Vol 7, No 3 (2016)

Using the data on the quantum states and mechanisms of the interaction of an impurity hydrogen atom with metals, the over-barrier hopping of hydrogen at high temperatures is studied. It is shown that anharmonicity of the hydrogen atom vibrations affects the relaxation processes as a result of the interference with phonon scattering.

The effects of powerful pulsed ion and high-temperature plasma fluxes generated in a plasma focus (PF) device and the effect of free running laser radiation on a corundum (α-Al₂O₃) ceramic produced by powder technology are studied. The power flux density q and acting pulse time τ for plasma stream, ion flux, and laser irradiation were q_p ≈ 10⁷ W/cm² and τ_p ≈ 100 ns, q_i ≈ 10⁸ W/cm² and τ_i ≈ 20 ns, and q_l ≈ (3–5) × 10⁵ W/cm² and τ_l ≈ 0.7 ms, respectively. The resistance of the ceramic to pulsed energy fluxes was estimated by the weight loss of irradiated specimens and by the surface layer defects (damage). The combined use of PF and pulsed laser irradiation is shown to allow simulation of the extreme erosion and damage of materials in thermonuclear fusion facilities (such as ELM effects in ITER or at the first wall of inertial confinement chambers).

Equilibrium energy and technological characteristics of the plasma synthesis of titanium nitride, carbide, and carbonitride, in particular, the composition and yields of final products, energy consumption upon their production, and the required enthalpy of a plasma flow, are calculated for the following reactions: TiCl₄ + xH₂ + yN₂ (synthesis of TiN), TiCl₄ + xH₂ + zC_mH_n (synthesis of TiC), and TiCl₄ + xH₂ + y₁N₂ + z₁C_mH_n (synthesis of TiCN). The calculations are carried out for the temperature range from 500 to 4000 K, at the total pressure of 0.1 MPa in the system, and with the following molar ratios of reagents: x = 8, x = 20; y = 0.5, y = 5, y = 20; z = 0.9, z = 1.0, z = 1.1; y₁ = 5; z₁ = 0.4, z₁ = 0.5, z₁ = 0.6.

By employing an open-air plasma dynamic synthesis technique in a coaxial magnetoplasma accelerator, ultrafine copper oxide powders are produced. Using the methods of SEM, TEM, XRD structural analysis, and IR spectroscopy, it is shown that annealing in air at temperatures up to 800°C results in changes in the phase composition of the powder, as well as in the formation of a nanodispersed product whose main crystalline phase is copper oxide CuO.

Features of the formation and structure of plasma ceramic coatings sprayed with composite powders based on alumina and zirconia plated with nickel and aluminum are studied. The porosity and thermal conductivity of the coatings and the microhardness of the phase components are measured. It is found that a decrease in the thermal conductivity of the composite coatings caused by a decrease in the metal phase content with increasing plasmatron arc power is compensated by an increase thereof owing to a decrease in the coating porosity, which neutralizes the net effect of the arc power on the thermal conductivity of metal–ceramic coatings.

Four types of three-dimensional plasma capillary-porous titanium coatings for model intraosseous implants are developed. By means of pulsed microplasma oxidation in solutions or plasma spraying of powders, additional bioactive coatings on the basis of calcium phosphates are deposited on the Ti coating surface. Shear strength values of the interface between the implants coated and osseous block after 16 weeks of implantation are 4.25–4.81 MPa, while for implants with additional plasma hydroxyapatite coating it exceeds 6.19 MPa after 4 weeks of implantation.

The article discusses production of composite granules by combined mechanical activation of Babbitt and reinforcing components of nano- and micrometric range, including carbon-containing components. The parameters of mechanical alloying are determined, and the structure of the obtained composite granules is analyzed.

Existing models for calculation of thermal conductivity of uranium dioxide are analyzed. Anomalous growth of the thermal conductivity coefficient of nuclear fuel in the high-temperature region is explained. Models of specific heat at constant volume and thermal conductivity are proposed. It is demonstrated that the contribution of degrees of freedom of charge carriers to the observed thermal conductivity coefficient of admixture-free stoichiometric UO₂ can be neglected up to the melting point.

A method of preparation of titanium materials with a porous surface layer by hydrostatic pressing and subsequent high-temperature sintering with use of a pore former as a temporary space holder was proposed. Comparative studies of the structure and properties of titanium materials with a porous surface layer fabricated in a new way and by the classical method of powder metallurgy (uniaxial pressing and high-temperature sintering) were carried out. It was shown that this method makes it possible to obtain porous titanium samples with preset parameters of pore space (volume fraction and pore size) and high mechanical properties. An experimental sample of an endoprosthesis element (acetabular cup) was fabricated using the proposed method.

In this work, mechanisms of aggregation of carbon nanotubes in polymer nanocomposites are studied. This class of nanofillers exhibits two types of aggregations: formation of bunches or ringlike nanotube structures. The ultrasound is found to affect only the second type of aggregation, which is manifested in a strong (almost by an order of magnitude) increase in the radius of the carbon ringlike nanotube structures. This effect occurs only below the nanofiller percolation threshold.

The nuclear gamma resonance (Mössbauer effect) is used to determine the oxidation state and the coordination environment of iron ions in model glasses that simulate vitrified high-level waste. A major fraction of iron is present in the samples with relatively low contents of transition metal oxides as Fe(III) in the octahedral oxygen environment. When the content of transition metal oxides is high, iron is distributed between a glassy phase (10–15%) and a crystalline phase (85–90%). Iron in the first phase exists predominantly as Fe(III) in the octahedral environment, while in the second phase it is present as Fe(II) and Fe(III) ions as well in a form of octahedrally coordinated and participating ions in a “fast” electron exchange proceeding as mFe³⁺ + nFe²⁺ ↔ mFe²⁺ + nFe³⁺. The leach rate of Cs ions from boron-free glasses amounts to ~1 × 10^–5 g/(cm² day) and lower, and the value for Fe is three orders of magnitude lower. Upon annealing, both the rate and the degree of leaching increase by several times, while the boron-containing glasses exhibit lower hydrolytic durability. Both the rate and the degree of leaching of iron change insignificantly after annealing.