A simple and clean method to prepare SiC-containing vitreous ceramics for solar thermal storage in the clay-feldspar system

A simple and clean in-situ method was designed to prepare SiC whisker-reinforced vitreous ceramics for solar thermal storage. SiC whiskers were in-situ synthesized in the clay-feldspar system via a carbon-buried sintering process to improve the thermal properties of vitreous ceramics. The synthesis mechanism and the optimized processing procedure of SiC-containing vitreous ceramics from the clay-feldspar system were obtained. Results indicated that the in-situ SiC whiskers were synthesized inside the pores of vitreous ceramic matrix through the vapor-solid mechanism and covered by the liquid of K2O-Al2O3-SiO2 system. SiC whiskers with a diameter of 9-23 nm decreased the thermal expansion coefficients of the vitreous ceramics significantly from 6.59 x10(-6) degrees C-1 to 4.23 x 10(-6) degrees C-1 (room temperature similar to 1000 degrees C). Meanwhile, the thermal conductivity increases to 4.78W.(m.k)(-1), 2.6 times higher than that of the original products. The increased porosity was found to improve the amount of SiC whiskers by providing space for their growth. SiC whiskers also enhanced the mechanical properties of the products and the sample with the largest content of SiC exhibited the highest bending strength of 75.7 MPa. The introduction of SiC whiskers through the in-situ synthesis method makes vitreous ceramics more competent for solar thermal storage applications. The in-situ method can save the energy and costs needed for separately producing SiC whiskers and prevent the inhalation toxicity of SiC whiskers. (C) 2019 Elsevier Ltd. All rights reserved.