Thermal Properties of Carbon Fiber Reinforced Mullite Composites Derived from Sol-Gel

Abstract

Mullite matrix composites with laminated and stitched carbon fiber cloth preform as reinforcement were fabricated via the route of “infiltration-drying-heat treatment” using Al 2 O 3 -SiO 2 sol as raw materials. Thermal properties from room temperature to 1673K of the composites were investigated. The coefficient of thermal expansion (CTE) increases first and then decreases, and reaches a maximum of 4.83×10 -6 K -1 at 1273K. As a result of the further sintering of matrix, the CTE is negative at above 1300°C. The specific heat capacity increases to the maximum of 1.547J·g -1 ·K -1 at 1473K and remains stable at above 1473K, with a minimum of 0.756J·g -1 ·K -1 at room temperature. The thermal diffusivity decreases from 1.1mm 2 ·s -1 at room temperature to 0.707 mm 2 ·s -1 at 973K as the temperature was elevated, and remains stable at above 973K. On the contrary, the thermal conductivity is improved with increasing temperature on the whole and varies from 1.859W·m -1 ·K -1 at room temperature to 2.325W·m -1 ·K -1 at 1473K.