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ADA469804
Advanced Metals and Ceramics for Armor and Anti-Armor Applications. High-Fidelity Design and Processing of Advanced Armor Ceramics
Personal Author(s): Niesz, D E , McCauley, J W
Report Date: Jun 2007
Descriptors: (U) *ARMOR, *REPRODUCIBILITY, *NANOTECHNOLOGY, SIMULATION, EXPERIMENTAL DATA, NONDESTRUCTIVE TESTING, COLLABORATIVE TECHNIQUES, SILICON CARBIDES, MODELS, MATERIALS, STATISTICAL ANALYSIS, DESIGN CRITERIA
Identifiers: (U) *ARMOR CERAMICS, *NANOCERAMICS, DEFECTS, DYNAMIC FAILURE, HIGH FIDELITY DESIGN, PROCESSING TECHNOLOGY, SHOCK-WAVE MANAGEMENT, MICROMECHANICAL MODELING, NUMERICAL MACROSTRUCTURES, ANTI-ARMOR APPLICATIONS
Abstract: (U) This is the final summary report of a 5-year (2001 2005) collaborative research program on advanced metals and ceramics for armor and anti-armor applications carried out in the U.S. Army Research Laboratory Material Center of Excellence at Rutgers and Johns Hopkins Universities under a cooperative-agreement contractual relationship. The focus of this center is on high-fidelity design and processing of advanced armor ceramics. The overarching goal has been to develop an improved understanding of selected key areas of the materials and processing science of ceramic armor materials. The areas investigated were selected jointly by the participating organizations with significant input from the ceramic armor community through a ceramic armor working group (CAWG) that included over 20 industrial organizations. They were selected as the most relevant, unclassified basic-research areas for improving the scientific understanding of the materials and processing science critical to the ballistic performance of ceramic armor materials. Length scales from the atomic to the macro were included in the investigation.
ADA464957
Software Development for Modeling High Power Solid State Slab Lasers
Personal Author(s): Bass, Michael
Report Date: Feb 2007
Descriptors: (U) *SOLID STATE LASERS, HIGH POWER, REFRACTIVE INDEX, GRAIN SIZE, TENSORS
Identifiers: (U) SLAB LASERS, CERAMIC CRYSTAL LASERS, CERAMIC CRYSTALS, CRYSTALLINE LASERS, DEPOLARIZATION LOSSES, DIELECTRIC IMPERMEABILITY, LASER CRYSTALS, PE61102F
Abstract: (U) We will extend this study to smaller grain sizes to determine if the trend observed continues or if the curve eventually turns down. During this period we identified an error in our earlier work on depolarization in crystalline lasers. This error, was caused by a problem in writing the reduced form of the 4th rank tensor that gives the piezo optic effect. It was essential to have found this error as we started evaluating depolarization losses in ceramic crystal lasers. These lasers are of general interest and are in use in the Textron Thin-Zag laser. We discuss the error, its correction and the evaluation of depolarization losses in ceramic crystals in this report. Since this report was first drafted we detected an error in our method of calculating the path of a ray through a random array of crystallities. This has been corrected and the results are being revised.
ADA458850
Mechanical, Mathematical, and Computer Modeling in Penetration Mechanics - IV (Hybrid Models for Nanostructured Ceramics - II)
Personal Author(s): Kartuzov, Valeriy V
Report Date: 30 Nov 2006
Descriptors: (U) *MECHANICS, *CERAMIC MATERIALS, *PENETRATION, *DEFORMABLE PROJECTILES, MATHEMATICAL MODELS, COMPUTERIZED SIMULATION, NANOTECHNOLOGY, UKRAINE, RHEOLOGY, PARAMETERS, HIGH VELOCITY, TARGETS
Identifiers: (U) *NON-DEFORMABLE PROJECTILES, ANALYTICAL MODELS, FOREIGN REPORTS
Abstract: (U) Penetration of non-deformable projectiles in continuum with various rheological properties has been of interest to researchers for a long time. The first modeling representations of penetration were formulated in XVIII-XIX centuries in Euler's, Poncelet's, Wuich's works, etc. Analysis of these results can be found in A.J. Sagomonjan's monographs. In conjunction with development of more exact and effective technical means in the last two decades, the interest in this problem has considerably increased, and this is proved by works of Voejkova and Sagomonjan (1985), Alojan (1985), Liapykhin et al. (1993), Bahrah et al. (1992), Forrestal et al. (1988), (1992), (2000), Dikshit and Sundararajan (1992), Piekutowski et al. (1999), Warren and Forrestal (1998), Warren (2000), Yossifon et al. (2001), Chen and Li (2002). The analysis of the modern state of the problem of analytical modeling of high-velocity penetration of non-deformable projectiles in targets can be found in works by Forrestal et al., Warren and Forrestal, Yarin et al., Yossifon, Chen and Li. From this analysis, it follows that at present there is a deficiency of relatively simple analytical models using natural, physical, and geometrical parameters of projectiles and targets and with a small number of fitting parameters. In this study, we have built and investigated a new model of penetration of non-deformable projectiles of various shapes in elastic-plastic and elastic-brittle materials.
ADA458362
MICROMECHANICS AND MICROSTRUCTURE EVOLUTION: Modeling, Simulation and Experiments. Held in Madrid, Spain on 12-16 September 2005
Report Date: 30 Oct 2006
Descriptors: (U) *MICROSTRUCTURE, *SYMPOSIA, *DISLOCATIONS, *DEFORMATION, SIMULATION, ELASTIC PROPERTIES, NUCLEATION, STEEL, IRON, MOLECULAR DYNAMICS, NANOTECHNOLOGY, RECRYSTALLIZATION, GRAIN GROWTH, SPAIN, FATIGUE(MECHANICS), CRYSTAL DEFECTS, CRACK PROPAGATION, FRACTURE(MECHANICS), ALLOYS, THIN FILMS, FINITE ELEMENT ANALYSIS, INTERFACES, METALS
Identifiers: (U) *PROCEEDINGS, FOREIGN REPORTS, MODELING AND SIMULATION, STRUCTURAL MATERIALS, *MICROMECHANICS, LENGTH SCALES, *MATERIAL PROPERTIES, NANOSCALE, MESOSCALE, DISLOCATION MOBILITY, DISLOCATION DISTRIBUTION, NANOINDENTATIONS, STRAIN GRADIENT PLASTICITY, FERROELECTRIC CERAMICS, FIBER REINFORCED COMPOSITES, STRESS DISTRIBUTION, GRAIN BOUNDARIES, PRECIPITATION KINETICS
Abstract: (U) The aim of this conference is to bring together scientists who are working on the modeling and simulation of the deformation behavior of materials, and on material microstructural evolution. The focus will be on the interplay between behaviors at different length scales, in particular the atomistic, nano/mesoscales, and continuum aspects necessary to describe the processes that lead to changes in microstructure. Of particular interest are investigations that discuss the bridging of length scales, and the prediction of material properties from theory and computation. Experimental validation of the approaches is also important to differentiate between competing theories. Novel experimental techniques, to guide or verify the modeling and simulation efforts, also pertain to the theme of the conference. The session topics are: Atomistic, Dislocation Dynamics, Microstructure Evolution, Continuum, and Experimental.
ADA456617
Collaborative Research Program on Advanced Metals and Ceramics for Armor and Anti-Armor Applications Dynamic Behavior of Non-Crystalline and Crystalline Metallic Systems
Personal Author(s): Ramesh, K T, McCauley, James W
Report Date: Sep 2006
Descriptors: (U) *ARMOR, *METALS, *INTERACTIONS, *CERAMIC MATERIALS, *ANTIARMOR AMMUNITION, WEAPONS, METAL MATRIX COMPOSITES, THRUST, TIGHTNESS, INTEGRATION, CRYSTALS, COHERENCE, MICROSTRUCTURE, DYNAMIC RESPONSE, ARMY RESEARCH
Identifiers: (U) *NANOSTRUCTURED METALS, CAMCS(CENTER FOR ADVANCED METALLIC AND CERAMIC SYSTEMS), BULK METALLIC GLASS, DYNAMIC PROPERTIES, *ADVANCED METALS, *CRYSTALLINE METALLIC SYSTEMS, *NON CRYSTALLINE METALLIC SYSTEMS
Abstract: (U) This collaborative research program emphasized collaborative research between Johns Hopkins University and the U.S. Army Research Laboratory (ARL) towards well-defined common goals: the understanding and development of advanced metallic systems for armor and anti-armor applications. The Johns Hopkins side of the collaboration was operated through a science driven, problem-directed Center the Center for Advanced Metal and Ceramic Systems. The Center provides a tight integration of the University with ARL, providing both an emphasis on fundamentals and a carefully planned coherent assistance with the ARL Weapons and Materials Research Directorate (WMRD) mission. The research thrusts and the collaborative structures of the Center provided a basis for the substantial enhancement and continuous improvement of the scientific and technical capabilities of ARL, particularly of WMRD. Each research thrust operated a Collaborative Research Group with joint responsibility for the development of the research. This report is the final report for research performed in the 2001 2005 period. The accomplishments of each research thrust are described in order. Rather than provide full detail in each case, the highlights are noted, and the corresponding publications are referenced for the details. Finally, a summary of the collaborative interactions and a summary of the publications and presentations are provided.
ADA457605
2006 Gordon Research Conference on Ceramics, Solid Studies In
Personal Author(s): Blendell, John E , Gray, Nancy R
Report Date: 18 Aug 2006
Descriptors: (U) *MICROSTRUCTURE, *CERAMIC MATERIALS, SYMPOSIA, INTERFACES, THIN FILMS, FUEL CELLS, GRAIN BOUNDARIES, GRAIN GROWTH, WETTING, GRAIN SIZE, POROSITY, BULK MATERIALS
Identifiers: (U) CRYSTALLOGRAPHIC TEXTURES, GRAIN TEXTURES, PHASE CONTENT, PHASE DISTRIBUTION, PORE LOCATION, PORE SIZE, SURFACE ADSORPTION
Abstract: (U) The Gordon Research Conference (GRC) on CERAMICS, SOLID STATE STUDIES IN was held at Proctor Academy from 8/13/2006 thru 8/18/2006. The Conference was well-attended with 101 participants (attendees list attached). The attendees represented the spectrum of endeavor in this field coming from academia, industry, and government laboratories, both U.S. and foreign scientists, senior researchers, young investigators, and students. In designing the formal speakers program, emphasis was placed on current unpublished research and discussion of the future target areas in this field. There was a conscious effort to stimulate lively discussion about the key issues in the field today. Time for formal presentations was limited in the interest of group discussions. In order that more scientists could communicate their most recent results, poster presentation time was scheduled. Attached is a copy of the formal schedule and speaker program and the poster program. In addition to these formal interactions, "free time" was scheduled to allow informal discussions. Such discussions are fostering new collaborations and joint efforts in the field.
ADA469470
Nano Crystalline Ceramic and Ceramic Coatings Made by Conventional and Solution Plasma Spray
Personal Author(s): Jordan, Eric H, Gell, Maurice
Report Date: 01 Aug 2006
Descriptors: (U) *CERAMIC COATINGS, *CERAMIC MATERIALS, *NANOSTRUCTURES, MECHANICAL PROPERTIES, MICROSTRUCTURE, BARRIER COATINGS, PLASMA SPRAYING, SYMPOSIA, PHYSICAL PROPERTIES
Identifiers: (U) AIR PLASMA SPRAY, NATO FURNISHED, ALUMINA-TITANIA WARE COATINGS, SPPS(SOLUTION PRECURSOR PLASMA SPRAY), EB-PVD(ELECTRON BEAM PHYSICAL VAPOR DEPOSITION), DENSE CERAMICS
Abstract: (U) Nanostructured ceramic coatings produced by plasma spray processes are being developed for a wide variety of applications that require resistance to wear, erosion, cracking and spallation. In addition the process is being developed to make near net shaped ceramic performs by dissolution of the substrate after spraying. Attractive properties associated with a nanostructure (in general referring to grain size smaller than 100 nm) have been documented for bulk materials. It is anticipated that, if properly deposited, nanostructured ceramic coatings could also provide improved properties for variety of applications, including wear resistant and thermal barrier coatings. Thermal spray techniques are often used to deposit thick oxide coatings and experimental examination of phase constituents, microstructures and mechanical properties with respect to processing conditions have been extensively carried out and reviewed. This is one of the first papers that deals with similar studies for nanostructured coatings. In this paper three different applications are discussed. Conventional air plasma spray of nano crystalline alumina-titania ware coatings for ship applications and then liquid precursor spray of nano crystalline thermal barrier coatings for turbine applications finally a brief mention of recent progress in spraying dense materials for use a stand alone ceramics will be presented.
ADA455765
Chemical Routes to Ceramics With Tunable Properties and Structures
Personal Author(s): Sneddon, Larry G
Report Date: 26 Jul 2006
Descriptors: (U) *PRECURSORS, *HIGH TEMPERATURE, *CERAMIC FIBERS, HAFNIUM, CARBIDES, BORIDES, DIATOMS, ELECTROSTATICS, NITRIDES, ZIRCONIUM, BORON CARBIDES
Identifiers: (U) HAFNIUM BORIDE, HAFNIUM CARBIDE, HAFNIUM NITRIDE, DIATOM-TEMPLATING, *MICROFIBERS, *NANOFIBERS, *CHEMICAL PRECURSORS, *ADVANCED CERAMICS
Abstract: (U) The objective this AFOSR sponsored project was to design, synthesize and explore the materials applications of new, processable single-source chemical precursors to nonoxide ceramics that allow the formation of these technologically important materials in forms that have been unattainable with conventional methods. Research was focused on the development of new precursor routes to a number of ultra high temperature ceramics, including hafnium and zirconium -boride, -carbide and -nitride materials, and on the use of electrostatic spinning and diatom-templating methods, in conjunction with newly designed preceramic polymers, to achieve the formation of nano-structured ceramic materials.
ADA469054
Lightweight and Advanced Materials for Defense: Materials for Military Ground Vehicles
Personal Author(s): Ostberg, Donald T
Report Date: 27 Jun 2006
Descriptors: (U) *TACTICAL WARFARE, *TANKS(COMBAT VEHICLES), ARMOR, COMPOSITE MATERIALS, STEEL, CERAMIC MATERIALS, ALUMINUM, TITANIUM
Identifiers: (U) *FCS(FUTURE COMBAT SYSTEMS), BRIEFING CHARTS
Abstract: (U) MATERIALS FOR TACTICAL TRUCKS: (1) Material must be readily available and fully developed. (RHA; High hard steel; Aluminum). (2) Research projects are ongoing to further develop advanced lightweight armors. (Composites; Ceramics; Titanium) (3) Long Term Armor Strategy (A+B design; Requirements are classified)
ADA451746
Design of Geopolymeric Materials Based on Nanostructural Characterization and Modeling
Personal Author(s): Lukey, G C, van Deventer, J S, Provis, J L , Duxson, P
Report Date: Apr 2006
Descriptors: (U) *MATHEMATICAL MODELS, *POLYMERS, *ALUMINOSILICATES, CATIONS, CRYSTALLIZATION, AUSTRALIA, STOICHIOMETRY, CERAMIC MATERIALS, COMPOSITE MATERIALS, REACTION KINETICS
Identifiers: (U) FOREIGN REPORTS, GEOPOLYMERS, STATISTICAL THERMODYNAMIC MODELS
Abstract: (U) Geopolymers, a class of largely X-ray amorphous aluminosilicate binder materials, have been studied extensively over the past several decades, but largely from an empirical standpoint. The primary aim of this investigation has been to apply a more science-based approach to the study of geopolymers, including introducing a variety of mathematical modelling techniques to the field. Si/Al ordering within the tetrahedral aluminosilicate gel framework is described by a statistical thermodynamic model, which provides an accurate representation of the distribution of Si and Al sites within the framework as well as physically reasonable values for the energy penalty for ordering violation. Direct measurement of the kinetics of the early stages of geopolymeric setting (up to 3 hours) is shown to be possible by energy-dispersive X-ray diffractometry (EDXRD), utilizing a high-intensity synchrotron X-ray source to conduct experiments in transmission geometry. Quantification of the results obtained by this technique provides a comparison between the setting rates of different geopolymer-forming systems, and shows clear trends with regard to temperature and Si/Al ratio as well as the nature of the alkali cation (or cation mixture) present. Finally, formulation of a reaction kinetic model for geopolymerisation draws together the results of the project. Based on an existing model for aluminosilicate weathering in aggressive media, the model includes description of dissolution, reorientation and reprecipitation processes including an autocatalytic polycondensation step, and can describe reactions involving either fly ash or metakaolin. Flexible stoichiometry of all polymerized species allows for variations in Si/Al ratios, and the effects of different alkali cations are also described. Model results are compared to calorimetric and EDXRD data, and predictions are consistent with the processes that have previously been postulated to occur during the early stages of geopolymerisation.
ADA458217
In Situ Studies of Defect Nucleation During the PVT and CVD Growth of Silicon Carbide Single Crystals
Personal Author(s): Dudley, Michael
Report Date: Mar 2006
Descriptors: (U) *SINGLE CRYSTALS, *NUCLEATION, *SILICON CARBIDES, *CRYSTAL DEFECTS, CORROSION, IN SITU ANALYSIS, TOPOGRAPHY, CHEMICAL VAPOR DEPOSITION, EPITAXIAL GROWTH
Identifiers: (U) *CVD(CHEMICAL VAPOR DEPOSITION)
Abstract: (U) A complete chemical vapor deposition (CVD) system for growing SiC epitaxial films and bulk crystals was set up using commercially procured gas flow controls and scrubber units, and integrating them with a modified in-house designed growth chamber that has options for in situ X-ray topographic study. This CVD system uses silicon tetrachloride (SiCl4), silane (SiH4), propane (C3H8), hydrogen (H2) and argon (Ar) gases. The aggressive SiCl4 corrosion in the chamber and the gas lines has been investigated and found to be predominantly related to moisture, and this severe problem has been solved by keeping the gas lines and the growth reactor in vacuum or in inert atmosphere when the CVD system is not running.
ADA454566
Ab-Initio Calculations of Structure and Properties of Nanolaminated MAX Phases
Personal Author(s): Schneider, Jochen M
Report Date: 27 Jan 2006
Descriptors: (U) *TRANSITION METALS, *CERAMIC MATERIALS, *TRIBOLOGY, ELECTRONICS, AIRCRAFT MAINTENANCE, SHEAR MODULUS, ELECTRONS, CONFIGURATIONS, FRICTION, NANOTECHNOLOGY, MACHINABILITY, HARDNESS, BONDING, OXIDATION, CHEMISTRY, TOUGHNESS, SYNTHESIS, STABILITY
Identifiers: (U) *AIRCRAFT STRUCTURES, *NANOLAMINATED MAX PHASES, CALCULATIONS, FOREIGN REPORTS
Abstract: (U) This report results from a contract tasking RWTH Aachen as follows: A new class of machinable ceramic materials had recently received attention due a unique combination of hardness, toughness, machinability, and oxidation stability. These materials are called MAX phases, where M designates a transition metal, A is mostly a IIIA or IVA element of periodic table, and X stands for C or/and N. MAX phases have a unique nanolaminated atom arrangement, which leads to a low shear modulus - a property critical for low friction materials. However, MAX phases for tribology have not yet been explored systematically. Most research has been done on the machinable Ti3SiC2 system. However, the list of theoretically possible MAX phases is extensive. Practically, it is resource intensive to synthesize every thinkable MAX phase searching for a material exhibiting advantageous tribological properties. A superior strategy is to calculate bonding, structure, and properties of possible MAX phase compounds and then selectively dedicate a synthesis effort to the phase with the best combination of properties. This project is based on state of the art (1998 Nobel Prize in chemistry) density functional theory calculation algorithms to build up models of MAX phases and provide predictions of their phase stability and expected properties. It is envisioned to systematically explore nanolaminated phases with the M2AlC formula to address the influence of the M elements (Y, Zr, Nb, Mo, La, Hf, Ta, W) on bonding strength, electronic structure, and shear modulus. Our aim is to contribute towards the development of novel tribological materials. We propose to study the relationship between the valence electron configuration of M = Y, Zr, Nb, Mo, La, Hf, Ta, and W in M2AlC and the shear modulus of this fascinating new class of nanolaminated materials.
ADA450056
Scientific Presentations on Superconductivity from 2002-2005
Personal Author(s): Barnes, Paul N, Harrison, Brandon C
Report Date: Jan 2006
Descriptors: (U) *HIGH TEMPERATURE SUPERCONDUCTORS, LABORATORY TESTS, THIN FILMS, NANOTECHNOLOGY, ELECTRON FLUX, ALTERNATING CURRENT
Identifiers: (U) *HTS(HIGH TEMPERATURE SUPERCONDUCTING) COATED CONDUCTOR, *YBCO(YTTRIUM-BARIUM-COPPER-OXYGEN) SUPERCONDUCTOR, NANOPARTICULATE DISPERSIONS, RARE EARTH SUBSTITUTIONS, HIGH TEMPERATURE CERAMIC SUPERCONDUCTORS, AC LOSS, FLUX PINNING, HIGH CRITICAL CURRENT, NANOPARTICLES, X-RAY PHOTOELECTRON SPECTROSCOPY, PE62203F, WUAFRL314532ZE
Abstract: (U) This program addresses the basic scientific and engineering issues related to the development of the second generation high temperature superconducting (HTS) coated conductor for use in magnet and generator coil windings of power applications relevant to the Air Force (AF). Current work focuses on the development of an ac YBCO coated conductor and enhancement of the current dc coated conductor. The dc coated conductor development is done as part of an overall AF program that includes industry and academic research facilities. This program is coordinated with the Department of Energy's Coated Conductor Program to ensure integration with no redundancy. Flux pinning in the conductor is a significant focus of the overall coated conductor work to improve in-field critical currents. The ac loss issues as well as stability (and quench protection) must be ultimately considered for study and work has commenced in this area within the in-house program. In order for the conductor to be ready for projected power generation requirements (for directed energy weapons), the superconductivity group is determining the unique, AF requirements of the conductor and investigating ac loss and flux pinning issues.
ADA464844
1.8 kV, 10 mOmega-square cm 4H-SiC JFETs (Preprint)
Personal Author(s): Scofield, James, Ryu, Sei-Hyung, Krishnaswami, Sumi, Fatima, Husna, Agarwal, Anant K
Report Date: Jan 2006
Descriptors: (U) *FIELD EFFECT TRANSISTORS, *SILICON CARBIDES, HIGH TEMPERATURE, FABRICATION, NANOTECHNOLOGY, MICROELECTRONICS, SUBSTRATES
Identifiers: (U) JFET(JUNCTION FIELD EFFECT TRANSISTOR)
Abstract: (U) Fabrication and characteristics of high voltage, normally-on junction field effect transistors (JFETs) in 4H-silicon carbide (4H-SiC) are presented. The devices were built on 5x10(exp 15) cm(exp -3) doped, 12 micron thick n-type epilayer grown on a n+ 4H-SiC substrate. A specific on-resistance of 10 mOmega-square cm and a blocking voltage of 1.8 kV were measured. Device characteristics were measured for temperatures up to 300 deg C. An increase of specific on-resistance by a factor of 5 and a decrease in transconductance were observed at 300 deg C, when compared to the value at room temperature. This is due to a decrease in bulk electron mobility at elevated temperature. A slight negative shift in pinch-off voltage was also observed at 300 deg C. The devices demonstrated robust DC characteristics for temperatures up to 300 deg C, and stable high temperature inverter operation in a power DC-DC converter application, using these devices, is reported in this paper.
