Tuning silicon tetrachloride hydrolysis to optimize silica microstructure and sintering densification

Abstract

Fused silica (SiO₂) glass is integral to numerous industries owing to its exceptional physical and chemical attributes. Although the hydrolysis of silicon tetrachloride (SiCl₄) provides a cost-effective and straightforward route for SiO₂ production, its influence on sintering densification and the underlying mechanisms remains poorly understood. Here, amorphous SiO₂ is prepared by hydrolyzing liquid SiCl₄ at different molar ratios of SiCl₄ to water (R(SiCl₄/H₂O)). As the concentration of H₂O increases, the SiO₂ specific surface area increases, and the microstructure evolves from agglomerated blocks into a connected skeleton. Sintering these hydrolyzed green samples significantly enhances their bulk density, reaching a maximum of 1.591 g/cm³ at R = 1:70. Further analysis of the sintering activation energy reveals that this ratio also yields the lowest activation energy (34.439 kJ/mol), pinpointing the optimal conditions for achieving dense amorphous SiO₂. Additionally, the influence of different microstructures on sintering densification is clarified.