Thermal diffusivity, heat capacity and thermal conductivity in Al 2O 3Ni composite

Abstract

Thermal diffusivity, heat capacity, and thermal conductivity of Al 2O 3Ni composite with 5 vol.% of Ni particulate were investigated. The thermal conductivity of the composite increases monotonically with increase of Ni particle size, and approaches a limiting value for Ni particles of 2 μm or larger. The reduced conductivity at smaller particle sizes is due primarily to the increased interfacial resistance related to the increase of Al 2O 3/Ni contact area, even though metal Ni has higher value of thermal conductivity than that of Al 2O 3. The mode of heat conduction in the composite with the smallest Ni particulate, i.e. D = 0.1 μm, is a result of both phonons and interfacial defects, and this leads of the composite characterizing with a lower temperature-dependent thermal conductivity. The Kapitza radius of the composite was experimentally determined as approximately 0.6–0.7 μm, at which the Ni conductivity is balanced by interfacial resistance, resulting in composite conductivity = matrix conductivity. This suggests that a minimum Ni particle size of ∼ 1.4 μm is essentially required for the improvement of the overall thermal conductivity in Al 2O 3Ni composite.