Preparation, microstructure and high temperature performances of porous γ-Y2Si2O7 by in situ foam-gelcasting using gelatin

Porous γ-Y2Si2O7 ceramic with good mechanical and thermal properties is prepared by the in situ reaction sintering foam-gelcasting method using Y2O3 and SiO2 as the starting powders and non-toxic gelatin as the gel former. The porous sample has interconnected large pores (40–230 μm) and small pores (0.1–2 μm) in the skeleton. The porosity can be controlled from 64.3% to 89.3% by adjusting the solid content and amount of the slurry. The corresponding strength ranges from 46.5 to 3.4 MPa. Porous γ-Y2Si2O7 with a porosity between 57.2% and 90.0% shows a low thermal conductivity in the range of 0.918–0.147 W/(m K) at room temperature. Porous γ-Y2Si2O7 has excellent mechanical property at high temperature (the strength at 1100 and 1200 °C is maintained above 71% and 50%, respectively, of the value at room temperature) and good thermal stability (the reheating shrinkage is 1.3–1.7%). This work indicates that lightweight porous γ-Y2Si2O7 ceramic could be applied as a promising high-temperature thermal insulator with low thermal conductivity and high temperature reliability.