In situ synthesis and mechanism of mullite-silicon carbide composite ceramics for solar thermal storage

摘要

SiC combined with mullite ceramic, which is an important thermal storage material in solar thermal power generation systems, was synthesized in situ by semidry pressing and carbon-buried sintering of mixtures containing andalusite, calcined bauxite, kaolin, talc and SiC. The effects of the SiC addition and sintering temperature on the physical properties, crystal phases, microstructure, thermal shock resistance, thermo-physical properties and oxidation resistance of the specimens were studied. The results indicate that the formula W-1 (SiC content: 20%) sintered at 1540 degrees C has the best performance, yielding a bending strength of 36.46 MPa, the completion of 30 cycles of the thermal shock test without cracking and an increase in the bending strength by 136.86%. The silicon carbide on the surface of the specimen is oxidized to produce a dense SiO2 protective film, which effectively prevents the oxygen from incorporating into the interior of specimen and further oxidation. Potentially, the mullite-silicon carbide composite ceramics could be applicable as materials for solar thermal storage devices.