STUDIES OF THERMIONIC MATERIALS FOR SPACE POWER APPLICATIONS. Quarterly Progress Report, September 1, 1963-November 30, 1963

Isostatic-pressing techniques using reversible gels as the pressing medium were studied for improving the uniformity in density and structure of UC-- ZrC bodies. Control of powder-size fraction was studied as a means for controlling the pore distribution. Control of the carbon content by thermal treatment in a mixture of H/sub 2/ and hydrocarbon was also studied. Near stoichiometric 30 UC--70 ZrC powder was prepared by gas-metal reaction. Assembly of an apparatus for study of the thermochemical vapor-deposition of tungsten is near completion. The vaporization and fission product release rates of a hot- pressed high-density 30 UC -70 ZrC sample were measured from 1800 to 2000 deg C. A low-pressure gas adsorption apparatus was set up for measuring the true surface area of UC-ZrC samples. The cell used for the study of fission product diffusion through tungsten was fabricated. Samples are being prepared for fuel-clad compatibility and refractory-metal interdiffusion studies. Diffusion-emission studies were made on a rhenium-clad UC sample at 1800 deg C. The molybdenum pedestal of the loading device of a high-temperature mechanical testing furnace was modified. Thermionic emission microscopy showed that areas of high work function can co-exist with betteremitting UO/sub 2/ dispersions on the surface of a W-UO/sub 2/ cermet at 1650 deg C. Life-testing cells for fueled cesium converters using planar, as well as cylindrical fueled emitters were designed. The cylindrical configuration was favored, since a reliable cylindrical cell envelope was developed. (auth