YANG Xu, LU Yuan, ZHANG Zhen, DING Cong, SUN Fuyang
(Xi’an Special Equipment Inspection Institute, Xi’an 710065, Shaanxi, China)
Abstract: Porous ceramics are the most effective filter materials in cyclable integrated gasification. Due to its high mechanical strength and strong corrosion resistance, silicon nitride is considered to be such porous ceramics. In this paper, porous silicon nitride ceramics with high porosity and uniform pore structure were prepared through carbothermal reduction reaction between low-cost diatomite and carbon black. The influence of the type and content of sintering additives and the size of diatomite particles were studied. Microstructures and mechanical properties of the porous silicon nitride ceramics were characterized by using XRD, SEM and three-point bending measurement. It is found that β-Si3N4, a-Si3N4, Sialon Si5AlON7 and glass Y2Si3O3N4 were present in the samples. The porous silicon nitride ceramics contained rod-like β-Si3N4 grains and uniform pores. The addition of Lu2O3 with high melting point as the sintering aid enhanced the aspect ratio of the rod-like b-Si3N4 grains. As a result, the sample with 1% Lu2O3 showed a high porosity of 78.6%. As the particle size of diatomite was 1.2 mm, fine rod-like b-Si3N4 grains were obtained. The sample Y-1%-1.2 showed the optimized flexural strength of 19.7 MPa.
Key words: diatomite; carbothermal reduction; porous silicon nitride