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At least 163 records · Page 9

Floating the Ball: Advances in the Technology of Electrostatic Levitation

Electrostatic Levitation (ESL) is an emerging technology. The MSFC ESL is a NASA facility that supports investigations of refractory solids and melts. The facility can be used to process a wide variety of materials including metals, alloys, ceramics, glasses and semiconductors. Containerless processing via ESL provides a high-purity environment for the study of high temperature materials and access to metastable states. Scientific topics investigated in the facility include nucleation, undercooling, metastable state formation and metallic glass formation. Additionally, the MSFC ESL provides data for the determination of phase diagrams, time-temperature-transition diagrams, viscosity, surface tension, density, heat capacity and creep resistance. In order to support a diverse research community, the MSFC ESL facility has developed a number of technical capabilities, including a portable system for in situ studies of structural tran$hrmations during processing at the high-energy X-ray beamline at the Advanced Photon Source of Argonne National Laboratory. The capabilities of the MSFC ESL facilities will be discussed and selected results of materials processing and characterization studies will be presented.

Rogers, Jan R.↗

Abstracts, Third Space Processing Symposium, Skylab results

Skylab experiments results are reported in abstracts of papers presented at the Third Space Processing Symposium. Specific areas of interest include: exothermic brazing, metals melting, crystals, reinforced composites, glasses, eutectics; physics of the low-g processes; electrophoresis, heat flow, and convection demonstrations flown on Apollo missions; and apparatus for containerless processing, heating, cooling, and containing materials.

Source record↗

Space processing viewed by a scientist-astronaut

An account is given of NASA astronaut T. G. Wang's 1985 experiences with Spacelab-borne containerless processing experiment equipment handling and experimental management. The mission in question was marred by the initial malfunction of the zero-gravity materials-processing experiment package; Wang's first task was accordingly to attempt repairs, and led to his living inside the experiment package for 2.5 days in order to operate the system as well as possible, on a 16-hr workday basis, with the assistance of two other astronauts.

Wang, Taylor G.↗

Space Processing Applications Rocket project SPAR III

This document presented the engineering report and science payload III test report and summarized the experiment objectives, design/operational concepts, and final results of each of five scientific experiments conducted during the third Space Processing Applications Rocket (SPAR) flight flown by NASA in December 1976. The five individual SPAR experiments, covering a wide and varied range of scientific materials processing objectives, were entitled: Liquid Mixing, Interaction of Bubbles with Solidification Interfaces, Epitaxial Growth of Single Crystal Film, Containerless Processing of Beryllium, and Contact and Coalescence of Viscous Bodies.

Reeves, F.↗

Processing and Mechanical Properties of NiAl-Based In-Situ Composites

In-situ composites based on the NiAl-Cr eutectic system were successfully produced by containerless processing and evaluated. The NiAl-Cr alloys had a fibrous microstructure while the NiAl-(Cr,Mo) alloys containing 1 at. percent or more molybdenum exhibited a lamellar structure. The NiAl-28Cr-6Mo eutectic displays promising high temperature strength while still maintaining a reasonable room temperature fracture toughness when compared to other NiAl-based materials. The Laves phase NiAlTa was used to strengthen NiAl and very promising creep strengths were found for the directionally solidified NiAl-NiAlTa eutectic. The eutectic composition was found to be near NiAl-15.5Ta (at. percent) and well aligned microstructures were produced at this composition. An off-eutectic composition of NiAl-14.5Ta was also processed, consisting of NiAl dendrites surrounded by aligned eutectic regions. The room temperature toughness of these two phase alloys was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa. Polyphase in-situ composites were generated by directional solidification of ternary eutectics. The systems investigated were the Ni-Al-Ta-X (X=Cr, Mo, or V) alloys. Ternary eutectics were found in each of these systems and both the eutectic composition and temperature were determined. Of these ternary eutectics, the one in the NiAl-Ta-Cr system was found to be the most promising. The fracture toughness of the NiAl-(Cr,Al)NiTa-Cr eutectic was intermediate between those of the NiAl-NiAlTa eutectic and the NiAl-Cr eutectic. The creep strength of this ternary eutectic was similar to or greater than that of the NiAl-Cr eutectic.

Johnson, David Ray↗

Dielectric-Particle Injector For Processing Of Materials

Device generates electrically charged particles of solid, or droplets of liquid, fabricated from dielectric material and projects them electrostatically, possibly injecting them into electrostatic-levitation chamber for containerless processing. Dielectric-particle or -droplet injector charges dielectric particles or droplets on zinc plate with photo-electrons generated by ultraviolet illumination, then ejects charged particles or droplets electrostatically from plate.

