Synthesis of AlSubscript4/SubscriptSiCSubscript4/Subscript powders via carbothermic reduction: Reaction and grain growth mechanisms

摘要

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 ī0) planes resulting in formation of hexagonal plate-like Al4SiC4 grains.