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The tin–substituent bonds in Sn(II) organic compounds are studied by quantum chemical methods using the PC GAMESS-Firefly program package. The geometry optimization for the studied molecules is carried out by the DFT method (B3PW91functional, using the aug-cc-pVTZ-pp basis set with an effective core potential for tin and the 6-311++(2d,p) basis set for other atoms. The wave functions and the NBOs of tin–substituent bonds were calculated by the HF method using the x2c-TZVPall-electron relativistic basis set for the tin atom and the 6-311G(2d,p) basis set for other atoms. The values of topological characteristics of tin–substituent bonds are obtained by the AIM method. These bonds can be classified as “intermediate bonds” characterized by small contributions of Sn AOs in the MOs of the bonds, large differences between the charges on tin atoms, and low occupancies of the MOs of the bonds. The energies of Sn–R bonds are estimated.

Spheroidization of Fe and steel powders in a plasma stream of an DC arc plasma torch is investigated. The possibility of obtaining a product with a spherical particle content of up to 100% is established. The fluidity of the best samples of obtained powder is 13–20 s with a fluidity of the feedstock of 39 s. The bulk density of the initial powder (3.05 g/cm3) during the plasma treatment increases to 4.1–4.4 g/cm3. The nanofraction content in spheroidized powders varied from 0 to 75 wt % and it depends mainly on the enthalpy of the plasma stream, consumption of raw materials, and the organization of the flow of the plasma-forming gas in the discharge channel of the plasma torch. It is established that Fe powders spheroidized in plasma can be used in selective laser melting technology to obtain compact samples whose density reaches 7.86 g/cm3.

The effect of processing multicomponent nanopowders of the W–C system, obtained by plasma-chemical synthesis, in microwave fields with a frequency of 2.45 and 24 GHz generated using a magnetron and gyrotron, respectively, is studied experimentally. It is established that microwave processing results in the formation of nanosized particles of tungsten carbide WC. The influence of processing time on the phase, disperse, and chemical compositions of nanopowders is investigated.

Experimental studies of aluminium boride synthesis as a result of interaction of disperse aluminum with diborane B2H6 and disperse boron in a flow of thermal plasma of different composition generated in electric arc plasma torch have been carried out. Experimental work on the synthesis of aluminium boride nanoparticles from elements (a mixture of disperse aluminum and boron) has shown the possibility of obtaining in thermal plasma arc discharge of such phases of the boride as AlB12 and AlB31. The specific surface of the powders obtained is from 3 to 27 m2/g. According to X-ray phase analysis, the powders obtained, except for aluminum boride phases, also contain boron, aluminum, aluminum nitride and boric acid phases. The greatest yield of aluminum boride phases is provided by using the nitrogen plasma with hydrogen and enthalpy 4.5 kWt∙h/m3 in the reactor with increased high-temperature zone. The use of gaseous diborane made it possible to eliminate restrictions on the evaporation of boron particles but did not provide an opportunity to obtain aluminum borides in the plasma-chemical process. It was concluded that it is necessary to perform quenching of high-temperature gas flow containing boron and aluminum vapor to form aluminum borides from the gas phase in plasma-chemical synthesis. Such an approach should ensure that the temperature is reduced to the values at which aluminum borides are stable and that the formation of aluminum boride nanoparticles will occur as a result of condensation from the gas phase under these conditions.

Spatial and electronic structures of three-coordinated silicon molecules are calculated within MP2/6-311G(2d,p) and HF/6-311++G(3df,3pd) methods using the PC GAMESS-Firefly software package. AIM and NBO methods are used to determine main characteristics of silicon-substituent bonds in these molecules. Topologically, Si-C, Si-N, Si-Cl, and Si-O bonds may be characterized as “intermediate” bonds, and Si-Si bonds are characterized as covalent bonds.

The possibility of obtaining composite micropowders of the W-C-Co system with a spherical particle shape having a submicron/nanoscale internal structure was experimentally confirmed. In the course of work carried out, W-C-Co system nanopowders with the average particle size of approximately 50 nm were produced by plasma-chemical synthesis. This method resulted in the uniform distribution of W, Co and C among the nanoparticles of the powder in the nanometer scale range. Dense microgranules with an average size of 40 microns were obtained from the nanopowders by spray drying. The spherical micropowders with an average particle size of 20 microns were received as a result of plasma treatment of 25.36 microns microgranule fraction. The spherical particles obtained in the experiments had a predominantly dense microstructure and had no internal cavities. The influence of plasma treatment process parameters on dispersity, phase, and chemical composition of spherical micropowders and powder particles microstructure has been established.

