Preparation of corundum-spinel-mullite porous ceramics with high strength and thermal insulation

Composite ceramics with high strength and thermal insulation were fabricated via an in-situ reaction sintering method using alumina, silica and fused magnesia as starting raw materials, and sulphite liquor as binders. The effect of MgO addition on apparent porosity, flexural and compressive strength, and thermal shock resistance of samples was investigated. The phase compositions, microstructure characteristics and mechanical properties were characterized by means of X-ray diffraction (XRD), scanning electronic microscopy (SEM) and electronic universal testing machine, the apparent porosity and thermal shock resistance of porous ceramics were also characterized. The results show that corundum-spinel-mullite porous composite ceramics are fabricated with 5% (mass fraction) fused magnesia, alumina, and silica sintering at 1450 degrees C for 3h via an in-situ reaction. The porous ceramics possess high compressive strength of 270. 25 MPa, high flexural strength of over 45MPa and apparent porosity of 26. 46%. It exhibits good thermal insulation performance with a thermal conductivity of 1. 469W . m(-1) . K-1 at room temperature, and the retention percent of residual flexural strength exceeds 27% after 3 thermal shocks. It is a promising lining material for kilns. The change of MgO content influences directly the three-phase compositions, phase morphology, pores size and distribution, which leads to non-monotonic variation of flexural strength, compressive strength and thermal shock resistance of the porous ceramics.