ADA450946
Synthesis and Mirostructural Design of Oxide Fibers
Personal Author(s): Yoon, Wonki, Kriven, Waltraud M
Report Date: 31 Dec 2005
Descriptors: (U) *FIBER REINFORCED COMPOSITES, *CERAMIC FIBERS, SYNTHESIS, REFRACTORY MATERIALS, FINE GRAINED MATERIALS, SINGLE CRYSTALS, HEAT TREATMENT
Abstract: (U) Fine ceramic oxide fibers are widely used as reinforcements in composites for high temperature applications. The primary goal of this research effort was to investigate the growth of single crystal or textured or eutectic oxide fibers by heat treatment of polycrystalline or amorphous precursor fibers.
ADA459310
MRS Workshop Explores the Diversity of 3D Multifunctional Ceramic Composites
Personal Author(s): Braun, Paul V
Report Date: Dec 2005
Descriptors: (U) *THREE DIMENSIONAL, *CERAMIC MATERIALS, *WORKSHOPS, REPRINTS, MICROSTRUCTURE, POLYMERS, PHOTONIC CRYSTALS, NANOSTRUCTURES, HOLOGRAPHY, COMPOSITE MATERIALS, FABRICATION, SEMICONDUCTORS
Identifiers: (U) NANOPARTICLE ASSEMBLIES, SELF ASSEMBLY, ACTIVE MEMBRANES, BIOLOGICAL DETECTORS, CHEMICAL DETECTORS
Abstract: (U) The MRS Workshop on Three-Dimensional Multifunctional Ceramic Composites was held at the Beckman Institute on the campus of the University of Illinois at Urbana-Champaign (UIUC) October 3-5, 2005. Organized by Paul V. Braun of UIUC, C. Jeffrey Brinker of the University of New Mexico and Sandia National Laboratories, and Shanhui Fan of Stanford University, the workshop reached an audience of about 100 attendees from academic institutions, government laboratories, and private industry. The scientific and technical underpinnings of self-assembly and properties of self-assembled 3D ceramic, composite and semiconductor structures were emphasized. The technical program consisted of invited presentations from renowned experts, along with selected contributed presentations, posters, and hands-on tutorials given by expert faculty. The topics explored included new developments in 3D photonic crystals, chemical and biological sensors, nanoparticle assemblies, rapid fabrication techniques, active membranes, 3D holographic patterning, and modeling and theory of 3D optical devices.
ADA441334
Development of Metal/Ceramic Nanocomposite Powder and Consolidation to Bulk Nanocomposite Components with Retained Nanostructures
Personal Author(s): Seal, Sudipta, Georgieva, Petya, Rea, Keith, Viswanathan, Venkatachalapathy
Report Date: 17 Nov 2005
Descriptors: (U) *COMPOSITE MATERIALS, *CERAMIC MATERIALS, *NANOSTRUCTURES, QUICK REACTION, HIGH TEMPERATURE, PLASMAS(PHYSICS), COPPER, PLASMA SPRAYING, POWDER METALS, NANOTECHNOLOGY, PROTECTIVE COVERINGS, SPRAYS, GUNS, OXIDATION, SOLIDIFICATION, POROSITY, BULK MATERIALS
Identifiers: (U) *BULK NANOCOMPOSITE COMPONENTS, YOUNG INVESTIGATOR PROGRAM, SHROUDED AIR PLASMA SPRAY, MOLTEN PARTICLES, NANOSTRUCTURED COMPONENTS, PLASMA GUNS, PE68342N
Abstract: (U) An instrument innovation has been developed that enables for the minimization of oxidation during Air Plasma Spray (APS). Oxidation is limited due to the creation of a three-part copper shroud that utilizes a custom-fit mounting plate that is affixed to the SG-100 APS plasma gun. Due to the separation of the ambient environment from the plasma flame and the particles traveling through it, this process has been deemed Shrouded Air Plasma Spray or SAPS. Shrouding the plasma flame and the molten particles holds much promise for the minimization of porosity, oxidation, and other debilitating material phenomenon that occurs at the high temperatures and rapid solidification environment that is used for the development of bulk nanostructured components. This shroud design has been experimentally tested and meets all APS spraying parameters.
ADA441212
Mechanisms of Photo Degradation for Layered Silicate-Polycarbonate Nanocomposites
Personal Author(s): Sloan, James M, Patterson, Philip
Report Date: Sep 2005
Descriptors: (U) *LAYERS, *POLYMERS, *POLYCARBONATES, *CERAMIC MATRIX COMPOSITES, *WEATHERING, *PHOTODEGRADATION, *SILICATES, ARMOR, INFRARED SPECTROSCOPY, AUGMENTATION, NANOTECHNOLOGY, HYBRIDIZATION, VISIBLE SPECTRA, ACCELERATED TESTING, CLAY, ULTRAVIOLET RADIATION, SURVIVABILITY, EXPOSURE(GENERAL), PHOTOCHEMICAL REACTIONS
Identifiers: (U) HYBRID MATERIALS, POLYMER MATRIX NANOCOMPOSITES, ABRASION RESISTANCE, OPTICAL CLARITY, CHEMICAL RESISTANCE, LAYERED SILICATES, YELLOWING, ENHANCED MATERIALS, PHOTOLYTIC DEGRADATION, PLS(POLYMER LAYERED SILICATES), *POLYMER LAYERED SILICATES, POLYMER CERAMIC HYBRIDS, TRANSPARENT ARMOR
Abstract: (U) The use of advanced lightweight materials to improve combat survivability has been of crucial interest to the U.S. Army for a number of years. Specifically, hybrid organic/inorganic polymer matrix nanocomposites show promise in providing many of the physical properties required (i.e., lightweight structure, rugged abrasion resistance, and high ballistic impact strength). However, as with any polymer system, these materials are susceptible to degradation over time when exposed to various environmental (i.e., sunlight, moisture, temperature, etc.) conditions. This structural degradation will eventually compromise the original integrity of the materials' desired properties. Polycarbonate (PC) has outstanding ballistic impact strength, good optical clarity, and high heat-distortion resistance. The Army has a continuous interest in research on PC for better chemical resistance and enhanced resistance to abrasion. The focus of this research is to exploit nanotechnology through incorporation of layered silicates for property enhancement. Typical mica-like clays consist of stacked platelets with the thickness of each individual platelet on the order of 1 nm. In this study, the effect of accelerated weathering upon newly developed PC-layered silicate nanocomposite materials was investigated. The silicate loading varied from 0 to 3.5% by weight. A fluorescent ultraviolet (UV)/condensation weatherometer was selected for the exposure study. The materials were characterized by UV/VIS spectroscopy and Fourier transform infrared spectroscopy. The results reveal that the carbonate linkages undergo a scission reaction upon UV exposure, thereby compromising the original properties of the material. Furthermore, these scissions produce a yellowing of the polymer matrix that can inhibit its use where optical clarity in important.
ADA458382
CVC Silicon Carbide Optical Properties and Systems (Preprint)
Personal Author(s): Foss, Jr, Colby A
Report Date: 29 Jul 2005
Descriptors: (U) *OPTICAL PROPERTIES, *CHEMICAL VAPOR DEPOSITION, *SILICON CARBIDES, MACHINING, ULTRAVIOLET SPECTRA, NEAR NET SHAPE FORMING, RESIDUAL STRESS, COMPOSITE MATERIALS, SINGLE CRYSTALS
Identifiers: (U) CVC(CHEMICAL VAPOR COMPOSITES), PE65502F, AFRLWU3005DPDN
Abstract: (U) The chemical vapor composites (CVC) process provides for the rapid manufacture of near net shape, reduced residual stress silicon carbide (SIC) suitable for high performance optics. The reduction or elimination of residual stress provides several key advantages: 1) increased growth rate, 2) high yields and 3) near net shape deposition of complex geometries. Near net shape deposition allows for fabrication of spherical and aspherical optics without machining of the optical surface. Final surface figures of optical flats are typically better than l/lO delta (P-V) and a 2-5A surface roughness. A comparison of ultraviolet spectrum reflectance of CVC SiC and that of single crystal SiC is discussed, The complex optical constants of CVC SiC in the mid-infrared spectrum are also presented.
ADA437199
Nanograin Ceramic Optical Composite Window
Report Date: 15 Jul 2005
Descriptors: (U) *CERAMIC MATRIX COMPOSITES, *ALUMINUM OXIDES, *INFRARED WINDOWS, *ZIRCONIUM OXIDES, *NANOTECHNOLOGY, DENSITY, ISOSTATIC PRESSING, TABLES(DATA), SINTERING, GRAIN GROWTH, PARTICULATES, FORGING, GRAIN SIZE, MEASUREMENT
Identifiers: (U) SBIR(SMALL BUSINESS INNOVATION RESEARCH), SBIR REPORTS, SBIR TOPIC N04-T008 PHASE 1, STTR(SMALL BUSINESS TECHNOLOGY TRANSFER), DENSIFICATION, OXYGENATION, HIP(HOT ISOSTATIC PROCESSING)
Abstract: (U) The principle objective of the Phase I STTR program was to demonstrate the feasibility of producing a dense, transparent nanocomposite material with final grain sizes less than 50 nm. The alumina/zirconia system was initially selected because it has been shown for larger scale systems that immiscible phases are particularly effective in suppressing grain growth. The work was conducted by MetaMateria Partners (MMP) in collaboration with the Particulate Materials Center (PMC) at Penn State University. Key accomplishments done in Phase I were: * Dense Al2O3-ZrO2 composites with a microstructure under 50 nm were made on a repeatable basis by densifying Al2O3-ZrO2 nanoparticulates with pressure-assisted sintering (sinter forging). Primary starting particle size was 3-5 nm (surface area 200-500 m squared/g). * Al2O3-ZrO2 nanoparticulate powders were prepared by two different methods: sonochemical processing at MMP and glycothermal processing at PMC. The sonochemical process gave finer particle sizes. * Full densification was accomplished using sinter-forging followed by hot isostatic pressing (HIP) at 12500 degrees C for 2 hours and 20,000 psi. * Limited IR transmission measurements yielded in one sample ^50% transmission.
ADA445456
A Novel, Flexible Approach to Packaging Integrated Microsystems for Space Applications
Personal Author(s): Eckersley, Steven, Coumar, Oudea, Schalk, Josef, Kluge, Martin
Report Date: 13 Jul 2005
Descriptors: (U) *SPACE TECHNOLOGY, *SPACECRAFT, *PACKAGING, *MICROELECTROMECHANICAL SYSTEMS, *OFF THE SHELF EQUIPMENT, *MICROSENSORS, LOW POWER, LOW COSTS, CERAMIC MATERIALS, MICROPROBES, NANOTECHNOLOGY, UNITED KINGDOM, DATA PROCESSING EQUIPMENT, LIGHTWEIGHT, POWER SUPPLIES, ROBOTS, LAYERS, SYMPOSIA, INTEGRATED SYSTEMS
Identifiers: (U) MST(MICROSYSTEMS TECHNOLOGY), NANOSATELLITES, AEROBOTS, COMPONENT REPORTS, FOREIGN REPORTS
Abstract: (U) The European Aeronautic Defence and Space Company (EADS) recognizes the potential for Microsystems Technology (MST) to disrupt and revolutionize the space industry, where it can dramatically reduce mass, size, and power requirements, and, therefore, mission cost. EADS is developing a novel modular approach to packaging integrated microsystems for space applications, called "micropacks." The micropack include suites of commercial off-the-shelf (COTS) MST sensors, packaged and integrated into a 3D modular multi-layer ceramic package. This impressively light and compact micropack technology can be adapted to form the basis of a solution for a range of exciting future mission concepts, such as the following: (1) highly integrated multi-functional nanosatellites (e.g. for solar terrestrial physics or space weather monitoring); (2) planetary aerobots on Mars, Venus, the Giant Planets, and Titan (e.g. as a payload/system package); (3) sub-100g planetary microprobes for measuring atmospheric profiles; (4) solar sails (e.g. as the central hub of the spacecraft); (5) penetrators (e.g. as a payload/system package); and (6) robotic planetary explorers (e.g. landers, rovers, walkers, hoppers). The micropack consists of five ceramic layers, including an atmospheric sensor unit (e.g. pressure sensor), an acceleration sensor unit, a power supply unit, a data handling unit (a Texas Instruments MSP430 micro-controller), and a chip-size radiofrequency transceiver unit laminated into the ceramic. Each module has a standardized interface, which ultimately combines with other modules to form a system platform. The size of the micropack will be a mere 20x25x25mm(exp 3), with power consumption of less than 100mW and a mass of just 25g.
ADA434229
Detection of Residual Stress in SiC MEMS Using micro-Raman Spectroscopy
Personal Author(s): Zingarelli, John C
Report Date: Mar 2005
Descriptors: (U) *DETECTION, *RAMAN SPECTROSCOPY, *RESIDUAL STRESS, *SILICON CARBIDES, *MICROELECTROMECHANICAL SYSTEMS, CRYSTAL STRUCTURE, EXCITATION, SIGNAL TO NOISE RATIO, THIN FILMS, THESES, CHEMICAL VAPOR DEPOSITION, SUBSTRATES, ABSORPTION, RAMAN SPECTRA
Identifiers: (U) STOKES PEAKS
Abstract: (U) Micro-Raman (mu-Raman) spectroscopy is used to measure residual stress in two silicon carbide (SiC) poly-types: single-crystal, hexagonally symmetric 6H-SiC, and polycrystalline, cubic 3C-SiC thin films deposited on Si substrates. Both are used in micro-electrical-mechanical systems (MEMS) devices. By employing an incorporated piezoelectric stage with submicron positioning capabilities along with the Raman spectral acquisition, spatial scans are performed to reveal areas in the 6H-SiC MEMS structures that contain residual stress. Shifts in the transverse optical (TO) Stokes peaks of up to 2 cm^-1 are correlated to the material strain induced by the MEMS fabrication process through the development of phonon deformation potential curves for this material. The 3C-SiC films, with thicknesses ranging from 1.5-5 microns, are deposited by CVD on (100) Si substrates and are also investigated to determine their residual stress. An ultraviolet excitation source (lambda = 325 nm, hv = 3.82 eV) was determined to be more effective for the detection of Raman shifts in these thin films than the 514-nm source, since the absorption coefficient in SiC at 300 K at 325 nm is 3660 cm-1, while that at 514 nm is less than 100 cm-1.
ADA437126
AMN-2: Second International Conference on Advanced Materials and Nanotechnology
Report Date: 11 Feb 2005
Descriptors: (U) *NANOTECHNOLOGY, METALS, OPTICS, SYMPOSIA, PHYSICAL PROPERTIES, POLYMERS, COMPOSITE MATERIALS, SUPERCONDUCTORS, CARBON NANOTUBES, COLLABORATIVE TECHNIQUES, OPTICAL MATERIALS, SEMICONDUCTORS, ALLOYS, CERAMIC MATERIALS, LITHOGRAPHY, CLUSTERING, BIOMOLECULES
Identifiers: (U) AQ F05-08-3397, NANOLITOGRAPHY, NONOSCALE OPTICS, NONOTUBES, NANOENGINEERING, FOREIGN REPORTS
Abstract: (U) The purpose of the conference is to promote international collaborations in the broad areas of advanced materials and nanotechnology, with a particular emphasis on new and emerging technologies. Technical symposia will include biomolecular assembly, conducting polymers, functional materials, nanoengineered materials and devices, nanolithography, nanoscale optics, nanotube growth and device concepts, novel semiconductor materials, physics of clusters and cluster-based devices, and properties of superconducting materials.
ADA430400
Mechanical and Thermal Properties of Advanced Ceramics for Gun Barrel Applications
Personal Author(s): Swab, Jeffrey J, Wereszczak, Andrew A, Tice, Jason, Caspe, Russ, Kraft, Reuben H
Report Date: Feb 2005
Descriptors: (U) *THERMAL PROPERTIES, *MECHANICAL PROPERTIES, *GUN BARRELS, *CERAMIC MATERIALS, TOUGHNESS, STRENGTH(MECHANICS), FRACTURE(MECHANICS), LININGS, THERMAL EXPANSION, THERMAL CONDUCTIVITY, HARDNESS, SPECIFIC HEAT
Identifiers: (U) GUN TUBES
Abstract: (U) Eight commercially available ceramic materials were procured and evaluated for potential application as gun barrel liners. These materials included an alumina, zirconia, and SiAlON, as well as three silicon carbides and two silicon nitrides. Preliminary evaluation determined the strengths, fracture toughness, Vickers hardness, thermal conductivity, specific heat, and linear coefficient of thermal expansion. An uncensored Weibull analysis was performed on all of the strength data. These databases were developed for use in the probabilistic modeling and design efforts of the program to predict performance, identify optimum gun barrel designs, and to rank and down select ceramics for further evaluation.
ADA430030
Bio-Derived Photonic Assemblies
Personal Author(s): Thomas, Edwin L, Morris, Cohen, Mickiewicz, Rafal
Report Date: 31 Jan 2005
Descriptors: (U) *SEA URCHINS, *PHOTONIC CRYSTALS, ORDER DISORDER TRANSFORMATIONS, THREE DIMENSIONAL, CROSSLINKING(CHEMISTRY), VIRUSES, SILICON CARBIDES, TELLURIUM, INTERMEDIATE INFRARED RADIATION, CHEMICAL RADICALS
Identifiers: (U) WIV(WISEANA IRIDESCENT VIRUS)
Abstract: (U) Biologically derived photonic assemblies were created using two different approaches. The first method employed the periodic, bi-continuous exoskeleton structure of a sea urchin as a template for the construction of a 3-dimensional (3-D) photonic crystal. The second approach involved viral particles of the Wiseana iridescent virus (W!V), assembled by various means to produce colloidal photonic crystals. In the first case, a novel cyclic size reduction scheme was devised to shrink the native sea urchin skeleton structure to the relevant size scale. This method produced high fidelity replicas of the original structure with a 50% decrease in linear dimensions at each iteration. The silicon oxycarbide (SiOC): air replica was subsequently infiltrated with tellurium (Te) and etched to increase the dielectric contrast, resulting in a Te: air structure exhibiting a sharp, well defined reflectivity peak in the mid-IR range. In the second case, sedimentation, centrifugation, and flow-assisted assembly were successfully used to guide virus particles into ordered colloidal crystals with photonic properties in the visible range. The centrifugation and flow-assisted techniques created larger area crystals with better defined spectral properties than the sedimentation technique. Significantly, the spectral properties (color) of both disordered and polycrystalline assemblies could be tuned by swelling the cross-linked colloidal crystals with water and varying processing parameters.
ADA449542
Spring 2005 Industry Study. Strategic Materials
Personal Author(s): Boland, Michael, Bromell, Robert, Carpenter, Robert , Clark, Thomas , Donnelly, Thomas , Echernacht, Jr , Kenneth, Higgins, David, Madden, Michael, Martin, Matthew, Murdock, Hal
Report Date: Jan 2005
Descriptors: (U) *NATIONAL SECURITY, *MATERIALS, COMPETITION, STEEL, AVAILABILITY, TITANIUM, MILITARY MODERNIZATION, STOCKPILES, NANOTECHNOLOGY, MICROELECTROMECHANICAL SYSTEMS, ECONOMIC DEVELOPMENT, SUPERALLOYS, RARE EARTH ELEMENTS, POWDER METALLURGY, ALUMINUM, CERAMIC MATERIALS, COMPOSITE MATERIALS, ECONOMIC IMPACT
Identifiers: (U) COMMERCIALIZATION, INNOVATION, BIOMIMETICS, ACCESSIBILITY, AFFORDABILITY, CRITICAL MATERIALS, INNOVATION
Abstract: (U) Strategic materials are those materials and related technologies whose critical function or availability is essential for US economic competitiveness and security. Emerging materials and innovative technologies are key enablers to military transformation and economic growth. In order to retain its competitive advantage, the US must initiate a comprehensive National Materials Strategy to focus and revitalize the climate for innovation, to develop strategic partnerships for rapid commercialization, and to ensure the accessibility, availability, and affordability of critical materials. In summary, the US should again view materials as strategic given their role as a critical enabler for economic prosperity and security.
ADA460490
Plastic/Brittle Behavior of Consolidated Bodies: Role of Particle Pair Potential
Personal Author(s): Lange, F F
Report Date: Jan 2005
Descriptors: (U) *POWDERS, *CERAMIC MATERIALS, *BRITTLENESS, MECHANICAL PROPERTIES, PROCESSING, RELIABILITY, HETEROGENEITY, COLLOIDS, COMPACTING, PLASTIC PROPERTIES, PARTICLES, DEFECTS(MATERIALS), CRYSTALS, STRENGTH(MECHANICS), SATURATION
Identifiers: (U) *COLLOIDAL POWDER PROCESSING, *FORMING METHODS, *SHAPE FORMING, FILTERING, FLAWS, INTERPARTICLE FORCES, SATURATED POWDER COMPACTS
Abstract: (U) Colloidal powder processing can improve the reliability and strength of ceramics by reducing the size of strength degrading heterogeneities through filtering the powder prior to consolidation. Removing heterogeneities greater than a given size is equivalent to a proof test, namely, truncating the strength distribution. Although significant property improvements can be made with the colloidal approach, new forming methods-consistent with the removal of flaws, are still under development. This development requires knowledge relating the mechanical properties of saturated powder compacts to the forces between particles, similar to relating properties of crystalline materials to interatomic forces. The background to this program resides with the discovery that short-range repulsive potentials can be developed that, when combined with the pervasive attractive van der Waals potential, produce an interparticle pair potential characterized by a potential well. This development has lead to new shape forming methods that are discussed at the end of this review.
ADA430219
Carbothermal Reduction Synthesis and Structural Evolution of Nanocrystalline Ultra High Temperature Carbides
Personal Author(s): Sacks, Michael D
Report Date: Dec 2004
Descriptors: (U) *HAFNIUM COMPOUNDS, *CARBIDES, *SILICON CARBIDES, *POLYCRYSTALLINE, LOW TEMPERATURE, ZIRCONIUM COMPOUNDS, CORES, STRUCTURAL PROPERTIES, VAPORS, SYNTHESIS(CHEMISTRY), CARBON, MIXTURES, OXIDES, REACTANTS(CHEMISTRY), MONOXIDES
Identifiers: (U) *CARBOTHERMAL, NANOCRYSTALLINE, *ZIRCONIUM CARBIDES, *HAFNIUM CARBIDES
Abstract: (U) Zirconium carbide (ZrC) and hafnium carbide (HfC) powders were produced by the carbothermal reduction reaction of carbon and the corresponding metal oxide (ZrO2 and HfO2, respectively). Solution-based processing was used to achieve a fine-scale (i.e., nanometer-level) mixing of the reactants. The reactions were substantially completed at relatively low temperatures (<1500 C) and the resulting products had small average crystallite sizes (^5O-l3O nm). Dry-pressed compacts prepared using ZrC-based powders with ^100 nm crystallite size could be pressurelessly sintered to ^99% relative density and zero open porosity at l950C. Silicon carbide (SiC) powders with crystallite size <25 nm were prepared at low temperature (^l3OOC) by carbothermal reduction reactions in silica/carbon mixtures. Solution-based processing was again used to achieve fine-scale mixing of the reactants. Mechanistic studies indicated that the SiC formed in accordance with the "shrinking core" reaction model in which the rate was controlled by the reaction of silicon monoxide vapor at carbon surfaces.
