Abstract
The influences of PMMA sphere, hollow SiO2 sphere, hollow corundum sphere and AlF3·3H2O on properties of corundum-mullite refractories have been investigated. The finite-element analysis was used to simulate thermal stress of the samples in the process of thermal shock. The PMMA, hollow SiO2 and hollow corundum were used to form different pore structures. The AlF3·3H2O was used as a reaction medium to promote the mullite whiskers formation. F2 was formed by oxidation reaction between AlF3 and O2 which could react with edges of fused mullite aggregate besides corundum and silica. SEM results showed that much mullite whiskers formed in the contact area of matrix powder and fused mullite aggregate. Bridging mullite whiskers of in-situ formation between matrix and aggregates strongly improved strength performance and thermal shock resistance of corundum-mullite materials. The closed pores from hollow corundum sphere were beneficial to thermal shock resistance. The high open porosity after PMMA burning out is adverse to in-situ formation of mullite whisker. Hollow corundum sphere, AlF3·3H2O and suitable grain composition worked together providing corundum-mullite refractories of lightweight, high strength and high thermal shock resistance.
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