Queen's University Experiment in Liquid Diffusion (QUELD) - MIM

Objectives

The objectives of this experiment were: (1) to measure the diffusion coefficients in metallic binary systems under conditions of microgravity and (2) to provide further data and increase the understanding of the diffusion problem and of the experimental data.

Shuttle-Mir Missions
NASA-2, NASA-4, NASA-7

Approach
The QUELD payload consisted of a high temperature (900 degrees Celsius) furnace that was used to process materials requiring high melting points for liquid diffusion. Samples were processed via an automatic insertion of the sample into the pre-heated furnace. The temperature of the furnace was controlled by a programmed temperature controller. Following the necessary heating exposure, the samples were automatically withdrawn and were subsequently quenched by the automatic closure of paired quench blocks. Each sample had a individual processing routine which was stored within a movable memory module. In order to reduce the natural vibrations on the Mir Space Station, QUELD was mounted to the Microgravity Isolation Mount (MIM) to assure the best microgravity quality.

Results
The QUELD was upmassed on STS-76 on May 27, 1996 and operated during the NASA-2 mission. During the period from June 10, 1996 to August 27, 1996, crewmember Shannon Lucid processed a total of 50 samples of the 55 samples planned for this mission. All the samples were returned on STS-79 in September, 1996. The QUELD FA-1 was upmassed on STS-81 in January, 1997 and operated during NASA-4. During the period from March 21 to May 4, 1997, crewmember Jerry Linenger processed or attempted to process a total of 102 samples, 36 samples more than planned for NASA-4. Of these 102 samples, only 6 samples seem to have been affected by anomalies. All 102 samples were returned on STS-84 in May, 1997. Fifty samples were processed during the NASA-7 science increment; a failure in hardware during the NASA-2 mission postponed the processing until NASA-7.

NASA-2: As desired, none of the samples were found to have internal shrinkage cavities. As desired, the X-ray inspection showed that during processing, the surface of the molten specimens had wetted the walls of the inner sheath, an indication that Marangoni convection was minimized. The preliminary examination of the oxide interference tints on the sample surfaces and a visual inspection of the specimen materials indicate that the experiments were highly reproducible (consistent).

NASA-4: This post-mission examination revealed that some of the samples had some external oxidation but that the integrity of the sample containment was maintained. The crew processed or attempted to process 102 QUELD samples, 36 more samples than planned. Of these 102 samples, 6 samples have been affected by operating anomalies.

NASA-7: The crew processed or attempted to process 50 QUELD samples. The 38 samples from Queen's have been visually inspected by the PI and CSA and 4 samples seems to have not been processed. The 12 samples from University of Toronto will not be further analyzed until a new proposal is submitted. All samples have maintained containment integrity in spite of surface oxidation on some of the sample casings.

Earth Benefits
Accurate diffusion coefficients are of considerable importance in modeling industrial diffusion processes on Earth. Even in systems where other factors are dominant such as convection, there are boundaries within the material where diffusion is dominant. By studying liquid diffusion in microgravity, the mixture of a material is controlled by diffusion rather than convection, therefore, diffusive processes can be better observed. Improved knowledge of material processing can lead to the development of higher quality ceramics, semiconductors, and metal alloys.

Publications
None available at this time.

Principal Investigators
Reginald Smith
Queen's University, Canada

Co-Investigators
Kedar Tandon
Robert Redden

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Page last updated: 07/16/1999

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