Effects of composition and milling medium on mechanosynthesis of chlorapatite-alumina composite nanopowders

The effects of alumina content and milling medium on the formation of chlorapatite-based composite nanopowders were studied. The powder mixtures with various compositions were activated in a high-energy planetary ball mill for 5 h using two distinct milling media. The first medium (M1) was composed of sealed tempered chrome steel vial and un-fused alumina balls. The second medium (M2) consisted of sealed tempered chrome steel vial and balls. In the presence of different amounts of γ-Al2O3, no mechanochemical reaction occurred in M1 medium. In contrast, in the second medium (M2), chlorapatite−alumina composite nanopowders were obtained after 5 h of milling in the presence of 4 and 7 wt% alumina. In the presence of 4 wt% alumina, crystallite size and lattice strain of the product were about 30±2 nm and 0.62±0.031%, respectively. With increasing the alumina content to 7 wt%, the lattice strain declined to 0.57±0.029%, while the crystalline size increased to around 32±2 nm. From the electron microscopic images, the synthesized composite nanopowder had a cluster-like structure with an average particle size of about 97 nm.