ИСТИНА

The topical issues of modern biomaterials science include the manufacture of nanosized bioceramics for bone tissue replacement. The latest developments are related to regenerative approach, which requires the investigation of calcium phosphate based materials with Ca/P ratio < 1.5. The usage of non-aqueous media is a promising way to eliminate water influence, avoid the impurities and gain strong control over the material. Another advantage of non-aqueous media is the ability to explore low-temperature synthesis and thus to liquidate calcination stage. The key objects of the research were tricalcium orthophosphate (Ca3(PO4)2, TCP) and several condensed calcium phosphates (e.g. Ca2P2O7, CPP). The main requirement was the usage of liquids with high boiling point and fusible salts. Ethylene glycol was chosen due to its solvent abilities and the fact that the only coproduct of the reaction should be the solvent itself. The precursors, such as calcium glycolate, crystal orthophosphoric acid, ammonium pyrophosphate were obtained previously. TCP was obtained by adding orthophosphoric acid or commercial ammonium hydrophosphate solutions in ethylene glycol to calcium glycolate solution. CPP was obtained in ethylene glycol using the same technique: ammonium pyrophosphate solution was added to calcium glycolate solution. The syntheses were carried out in the range from 30 to 150 °C. The usage of ionic liquids is the key idea of the second approach. Temperature range from 150 to 350 °C was chosen for the calcium phosphates synthesis according to the KNO3-NaNO3 phase diagram. Calcium phosphates were obtained by mixing Ca(NO3)2- NaNO3-KNO3 melt with suspension of corresponding sodium phosphate in molten KNO3- NaNO3. By-products were washed out with alcohol. The main aspects of the samples sintering, as well as the microstructure and qualities, were analysed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and dynamic light scattering (DLS). We have developed a unique method of microcrystalline calcium ortho- and pyrophosphate powder synthesis in non-aqueous media. Also we have investigated low-temperature range for calcium phosphate synthesis. Development of the novel phosphate synthesis method makes possible obtainment of pure calcium phosphate phases without impurities of hydrophosphates. XRD data have confirmed the obtainment of pure crystalline TCP and CPP phases. DLS, SEM and TEM have demonstrated that phosphate particle size from 100 to 200 nm can be obtained.