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The macrokinetic features and phase and structure formation mechanisms are investigated in the Zr-Ta-Si-B system in the framework of the fractal theory of combustion. The reaction mechanisms are explored using ab initio grand potential modeling and Ellingham diagrams and then verified via direct in situ time-resolved XRD and quenching of combustion fronts in a copper block. The tendency of the Zr-TaSi-B system to form tantalum boride Ta3B4 and a transient tantalum silicide Ta5Si3 and release elemental Si and Zr in the combustion front is suggested based on the developed models and verified using a quenched combustion front and timeresolved XRD analysis. Investigation of hot-pressed combustion products shows that despite slightly higher relative density, TaSi2-rich ceramics have relatively lower mechanical properties and oxidation resistance under plasma torch as compared to single-phase (Zr,Ta)B2 solid solution.

This work describes the influence of VK carbonyl iron powder on the properties of 60Kh2N steel powder. It has been demonstrated that addition of the VK powder to sprayed powder of grade PZhRV 2.200.26 in an amount up to 15% makes it possible to increase the tensile strength from 417 to 482 MPa because carbonyl iron in combination with carbonyl nickel powder in coarse pores between the particles of sprayed iron forms a sintered frame, which positively influences the strength of the obtained material. The mechanical properties of this steel have been improved by hot rolling with subsequent annealing in a protective environment. As a consequence of this additional treatment, the ultimate tensile strength reached 595 MPa.

In this paper we present the results of studies of the effect the state of grain boundaries formed in consolidation of beryllium powders by vacuum hot pressing has on the strength properties of sintered beryllium. The dependences of the morphology, elemental composition, and structure of the dispersed strengthening phase, beryllium oxide, on the content of low-melting impurities at the grain boundaries of sintered beryllium were studied using scanning electron microscopy and X-ray microspectral analysis. A new hypothesis that explains the difference in the morphology and structure of reinforcing particles based on the features of the transition of amorphous beryllium oxide to the crystalline state (devitrification) at grain boundaries of metallic beryllium is proposed. It has been theoretically substantiated and experimentally confirmed that the devitrification mechanism can be homogeneous or heterogeneous, depending on the content and ratio of silicon and aluminum impurities. This difference determines the formation of either finely dispersed high-strength reinforcing particles of beryllium oxide or large and less strong oxide clusters. Changes in the morphology and structure of reinforcing oxide particles at the grain boundaries of metallic beryllium, in turn, affect the dynamics of grain growth in the beryllium microstructure during vacuum hot forming processes and, ultimately, the effect of grain-dispersed hardening of sintered beryllium. The results of testing the mechanical properties of industrial hot-pressed blanks of powders with fineness less than 56 μm to determine the effect of various factors (impurity content, their ratio, and particle size of the initial powders) on the strength properties of hot-pressed beryllium are statistically processed. The adequacy of the regularities is estimated using the coefficients of the approximation accuracy, which confirms the conclusions of the theoretical and experimental analyses of the studied problem. One complex indicator of the initial powder quality which makes it possible to predict the strength properties of hot-pressed beryllium is validated based on the statistical studies. The results substantiate new possibilities for controlling the mechanical properties of sintered beryllium for various purposes.

The paper presents the results of studying the effect of the state of grain boundaries (formed in the consolidation of beryllium powders by vacuum hot pressing on the strength properties of sintered beryllium. Scanning electron microscopy and X-ray spectral microanalysis were used to study the dependences of the morphology, elemental composition and structure of a dispersion hardening phase - beryllium oxide – on the content of low-melting impurities at the grain boundaries of sintered beryllium. A new hypothesis is proposed to explain the difference in the morphology and structure of reinforcing particles based on the transition features of amorphous beryllium oxide to a crystalline state (devitrification) at the grain boundaries of metallic beryllium. It is theoretically substantiated and experimentally confirmed that the devitrification mechanism can be homogeneous or heterogeneous depending on the content and ratio of silicon and aluminum impurities. This difference leads to the formation of either finely dispersed high-strength reinforcing particles of beryllium oxide or large, lower-strength oxide clusters. Changes in the morphology and structure of reinforcing oxide particles at the metallic beryllium grain boundaries, in its turn, influence the dynamics of beryllium microstructure grain growth during vacuum hot forming and, ultimately, the effect of dispersed grain-boundary hardening of sintered n beryllium. The paper provides the statistically processed results of testing the mechanical properties of industrial hot-pressed blanks produced of less than 56 μm powders to determine the effect of various factors (the content of impurities, their ratio and particle size of the initial powders) on the strength properties of hot-pressed beryllium. The adequacy of the obtained regularities was evaluated using the approximation confidence coefficients and confirmed the conclusions made in the theoretical and experimental analysis of the research problem. The statistical studies substantiated a comprehensive quality indicator of initial powders in order to predict the strength properties of hot-pressed beryllium. The results obtained substantiate new possibilities for controlling the mechanical properties of sintered beryllium for various purposes.