A comparative study of the results of Spark-Plasma Sintering (SPS) of two-types of aluminum oxide nanopowders, obtained by the method of conductor explosion and plasma synthesis. When the parameters of both powders are similar (spherical form of the particles, size, phase composition) as well as SPS modes the properties of the resulting compacts are significantly different both in mechanical properties and microstructure. The reason of differences in the properties of the obtained compacts is in technological impurities in powders, obtained by different methods. Artificial addition of impurities, contained in the nanopowder, obtained by electro explosion of conductor, into the powder, made by synthesis in plasma and not containing these impurities, allowed to reveal their effect on the formation of the microstructure and properties of the sintered by SPS method sample.

Spheroidization of micropowders of a heat-resistant alloy based on nickel aluminide with a particle size of 20 to 45 μm was studied. The alloy was produced by calcium hydride reduction (CHR) and elemental synthesis (SHS). The spheroidization was carried out in a flow of argon–hydrogen thermal plasma generated by a direct-current (DC) plasma torch. The degree of spheroidization of the micropowders reached 98.5%, and the flowability was 20 s/50 g.

Spatial and electronic structures of six-coordinated germanium compounds are calculated within МР2 and AIM methods using PC GAMESS-Firefly, MORPHY, and AIMALL software packages. Main topological characteristics of germanium-substituent bonds are determined in these molecules.

The influence of nanoparticles introduced into a molten weld pool using a flux-cored wire on the structure and impact toughness of the weld metal is considered. The use of a flux-cored wire with tungsten carbide particles is shown to decrease the scatter of the impact toughnesses of the weld metal. The use of titanium carbide allows one to increase the average impact toughness.

The influence of tungsten carbide and titanium nitride nanoparticles on the structure and properties of the weld metal of welded joints made by automatic twin submerged arc welding is considered. The nanoparticles have been introduced into the weld pool as a part of the “master alloy” based on nickel powder (PNE-1 according to GOST 9722). It has been shown that modifying the weld metal with tungsten carbide nanoparticles holds promise for enhancing the impact strength. In addition, it has been found that titanium nitride is prone to dissociation under the same conditions. However, microalloying with titanium, which is due to the release of titanium from the nitride, leads to an increase in the impact strength of the weld metal.

Experimental studies on the synthesis of aluminum oxynitride nanopowders in a reactor with a confined plasma jet by the interaction of disperse aluminum with ammonia and oxygen in a flow of nitrogen plasma generated in an electric arc plasma torch are performed. Preliminary calculations of the equilibrium compositions and thermodynamic characteristics of the multicomponent Al–O–N system are carried out. An optimal design of the reaction prechamber of the reactor is performed. Powders having a cubic structure and consisting of aluminum oxynitride phases with an average particle size in the range from 20 to 200 nm are obtained. It is established that the specific surface area of the obtained powders increases from 20 to 71 m2/g, and the nitrogen content in the nanopowders increases from 3.6 to 14.7 wt % with an increase in the flow rate of quenching gas from 1.8 to 6.0 m3/h. At the same time, the oxygen content decreases from 35.5 to 25.5 wt %. At a minimal flow rate of the quenching gas, the metallic aluminum and its oxide phases are present in the obtained powders. With an increase in the amount of quenching gas, the conditions for the mixing of aluminum vapors with oxygen and atomic nitrogen from decomposing ammonia are improved, which leads to the formation of aluminum oxynitride and aluminum nitride. The variation of the synthesis parameters allows us to obtain aluminum oxynitride nanopowders having a specific surface area ranging from 28 to 50 m2/g containing from 1 to 11 wt % of nitrogen and from 25 to 40 wt % of oxygen.

The effect of processing multicomponent nanopowders of the W-C system obtained by plasma-chemical synthesis in a microwave electromagnetic field with a frequency of 24 GHz, generated by continuous gyrotron, has been experimentally studied. It was found that the formation of nanosized particles of tungsten carbide WC occurs during microwave treatment. The influence of the processing time, microwave power and the composition of the gas atmosphere on the phase composition of nanopowders, their morphology and specific surface area was investigated. It has been found that processing in a microwave field can reduce the time of chemical transformations, leading to the formation of tungsten monocarbide, by an order of magnitude compared to traditional heating in an electric furnace in a hydrogen environment. At the same time, the particle size is preserved in the nanometer range.