ADA429746
Efficient Local Packing in Metallic Glasses
Personal Author(s): Miracle, D B
Report Date: Aug 2004
Descriptors: (U) *METAL MATRIX COMPOSITES, REPRINTS, CRYSTAL STRUCTURE, STRUCTURAL PROPERTIES, AMORPHOUS MATERIALS, CERAMIC MATERIALS, HIGH DENSITY, SOLVENTS, RADIUS(MEASURE)
Identifiers: (U) METALLIC GLASS, WUAFRLM02R00
Abstract: (U) A simple topological model in an earlier manuscript has shown that efficient atomic packing is a fundamental principle in the formation of metallic glasses. An approach for defining and quantifying the local packing efficiency, P. was developed for solute-centered clusters that contained only solvent atoms in the first coordination shell. In the present research. this methodology is extended to allow quantification of P when more than one atomic species is present in the first coordination shell. This analysis is applied to several metallic glasses using published data of atom radii and partial coordination numbers. It is shown that packing is generally very efficient, and that the values of P obtained for the metallic classes are essentially identical to the values obtained from a similar analysis of the competing crystalline structures. These results are consistent with frequent reports of topological short range ordering in metallic glasses. and are inconsistent with a structural model on dense random packing of atoms.
ADA425235
Fundamentals of Friction and Vapor Phase Lubrication
Personal Author(s): Gellman, Andrew J
Report Date: 30 Jul 2004
Descriptors: (U) *VAPOR PHASES, *FRICTION, *LUBRICATION, ACTIVATION, HIGH TEMPERATURE, HIGH PRESSURE, CERAMIC MATERIALS, VAPOR PRESSURE, TRIBOLOGY, METAL METAL BONDS, METAL CRYSTALS
Identifiers: (U) VPL(VAPOR PHASE LUBRICATION), QUASICRYSTALLINE FILMS, *VAPOR PHASE LUBRICATION, FE(CO)5
Abstract: (U) This is the final report for the three year research program on "Fundamentals of Friction and Vapor Phase Lubrication" conducted at Carnegie Mellon with support from AFOSR grant number F49630-01-1-0069. The report summarizes the program objectives and summarizes the accomplishments and progress of the research towards the development of new methods for high temperature, vapor phase lubrication (VPL), understanding the tribological properties of quasicrystalline films and the development of a fundamental understanding of friction. The three primary objectives of the work have been: Exploration of a new approach to vapor phase lubrication of ceramics by surface activation with high vapor pressure Fe containing compounds such as Fe(CO)5; Understanding the fundamental origins of friction antisotropy in crystalline metals and lubrication of metal-metal interfaces; Probing the origins of the frictional properties of quasicrystalline surfaces through comparison with quasicrystalline approximants.
ADA427028
Photo Electron Paramagnetic Resonance (Photo EPR) Study of Trapping and Recombination Processes in Semi-Insulating 4H, 6H Sic Crystals Over a Wide Temperature Interval
Personal Author(s): Kalabukhova, Ekaterina
Report Date: 02 Jul 2004
Descriptors: (U) *TRAPPING(CHARGED PARTICLES), *RECOMBINATION REACTIONS, *SOLID STATE PHYSICS, *ELECTRON PARAMAGNETIC RESONANCE, OPTICAL EQUIPMENT, TEMPERATURE, ELECTRONIC EQUIPMENT, SUBSTRATES, CRYSTALS, SILICON CARBIDES, INTERVALS
Identifiers: (U) *PHOTO EPR(PHOTO ELECTRON PARAMAGNETIC RESONANCE), SEMI-INSULATING
Abstract: (U) This report results from a contract tasking National Academy of Sciences of the Ukraine as follows: The objective of this project is to clarify the physics and materials science of a material with great industrial potential, as a substrate used in a wide variety of electronic and optical devices. The Institute for Semiconductor Physics, with more than 15 years of experience in semiconductor material analysis, is uniquely qualified to conduct this research and has developed unique experimental facilities to carry out this investigation.
ADA425288
High Temperature Studies of La-Monazite
Personal Author(s): Marshall, David, Davis, Janet B
Report Date: Jul 2004
Descriptors: (U) *COMPOSITE MATERIALS, PLASTIC DEFORMATION, HIGH TEMPERATURE, CRACKING(FRACTURING), SINGLE CRYSTALS, STRAIN(MECHANICS), CERAMIC MATERIALS, DIELECTRIC PROPERTIES, OXIDES, BONDED JOINTS, DECOUPLING, GRAIN GROWTH, REINFORCING MATERIALS, EUTECTICS, DAMAGE TOLERANCE
Identifiers: (U) LA-MONAZITE
Abstract: (U) This report summarizes results from a 3-year research effort aimed at gaining a basic understanding of high-temperature properties of LaPO4, with a view to its application in high-temperature structural composites. Previous studies at Rockwell and the Air Force established that LaPO4 has a unique set of properties that make it suitable as a weakly bonded interphase material that enables damage tolerance by decoupling damage in the matrix and the reinforcing fibers. However, there was previously very little information on the fundamental high temperature properties of LaPO4, such as environmental stability, sintering, grain growth, mechanical and dielectric properties. Such studies require high purity powders that have only recently been produced at Rockwell. Using these materials, measurements have been made of the following properties: stability in various high temperature environments required for Air Force application, including water-containing environments typical of combustion, vacuum, and reducing environments; high-temperature creep, hardness, toughness, and sliding; low-temperature debonding, deformation, and sliding mechanisms; and dielectric properties. A preliminary assessment is made of the potential for developing directionally solidified eutectic oxide 5 stems containing LaPO4 for toughening.
ADA423843
Nanocrystal Ceramics
Personal Author(s): Alivisatos, A P
Report Date: 26 Jun 2004
Descriptors: (U) *CERAMIC MATERIALS, REACTION KINETICS, PHASE TRANSFORMATIONS, CRYSTALS, TITANIUM DIOXIDE, SOLID PHASES
Identifiers: (U) *OXIDE NANOCRYSTALS, *NANOCRYSTALLINE, SOLID-SOLID PHASE TRANSITION, NANOROD LIQUID CRYSTALS, HOLLOW CRYSTALS, *NANOCRYSTAL CERAMICS
Abstract: (U) The objectives of this report are as follows: 1) Ceramic and oxide nanocrystals will be prepared and isolated; 2) Nanocrystals will be characterized structurally; 3) Kinetic studies of reaction and phase transition processes in oxide nanocrystals.
ADA422530
Mechanical Properties of MEMS Materials
Personal Author(s): Sharpe, W N , Jr , Hemker, K J, Edwards, R L
Report Date: Mar 2004
Descriptors: (U) *MECHANICAL PROPERTIES, *MICROELECTROMECHANICAL SYSTEMS, STRESS STRAIN RELATIONS, WEIBULL DENSITY FUNCTIONS, MICROSTRUCTURE, CRYSTAL STRUCTURE, COMPOSITE MATERIALS, TENSILE PROPERTIES, THIN FILMS, SURFACE ROUGHNESS, SINGLE CRYSTALS, AMORPHOUS MATERIALS, GLASS, STRENGTH(MECHANICS), FRACTURE(MECHANICS), ELECTRON MICROSCOPY, TRANSMITTANCE, BRITTLENESS, ALUMINUM, COEFFICIENTS, THERMAL EXPANSION, LINEARITY, NICKEL, DUCTILITY, GERMANIUM, SILICON CARBIDES, FATIGUE TESTS(MECHANICS), POLYSILICONS, SILICON NITRIDES, CURVES(GEOMETRY), STRESS CONCENTRATION, ELECTROPLATING
Identifiers: (U) PE63739E, WUAFRLE1170050
Abstract: (U) New techniques and procedures were developed to measure the mechanical properties of the thin-film structural materials used in microelectromechanical systems. Tensile stress-strain curves were measured for polysilicon, silicon nitride, silicon carbide, and electroplated nickel. For example, polysilicon has a Young's modulus of 160 GPa and a Poisson's ratio of 0.22. It is a linear brittle material with fracture strength as high as 3 GPa. The mechanical properties of electroplated nickel are found to be highly dependent on the manufacturing process. Preliminary tests were conducted on silicon germanium, aluminum-glass composites, and diamond (amorphous carbon). Tests on specimens with stress concentrations show a definite size effect, i.e.,increase in fracture strength with decrease in size of highly stressed region, that is explained with Weibull statistics. Scanning and transmission electron microscopy studies of these materials relate the microstructure to the mechanical behavior. X-ray and atomic force microscopy studies show texture and surface roughness to be important features. Methods were developed to test polysilicon up to 600 deg C, and it is seen to be ductile and subject to creep at these temperatures. The coefficient of thermal expansion of polysilicon is larger than predicted from single crystal data. New axial fatigue tests at 6 kHz show polysilicon to behave much like a metal with decreased loading leading to increased life. Creep and fatigue tests were also conducted on nickel.
ADA435196
Spring 2004 Industry Study Final Report: Strategic Materials
Personal Author(s): Babus, Sylvia W , Carlson, Tom A, Jones, William F, Boslego, David V, Davis, Mark K, Dion, Denis, Doryland, David J, Harris, Mark W, Hemmrich, Steven B, Hollman, Karen A
Report Date: Jan 2004
Descriptors: (U) *POLICIES, *NATIONAL SECURITY, *UNITED STATES GOVERNMENT, *STRATEGIC MATERIALS, *ECONOMIC FORECASTING, SYMPOSIA, COMPOSITE MATERIALS, STEEL, CERAMIC MATERIALS, ALUMINUM, TITANIUM, POWDER METALLURGY, RARE EARTH ELEMENTS, STOCKPILES, NANOTECHNOLOGY, TECHNOLOGY ASSESSMENT, BIOMIMETICS, MICROELECTROMECHANICAL SYSTEMS
Abstract: (U) Strategic materials are those materials and related technologies whose critical function or supply are essential to the economic competitiveness and security of the United States. Emerging materials and technologies are key enablers to military transformation and economic growth. The United States needs to continue to fund research and development and create an environment conducive to transitioning research to manufactured products. The "Buy America" policy needs to be reviewed and the waiver process streamlined. A virtual strategic stockpile needs to be created and rare earth elements considered for stockpiling. The government must vigorously enforce the intellectual property rights of U.S. companies. While not a comprehensive study of all materials and technologies, this industry study focuses on several materials and emerging technologies that will play a significant role in ensuring the economic competitiveness and national security of the United States in the next two decades and beyond. Given the difficulty in defining the boundaries of the strategic materials "industry," the authors' purpose in this report is to present an executive summary of several key materials and technologies in a global context. Specifically, this discussion will do the following: (1) define the industry; (2) evaluate its current condition, challenges, and outlook; (3) assess the industry's contribution to national security, the nation's competitive advantage, and transformation efforts; and (4) provide recommendations for Federal Government action.
ADA452947
A Stress-Dependent Hysteresis Model for PZT-Based Transducers
Personal Author(s): Ball, Brian L, Smith, Ralph C
Report Date: Jan 2004
Descriptors: (U) *TRANSDUCERS, *LEAD ZIRCONATE TITANATES, STRESSES, SINGLE CRYSTALS, ELECTRIC FIELDS, FERROELECTRIC MATERIALS, COMPRESSIVE PROPERTIES, SWITCHING, CRYSTALS, CERAMIC MATERIALS
Abstract: (U) A ferroelastic switching model for single crystal piezoceramic compounds is developed. The model is based on a phenomenological Landau-Devonshire type thermodynamic theory for the materials. The model incorporates externally applied electric fields and compressive stress inputs to the crystals and models the 90 deg and 180 deg ferroelastic and ferroelectric switching induced by the inputs. Properties of the ferroelastic model are qualitatively similar to experimental PLZT data.
ADA419635
Superconducting and Magnetically Ordered Systems
Personal Author(s): Stronach, Carey E, Noakes, David R
Report Date: 29 Dec 2003
Descriptors: (U) *MAGNETIC PROPERTIES, *SUPERCONDUCTIVITY, ORDER DISORDER TRANSFORMATIONS, CERAMIC MATERIALS, CERIUM, TIN, NICKEL ALLOYS, RARE EARTH COMPOUNDS, GADOLINIUM, COPPER OXIDES, FERROMAGNETIC MATERIALS, STRONTIUM COMPOUNDS, ACTINIDE SERIES, MAGNETIC ALLOYS, RUTHENIUM COMPOUNDS, YTTRIUM BARIUM COPPER OXIDES
Identifiers: (U) QUASICRYSTALS, MUON SPIN ROTATION
Abstract: (U) This Report covers the period of grant F49620-97-1-0297, from April 1, 1997 to September 30, 2000. The major research findings include (a) determination of the exotic magnetic and superconducting behavior of Sr2YRuO6, (b) discovery of coexistence of ferromagnetism and superconductivity in RuSr2GdCu2O8, (c) determination of the correct expression for the strong-collision Lorentzian in fast fluctuations or high fields, (d) measurement of correlation lengths in the disordered magnetic alloys CeNi(1-x)Cu(x)Sn, (e) a study of the vortex-core structure of superconducting YBCO done with muon spin rotation, (f) preparation for publication of muonSR studies of rare earth and actinide magnetism in the Handbook on the Physics and Chemistry of Rare Earths, (g) a study of spin dynamics and freezing in magnetic rare-earth quasicrystals, and (h) a study of non-Fermi-liquid metallic Ce7Ni3.
ADA419616
Synthesis of Oxide Fibers Using a Fiber Drawing Machine
Personal Author(s): Kriven, Waltraud M
Report Date: 10 Dec 2003
Descriptors: (U) *EXTRUSION, *MACHINES, *CERAMIC FIBERS, *DRAWING(FORMING), *MONOFILAMENTS, *ALUMINOSILICATES, CORROSION RESISTANCE, REFRACTORY MATERIALS, MINERALS, THERMAL RESISTANCE, POLYCRYSTALLINE, SINTERING FURNACES, PISTON ENGINES, NANOTECHNOLOGY
Identifiers: (U) *FIBER EXTRUDERS, *MULLITE FIBERS, DRAWING MACHINES, POLYCRYSTALLINE POWDERS, POLYMERIZED PRECURSORS, POLYMERIC PRECURSORS, COMPOSITE REINFORCEMENT, CERAMIC OXIDE FIBERS
Abstract: (U) The Marksman Fiber Drawing Machine (Chemat Technology Inc., Northridge, CA) is a research scale, positive displacement, piston-type, fiber extruder. The machine was custom made to extrude various compositions of fibers from polymeric precursors specifically designed with sufficient flexibility to cover anticipated research requirements. It has a capacity of 10-150 grams, offers operational temperatures up to 500 degrees C, a 10-10,000 m/minute take-up capacity, and 2400 Watts heater capacity. It allows the continuous drawing of fiber while the diameter of the spinnerette hole can be designed to fit application requirements. Standard spinnerette orifice diameters of 200 nanometers, 150 nanometers, and 100 nanometers were supplied. In addition, an orifice diameter of 30 nanometers was custom made for research use. The machine for UIUC was custom made with an integrated high-temperature furnace to allow the fiber to be dried and sintered at elevated temperatures in three zones, up to 1,200 degrees C with programmable controls. (3 figures)
ADA445526
Synthesis, Structure and Properties of BN Nanotubes, BN/SiC and CBN/SiC Micro/Nano-Whiskers
Personal Author(s): Pokropyvnyy, Volodymyr
Report Date: 01 Dec 2003
Descriptors: (U) *MECHANICAL PROPERTIES, *SYNTHESIS(CHEMISTRY), *SILICON CARBIDES, *BORON NITRIDES, *NANOTECHNOLOGY, EXPERIMENTAL DATA, ELECTRON MICROSCOPY, ULTRASONICS, UKRAINE, PROTECTIVE COATINGS, CHEMICAL REACTIONS, DEPOSITION, X RAYS, OPTIMIZATION
Identifiers: (U) *BORON NITRIDE NANOTUBES, FOREIGN REPORTS, CHEMICAL DEPOSITION, SIC WHISKERS
Abstract: (U) This report results from a contract tasking Institute for Problems of Materials Science of Ukraine National Academy of Sciences as follows: The contractor will investigate: 1) chemical synthesis including carbothermal reduction chemical deposition and coating of nanoparticles 2) optimization of synthesis processes parameters: 3) structure examination by high-resolution electron microscopy atomic/force microscopy and X-ray analysis; 4) experimental measurements of mechanical properties
ADA417986
The Mechanisms of Creep Resistance of Advanced Ceramic Eutectics: Experiments and Modeling
Personal Author(s): Argon, Ali S
Report Date: 15 Aug 2003
Descriptors: (U) *CERAMIC MATERIALS, *CREEP STRENGTH, STRESSES, COMPUTERIZED SIMULATION, STRUCTURAL PROPERTIES, HIGH TEMPERATURE, SAPPHIRE, RANGE(EXTREMES), ZIRCONIUM OXIDES, EUTECTICS
Identifiers: (U) CERAMIC EUTECTICS, CREEP RESISTANCE
Abstract: (U) The creep resistance of the directionally solidified ceramic eutectics of alumina/cubic- zirconia was studied experimentally in the 1200-1520 degrees C, and 100-275 Mpa stress range, with associated TEM and SEM microscopy, as a generic example of ceramic eutectics. Additional (computer simulations were done both at the atomic level and by FEM methods to study: a) the core structure of pyramidal edge dislocations in alumina-that can only climb but not glide; and b) the stress distribution in the alumina component during creep. A creep model based on diffusional climb of pyramidal system edge dislocations was in very good agreement with the measured creep rates. The model predicts that the creep resistance of the eutectics should be superior to that of pure sapphire fiber in the above temperature range, and must be considered as potential candidates for high temperature structural applications. Exploitation of their full potential in high temperature composites, however, requires extensive engineering materials development.
ADA417791
Nanolaminates and Microlaminates: Modeling and Characterization
Personal Author(s): Jasiuk, Iwona, Lackey, W J
Report Date: 06 Aug 2003
Descriptors: (U) *MICROSTRUCTURE, *LAMINATES, *MICROMECHANICS, *CARBON REINFORCED COMPOSITES, *SILICON CARBIDES, *NANOSTRUCTURES, OPTIMIZATION, MODELS, POLYMERS, SYNTHESIS(CHEMISTRY), VAPOR DEPOSITION, MATRIX MATERIALS, EPOXY COMPOSITES, COBALT, NANOTECHNOLOGY, MICROELECTROMECHANICAL SYSTEMS, RESIN TRANSFER MOLDING
Identifiers: (U) PARTICLE REINFORCED COMPOSITES, POLYMER MATRIX COMPOSITES, NANOINDENTATION TECHNIQUES, COUPLE STRESS THEORY, LASER CHEMICAL VAPOR DEPOSITION
Abstract: (U) The author fabricated C/SiC laminates with layer thicknesses spanning two length scales (micrometer and nanometer) and fabricated particle-reinforced composites consisting of particles (cobalt and SiC) and polymer matrix (polysterene and epoxy) with particle diameters spanning these two scales. The laminates were made using the laser vapor deposition technique, while the particle-reinforced composites were made using either polymer synthesis or a resin transfer molding technique. The author characterized the ultrastructures of these composites using SEM and TEM, and measured their local and global properties using nanoindentation apparatus, DMA, and MTS testing equipment. The focus was on matrix-inclusion interface. Finally, they conducted modeling of such composites. This included modeling using classical micromechanics approaches which account for ultrastructural features such as interphase thickness and reinforcement shape and voids, and generalized continuum modeling using couple stress theory. The author also conducted a study of concentrated force problem using micromechanics-based continuum theory. This should be useful in interpreting nanoindentation data.
ADA416774
Creep Behavior of Polymer Precursor Derived Si3N4/SiC Nanocomposites
Personal Author(s): Mukherjee, Amiya K
Report Date: 14 Jul 2003
Descriptors: (U) *COMPOSITE MATERIALS, *CREEP, POLYMERS, PRECURSORS, DEFORMATION, SILICON CARBIDES, PYROLYSIS, SILICON NITRIDES, SINTERING, NANOTECHNOLOGY
Identifiers: (U) NANOCOMPOSITES, SPS(SPARK PLASMA SINTERING), POLYMER PRECURSORS
Abstract: (U) The creep properties of silicon nitride/silicon carbide nanocomposites were studied in compression. The material was processed using the route of pyrolysis of a polymer precursor. The extraordinary low creep rate that was experimentally measured in this project was obtained by primarily minimizing the presence of intergranular glassy phase.
ADA420043
The Effects of Adhesion and Nano-Structure on the Toughness of Polymer Nano-Composites
Personal Author(s): Kinloch, A J, Taylor, A C
Report Date: Jul 2003
Descriptors: (U) *COMPOSITE MATERIALS, *ADHESION, *TOUGHNESS, *NANOSTRUCTURES, MECHANICAL PROPERTIES, POLYMERS, HIGH TEMPERATURE, TENSILE PROPERTIES, FRACTURE(MECHANICS), CERAMIC MATERIALS, EPOXY COMPOSITES, HEAT RESISTANT MATERIALS, NANOTECHNOLOGY, UNITED KINGDOM, CARBON NANOTUBES
Identifiers: (U) FOREIGN REPORTS, *NANOCOMPOSITE MATERIALS
Abstract: (U) Epoxy nanocomposites have been manufactured using a range of modifiers, including organoclays, silica nanoparticles, carbon nanotubes and carbon nanofibres. The mechanical and fracture properties of these materials have been investigated, and the structure/property relationships discussed. Modelling methods have been used to predict the performance of these materials. Epoxy micro- and nano-composites have been manufactured using a range of inorganic modifiers, with exfoliated, intercalated and particulate morphologies. Indeed, by changing the surface treatment, and hence the interfacial adhesion, the type of morphology obtained could be varied. The modulus and fracture toughness of these composites increased with the weight fraction of modifier. The fracture toughness was increased by up to 150% with the addition of mica, but the material modified with the surface-treated clays generally showed only a small toughening effect. The modulii of the composites were in good agreement with predictions using the van-Es-modified Halpin-Tsai model. The fracture toughness of the clay-modified materials generally decreased as the degree of exfoliation increased, as the modifier acts like large particles rather than individual platelets, hence having a lower effective aspect ratio and a smaller toughening effect. The nanocomposites tend to behave in a similar manner to the microcomposites, and the same models can be applied to describe the performance of these systems.
ADA422012
X-ray Diffractometer for Texture and Residual Stress Studies of Advanced Materials
Descriptive Note: Final rept. 1 Apr 2000-31 Mar 2002
Personal Author(s): Dickey, Elizabeth C
Report Date: 01 Jul 2003
Descriptors: (U) *CERAMIC MATERIALS, *DIFFRACTOMETERS, HIGH TEMPERATURE, TENSILE STRESS, X RAY DIFFRACTION, RESIDUAL STRESS, TEXTURE, COMPRESSIVE PROPERTIES, EUTECTICS
Identifiers: (U) XRD(X-RAY DIFFRACTOMETER)
Abstract: (U) Through AFOSR DURIP grant # F49620-00-1-0245, a four circle goniometer x-ray diffractometer outfitted with a high temperature stage was purchased from Philips Analytical. The instrumentation facilitates residual stress measurements in highly textured materials up to 900 deg C. The instrument has significantly enhanced the AFOSR funded research efforts of the Pl on directionally solidified ceramic eutectics. Initial studies have measured the residual stresses in highly textured AlO3-ZrO2(Y2O3) eutectics as a function of temperature. At room temperature, significant compressive stresses (^450 MPa) are present in Al2O3 with corresponding tensile stresses in ZrO2. Through high temperature studies, the stress-free temperature was found to be ^675 deg C.
