EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Bioactive-element doped hydroxyapatite bioceramic (dHAp) powders were successfully prepared from different calcium precursors, using wet chemical precipitation method. The bioactive ions were incorporated into the hydroxyapatite crystals by adding appropriate amount of chloride salts of Mg2+, Sr2+ and Zn2+ ions into the base solution and they were co-precipitated with the calcium phosphate particles. The phosphorous precursor was disodium hydrogen phosphate. The micro- and nanostructure of base HAp and dHAp powders from different sources were studied by scanning electron microscope (SEM) and transmission electron microscope (TEM). The measurements revealed that the structure and morphology of precipitated powders were highly dependent on the different precursors used, the precipitation parameters, pH of the suspension, the concentration of doping ions as well as the post treatment of precipitated powders after the chemical reaction. The smallest grain size with almost amorphous structure was obtained when calcium gluconate was used as Ca source, while in the case of nitrate and chloride salt of Ca, the crystallinity was higher and well defined, small, needle-like particles could be obtained. The post-treatment of suspensions with 1M Na2CO3 solution (for adjusting the pH to 11) caused phase transformation from monetite (CaHPO4) into a mixed phase of pure HAp and carbonated HAp with small, disoriented, needle-like particles in nanometre size, according to X-ray diffraction (XRD) measurement. The addition of different bioactive ions into the starting solution also changed the morphology of the precipitated powders. The doping ions were deposited in the form of low soluble phosphate precipitates along with different CaP phases. The elemental distribution of doping elements was homogeneous.

Acknowledgements: The authors are grateful for the SEM/EDX measurements to L. Illes (MTA-EK, Hungary) and thank for the financial support of National Research, Development and Innovation Office – NKFIH OTKA-PD 131934.