Effect of gas–solid interface on pore wall microstructure evolution during thermal melting of foamed ceramics.

In this paper, through thermal analysis of the melting process of foamed ceramics, the microstructure evolution of foamed ceramics and the effect mechanism of the appearance of gas–solid interface on the evolution of pore wall structure are studied. A new method for regulating the microstructure of pore wall based on gas–solid interface is proposed. The results show that after the initial melting temperature point, the appearance of the gas–solid interface provides a large number of heterogeneous nucleation sites, which promotes the precipitation of anorthite in the pore wall. Within the soaking time of 0–50 min, the gas–solid interface showed a decreasing trend, which resulted in a significant decrease in the anorthite content on the pore wall and eventually disappeared. The addition of alkali metal oxide-Na₂O not only reduces the melting point of the raw material, but also increases the number of gas–solid interfaces, thereby increasing the content of anorthite in the pore wall. When the Na₂O content reaches 2.1 mass%, the effect of the gas–solid interface is significantly reduced. Na₂O reacts with quartz to form a sodium silicate melt, at the same time, the addition of Na₂O provides excess O²⁻. The Mg²⁺ and Al³⁺ in the raw material combine with free O²⁻ to form spinel, which promotes the spinel precipitation in the pore wall, leading to the main crystalline phase from anorthite to spinel. This research has important guiding significance for enriching and precisely controlling the preparation process of porous materials. [ABSTRACT FROM AUTHOR]