Optimization of process parameters for preparation of hydroxyapatite by the sol–gel method

Abstract

Hydroxyapatite (HA) powder was prepared by a sol–gel method using Ca(NO3)2·4H2O and (NH4)2HPO4 as raw materials. The usage of preset parameters just mixing the two raw materials only produced Ca2P2O7 and β-Ca3(PO4)2, without any evidence of HA. Then, effects of the reactant concentration, dropping speed, pH value, and mechanical stirring time on the reaction products were studied, and the process parameters were optimized. Results show that the optimum condition for the preparation of HA powder could be obtained by adding Ca(NO3)2·4H2O, (NH4)2HPO4, and citric acid to the reaction base solution, in turn, adjusting the pH value of the reaction solution with concentrated nitric acid to 2.5 and stirring the reaction solution manually. The parameters of calcination process were optimized by DSC analysis, and the HA powder with good crystallinity was successfully prepared.