Effect of Mechanical Milling Time on the Synthesis of Hydroxyapatite Nanoparticles by Mechanochemical Method

Hydroxyapatite nanoparticles using planetary ball mill with a stoichiometric ratio of Ca / P = 1/67 were synthesized. For this reason two different approaches were adopted to synthesize the hydroxyapatite nanoparticles: insitu synthesis by mechanical activation method and mechanochemical method. For both methods the initial material of CaCO3 and CaHPO4.2H2O with a molar ratio of 2: 3 were used under the same milling conditions. After optimizing the parameters in the mechanochemical method the milling operation was done for 5 hours under argon atmosphere using a stainless steel milling vial. According to the STA results the heat treatment was done at 500 C for 3 hours with a heating rate of 10 C/min. For the insitu synthesis method the milling was done under argon atmosphere for 15 hours and the hydroxyapatite nanoparticles were obtained insitu and without any heat treatment. In order to characterize the formation of hydroxyapatite phase, X-ray diffraction analysis was used. Furthermore field emission scanning electron microscopy was used to determine the particle size and particle size distribution. According to the experiments, it was shown that increasing the milling time resulted in the decomposition of CaCO3 at low temperature and the increased chemical activation of the initial CaHPO4. 2H2O and CaCO3 powders. The decrease in the particle size and crystallite size caused an increase in the diffusibility and decrease in the reaction temperature of the mixed milled powder. As a result of these events, the hydroxyapatite nanoparticles obtained from both methods had a hexagonal structure with spherical morphology.