Inorganic Materials最新文献

Nickel and aluminum powders have been deposited for the first time on steel 35 by electrospark deposition. We have studied the effect of the ratio of the Ni and Al powders in the anodic mixture on the structure, oxidation resistance, and corrosion behavior of the coatings and also on their friction coefficient and wear resistance. The results demonstrate that, as the fraction of aluminum powder in the anodic mixture increases from 30 to 70 at %, the average aluminum content of the coatings increases steadily from 39 to 63 at %, whereas the nickel content decreases from 46 to 26 at %. The use of such coatings allows the oxidation resistance of steel 35 parts at a temperature of 700°C to be raised 13 to 34 times. The most aluminum rich coating has been shown to have the highest hardness, wear resistance, and heat resistance.

A single crystal of a Pb_1−xSc_xF_2+x heterovalent solid solution with x = 0.1 (nominal composition) has been grown by vertical directional solidification (Bridgman technique), its elemental and phase compositions and crystallographic parameters have been determined, and the interrelation between its thermal and electrical conductivities has been analyzed. The composition of the solid solution has been found to vary from x = 0.08 in the bottom (cone) of the crystal to x = 0.095 in its top. The Pb_1−xSc_xF_2+x crystal has been shown to have low thermal conductivity (k = 0.7 W/(m K) at 300 K), with “glass-like” behavior of thermal transport, atypical of the crystalline state, in combination with high fluoride ion electrical conductivity (σ_dc = 0.012 S/m at 293 K) and relatively low activation enthalpy for electrical conduction (ΔH_σ = 0.378 ± 0.005 eV). The observed behavior of the thermal and electrical conductivities of the Pb_1−xSc_xF_2+x solid solution is due to structural disorder in the fluorine sublattice—which persists at room temperature—as a result of heterovalent substitutions of Sc³⁺ for Pb²⁺ cations. The thermal and electrical conductivities of single crystals of Pb_1−xSc_xF_2+x and Pb_1−xCd_xF₂ two-component solid solutions (CaF₂ structure) are compared to those of the β-PbF₂ (CaF₂ structure) and ScF₃ (ReO₃ structure) single-component fluorides.

This paper presents models of the hysteresis effects occurring on the wetting perimeter of a liquid-metal catalyst drop due to the effects caused on the contact angles by the edge of the end (tip) face of a nanowires (NW) and the linear tension of the three-phase contact interface. The contact angle hysteresis of the catalyst liquid drop on the end of an NW grown by the vapor → liquid → solid (VLS) scheme is due to its indifferent equilibrium at the wetting perimeter. The conclusion is drawn that the contact angle hysteresis in the catalyst drop wetting the NW crystal surface has a dual, not strictly equilibrium nature.

We have grown single crystals of solid solutions based on the layered compound semiconductor TlGaS₂ containing up to 2 mol % praseodymium and characterized them by X-ray diffraction. The optical absorption edge of the TlGaS₂〈Pr〉 solid solutions has been studied in the temperature range 100–200 K, and the edge exciton peak position has been determined as a function of temperature for all of the TlGaS₂〈Pr〉 compositions studied.

The vapor–liquid separation factors for the system Ni(PF₃)₄–impurities, in which the impurities include pentane (3.8 ± 0.8), hexane (1.3 ± 0.3), heptane (0.6 ± 0.2), dichloromethane (3.5 ± 0.8), trichloromethane (1.5 ± 0.3), tetrachloromethane (3.0 ± 0.7), phosphorus(III) fluoride (27.7.3 ± 7.8), and branched alkanes (2-methylpentane, 3-methylpentane, 2-methylhexane, 3-methylhexane, and 3-ethylhexane) were determined at 298 K by the static phase balancing method. The experimental data were in good agreement with the estimates of the vapor–liquid separation factors based on the conformal solution theory using Lennard-Jones potential parameters.

Composites based on poly(methylmethacrylate) (PMMA) and lead and europium salts, with the compositions PMMA/Pb(CF₃COO)₂ and PMMA/Pb(CF₃COO)₂,Eu(CF₃COO)₃, have been prepared by curing methylmethacrylate (MMA) based solutions via thermal radical block polymerization of MMA. The refractive index of MMA + Pb(CF₃COO)₂ solutions and the density of the PMMA/Pb(CF₃COO)₂ polymer composites have been shown to increase linearly as the Pb salt concentration increases to 83 wt % (40 wt % elemental Pb). The optical transmission of the composites at wavelengths above 450 nm and the highest lead and europium concentrations reaches 90% at sample thicknesses of up to 5 mm. The lead equivalent at a Pb(II) concentration of 40 wt % is 0.010. Photoluminescence in the PMMA/Pb(CF₃COO)₂,Eu(CF₃COO)₃ composites is due to Eu³⁺ electronic transitions from the ⁵D₀ metastable electron energy level to the ⁷F_j sublevels of the ground level. We have demonstrated the influence of lead(II) and europium(III) on the properties of the matrix and the influence of the matrix and Pb(II) on absorption and luminescence spectra of europium(III).

