Preparation of micrometer- to sub-micrometer-sized nanostructured silica particles using high-energy ball milling

Nanostructured porous silica particles with sizes in the micrometer to sub-micrometer range are of great interest due to their potential applications as catalyst supports and nanocomposite materials. However, if these particles are to be used in industry, a process must be developed to affordably produce them on a large scale. This paper reports on a high-energy ball-milling process that has been used to create micrometer- to sub-micrometer-sized mesoporous silica particles starting from a silica xerogel prepared by a surfactant self-assembly sol-gel process. We have studied various milling conditions such as milling media (zirconia, stainless steel, or steel-centered nylon balls), milling time, and the presence of surfactants during milling and the resulting effect on particle size and pore structure. Results from transmission electron microscopy, scanning electron microscopy, X-ray diffraction, light scattering, and nitrogen adsorption demonstrate the feasibility of producing large quantities of nanostructured particles by this simple milling process.