In-situ synthesis of SiCw/Al2O3 composite honeycomb ceramics by aluminium-assisted carbothermal reduction of coal series kaolin

• SiCw/Al2O3 composite honeycomb ceramics were synthesized using coal series kaolin (CSK).
• SiCw was in-situ synthesized via aluminium (Al)-assisted carbothermal reduction of CSK.
• Phase transformation and microstructure evolution of the fired CSK-Al system were studied.
• The high softening temperature and the good thermal shock resistance were obtained.
• The composite honeycomb ceramics were suitable for thermal storage applications.

A new route, aluminium (Al)-assisted carbothermal reduction of aluminosilicate mineral (coal series kaolin, CSK), was developed to in-situ produce SiCw/Al2O3 composite honeycomb ceramics using a three-step reaction scheme. The phase transformation, microstructure evolution and the relevant variations in properties of the composites had been investigated. Results indicated the reduction of CSK-Al system was found to be more superior in preparation of monolithic SiCw/Al2O3 composites under CO-rich condition comparing with the conventional CSK-carbon system. Low linear shrinkage(0.14%), good mechanical and thermophysical properties of samples could be obtained by using Al as assisted reducing agent and firing at 1550 °C as the Vickers hardness, the bending strength, the specific heat capacity and the thermal conductivity were 703.1 ± 21.6 HV, 65.9 ± 7.8 MPa, 1.09 J/(g·K) and 8.96 W/(m·K), respectively. The thermal conductivity of the Al2O3 matrix was significantly improved by the incorporation of the in-situ synthesized SiCw with an interlocking texture. The performance study of the produced SiCw/Al2O3 composite honeycomb ceramics revealed that the honeycomb ceramics were characterized by the high softening temperature and the good thermal shock resistance, which make the honeycomb ceramics suitable for the uses as porous thermal storage materials.

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