The preparation of refractories with both low thermal conductivity and high strength are continuously pursued in industrial furnaces. In this work, mullite refractories with low thermal conductivity and high strength were developed using fly ash as main raw material, and the influence of the quantity of fly ash and sintering temperature on the structure and properties of mullite refractories were investigated. The results show that mullite refractories with low thermal conductivity and high strength could be prepared by using fly ash in large proportion; the thermal conductivity of the samples decreased with the addition of the fly ash and increased with the increase of sintering temperature; the cold compressive strength and modulus of rupture of samples all are enhanced with the increase of sintering temperature, which is attributed to the formation of more elongated mullite by the reconstruction of fly ash at high temperature. For the mullite refractory using 65.04 wt% fly ash treated at 1600 • C, the thermal conductivity was .732W/(m⋅k) at 1000 • C, and the cold compressive strength and modulus of rupture could reach 143.5 ± 5.7 MPa and 47.0 ± 4.1 MPa respectively. It can be considered to use as a prospective work lining in industrial furnaces to meet energy saving requirements.

In the work, a novel mullite refractory was prepared by using coal gangue and low-grade raw bauxite as main raw materials, and the effect of the low-grade raw bauxite content and temperature on the microstructure and properties of mullite refractories was investigated. Both the green densities and cold compressive strength of mullite refractories increased with the increase of low-grade raw bauxite; also, the addition of low-grade raw bauxite had no significant effect on the thermal conductivity of such refractories treated at 1500°C. When the addition of low-grade raw bauxite was 34.5%, the compressive strength of the refractories treated at 1600°C was up to 104.3 MPa, and its thermal conductivity tested at 1000°C was only 1.02 W/(m K).