Effect of jar shape on high-energy planetary ball milling efficiency: Simulations and experiments

Highlights: • An innovative jar shape for the planetary ball mill is proposed and characterized through simulations and experiments. • Increased high velocity collisions along impact axis enhance comminution with respect to the conventional jar. • The range of velocity ratios granting the maximum grinding efficiency is wider with respect to the conventional jar. • Information from X-Ray diffraction analysis of a milled test material support and validate simulation results. Enhanced comminution in a planetary ball mill was achieved by suitably re-designing the jar shape. Compared with a traditional cylindrical vial of circular cross-section, the new jar was modified internally to have a flat wall portion resulting in a half moon cross-section. Results from simulations using a multibody dynamics software, suggest that this geometry increases the number of high-velocity collisions with energy exchange along the axial direction, deemed as more effective in the comminution process. X-ray diffraction line profiles of calcium fluoride (CaF₂) ground in the two jars under equivalent conditions were used to obtain information on the microstructure resulting from the milling process and validate the modelling results. A better homogeneity and a faster reduction of crystallite size were achieved using the new design compared to that using the standard cylindrical vial design. Optimal operating conditions, in terms of jar-to-plate angular velocity ratio, are correlated and discussed according to the model predictions.