Preparation of submicron-sized quasi-spherical silica particles via ultrafine grinding with chemical dissolution assistance

Abstract

Submicron-sized silica particles with the quasi-sphericity were prepared via wet ultrafine grinding in a high energy-density stirred bead mill in the absence and presence of different salt solutions (i.e., water, potassium chloride (KCl), sodium chloride (NaCl), magnesium chloride (MgCl2), calcium chloride (CaCl2), barium chloride (BaCl2) and ammonia chloride (NH4Cl)). Effects of parameters (i.e., salt solution type, salt concentration, solid content of silica particles and grinding time) on the size/size distribution and sphericity of silica particles ground in the mill were investigated. The results show that submicron-sized quasi-spherical silica particles can be obtained under the selected condition (i.e., solution of BaCl2, BaCl2 concentration of 0.01 mol/L, solid content of 20 wt.% and grinding time of 30 min). Besides the size reduction and size distribution improvement, the sphericity can enhance from 0.71 for the original particles to 0.76 for the ground particles in the absence of any salt solution. Also, the proper addition of BaCl2 during ultrafine grinding can give a finer product with a steeper size distribution, and the particle quasi-sphericity increases from 0.76 to 0.89. It is revealed that ultrafine grinding can affect the spheroidization with and without chemical dissolution. In addition, the mechanism for ultrafine grinding of silica particles without and with chemical dissolution assistance was also discussed via the selection and breakage functions from population balance modeling.