Preparing β-SiAlON ceramic foam filters with high oxidation resistance

Abstract

Herein, to develop ceramic foam filters (CFFs) with high porosity and strength, porous β-SiAlON ceramic foam was prepared using Si, α-Al2O3, and AlN via foam impregnation. Experiments were performed to investigate the effects of the slurry solid content, impregnation times, and sintering temperature on the sample properties. The best green bodies were obtained at a slurry solid content of ∼70 wt%, and the sample subjected to two impregnation times effectively filled the defects. The sintering temperature was found to affect the phase composition, microstructure, sintering behavior, mechanical properties, and oxidation resistance of β-SiAlON ceramic foams. Granular β-SiAlON started to develop at 1550 °C and was almost completely developed at 1600 °C. After sintering at 1650 °C, the porosity remained as high as 85.93% and the compressive strength reached 1.57 MPa. In a nonisothermal oxidation experiment, the maximum oxidation weight gain rate was 14.1% and the sample strength still reached 1.54 MPa at 1600 °C. A high sintering temperature promoted the development of material phases and liquefaction of grains, while the oxidized surface generated an amorphous layer with a high melting point, effectively preventing oxygen diffusion. Therefore, β-SiAlON can be employed to develop CFFs with high strength and excellent oxidation resistance.