ADA416277
Chemical Precursor Routes to Ceramic Nanocylinders
Personal Author(s): Sneddon, Larry G
Report Date: 24 Jun 2003
Pagination Code: 2
Descriptors: (U) *SYNTHESIS(CHEMISTRY), POLYMERS, PRECURSORS, CERAMIC MATERIALS, CYLINDRICAL BODIES, BORON CARBIDES, SILICON CARBIDES, BORON NITRIDES, NANOTECHNOLOGY
Identifiers: (U) NONOXIDE CERAMICS
Abstract: (U) The objective this AFOSR sponsored project was to design and synthesize new processable chemical precursors to nonoxide ceramics that allow the formation of the ceramics in nano-structured forms. These studies demonstrated that the use of a suitably designed molecular or polymeric single-source precursor in conjunction with porous alumina nano-templating methods can be used for the systematic generation of aligned, monodispersed ensembles of boron carbide, boron nitride and silicon carbide ceramic nanocylinders. These methods should now be useful for the production of a wide range of nanostructured ceramics.
ADA416322
Controlled Crystallization of Amorphous Oxide Fibers
Personal Author(s): Kriven, Waltraud M
Report Date: 20 Jun 2003
Descriptors: (U) *AMORPHOUS MATERIALS, *CRYSTALLIZATION, *OXIDES, *CERAMIC FIBERS, YTTRIUM ALUMINUM GARNET, TENSILE STRENGTH, MICROSTRUCTURE, SILICON DIOXIDE, THERMODYNAMICS, POWDERS, HIGH TEMPERATURE, SINGLE CRYSTALS, TOUGHNESS, HEAT TREATMENT, RELIABILITY, ALUMINUM OXIDES, HIGH DENSITY, GRAIN GROWTH, CONTINUOUS PROCESSING, POLYCRYSTALLINE, CREEP STRENGTH
Identifiers: (U) TTT CURVES, FIBER CRYSTALLIZATION, YAG FIBERS, MULLITE FIBERS
Abstract: (U) The goal of this work is to produce creep resistant reinforcement fibers to improve the toughness and reliability of oxide ceramic composites, which are able to withstand operating temperatures of 1600 deg. C in air. We have studied crystallization mechanisms of quenched mullite (3Al2O3 (dot) 2SiO2) and YAG (Y3Al5O12), from solid amorphous or polycrystalline spheres and determined the parameters of kinetics and thermodynamics. This has enabled us to put together T-T-T curves for both systems. A four-lamp, image furnace, having a narrow hot zone and capable of operating to 2000 deg. c in air has been built and calibrated. Heat treatments can be controlled by two parameters of temperature and traverse rate (from 0.1 mm/sec to 0.025 m/sec, or 1 inch/sec). Grain growth, densification and melting can be achieved in 100 micrometers diameter monofilaments, indicating the feasibility of making textured or single crystal fibers in a continuous process. A process to extrude polycrystalline powders of green diameters approx. 140 micrometers, which densify to approx. 100 micrometers or less, has been developed. Nextel 550, 720, pure and TiO2(-) doped mullite and YAG fibers have been heat treated or melted, and a dense microstructure can been achieved. Needles of mullite form in random orientation.
ADA429655
Fabrication and Piezoelectric Properties of 1-3 Composite Sheets Consisting of Highly Oriented PZT Single Crystal Grains
Personal Author(s): Sekiya, T, Wang, R, Sato, H, Shimojo, Y
Report Date: 17 Jun 2003
Descriptors: (U) *CERAMIC MATRIX COMPOSITES, *FABRICATION, *SINGLE CRYSTALS, *SHEETS, *PIEZOELECTRIC TRANSDUCERS, SYMPOSIA, DIELECTRICS, PIEZOELECTRICITY, HYSTERESIS, GRAIN STRUCTURES(METALLURGY), FLUXES(FUSION), POLYIMIDE RESINS, LEAD OXIDES
Identifiers: (U) RHOMBOHEDRAL CRYSTALS, FOREIGN REPORTS
Abstract: (U) Cube-shaped PZT single crystals with PZ/PT=55/45 composition were grown in a relatively uniform size distribution around 80 micrometers by a PbO-flux method. The PZT grains obtained were mixed with liquid polyimide resin and rolled on a glass plate to fabricate 1-3-type composite sheet. This rolling process resulted in a high orientation of the PZT grains as the ?h00! are parallel to the substrate plane. The degree of grain orientation reached about 90%. After heating at 180 degrees C, the composite sheet showed a well-defined DE hysteresis loop due to the dielectric property of PZT grains. The longitudinal field-induced strain was 0.2% at 120kV/cm.
Distribution Statement: Availability: This document is not available from DTIC in microfiche.
ADA429654
Effect of Yb Addition on the Sintering Behavior and High Power Piezoelectric Properties of Pb(Zr,Ti)O3-Pb(Mn,Nb)O3
Personal Author(s): Ryu, J, Kim, H W, Uchino, Kenji
Report Date: 17 Jun 2003
Descriptors: (U) *CERAMIC MATERIALS, *PIEZOELECTRICITY, *SINTERING, *YTTERBIUM, VELOCITY, VIBRATION, SYMPOSIA, DIELECTRICS, DOPING, POLYCRYSTALLINE, PEROVSKITES, PIEZOELECTRIC TRANSDUCERS
Abstract: (U) Piezoelectric ceramics doped with Yb2O3 were prepared by conventional ceramic processing, and the effects of the Yb doping on the sintering behavior and high power piezoelectric properties were investigated. XRD measurements indicated that the piezoelectric ceramics with Yb2O3 in this study were a single phase of polycrystalline perovskite. The sintering density was strongly affected by small amount of Yb2O3 addition. Vibration velocity, which is one of the most important factors for high power piezoelectric applications, as high as 1.0 m/s (rms value), was obtained from the 0.2 mol% Yb2O3 doped sample. This value is about 2.5 times higher than that for commercialized hard PZT ceramics.
ADA415889
Focused Topical Session: Oxide/Oxide Ceramics and Composites Meeting; Annual Cocoa Beach Conference (27th) and Exposition on Advanced Ceramics and Composites Held in Cocoa Beach on 26-31 January 2003
Personal Author(s): Sayir, A
Report Date: 15 Jun 2003
Descriptors: (U) *COMPOSITE MATERIALS, *CERAMIC MATERIALS, *OXIDES, AIR BREATHING ENGINES, MICROSTRUCTURE, SYMPOSIA, HIGH TEMPERATURE, LOADS(FORCES), FIBER REINFORCED COMPOSITES, OXIDATION, ADVERSE CONDITIONS, AEROSPACE INDUSTRY, STRUCTURAL COMPONENTS
Abstract: (U) Advanced materials are usually composite materials for structural components to carry loads and/or functional components to accomplish specific tasks. Oxide ceramic, oxide fiber reinforced ceramic composites and in-situ composites stand out as those which provide best properties in oxidizing environment. The oxide materials are essential to withstand severe loads in the oxidizing environment a severe conditions. The oxide ceramics and oxide composites is a crucial research area because it's importance to air breathing engine technology of US Air Force, Department of defense and US civilian industry. The components of the oxide ceramics and their composites are essential for the future aerospace industry and the information of their behavior is critical to understand the response of composites. Three focused topical session on the Oxide ceramics and Composites has been organized at the 27 Annual Cocoa Beach Conference and Exposition on Advanced Ceramics & Composites meeting. These sessions were: (i) Intrinsic Properties of Oxides (Magnetic, Electrical, Optical, Mechanical), (ii) Microstructures and Mechanical Behavior (iii) Novel Processing Techniques. The proposed meeting provided a forum for discussing the essential scientific issues involved in the development and use of high temperature materials.
ADA429539
High Performance Materials by the Powder Particle Assemblage
Personal Author(s): Kobayashi, M, Miyazaki, H T, Shinya, N
Report Date: Jun 2003
Descriptors: (U) *NANOTECHNOLOGY, *SMART TECHNOLOGY, *PHOTONIC CRYSTALS, SCANNING ELECTRON MICROSCOPES, SYMPOSIA, POWDERS, OPTICAL MATERIALS, JAPAN, THREE DIMENSIONAL, CERAMIC MATERIALS, PARTICLES, PENNSYLVANIA, HEATERS
Identifiers: (U) *HIGH PERFORMANCE MATERIALS, *INTELLIGENT MATERIALS, *POWDER PARTICLE ASSEMBLAGE, COMPONENT REPORTS, FOREIGN REPORTS, OPTICAL MICROSCOPIC OBSERVATION
Abstract: (U) The techniques of the particle assemblage have been developed to create intelligent materials by assembling particles. The particle assemblage techniques of particle arrangement, probe manipulation and composition are introduced in this paper. The probe manipulation is carried out in the air under optical microscopic observation and in vacuum under the SEM observation. We can fabricate 3-dimensional structures as designed from fine particles to some extent. Photonic crystals and ceramics heaters are fabricated by the probe manipulation in SEM and by the composition, respectively.
ADA429575
Long Fiber Formation of Hydroxyapatite/Collagen Nanocomposites through a Self-Organization Mechanism
Personal Author(s): Kikuchi, M, Tanaka, J, Itoh, S, Shinomiya, K
Report Date: Jun 2003
Descriptors: (U) *FIBERS, *COMPOSITE MATERIALS, *CERAMIC MATERIALS, *COLLAGEN, *BONES, *NANOTECHNOLOGY, *BIOMIMETICS, EXTINCTION, POLARIZATION, SYMPOSIA, BIOCHEMISTRY, METABOLISM, JAPAN, CROSSLINKING(CHEMISTRY), SORPTION, BIOMECHANICS, CRYSTAL GROWTH, SELF ORGANIZING SYSTEMS, IONIC STRENGTH
Identifiers: (U) *HYDROXYAPATITE, *ARTIFICIAL BONE, ARTIFICIAL TISSUE, RESORPTION, BIOMATERIALS, BIOCERAMICS, COMPONENT REPORTS, FOREIGN REPORTS
Abstract: (U) Long fibers of bone-like hydroxyapatite/collagen nanocomposites were fabricated via a self-organization under biomimetic conditions to obtain much more suitable biomechanical and biochemical properties for artificial bone and tissue engineering scaffolds. The fiber growth was controlled with ionic strength in the reaction vessel and was explained by a crystal growth model. The composite fiber grew up to 75 mm in length and demonstrated straight extinction under a polarized microscope. The composite compacts were incorporated into bone metabolism, and their resorption was controlled with cross linkage. The composite is utilizable for the bone reconstruction materials that can gradually change into bone.
ADA429564
Bending Behavior of Monolithic Ba(Ti,Sn)O3-Ceramics with a Functionally Gradient of the Piezoelectric Properties
Personal Author(s): Steinhausen*, R, Kouvatov, A, Pientsclilce, C, Seifert, W, Beige, H
Report Date: Jun 2003
Descriptors: (U) *PIEZOELECTRIC EFFECT, SYMPOSIA, LOW COSTS, CERAMIC MATERIALS, RESONANT FREQUENCY, APPROXIMATION(MATHEMATICS), MONOLITHIC STRUCTURES(ELECTRONICS), NANOTECHNOLOGY
Abstract: (U) Functionally Gradient Materials are suitable for bending devices due to reduced internal mechanical stresses and lower production costs. Monolithic BaTi(sub l-x)Sn(sub x)O(sub 3) (BTS) ceramics with a gradient of the Sn-content (0.075 less than or equal x less than or equal .15) were prepared. The chemical gradient was transformed into a gradient of the piezoelectric properties by a poling process. The bending deflection was measured as a function of the applied voltage and compared with analytical approximations. Additionally the resonance frequencies and the damping behavior of samples with different Sn-contents were investigated. The monolithic ceramics showed good results in comparison with conventional glued bending devices.
ADA429580
Structural and Microwave Dielectric Properties of Sr(1-X/2)Na(X)Nb2O6 Ferroelectric Ceramics
Personal Author(s): Yohannan, Jaimon, Jacob, Joe, Lonappan, Anil, Mathew, K T
Report Date: Jun 2003
Descriptors: (U) *CRYSTAL STRUCTURE, *STRUCTURAL PROPERTIES, *MICROWAVES, *DIELECTRIC PROPERTIES, SCANNING ELECTRON MICROSCOPES, MICROSTRUCTURE, SYMPOSIA, REACTION KINETICS, ELECTROMAGNETIC PROPERTIES, X RAY DIFFRACTION, DIELECTRICS, CERAMIC MATERIALS, RESONANT FREQUENCY, COEFFICIENTS, CONSTANTS, TEMPERATURE COEFFICIENTS, PENNSYLVANIA, NIOBATES, SODIUM COMPOUNDS
Identifiers: (U) *FERROELECTRIC CERAMICS, *PERMITTIVITY, COMPONENT REPORTS, FOREIGN REPORTS, PVA(BINDER POLYVINYL ALCOHOL), DIELECTRIC CONSTANTS, TETRAGONAL TUNGSTEN BRONZE
Abstract: (U) Strontium sodium niobate ceramics are prepared by solid state reaction method. The crystal structures of these ceramics are studied by X-ray powder diffraction method. These materials are found to crystallize in the tetragonal tungsten bronze type structure and the unit cell parameters are calculated. The microstructural features were studied using scanning electron microscope. The real and imaginary part of complex Permittivity of the sample is determined by cavity perturbation technique. It is observed that the real and imaginary part of complex Permittivity varies with frequency. The temperature coefficient of dielectric constant and resonant frequency is found to be very small.
ADA415290
T2 Success within the Material Applications Branch of AFRL's Propulsion Directorate
Personal Author(s): Phillips, Shawn
Report Date: 01 May 2003
Descriptors: (U) *PLASTICS, *CHEMICAL ENGINEERING, *NANOTECHNOLOGY, CERAMIC MATRIX COMPOSITES, SILOXANES, PROPULSION SYSTEMS, CARBON CARBON COMPOSITES, OLIGOMERS, NANOSTRUCTURES
Identifiers: (U) *HYBRID PLASTICS, POSS(POLYHEDRAL OLIGOMERIC SILSESQUIOXANE), DENSIFICATION, VIEWGRAPHS ONLY, PRESENTATION SLIDES, WUAFRL2303M1A3
ADA420282
Basic Studies on Templated Grain Growth of Relaxor Ferroelectric Crystals and Textured Ceramics
Personal Author(s): Messing, Gary L, Trolier-McKinstry, Susan
Report Date: 30 Apr 2003
Descriptors: (U) *CERAMIC MATERIALS, *TEMPLATES, *TEXTURE, *GRAIN GROWTH, *FERROELECTRIC CRYSTALS, LOW COSTS, FABRICATION, SINGLE CRYSTALS, ELECTRICAL PROPERTIES, ELECTROMECHANICAL DEVICES, PIEZOELECTRIC MATERIALS, BARIUM TITANATES, HYSTERESIS
Identifiers: (U) *RELAXOR, SODIUM BISMUTH TITANATES, RHOMBOHEDRON
Abstract: (U) Templated grain growth (TGG) enables the relatively low cost fabrication of textured ceramics with single crystal-like properties, as well as single crystals. The resulting ceramics show texture levels up to 90%, and significant enhancements in the piezoelectric properties relative to randomly oriented ceramics with comparable densities. The piezoelectric coefficients of highly textured PMN-32.5PT ceramics were found to be ^1.2- 1.5 times greater than randomly-oriented samples. The unipolar strain-field measurements (<S kV/cm) of 90%-textured PMN-32.5PT ceramics produced piezoelectric coefficients as high as 1150 pC/N with relatively low piezoelectric hysteresis. Electrical and electromechanical property characterization of<001>pc textured sodium bismuth titanate - 5.5 mol% barium titanate rhombohedral ceramics showed 0.26% strain at 70 kV/cm, and large field piezoelectric coefficients over 500 pC/N were obtained for highly textured samples (f^90%). Reasons are given for why the high field dielectric and electromechanical properties are more hysteretic than those of single crystals.
ADA415847
A Systematic Study of the Failure Wave Phenomenon in Brittle Materials
Personal Author(s): Kanel, G I, Bogatch, A A, Razorenov, S V, Savinykh, A S
Report Date: Apr 2003
Descriptors: (U) *THRESHOLD EFFECTS, *SHOCK WAVES, *CERAMIC MATERIALS, *BRITTLENESS, *FAILURE(MECHANICS), STRESSES, COMPUTERIZED SIMULATION, PROPAGATION, SINGLE CRYSTALS, QUARTZ, ALUMINUM OXIDES, SILICON, EVOLUTION(GENERAL), RUSSIA, BORON CARBIDES, RANGE(DISTANCE), PILE STRUCTURES, COMPRESSIVE PROPERTIES, POLYCRYSTALLINE, COMMINUTION, OPTICAL GLASS
Identifiers: (U) AQ F03-10-2396, FOREIGN REPORTS
Abstract: (U) Shock-wave experiments with four glasses of different hardness, two ceramics, quartz and silicon single crystals have been carried out with the goals to better understand in which materials the failure wave may occur under shock compression, which material properties control the formation and propagation, and what are the threshold conditions. Experiments with piles of thin sample plates confirm the appearance of the failure wave in elastically compressed fused quartz, K8 crown glass, and heavy flint glass, although the relationships between the Hugoniot elastic limits and the failure thresholds of these glasses are different. For softest heavy flint glass, the failure threshold is closest to the HEL. The failure waves were not recorded in single crystals and polycrystalline alumina and boron carbide ceramics. The results show that the propagation speed of the failure wave in glass slightly depends on the stress above the failure threshold, and does not depend on the propagation distance. The process becomes unstable and stops at stresses near the failure threshold. Longitudinal compressibility of comminuted glass has been found close to that of intact material. Preliminary results of computer simulations demonstrate the potential of the combustion-like model in simulating the evolution of failure wave.
ADA411043
Defects in SiC Single Crystals and Their Influence on Device Performance
Personal Author(s): Dudley, Michael
Report Date: 04 Feb 2003
Descriptors: (U) *DISLOCATIONS, *CRYSTAL DEFECTS, *SILICON CARBIDES, SCANNING ELECTRON MICROSCOPES, MICROSTRUCTURE, VOLTAGE, SINGLE CRYSTALS, SEMICONDUCTORS, X RAYS, TOPOGRAPHY, ELECTRICAL PROPERTIES, MICROSCOPY, ELECTRON MICROSCOPY, TRANSMITTANCE, DEFECTS(MATERIALS), OPTICAL ANALYSIS, PIEZOELECTRIC MATERIALS, RESONATORS, PARALLEL ORIENTATION, ELECTRIC CURRENT, CRYSTAL GROWTH, BREAKDOWN(ELECTRONIC THRESHOLD), STRIATIONS, SYNCHROTRONS
Identifiers: (U) *SUPERSCREW DISLOCATIONS, SYNCHROTRON X RAY TOPOGRAPHY, DEVICE PERFORMANCE, SWBXT(SYNCHROTRON WHITE BEAM X RAY TOPOGRAPHY), NOMARSKI OPTICAL MICROSCOPY, 4H-SIC, 6H-SIC, HEXAGONAL, BURGERS VECTOR, OPTOELECTRONIC DEVICES, STEREO TRANSMISSION OPTICAL MICROSCOPY
Abstract: (U) This extensive program of research aims to apply the techniques of Synchrotron White Beam X-ray Topography (SWBXT), Nomarski Optical Microscopy. Scanning Electron Microscopy. Transmission Electron Microscopy (TEM). and I-V Characteristic Probing to the detailed analysis of defect structures in SiC Single Crystals of various polytypes, and to determine how these defect structures can influence the performance of various kinds of device manufactures therefrom. Results obtained so far indicate that devices without screw dislocations exhibited excellent characteristics, with no detectable leakage current prior to breakdown, a sharp breakdown I-V knee, and no visible concentration of breakdown current. In contrast, devices that contained at least one elementary screw dislocation exhibited a 5% to 35% reduction in breakdown voltage, a softer breakdown I-V knee, and visible microplasmas at the sites of the screw dislocations. In addition a new strategy for preparing defect free 3C epilayers on 4H substrates was investigated. The success of this strategy was assessed using SWBXT,and results obtained to date reveal that high quality, poytype controlled 3C could be grown. The scope of the project was modified to encompass parallel studies of the influence of defect microstructure on the performance of resonators made from single crystals of the novel piezoelectric materials Langasite, Langanite and Langatate. Early results have indicated the presence of growth striations, dislocations and precipitates. The influence of these defects on device performance is being systematically studied.
ADA410953
Material Applications Research Within the Propulsion Directorate of the Air Force Research Laboratory
Personal Author(s): Phillips, Shawn H
Report Date: 27 Jan 2003
Descriptors: (U) *AIR FORCE RESEARCH, *POLYMERS, *COMPOSITE MATERIALS, HIGH TEMPERATURE, CERAMIC MATRIX COMPOSITES, FRACTURE(MECHANICS), SILOXANES, CARBON CARBON COMPOSITES, MONOMERS, ROCKET PROPULSION, NANOTECHNOLOGY
Identifiers: (U) VIEWGRAPHS, IHPRPT(INTEGRATED HIGH PAYOFF ROCKET PROPULSION TECHNOLOGY), POSS(POLYHEDRAL OLIGOMERIC SILSESQUIOXANE), WUAFRL48470249
Abstract: (U) Viewgraphs for presentation on materials research and development conducted by the Air Force Research Lab Propulsion Directorate, Edwards AFB, California, and its subdivisions.
ADA443876
A Free Energy Model for Hysteresis Ferroelectric Materials
Personal Author(s): Smith, Ralph C, Ounaies, Zoubeida, Seelecke, Stefan, Smith, Joshua
Report Date: Jan 2003
Descriptors: (U) *FERROELECTRIC MATERIALS, STOCHASTIC PROCESSES, PHYSICAL PROPERTIES, SINGLE CRYSTALS, HYSTERESIS, HELMHOLTZ EQUATIONS, HOMOGENEITY, FREE ENERGY, CERAMIC MATERIALS, PIEZOELECTRIC MATERIALS
Abstract: (U) This paper provides a theory for quantifying the hysteresis and constitutive nonlinearities inherent to piezoceramic compounds through a combination of free energy analysis and stochastic homogenization techniques. In the first step of the model development, Helmholtz and Gibbs free energy relations are constructed at the lattice or domain level to quantify the relation between the field and polarization in homogeneous, single crystal compounds which exhibit uniform effective fields. The effects of material nonhomogeneities, polycrystallinity, and variable effective fields are subsequently incorporated through the assumption that certain physical parameters, including the local coercive and effective fields, are randomly distributed and hence manifestations of stochastic density functions associated with the material. Stochastic homogenization in this manner provides low-order macroscopic models with effective parameters that can be correlated with physical properties of the data. This facilitates the identification of parameters for model construction, model updating to accommodate changing operating conditions, and control design utilizing model-based inverse compensators. Attributes of the model, including the guaranteed closure of biased minor loops in quasistatic drive regimes, are illustrated through examples.
