China's Refractories

Abstract: Affected by increasingly stringent environmental protection policies, the quality fluctuation of industrial lime milk has become a common bottleneck restricting the stable production of silica bricks, leading to inhomogeneous crystalline phases and unstable performance. In this study, silica bricks were prepared using high-purity silica as the main raw material, and CaO-based mineralizers were introduced through three methods: conventional industrial lime milk, direct mixing of Ca(OH)₂ powder with water, and pre-dispersed Ca(OH)₂ emulsion. The effects of different Ca(OH)₂ introduction methods on the phase transformation, microstructure and properties of the silica bricks were investigated. The results show that the silica bricks fabricated with pre-dispersed Ca(OH)₂ emulsion present equivalent comprehensive properties to those of the traditional lime milk process. Compared with the traditional specimen, the relative β-tridymite content increases by 12.0% and the residual quartz content decreases to 2.0%. The pre-dispersed emulsion promotes sufficient phase transformation from quartz to β-tridymite and optimizes the microstructure via four core mechanisms, including thermal decomposition matching, nano-activation effect, liquid phase regulation and lattice defect strengthening. It can completely replace traditional industrial lime milk as a mineralizer, fundamentally solving the production stability problem caused by unstable mineralizer activity and showing outstanding industrial application potential.

Key words: silica bricks, lime milk, Ca(OH)₂ emulsion, phase transformation, β-tridymite