Low-cost fabrication of multicomponent silicate microspheres with tailored crystallization and morphology

This study presents a cost-effective method using sol-emulsion-gel approach to prepare micron-sized multicomponent silicate microspheres (SMs). SMs were obtained via rotary evaporation using water glass or silica sol as the silicon source. Results revealed that two-stage heating drying or two-step ion exchange treatment effectively suppressed crystallization in water glass-based SMs. The size and concentration of silicon sources and the rotary evaporation temperature dominated the sphericity and surface wrinkling of SMs. Smaller silicon sources like water glass or 5 nm silica sol with relatively high concentration, along with a suitable evaporation temperature like 65 °C, contributed to higher sphericity and smoother surfaces. The formation mechanism of microsphere crystallization and methods for its suppression were analyzed based on emulsion drying theory. Formation principles of microspheres with different morphologies were explained using wet-shell and dry-shell drying models. This method enables low-cost, large-scale fabrication of high-performance hollow glass microspheres (HGMs) with high quality SMs.