Leung, Philip L.↗

Drop tube research

This report covers the activities performed in the Drop Tube Study which The University of Alabama in Huntsville designed, fabricated and performed various low gravity experiments in materials processing from November 1, 1991 through October 30, 1992. During the performance of this contract the utilization of these ground-based containerless processing facilities has been instrumental in providing the opportunity to determine the feasibility of performing a number of solidification experiments in a simulated space environment, without the expense of a space-based experiment. A number of periodic reports have been given to the TCOR during the course of this contract hence this final report is meant only to summarize the many activities performed and not redundantly cover materials already submitted.

Workman, Gary L.↗

Non-contact temperature measurement requirements of ground-based research and flight programs at JPL

The Modular Containerless Processing Facility project is responsible for the development of flight equipment and of the accompanying scientific and technological research necessary to carry out containerless investigations in the low gravity of earth orbit. The requirement for sample temperature measurement is just one of the many physical properties determination needs that must be satisfied before the useful exploitation of low gravity and containerless experimentation techniques can be achieved. The specific implementation of temperature measurement for the ground-based research program is different from that of the flight hardware development project. The needs of the latter must also be differentiated according to the chronological order of the relevant space flight missions. Immediate demands of Spacelab instruments must be addressed by the adaptation of existing reliable technology to the special and restrictive on-orbit environment, while more advanced and yet unperfected techniques will be assigned to enterprises further in the future. The wide range of application of the containerless methods to the study of phenomena involving different states of matter and environmental conditions requires the satisfaction of a variety of boundary conditions through different approaches. An important issue to be resolved will be whether an integrated program dedicated to solve the problems of all the microgravity experimental effort will allow the solution of specific demands of existing as well as future flight equipment.

Trinh, E. H.↗

Crystal growth in a low gravity environment

Crystal growth in microgravity possesses several distinct technological advantages over earth-bound processes; containerless handling and reduction of density gradient driven as well as sedimentation flows. Experiments performed in space to date have been basically reproductions of processes currently used on earth and the results have clarified our understanding of crystal growth dynamics. In addition, both unresolved problems and areas requiring further study on earth have been identified. Future work in space processing of materials must address these areas of study as soon as possible if the full potential of a space environment to develop new techniques and materials is to be realized.

Carruthers, J. R.↗

The promise of space processing

The long exposure to a virtually zero-gravity environment is a truly unique situation that cannot be duplicated or even approximated for any length of time on earth. The topics discussed are: (1) low gravity; (2) atmospheric effects; (3) potential advantages of materials processing in space; (4) the absence of buoyancy-driven convection; (5) the absence of hydrostatic pressure; (6) the absence of sedimentation and buoyancy; (7) containerless processing; and (8) ultrahigh vacuum processing.

Source record↗

Post-Skylab activities

The Apollo Soyuz Test Program is described. A modification of the Skylab furnace was developed for the ASTP mission that had a maximum temperature of 1200 C, a programmed cool down to give more uniform growth rates, and a He quench system to shorten the time required to reach allowable touch temperature. The Space Processing Applications Rocket (SPAR) program was initiated to provide some continuity in flight experimentation. Liquid mixing, immiscible alloy solidification, composite materials, bubbles and dispersed particles during solidification, and containerless processing techniques were studied in the SPAR program.

Source record↗

Materials processing in space; Proceedings of the Special Conference, Cincinnati, OH, May 4, 5, 1982

An international review of materials processing in space is provided, taking into account the NASA materials processing in space program, European activities in the field of microgravity research, and Japanese material processing tests in space. The subjects considered are related to materials processing in a microgravity environment, industrial and university applications and involvement, and challenges and prospectives of microgravity research in space. Attention is given to a review of the containerless processing technologies and facilities, glass research in space, bubble behavior in molten glass in a temperature gradient, semiconductor crystal growth and segregation problems on earth and space, seeded crystal growth of pseudobinary systems with large liquidus-solidus separation, avenues and incentives for commercial use of a low-gravity environment, and the Universities Space Research Association and its role in the materials processing in space program.

