Grinding kinetics of amorphous powder obtained by sol-gel process

Pre-mullite powder has been synthesized by sol-gel process followed by calcination. Aluminium nitrate and tetraethyl ortosilicate (TEOS) were used as the starting materials. X-ray diffraction (XRD) analysis showed that calcined pre-mullite powder is completely amorphous. The powders were wet milled in planetary ball-mill within various time intervals. The particle size distribution of ground samples has been determined using particle size analyzer (PSA). The powder samples morphology was investigated with Scanning Electron Microscopy (SEM). Comminution kinetics of calcined pre-mullite gel is modeled using a classical batch grinding equation based on selection and breakage functions. The analytical solution of the batch grinding equation, as well as parameters of grinding kinetics was obtained through Nakajima and Tanaka approach. Analysis of experimental data resulted with model suitable for prediction of particle size distribution of calcined amorphous gel comminuted in planetary ball mill. Model is suitable if the duration of grinding is no longer than 128 min. Obtained product size distribution, for shorter grinding duration (≤ 128 min) is consistent with massive fracture mechanism. For longer grinding periods (≥ 256 min) changes of breakage mechanism indicated parallel fracture and attrition mechanism. The parameters of grinding kinetics obtained by the linear regression analysis were used to reproduce the product size distributions. The good agreement between experimental and calculated size distributions confirms the applicability of the applied rate equation to the description of grinding of calcined amorphous gel.