Mechanical and thermal properties of AlN–BN–SiC ceramics

Abstract: Mechanical and thermal properties were characterized for two AlN:BN:SiC composite ceramics produced from BN with different particle sizes. The ceramics were hot pressed at temperatures from 1950 to 2100°C to ∼97% relative density. For both materials, the matrix (90:10vol% SiC:AlN) had a grain size of ∼0.4μm, and the BN grains (10vol%) were crystallographically aligned. Microhardness values were between 20 and 22GPa, while fracture toughness values were between 2.5 and 3.1MPam1/2. Other properties were found to be dependent on testing direction. Elastic moduli were between 260 and 300GPa and strengths were ∼630MPa for small particle BN additions. Thermal conductivity was calculated to be between 25 and 37W/mK at room temperature and 17 and 25W/mK at 900°C. The low values compared to traditional SiC ceramics were attributed to AlN–SiC solid solution formation and sub-micron matrix grain sizes. [Copyright &y& Elsevier]