Inorganic Materials最新文献

Thermodynamic properties of polycrystalline powders of ruthenium dichalcogenides have been studied using calorimetric isobaric heat capacity measurements in a wide temperature range. The adiabatic and differential scanning calorimetry data for ruthenium disulfide and ruthenium diselenide have been used to determine standard thermodynamic functions (heat capacity, entropy, enthalpy increment, and reduced Gibbs energy) of these compounds in the range 10–965 K. At 298.15 K, the functions of RuS₂ are as follows: (C_{p}^{^circ }) = 60.82 ± 0.12 J/(K mol), S° = 56.05 ± 0.11 J/(K mol), Н°(298.15 K) − Н°(0) = 9.75 ± 0.02 kJ/mol, and Ф° = 23.34 ± 0.05 J/(K mol). For RuSe₂, we have obtained (C_{p}^{^circ }) = 69.96 ± 0.14 J/(K mol), S° = 80.62 ± 0.16 J/(K mol), Н°(298.15 K) − Н°(0) = 13.05 ± 0.03 kJ/mol, and Ф° = 36.85 ± 0.08 J/(K mol). The data obtained above 298 K have been used to determine empirical coefficients of the Maier–Kelley and Khodakovsky equations. The absolute entropies obtained in this study for the ruthenium dichalcogenides, in combination with literature data, have made it possible to evaluate the Gibbs energy of formation of RuS₂(cr) and RuSe₂(cr) at 298.15 K.

In this paper, we report a theoretical study of the electronic structure of copper oxides. The band structure of the copper oxides Cu₂O and CuO has been calculated in the density functional approach by the full-potential linearized augmented plane wave method, using the modified Becke–Johnson (mBJ) potential. The results demonstrate that the use of the modified Becke–Johnson potential ensures better agreement of band structure calculation results for the copper oxides with experimental data then does the generalized gradient approximation (GGA). The use of the mBJ potential allows both compounds to be described as semiconductors whose band structure parameters are in qualitative agreement with experimental data. We have calculated copper L₃-edge and oxygen K-edge X-ray absorption near edge structure spectra of Cu₂O and CuO at different occupancies of the core level from which an electron transition occurs and compared the calculation results with experimental data.

Ni–Al–Co alloy with the composition 45 wt % Ni + 41 wt % Co + 14 wt % Al has been prepared for the first time by aluminothermic reaction. The phase composition of the synthesized alloy comprises a cubic (Ni,Co)₃Al solid solution of cobalt in nickel aluminide (γ'-phase) and a tetragonal (Ni,Co)₃Al phase. The formation of the tetragonal structure of (Ni,Co)₃Al is due to a martensitic transformation of a supersaturated initial structure in grains of the cubic (Ni,Co)₃Al phase. The intragranular microhardness of the synthesized alloy is 6500 MPa. The alloy has soft magnetic properties, with the highest magnetization of 27 emu/g in a magnetic field of 10 kOe.

In this paper, we examine the purity level and impurity composition of the titanium, zirconium, and hafnium samples at the Exhibition–Collection of Extrapure Substances and present estimates of the average and total concentrations of elemental impurities in the purest samples. We examine the impurity composition of the array of the group 4 elements and contributions of particular groups of impurities and discuss the purity level of the group 4 elements and their compounds manufactured in Russia and abroad.

A ternary molybdate with the composition KBаLu(MoO₄)₃ and a monoclinic scheelite-like structure has been synthesized. Codoping KBаLu(MoO₄)₃ with Er³⁺/Yb³⁺ ions, we have obtained an upconversion phosphor exhibiting anti-Stokes luminescence in the range 400–700 nm under IR excitation. The synthesized phosphor has been characterized by X-ray diffraction, differential thermal analysis, and vibrational spectroscopy, and its IR, Raman, and luminescence spectra have been measured.

