Effect of zirconia content on the mechanosynthesis and structural features of fluorapatite-based composite nanopowders

The influence of zirconia content on the mechanosynthesis of fluorapatite-zirconia composite nanopowders was investigated. The structural features of the specimens with different amounts of monoclinic zirconia (0-20 wt%) were examined after 5 h of mechanical activation. Results indicated that the formation of fluorapatite-zirconia composite was strongly influenced by the zirconia content. In the presence of 5-10 wt% monoclinic zirconia, fluorapatite-zirconia composite nanopowders were produced after 5 h of milling. With increasing zirconia content to 20 wt%, there was no trace of fluorapatite-zirconia composite. In the absence of zirconia, the average crystallite size, lattice strain and the volume fraction of grain boundary of fluorapatite were about 34 nm, 0.469% and 8.38%, respectively. These values reached 24 nm, 0.754% and 11.71% with the addition of 10 wt% monoclinic zirconia. In the presence of 10 wt% monoclinic zirconia, the fraction of crystalline phase considerably decreased after 5 h of milling. Results revealed that the lattice parameter deviations were affected by the zirconia content. Based on SEM observations, no significant differences in the size distribution and morphology of the agglomerates were observed.