Synthesis of Al₄SiC₄ powders via carbothermic reduction: Reaction and grain growth mechanisms

Highly pure Al₄SiC₄ powders were prepared by carbothermic reduction at 2173 K using Al₂O₃, SiO₂, and graphite as raw materials. The obtained Al₄SiC₄ powders owned hexagonal plate-like grains with a diameter of about 200-300 μm and a thickness of about 2-6 μm. Based on the experimental results, the reaction of Al₄SiC₄ formation and grain evolution mechanisms were determined from thermodynamic and first-principles calculations. The results indicated that the synthesis of Al₄SiC₄ by the carbothermic reduction consisted of two parts, i.e., solid-solid reactions initially followed by complex gas-solid and gas-gas reactions. The grain growth mechanism of Al₄SiC₄ featured a two-dimensional nucleation and growth mechanism. The gas phases formed during the sintering process favored the preferential grain growth of (0010) and $(1\overline{1}0)$ planes resulting in formation of hexagonal plate-like Al₄SiC₄ grains.