Effect of Thermal Expansion Mismatch on the Thermal Diffusivity of Glass‐Ni Composites

Abstract

The effect of interfacial decohesion, due to the thermal expansion mismatch, on the thermal diffusivity of a hot‐pressed glass matrix with a dispersed phase of nickel was investigated by the laser‐flash technique at 25° to 600°C. The interfacial gap formed on cooling acts as a barrier to heat flow and lowers the thermal diffusivity to values below those predicted from composite theory and also creates a strongly positive temperature dependence of the thermdl diffusivity. Preoxidation of the Ni spheres promotes interfacial bonding and yields values of thermal diffusivity higher than those for nonoxidized spheres and a thermal diffusivity which is relatively temperature‐independent. The results of the present study also confirm the criteria for the effective thermal diffusivity of composites established by Lee and Taylor.