Effect of fly ash cenospheres on the microstructure and properties of silica-based composites

Effects of fly ash cenospheres on the microstructure and properties of silica-based composites were studied in this paper. It was found that the density of the samples decreased as the content of fly ash cenospheres increased, while the strength increased inversely when the content was lower than 50 wt%. An interlaced microstructure of lath-like and needle-like mullite crystals was discovered in the composites, which was a beneficial factor for strengthening the silica matrix. Furthermore, the results indicated that fly ash cenospheres can promote the densification of silica as a sintering aid and restrain the crystallization of cristobalite as an inhibitor. After sintered at 1200 °C for 2 h, the density and flexural strength of silica-based composites with 50 wt% fly ash cenospheres were 0.92 g/cm3 and 14.5 MPa separately, and the strength was as high as that of the silica ceramics without fly ash cenospheres.