An Innovative Approach to Synthesis to Porous Intermetallic Matrix Composites for Regenerative Cooling Below 20K

40997 November 19, 1996 MER Chlorofluorocarbons (Freon) are being phased out of use for refrigeration. This project will develop a processing technology for active magnetic refrigeration devices which are being considered as candidates for replacements. Brittle intermetallics will be processed into a "tubular channels in solid block" geometry. Because the synthesis of such composites is extremely difficult, given their brittle nature, the conventional approach is to use a bed of intermetallic powders. However, numerical calculations indicate that alternate bed geometries, such as a solid block consisting of ~50-60 ¿m diameter channels or a series of stacked porous plates, hold promise for a 25% enhancement in operating efficiency. In this new approach, individual fibers are coated with the intermetallic and densified. The thickness of the matrix coating on individual fibers affords a convenient means to control the matrix volume fraction, and hence the porosity in the composite. Then, the fibers are removed to yield continuous channels of constant pore size throughout a solid block. Alternately, the solid blocks can be sliced into thin porous plates which can be stacked appropriately for the highest efficiency. Anticipated Results/Potential Commercial Applications as described by the awardee: Magnetic refrigeration systems have been proposed for several applications from production of superfluid helium to comfort air conditioning. Other applications include refrigerators for cooling high temperature superconductor devices such as magnetic energy systems, motors, generators, etc. and one-ton per day high efficiency hydrogen liquefier.