Program Organizers: Dr. Robert A.Schiffman, R. S. Research Inc., Barton, VT 05822; Professor Carlo Patuelli, Universita di Bologna, I-40126 Bologna, Italy
Wednesday, AM Room: Orange County 2
February 7, 1996 Location: Anaheim Marriott Hotel
Session Chairperson: J. Smith, Jr., The Department of Chemical and Materials Engineering, The University of Alabama in Huntsville, Huntsville, Alabama 35899
8:30 am
AMPOULE DESIGN AND TESTING FOR MICROGRAVITY EXPERIMENTATION ON COUPLED GROWTH IN HYPERMONOTECTICS: J.B. Andrews, J.S. O'Dell, A.B. Cheney, Y. Arikawa, L.B. Hayes, Department of Materials Science and Engineering, University of Alabama at Birmingham, Birmingham, AL 35294-4461
Microgravity experimentation on immiscible alloys presents several unique problems concerning ampoule design. This presentation will cover the steps being taken in an attempt to minimize some of these difficulties for the Al-In alloys that will be directionally solidified aboard the Life and Microgravity Space Lab during the Summer of 1996. As an example, caution must be used when selecting the ampoule material in order to avoid undesirable wetting behavior between the ampoule and the alloy. In addition, a means must be provided to accommodate the thermal contraction and solidification shrinkage during processing in order to avoid free surface formation on the melt. Steps must also be taken to control thermal end effects in order to maintain a constant growth rate during processing. The final design results in a relatively complicated ampoule assembly containing insulating segments, dummy samples, moving pistons and a high temperature spring assembly. The details of this design and the results of ground based testing on the Advanced Gradient Heating Facility engineering model in preparation for flight experimentation will be discussed.
8:50 am
MASS-TRANSFER CHARACTERISTICS OF A MULTISTAGE BIPHASIC AQUEOUS PARTITIONING SYSTEM DESIGNED FOR USE IN LOW GRAVITY: Mark Deuser, John Vellinger, John Weber, Space Hardware Optimization Technology (SHOT), Inc., Floyd Knobs, IN 47119; Martin Guinn, Paul Todd, University of Colorado, Boulder, CO 80309
Extraction of solutes from one liquid phase to another is a common method of solute purification. A 22-stage biphasic aqueous extractor has been designed and tested for applications in low gravity and as a prototype for ground-based commercial extractions. This device operates on the principle of sliding half-chambers and will test concepts of gravity dependent mass transfer in the purification of particulate products. A mass-balance model predicts the potential effects of low-gravity operations on mixing and demixing of the immiscible fluids used in the extraction process. A magnetically-driven, programmable mixing system has been designed to operate in each of the 22 chambers to assure effective mass transfer between the phases. This mixing system was successfully tested for comparison with the mass-transfer model. The overall system designed for space-flight applications includes interchangeable "cassettes" consisting of 22-stage disks preloaded with immiscible aqueous solutions and samples to be separated. The first space-flight applications of this multistage extractor will occur on Space Shuttle flight STS-77 in the SPACEHAB-04 payload module.
9:10 am
DESIGN AND DEVELOPMENT OF A SAMPLE/AMPOULE CARTRIDGE ASSEMBLY TO SUPPORT HIGH-TEMPERATURE MICROGRAVITY CRYSTAL GROWTH EXPERIMENTS: Michael R. Fiske, John D. Stark, Dean L. Heston, Teledyne Brown Engineering, 300 Sparkman Drive, MS 128, Huntsville, AL 35807
Microgravity processing of semiconductor materials has long been of interest to the science community. The microgravity environment of space holds promise for reduction of buoyancy-driven convection and sedimentation and associated structural defects. In addition, there has been significant interest in quantitatively assessing the effects of Shuttle thruster firings, crew movements, and other payload operations on the morphology of a growing crystal front. Both of these research areas can be addressed through on-orbit Current Pulse Interface Demarcation (Peltier pulsing) during the growth process to identify the shape and location of the solid-liquid interface. This paper address key issues related to the development of a Sample/Ampoule Cartridge Assembly (SACA) which incorporates a Current Pulse Interface Demarcation (CPID) capability for microgravity crystal growth experiments. These experiments have been processed in the Crystal Growth Furnace (CGF) on the second United States Microgravity Laboratory (USML-2) in late 1995 and are planned for use in CGF as part of the Space Station Furnace Facility (SSFF). Specifically, issues such a materials compatibility, cartridge fabrication, thermocouple design, electrical and mechanical interfaces, ampoule failure detection sensor design, and assembly techniques will be discussed. Results of analysis of the USML-2 SACA performance and development of SACAs for planned flights of the CGF in the Space Station Furnace Facility (SSFF) will be presented, including design approaches allowing operation at temperatures up to 1600deg.C.