We have studied the effect of the composition of starting Mg_{1 – х}Ni_х(OH)₂ nanoplates on the formation of (Mg_{1 – х}Ni_х)₃Si₂O₅(OH)₄ nanoscrolls under hydrothermal conditions and determined the structure, morphology, size parameters, and specific surface area of the synthesized nanopowders based on (Mg_{1 – х}Ni_х)₃Si₂O₅(OH)₄ hydrosilicates with the chrysotile structure. The thermodynamically driven dehydration of the starting (Mg_{1 – х}Ni_х)(OH)₂ hydroxide with х ≳ 0.4 during hydrothermal treatment of a mixture of magnesium nickel hydroxide nanoplates and silica gel (SiO₂∙nH₂O) particles dispersed in an aqueous sodium hydroxide solution has been shown to play a key role in determining the formation and structural characteristics of (Mg_{1 – х}Ni_х)₃Si₂O₅(OH)₄ nanopowders with tubular structure.

Temperature dependences of lattice parameters for AgInSe₂ single crystals have been used to determine their thermal expansion coefficients along the a and c crystallographic axes. The results demonstrate that the thermal expansion coefficients of the AgInSe₂ single crystals in the a- and c-axis directions change sign at temperatures of 142 and 135 K, respectively. Analysis of the temperature-dependent band gap of AgInSe₂ with the use of optical absorption spectra shows that its band gap increases with increasing temperature in the range 80–120 K and decreases in the range 120–300 K.

In this paper, we report the conditions and results of the synthesis of solid solutions and flux growth of single crystals with the general formula La_{1 − x – y}Tb_xEu_yMgB₅O₁₀ from a K₂Mo₃O₁₀-based high-temperature solution. The structural properties, composition, thermal characteristics, Tb³⁺ and Eu³⁺ luminescence spectra, and excitation spectra of the solid solutions have been studied in the ranges 0.2 < x < 0.7 and 0.1 < y < 0.6. We have calculated CIE luminescence spectra of the single crystals and fabricated operating prototype emitters using them.

T-590 commercially available electrodes for wear-resistant claddings and STIM-2/30 electrodes prepared by self-propagating high-temperature synthesis (SHS) extrusion and containing reinforcing titanium carbide particles have been used to produce protective layers on the surface of steel by electric arc cladding. We have determined the phase composition and structure of the clad coatings. The results demonstrate that the microstructure of the coatings produced by cladding with the use of T-590 electrodes is formed by a carbide eutectic. The reinforcing TiC phase in the SHS electrodes has been shown to pass into the clad layer and be uniformly distributed across the entire clad layer, which is accompanied by the formation of an intermediate diffusion layer on the coating–substrate fusion interface. The hardness and microhardness of the clad coatings are a factor of 2–4 higher than those of the steel substrate. Cladding with the use of T-590 electrodes ensures higher hardness of the clad layers, but an increase in the percentage of ferrite in their structure can lead to a decrease in their wear resistance. The coatings produced by cladding with the use of SHS electrodes have a favorable structure capable of ensuring high abrasive wear resistance.

In this paper, we discuss general trends in the IR luminescence of colloidal PbS quantum dots 3 nm in average size, capped with thioglycolic acid molecules (PbS/TGA QDs). Treatment of the PbS/TGA QDs with a KI solution has been shown to cause a shift of a composite luminescence band peaking at 1120 nm to shorter wavelengths, to 1060 nm; an increase in the quantum yield of its shorter wavelength component, related to excitonic emission, from 1 to 10%; and quenching of its longer wavelength component, due to radiative recombination at defect levels. In this process, the cubic structure of PbS undergoes no changes. The average size of the PbS/TGA QDs has been shown to decrease slightly, by 0.2–0.3 nm. The conclusion has been drawn that the increase in the quantum yield of excitonic emission from the PbS/TGA QDs as a result of KI treatment is due to the more efficient passivation of interfacial defects, which act as both recombination luminescence and nonradiative carrier recombination channels. Using thermoluminescence in the temperature range from 80 to 350 K, we have demonstrated the presence of two types of shallow localized states, at 0.17- and 0.25-eV depths, whose density is only slightly sensitive to treatment of the PbS/TGA QDs with a KI solution. We assume that some of the traps identified are due to native defects in the nanocrystals—interstitial lead and sulfur ions—rather than to dangling bonds of surface lead and sulfur atoms.