Advances in nanotechnology have made it possible to use nanosized particles for the modification of metals and alloys both in metallurgy and in welding. This article discusses the thermodynamic stability of titanium nitride nanosized particles in a molten pool on the basis of theoretical analysis and experiments. It is demonstrated that, upon the addition of titanium nitride to a molten pool, its dissociation should be expected in the overall temperature range; this has been confirmed experimentally.

It is shown that powders of a model high alloy consisting of spherical particles 25–50 μm in size can be synthesized from a starting ultradispersed powder, which is made of a mixture of the alloy components and is fabricated by the magnesiothermal reduction of metal chlorides in the potassium chloride melt. The synthesis includes the stages of microgranulation of an ultradispersed powder, heat treatment of microgranules, classification of the microgranules with the separation of microgranule fraction of 25–50 μm, spheroidization of the separated fraction in a thermal plasma flow, and classification with the separation of a fraction of micro- and submicrometer-sized particles.

This article discusses the possibility of introducing nanosized particles into a molten pool using a flux-cored wire. A flux-cored wire has been proposed with added composite granules obtained upon the combined treatment of nickel powder and nanosized particles. In order to avoid the overheating of particles, it has been proposed to add a flux-cored wire to a molten-pool tail using preheating. The following hardmelting particles have been tested: tungsten carbide (WC), titanium nitride (TiN), and aluminum oxide (Al2O3). It has been demonstrated that the addition of tungsten carbide to a molten pool improves the stability of weld-metal (WM) impact toughness while retaining its average value and the addition of aluminum oxide to a molten pool leads to increased average values of WM impact toughness while retaining its stability. Meanwhile, nanosized particles of titanium nitride in a molten pool are prone to dissociation, which leads to the formation of porosity, thus limiting the field of application of this modifier.

The method of production of group IV powders for additive manufacturing is presented. Powders are produced in the hydrogenation-dehydrogenation process followed by plasma spheroidization of prepared polygonal powders. The dependence of composition of hydrides on amount of absorbed hydrogen is established for the group IV metals; it allows optimizing the technological parameters of processes for hydrogenation and grinding. It is shown that spherical powders of titanium, Ti–6Al–4V, and Zr–10% Ti of mass fractions of 40–70 μm and not less than 40 μm with calculated spheroidization level achieving 96% may be produced in Ar + 8 vol % H2 thermal plasma flow generated by an arc-jet plasma generator. The average roundness factor is 1.01.

The formation of the WO3, SnO2 and ZnO metal oxide nanoparticles from vapors generated during evaporation of the material by a focused beam of microwave electromagnetic radiation with a frequency of 24 GHz and an energy flux density of more than 10 kW/cm2 is studied experimentally. The specific surface area of the nanopowders obtained over the entire range of the process parameters ranged from 1.9 to 8.3 m2/g, which corresponds to an average particle size of 430 to 95 nm. The possibility to control the dispersion composition of the powders is demonstrated. Increasing the quenching air flow increases the specific surface area of the powder obtained. The maximum evaporation rate of WO3 exceeded 100 g/h.

With the help of a complex of methods of disperse-structure analysis of nanopowders of plasmachemical synthesis, the function of particle-size distribution and its main characteristics—the average size and dispersion—are studied. A generalization of results of disperse characteristics for nanoparticles formed with the participation of various mechanisms—“vapor–solid” and “vapor–liquid–solid”—is carried out. It is shown that the formation of titanium nitride and carbonitride nanoparticles proceed on the vapor–solid mechanism without the participation of coagulative-particle growth. For the nanopowders under study, it is established that the variation range of standard deviation for the distribution function is in the interval of 30–60% of the average diameter; the index of aggregation is defined in the range of 1.5–3.0. It is revealed that the logarithmically normal function of particle-size distribution most authentically (with a correlation coefficient of more than 0.95) describes all studied objects for all mechanisms of particle formation in a wide range of dispersion of the received nanopowders independently of process parameters and organization of gas-disperse stream in the plasma reactor. Hypothetically, the established lognormal particle-size distribution is determined by the lognormal distribution of nanoparticles by residence time in the growth zone.

The synthesis of titanium nitride and carbonitride nanopowders from titanium tetrachloride vapor in a stream of hydrogen–nitrogen plasma, generated by an arc torch, in confined-jet flow reactor has been experimentally studied. Single-phase nanopowders with a NaCl-type cubic crystal lattice as assemblies of preferably cube-shaped nanoparticles of a 20–150 nm size and aggregates based on them have been obtained in the experiments. By varying the synthesis parameters, it has been possible to prepare titanium nitride nanopowders with a specific surface area in the range of 11–39 m2/g containing 18.8–22.5 wt % nitrogen, which corresponds to the empirical formula TiN0.79–TiN0.99. The titanium carbonitride nanopowders had a specific surface area of 13–23 m2/g and carbon and nitrogen contents of 7.5–13.6 and 13.5–5.1 wt %, respectively.

