In situ synthesis of Al2O3-SiC powders via molten-salt-assisted aluminum/carbothermal reduction method

Al2O3-SiC composite powder (ASCP) was successfully synthesized using a novel molten-salt-assisted aluminum/carbothermal reduction (MS-ACTR) method with silica fume, aluminum powder, and carbon black as raw materials; NaCl-KCl was used as the molten salt medium. The effects of the synthesis temperature and salt-reactant ratio on the phase composition and microstructure were investigated. The results showed that the Al2O3-SiC content increased with an increase in molten salt temperature, and the salt-reactant ratio in the range of 1.5:1-2.5:1 had an impact on the fabrication of ASCP. The optimum condition for synthesizing ASCP from NaCl-KCl molten salt consisted of maintaining the temperature at 1573?K for 4?h. The chemical reaction thermodynamics and growth mechanism indicate that the molten salt plays an important role in the formation of SiC whiskers by following the vapor-solid growth mode in the MS-ACTR treatment. This study demonstrates that the addition of molten salt as a reaction medium is a promising approach for synthesizing high-melting-point composite powders at low temperatures.