This article discusses the influence of carbonyl iron powder, grade VK, on compactability, sintering, and mechanical properties of samples made of atomized iron powder, grade PZhRV 2.200.26, produced on commercial scale in Russia. It is demonstrated that the relative density of compacted samples made of dispersed PZhRV 2.200.26 iron powder can be increased by addition of particles of carbonyl iron powder, grade VK, which are predominantly located in pores between the particles of atomized powder. Additional introduction of solid lubricants in PZhRV 2.200.26 and VK mixture does not lead to further increase in relative density of pressed samples (more than 90%). It is established that addition of the VK carbonyl powder to the atomized PZhRV 2.200.26 powder in the amount of 15–20 wt % atomized the bending strength of green compacted pieces because of difficulties of plastic deformation of atomized particles into pores, but it increases the bending strength of the material after sintering owing to more developed contacts.

Coatings in the Ta-Zr-Si-B-C-N system were produced by magnetron sputtering of a TaSi2-Ta3B4-(Ta,Zr)B2 ceramic target in the Ar medium and Ar-N2 and Ar-C2H4 gas mixtures. The structure and composition of coatings were studied using scanning electron microscopy, glow discharge optical emission spectroscopy, energy-dispersion spectroscopy, and X-ray diffraction. Mechanical and tribological properties of coatings were determined using nanoindentation and pin-on-disk tests using 100Cr6 and Al2O3 balls. The oxidation resistance of coatings was evaluated by microscopy and X-ray diffraction after annealing in air at temperatures up to 1200 &deg, C. The reactively-deposited coatings containing from 30% to 40% nitrogen or carbon have the highest hardness up to 29 GPa and elastic recovery up to 78%. Additionally, coatings with a high carbon content demonstrated a low coefficient of friction of 0.2 and no visible signs of wear when tested against 100Cr6 ball. All coatings except for the non-reactive ones can resist oxidation up to a temperature of 1200 &deg, C thanks to the formation of a protective film based on Ta2O5 and SiO2 on their surface. Coatings deposited in Ar-N2 and Ar-C2H4 demonstrated superior resistance to thermal cycling in conditions 20-T&minus, 20 &deg, C (where T = 200&ndash, 1000 &deg, C). The present article compares the structure and properties of reactive and &ldquo, standard-inert atmosphere&rdquo, deposited coatings to develop recommendations for optimizing the composition.

—The optimum modes of spark plasma sintering (SPS)—temperature, time, and pressure amplification—were determined; the structure and properties of blanks of boron carbide sintered by the above method from the powders obtained by the mechanochemical synthesis from carbon char and amorphous boron, by self-propagating high-temperature synthesis (SHS), and by the carbon reduction technique were studied. The optimum modes of the spark plasma sintering of the powder mix of carbon char and amorphous boron were determined.

Electrospark treatment of OT4-1 titanium alloy was performed sequentially with a hard-alloy electrode STIM-20H (TiC—20% Ni) and carbon-containing material (graphites and carbon-based composite materials). Phase composition and relief of the coatings formed were analyzed. It was established that with regard to the applied carbon-containing material, the electrospark treatment can decrease the friction coefficient of the coatings and increase wear- and heat resistance of the titanium alloy.

Electrospark treatment of OT4-1 titanium alloy was performed sequentially with a STIM-20N hard-alloy electrode (TiC–20% Ni) and carbon-containing material (graphite and carbon-based composite materials). Kinetics of the mass transfer of the hard-alloy electrode was studied. The cathode mass loss during the first minute of the treatment was established. The kinetics results were processed using the methods of mathematical statistics. The erosion resistance of the applied carbon-containing materials was determined. Phase composition and relief of the coatings formed were analyzed. It was found that the application of the carbon-containing material increases the content of refractory phases in the coatings. Increase in the time of the treatment using the carbon-containing materials decreases the roughness of the coatings.

