Hydrothermal synthesis of hydroxyapatite crystals with and without seed crystals and surfactant

To the best of our knowledge for the first time the hydroxyapatite (HA) crystals were synthesized with different doses of HA seed crystals. HA crystals were synthesized from solutions containing the stoichiometric amounts of ammonium dihydrogen phosphate and calcium hydroxide. The various interactions of the NH4H2PO4 concentrations (0.5-5.5 Molar), surfactant {amino tris (methylene phosphonic acid) [N(CH2PO3H2)3] (ATMP)} [ATMP] concentrations (0-100 ppm), and HA seed crystals doses (0-50%) were investigated and their effects on the HA mean diameter and hardness were studied using the Box-Behnken experimental statistical design. Results have shown that no correlations were obtained between the mean diameters of the HA crystals and the obtained HA hardness. HA synthesis in the absence of surfactant resulted in formation of HA rod-like and/or tabular crystals whereas agglomerated crystals were obtained with surfactant. The results indicate that with increasing the % of HA crystal seed dose, an increase in the HA mean diameter was obtained. Moreover, with increase of surfactant concentration, a high increase in HA hardness was achieved. HA crystal particle sizes were ranged from about 11-18 mu m whereas the crystallite sizes were ranged from 22 to 46 nm.