Nataliia Yu. Strutynska

Structure of Biocompatible Coatings Produced from Hydroxyapatite Nanoparticles by Detonation Spraying.

Detonation-produced hydroxyapatite coatings were studied by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Raman spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy. The source material for detonation spraying was a B-type carbonated hydroxyapatite powder. The coatings consisted of tetracalcium phosphate and apatite. The ratio depended slightly on the degree of crystallinity of the initial powder and processing parameters of the coating preparation. The tetracalcium phosphate phase was homogeneous; the apatite phase contained defects localized on the sixfold axis and consisted of hydroxyapatite and oxyapatite. Technological factors contributing to the transformation of hydroxyapatite powder structure during coating formation by detonation spraying are discussed.

Synthesis, Characterization and EPR Investigation of γ-Induced Defects of Nanoparticles of (MI, CO3)-Containing Apatites (MI – Na, K)

The nanoparticles of (Na, CO3)- and (K, CO3)-containing Calcium phosphates have been prepared by a wet precipitation method in aqueous media. The influence of nature of alkaline metal and of samples composition on particles size and peculiars of their thermal transformation have been studied using such physical-chemical methods as FTIR, XRD, SEM and TPM MS analysis. Chemical composition of powders have been determined by ICP analysis and the degree of substitution of Calcium atoms by alkaline metals depends on CO32-/PO43- molar ratio in initial solutions. The differences in the formation of γ-induced defects in (Na, CO3)- and (K, CO3)-containing apatites have been found using EPR spectroscopy.

Partial Substitution of Potassium with Sodium in the K2Ti2(PO4)3 Langbeinite‐Type Framework: Synthesis and Crystalline Structure of K1.75Na0.25Ti2(PO4)3

Abstract The interaction of TiN with Na2O–K2O–P2O5 melts was investigated at (Na+K)/P molar ratios of 0.9, 1.0, and 1.2 and at Na/K molar ratios of 1.0 and 2.0. Interactions in the system led to the loss of nitrogen and the partial loss of phosphorus and resulted in the formation of KTiP2O7 and langbeinite‐type K2−xNaxTi2(PO4)3 (x=0.22–0.26) solid solutions over the temperature range of 1173 to 1053 K. The phase compositions of the obtained samples were determined by using X‐ray diffraction (including Rietveld refinement), scanning electron microscopy (using energy‐dispersive X‐ray spectroscopy and element mapping), FTIR spectroscopy, and thermogravimetric analysis/differential thermal analysis. K1.75Na0.25Ti2(PO4)3 was characterized by single‐crystal X‐ray diffraction [P213 space group, a=9.851(5) Å]. The 3D framework is built up by TiO6 octahedra and PO4 tetrahedra sharing all the oxygen vertices with the formation of cavities occupied by K(Na) cations. Only one of the two crystallographically inequivalent potassium sites is partially substituted by sodium, and this was confirmed by calculating the bond‐valence sum. The thermodynamic stability of K1.75Na0.25Ti2(PO4)3 crystals and the preferable occupation sites of NaK cationic substitutions were investigated by DFT‐based electronic structure calculations performed by the plane‐wave pseudopotential method.

Crystal structure of langbeinite-related Rb0.743K0.845Co0.293Ti1.707(PO4)3.

Single crystals of the langbeinite-related phosphate Rb0.743K0.845Co0.293Ti1.707(PO4)3 have been prepared by crystallization of high-temperature self-flux K2O–Rb2O–P2O5–TiO2–CoO.

The solid solution K3.84Ni0.78Fe3.19(PO4)5

The title compound, tetrapotassium tetra[nickel(II)/iron(III)] pentakis(orthophosphate), K3.84Ni0.78Fe3.19(PO4)5, has been obtained from a flux. The structure is isotypic with that of K4MgFe3(PO4)5. The three-dimensional framework is built up from (Ni/Fe)O5 trigonal bipyramids with a mixed Fe:Ni occupancy of 0.799 (8):0.196 (10) and isolated PO4 tetrahedra, one of which is on a general position and one of which has -4.. site symmetry. Two K+ cations are statistically occupied and are distributed over two positions in hexagonally shaped channels that run parallel to [001]. One K+ cation [occupancy 0.73 (3)] is surrounded by nine O atoms, while the other K+ cation [occupancy 0.23 (3)] is surrounded by eight O atoms.