Recently it has become a trend to set up academic and education clusters in different industries of economy and education. Education cluster priorities are the quality of education, its continuity, succession, accessibility, competitiveness. The article researches the necessity to project innovation infrastructure covering education institutions, private and state-owned enterprises. The authors provide examples and show prospects of setting-up an education cluster in the oil and gas industry. Integration, combination and coordination of efforts of separate education structure, enterprises, research institutes in education and industrial cluster could help society reach stable, sustainable development.

The article is devoted to studying the effect of introduced strengthening nanosize particles on composite material (CM) structure. The nature of strengthening particle distribution, the distance between dispersed particles, and the size of a critical nucleus are determined. It is shown that use of centrifugal forces in a crystallizing field provides uniform particle distribution within a matrix with predominant arrangement of particles within grains. The critical nucleus radius determined during crystallization in a centrifuge of CM based on aluminum shows that the critical nucleus radius is close to that of strengthening nanoparticles. A version is proposed for production parameters making it possible to obtain a critical nucleus with a size markedly greater than that of added particles.

A simplified model of cooling long insulated pipelines with liquid hydrogen flowing through them has been developed. The model allows us to determine the flow parameters at different points in time and to estimate the pipeline cooling time. When developing the model, the following assumptions were made: the linear velocities of the liquid and vapor are equal, the phases are in a state of thermodynamic equilibrium, the dependencies obtained for a single-phase flow are applicable to determine the friction coefficient of a two-phase flow. Based on the model, an automated algorithm for calculating the cooling process of a long pipeline with cryogenic components was developed. It allows us to obtain data for plotting the temperature fields of the pipeline walls and the flow of the transported cryogenic liquid at different times, as well as to determine the cooling time of the pipeline and the moment of the onset of a stationary single-phase flow. The calculation results are in good agreement with the experimental data.

Doppler ultrasound dynamic in interlobar arteries allows indirectly assess arterial blood flow component intraorganic, state microvasculature of kidneys when they are damaged on the background of endotoxemia, as well as state of the peripheral vascular bed of the kidney and the degree of functional disorders in acute pancreatitis. Hemodynamics indicators in renal interlobar arteries in conjunction with standard laboratory methods to help in determining the extent of kidney damage in acute pancreatitis and its destructive forms.

The peculiarities of the influence of nanodimensional additives of WC, ZrO2, and micrometer particles of hexagonal BN on the compression ratio under cold pressing of briquettes, shrinkage under the solid-phase sintering, and mechanical properties (bending strength limit and hardness) of powder alloys in the Cu–Fe–Co–Ni system are investigated. It is shown that the introduction of alloying additives of WC, ZrO2, and hexagonal BN insignificantly affect the charge resistance to compaction under cold pressing, while they are an additional diffusion barrier in the course of sintering increasing the activation energy. An increase in hardness to 7 HRB and strength to 200 MPa are attained due to the implementation of the effect of dispersed reinforcement in a compact composite.

The influence of alloying additives Al(OH)3 and TiO2 on the structure and properties of uranium dioxide fuel pellets is investigated. It is established that their introduction improves the characteristics of the macrostructure and microstructure of fuel pellets and positively affects their properties. For example, the grain size in the fuel pellet increases to 39 mm (instead of 10–15 mm in the case of usual technology), the number of large (>10 mm) pores decreases, and the strength and thermal conductivity increase slightly.

Based on the results of experiments on the introduction of a molybdenum-containing organometallic compound (Mo-MO) into the powder of R-10 grade carbonyl iron, it is shown that it can be used in principle as the plasticizer. It is established that the introduction of the Mo-MO compound into the carbonyl iron powder activates its sintering due to the fact that the growth of the contact necks intensifies. The gluing strength of the samples obtained using the Mo-MO compound is higher than with the addition of synthetic rubber (SR). The increased gluing ability of the Mo-MO compound in comparison with SR makes it possible to decrease the volume fraction of the plasticizer in the powder mixture by a factor of approximately 1.5.

Comparative characteristics of the lithological composition of estuarine incised valley fill, as well as the enclosing and overlying storm-related deltaic sediments (beds VK1, VK2, and VK3), in the productive part of the Vikulovo Formation (upper Aptian), Kamenny area, West Siberia are given. It is shown that the incised valley fill-reservoirs, which are characterized by a coarser structure, inferior sorting, lower mineral maturity, and predominant kaolinitic clayey cement, demonstrate higher filtration properties.

