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Binary Colloidal Alloy Test - 3: Binary Alloys (BCAT-3-BA)
06.27.08

Overview | Description | Applications | Operations | Results | Publications | Images

Experiment/Payload Overview

Brief Summary

Crews were to photograph a two-component (binary) mixture of colloidal particles (tiny nanoscale spheres suspended in liquid) to document the formation of novel binary crystals not presently realizable on Earth. Results would help scientists develop fundamental physics concepts previously hindered by the effects of gravity. For example, binary alloy colloidal crystals are particularly promising candidates for photonic applications, in addition, they are of immense value as a model system for crystallization kinetics in multi-component systems. Unfortunately, this sample, number 7 of the ten BCAT-3 samples, dried out before crystallizing.

Principal Investigator

  • Peter N. Pusey, Ph.D., University of Edinburgh, United Kingdom
  • Andrew Schofield, Ph.D., University of Edinburgh, United Kingdom

    • Co-Investigator(s)/Collaborator(s)

    No Information Available

    Payload Developer

    Glenn Research Center, Cleveland, OH

    Sponsoring Agency

    National Aeronautics and Space Administration (NASA)

    Expeditions Assigned

    |8|

    Previous ISS Missions

    The predecessor to BCAT-3, BCAT, flew on Mir in 1997 and 1998.

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    Experiment/Payload Description

    Research Summary

    • BCAT-3 is comprised of three separate experiments, which are individually referred to as binary alloy (BCAT-3-BA), surface crystallization (BCAT-3-SC) and critical point (BCAT-3-CP). The critical point investigation is continuing with additional samples on future ISS expeditions and will be referred to as Binary Colloidal Alloy Test - 4. BCAT-4 will consit of two sets of samples referred to as BCAT - 3 and 4: Critical Point (BCAT-3-4-CP) and BCAT-4:Polydisperse (BCAT-4-Poly).


    • The BCAT-3-BA experiment was designed to develop new crystals that are capable of manipulating beams of light in a controlled and predictable way. Sample 7 makes up the BCAT-3-BA part of the experiment and it is a binary alloy.


    • Each of these three components of BCAT-3 takes advantage of the microgravity environment on-board the ISS. On Earth, the colloids in the mixtures being studied normally settle to the bottom of sample containers due to gravity. Colloids are suspensions of very small particles within a liquid (paint, ink and milk) and can be used to study the solidification processes that may lead to colloid engineering and the manufacture of uniquely fine controlled materials from colloids. Colloids are easier to study in microgravity where the effects of sedimentation and convection are minimized. These new colloid materials may have application in the communications and computer industries for switches, displays and optical devices with properties that could rival those of lasers.

    Description

    The Binary Colloidal Alloy Test-3 (BCAT-3) hardware supported three investigations in which ISS crews photographed samples of colloidal particles (tiny nanoscale spheres suspended in liquid) to document liquid/gas phase changes, growth of binary crystals, and the formation of colloidal crystals confined to a surface. Colloids are small enough that in a microgravity environment without sedimentation and convection, they behave much as atoms and so can be used to model all sorts of phenomena because their size, shape, and interactions can be controlled.

    The BCAT-3 payload consists of ten small samples of colloid alloys in which the microscopic colloid particles are mixed together into a liquid. These ten samples are contained within a small case that is the size of a school textbook. At the start of an experiment run, all ten samples are shaken to completely remix the colloid samples, much in the same way that salad dressing must be shaken to remix oil and vinegar. After the samples are mixed, what remains is periodically photographed using a digital camera until the colloid and liquid components of those samples have separated or the polymers have formed crystals. The samples can be remixed to repeat the experiment.

    The ten samples in BCAT-3 were selected as part of three separate experiments examining different physical processes: critical point, binary alloys, and surface crystallization.

