Thermal decomposition, densification and mechanical properties of AlN–SiC(–TiB2) systems with and without B, B4C and C additives

Thermal decomposition of AlN–SiC(–TiB2) systems during densification was analyzed, and effects of B, B4C and C on the densification behavior of the systems were studied. SiO2 impurity in the powder mixture was nearly completely removed by carbothermal reaction at 1500 °C in vacuum, while Al2O3 remained and affected the densification behavior of the system. The onset temperature of densification of a AlN–SiC–TiB2 system decreased from 2050 to 1850 °C by the addition of carbon, which decreased further (1680 °C) by adding both B4C and carbon. Dense AlN–SiC–TiB2 specimens were obtained after the hot pressing at 2000 °C by the application of carbon and boron or B4C. Young's modulus, hardness, fracture toughness and thermal conductivity of a AlN–SiC–TiB2 system sintered with B4C and C were 313 GPa, 18.2 GPa, 3.7 MPa m1/2 and 22.9 W/(m °C), respectively.