ADA411707
Synthesis and Atomic Oxygen Erosion Testing of Space-Survivable POSS (Polyhedral Oligomeric Silsesquioxane) Polyimides
Personal Author(s): Gonzalez, Rene L, Tomczak, Sandra J, Hoflund, Gar B, Minton, Timothy K, Brunsvold, Amy
Report Date: 16 Dec 2002
Descriptors: (U) *DEGRADATION, *CERAMIC MATERIALS, *ORGANIC MATERIALS, *SPACECRAFT COMPONENTS, *OXIDATION RESISTANCE, *POLYIMIDE PLASTICS, *INORGANIC POLYMERS, THERMAL PROPERTIES, OPTICAL PROPERTIES, MECHANICAL PROPERTIES, SPACE ENVIRONMENTS, BLENDING, POLYMERS, SYNTHESIS(CHEMISTRY), LIGHTWEIGHT, SOLAR RADIATION, EROSION RESISTANCE, RADIATION DAMAGE, NANOTECHNOLOGY
Identifiers: (U) *HYBRID POLYMERS, *POSS(POLYHEDRAL OLIGOMERIC SILSESQUIOXANE), *ATOMIC OXYGEN, INORGANIC ORGANIC POLYMERS, WUAFRL23030026
Abstract: (U) The harsh environment present in both low-earth and geosynchronous orbit combined with the need for lighter weight and lower cost man-made orbiting bodies necessitates the design of multi-functional, space-survivable materials. Over the last two decades it has been well established that conventional polymers used in the construction of space vehicles undergo severe degradation resulting in reduced spacecraft lifetimes. In particular, the polyimide Kapton has been studied at length since it is widely used as a flexible substrate for lightweight high power solar arrays because of its inherent strength and desirable thermal properties. In addition to Kapton, thin films of fluorinated polymers such as Teflon FEP are used as the outer layer of multi-layer thermal control insulation because of their superior optical properties, including low solar absorptance and high thermal reflectance. These polymeric materials degrade because spacecraft surfaces must endure a high incident fluences of atomic oxygen (AO), bombardment by low and high-energy charged particles, and thermal cycling along with the full spectrum of solar radiation. Hybrid inorganic/organic polymers have the potential to meet the requirements of space-survivable materials by bridging the gap between ceramics and plastics, resulting in the prevention of AO and radiation damage that has hampered the widespread application of organic polymers in space. The Polymer Working Group at the Air Force Research Laboratory at Edwards AFB has incorporated inorganic POSS (Polyhedral Oligomeric Silsesquioxane) frameworks into traditional polymer systems resulting in hybrid POSS-polymers with dramatic property enhancements. Addition of these POSS nanostructured frameworks into polymers results in increased use and decomposition temperatures, improved mechanical properties, and oxidation resistance.
ADA414580
Symposium K: Silicon Carbide - Materials, Processing, and Devices
Personal Author(s): Saddow, Stephen E, Saks, Nelson S, Larkin, David J, Schoener, Adolf
Report Date: Dec 2002
Descriptors: (U) *MATERIALS, *EPITAXIAL GROWTH, *SILICON CARBIDES, HIGH FREQUENCY, HIGH TEMPERATURE, SUBSTRATES, CRYSTALS, HIGH VOLTAGE
Abstract: (U) Symposium K is the second in a series of SiC symposia at the MRS Fall Meeting. Since the last meeting in 2000, advances in SiC materials, processing, and device design have resulted in implementation of SiC-based electronic systems and offer great promise in high voltage, high temperature, high frequency applications. Presenters focused on new developments in the basic science of SiC materials as well as rapidly maturing device technologies. The challenges in this field include understanding and decreasing defect densities in bulk SiC crystals, controlling morphology and residual impurities in epilayers, optimization of implant activation and oxide-SiC interfaces, and developing novel device structures. Topics of particular interest were in the area of bulk SiC growth (including large-diameter crystals), modeling, characterization, homo- and heteroepitaxial growth (e.g., doping control, morphology development, and carrier lifetimes), advances in ion implantation, improved ohmic and rectifying contacts, surfaces and interfaces, oxidation, and alternative dielectric materials and devices (including high-voltage, high-temperature, high-frequency sensors and system level benefits).
ADA415295
Journal of Crystal Growth Volume 246, Nos. 1-2, pp.1-176, December 2002
Personal Author(s): Stringfellow, G B, Schieber, M, Feigelson, R S, Hurle, D T, Kern, R
Report Date: 01 Dec 2002
Descriptors: (U) *EPITAXIAL GROWTH, STRESSES, BUFFERS, CRYSTAL STRUCTURE, PHASE TRANSFORMATIONS, QUANTUM WELLS, GALLIUM ARSENIDES, MORPHOLOGY, THIN FILMS, SINGLE CRYSTALS, ETCHING, IMPURITIES, ROOM TEMPERATURE, ELECTRON BEAMS, THERMAL ANALYSIS, SURFACE PROPERTIES, CRYSTAL DEFECTS, MASS TRANSFER, SUBLIMATION, TIN, TEMPERATURE CONTROL, DIFFUSION, DOPING, N TYPE SEMICONDUCTORS, SULFUR, ARSINES, BARIUM TITANATES, SPUTTERING, RADIOFREQUENCY, SILICON CARBIDES, TITANIUM BORIDE, TELLURIUM, ULTRAHIGH VACUUM, ANTHRACENES, SPECULAR REFLECTION, MAGNETRONS, FERROELECTRICITY, MOLECULAR BEAM EPITAXY, GALLIUM NITRIDES, ALUMINUM NITRIDES, NANOSTRUCTURES, ALUMINUM GALLIUM NITRIDES
Identifiers: (U) COMPILATION REPORT, TRIETHYLGALLIUM, PLASMA ASSISTED, FZ(FLOATING ZONE), EPITAXIAL LATERAL OVERGROWN, DRSSVBT(DOUBLE RUN SELECTIVE SELF SEEDING VERTICAL BRIDGMAN TECHNIQUE), CADMIUM SULFIDES, NANOWIRES
Abstract: (U) Partial Contents: Classical semiconductors. Temperature control in InGaAs-based quantum well Structures grown by molecular beam epitaxy on GaAs (100) and GaAs (111)B substrates; Atomic depth distribution and growth modes of Sn on Si(1111 41-In and alpha-33-Au surfaces at room temperature; Enhanced impurity incorporation by alternate Te and S doping in GaAs prepared by intermittent injection of triethylgallium and arsine in ultra high vacuum; Defect-selective etching of GaN in a modified molten bases system; N-type doping behavior of Al(0.15)Ga(0.85)N:Si with various Si incorporations; On mass transport and surface morphology of sublimation grown 4H silicon carbide; A global thermal analysis of multizone resistance furnaces with specular and diffuse samples; The role of growth conditions on the p-doping of GaN by plasma-assisted molecular beam epitaxy; A new phenomenon in the floating-zone (FZ) growth of Si nanowires; Structural characterization of epitaxial lateral overgrown GaN on patterned GaN/GaAs(001) substrates; Temperature dependence of stresses in GaN/AlN/6H SiC(0001) structures: correlation between AlN buffer thickness and intrinsic stresses in GaN; Crystal structure and ferroelectricity of nanocrystalline barium titanate thin films; Preparation of high quality anthracene crystals using double run selective self-seeding vertical Bridgman technique (DRSSVBT); Relationships between DTA and DIL characteristics of nano-sized alumina powders during 0- to alpha-phase transformation; Characteristics and crystal structure of the Ba(Zr(x) Ti(1-x)O3 thin films deposited by RF magnetron sputtering.
ADA411961
Defect Characterization of Pyroelectric Materials
Personal Author(s): Keeble, David J
Report Date: Nov 2002
Descriptors: (U) *FERROELECTRIC MATERIALS, *PYROELECTRICITY, SPECTROSCOPY, COUNTING METHODS, BACKSCATTERING, POINT DEFECTS, IMPURITIES, CERAMIC MATERIALS, PURITY, SPECTRA, NONLINEAR SYSTEMS, OXIDES, LEAST SQUARES METHOD, ATOMIC PROPERTIES, SPECTROMETERS, ENTROPY, ELECTRON PARAMAGNETIC RESONANCE, POLYCRYSTALLINE, POSITRONS, ANNIHILATION REACTIONS, ANNIHILATION RADIATION, UNITED KINGDOM, LEAD ZIRCONATE TITANATES
Identifiers: (U) AQ F03-06-1032, FOREIGN REPORTS, PLZT(LEAD LANTHANUM ZIRCONATE TITANATE), OXIDE MATERIALS, POSITRON ANNIHILATION, PYROELECTRIC MATERIALS
Abstract: (U) Two methods for identify point defects applicable to the study of technologically relevant pyroelectric oxide materials have been investigated, namely Positron Annihilation Lifetime Spectroscopy (PALS) and Electron Paramagnetic Resonance (EPR). For this study a PALS spectrometer was constructed. Preliminary PALS and EPR results on powder and ceramic materials are presented. An operational positron annihilation lifetime spectrometer has been constructed and tested. The resolution function width of approximately 205 ps with a count rate of 130 counts S(-1) from a 370 kBq(-1) source was achieved. Two independent analysis algorithms were tested using simulated lifetime spectra. Systematic studies were performed on a series of polycrystalline pure metal samples. This work confirmed the need for accurate source annihilation correction and allowed a methodology to be developed. Further, this procedure allowed the variation in backscatter source contribution with atomic number to be studied. The spectrometer was then used to study two pyroelectric Pb based perovskite oxide ceramic samples, a La doped PZT sample, (Pb,La)(Zr,Ti)O3, and an undoped Pb(Sc(0.5),Ta(0.5))O3 (PST) sample. Fits using maximum entropy method and source corrected fitting using non-linear least square where found to be similar. A second vacancy defect contribution was clearly observed in both samples. Electron paramagnetic resonance measurements were extended from earlier single crystal PbTiO3 work to powder Pb(Zr,Ti)O3 samples. A series of Mn doped samples was studied. The spectrum was found to contain contributions from both Mn(4+) and Mn(2+) charge states.
ADA410104
Science for Materials in the Frontier of Centuries: Advantages and Challenges, Volume 2
Report Date: Nov 2002
Descriptors: (U) *METALS, *COMPOSITE MATERIALS, *CERAMIC MATERIALS, SYMPOSIA, SPECTROSCOPY, REACTION KINETICS, PHASE TRANSFORMATIONS, POLYMERS, SYNTHESIS(CHEMISTRY), AMORPHOUS MATERIALS, CRYSTALS, FULLERENES, ALLOYS, COATINGS, ACOUSTICS, SINTERING, CERMETS, UKRAINE, EUTECTICS, NANOTECHNOLOGY
Identifiers: (U) AQ F03-03-0435, FOREIGN REPORTS, PROCEEDINGS, NANOCRYSTALLINE
Abstract: (U) The Final Proceedings for Science for Materials in the Frontier of Centuries: Advantages and Challenges, 4 Nov 02-8 Nov 02. I. Fundamental problems of materials science including phase transformations, reaction kinetics, deformation of materials, materials modeling, and surface phenomena. II. Prospective materials for functional and structural purposes as composites, ceramics, amorphous and nanocrystalline materials, quasi-crystals, fullerenes, nano-tubes, intermetallics, eutectic materials, hard alloys and cermets. III. Materials processing routes including materials synthesis in the bulk and dispersed states, self-propagating high- temperature synthesis, powder formation, sintering, joining, and coating. IV. Characterization of materials properties using non-destructive methods, microscopy, spectroscopy, acoustics, and x-ray.
ADA408965
Science for Materials in the Frontier of Centuries: Advantages and Challenges. Volume I
Personal Author(s): Skorokhod, Valery V
Report Date: Nov 2002
Descriptors: (U) *METALS, *SYMPOSIA, *MATERIALS, *POLYMERS, *ALLOYS, TEMPERATURE, NONDESTRUCTIVE TESTING, MODELS, SPECTROSCOPY, REACTION KINETICS, SYNTHESIS, PHASE TRANSFORMATIONS, POWDERS, PROCESSING, DEFORMATION, CRYSTALS, FULLERENES, MICROSCOPY, CERAMIC MATERIALS, COATINGS, SURFACE PROPERTIES, ACOUSTICS, SINTERING, CERMETS, EUTECTICS
Identifiers: (U) AQ F03-03-0434
Abstract: (U) The Final Proceedings for Science for Materials in the Frontier of Centuries: Advantages and Challenges, 4 Nov O2-8 Nov O2 I. Fundamental problems of materials science including phase transformations, reaction kinetics, deformation of materials, materials modeling, and surface phenomena. II. Prospective materials for functional and structural purposes as composites, ceramics, amorphous and nano- crystalline materials, quasi-crystals, fullerenes, nano-tubes, intermetallics, eutectic materials, hard alloys and cermets. III. Materials processing routes including materials synthesis in the bulk and dispersed states, self-propagating high- temperature synthesis, powder formation, sintering, joining, and coating. IV. Characterization of materials properties using non-destructive methods, microscopy, spectroscopy, acoustics, and X-ray.
ADA407276
Self-Starting Solid-State Laser with Dynamic Self-Adaptive Cavity
Personal Author(s): Antipov, Oleg
Report Date: 04 Oct 2002
Descriptors: (U) *SOLID STATE LASERS, HIGH POWER, OSCILLATORS, LASER PUMPING, YAG LASERS, LASER CAVITIES, FLUORESCENCE, REFRACTIVE INDEX, SINGLE CRYSTALS, LASER BEAMS, CERAMIC MATERIALS, GRATINGS(SPECTRA), HOLOGRAPHY, NONLINEAR SYSTEMS, RUSSIA, DRILLING, CUTTING, NEODYMIUM LASERS, INDUSTRIAL EQUIPMENT
Identifiers: (U) FOREIGN REPORTS, GAIN GRATINGS, POPULATION GRATINGS, SPOT THERMO-HARDENING
Abstract: (U) This report results from a contract tasking Institute of Applied Physics as follows: The present project is directed at the development of physical principles of creation of solid-state lasers of a new class with cavity completed by dynamic holographic gratings induced in nonlinear medium by generating beam itself. The self-starting laser oscillator based on Nd:YAG laser crystals with cavity formed with participation of refractive-index and gain gratings accompanied by population gratings induced in the laser crystal by generating waves will be studied both experimentally and theoretically. The industry-related importance of our project is indicated in its main goal: the solution of a very important problem of laser engineering, - that is the creation of a high power industrial laser with good beam quality. Such lasers could find numerous applications in precision technologies such as drilling of small apertures, cutting, spot thermo-hardening of metals, treatment of ceramics and other materials.
ADA407959
A Pulsed Laser Deposition Facility for the Synthesis of Novel Surface Engineered and Electronic Ceramic Materials
Personal Author(s): Sankar, J, Kumar, D, Yarmolenko, S, Lee, Clinton, Pai, D
Report Date: 31 Aug 2002
Descriptors: (U) *THIN FILMS, *FABRICATION, *PULSED LASERS, *DEPOSITION, SYNTHESIS, COMPOSITE MATERIALS, UNIVERSITIES, EXCIMERS, MATERIALS LABORATORIES, CRYSTALLOGRAPHY
Identifiers: (U) NANOCRYSTALS, PLD(PULSED LASER DEPOSITION)
Abstract: (U) The acquired funding from ARO was efficiently used to set-up a pulsed laser deposition (PLD) facility at the NCAT campus. The PLD technique is one of the most popular and effective techniques used in the present days for the deposition of thin films. In this technique, a pulsed laser (usually an excimer) is directed on a solid target. The PLD facility at NCAT campus has added a new dimension to the various research and educational activities taking place at our campus under the umbrella of NSF Center for Advanced Materials and Smart Structures. We have carried out a number of important experiments using the PLD facility in NOAT campus. These experiments have resulted in several publications in peered reviewed journals. A list of these publications can be seen at http://camss.ncat.edu.
ADA421560
Life Prediction Methodologies for Aerospace Materials Annual Report, 2002
Personal Author(s): Ashbaugh, N E, Brockman, R A, Buchanan, D J, Hartman, G A, Hutson, A L
Report Date: Jun 2002
Descriptors: (U) *LIFE EXPECTANCY(SERVICE LIFE), *ALUMINUM ALLOYS, *CERAMIC MATRIX COMPOSITES, *AEROSPACE SYSTEMS, *TITANIUM ALUMINIDE, THERMOMECHANICS, CRACK PROPAGATION, CRYSTALLOGRAPHY
Identifiers: (U) AEROSPACE MATERIALS, PE62102F, WUAFRL43475201
Abstract: (U) Three types of models to predict behavior of gamma titanium aluminide (g-TiAl) alloys in a high temperature turbine engine environment were developed and have been refined: (a) a model to evaluate linear elastic response, (b) a crystal plasticity model, and (c) a computational model for analyzing stress variations within polycrystals of g-TiAl. Orientation-imaging microscopy (OIM) has been used to understand the role that crystallographic orientation plays with respect to fatigue crack initiation and growth. Mechanical tests have been conducted on various ceramic matrix composites to determine their viability in applications such as exhaust wash structures, exhaust nozzle flaps and seals and combustor liners. Models have been developed for determining effective thermoelastic properties and creep and damage associated with anisotropy of the creep response in off-axis orientations. Titanium, nickel and aluminum alloys used in fabricating engine components have been examined to assess their behavior under laboratory conditions designed to simulate fretting fatigue, in turbine engine blade attachments, foreign object damage, high-cycle fatigue, and high-cycle/low-cycle interactions under engine operation. The ability to predict turbine-engine-materials behavior under operating conditions is an important facet of the Engine Rotor Life Extension (ERLE) and Phase 1 DARPA Prognostics programs. Various studies have been undertaken to assess: (a) baseline properties for virgin material and material extracted from retired turbine disks, (b) fatigue crack initiation and growth, (c) the role that material defects play in low cycle fatigue crack initiation, (d) periodic overloads on fatigue crack growth behavior, (e) fatigue crack growth under near-threshold conditions, and (f) fracture surface marking for crack location during spin-pit testing. Studies that lead t
ADA404120
AASERT Student Research on In-Situ Toughened Alpha Prime-SiAlON
Personal Author(s): Chen, I-Wei
Report Date: 22 May 2002
Descriptors: (U) *TOUGHNESS, *CERAMIC MATERIALS, *OXYNITRIDES, *IN SITU ANALYSIS, MICROSTRUCTURE, PHASE TRANSFORMATIONS, NUCLEATION, ETCHING, IONIZATION, DOPING, KINETICS, RARE EARTH ELEMENTS, GRAIN GROWTH, SOLID SOLUTIONS, CRYSTAL GROWTH, CHEMICAL ENGINEERING, SILICON NITRIDES, ALKALINE EARTH METALS
Identifiers: (U) *ALPHA PRIME-SIALON, ALPHA PHASE, SIALON(SILICON ALUMINUM OXYGEN NITROGEN)
Abstract: (U) The grant was initiated on May 15,1998 and was completed in August 2001. We have explored the compositions at which in-situ toughened ct-SiAlON can be obtained. This essentially encompasses the entire single a-phase region. It includes both rare-earth ion-added compositions and alkali/alkali-earth ion-added compositions. We have made a systematic effort to obtain kinetic data on phase transformation at different compositions, since this knowledge is critically important for the precise control of nucleation and growth, which dictate the microstructure. We have developed methods for controlling microstructure in ci-SiAlON prepared from commercial a-Si3N4 powders. These materials have faster transformation rate and the microstructure control must rely on nucleation treatment of external seeding. We have developed the method to grow and harvest seed crystals, of a controlled composition, size and morphology, which can be used to nucleate a'-SiAlON grains in the ceramic to allow tailored grain growth. We have developed a theory for grain growth, based on the recent observations of the morphology of isolated grains from the oxynitride liquid. This model successfully predicted the novel shape transition observed experimentally. We have developed a wet chemical technique for etching the highly stable a'-SiAlON, which until now has proved difficult for ceraniographic preparation. We have shown that the mechanical strength of ct-SiAlON can exceed 1 CPa and the strength retention is good at least up to 1350 deg C. We have obtained R-curves for a'SiA1ON ceramics, and show that they can reach a toughness of 11-12 MPa m1t which compares favorably with the state-of-the-art Beta silicon nitride.
ADA402960
Structure and Properties of Aluminum Nitride and AlON Ceramics
Personal Author(s): McCauley, James W
Report Date: May 2002
Descriptors: (U) *CHEMICAL EQUILIBRIUM, *CRYSTAL CHEMISTRY, *ALUMINUM NITRIDES, MICROSTRUCTURE, CHEMICAL PROPERTIES, CERAMIC MATERIALS, ALUMINUM OXIDES, ANIONS, ION EXCHANGE, ALUMINATES, SPINEL, BINARY COMPOUNDS, OXYNITRIDES
Identifiers: (U) POLYTYPOIDS
Abstract: (U) A brief review of aluminum nitride and AlON ceramics is presented in the context of the pseudobinary aluminum nitride-aluminum oxide phase equilibrium system. AlON is the name applied to the nitrogen stabilized cubic spinel in this system, with a composition centered at 35.7 mole-percent AlN. First, the phase equilibria and crystal chemistry of these phases are presented, focusing on a constant anion oxynitride spinel model and the various phases, including polytypoids, in this system. Then, a brief summary is given on the processing and microstructures of AlN and AlON, with comparisons to other microstructures in this system. Finally, selected properties of AlN and AlON are discussed and tabulated, with special reference to alumina. A comprehensive reference list is given.
ADA410420
Thin Film Properties of POSS
Personal Author(s): Viers, Brent
Report Date: 24 Apr 2002
Descriptors: (U) *THIN FILMS, *ORGANIC MATERIALS, *INORGANIC MATERIALS, SYMPOSIA, POLYMERIZATION, CERAMIC MATERIALS, HYBRID SYSTEMS, OLIGOMERS, HYDROPHOBIC PROPERTIES, NANOTECHNOLOGY
Identifiers: (U) PRESENTATION SLIDES, VIEWGRAPHS ONLY, *POSS(POLYHEDRAL OLIGOMERIC SILSESQUIOXANE), LOW ABLATION MATERIALS, WUAFRL48470249549871
ADA410241
Hybrid Inorganic/Organic Reactive Polymers for Severe Environment Protection
Personal Author(s): Phillips, Shawn
Report Date: 12 Apr 2002
Descriptors: (U) *POLYMERS, *PROPULSION SYSTEMS, *SOLID PROPELLANTS, AIR FORCE, RISK, SURVIVABILITY, TECHNOLOGY TRANSFER, PROCESSING, CERAMIC MATERIALS, ENVIRONMENTAL PROTECTION, AIR FORCE OPERATIONS, NANOTECHNOLOGY
Identifiers: (U) VIEWGRAPHS ONLY
Abstract: (U) Significant advances in materials and processing technologies have made within AFRL/PRSM: demonstrated ceramic char layer of POSS-insulation, synthesized POSS-Kapton (up to 20 wt% POSS), demonstrated significant (9x) atomic oxygen survivability and formation of ceramic SiO2 layer. Basic (6.1) and Applications (6.2) research have been successfully integrated in Air Force Propulsion Programs: successful technology transfer of POSS nanotechnology, POSS nanotechnology on critical and high risk path for the Air Force.
