Abstract
Biphasic Calcium Phosphate (BCP) bioceramics were prepared in physiological pH. Salts of Calcium and Phosphate with initial molar ratio of Ca/P=1.67, similar to Hydroxyapatite (HA) stoichiometry, were precipitated by the addition of NH4HCO3 1M. XRD results of the as prepared materials show that high crystalline CaHPO4·2H2O (DCPD) was produced, resulting a decrease of the initial Ca/P ratio. However ageing of the slurry under continuous stirring for 1 and 2 days time, lead to the gradual hydrolysis of dicalcium phosphate dihydrate (DCPD) to low crystalline HA producing biphasic HA/DCPD particles. Ageing time affects also the morphology of the materials. SEM images show that the initial lath-like DCPD particles with HA during the ageing were transformed firstly into bigger particles and flake like particles afterwards. The above mentioned are in accordance to the results of TG/DTA analysis. The morphology and the phase composition of the yielding materials depend on the initial concentration of HCO3− and ageing time. Hydrolysis of NH4HCO3, affects the precipitation of both Ca2+ and PO43− on the starting material, under physiological pH and thus has to be manipulated properly in order to achieve the desirable results in a possible hard tissue evaluation of in vitro bioactivity.
Published Version
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