Influences of thermal shock on thermal properties of diamond/copper composite

Different interface states of diamond/copper composites were prepared by pressure Infiltration and EHV Infiltration. The effect of interface state on thermal performance was investigated. The samples were submitted to 100 thermal shock cycles from -65 to 125°C or from -196 to 85°C. Thermal properties such as thermal conductivity and expansion coefficient were measured before and after thermal cycles. The results showed that the interfaces states of Dia/CuCr and EHV-Dia/Cu were significantly improved. The improved bonding strength would be conducive to obtain a composite material with high thermal conductivity and low thermal expansion coefficient. The thermal conductivity of Dia/Cu was only 459.1 W · m-1 · K-1, while that of EHV-Dia/Cu was up to 529.7 W · m-1 · K-1. and the thermal conductivity of Dia/CuCr was 529.7 W · m-1 · K-1. In the thermal shock test from -55 to 125°C, the thermal conductivity of Dia/Cu, Dia/CuCr and EHV-Dia/Cu maintained a good stability, each group changed within 2.5%. In the thermal shock test from -196 to 85°C, the uSermal conductivity of Dia/Cu declined rapidly after 100 thermal cycles because of its weak interface binding strength. However, the Dia/CuCr and EHV-Dia/Cu performed excellent thermal shock resistance, with their thermal conductivity only declined about 3%. The initial coefficient of thermal expansion (CTE) of DiaCu and Dia/CuCr were 8.45 × 10-6 K-1 and 6.93 × 10-6 K-1 separately. Cr addition improved the interfacial bonding strength. Low CTE of diamond increased constraining force to the high CTE of substrate, so that the CTE decreased significantly. In the two experimental conditions of thermal shock, CTE of DiaCu remained stable, Dia/CuCr increased by 6.64% and 7.22%, respectively.