June 8, 2006

	In This Issue:
	NIST Bullet Tests Make Frangibles More Tangible
	NIST Software Makes Fire Gear Choice Easier
	Designer Gradients Speed Surface Science Experiments
	Circuit Board Materials May Like It Hot (or Not)
	Quick Links
	Three NIST Scientists Receive Flemming Awards
	Alliance Donates Health IT Standards Directory to NIST

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NIST Bullet Tests Make Frangibles More Tangible

Strain waves traveling at 5,000 meters per second in the NIST Kolsky bar apparatus compress a test slice from a frangible bullet to measure the precise amount of stress needed to break it apart. View video clips of two test sequences: Clip 1, Clip 2. To view video clips you must have Windows Media Player or equivalent.

Researchers at the National Institute of Standards and Technology (NIST) are measuring precisely the disintegration of “frangible” bullets when they strike a surface to better understand how the ammunition might affect body armor.

Frangible bullets, often made from sintered (formed by heat and pressure) metal powders that will break into tiny fragments, are designed to disintegrate on impact with a hard surface. They are becoming increasingly popular in situations where ricochets or “splash-back” from bullets is not tolerable. These include firearms training facilities and crowded places such as airports, courtrooms and office buildings. Additionally, the lead-free nature of frangible bullets eliminates the risk of exposure to that hazardous substance.

While frangible bullets have distinct advantages over conventional lead and copper-clad lead bullets, their characteristics are well known only for contact with hard surfaces. The behavior of such ammunition upon impact with softer materials—like those found in the soft body armors worn by many law enforcement officers and emergency responders—has raised concerns that some protective garments may be vulnerable to certain types of frangible bullets.

Initial research to assess this risk focused on ballistic penetration tests. Now NIST researchers are using a Kolsky bar apparatus—a NIST-built, air-powered device that can measure a metal’s response to the stress and strain of high-speed impacts—to document precisely what it takes for a frangible bullet to fail (or in this case, succeed, because the sintered metal’s breakdown is the desired outcome). (See www.nist.gov/public_affairs/newsfromnist_kolskybar.htm.)

The test samples are small slices from frangible bullets that are sandwiched in the space between the Kolsky apparatus’ two hardened steel bars. An air gun situated at the far end of one bar propels a striker rod into the bar. This creates a fast-traveling disturbance called a strain wave that races down the bar at 5,000 meters per second (equivalent to 11,000 miles per hour) and compresses the sample. The wave energy transmitted through the bars can be measured to determine the strain and stress that the sample has endured.

Data derived from the NIST experiments will be used to better understand what happens when frangible bullets and body armor materials interact, and then serve as the foundation for additional bullet impact studies. Once that knowledge is in hand, the Department of Justice will reassess the current body armor performance standard to determine if special accommodations are necessary for frangible bullets.

NIST’s Office of Law Enforcement Standards and DoJ’s National Institute of Justice are sponsoring the frangible bullet study.

Media Contact:
Michael E. Newman, michael.newman@nist.gov, (301) 975-3025

 

NIST Software Makes Fire Gear Choice Easier

Firefighters know that protective “turnout gear” (pants and coats) can save their lives. Yet because there are several different attributes of protective performance, choosing the turnout gear system that best matches desired performance can be complicated. Researchers at the National Institute of Standards and Technology (NIST) released a software tool this month called ToGS™ (“Turnout Gear Selector”), which helps both manufacturers and buyers decide on the turnout gear systems to design and purchase based on their individual needs.

With ToGS, the user specifies the relative “importance” value placed on each of the performance attributes, including thermal protective performance (TPP), system weight, thickness, stiffness, breathability and outer shell resistance to abrasion, tearing and charring. ToGS starts with default values established in 2005 at a NIST-hosted meeting. All turnout gear systems included in the analysis are then ranked in a bar chart based on how well they score. When the user changes the importance of an attribute, the ranking of turnout gear systems also changes. 

An urban fire department that enters multi-story buildings might place relatively high importance on attributes like TPP, system weight, breathability and resistance to charring. A rural fire department that does not have the same needs might place relatively high importance on other attributes like resistance to abrasion and tearing.

Users also can access the underlying performance data for the 41 turnout coat systems, which include nine different outer shells, five moisture barriers, eight thermal liners and seven face cloth materials.

ToGS helps users understand tradeoffs between performance attributes. For example, a better Thermal Protection Performance (TPP) score may be due to more insulation. Therefore, even though TPP is higher, such a system will be heavier and perhaps stiffer. ToGS helps the user take all tradeoffs into account when making decisions.

TOGS is available free for download at http://www2.bfrl.nist.gov/software/TOGS.

Media Contact:
John Blair, john.blair@nist.gov, (301) 975-4261

 

Designer Gradients Speed Surface Science Experiments

Illustration of NIST's new gradient surface for materials research: a graded co-polymer "brush" which gradually changes in composition from one end of a silicon substrate to the other. View hi-res version of image.

Researchers from the National Institute of Standards and Technology (NIST) have demonstrated an elegantly simple technique for synthesizing a wide variety of complex surfaces that vary in a controlled fashion across a test strip. The new technique is so flexible that it can be applied to surface science experiments ranging from developing better paints to exploring the bonding of proteins to cell membranes.

So-called “gradient composition surfaces”—their chemical composition changes gradually across the surface—have been shown to be powerful research tools for rapid, high-throughput testing of complicated surface properties, but they can be tricky to build. The new NIST technique described in a recent paper in Advanced Materials* coats a silicon wafer with a brush-like copolymer surface, varying the relative concentration of two components, or monomers, of the polymer along the length of the substrate. The dense polymer brush provides a controlled interaction surface at the top while effectively masking the underlying substrate.

