Synthesis and characterization of Al2O3/SiC composite ceramics via carbothermal reduction of aluminosilicate precursor for solar sensible thermal storage

Al2O3 material with high heat capacity and high thermal conductivity was in situ formed to bond with SiC for synthesizing Al2O3/SiC composite ceramics by the removal of silica in aluminosilicate precursor using carbothermal reduction method. Phase transformation, microstructural evolution, and the relevant variations in properties were studied in the temperature range 1460-1580 degrees C. Results indicated that the addition of Y2O3 improved the carbothermal reaction rate significantly and decreased the finish temperature of carbothermal reaction to 1500 degrees C. Incorporation of the in situ formed Al2O3 could lower the sintering temperature of SiC ceramic without decreasing the heat capacity. By sintering at the optimal temperature as 1540 degrees C, Al2O3/SiC composite ceramics with the heat capacity of 1.16 J/(g.K) and the high thermal conductivity of 13.73 W/(m.K) were obtained. The relatively high thermal conductivity endowed the composites with a good thermal shock resistance. This study was intended to identify the reaction conditions for obtaining sensible thermal storage materials with favorable morphology and properties by using a simple in situ synthesis method. (C) 2015 Elsevier B.V. All rights reserved.