Thermal conductivity of alumina inclusion/glass matrix composite materials: local and macroscopic scales

The thermal conductivity of a two-phase material, based on a glass matrix containing mm sized spherical alumina inclusions, has been studied as a function of the alumina phase volume fraction. The glass matrix and the alumina phase were chosen with almost identical coefficients of thermal expansion to ensure good thermal contact at the interface between the two phases. The thermal conductivity of the alumina phase was determined by local measurements on the inclusions using the mirage technique. For the glass phase and the two-phase samples, the thermal conductivity values were evaluated with the laser flash technique and compared to predictions by analytical models. The Maxwell–Eucken model gives a close agreement to these experimental values for alumina volume fractions up to 55%. In fact, we show that for large mm sized alumina inclusions, Hasselman's correction for the interface thermal resistance is not necessary.