5 and a thermal conductivity of 20 w m u2212 1 k u2212 1 the alumina particles were initially coated with the liquid gallium alloy the liquid metal to alumina volume ratios were selected in three different ranges as set forth in table i hereinbelow the coating was accomplished by mechanically mixing the alumina powder with the liquid gallium alloy of example i and this may be achieved either by hand or in a high speed mixer mixing was followed by addition of the appropriate amount of the silicone oil followed by high speed mixing until a visually smooth paste was obtained the formulation 1 table i was tested for thermal conductivity the astm d5470 method yielded a thermal conductivity of 8 0 w m u2212 1 k u2212 1 controlled thermal impedance testing against industry standard materials was also undertaken one of these is a generic thermal interface compound from dow corning dc 340 thermal grease and another is a high performance compound made by shin etsu corporation g 749 thermal grease also tested was the gallium liquid metal of example i the thermal impedance test is shown schematically in fig7 a motorola irf840 transistor in a to 220 package was used it was powered at 60 w 30 v 2a and coupled to a.