Vol 61, No 2 (2016)

Calcium phosphate coatings consisting of magnesium oxide and hydroxyapatite, which accelerates osteogenesis (bone formation), were formed on magnesium alloys of the Mg–Mn–Ce and Mg–Zn–Zr systems by plasma electrolytic oxidation (PEO). The phase and elemental composition, morphology, and anticorrosion properties of the coatings were studied. Approaches to the formation of composite protective coatings on the basis of the PEO layer using superdispersed polytetrafluoroethylene were developed. Treatment of the PEO-coating with a polymer material reduces the adverse effect of different-level defects. After a single polymer deposition, corrosion protection effect of the composite layer substantially (by more than three orders of magnitude) increases with respect to the base PEO coating.

Ultra-high-temperature ceramic materials based on zirconium and hafnium borides were obtained by spark plasma sintering. The samples were thermal-shock tested on a gas-dynamic setup in an oxidizing atmosphere; the temperature on the surface of the samples was 2100°C. The microstructure of the samples after sintering and gas-dynamic tests was studied by electron microscopy, X-ray tomography, and elemental analysis.

Thermal decomposition of Ln₂(C₂O₄)₃ · 9H₂O concentrate (Ln = La, Ce, Pr, Nd) in the presence of CaC₂O₄ · H₂O was studied by X-ray diffraction, thermogravimetry, and chemical analysis. Annealing at temperatures above 374°C in the absence of calcium oxalate gives rise to the solid solution of CeO₂-based rare-earth oxides. Calcite CaCO₃ is formed in the presence of calcium oxalate at annealing temperatures above 442°C, which impedes the formation of lanthanide oxide solid solution and favors crystallization of oxides as individual La₂O₃, CeO₂, Pr₆O₁₁, and Nd₂O₃ phases. An increase in temperature above 736°C is accompanied by decomposition of calcium carbonate to give rise to an individual CaO phase and an individual phase of CeO₂-based lanthanide oxide solid solution.

[Ln(H₂O)₈][Cr(NCS)₆] · 5H₂O aqua complexes, where Ln = Er (1), Lu (2), have been found in an aqueous solution instead of binary complex salts with an organic ligand in their cation, when crystal products of the reaction between Ln(NO₃)₃ · 6H₂O (Ln = Er, Lu), K₃[Cr(NCS)₆] · 4H₂O, and 8-oxyquinoline (C₉H₇NO) were studied by X-ray diffraction. Crystals of complexes 1 and 2 are isostructural and crystallize in triclinic system, space group P\(\bar 1\), Z = 2. For complex 1: a = 9.0677(4) Å, b = 9.3115(4) Å, c = 16.9595 Å, α = 81.526(2)°, β = 86.153(2)°, γ = 83.879(2)°, V = 1406.33(10) ų, ρ_calc = 1.894 g/cm³; for complex 2: a = 9.0438(3) Å, b = 9.2880(3) Å, c = 16.9181(3) Å, α = 81.7250(10)°, β = 86.1600(10)°, γ = 83.8850(10)°, V = 1396.38(7) ų, ρ_calc = 1.926 g/cm³.

The ionic complexes [Ph₄Sb · DMSO]₂[OsBr₆] (I) and [p-Tol₄Sb · DMSO][p-Tol₄Sb][OsBr₆] (II) have been synthesized by the reaction between sodium hexabromoosmate and tetraphenyl- or tetra-para-tolylstibonium bromide in dimethyl sulfoxide (DMSO). According to X-ray diffraction data, the antimony atoms in [Ph₄Sb · DMSO]⁺ and [p-Tol₄Sb · DMSO]⁺ cations have a distorted trigonal bipyramidal coordination, and the pseudo-axial CSbO and pseudo-equatorial СSbС angles are 173.7(2)°, 172.8(3)° and 111.3(2)°‒121.8(2)°, 107.4(3)°‒120.3(3)°, respectively. In the tetrahedral [p-Tol₄Sb]⁺ cation, the СSbС angles are 106.1(4)°‒111.3(4)°. In the octahedral [OsBr₆]^2‒ anions, the Os‒Br bond lengths are 2.4765(6)‒2.4981(6) Å (I) and 2.4795(11)‒2.5063(11) Å (II); the trans-BrOsBr angles are 180.00(2)° (I) and 178.83(4)°‒179.34(4)° (II).

