Abstract: A composite material which comprises an elastomer or vulcanized rubber and particles of a high-density material, such as tungsten, evenly dispersed therein, wherein the contents of the elastomer or vulcanized rubber and the high-density particles are 35 to 50 vol. % and 50 to 65 vol. %, respectively, based on the whole composite material, and the high-density particles have a particle composition comprising 60 to 80 vol. % coarse particles having a particle diameter of 10 to 100 ?m, 10 to 20 vol. % medium particles having a particle diameter of 3 to 6 ?m, and 10 to 20 vol. % fine particles having a particle diameter of 1 to 2 ?m, the spaces among the coarse particles being filled with the medium particles and fine particles. The composite material is excellent in flexibility and processability and is suitable for use as a radiation-shielding sheet material, weight member, vibration-damping material, balancing member, radiating material, and shot material.

Abstract: A composite material which comprises an elastomer or vulcanized rubber and particles of a high-density material, such as tungsten, evenly dispersed therein, wherein the contents of the elastomer or vulcanized rubber and the high-density particles are 35 to 50 vol. % and 50 to 65 vol. %, respectively, based on the whole composite material, and the high-density particles have a particle composition comprising 60 to 80 vol. % coarse particles having a particle diameter of 10 to 100 ?m, 10 to 20 vol. % medium particles having a particle diameter of 3 to 6 ?m, and 10 to 20 vol. % fine particles having a particle diameter of 1 to 2 ?m, the spaces among the coarse particles being filled with the medium particles and fine particles. The composite material is excellent in flexibility and processability and is suitable for use as a radiation-shielding sheet material, weight member, vibration-damping material, balancing member, radiating material, and shot material.

Abstract: A substrate serving as a heat sink for a semiconductor efficiently radiates heat from a semiconductor element mounted thereon. The substrate consists of a composite alloy metal which consists of a sintered body of a metal powder having a high melting point such as W and Mo impregnated with a filling metal such as Cu and Ag, wherein the sintered body of a metal powder having a high melting point has a grain size composition of a combination of a plurality of powder groups having statistically different average grain sizes from group to group, and the powder of each group is dispersed uniformly.