Heat conductive material
This invention relates to diamond-containing composite materials that have high thermal conductivity and thermal diffusivity, and to the use of such materials in heat sinks, heat spreading and other heat conductive applications. The material comprises diamond particles silicone carbide and silicon and has a thermal conductivity of at least 400 W/mK and a thermal diffusivity of at least 2.1 cm 2 /s.
1. A heat conductive composite material made from a mixture of diamond particles and comprising diamond particles, silicone carbide and silicon or silicon alloy, the silicon carbide forms an interconnected skeleton structure surrounding each individual diamond particle and silicon or silicon alloy fills the interstices of the silicon carbide skeleton, transformed diamond being the only carbon source in the material, wherein said conductive material has a diamond content of at least 58 vol % and 81 vol % at the most, a silicon carbide content of at least 3 vol % and 39 vol % at the most and a content of silicon or silicon alloy of 41 vol % at the most, and the diamond particles consist of at least two fractions with different particle size, at least 50 wt % of the particles in the mixture of diamond particles, from which the conductive material is made, having a diameter of 80 μm or above, whereby the conductive material has a thermal diffusivity of at least 2.1 cm 2 /s and a thermal conductivity of at least 400 W/mK.
2. A heat conductive material according to claim 1 , wherein the nitrogen content in the diamond fraction with the largest diameter is 300 ppm or lower and the thermal conductivity is at least 430 W/mK.
3. A heat conductive material according to claim 2 , wherein the nitrogen content in the diamond fraction with the largest diameter is 130 ppm or lower and the thermal conductivity is at least 490 W/mK.
4. A heat conductive material according to claim 3 , wherein the nitrogen content in the diamond fraction with the largest diameter is 80 ppm or lower and the thermal conductivity is at least 550 W/mK.
5. A heat conductive material according to claim 1 , wherein the silicon alloy includes at least one metal from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Cu, Ag, Al, Ge.
6. A heat conductive material according to claim 5 , wherein a small amount of a metal-carbon compound comprising at least one metal from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Cu, Ag, Al, Ge is included in the material.
7. A heat conductive material according to claim 5 , wherein the nitrogen content in the diamond fraction with the largest diameter is 100 ppm or lower and the thermal conductivity is at least 500 W/mK.