Data on the thermochemical synthesis of molybdenum carbide on the basis of the (NH₄)₆Mo₇O₂₄–NH₄NO₃–C₆H₁₂N₄ system at different component ratios have been reported. Thermodynamic computations have been performed to establish composition regions for probable exothermic reactions to produce molybdenum carbide: 10–20 moles of ammonium nitrate per 1 mole of ammonium molybdate and the ratio of reducing agent to oxidizing agent (φ) equal to 1.5–4.0. It has been found that the reaction in ammonium molybdate–ammonium nitrate–urotropin system includes several stages, the main exothermic reaction is observed after temperature of 120–180°C is reached. Molybdenum carbide forms at φ ≥ 6.5 after thermal treatment at 1000°C under inert atmosphere. The reaction leads to fine crystalline structure of particles with size of 100–200 nm. The obtained materials based on molybdenum carbide show catalytic activity in the conversion of products of incomplete combustion of biofuel (pyrolysis resins). Addition of the obtained materials to pyrolysis resin in 1/10 ratio enhances its conversion (rate parameter increases by 2–10 times), reduces average process temperature by 50–100°C, and decreases activation energy from 82 to 52–65 kJ/mol.

Abstract―Compound Cu₃NaS₂ has been prepared by solid-phase reactions from copper and sodium sulfides Cu₂S and Na₂S. It has been shown that compound Cu₃NaS₂ has hexagonal structure with lattice parameters a = 13.9398 ± 23 Å and c = 21.4637 ± 74 Å. After 6 months after synthesis, compound Cu₃NaS₂ spontaneously transforms at ambient temperature from hexagonal structure into phase with face-centered cubic (FCC) lattice. The dimension of coherent-scattering regions (CSR) for the FCC phase determined from the broadening of diffraction lines varies from ~25 nm at ambient temperature to ~110 nm at 500°C. DSC curves show anomalies at temperatures of 108 and 436°C corresponding to endothermal reversible transitions without change in the type of crystal lattice. The authors consider these anomalies to be due to redistribution of copper and sodium cations over possible crystallographic positions.

One-dimensional layered α-МоО₃ structures have been synthesized via hydrothermal treatment of peroxo molybdenum complexes. Treatment of the structures in aqueous sucrose solutions under hydrothermal conditions after drying at 80°C has been shown to cause partial reduction of their surface. The reduction process is accompanied by a change in Mo–O bond length as a consequence of distortion of the MoO₆ octahedra. Local supersaturation with reduction products in aqueous solution under hydrothermal conditions leads to the formation of new crystallization centers and growth of dumbbell-shaped particles. The forming nanostructured α-МоО₃/MoO₂ two-phase material, with two morphological species of particles, contains no carbon. Such a strategy for designing one-dimensional α-МоО₃ structures can be aimed at monitoring electrochemical degradation of high-capacity electrodes and controlling the associated deformation dynamics.

Titanium nickelide alloys have been prepared by self-propagating high-temperature synthesis compaction using equiatomic mixtures of nickel and titanium powders. The alloys were synthesized in a “sand” press die with the use of a “chemical furnace” and in a rigid press die. In the latter process, reaction mixtures were first subjected to mechanical activation (MA), which made it possible to carry out exothermic synthesis and consolidation of the synthesis products without preheating. No inert atmosphere was used in the syntheses. We obtained titanium nickelide samples 70 mm in diameter and 8 mm in thickness. The percentage of the NiTi phase has been shown to depend on the combustion temperature of the Ni + Ti powder mixture and the percentages of oxygen and hydrogen in the starting titanium powder. The largest percentage of the NiTi phase (85 vol %) was reached at a combustion temperature of 1400°C with the use of titanium containing 0.55 wt % oxygen and 0.14 wt % hydrogen. An increase in the oxygen content of the Ni + Ti powder mixture to 2.3 wt % as a result of MA leads to an increase in the content of the Ti₂Ni phase in the alloy to 53 vol %. As the hydrogen content of titanium increases to 0.6 wt %, the combustion temperature and speed decrease and free Ni remains in the alloy. The alloys with the highest content of the NiTi phase have the lowest microhardness: HV = 6.2 GPa. As the percentage of the Ti₂Ni, Ni₃Ti, and Ni₄Ti₃ phases in the alloys increases, their hardness rises to HV = 11.1 GPa.