9:30 am
SPACE-DRUMS(TM) - CONTAINERLESS PROCESSING OF MATERIALS USING ULTRASONICS: Edward A. Sloot, Barry L. Wetter, Canadian Space Agency, 6767 rue de l'Aeroport, St-Hubert, Quebec, Canada J3Y 8Y9
Space-DRUMS(TM) is a new Canadian technology capable of processing materials without a container in both gravity and microgravity environments using ultrasonics. The prototype system uses twenty equivalently positioned ultrasonic beams to levitate or position large samples from 5mm to 6cm in diameter inside a closed dodecahedron container. This new technological approach relies on direct acoustic radiation forces to position the sample dynamically with real-time adjustments in response to the behaviour of the material undergoing processing. A high level of sample stability is provided by the multiplicity of energy enveloping the sample specimen. Precision control of the sample is maintained by the response characteristics of the feedback mechanisms built into a novel multi processor/controller. Space-DRUMS(TM) can containerlessly process a variety of materials with temperatures as high as 3500deg.C.
9:50 am BREAK
10:10 am
RECENT RESULTS OF THE GERMAN MICROGRAVITY PROGRAM: Rainer Kuhl, Horst Binnenbruck, German Space Agency, DARA, 53227 Bonn, P.O.B. 30 03 64
Main results of fundamental and application-oriented research topics in the field Materials and Physical Sciences using microgravity conditions are outlined. This refers to precise measurements of thermophysical properties of metallic melts and nonmetallic liquids, crystal growth of semiconductor materials with external magnetic forces, the quantitative confirmation of the divergence of the specific heat of fluids near the critical point, a deeper understanding of phase separation and agglomeration processes in immiscible alloys which resulted in a new ground-based pilot production of bearing metals, and others. The results were gained by using a broad spectrum of microgravity flight opportunities such as Drop Tower Bremen, Sounding rockets TEXUS, unmanned FOTON satellites, Space Shuttle carried Spacelab and the MIR space station.
10:30 am
UTILIZATION OF A MICROGRAVITY ENVIRONMENT TO FABRICATE UNIFORMLY COMPOSITE SPHERES FROM IMMISCIBLE ALLOY SYSTEMS: R. N. Grugel, Universities Space Research Association, Marshall Space Flight Center, MS-ES75, Huntsville, AL 35812; L.N. Brush, University of Washington, Department of Materials Science and Engineering, Seattle, WA 98195
Uniform microstructures can evolve during solidification of monotectic composition alloys if the liquid reaction product (L-II) wets the primary solid (S-I). However, highly segregated macrostructures tend to develop during processing of hypermonotectic alloys. Here the interfacial surface tension can not accommodate the excess LII which then, because of Earth's gravity, runs down and hangs off the solid as is demonstrated by melting silver foil (L-II) over a suspended nickel sphere (S-I). A 1-D numerical solidification model was developed to track multiple interfaces of the bi-material drop configuration. Experimental processing parameters dictated by the model were utilized to promote and insure a uniform silver thickness on precast nickel spheres within the limited microgravity time provided by Marshall Space Flight Center's 105 meter drop tube. Results limitations, and possible applications are presented and discussed.
10:50 am
A HYBRID GLASS CRYSTAL OBSERVATION CHAMBER FOR MICRO-GRAVITY ENVIRONMENTS: Dean S. Schrage; ADF, Inc., Lewis Research Center Group, Brook Park, OH 44142
The Space Shuttle experiment, Isothermal Dendritic Growth Experiment (IDGE) will be flown on United States Micro-Gravity Payload (USMP)-4, in 1997, to evaluate the morphology of dendrite growth of a carboxilic acid, Pivalic acid (PVA). Earlier micro-gravity dendritic test programs, using Succinonitrile (SCN) as the working fluid, were successful in achieving nominal maximum supercoolings of 2.0 C. The dendrite growth with SCN were successfully performed within the confines of a crystal observation chamber (COC), ruggedized for space flight, constructed primarily of stainless steel. However, when these same chambers are filled/tested with PVA, the maximum supercooling that can be achieved, prior to auto-nucleation, decreases to 0.1 C. It is postulated that the stainless steel chamber wall material catalyzes nucleation. As this supercooling is insufficient to capture the desired dendritic growth phenomenon, a development program has been initiated to design and build a COC that will achieve, functionally the same operation as the conventional stainless steel chambers, yet harbor the PVA within the confines of inert glass material interfaces. This paper presents a detailed discussion of the development of this hybrid glass COC, presents high-level conceptual drawings and a detailed discussion of the operational characteristics.
11:10 am
LIQUID-METAL PROCESSING - ZARM: Reginald Smith, Mark Tunnicliffe,
Mark Gallerneault, Evangelos Vekris, Queen's University, Kingston, Canada K7L 3N6
Queen's University is collaborating with the University of Bremen to
investigate the freezing of liquid metals during free fall in the "ZARM" drop
tower. Of particular interest is the manner in which the undercooling at which
nucleation occurs influences the resulting microstructure. In order to produce
specimens which will begin to freeze over a particular temperature interval, 5
mm diameter samples are first "trained" by repeatedly melting and freezing at
1g under a fused glass flux. During the melting/freezing operation the flux
strips out nucleant so that reproducible nucleation behaviour may be obtained.
When trained, the flux-covered droplet is placed in an experiment capsule where
it is melted in an optical furnace. Just prior to release, the multi-specimen
assembly is plunged into a molten tin bath to effect a progressive quench so
that solidification has been completed before the fall of the drop capsule is
arrested. The equipment used and the results obtained during an experimental
campaign in September 1995 will be described.
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