Dunbar, B. J.↗

Commercialization of materials processing in space

NASA research to date on materials processing in space (MPS) has revealed that microgravity conditions to a large degree eliminate normal convection, sedimentation, buoyancy, and deformations due to gravity, and permit the exploration of containerless processing. The goals of current NASA MPS work is to augment the fundamental database on MPS and to foster commercial participation in MPS. Techniques being applied by NASA to fulfill the latter goal are described, including technical exchange, industrial guest investigator and joint endeavor agreements, and tangible market incentives. Guidelines for each type of agreement are summarized.

Yost, Charles F.↗

Reduction of Acceleration to Effectively Microgravity Levels

Pressure gradients, i.e. pressure head, and buoyancy driven convection can be greatly decreased in experimental systems by acceleration of the laboratory reference frame at a rate consistent with the acceleration due to gravity. This may be done in a number of ways, the best known of which is the use of orbiting spacecraft. Other techniques include the use of aircraft following an appropriate parabolic trajectory or drop towers. The result is an experimental condition in which fluids experience virtually no outside forces relative to the laboratory reference frame. Such conditions are appropriate for the study of processes with diffusion dominated heat and/or mass Under, the study of phase transitions in the absence of pressure gradients, the study of solutal or thermal capillary convection, or containerless processes. Ways of achieving these conditions and complexities that arise in performing experiments in this environment are discussed.

Downey, James Patton↗

Low-gravity materials experiments in the Space Station Freedom

The science and hardware programs laying the science and technology framework for experiments to be conducted aboard SSF are described. Six microgravity facilities planned for the Laboratory Module encompass the Fluid Physics/Dynamics Facility, investigating fundamental fluid behavior; the Advanced Protein Crystal Growth Facility, growing high-quality crystals for pharmaceutical, medical, chemical, and biotechnology applications; the Biotechnology Facility, investigating microgravity effects on biological processes and living organisms at the cellular level and on the purification and production of biological materials; the Space Station Furnace Facility, conducting metal and alloy solidification experiments; the Modular Containerless Processing Facility, supporting experiments through levitation techniques; and the Modular Combustion Facility, performing studies of fundumental combustion processes.

Chassay, Roger P.↗

Density of molten oxides measured in an aero-acoustic levitator

Knowing the thermophysical properties of high-temperature melts can aid the design of melt processes and validate atomic structural models, such as those used in studying glass formation. Property measurements on such melts are challenging, however, due to container-related contamination and heterogeneous nucleation. Containerless processing techniques that employ levitation can be used to avoid these obstacles. In that context, we demonstrate here the application of silhouette imaging to measure the density of molten oxides in an aero-acoustic levitation instrument (AAL). The AAL combines gas jet levitation with actively controlled acoustic positioning to enable full optical access to samples ca. 2–4 mm in diameter, which are laser beam heated and melted. The cross sections of molten drops are imaged using a monochromatic light source and narrowband-filtered camera. Melt volume is calculated from the cross sections and used to find density at several temperatures ranging 1530–1920 K, including up to 350 K of supercooling. We report densities for CaAl 2 O 4 , Ca 12 Al 14 O 33 , CaSiO 3 , their Fe 2 O 3 -bearing analogs, and 83TiO 2 -17RE 2 O 3 (RE = La or Nd). These provide important benchmarks of the capabilities, measurement uncertainties, and future outlook for this technique.

36 MATERIALS SCIENCE↗

Survey of the US materials processing and manufacturing in space program

To promote potential commercial applications of low-g technology, the materials processing and manufacturing in space program is structured to: (1) analyze the scientific principles of gravitational effects on processes used in producing materials; (2) apply the research toward the technology used to control production process (on Earth or in space, as appropriate); and (3) establish the legal and managerial framework for commercial ventures. Presently federally funded NASA research is described as well as agreements for privately funded commercial activity, and a proposed academic participation process. The future scope of the program and related capabilities using ground based facilities, aircraft, sounding rockets, and space shuttles are discussed. Areas of interest described include crystal growth; solidification of metals and alloys; containerless processing; fluids and chemical processes (including biological separation processes); and processing extraterrestrial materials.

Mckannan, E. C.↗

Glass processing in a microgravity environment

The basic techniques used in the processing of glasses and crystalline ceramics under terrestrial conditions are briefly reviewed, and the features of the space environment relevant to the processing of glasses are examined. These include reduced gravitational forces, a vacuum of essentially unlimited pumping capacity, unique radiation conditions, and the unlimited dimensions of space. Of these factors, particular attention is given to reduced gravitational forces, and the advantages of containerless processing are discussed. Finally, current programs concerned with glass processing in space are reviewed along with additional areas which merit investigation.

Uhlmann, D. R.↗