To obtain a composite having a high thermal conductivity, a low specific gravity and the thermal expansion coefficient close to that of a ceramic substrate by specifying the thermal conductivity and thermal expansion coefficient at ambient temperature of the composite prepared by impregnating a silicon carbide-based porous material with a metal consisting essentially of aluminum and further specifying the bending strength of a structure, obtained by treating the composite with hydrochloric acid and consisting essentially of silicon carbide.
This composite is obtained by impregnating a silicon carbide-based porous material with a metal consisting essentially of aluminum and has ≥150 W/(m.K) thermal conductivity and ≤9×10-6 K-1 thermal expansion coefficient at ambient temperature. The bending strength of a structure, prepared by treating the resultant composite with hydrochloric acid and consisting essentially of silicon carbide is ≥10 MPa. The oxygen content in the composite is preferably 0.2-10 wt.% expressed in terms of silica. The treatment with the hydrochloric acid is carried out at ambient temperature for about 12 hr by using an aqueous solution of the hydrochloric acid at ≥2 N concentration. The content of the silicon carbide- based porous material in the composite is 50-80 vol.%. The metal in the composite contains ≤20 wt.% silicon and ≤5 wt.% magnesium. The density of the composite is about 3 g/cm3 effective in reducing the weight of parts. The ceramic substrate is aluminum nitride or silicon nitride.
OBATA MASAAKI
NOMURA KENJI
