Abstract: Samples of porous silicon oxide ceramic core were prepared using a heat-press molding method. The effects of different sintering temperatures and particle sizes on the structures and properties of the porous silicon oxide ceramic core were investigated. The result indicates that, as sintering temperature increases, the room temperature bending strength and high temperature bending strength increase and the porosity decreases. When the sintering temperature is 1 200°C, silicon oxide ceramic core shows the best overall performance for linear shrinkage rate of 2.75%, porosity of 24.69%, room temperature bending strength of 25.3 MPa and the high temperature bending strength of 44.23 MPa. Above 1 200°C, the room temperature bending strength and high temperature bending strength decrease obviously, while linear shrinkage rate and the porosity are stable. According to X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) fracture micrographs of the silicon oxide ceramic core, changes of the room temperature bending strength and high temperature bending strength are attributed to the differences of the compactness and cristobalite content at different sintering temperatures. In addition, the particle size of ceramic core has visible effects on porosity, linear shrinkage rate, and room temperature bending strength. The best overall property of the ceramic core occurrs when 25.33% of the particle sizes are less than 10 μm, 38.16% between 10 μm and 30 μm, 28.74% between 30 μm and 50 μm, and 7.77% greater than 50 μm but no more than 95 μm.

Key words: bending strength, cristobalite, porosity, silicon oxide ceramic core, sintering temperature