Chemical Dissolution-Assisted Ultrafine Grinding for Preparation of Quasi-Spherical Colloids of Zinc Oxide.

Submicron-sized quasi-spherical zinc oxide (ZnO) particles were prepared by wet ultrafine grinding in a stirred media mill under various conditions. The effects of parameters (i.e., solution type, acid or alkali concentration, solid content and grinding time) on the particle median size (d50), particle size distribution (PSD) and sphericity of ZnO particles was investigated. The results show that submicron-sized quasi-spherical particles (i.e., d50: 370 nm, uniformity coefficient (n) of 2.28 and sphericity of 0.91) can be obtained when the micron-sized ZnO particles are ground for 30 min in a CH3COOH solution at a concentration of 0.010 mol/L with 20 wt.% of solid content. The chemical dissolution of ZnO particles ground in the presence and absence of acetic acid is discussed. It is indicated that chemical dissolution accelerated due to the mechanochemical effects could reduce the particle size, obtain a narrower PSD and enhance the sphericity. In addition, the functions of selection and breakage were used to analyze the grinding mechanism of ZnO particles.