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

摘要

Mullite matrix composites with laminated and stitched carbon fiber cloth preform as reinforcement were fabricated via the route of "iefiltration-drying-heat treatment" using Al_2O_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 amaximum 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 l.lmnrt-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.