Microstructures and properties of silica-based ceramic cores reinforced by alumina sol-modified fused-silica fibers

Abstract

In this study, silica-based ceramic cores with zircon as a mineralizer and fused-silica fibers modified with alumina sol as an additive were prepared via injection molding method, the effects and mechanisms of fused-silica fibers on the mechanical and high-temperature dimensional stability properties of silica-based ceramic cores were investigated. The results demonstrate that both modified and unmodified fused-silica fibers are advantageous for the mechanical properties of silica-based ceramic cores, and the improvement level depends on the bonding strength of the interface between the fibers and the matrix. However, the unmodified fused-silica fibers melted with the matrix and aggravated the viscous flow of the liquid glass phase at high temperatures, thereby severely increasing the creep deformation of the silica-based cores. The modified fused-silica fibers remain intact because the mullite shell on the surface obstructed the fusion flow of the fibers at high temperatures, which helped to retard crack propagation and also considerably reduce the creep deformation of the silica-based cores by significantly accelerating cristobalite crystallization. The core with 1 wt% alumina sol-modified fused-silica fibers exhibited excellent comprehensive performance with bending strengths of 21.48 and 23.65 MPa at room temperature and 1550 °C, respectively; creep deformation of 0.37 mm; and apparent porosity of 37.98 %, well fulfilling the requirements for single crystal hollow blade casting.