Fabrication of High Density AIN-BN Composite Ceramics by Presureless Sintering

AlN-BN composite ceramics were produced by pressureless sintering process with BN powders bought from market and AlN powders having a specific surface area of 17.4m2/g synthesized from a combustion precursor, as starting materials. The sintering behavior and characterization of AlN-BN composite ceramics were studied. The results showed that the sintering temperature for densification was from 1500 to 1650℃ because of the high sintering activity of AlN powders. AlN-15BN composite ceramics with relative density 95.6% were fabricated by sintering at 1650℃. The thermal conductivity of the composite ceramics was increased, while the density remained almost constant as sintering temperature increased. AlN-15BN composite ceramics with relative density 96.1%, thermal conductivity 132.6W·m-1·K-1, and HRA hardness 64.2 were produced by sintering at 1850℃ for 3h. The mechanism that high specific surface area AlN powders promoting the densification of AlN-BN composite ceramics was suggested, and the ?characterizations of the sintered bodies were determined by XRD, SEM and so on.