Aluminium-assisted in situ synthesis of bulk SiC nanowhiskers-alumina ceramics using waste coal gangue with high carbon

Abstract

The green and efficient use of coal gangue (CG) is urgently required in the Chinese coal industry to avoid its adverse environmental impact. This study proposed an Al-assisted carbothermal reduction method to synthesise SiC–Al2O3 ceramics using high-C CG. The optimised experimental conditions for sintering SiC and their effects on the phase composition and related properties of the composites were investigated. The addition of Al optimised the in-situ synthesis pathway of SiC and significantly improved the carbothermal reaction efficiency, making the reactive temperature decrease from 1500 to 1200 °C. Additionally, sintering temperatures could modulate the SiC morphology by affecting the generation of SiO (gas) and the liquid phase of melting Al. The H3 formulation sintered at 900 °C was appropriate for producing SiCw/Al2O3 ceramics with a bending strength of 49.24 MPa, a thermal conductivity of 1.720 W (m K)−1 and good thermal shock resistance (no cracks forming after 20 cycles). This study aimed to fully combine the reactivity changes of CG with the melting reduction reaction of Al. Findings in this work offer novel insights into the synthesis of structural ceramics and the cleaner use of CG for solar thermal storage.