Effect of milling parameters on the formation of nanocrystalline hydroxyapatite using different raw materials

The influence of milling parameters (time and atmosphere) on the mechanochemical synthesis of nanocrystalline hydroxyapatite (n-HAp) using different raw materials was studied. Two distinct chemical reactions were activated for various milling times under air or in a high purity argon (99.998 vol%) atmosphere. Then, the mechanically activated powder was heat treated at 800 °C for 1 h to produce n-HAp with high degree of crystallinity. Results revealed that the phase purity of products under both milling atmospheres was strongly influenced by the chemical composition of raw materials. The synthesized powders exhibited average sizes about 32 and 27 nm under air atmosphere, and about 32 and 34 nm under argon atmosphere. The fraction of crystalline phase drastically decreased after 80 h of milling under both atmospheres. In addition, the fraction of crystalline phase for the annealed sample at 800 °C was higher than the mechanosynthesized specimens. The results of morphological evaluation confirmed the formation of n-HAp with different morphologies each of which can be used for particular purpose.