ADA400094
Ceramic Nanocrystals
Personal Author(s): Alivisatos, A P
Report Date: 28 Feb 2002
Descriptors: (U) *SPECTROSCOPY, *SOFT X RAYS, CRYSTALS, CERAMIC MATERIALS, NANOSTRUCTURES
Identifiers: (U) *NANOCRYSTALS, SOFT XRAY IMAGING
Abstract: (U) We have shown that it is possible to prepare disposable nanocrystals of transition metal oxides in the absence of water or air by thermal decomposition of metal Cupferron complexes in hot surfactants. Preliminary experiments suggest that a similar level of size control as in the synthesis of semiconductor nanocrystals is possible. Since the precursor is available for many metal elements, this approach may present a rather general route to metal oxide nanocrystals. In another study resonant photoemission electron microscopy (PEEM) at the FeL absorption edge was utilized to image single gamma-Fe203 nanocrystals of 10 nm average diameter (approximately 20,000 Fe atoms) and to record soft x-ray absorption spectra of individual particles. Within the spectral resolution of the experiment, no damage to the individual nanoparticles occurs during repeated prolonged exposures to the intense x-ray beam. Furthermore, no differences in the x-ray absorption spectrum of a single nanocrystal are observed whereas PEEM contrast images and absorption spectra show strong intensity variations. This proof-of-principle experiment demonstrates the applicability of x-ray spectromicroscopy to the study of nanoscale systems on a hitherto unachieved length scale.
ADA410430
Molecularly Reinforced Polymers
Personal Author(s): Blanski, Rusty L, Haddad, Tim, Viers, Brent, Gonzalez, Rene, Moore, Brian
Report Date: 22 Feb 2002
Descriptors: (U) *OLIGOMERS, *ABLATIVE MATERIALS, SPACE TECHNOLOGY, SYMPOSIA, POLYMERS, HIGH TEMPERATURE, INSULATION, TOUGHNESS, CERAMIC MATERIALS, LIGHTWEIGHT, LIQUID PROPELLANT ROCKET ENGINES, AIRCRAFT CANOPIES, HYBRID SYSTEMS, MOLECULAR STRUCTURE, SILICON COMPOUNDS, RADOMES, PLASTICS, SOLID PROPELLANT ROCKET ENGINES, LUBRICANTS, CYCLIC COMPOUNDS, REINFORCED PLASTICS, NANOTECHNOLOGY
Identifiers: (U) *POSS(POLYHEDRAL OLIGOMERIC SILSESQUIOXANE), PRESENTATION SLIDES, VIEWGRAPHS ONLY, METAL PARTS REPLACEMENT, HIGH PERFORMANCE POLYMERS, SILSESQUIOXANE/POLYHEDRAL OLIGOMERIC, POLYMER WORKING GROUP, *REINFORCED POLYMERS, WUAFRL48470249549871
ADA403755
International Symposium on Self-Propagating High-Temperature Synthesis (SHS-2001) (6th) Held at Technion, Haifa, Israel on February 17-21, 2002. Book of Abstracts
Report Date: 21 Feb 2002
Descriptors: (U) *COMPOSITE MATERIALS, *ABSTRACTS, *CERAMIC MATERIALS, ISRAEL, MAGNETIC FIELDS, SYMPOSIA, SYNTHESIS, THERMODYNAMICS, POLYMERS, HIGH TEMPERATURE, EXPLOSIONS, ORGANOMETALLIC COMPOUNDS, ELECTRIC FIELDS, FULLERENES, GASES, INFILTRATION(FLUIDS), CHEMICAL REACTIONS, NITRIDING, CATALYSTS, HOT SPOTS, FLAME PROPAGATION, SOLID STATE CHEMISTRY, FERRITES, CASTINGS, THERMOELECTRICITY, DEFLAGRATION, NANOTECHNOLOGY, CARBON NANOTUBES, ALUMINUM NITRIDES, NANOSTRUCTURES
Identifiers: (U) *SHS(SELF PROPAGATING HIGH TEMPERATURE SYNTHESIS), FOREIGN REPORTS, THERMOLYSIS, METALORGANIC POLYMERS, THERMAL EXPLOSION, AUTOWAVE PROPAGATION, ETE(ELECTROTHERMAL EXPLOSION), GASLESS COMBUSTION, CONDENSED PHASE, MECHANICAL ALLOYING, TITANIUM NITRIDES
Abstract: (U) Partial contents: Nanocrystalline Ceramics by Solid State Thermolysis of Metalorganic Polymers; Trends in Ceramic Materials Development into the Third Millennium; SHS of Dense in situ Composites via Pressure Assisted Thermal Explosion: experiment and modeling; Forewood; Contaminants, Additives and Dopants in Modern Materials Science; Inorganic Nanotubes and Inorganic Fullerane-like Materials from Layered Compounds: synthesis, properties and applications; Kinetics and Thermodynamics of SHS Reactions; Mechanical Alloying in the SHS Research; SHS in Electric and Magnetic Fields; SHS-Produced Composite Materials; Critical Phenomena at Autowave Propagation; Dynamics of Hot spots in Solid Flame Propagation; Electrothermal Explosion (ETE) method to Study the Kinetics of Fast High Temperature Reactions in Condensed Systems; Mutual Interdependence, between SHS Reaction and Gas Infiltration, during Thermal Explosion; On Spinning Modes of Gasless Combustion; The Present Status and rends of SHS FGM; Reactive Castings of Ceramic Composites; SHS of Complex Ceramic Materials and their Properties; SHS TiB2 Based Multiphase Ceramics and Composites.
ADA453933
Model Development and Inverse Compensator Design for High Speed Nanopositioning
Personal Author(s): Smith, Ralph C, Salapaka, Murti V, Hatch, Andrew, Smith, Joshua, De, Tathagata
Report Date: Jan 2002
Descriptors: (U) *MATHEMATICAL MODELS, *MICROSCOPES, *COMPENSATORS, *HYSTERESIS, *PIEZOELECTRIC TRANSDUCERS, *NANOTECHNOLOGY, POSITION(LOCATION), SYMPOSIA, REAL TIME, CONTROL SIMULATORS, CONSTITUTIVE PROPERTIES, HIGH VELOCITY, ACCURACY, CERAMIC MATERIALS, NONLINEAR SYSTEMS, FEEDBACK, INVERSION, ACTUATORS
Identifiers: (U) *NANOPOSITIONING, *INVERSE COMPENSATORS, *ATOMIC FORCE MICROSCOPES, PIEZOCERAMIC ACTUATORS, PIEZOCERAMIC TRANSDUCERS, COMPONENT REPORTS
Abstract: (U) This paper focuses on the development of constitutive models, commensurate system models, and inverse compensator construction for high speed nanopositioning in atomic force microscopes (AFM). All current AFM employ either stacked or cylindrical piezoceramic actuators for both longitudinal and transverse positioning of the sample. An inherent property of these materials is the presence of hysteresis and constitutive nonlinearities, even at the low drive levels employed for angstrom-level resolution. At low frequencies, standard feedback mechanisms effectively attenuate the hysteresis, whereas noise at high frequencies diminishes the efficacy of feedback and leads to unacceptable accuracy. In this paper, we discuss modeling techniques which provide a first step toward high speed nanopositioning for applications ranging from macroscopic product evaluation to real-time imaging of biological processes.
ADA396874
Application of Bonded Multilayer Technology to Relaxor-Based Single Crystals for Imaging Transducer Applications
Personal Author(s): Zipparo, Michael J
Report Date: 26 Nov 2001
Descriptors: (U) *SINGLE CRYSTALS, *TRANSDUCERS, SCANNING ELECTRON MICROSCOPES, DIELECTRICS, CERAMIC MATERIALS, CRYSTAL DEFECTS, PIEZOELECTRIC MATERIALS, BANDWIDTH, INSERTION LOSS, FERROELECTRIC MATERIALS, POLYCRYSTALLINE
Identifiers: (U) IMAGING ARRAYS, MULTILAYERS
Abstract: (U) The objective of this program was to evaluate the performance of single crystal materials processed in the form of multilayer crystals and crystal-composites. These multilayers have been fabricated using a process originally developed for polycrystalline ceramic. All of the multilayers were found to function with the expected four- and nine-fold increase in the effective dielectric constant. The coupling was found to vary considerably between different multilayer sizes and between different array element samples diced from the same multilayers. SEM analysis of the multilayers and of bulk material found evidence of crystal defects which likely contributed to some degradation in performance. The crystal- and crystal-composite multilayers were found to be considerably better than similar multilayers fabricated with ceramic materials. The KLM model has been used to predict the performance of array elements. Using the measured properties for 2-layer crystals and 3-layer crystal-composites, very wide bandwidth (> 120%) and very good insertion loss (-18 dB) have been modeled. Because of the lower coupling measured for the crystal-composites, they did not show better bandwidth or sensitivity than the multilayer crystal. Improvements in crystal quality and a corresponding decrease in processing damage should improve the performance of multilayer crystal-composites, resulting in even better array performance.
ADA398431
Fabrication of PMN-PT Single Crystals by Using the Exaggerated Grain Growth Method
Personal Author(s): Kim, Doh-Yeon, Hwang, N M, Lee, Ho-Yong, Yoon, D Y, Kang, S J
Report Date: 23 Nov 2001
Descriptors: (U) *SINGLE CRYSTALS, *GRAIN GROWTH, MANUFACTURING, HEAT TREATMENT, CERAMIC MATERIALS, DIELECTRIC PROPERTIES, PIEZOELECTRICITY, SINTERING, POLYCRYSTALLINE
Abstract: (U) Polycrystalline 65 mole% Pb(Mg1/3Nb1/3)O3 -35 mole% PbTiO3 (PMN-PT) specimens were prepared by conventional and spark-plasma sintering. Conventional sintering at 1200 deg C produced 92% dense specimens, whereas spark-plasma sintering at 900 deg C produced 99% dense specimens. Addition of slight excesses of Mg accelerated grain growth, but additions of Nb retarded grain growth. In addition, excess Mg decreased dielectric and piezoelectric properties. Grain-growth studies indicated that abnormal grain growth (AGG) occurred when excess Pb was present. The AGG was ascribed to formation of sum 3 coincidence-site-lattice and low-angle grain boundaries. Because of reentrant edges appearing at the ends of these boundaries, grain-coarsening rates were significantly enhanced. However, single crystals could not be made by an AGG process.
ADA400386
International Conference on Silicon and Carbide and Related Materials 2001 (9th) (ICSCRM2001) Held in Tsukuba, Japan on October 28 - November 2, 2001. Technical Digest
Personal Author(s): Yoshida, Sadafumi
Report Date: Nov 2001
Descriptors: (U) *COMPOSITE MATERIALS, *SILICON CARBIDES, SYMPOSIA, SEMICONDUCTOR DEVICES, ION IMPLANTATION, JAPAN, NITRIDES, CRYSTAL DEFECTS, DOPING, PIN DIODES, CRYSTAL GROWTH, CARBON NANOTUBES
Identifiers: (U) FOREIGN REPORTS, AQ F02-07-1184, GROUP III-V COMPOUNDS, 4H-SIC, WIDE BANDGAP MATERIALS
Abstract: (U) The Technical Digest contains the abstracts of 506 papers presented at the International Conference on Silicon Carbide and Related Materials 2001 held on October 28-November 2 in Tsukuba, Japan. Topics include crystal growth, characterization, device process, and device modeling of wide bandgap materials such as silicon carbide, III-V nitrides and carbon nanotube.
ADA406351
Smart Materials Systems Through Mesoscale Patterning
Personal Author(s): Aksay, Ilhan A, Shih, W -H, Lee, P C Y, Prud'homme, R K, Whitesides, G M
Report Date: 01 Nov 2001
Descriptors: (U) *CERAMIC MATERIALS, *PIEZOELECTRIC MATERIALS, *PATTERNS, MATHEMATICAL MODELS, LINEAR SYSTEMS, CRYSTAL STRUCTURE, SYNTHESIS, COMPOSITE MATERIALS, SHOCK ABSORBERS, SHELLS(STRUCTURAL FORMS), LIQUID CRYSTALS, THREE DIMENSIONAL, FEASIBILITY STUDIES, ACTUATORS, INORGANIC MATERIALS, STEREOLITHOGRAPHY, MICROCONTACT PRINTING
Identifiers: (U) *SMART MATERIALS, INORGANIC COMPOSITES, ORGANIC COMPOSITES, PIEZOCOMPOSITES, SELF-ASSEMBLED MONOLAYERS, SHELL TRANDUCERS, MESOSCALE PATTERNING, NEGATIVE POISSON RATIO MATERIALS
Abstract: (U) This project emphasized the production of smart material systems using advanced 3-dimensional processing techniques. The specific aim was the fabrication and characterization of smart organic/inorganic composites at the mesoscale (^1 nm - 1 mm length scale) to achieve improved performance. Two approaches were used: (1) the synthesis and processing of organic/inorganic composites and (2) developing two novel materials systems. Synthesis and processing studies involve the use of three methods: (1) laser stereolithography, (2) self-assembled monolayers, and (3) 3-dimensional co-assembly. The two novel systems developed for use in sensor and actuator technologies were piezoelectric shell transducers and 1-3 piezocomposite hydrophones. This is the final technical report for the project, covering period 06/19/1995 - 05/31/2001. Proof of concept and feasibility studies have successfully demonstrated (1) the utility of rapid prototyping in the fabrication of ceramic structures for use in sensor and actuator applications; (2) the formation of mesostructured ceramics via templation of liquid crystal structures in solution; (3) guided growth and orientation in microcontact printing microinfiltration; and (4) optimization of piezo-composite properties through analytical modeling.
ADA407470
Polytype Distribution in Presolar SiC: Microstructural Characterization by Transmission Electron Microscopy
Personal Author(s): Daulton, T L, Lewis, R S, Amari, S
Report Date: 17 Oct 2001
Descriptors: (U) *CRYSTAL STRUCTURE, *SILICON CARBIDES, *INTERSTELLAR MATTER, MICROSTRUCTURE, DIAMONDS, ELECTRON MICROSCOPY, METEORITES, COSMIC DUST
Identifiers: (U) PRESOLAR GRAINS, PRESOLAR DUST
Abstract: (U) Presolar dust grains predate the formation of the solar system, originating from circumstellar outflows and supernova ejecta. The two most abundant forms of presolar grains isolated from primitive meteorites are nm-sized diamond and mm to submm-sized SiC. Both are ubiquitous in primitive chondritic meteorites at 300 - 1800 ppm (diamond) and 1 - 28 ppm (SiC). Silicon carbide is particularly interesting because it is known to form hundreds of different polytype structures and the formation of a particular polytype is sensitive to growth conditions. The first astronomical evidence of SiC in dusty envelopes of carbon stars came from a relatively broad 11.3 mm infrared (IR) feature. Later attempts to identify crystallographic structure of circumstellar SiC from IR spectra of carbon stars have generated controversy over the techniques and interpretation of the data. The outstanding question of polytype has bearing on physical conditions, such as temperatures and pressures. at which SIC condense from circumstellar outflows or supernova ejecta. Therefore, using transmission electron microscopy (TEM), we unambiguously determine the distribution of polytypes in presolar SiC grains, isolated by acid dissolution from the Murchison CM2 carbonaceous meteorite.
ADA395192
A New Method to Prepare Polycrystalline Meta-Thioboric Acid, (HBS2)3
Personal Author(s): Karthikeyan, Annamalai, Martindale, Chad A, Martin, Steve W
Report Date: 25 Sep 2001
Descriptors: (U) *GLASS, *CERAMIC MATERIALS, ELECTROCHEMISTRY, VAPOR PHASES, SULFUR, BORON, BROMIDES, RAMAN SPECTRA, ELECTRIC CONDUCTORS, POLYCRYSTALLINE, CHALCOGENS, THIOLS
Identifiers: (U) PROTONATED GLASSES, THIOBORIC ACIDS, FPC(FAST PROTON CONDUCTION), POLYCRYSTALLINE META-THIOBORIC ACID
Abstract: (U) Thioacids (ex: thioboric acid) are important precursors in exploring new chalcogenide ceramic and glassy materials. We report here a new facile method to prepare crystalline meta-thioboric acid (c-(HBS2)3). c-(HBS2)3 was prepared by reacting H2S with B2S3, in the vapor phase and the product was obtained as a vapor condensate. The technique is fairly simple and quick compared to the time consuming and wet routes of thiolysis of boron tribromide. The reaction takes place at much lower temperatures and in the vapor phase, thus achiveing higher purity.
ADA396955
Interphase Debonding in High Temperature Ceramic Composites
Descriptive Note: Final rept. 15 Jun 1996-14 Jun 1999
Personal Author(s): Marshall, David B, Davis, Janek B
Report Date: 13 Sep 2001
Descriptors: (U) *COMPOSITE MATERIALS, PLASTIC DEFORMATION, HIGH TEMPERATURE, CRACKING(FRACTURING), SINGLE CRYSTALS, STRAIN(MECHANICS), CERAMIC MATERIALS, OXIDES, BONDING, NONLINEAR ANALYSIS, RARE EARTH COMPOUNDS, EUTECTICS
Identifiers: (U) DEBONDING, LA-MONAZITE
Abstract: (U) Studies aimed at understanding the role of the interphase in providing a nonlinear response in oxide composites are described. Debonding and sliding of single crystal and eutectic oxide fibers coated with La-monazite caused intense plastic deformation of the LaPO4 at room temperature. Such plastic deformation mechanisms could be critical for preventing the development of very high stresses during constrained sliding of rough interfaces. A new class of machinable two-phase ceramics based on the debonding and deformation characteristics of rare-earth phosphates was demonstrated. Multilayered composites, consisting of various zirconia-based materials alternating with layers of LaPO4, were fabricated for studies of compatibility and debonding mechanisms.
ADA402433
Materials Development Research
Personal Author(s): Boakye, Emmanuel E, Hazzledine, Peter M, Keller, Kristin A, Kim, Young-Won, Mogilevsky, Pavel
Report Date: Sep 2001
Descriptors: (U) *ALUMINUM ALLOYS, *METAL MATRIX COMPOSITES, *FRACTURE(MECHANICS), *HEAT TREATMENT, MECHANICAL PROPERTIES, MICROSTRUCTURE, INTERFACES, PHYSICAL PROPERTIES, CERAMIC MATRIX COMPOSITES, FIBER REINFORCED COMPOSITES, VAPOR DEPOSITION, POINT DEFECTS, CHEMISTRY, COATINGS, CREEP, TITANIUM ALUMINIDE, PLASTIC PROPERTIES, REFRACTORY METALS, KINETICS, YIELD STRENGTH, OXIDATION RESISTANCE, GREENS FUNCTIONS, SILICIDES, ELECTRON MOBILITY, POLYCRYSTALLINE, NIOBIUM COMPOUNDS
Identifiers: (U) *NIOBIUM SILICIDE INTERMETALLICS, PHYSICAL VAPOR DEPOSITION, METALLIC MULTILAYERS, NANOCRYSTALLINE, PLANAR FAULT ENERGIES, OXIDE OXIDE COMPOSITES, INTERFACE COATINGS, AMORPHOUS ALUMINUM ALLOYS, COMPUTATION MATERIALS SCIENCE, DISCONTINUOUSLY REINFORCED METALLIC COMPOSITES, PE62102F, WUAFRL2306BO02
Abstract: (U) Research has been carried out in three materials systems: (1) Advanced Metallics: NbTi/silicides and gamma TiAl are being developed as high-temperature structural materials. The research included chemistry/processing/microstructure/property relations to provide a balance in mechanical properties and oxidation resistance. Fundamental studies on microstructures and mechanical behavior in these systems have been performed using a variety of analytical and computational tools to predict aspects of plasticity, creep and fracture on length scales connected to electronic, atomistic, and continuum levels. (2) Advanced Metallic Composites: Deformation, fracture, and creep studies have been performed on discontinuously reinforced Al and Ti composites. Projects have been initiated on 1) microstructural simulation in these composites, and 2) crystallization kinetics and topology-based models for amorphous Al alloys. (3) Ceramic Composites: Research has been conducted on a number of interrelated projects, including interface control, experimental mechanics and models, new composite systems, processing, and structure-property understanding.
ADA395517
Piezoelectric Ceramics Characterization
Personal Author(s): Jordan, T L , Ounaies, Z,
Report Date: Sep 2001
Descriptors: (U) *CERAMIC MATERIALS, *PIEZOELECTRIC MATERIALS, METHODOLOGY, POLYMERS, COMPOSITE MATERIALS, SINGLE CRYSTALS, PIEZOELECTRICITY, HYSTERESIS, INORGANIC MATERIALS, POLYCRYSTALLINE, FERROELECTRICITY, LEAD ZIRCONATE TITANATES
Identifiers: (U) *PIEZOELECTRIC CERAMICS, *PIEZOELECTRIC CHARACTERIZATION, CRYSTALLINE CERAMIC, PIEZOELECTRIC COEFFICIENTS, POLING
Abstract: (U) This review explores piezoelectric ceramics analysis and characterization. The focus is on polycrystalline ceramics; therefore, single crystals, polymeric materials and organic/inorganic composites are outside the scope of this review. To thoroughly grasp the behavior of a piezoelectric polycrystalline ceramic, a basic understanding of the ceramic itself should not be overlooked. To this end, we have presented a brief introduction of the history of piezoelectricity and a discussion on processing of the ceramic and development of the constitutive relations that define the behavior of a piezoelectric material. We have attempted to cover the most common measurement methods as well as introduce parameters of interest. Excellent sources for more in-depth coverage of specific topics can be found in the bibliography. In most cases, we refer to lead zirconate titanate (PZT) to illustrate some of the concepts since it is the most widely used and studied piezoelectric ceramic to date.
ADA394452
Deformation Mechanisms and Destruction of New Perspective Materials: Actual Problems of Strength
Report Date: 03 Jul 2001
Descriptors: (U) *MECHANICAL PROPERTIES, *DEFORMATION, *DESTRUCTION, THERMAL PROPERTIES, STRESS STRAIN RELATIONS, STRUCTURAL PROPERTIES, AMORPHOUS MATERIALS, ALLOYS, FRACTURE(MECHANICS), CERAMIC MATERIALS, HIGH STRENGTH, METAL COMPOUNDS, GRADIENTS
Identifiers: (U) FOREIGN REPORTS, AQ F01-12-2605, NANOCRYSTALLINE MATERIALS
Abstract: (U) The Final Proceedings for Deformation mechanisms and destruction of new perspective materials: Actual Problems of Strength, 2 July 2001 - 5 July 2001. Deformation and destruction mechanisms of new advanced materials: (1) ceramics; (2) nanocrystals; (3) amorphous metal alloys; (4) quasicrystals; (5) gradient and layered materials; (6) memory shape materials; (7) sintered materials; and (8) high specific strength materials.
ADA393567
A High Temperature Microhardness Tester for Structural Ceramics
Personal Author(s): Chen, I-Wei
Report Date: Jul 2001
Descriptors: (U) *CERAMIC MATERIALS, MECHANICAL PROPERTIES, HIGH TEMPERATURE, ELASTIC PROPERTIES, INSTRUMENTATION, PLASTIC PROPERTIES, SILICON NITRIDES, MICROHARDNESS, NANOTECHNOLOGY
Identifiers: (U) DURIP GRANT, SIALON, PE61103D, WUAFRL3484US
Abstract: (U) The grant was initiated on May 1, 1999. In view of the fact that high temperature microindentation testers are no longer in commercial production, we have instead designed, purchased and received an atomic force microscope (AFM) from Digital Instrument. This instrument is configured to perform nanoindentation tests to obtain information on deformation resistance in both elastic and plastic range. The instrument was installed in September 1999 and personnel have been trained to operate the instrument at the same time. We have proceeded with nanomechanical characterization of the bulk silicon nitride and SiAlON's and their interfacial properties. This includes a study of the intergranular glassy phase that is often thought to be a critical factor in determining their mechanical performance.
