Effect of alumina bubble modification on properties of mullite castables

Mullite castables are widely used in the hot metal pretreatment processing equipment. In this work, the effects of modification of alumina bubbles with silica sol on the properties of mullite castables were studied. After the alumina bubbles were modified by silica sol, the bulk density of the samples was slightly increased, and the apparent porosity was decreased. The cold modulus of rupture values of experimental castables increased remarkably after drying at 110 °C and heating at 1400 °C for 3 h. The thermal expansion of the samples was obviously increased, while the thermal conductivity of the samples was decreased significantly. More columnar mullite crystals were formed at the alumina bubble/matrix interface after the alumina bubble modification and form a continuous inter-locking network structure, which was helpful to improve castables’ thermal shock resistance.