In situ synthesis of SiC-bonded cordierite-mullite ceramics for solar thermal energy storage

Cordierite-mullite ceramic has been engaged as one of the most promising substrate materials for thermal storage in the next-generation solar thermal power generation systems. It's expected to possess high thermal conductivity and excellent mechanical strength for a good running. In this study, an in situ reaction bonding technique was developed to prepare SiC-bonded cordierite-mullite composites, using different carbon sources (graphite, phenolic resin) and silicon sources (Si, SiO2) for the synthesis of SiC. The effects of SiC content on performance and structure of the composite ceramics were studied. Results showed that the most effective bonding for SiC with cordierite-mullite was an in situ reaction between silicon (Si) and graphite. Correspondingly, the optimum sample with 40 wt% SiC showed an obvious improvement of both mechanical strength and thermal conductivity, which was 109.67 MPa and 5.8782 (25 degrees C) W/(m K) respectively. The characterization of the as-synthesized SiC showed a relatively uniform diameter, a much smooth surface and a completely intertwined structure, which formed thermally conductive channels of SiC-SiC and presented mechanical strength enhancement of reinforcing-toughening effect. To understand the synthesis mechanism of SiCw bonded in the composite ceramics, we found that the silicon source played a key role and suggested that the growth mechanism of SiC was a liquid-solid (L-S) mechanism. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.