ADA410607
The Preparation and Properties of Polymer/Nanoparticle Blends Using POSS (TM)
Personal Author(s): Blanski, Rusty L, Phillips, Shawn H, Lee, Andre Y
Report Date: 11 Jun 2001
Descriptors: (U) *BLENDING, *POLYMERS, *CERAMIC MATERIALS, COMPOSITE MATERIALS, POLYSTYRENE, SYNTHESIS(CHEMISTRY), STYRENE PLASTICS, RUBBER, POLYPROPYLENE, ORGANIC MATERIALS, MONOMERS, POLYCARBONATES, POLYESTER PLASTICS, POLYETHYLENE, VINYL PLASTICS, CYCLOPENTANES, NANOTECHNOLOGY
Identifiers: (U) *POSS(POLYHEDRAL OLIGOMERIC SILSESQUIOXANES), CROSS METATHESIS TECHNOLOGY, PHENETHYL 8T8, NANOPARTICLES, WUAFRL2303M1A3346127
Abstract: (U) The synthesis of nanoparticle/polymer blends has expanded greatly in recent years. When the nanoparticles are ceramic, these blend materials have the advantage of combining a ceramic-type material with an organic polymer that can result in a material that may bridge the performance gap between the two systems. The Air Force Research Laboratory in collaboration with Michigan State University has been working with Polyhedral Oligomeric Silsesquioxanes (POSS) to enhance the performance characteristics of polymers. One aspect of this program is the preparation of POSS (TM)/polymer materials using traditional blending techniques. The authors have shown that simply changing the organic functionality around the POSS (TM) molecule can lead to POSS (TM) dispersion in a wide array of polymers, including polyethylene, polypropylene, polystyrene, polycarbonate, SB rubber, and many other polymers. In several cases the authors have been able to maintain clarity of the polymer after dispersion. By altering the organic side groups of POSS (TM) compounds to more compatible groups, one can fully disperse the POSS (TM) molecules into high molecular weight polystyrene and, in the case of StyrenylPOSS (TM)/polystyrene film, an increase of 30% in the surface hardness is observed. Future work will focus on the use of POSS (TM) as a flame retardant. While vinyl 8T8 is not miscible in polystyrene, a partially functionalized vinyl 8T8 with aromatic groups should be. The concept of partial cross metathesis with vinyl 8T8 and styrene has been proven, and future work will focus on blends of these POSS (TM) compounds. Another possibility is the use of vinyl nTn as a reactive blendable with resins. (1 table, 6 figures, 4 refs.)
ADA399050
Ionically Conducting Polymer Electrolytes
Personal Author(s): Kumar, Bindo
Report Date: Jun 2001
Descriptors: (U) *POLYMERS, *CERAMIC MATERIALS, *DIPOLES, *LITHIUM BATTERIES, *ELECTROLYTES, ANNEALING, OPTIMIZATION, CONDUCTIVITY, INTERACTIONS, PARAMETERS, COMPOSITE MATERIALS, RESISTANCE, MATRIX MATERIALS, CRYSTALLIZATION, PARTICLES, CHAINS, ADDITIVES, RELAXATION, COMPOSITION(PROPERTY), MELTING POINT, POLYETHYLENE, ETHYLENE OXIDE
Identifiers: (U) *IONIC CONDUCTIVITY, CERAMIC ADDITIVES, DIPOLE-DIPOLE INTERACTION, PE61102F, WUAFRL2303P400
Abstract: (U) This report presents an investigation on the development of composite electrolytes for lithium batteries. The investigation covers a diverse range of composite electrolyte compositions and reveals that the incorporation of a ceramic component in a polymer matrix leads to enhanced conductivity. The conductivity enhancement depends upon the weight fraction of the ceramic phase, annealing parameters, nature of polymer-ceramic system, and temperature. The roles of ceramic additives are to depress the poly(ethylene oxide) (PEO) melting temperature and retard kinetics of its crystallization. A resistivity relaxation or conductivity enhancement below the melting temperature of PEO occurs, which appears to be a characteristic of these electrolytes and related to an interaction of dipoles associated with polymer chain and ceramic particles.
ADA418122
Acquisition of Single and Double Crystal X-Ray Topography System
Personal Author(s): Skowronski, M
Report Date: Jun 2001
Descriptors: (U) *SEMICONDUCTORS, *X RAYS, *CRYSTAL DEFECTS, *SILICON CARBIDES, *CRYSTAL GROWTH, *DEFECT ANALYSIS, PLASTIC DEFORMATION, DEGRADATION, STRUCTURAL PROPERTIES, VAPOR DEPOSITION, SEMICONDUCTOR DIODES, NUCLEATION, DISLOCATIONS, FAULTS, GALLIUM NITRIDES
Identifiers: (U) STACKING FAULTS, *PHYSICAL VAPOR TRANSPORT, *X RAY TOPOGRAPHY, PE61103D
Abstract: (U) The Durip Award was used to purchase two pieces of instrumentation in support of one overreaching goal of the AFOSR-funded program: correlation of growth conditions of silicon carbide boules and their structural characteristics. The x-ray topography unit was ordered in September of 2000 and manufactured and delivered to Carnegie Mellon University in January of 2001. The installation was completed in March 2001 and was followed by extensive alignment and testing. The system is producing valuable data for several federally funded projects, including "Growth of Semi-insulating 6H-SiC Crystals for GaN-based Microwave Devices," funded by the Air Force Research Laboratory (AFRL); "Structural Defects in Semi-insulating SiC Wafers," funded by the Air Force Office of Scientific Research; "High Volume, High Quality Silicon Carbide Substrate Merchant Manufacturing," a subcontract to Sterling Semiconductor, Inc. from the AFRL; and "Identification of Screw Dislocation Sources in SiC PVT Growth," funded by the Office of Naval Research. The system is intensively used for imaging extended defects in silicon carbide crystals grown by the Physical Vapor Transport method and in silicon carbide high-voltage diodes. Among the major findings accomplished with the help of x-ray topography are as follows: evidence of plastic deformation occurring during crystal growth of SiC boules, which causes the dislocation multiplication and resulting densities in the 10 (super 5) sq cm range; evidence of dislocation serving as nucleation sites for stacking faults under forward bias, which leads to the degradation of SiC bipolar devices through the increase of forward voltage drop (both the stacking faults and pre-existing dislocations have been imaged using x-ray topography); and evidence of stacking faults formation during the initial stages of SiC growth leading to nucleation of screw dislocations.
ADA389184
Fabrication and Characterization of Photoconductive AlGaN Detectors/Structural Characterization of SiC Wafers
Personal Author(s): Skowronski, Marek
Report Date: 22 Feb 2001
Pagination Code: 2
Descriptors: (U) *WAFERS, *SILICON CARBIDES, X RAY DIFFRACTION, VOIDS, CRYSTAL DEFECTS, GRAIN BOUNDARIES
Identifiers: (U) MICROPIPES
Abstract: (U) Structure of silicon carbide wafers have been evaluated by x-ray topography, high resolution x-ray diffraction, etching, Atomic Force Microscopy, and related techniques. The low angle grain boundaries were imaged by White Beam Synchrotron X-Ray Topography and mis-orientations quantitatively mapped out by x-ray diffraction. The dominant component of mis-orientation was basal plane tilt. The formation mechanism is most likely due to buckling of the rigidly mounted SiC seed during initial stages of growth. The morphology of hexagonal voids was studied by optical microscopy and AFM. Voids originate at the seed crystal/crucible lid interface and move through the boule during growth. Interaction of void and grown in dislocations leads to formation of dislocation arrays and open core screw dislocations underneath the void. It appears to be the dominant formation mechanism of micropipes.
ADA388439
Waves and Vibrations in Electroplated Piezoelectric Plates and Substrate Systems
Personal Author(s): Lee, Peter C
Report Date: 09 Feb 2001
Pagination Code: 2
Descriptors: (U) *VIBRATION, *PIEZOELECTRIC MATERIALS, *WAVES, SHEAR PROPERTIES, FREQUENCY, THICKNESS, EXPERIMENTAL DATA, CRYSTAL STRUCTURE, PREDICTIONS, COMPARISON, ACCURACY, SUBSTRATES, CERAMIC MATERIALS, SPECTRA, PLATES, SYMMETRY, RECTANGULAR BODIES, DISKS, EQUATIONS, FLEXURAL PROPERTIES, CIRCULAR, CORRECTIONS, CAPACITANCE, TRUNCATION, DISPERSION RELATIONS, ELECTROPLATING
Abstract: (U) In the present research, a new, infinite system of plate equations is obtained. They are applicable to piezoelectric plates of any crystal symmetry and requiring no correction factors. Firstly, a system of first-order plate equations is extracted from the infinite system, and they are employed to study the thickness shear and flexure vibrations of rectangular plates of AT- and SC-cuts of quartz and are shown to give accurate predictions in dispersion relations, frequency spectra, and capacitances without any corrections. Secondly, a system of second-order plate equations is extracted from the infinite system by a new truncation procedure, and these equations are employed to study the thickness-stretch, symmetric thickness-shear, and extensional vibrations of finite strips and circular disks of ceramics. The accuracy of the prediction is validated by the close comparison with experimental data, without any correction.
ADA387272
Fire Blankets for Munition Protection: Flame and Heat Blocking Properties of Advanced Materials
Personal Author(s): Tewarson, Archibald, Wu, Peter K, Chin, Wai K, Shuford, Richard
Report Date: Feb 2001
Pagination Code: 2
Descriptors: (U) *AMMUNITION, *FIRE RESISTANT MATERIALS, *BLANKETS, MILITARY FACILITIES, ARMY RESEARCH, EXPOSURE(GENERAL), SILICON DIOXIDE, HIGH TEMPERATURE, ORGANIC MATERIALS, THERMAL CONDUCTIVITY, ACETYLENE, FIRE PROTECTION, BLOCKING, FLAMES, CERAMIC FIBERS, DIFFUSIVITY, INORGANIC MATERIALS, CHARRING
Identifiers: (U) *FLAME RESISTANT BLANKET, STORED AMMUNITION, FLAME PENETRATION, EFFECTIVE THERMAL DIFFUSIVITY, INORGANIC/ORGANIC FIBERS, HEAT PENETRATION, MUNITION PROTECTION
Abstract: (U) This report examines the flame and heat penetration through layers of fabrics as blankets for thermally protecting stored munitions. Evaluated were 27 fabrics made of inorganic fibers (alumina, silica, and ceramic fibers) and organic fibers (Kevlar, Nomex, and carbon) varying in thickness from 3 to 25 mm. Two types of tests were performed. First, flame penetration tests were performed with an oxyacetylene flame. Visual observations and measured char depth into a wooden block at the back of the sample were used in the analysis. Second, heat penetration tests were performed in the heat penetration apparatus. A radiant heater was used for heat exposure. Temperatures were measured at the front and back surfaces of the inorganic fabrics and in each layer of the Kevlar fabric. The average steady-state temperatures were used for the analysis. Effective thermal diffusivity values for the sample "blankets" were estimated from the measured temperatures, sample thickness, and exposure duration using a simple heat conduction relationship for thermally thick materials. A procedure was developed to obtain effective thermal diffusivity of the sample "blankets" from the measured average steady-state temperatures at the front and back surfaces, thickness, and exposure time duration. This procedure, along with measurements in the heat penetration apparatus, can be used for routinely testing the various types and combinations of inorganic and organic fiber-based fabrics.
ADA386679
Deposition of Ceramic Coatings by the Changed Liquid Beam Cluster Technique
Personal Author(s):Kriven, Waltraud M
Report Date: 10 Jan 2001
Descriptors: (U) *CERAMIC COATINGS, PHASE TRANSFORMATIONS, SYNTHESIS(CHEMISTRY), ELASTIC PROPERTIES, AMORPHOUS MATERIALS, CRYSTALLIZATION, DEPOSITION, CLUSTERING, OXIDES, ALUMINUM OXIDES, ELECTROPHORESIS, ZIRCONIUM OXIDES, MICROCRACKING
Identifiers: (U) LIQUID BEAM CLUSTER TECHNIQUE, AASERT 97 GRANT, STTR
Abstract: (U) The original aim of this work was to develop a viable, on line, coating technique for oxide fibers and weaves. The coating was to be a chemically compatible, oxide (eg. hexacelsian Ba Al(2) 2SiO(8) which provided' a temperature-independent, debonding mechanism based on residual stresses developed at l59O degrees centigrade, due to a reconstructive phase transformation accompanied by a 5.6% volume contraction. However, the method adopted, the charged liquid beam cluster technique proved to be unfeasible at the current time. Attention was therefore focused onto electrophoretic deposition of oxide sols (alumina, zirconia) onto carbon-coated fibers and weaves of alumina and mullite 3Al(2)O(3).2SiO(2). However drying of films led to extensive microcracking and this method too, was found to be unsuitable. Attention was then turned to support related AFOSR work for which intermittent funding was obtained (STTR stages I and II); viz., (1) the development of mullite and YAG fibers by amorphous crystallization from a frozen, amorphous melt; (2) the elastic constants of single crystal, mullite and yttria fibers as measured by Brillouin spectroscopy to 1200 degrees centigrade; and (3) powder synthesis of oxides for matrices or deposition as coatings.
ADA386724
Templated Grain Growth of Single Crystal-Like Electroceramics
Personal Author(s): Messing, Gary L, Trolier-McKinstry, Susan
Report Date: Jan 2001
Descriptors: (U) *SINGLE CRYSTALS, *TEMPLATES, *GRAIN GROWTH, MEASUREMENT, FIBERS, POLARIZATION, POWDERS, HIGH TEMPERATURE, X RAY DIFFRACTION, ORIENTATION(DIRECTION), BLADES, ALIGNMENT, MICROSCOPY, CERAMIC MATERIALS, DIELECTRIC PROPERTIES, PARTICLES, ANISOTROPY, PIEZOELECTRIC MATERIALS, BIAXIAL STRESSES, TEXTURE, SINTERING, BISMUTH TITANATE, NANOTECHNOLOGY
Identifiers: (U) *ELECTROCERAMICS, PIEZOELECTRIC CERAMICS, BIAXIALLY TEXTURED, SN(STRONTIUM NIOBATE), TAPE CASTING, TGG(TEMPLATED GRAIN GROWTH) TECHNIQUE
Abstract: (U) Fiber textured bismuth titanate (Bi4Ti3O12) (BIT) and biaxially textured La-doped Sr2Nb2O7 (SN) were produced by templated grain growth. Platelets of BIT and blade-shaped SN template particles were dispersed in a matrix of nanosize BIT and fine SN powders, respectively. and aligned by tape casting. As determined by x-ray diffraction and microscopy. the sintered ceramics were >90% textured. Growth of the template particles depends critically on the presence of a liquid during growth and maintaining a template to matrix grain size ratio >2. Textured Nb-doped bismuth titanate ceramics (Bi4Ti(3-x/5)Nb(x/5)O12. where x=0.02) showed anisotropic dielectric and piezoelectric properties when measured parallel and perpendicular to the texture axes with the remanent polarization differing by more than a factor of 15 in the two directions. The piezoelectric constant in the grain-axis was 30 pC/N. or ^77% of the single crystal value. High temperature piezo, doped bismuth titanate. A gated doctor blade was developed to achieve biaxial alignment of the blade-shaped Sr2Nb2O7 template particles. Very good orientation was achieved perpendicular to the major blade axis In addition, X-ray diffraction measurements of the 131 pole revealed that the Sr2Nb2O7 was biaxially textured and had a full width at half maximum of the peak height of 30 deg in the orientation distribution in the plane of the blades.
ADA386884
In Situ Monitoring and Characterization of Superhard Thin-Film Growth Under Non-Equilibrium Conditions
Personal Author(s): Tsong, I S, Kouvetakis, J, Chason, E
Report Date: 29 Dec 2000
Descriptors: (U) *THIN FILMS, *CHEMICAL VAPOR DEPOSITION, REAL TIME, SUBSTRATES, BORON, SILICON CARBIDES, CRYSTAL GROWTH, SILICON NITRIDES, PHOSPHORUS COMPOUNDS, GALLIUM NITRIDES, IN SITU ANALYSIS
Identifiers: (U) *XRR(X RAY REFLECTIVITY), *MOSS(MULTIPLE BEAM OPTICAL STRESS SENSORS), SUPERHARDNESS, CNP(CARBON NITROGEN PHOSPHORUS)
Abstract: (U) We have developed new approaches to synthesize superhard/ultrastrong thin films and coatings by chemical vapor deposition (CVD) of unimolecular precursors, and to monitor and characterize the film-growth process in situ and in real time. To this end, we have designed and constructed an ultrahigh vacuum CVD chamber fitted with energy-dispersive x-ray reflectivity (XRR) and multiple- beam optical stress sensor (MOSS) for in situ monitoring of surface morphology and stress evolution of the films under growth. Both of these techniques were applied to the CVD growth of boron and GaN films. We have synthesized novel precursors of C3N3P, Si4CN4, LiBC4N4, BC3N3, BeC2N2, MgC2N2 for CVD growth of films with properties of superhardness. We have also deposited thin films by CVD with the composition of Zr-B-Si-N via reactions of Zr(BH4)4 with SiH4, and Zr(BH4)4 with N(SiH3)4. The elastic constants cli and c44 of these films measured by Brillouin scattering in collaboration with Prof. Sooryakumar of Ohio State University produced results suggesting that films and coatings based on the Zr-B-Si-N system exhibit promising superhard properties.
ADA386801
Material Strength and Inelastic Deformation Mechanisms in Shocked Ceramics
Personal Author(s): Gupta, Yogendra M
Report Date: 28 Dec 2000
Descriptors: (U) *STRENGTH(MECHANICS), *CERAMIC MATERIALS, SHEAR PROPERTIES, LOADS(FORCES), SHOCK WAVES, ELASTIC PROPERTIES, NONLINEAR SYSTEMS, WAVE PROPAGATION, SILICON CARBIDES, POLYCRYSTALLINE, COMPRESSION WAVES
Abstract: (U) The objectives of this project were to quantify the strength of shocked ceramics during uniaxial strain and to understand the mechanisms that govern shock wave induced inelastic deformation. Dense, polycrystalline silicon carbide (SiC) was selected for this study and two independent measurement techniques (lateral and longitudinal stress determination using in-material piezoresistance gauges; and combined compression and shear wave propagation) were used to examine the shocked state. Nonlinear elastic response below the Hugoniot Elastic Limit (11.5 GPa) was quantified. In the shocked state, the maximum shear stress increases from 4.5 GPa at the HEL to 7.0 GPa at twice the HEL. The inelastic deformation was interpreted as a combination of in-grain micro-plasticity and highly confined micro-fissures. The results suggest that confinement stress, inherent in shock wave loading, plays a dominant role.
ADA385216
First-Principles Theory of Transition Metal Impurities in Silicon Carbide
Personal Author(s): Lambrecht, Walter R
Report Date: 14 Dec 2000
Descriptors: (U) *TRANSITION METALS, *QUANTUM THEORY, *IMPURITIES, *SILICON CARBIDES, ELECTRONICS, SEMICONDUCTOR DEVICES, POINT DEFECTS, CRYSTALLOGRAPHY, SPIN STATES
Identifiers: (U) FIRST PRINCIPLES THEORY, ELECTRONIC STRUCTURE
Abstract: (U) A theoretical study of the electronic structure of selected transition metal impurities in silicon carbide is carried out using a first-principles approach. Polytype dependence, site preference and charge and spin states are investigated.
ADA386028
Novel Nanostructure Fabrication and Their Characterization by STM and AFM
Personal Author(s): Sarid, Dror
Report Date: 28 Nov 2000
Descriptors: (U) *FABRICATION, *NANOSTRUCTURES, FIELD EMISSION, MICROELECTRONICS, SILICON CARBIDES, NANOTECHNOLOGY
Identifiers: (U) SCANNING PROBE MICROSCOPY, FOWLER-NORDHEIM FIELD EMISSION, STM(SCANNING TUNNELING MICROSCOPY), AFM(ATOMIC FORCE MICROSCOPY)
Abstract: (U) The enclosed list of 12 publications contain papers on Silicon Carbide, Scanning Probe Microscopy, Fowler-Nordheim Field Emission, and Nanofabrication that were made possible by this grant.
ADA384285
Finishing of Advanced Ceramics
Personal Author(s): Komanduri, Ranga
Report Date: 30 Oct 2000
Descriptors: (U) *CERAMIC MATERIALS, *FINISHES, REMOVAL, MECHANICAL ENGINEERING, BEARINGS, SILICON NITRIDES, POLISHING, MECHANICAL WORKING
Identifiers: (U) CERAMIC BALLS, MFP(MAGNETIC FLOAT POLISHING), HYBRID BEARINGS, CMP(CHEMO-MECHANICAL POLISHING)
Abstract: (U) This project deals with both fundamental and applied aspects of finishing of advanced ceramics, such as silicon nitride (Si3N4) balls for hybrid bearing applications using the magnetic float polishing (MFP) technology developed under DARPA's Ceramic Bearing Technology Program (CF 33615-92-C-5933). On the fundamental side, an understanding of the material removal mechanisms involving both mechanical and chemo-mechanical polishing (CMP) as well as thermal aspects of polishing were considered. improvements in the quality of the finished balls in terms of surface finish (Ra 5 nm) and sphericity (0.15-0.25 mm) and the development of prototype equipment for increasing the batch size by almost an order of magnitude (i.e. from about 10 balls of 12 mm diameter per batch with the small apparatus to about 80 balls per batch with a large apparatus) for polishing were investigated on the technology side. The processing time for finishing a batch of balls was about 20 hours.
ADA384298
Quiet, Clean, Multi-fueled, Multi-kilowatt Thermophotovoltaic Generator
Personal Author(s): Seal, Michael
Report Date: 20 Oct 2000
Descriptors: (U) *THERMAL PROPERTIES, *GENERATORS, *PHOTOVOLTAIC EFFECT, HIGH TEMPERATURE, COMBUSTION, SPECTRA, OXIDATION, TUNGSTEN, SEALED SYSTEMS, RHODIUM, GALLIUM ANTIMONIDES, EXHAUST GASES, RUBIDIUM, WATER COOLING, OPTICAL FILTERS, SWITCHES, SILICON CARBIDES, NITROGEN OXIDES, TEMPERATURE CONTROL, CIRCUITS, CARBON MONOXIDE, NOISE REDUCTION
Identifiers: (U) *THERMOPHOTOVOLTAIC CELL, STANDALONE GENERATOR, POWER TO WEIGHT RATIO, METAL RECUPERATORS, COGENERATION, JX CRYSTALS, THERMAL MANAGEMENT
Abstract: (U) A stand-alone generator that is capable of producing one kWatt was developed during the contract period. Power to weight ratio has been improved from 10 Watts/K to 50 Watts/K. Exhaust emissions are less than 1 PPM HC and 300 PPM CO. NOx emissions are still high but a Rhodium or Rubidium flash coating on the metal recuperator surface should get below the 15 PPM target. The automated start up and run program works well and allows one switch operation. Water cooling and noise suppression were achieved early in the program and cooling efficiency has been dramatically improved. Efficiency has been improved from marginal net power output to an efficiency of 7%. System modeling development has allowed pinpointing areas of efficiency loss and allows rapid optimization of cells and optical cavity. Work with matched emitters and improved recuperators have brought about improved combustion efficiency. Work on Tungsten coated matched emitters have begun although it appears that a hermetically sealed emitter must be used to prevent rapid oxidation of the metal. Shingle cell circuits have been designed manufactured and tested.
