Nucleation and Crystal Growth of Octacalcium Phosphate on Titanium Oxide Surfaces

The nucleation and growth of octacalcium phosphate (Ca 4 H(PO 4 ) 3 ·2.5H 2 O, OCP) on titanium oxide (TiO 2 ) particles have been investigated using constant composition (CC) methods in aqueous solution at 37 °C. The solid phases during the reaction were examined by X-ray diffraction, scanning electron microscopy (SEM), and diffuse reflectance Fourier transform infrared spectroscopy (FTIR). The induction period, τ, preceding the initial crystal growth of OCP, varied markedly with the relative supersaturation, σ. The interfacial free energy, γ, estimated from initial growth rate data was 11.4 mJ m - 2, while that calculated from the induction times was 13.8 mJ m - 2 . These values were of the same order of magnitude as that determined by a contact angle method involving thin layer techniques.