Formation mechanism of large size plate-like Al4SiC4 grains by a carbothermal reduction method

Abstract

High temperature experiments and thermodynamic calculations were carried out to investigate the formation mechanism of large size plate-like Al₄SiC₄ grains during a carbothermal reduction process. Al₄SiC₄ grains with different morphologies were synthesized at different temperatures and plate-like Al₄SiC₄ grains with an average diameter of above 100 μm were obtained. The atomic structure of Al₄SiC₄ at different temperatures was obtained by using HRTEM with SAED. The results indicated that Al₄SiC₄ crystal nuclei were firstly formed by solid–solid reactions and then grew into little grains with the assistance of reactant gases. Then, large plate-like grains with a porous surface were formed via sintering of those little Al₄SiC₄ grains. Then, through the evaporation–condensation mass transfer process, the pores disappeared and large size hexagonal plate-like Al₄SiC₄ grains were eventually formed in the product.