The morphology of the surface and fracture of highly porous materials obtained during the thermal destruction of metalorganic mixtures (MOM) was investigated. The size and shape of pore channels in the finished product were shown to be determined through the fractional composition and the particle shape in MOMs. The effect of the porosity on the permeability and strength of sintered materials was considered. The permeability was demonstrated to depend not only on the value, but also on the shape of pore channels. Combining the techniques of powder metallurgy with chemical-metallurgical processes allows us to obtain materials with a porosity of 70–80% and a strength of no less than 5–25 MPa. If the pore size was from 10 to 100 µm, the permeability of materials was (in 10−12 m2) 1–3 for Mo, 0.5–6 for Mo-Ni, and 2–6 for Ti-Mo.

The possibility of manufacturing the highly porous materials from refractory metals (Mo, Mo-Ni, and Ti-Mo) while combining the techniques of powder metallurgy with chemical-metallurgical processes is considered. The formation of metallic nanostructures at the surface of powder particles immediately in the course of sintering the moldings is found. These nanostructures are capable of activating the sintering process for compositions based on Mo, Mo-Ni (50/50), and Ti-Mo (85/15) and provide the formation of highly porous (70–80%) materials at 1000°C.

A model for describing hopping thermopower is proposed. Within the model, the majority and compensating impurities form a simple cubic lattice in a crystal matrix. The thermopower associated with hole (electron) hopping over hydrogen-like impurities is calculated with inclusion of their excited states. The results of calculations are compared with available experimental data on the low-temperature thermopower of Ge: Ga and the specific heat of Si: P in the dielectric region of the insulator-metal transition.

Expressions for the screening length and the ambipolar diffusion length are derived, for the first time, for the case where hopping conduction and band conduction coexist in semiconductors with hydrogen-like impurities. A method is proposed for calculating the diffusion coefficient of electrons (holes) hopping between impurity atoms from data on the Hall effect, in the case where the hopping and band conductivities are equal. An interpretation is given of available experimental data on hopping photoconduction between acceptors (Ga) and donors (As) in p-Ge at T=4.2 K doped by a transmutation method. It is shown that the relative magnitude of the mobilities of electrons hopping between donors and holes hopping between acceptors can be found from the hopping photoconductivity measured as a function of the intensity of band-to-band optical carrier excitation.

A derivation of the equation for the hopping current of electrons and holes (electron vacancies) among impurities of a single species in three charge states [(−1), (0), and (+1)] is given in the continuum approximation. The screening length of an electrostatic field and the diffusion length of charge carriers are calculated. The dependence of the effective lifetime of electrons hopping among impurities relative to (−1)→(+1) transitions [and of holes relative to (+1)→(−1) transitions] on the degree of compensation and the rate of interimpurity photoexcitation, which stimulates the formation of ions, is obtained. The calculations of the dependence of the hopping photoconductivity on photoexcitation rate are consistent with known experimental data, which have not previously found a theoretical explanation.

It is shown for the first time that the observed [Phys. Lett. A 162 (1992) 105] potential difference Phi_t between the resistor and the screen surrounding the circuit is caused by polarization of the resistor because of the kinetic energy of the electrons of the superconducting coil. The proportionality of Phi_t to the square of the current and to the length of the superconducting wire is explained. It is pointed out that measuring Phi_t makes it possible to determine the Fermi quasimomentum of the electrons of a metal resistor., Comment: 2 pages, 1 figure

A model of hopping conduction between nearest neighbors is developed in which the majority and compensating dopant atoms are assumed to form a unified simple cubic lattice in a crystalline matrix. The hopping of carriers occurs when thermally activated “equalization” of majority impurity levels takes place, while the compensating impurities block the corresponding sites. The range of relatively high temperatures is considered in which the interactions giving rise to a Coulomb gap can be neglected and the density of states of the majority impurity band is Gaussian. The concentration dependences of the activation energy for hopping conductivity ɛ 3 (nonmonotonic and having a maximum) and the preexponential factor σ3 are found. The results are compared with experimental data obtained by different authors for neutron-doped Ge: Ga.

Within first order perturbation theory the time of electron-ion interaction is assumed to be equal to the time of an electron passing through the crystal region related to one impurity ion. In terms of the relaxation time approximation for nondegenerate semiconductors the mobility μ i , limited by elastic ion scattering, is shown to be proportional to T/N 2/3 ; the Hall factor is equal to 1.4. Calculated for various temperatures T the majority carrier mobility dependences on the doping impurity concentration N are in good agreement with known experimental data. It is shown that the Brooks-Herring formula for μ BH T 3/2 /N overestimates the value of mobility. Comparison of mobility calculation in degenerate crystals with experiments also yields μ BH .