The Preparation And Properties Of Anorthite-Mullite Composite Light-Refractory

Refractory has played a vital role in the industrial production and looking for high performance refractory is the focus of current research. Anorthite has low thermal conductivity and mullite has high refractoriness. Those properties make them famous in refractory. Single-phase anorthite and single-phase mullite were synthesized by solid phase method in this study. The effect of Al source and calcining temperature on the phase and microstructure of the powders were studied. Anorthite ceramic, mullite ceramic and the composite ceramics were prepared separately by in-situ method and two-step method. The influences of Al sources, preparation method, sintering temperature on the properties (the phase, microstructure and the mechanical properties) of ceramics were researched. And the thermal conductivity coefficients of single-phase ceramics were measured. On this basis, the effect of the types and the content of pores on the properties of anorthite/ mullite composite light-refractory were investigated.The results showed that single-phase anorthite was synthesized at 1400℃. The anorthite with Al(OH)₃ as Al source had plate appearance. The thermal conductivity coefficient of anorthite ceramic sintered at 1440℃was 1.503 W/m·K. Single-phase mullite was synthesized at 1650℃. The thermal conductivity coefficient of mullite ceramic sintered at 1690℃was 5.775 W/m·K. The anorthite/mullite composite ceramics had anorthite phase, mullite phase and unreactedα-SiO₂ and corundum. The bending strengths of the composite ceramics withα-Al₂O₃ as Al source were between the bending strength of mullite and anorthite. With SiO₂, CaCO₃ and Al(OH)₃ as raw materials, and adding 2.5% polystyrene ball, 20% sawdust and 5% graphite, the anorthite/mullite composite light-refractory was prepared at 1450℃with 20% theoretical anorthite content. The bulk density is 0.67g/cm³ . The compressive strength is 1.40MPa.