Grinding kinetics governed by packing volume in binary glass–alumina milling

The attritor grinding of a binary glass and alumina system was studied to clarify how the packing volume controls the comminution kinetics and morphology of the ground glass. Glass and alumina particles of 1 mm were mixed at a 1 to 1 weight ratio and milled dry at 800 rpm with packing volumes of 40 mL and 80 mL. Size distributions were measured by sieving, component separation in each size fraction was quantified by X-ray fluorescence, and glass morphology was evaluated by scanning electron microscopy. Population balance modeling yielded the grinding rate constant and size distribution index for glass. The 80 mL condition promoted faster early size reduction in 10 min, whereas the 40 mL condition achieved stronger long-term comminution in 40 min, leading to a reversal in the grinding performance in the glass size distribution with time. The aspect ratio increased under both conditions, whereas circularity decreased more significantly at 40 mL, indicating more angular fragmentation. Discrete element method simulations showed that 80 mL increased the collision frequency but was dominated by low-energy impacts in an upper slow-moving layer. In contrast, 40 mL enhanced the high-energy impacts, particularly particle-wall collisions near the agitator, thereby accelerating fragmentation.