    Colloids are also technologically interesting because they are the right size to manipulate light. Natural opal is likely the oldest and best known of the "photonic" crystals that direct light. Shine white light on the opal and a rainbow appears, demonstrating how colors of light are split up and sent in different directions. The ability to better control the movement of light is a major technological goal, not only to build computers operating on light instead of electricity but also to harness the full capabilities of existing fiber-optic networks for improving communications. Crystal structures built from only one building block, e.g., the arrangement of colloidal silica spheres in an opal, are well understood, but their optical properties are limited. More useful photonic crystals can be built from two different types of building blocks mixed together, yielding a binary alloy. The resulting structures and their optical properties are vast, as both the size and the proportion of the two building blocks can be varied. How crystallization is affected by these changes is only beginning to be explored. Theoretical studies suggest that desired optical properties require more complicated crystal structures, but this has not been well explored experimentally. Microgravity is crucial to the binary crystal experiments, allowing the growth of crystals far larger than those created on the surface of the Earth. The BCAT-3 binary alloy sample furthers previous investigations on binary growth in space.

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    Applications

    Space Applications

    This experiment addresses basic physics questions, but some of the areas may eventually have applications for space exploration. The binary alloy experiment provides information that may allow improvement of fiber optics and allow development of new computers that process data with light instead of electricity, thus avoiding deleterious heating, which enable higher component density.

    Earth Applications

    Increased knowledge of some of the areas of this basic physical research may have future benefits in the application of the same physical processes on Earth. The binary alloy experiment provides information that may allow improvement of fiber optics and allow development of new computers that process data with light instead of electricity.

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    Operations

    Operational Requirements

    The BCAT-3-BA experiment is part of the BCAT-3 payload which consists of ten small samples of colloid alloys, the microscopic colloid particles all mixed together with a liquid. These ten samples are contained within a small case the size of a school textbook. The experiment requires a crew member taking digital photographs of the samples at close range. The pictures must then be downlinked to investigators on the ground for analysis.

    Operational Protocols

    At the start of the experiment in Increment 8 all viable samples were mixed by using a magnet to run a magnetic stirbar up and down through the samples. This completely mixes and homogenizes the colloid samples. After the samples were mixed, the lights in the U.S. Lab are dimmed and photographs are taken to document the rate of crystallization for sample 7. These photographs are downlinked to the ground.

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    Results/More Information

    The sample dried out and was unavailable for experiments on ISS.

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    Related Web Sites
  • BCAT-3
  • Photographing Physics: Critical Research in Space

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    Publications

    Results Publications

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      Related Publications
      • Doherty MP, Koudelka JM, Motil SM, Saavedra SM. Light Scattering for complex Fluids Research on ISS: Investigator Dreams and Anticipated Hardware Development. Proceedings of the 37th Aerospace Sciences Meeting and Exhibit. ;AIAA 1999-0964. 1999
      • Ansari RR, Hovenac EA, Sankaran S, Koudelka JM, Weitz DA, Cipelletti L, Segre PN. Physics of Colloids in Space Experiment. Space Technology and Applications International Forum. . 1999
      • Doherty MP, Lant CT, Ling JS. The Physics of Hard Spheres Experiment on MSL-1: Required Measurements and Instrument Performance. Proceedings of the 36th Aerospace Sciences Meeting and Exhibit. ;AIAA 1998-0462. 1998
      • Lant CT, Smart AE, Cannell DS, Meyer WV, Doherty MP. Physics of hard spheres experiment--a general purpose light scattering instrument. Applied Optics. ;35:7501-7507. 1997
      • Manley S, Cipelletti L, Trappe V,Bailey AE, Christianson RJ, Gasser U, Prasad V, Segre PN, Doherty MP, Sankaran S, Jankovsky AL, Shiley B, Bowen J, Eggers J, Kurta C, Lorik T, Weitz DA. Limits to Gelation in Colloidal Aggregation. Physical Review Letters. ;93(10):108302. 2004

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      Images

      imageNASA Image: ISS008E20221- BCAT-3 sample holder affixed to a wall inside ISS on Expedition 8.
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      imageNASA Image: ISS009E20610 - Expedition 8 Commander and Science Officer Michael Foale uses the Kodak 760 digital still camera to photograph a Slow Growth Sample Module for the Binary Colloidal Alloy Test-3 experiment. The SGMS is on a mounting bracket attached to the Maintenance Work Area table set up in the Destiny U.S. Laboratory. This image was used by the Expedition 8 crew at their post-flight presentation.
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      imageNASA Image: 8J2Z8924.DCR - BCAT-3, Sample 7 with air bubble, sample quality has been compromised by an unintended but contained leak. Image captured during ISS Expedition 8 on 3/29/04.
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      Information Provided and Updated by the ISS Program Scientist's Office
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