Crystallite Size Refinement of ZrB_2 by High-Energy Ball Milling

摘要

The high-energy ball milling behavior of a commercially available ZrB_2 powder was studied by X-ray diffractometry and transmission electron microscopy. It is shown that ball milling is very effective in obtaining nanocrystalline ZrB_2 powder. Further, the crystallite size refinement occurs through repeated brittle fracture, with the final crystal size being limited by a combination of the fracture strength of particles and the com-pressive stress induced by collision of balls. With this mechanism, the crystallite size first decreases rapidly, then gradually, and finally approaches to an asymptotic limit as the ball-milling time increases. Additionally, the higher the ball-to-powder weight ratio, the faster the decrease in the crystallite size and the smaller the ultimate crystallite size.