ADA389451
Silicon Carbide and Related Materials: ECSCRM2000
Descriptive Note: Conference proceedings
Personal Author(s): Pensl, G, Stephani, D, Hundhausen, M
Report Date: Sep 2000
Pagination Code: 2
Descriptors: (U) *SYMPOSIA, *SEMICONDUCTORS, *SILICON CARBIDES, THERMAL PROPERTIES, ELECTROMAGNETIC PROPERTIES, EPITAXIAL GROWTH, CRYSTALS, NITRIDES, BROADBAND, GERMANY
Abstract: (U) The Third European Conference on Silicon Carbide and Related Materials (ECSCRM2000), held September 3-7, 2000 in Kloster Banz, Germany, developed into a truly important forum in the field of wide bandgap semiconductors. All continents - some 320 participants from 21 different countries - were represented and 15 exhibitors maintained booths and demonstrated the increasingly industrial interest in and the economic impact of the wide bandgap semiconductors. Scientists from Universities and Industry discussed the exciting progress in the fields of SiC and III-Nitrides. Many young scientists have been among the participants; they are regarded as the guarantee to successfully solve the forthcoming tasks. These proceedings reveal the present experimental and theoretical knowledge on the growth of bulk crystals and epitaxial layers, the mechanical, thermal and electronic properties of the grown material, the development of suitable processes and electronic devices, which will have a profound effect on society's ability to better utilize its strategic resources in the future.
ADA380708
Innovative Acoustic Techniques for Studying New Materials and New Developments in Condensed Matter Physics
Personal Author(s): Maynard, Julian D
Report Date: 15 Jul 2000
Descriptors: (U) *CERAMIC MATERIALS, *ACOUSTICS, *HIGH TEMPERATURE SUPERCONDUCTORS, THIN FILMS, CRYSTALS, FRACTURE(MECHANICS), INFRARED OPTICAL MATERIALS, SOLID STATE PHYSICS
Identifiers: (U) *RESONANT ULTRASOUND SPECTROSCOPY, PE61153N
Abstract: (U) This project involved the use of innovative acoustic techniques to study new materials and new developments in solid state physics. Major accomplishments include a) the preparation and publication of a number of papers, book chapters, and invited lectures, b) the measurement and analysis of an aluminum alloy quasicrystal and its cubic approximant, c) the use of resonant ultrasound to measure acoustic attenuation and determine the effects of heat treatment on ceramics, d) the extension of our technique for measuring even lower (possibly the lowest) infrared optical absorption coefficient, and e) the measurement of the effects of disorder on the propagation of a nonlinear pulse, and f) the observation of statistical effects in measurements of individual bond breaking events in fracture.
ADA396601
Report on International Conference on "Innovative/Cost-Effective Materials Processing Methods - Films and Nanocrystalline Powders
Report Date: 07 Jul 2000
Descriptors: (U) *CERAMIC MATERIALS, *COATINGS, COST EFFECTIVENESS, STRUCTURAL PROPERTIES, POWDERS, FILMS, FABRICATION
Identifiers: (U) INNOVATIVE, MATERIALS PROCESSING METHODS, NANOCRYSTALLINE POWDERS, PROCESS-STRUCTURE-PROPERTY-RELATIONSHIPS, F02-03-0271
Abstract: (U) On 6 July 2000, Dr. K. L. Choy welcomed over 35 delegates from 10 countries including UK, USA, France, Germany, Switzerland, Denmark, Poland, the Netherlands, Russia, Spain to ICMPM conference at Imperial College. The venue was held at the Dept. of Materials in the Royal School of Mines. This was followed by an official welcome addressed by the Dean of the Royal School of Mines, Prof. John Kilner. As the use of advanced engineering ceramic films and powders for structural and functional applications is expanding rapidly. Improved materials and innovative methods of fabrication are needed to enhance the engineering performance and reduce the production costs. Therefore the aim of the ICMPM conference was to bring together international engineer and material scientists concerned with the innovative/cost-effective materials processing methods, at a mature production stage and also in development. Issues and strategies associated with scaling-up were also highlighted. Modelling of deposition techniques and properties were also presented. Advanced on-line/in-situ process monitoring techniques were reported by several speakers. Ten invited papers and seven posters covering a wide variety of novel and/or cost effective synthesis of nanoparticles, films and their applications were presented and discussed. The poster session had facilitated informal discussions between the authors and conference delegates.
ADA382090
High Temperature Micromechanics and Mechanisms of Damage and Failure in Advanced Ceramic-Matrix Composites
Personal Author(s): Wang, S S
Report Date: 28 Jun 2000
Descriptors: (U) *DAMAGE, *HIGH TEMPERATURE, *CERAMIC MATRIX COMPOSITES, *FAILURE(MECHANICS), *MICROMECHANICS, THERMOMECHANICS, STABILITY, MICROSTRUCTURE, AGING(MATERIALS), DEGRADATION, REACTION KINETICS, POLYMERS, DEFORMATION, ELASTIC PROPERTIES, JET ENGINES, FRACTURE(MECHANICS), CRACK PROPAGATION, OXIDATION, THERMOCHEMISTRY, CREEP
Abstract: (U) In this project, research efforts have been made to address some of the most critical and complex issues on high-temperature damage, degradation and failure of advanced composites. For the convenience of program planning and execution, the research as been formulated in the form of several interrelated technical tasks with distinct focuses. In the study of high-temperature ceramic-matrix the following tasks have been conducted: (1) High-temperature fiber/matrix interface properties and failure mechanics; (2) High-temperature micromechanics theories for thermoelastic constitutive equations for whisker-reinforced ceramic composites with large temperature traverse; (3) High-temperature creep deformation and micromechanics modeling of inelastic composite constitutive properties with composite microstructure and damage, and (4) High-temperature toughening mechanisms, and mechanics of crack growth fracture. For the high-temperature polymer-matrix composite study, the following thermomechanics issues with internal and external damage have been addressed: (1) thermal oxidation reaction and stability at elevated temperatures; (2) chemical and physical aging in extreme thermal environments; (3) microstructure changes and property degradation associated with aging at elevated temperatures; and (4) long-term thermomechanical creep and associated damage modes.
ADA381274
Acoustic Transduction Materials and Devices - Volume 1
Personal Author(s): Uchino, Kenji
Report Date: 12 Jun 2000
Descriptors: (U) *POLYMERS, *CERAMIC MATERIALS, *PIEZOELECTRIC TRANSDUCERS, COMPOSITE STRUCTURES, SINGLE CRYSTALS, ACTUATORS, FERROELECTRIC MATERIALS, ELECTROSTRICTION
Identifiers: (U) HIGH STRAIN POLYMERS, PHOTOSTRICTION
Abstract: (U) A primary objective of this MURI grouping was to help shorten the time constant for new materials and device concepts to be applied in practical Navy Systems. We believe this has now been realized in joint work on the composite cymbal type flextensional arrays for large area projectors, and in the progress made towards a micro-tonpilz array system. Original work on new step and repeat piezoelectric high strain systems continues to make good progress now using commercial motion rectifiers to produce both linear and rotary systems with high torque capability. New composite designs are pushing toward 1 mm diameter motors in the size regimen where there are real difficulties for conventional electromagnetic designs. A new area of activity this year is in piezoelectric transformers where a circular symmetry design in conjunction with controlled inhomogeneous poling is shown to offer capabilities which are of real interest for energy recovery actuator power systems. Basic studies have evolved a new environmental SEM technique for high resolution domain wall studies without changing problems. Work is continuing on reliable measurements of electrostrictive constants in simple solids confirming by both direct and converse methods and permitting the first generalization of trends in these fundamentally important coupling constants.
ADA381271
Acoustic Transduction Materials and Devices - Volume 3
Personal Author(s): Uchino, Kenji
Report Date: 12 Jun 2000
Descriptors: (U) *POLYMERS, *CERAMIC MATERIALS, *PIEZOELECTRIC TRANSDUCERS, COMPOSITE STRUCTURES, SINGLE CRYSTALS, ACTUATORS, FERROELECTRIC MATERIALS, ELECTROSTRICTION
Identifiers: (U) HIGH STRAIN POLYMERS, PHOTOSTRICTION
Abstract: (U) A primary objective of this MURI grouping was to help shorten the time constant for new materials and device concepts to be applied in practical Navy Systems. We believe this has now been realized in joint work on the composite cymbal type flextensional arrays for large area projectors, and in the progress made towards a micro-tonpilz array system. Original work on new step and repeat piezoelectric high strain systems continues to make good progress now using commercial motion rectifiers to produce both linear and rotary systems with high torque capability. New composite designs are pushing toward 1 mm diameter motors in the size regimen where there are real difficulties for conventional electromagnetic designs. A new area of activity this year is in piezoelectric transformers where a circular symmetry design in conjunction with controlled inhomogeneous poling is shown to offer capabilities which are of real interest for energy recovery actuator power systems. Basic studies have evolved a new environmental SEM technique for high resolution domain wall studies without changing problems. Work is continuing on reliable measurements of electrostrictive constants in simple solids confirming by both direct and converse methods and permitting the first generalization of trends in these fundamentally important coupling constants.
ADA381273
Acoustic Transduction Materials and Devices - Volume 2
Personal Author(s): Uchino, Kenji
Report Date: 12 Jun 2000
Descriptors: (U) *POLYMERS, *CERAMIC MATERIALS, *PIEZOELECTRIC TRANSDUCERS, COMPOSITE STRUCTURES, SINGLE CRYSTALS, ACTUATORS, FERROELECTRIC MATERIALS, ELECTROSTRICTION
Identifiers: (U) HIGH STRAIN POLYMERS, PHOTOSTRICTION
Abstract: (U) A primary objective of this MURI grouping was to help shorten the time constant for new materials and device concepts to be applied in practical Navy Systems. We believe this has now been realized in joint work on the composite cymbal type flextensional arrays for large area projectors, and in the progress made towards a micro-tonpilz array system. Original work on new step and repeat piezoelectric high strain systems continues to make good progress now using commercial motion rectifiers to produce both linear and rotary systems with high torque capability. New composite designs are pushing toward 1 mm diameter motors in the size regimen where there are real difficulties for conventional electromagnetic designs. A new area of activity this year is in piezoelectric transformers where a circular symmetry design in conjunction with controlled inhomogeneous poling is shown to offer capabilities which are of real interest for energy recovery actuator power systems. Basic studies have evolved a new environmental SEM technique for high resolution domain wall studies without changing problems. Work is continuing on reliable measurements of electrostrictive constants in simple solids confirming by both direct and converse methods and permitting the first generalization of trends in these fundamentally important coupling constants.
ADA381272
Acoustic Transduction Materials and Devices - Volume 5
Personal Author(s): Uchino, Kenji
Report Date: 12 Jun 2000
Descriptors: (U) *POLYMERS, *CERAMIC MATERIALS, *PIEZOELECTRIC TRANSDUCERS, COMPOSITE STRUCTURES, SINGLE CRYSTALS, ACTUATORS, FERROELECTRIC MATERIALS, ELECTROSTRICTION
Identifiers: (U) HIGH STRAIN POLYMERS, PHOTOSTRICTION
Abstract: (U) A primary objective of this MURI grouping was to help shorten the time constant for new materials and device concepts to be applied in practical Navy Systems. We believe this has now been realized in joint work on the composite cymbal type flextensional arrays for large area projectors, and in the progress made towards a micro-tonpilz array system. Original work on new step and repeat piezoelectric high strain systems continues to make good progress now using commercial motion rectifiers to produce both linear and rotary systems with high torque capability. New composite designs are pushing toward 1 mm diameter motors in the size regimen where there are real difficulties for conventional electromagnetic designs. A new area of activity this year is in piezoelectric transformers where a circular symmetry design in conjunction with controlled inhomogeneous poling is shown to offer capabilities which are of real interest for energy recovery actuator power systems. Basic studies have evolved a new environmental SEM technique for high resolution domain wall studies without changing problems. Work is continuing on reliable measurements of electrostrictive constants in simple solids confirming by both direct and converse methods and permitting the first generalization of trends in these fundamentally important coupling constants.
ADA381270
Acoustic Transduction Materials and Devices - Volume 4
Personal Author(s): Uchino, Kenji
Report Date: 12 Jun 2000
Descriptors: (U) *POLYMERS, *CERAMIC MATERIALS, *PIEZOELECTRIC TRANSDUCERS, COMPOSITE STRUCTURES, SINGLE CRYSTALS, ACTUATORS, FERROELECTRIC MATERIALS, ELECTROSTRICTION
Identifiers: (U) HIGH STRAIN POLYMERS, PHOTOSTRICTION
Abstract: (U) A primary objective of this MURI grouping was to help shorten the time constant for new materials and device concepts to be applied in practical Navy Systems. We believe this has now been realized in joint work on the composite cymbal type flextensional arrays for large area projectors, and in the progress made towards a micro-tonpilz array system. Original work on new step and repeat piezoelectric high strain systems continues to make good progress now using commercial motion rectifiers to produce both linear and rotary systems with high torque capability. New composite designs are pushing toward 1 mm diameter motors in the size regimen where there are real difficulties for conventional electromagnetic designs. A new area of activity this year is in piezoelectric transformers where a circular symmetry design in conjunction with controlled inhomogeneous poling is shown to offer capabilities which are of real interest for energy recovery actuator power systems. Basic studies have evolved a new environmental SEM technique for high resolution domain wall studies without changing problems. Work is continuing on reliable measurements of electrostrictive constants in simple solids confirming by both direct and converse methods and permitting the first generalization of trends in these fundamentally important coupling constants.
ADA394818
International Conference (1st) on Multiscale Materials Phenomena in Harsh Environments Held in Limassol, Cyprus on June 19-24, 2000
Personal Author(s): Kalia, Rajiv K, Nakano, Aiichiro, Razis, Panos, Vashishta, Priya, Voyiadjis, George
Report Date: Jun 2000
Descriptors: (U) *COMPOSITE MATERIALS, STRESS STRAIN RELATIONS, RADIATION, MICROSTRUCTURE, SYMPOSIA, DAMAGE, SPACE ENVIRONMENTS, QUANTUM THEORY, DEFORMATION, SINGLE CRYSTALS, NUCLEATION, MONTE CARLO METHOD, FRACTURE(MECHANICS), CERAMIC MATERIALS, DEFECTS(MATERIALS), ELECTRONIC STATES, RESIDUAL STRESS, CREEP, PLASTIC PROPERTIES, FATIGUE(MECHANICS), SILICON COMPOUNDS, FAILURE(MECHANICS), ATOMIC PROPERTIES, MOSFET SEMICONDUCTORS, INTERMETALLIC COMPOUNDS, LOW ALLOY STEELS, NANOTECHNOLOGY, NANOSTRUCTURES
Identifiers: (U) *HARSH ENVIRONMENTS, *MULTISCALE, NANOPHASE MATERIALS, AB INITIO COMPUTATIONS
ADA378939
Development of Mullite Fibers for High-Temperature Structural Applications
Personal Author(s): Mitchell, Brian S
Report Date: 31 May 2000
Descriptors: (U) *HIGH TEMPERATURE, *CERAMIC MATRIX COMPOSITES, *COMPOSITE STRUCTURES, SILICON DIOXIDE, CRYSTALLIZATION, CERAMIC MATERIALS, SPINNING(INDUSTRIAL PROCESSES), KINETICS, INVISCID FLOW, REFRACTORY MATERIALS, ALUMINOSILICATES
Identifiers: (U) *MULLITE FIBERS, IMS(INVISCID MELT SPINNING)
Abstract: (U) Inviscid Melt Spinning (IMS) has been shown to be appropriate for the production of mullite fibers. The formation of novel mullite fiber and the optimum processing conditions required to produce the fiber are described in two archival journal publications by Zhijun Xiao and the principal investigator. The development of a novel crucible design that was used to eliminate volatilization of SiO2 from the mullite melt and a corresponding change in melt composition is also described in a publication and a provisional patent. Dr. Haoyue Zhang developed models and techniques for the characterization of crystallization kinetic parameters in these types of ceramic materials. The large-scaled production of mullite fiber and evaluation of the high-temperature properties of the fiber are the goals of future work. Work remains to be done in order to determine the suitability of IMS mullite fibers for high temperature structural composites.
ADA397027
Abstracts - 3rd International Conference and Poster Exhibition, Micro Materials, MicroMat 2000
Personal Author(s): Michel, B, Winkler, T, Werner, M, Fecht, H
Report Date: 19 Apr 2000
Descriptors: (U) *ABSTRACTS, OPTICAL PROPERTIES, NONDESTRUCTIVE TESTING, POLYMERS, GLASS, ELECTRICAL PROPERTIES, FRACTURE(MECHANICS), CERAMIC MATERIALS, MICROELECTRONICS, GERMANY, MICROMECHANICS, LECTURES, NANOTECHNOLOGY
Identifiers: (U) AQ F02-02-0264, MICRO MATERIALS, FOREIGN REPORTS
Abstract: (U) The aim of this third congress is to identify and highlight the progress achieved since the MicroMat 97 concerning mainly the different fields of micro materials applications and bring together specialists from all over the world to discuss the recent trends. Because there has been observed a considerable interest in micromaterials characterization the MicroMat organizers have invited outstanding scientists and engineers to deliver plenary and key-note lectures in different fields of materials testing and simulation. In addition to the plenary lectures, invited session and key-note session lectures, the program covers various topics of the conference with 260 oral and about 70 poster presentations.
ADA383042
Advanced Ceramics for Navy Air Vehicle Applications
Personal Author(s): Richardson, George Y
Report Date: Jan 2000
Descriptors: (U) *CERAMIC MATRIX COMPOSITES, *CERAMIC MATERIALS, *NAVAL AIRCRAFT, INFRARED SIGNATURES, MODULUS OF ELASTICITY, THERMAL STABILITY, LIGHTWEIGHT, WEAR RESISTANCE
Identifiers: (U) BRIEFING CHARTS
Abstract: (U) Advanced /Toughened Ceramics and CMC's are increasingly being sought to replace or protect metallic components for Navy Air vehicle applications due to thermal stability, light weight, high modulus, wear resistance and low Infrared signatures
ADA386439
Behavior of Brittle Materials Under Dynamic Loading
Personal Author(s): Kanel, G I, Bless, S J, Rajendran, A M
Report Date: Jan 2000
Descriptors: (U) *CERAMIC MATERIALS, *BRITTLENESS, *DYNAMIC LOADS, COMPRESSION, STRESSES, ARMOR, METEORS, SPACECRAFT, IMPACT, DAMAGE, FRAGMENTATION, LOADS(FORCES), DEFORMATION, TENSILE PROPERTIES, ELASTIC PROPERTIES, ROCK, EXPLOSIVES, THREE DIMENSIONAL, TURBINE BLADES, PARTICLES, RESPONSE, BEHAVIOR, FAILURE(MECHANICS), EXCAVATION, COMPRESSIVE PROPERTIES, POLYCRYSTALLINE
Abstract: (U) Dynamic loading of brittle materials is related to many applications, including explosive excavation of rocks, design of ceramic armor, meteor impact on spacecraft windows, particle damage to turbine blades, etc. When brittle materials are exposed to impact or explosive loading, inelastic deformation, fracture, and fragmentation occur under conditions of three-dimensional stress, where at least one stress component is compressive. Unlike fracture and fragmentation of brittle materials under tensile loading, response to compression is far from understood. Rapid application of loads can also introduce rate dependencies which make the analysis even more complicated. This review report is mainly focused on compressive failure. We have collected, reviewed, and assessed information on the behavior and properties of brittle materials that are of greatest current interest, namely polycrystalline ceramics, glasses, and rocks.
ADA397655
Internal Workshop on Interfacially Controlled Functional Materials: Electrical and Chemical Properties Held in Schloss Ringberg, Germany on March 8-13, 1998
Personal Author(s): Maier, Joachim, Tuller, Harry L
Report Date: Jan 2000
Descriptors: (U) *ELECTROCHEMISTRY, *ELECTRICAL PROPERTIES, DETECTORS, PHOTOCHEMICAL REACTIONS, CHEMICAL PROPERTIES, THERMODYNAMICS, SEMICONDUCTOR DEVICES, CERAMIC MATERIALS, CHEMICAL REACTIONS, IMAGES, GERMANY, HETEROGENEITY, CATALYSIS, KINETICS, ELECTROLYTES, FUEL CELLS, WORKSHOPS, GRAIN BOUNDARIES, SOLID PHASES, IONIC CRYSTALS, NANOTECHNOLOGY
Identifiers: (U) AQ F02-02-0280, COMPILATION REPORTS, FOREIGN REPORTS, SOLID STATE IONICS, IONIC MATERIALS, CONFERENCE PROCEEDINGS, PHOTOELECTROCHEMISTRY
Abstract: (U) These are the proceedings of the International Workshop on Interfacially Controlled Functional Materials held at Schloss Ringberg, Germany on March 8-13,1998. The workshop concentrated on the electrical and chemical properties of ionic materials. The emphasis was on systematically structured (both natural and artificial) ceramic materials in which properties are largely influenced or even completely controlled by interfaces (grain boundaries, surfaces and heterostructures). This workshop carries on the tradition of the meeting held four years ago in Ringberg on Interfaces in Ionic Materials in relation to the respective bulk phase. This conference is dedicated to the utilization of such effects to design materials and materials systems with respect to their overall properties (electrical and chemical). Important applications include sensors, fuel cells, catalysis, photoelectrochemistry and semiconducting devices.
ADA420946
Fundamental Investigation on Processing of High Performance Covalent Ceramic Nanocomposites by Polymer Precursor Pyrolysis
Personal Author(s): Kuntz, Joshua, Zhang, Guo-Dong, Mukherjee, Amiya
Report Date: Jan 2000
Descriptors: (U) *CERAMIC MATERIALS, MICROSTRUCTURE, POLYMERS, PRECURSORS, COMPOSITE MATERIALS, MATRIX MATERIALS, CRYSTALLIZATION, FRACTURE(MECHANICS), PYROLYSIS, ALUMINATES, NANOTECHNOLOGY
Identifiers: (U) NANOCOMPOSITES
Abstract: (U) Alumina based ceramic nanocomposites were investigated with the objective of improving fracture toughness. Specific focus during processing was directed at the retention of nanocrystalline microstructures in the matrix of the composites while still achieving full density. Second phases were added to the alumina matrix to investigate the applicability of toughening mechanisms that have been developed earlier for microcrystalline ceramics. The use of spark plasma sintering technique allowed the retention of ultrafine grain size of alumina due to lowered sintering temperatures and shorter sintering times. Very attractive improvements in fracture toughness were noted in Al2O3/Nb, Al2O3/carbon nanotube, Al2O3/SiC whisker, and Al2O3/Nb/carbon nanotube composites. The results were analyzed in the context of effective toughening mechanisms in these nanocrystalline matrices.