The thermodynamic and geometric parameters of isomeric macrotricyclic Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) complexes that can form upon the complexation of the corresponding hexacyanoferrates( II) with thiooxamide H₂N–C(=S)–C(=O)–NH₂ and glyoxal HC(=O)–CH(=O) in gelatin-immobilized matrices have been calculated by the OPBE/TZVP DFT method with the use of the Gaussian09 program package. It has been found that a complex with the MN₄ chelate core is most stable for M = Mn, Fe, Co, Ni, and Zn, and the MN₂S₂ core is most stable for M = Cu. Bond lengths and bond angles have been reported, and it has been noted that in all complexes, except the Zn(II) one, the chelate core and three fivemembered chelate rings are almost planar.

Samples of BaFe₁₂O₁₉ with high multiferroid properties at room temperature (maximum polarization P_m = 48.0–9.5 μQ/cm², residual polarization P_r = 28.0–29.5 μQ/cm², and electric coercive field Е_c = 115–120 kV/m) have been obtained for the first time using a modified ceramic technology (based on highpurity raw materials and sintering in an oxygen atmosphere with a B₂O₃ addition). A mechanism for the explanation of the multiferroid properties obtained has been suggested; the large practical importance of the results obtained is noted.

A novel series of Mn^III complexes with 5,10,15,20-tetra(p-tolylporphine) and 1,6-diaminohexane has been synthesized. These complexes have been characterized by UV/Vis, IR, ESI-mass spectra, elemental analysis, conductivity and magnetic susceptibility measurements. These Mn^III porphyrins exhibited a blue shift in soret band in comparison to non-metallated porphyrins. The molar conductance values of these complexes show their non-electrolytic nature in ethanol. The tentative structures have also been proposed. All the complexes have good level of water solubility due to which they may have medicinal as well as other valuable biological applications.

The complexation reactions between the yttrium(III) cation and (4-chlorophenyl, phenyl, 4-nitrophenyl, 4-methoxyphenyl, 4-methylphenyl) 9-substituted 1,8-dioxo-octahydroxanthene were studied in acetonitrile (AN) and methanol (MeOH) at different temperatures using the electrical conductivity measurements. The conductance data show that the stoichiometry of all formed complexes between the Y³⁺ cation and the studied ligands is 1: 1 [ML]. The order of stability of the complexes formed between the organic ligands and Y³⁺ cation in pure MeOH at 45°C was found to be: (3,6,6-Tetramethyl-9-(4-chlorophenyl)-1,8- dioxo-octahydroxanthene·Y³⁺) > (3,6,6-Tetramethyl-9-(4-methoxyphenyl)-1,8-dioxo-octahydroxanthene · Y³⁺) > (3,6,6-Tetramethyl-9-(4-phenyl)-1,8-dioxo-octahydroxanthene·Y³⁺) ≈ (3,6,6-Tetramethyl-9-(4- nitrophenyl)-1,8-dioxo-octahydroxanthene·Y³⁺) > (3,6,6-Tetramethyl-9-(4-methylphenyl)-1,8-dioxooctahydroxanthene ·Y³⁺). The values of the standard thermodynamic parameters (ΔH_c^°, ΔS_c^°) for formation of the complexes were obtained from temperature dependence of the formation constants of the complexes using the van’t Hoff plots. The experimental results show that the thermodynamics of the complexation reactions is influenced by the nature of solvent system and in most cases, the complexes are entropy stabilized.