Effect of boron doping on the thermal properties of carbon fibers reinforced lithium aluminosilicate matrix composites

Boron doped carbon fibers reinforced lithium aluminosilicate matrix composites (Cf/LAS) were prepared via slurry infiltration following by hot pressing procedure, and characterized by TG-DTA, XRD analysis and TEM. Their thermal expansion behavior and thermal conductivity properties were investigated across various temperatures. Dense composites samples (>99%) were sintered at 1350 °C for 0.5 h. The XRD data revealed an occurrence of single-phase β-spodumene in boron doped Cf/LAS composites. Boron doping increased the thermal stability of Cf/LAS composites in oxidizing condition, where the weight loss of Cf/LAS composites decreased with increasing boron content. Boron doped Cf/LAS composites exhibited nearly zero thermal expansion at the temperature range from room temperature to 720 °C. The thermal conductivity of boron doped Cf/LAS composites was also higher than that of boron free Cf/LAS composites. These properties were correlated with the interfacial microstructure between the fiber and the matrix as determined by TEM results.