Preparation of hollow silica particles by template method via chemical vapor deposition

Hollow silica particles (HSPs) were prepared using calcium carbonate (CaCO3) templates coated with silica layers via chemical vapor deposition (CVD), and the effects of the deposition duration on the microstructure and pore structure of the HSPs were investigated. The silica layers were deposited on the CaCO3 template particles by a rotary CVD technique at a deposition temperature of 540 °C. The amount and thickness of silica layers in the resultant silica-coated CaCO3 templates prepared with deposition time of 60–240 min were estimated as 12.2–16.6 wt.% and 17.4–22.9 nm, respectively, by thermogravimetry. HSPs were formed by removing of the templates by acid treatment, which had 10–30 nm thick silica shells with angular morphologies that were inherited from those of the templates. The specific surface area of the HSPs increased from 75 to 466 m2/g as the deposition time decreased from 240 to 60 min. The HSPs using the silica-coated template prepared at 60 min involved a large number of micropores (223 m2/g) as well as bursts and holes that were formed by the removal process of the templates, whereas no micropores were formed in the HSPs when the deposition duration was prolonged to 120–240 min.