The heart of the NIST technique is a combined microfluidic mixer and reaction chamber. The two components are injected into the mixer with gradually changing flow rates and mix thoroughly before filling a thin reaction chamber holding the silicon wafer substrate. Once the solution leaves the mixing region, the narrow dimensions of the reaction chamber inhibit further mixing, so the varying composition ratios through the chamber remain stable while the solution polymerizes on the substrate.

Because it keeps the fluid mixture concentrations stable for long periods, the new technique is unique in its ability to accommodate a wide variety of materials, potentially producing test surfaces for studying surface phenomena ranging from nanoscale interactions of biomolecules—critical for improving the performance of tissue-engineered medical products or for identifying the fundamental mechanisms key to cell/surface adhesion—to the performance of new products like paints or adhesives. The specific polymer used in these proof-of-concept experiments, for example, is typical of a temperature- or acidity-sensitive polymer that might be used in a drug delivery system.

For further information, see the paper cited below or visit the NIST Combinatorial Methods Center Web site at www.nist.gov/combi.

*C. Xu, S.E. Barnes, T. Wu, D.A. Fischer, D.M. DeLongchamp, J.D. Batteas, and K.L. Beers. Solution and surface composition gradients via microfluidics confinement: fabrication of a statistical-copolymer-brush composition gradient.  Adv. Mater. 2006, 18, 1427-1430.

Media Contact:
Mark Bello, mark.bello@nist.gov, (301) 975-3776

 

Circuit Board Materials May Like It Hot (or Not)

Electrical circuits may act differently in Arizona than they do in Alaska—potentially affecting the performance of computers and other electronics. A new technique identifies and quantifies an important cause of this temperature sensitivity.

Researchers at the National Institute of Standards and Technology (NIST) and DuPont Electronic Technologies (Research Triangle Park, N.C.) have demonstrated a nondestructive method for measuring how temperature affects the electrical properties of three common circuit board materials (ceramic, polymer and glass). The work, described at a recent conference,* provides manufacturers with an accurate technique for measuring high-frequency electrical properties of substrates without cutting up the material—enabling faster, less expensive and easier testing—as well as a tool for designing circuits and substrates with improved performance.

NIST has been working with ceramic and printed-wiring board manufacturers for five years to develop the technique. They previously have used the method to measure changes in electrical properties as substrates are subjected to different electromagnetic frequencies. The work is important to the electronics industry because the performance of electrical circuits depends in part on the electrical properties of the substrate.

The apparatus used in the experiments, the split-cylinder resonator, was originally designed elsewhere, but NIST developed a mathematical model that improves its accuracy and extends its frequency range. The model has been approved as an industry standard. A thin piece of substrate is placed between two halves of a cylindrical cavity—smaller than a coffee mug—inside an environmental chamber. A computer analyzes the changes in the microwave-range resonant frequency as the chamber temperature changes from -50 to 100 degrees Celsius (-58 to 212 degrees Farenheit). As the temperature rose, an important electrical property called loss tangent (a measure of electrical losses in an insulating material) fell in glass, generally increased in the organic substrate, and remained stable in one type of ceramic while rising slightly in another.

*M.D. Janezic, T. Mobley, and D. Amey. 2006. Temperature-dependent complex permittivity measurements of low-loss dielectric substrates with a split-cylinder resonator. Presented at IMAPS/ACerS International Conference and Exhibition of Ceramic Interconnect and Ceramic Microsystems Technologies (CICM), April 24-27, 2006, Denver, Colo.

Media Contact:
Laura Ost, laura.ost@nist.gov, (301) 975-4034

 

Quick Links

Three NIST Scientists Receive Flemming Awards

Three scientists from the National Institute of Standards and Technology (NIST) will be among 11 federal employees to receive the Arthur S. Flemming Awards at an awards ceremony June 13 at The George Washington University in Washington, D.C. The Flemming Awards honor those with three to 15 years of public service experience for extraordinary contributions to the federal government.

The NIST honorees are:

• Bradley K. Alpert, computer scientist, NIST Information Technology Laboratory, a premier researcher in scientific computing, including the development of fast algorithms for solutions in computational physics. Alpert also has been a mentor and leading proponent of mathematics careers for students at the high school, undergraduate, graduate, and post-graduate levels.

• Yoshihiro Ohno, group leader, Optical Technology Division, NIST Physics Laboratory, known in his field as "The Father of Modern Photometry". His research into the development of semiconductor-based lighting could potentially help reduce total electricity use in the United States by 10 percent.

• Carl J. Williams, chief, Atomic Physics Division, NIST Physics Laboratory, a world leader in applying quantum mechanics to model the collision of atoms and molecules at temperatures near absolute zero. His work on ultracold quantum mechanics has been applied to precision measurement and atomic clocks, and is laying the foundation for future quantum computing.

More information is available at http://www.gwu.edu/%7Emedia/pressrelease.cfm?ann_id=22331.

 

Alliance Donates Health IT Standards Directory to NIST

The National Alliance for Health Information Technology is donating its directory of health information technology (IT) standards to help the National Institute of Standards and Technology expand its Health Care Standards Landscape (HCSL), a Web-based repository of health care standards, standards development organizations and related information. HCSL was developed by NIST to help harmonize health IT standards and improve the safety, quality and accessibility of the nation’s healthcare system. The alliance’s directory contains more than 2,100 listings for health IT standards and links and information for the 430 organizations that created them. The HCSL can be accessed at www.nist.gov/hcsl. The alliance is a partnership of senior executives from all health-care sectors working to advance the adoption of clinical information technology systems to achieve measureable improvements in patient safety, quality of care and operating performance. For more information on the alliance, see http://www.nahit.org/cms.

 

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Editor: Michael Baum

Date created: 6/8/06
Date updated: 6/8/06
Contact: inquiries@nist.gov