| Abstract [eng] |
Hydroxyapatite is the main inorganic component of the hard tissues of the human body, such as bones and teeth, accounting for about 70% of the skeleton and 90% of tooth enamel, therefore, it is in-demand materials for repairing bone defects, especially in the fields of dentistry, orthopedics and trauma surgery [1, 2]. Nonstoichiometric hydroxyapatite that naturally occurs in bone tissue contains small amounts of ions such as Cl-, F-, Zn2+, K+, Si2+, Ba2+, Mg2+ and Na+ [3]. Hydroxyapatite doped with Zn2+ ions, depending on the amount of doped Zn2+, is effective against gram-negative, gram-positive bacterias and fungi such as A. niger, C. Albicans. Thus, the incorporation of Zn2+ ions into hydroxyapatite not only improves the compatibility of the system, but also provides functional properties to the system [4, 5]. Therefore, the aim of this work was to investigate the influence of microwave synthesis temperature on the formation of hydroxyapatite substituted with Zn2+ ions. In this work, calcium carbonate, zinc oxide and diammonium hydrophosphate anhidride were used as raw materials for the synthesis. The synthesis of hydroxyapatite substituted with Zn2+ ions was based on the microwave method. The dry primary mixture of calcium carbonate, zinc oxide and diammonium hydrophosphate anhidride with a molar ratio of CaO/PO4=1.67 was mixed with distilled water to reach a solution/solid ratio of the suspension of 10:1. The microwave synthesis has been carried out in stirred suspensions under saturated steam pressure at the temperature of 80-200 °C for 2h. XRD, DSC, TG, and FT-IR methods were used to characterize the products of synthesis. It was determined, that not only quantity of zinc additive but also temperature of synthesis influence the formation of hydroxyapatite substituted with Zn2+ ions and the stability of intermediate compounds. By increasing the synthesis temperature, less intermediate compounds such as calcium phosphate hydroxide hydrate, hydrogen calcium phosphate, calcium phosphate, calcium hydroxide or ammonium zinc phosphate are formed. Accordingly, larger amounts of the targeted product – hydroxyapatite substituted with Zn2+ ions are formed at 200 ºC (Fig.1). Fig. 1. Results of microwave synthesis (200℃, 2h) of hydroxyapatite substituted with Zn2+ ions in CaCO3- (NH4)2HPO4-ZnO (1 mol)-H2O system XRD (a) and STA(b). Indexes: h – hydroxyapatite substituted with Zn2+ [...]. |
