The purpose of this work was to find and investigate a correlation between the carbonate ion content in crystalline lattice and defect structure, and solubility of the materials; finally, to prepare the materials under study for in vitro tests. Various techniques, such as XRD, FTIR, TEM, FESEM/EDX, TG/DTA, AES (ICP), wet chemical analysis, Ca-ionometry, microvolumetric analysis of evolved CO2, BET adsorption, were applied to determine the efficiency of carbonate substitution, and to quantify the elemental composition, as well as to characterize the structure of the carbonated hydroxyapatite and the site(s) of carbonate substitution,. It was shown that AB-type substitution prevails over other types with the carbonate content increase. According to in vitro tests, the bioactivity of the samples is correlated with the carbonate content in carbonate-doped hydroxyapatite due to accumulation of defects in carbonated hydroxyapatite nanocrystals.
Conditions for hydroxyapatite (HAP) synthesis in aqueous solutions by hydrolysis of α Са 3 (РО 4 ) 2 were studied. Temperature exerts a substantial effect on the rate of α Ca 3 (PO 4 ) 2 hydrolysis and also changes the morphology of the reaction products. At 40 °C, the plate like intersecting (perpendicular to the surface of the initial particles) crystals of HAP grow. Their maximum size after the 24 h hydrolysis is 1-2 µm. Needle like HAP crystals are formed upon boiling of the suspension. The morphology observed for the HAP particles agrees well with the conclusions obtained by analysis of the kinetics of tricalcium phosphate hydrolysis.
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