Combustion synthesis of hexagonal AlN–SiC solid solution under low nitrogen pressure

Abstract

AlN–SiC solid solutions were synthesized by self-propagating combustion of powders consisting of Al, Si and carbon black (CB) under low nitrogen pressure (0.1–0.5 MPa), with the molar ratio of Al and Si, and nitrogen pressure as the main investigating parameter. The products were mainly AlN–SiC solid solution with a residual Si, and the morphology was of hexagonal crystal. Nearly pure AlN–SiC solid solution, also having the best solid-solution homogeneity in this study, was obtained by adding extra CB to the starting powders. The best Al/Si molar ratio was 1 or 1.5 and the combustion results indicated that better combustion produced a higher combustion temperature, greater product purity, and better solid solution homogeneity. Increasing nitrogen pressure (from 0.1 to 0.5 MPa) moderately increased the combustion temperature and the product homogeneity, but combustion velocity increased by around 65%. The full width at half maximum (FWHM) of AlN–SiC solid solution's (1 1 0) XRD peak, served as the homogeneity index for the AlN–SiC solid solution (D. Kata, K. Shirai, M. Ohyanagi, Z.A. Munir, J. Am. Ceram. Soc. 84 (2001) 726–732.), of all samples were summarized with the reported values in the literature, where our FWHM values were comparable to the reported data.