Synthesis and characterization of chlorapatite–ZnO composite nanopowders

Abstract

The influence of zinc oxide content on the formation of chlorapatite-based composite nanopowders in the mechanically alloyed CaO–CaCl2–P2O5–ZnO system was studied. To mechanosynthesize composite nanopowders, different amounts of hydrothermally synthesized zinc oxide nanoparticles (0–10wt%) were mixed with ingredients and then were mechanically activated for 5h. Results showed that in the absence of zinc oxide, high crystalline chlorapatite nanopowder was obtained after 5h of milling. In the presence of 4 and 7wt% zinc oxide, the main product of milling for 5h was chlorapatite–zinc oxide composite nanopowder. On increasing the zinc oxide content to 10wt%, composite nanopowder was not formed due to improper stoichiometric ratio of the reactants. The crystallite size, lattice strain, volume fraction of grain boundary, and crystallinity degree of the samples fluctuated significantly during the milling process. In the presence of 7wt% zinc oxide, the crystallite size and crystallinity degree reached 51±2nm and 79±2%, respectively. During annealing at 900°C for 1h, the crystallization of composite nanopowder occurred and as a result the crystallinity degree rose sharply to 96±3%. In addition, the crystallite size increased to 77±2nm after annealing at 900°C. According to SEM and TEM images, the composite nanopowder was composed of both ellipse-like and polygonal particles with a mean size of about 98nm.