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 + zCmHn (synthesis of TiC), and TiCl4 + xH2 + y1N2 + z1CmHn (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.

Parameters have been developed and experimental studies carried out for the synthesis of W-C-Co system nanopowders in a limited jet plasma reactor by interaction of tungsten oxide and cobalt with methane in hydrogen-nitrogen plasma flow generated in an electric arc plasma torch. Nanoscale powders with a specific surface area of about 25 m2/g, consisting mainly of tungsten-carbon phases and cobalt, have been produced.

The characteristics of heat and mass transfer to the wall of a confined-jet plasma flow reactor on the basis of an electric arc plasmatron in the processes of nanopowder preparation from metals and their compounds are studied experimentally. Nanopowders are prepared from copper, tungsten, aluminum oxide, and a composition based on tungsten carbides. The heat flow distribution and the distribution of the mass flow of nanoparticles to the reactor surface at different parameters of the nanopowder preparation processes are studied.

The spatial and electronic structures of three-coordinate aluminum molecules with Al–C bonds are calculated using the GAMESS-Firefly program package at DFT and HF levels of theory. By NBO and AIM methods the main characteristics of Al–C bonds in these molecules are determined. It is shown that by their topological characteristics the Al–C bonds can be characterized as weakened intermediate bonds close to the bonds between closed shell atoms.

Fabrication of WO3 tungsten oxide nanoparticles by evaporation of the initial oxide material with a focused beam of 24-GHz electromagnetic radiation generated in a 5-kW gyrotron complex at a design microwave power density of 10 kW/cm2 has been experimentally studied. Tungsten oxide powders consisting of particles, which sizes are in range of 20 nm up to 1 μm, have been obtained. The particles have different shapes, close to spherical or octahedral, suggesting their formation via both the “vapor-liquid-crystal” and the “vapor-crystal” mechanism. The maximal evaporation rate was 100 g/h. The feasibility of powder dispersity controlling by varying the flow rate of cooling air has been revealed.

The preparation of nanodimensional powders of tungsten carbides, as well as other transitionmetal carbides, using plasma-chemical reduction synthesis are investigated. The main regularities of preparing powders of specified dispersity and composition are revealed. Characteristic particle sizes of carbides are 40–80 nm. In order to prepare a homogeneous mixture of WC-Co nanoparticles with an exact weight content, the procedure of deposition of cobalt on the tungsten carbide powder with the simultaneous introduction of an additive of inhibitor carbides such as carbides of chromium, vanadium, and tantalum is developed. The prepared powders were investigated using modern methods, including high-resolution scanning electron microscopy and fractional gas analysis.

The synthesis of TiN nanopowder from titanium hydride in thermal plasma generated in DC arc plasmatron is investigated experimentally. It is shown that a single-phase TiN nanopowder can be produced within a two-stage process consisting of plasma synthesis and separation of powdered product by means of sedimentation. The yield of nanopowder is up to 90%.

The structure of a welded joint obtained by argon-arc welding with the use of a composite electrode wire of a Ni3Al-base alloy after directed crystallization is studied. It is shown that the use of composite electrode wire containing nanoparticles of tungsten carbide for argon-arc welding promotes formation of a quality weld metal and a defect-free transition zone between the latter and the directedly crystallized alloy based on Ni3Al.

The spatial and electronic structures of trimethoxyaluminum complexes with neutral molecules are calculated by the MP2/6-31(2d,p) method using the PC GAMESS-Firefly program package. The main characteristics of aluminum bonds in these molecules are determined by AIM and NBO methods. It is shown that these bonds can be characterized as the bonds between the atoms with closed shells.

Experimental studies on the synthesis of aluminum oxynitride nanopowders in a reactor with a confined plasma jet by the interaction of disperse aluminum with ammonia and oxygen in a flow of nitrogen plasma generated in an electric arc plasma torch are performed. Preliminary calculations of the equilibrium compositions and thermodynamic characteristics of the multicomponent Al–O–N system are carried out.

DFT and HF methods using the PC GAMESS-Firefly program are employed to calculate the spatial and electronic structures of molecules: alkoxy derivatives of aluminum. By NBO and AIM methods the main characteristics of Al-O, C-O, and Al-X bonds in these molecules are determined. It is shown that Al and O atoms interact with each other as atoms with closed shells. The C-O bonds are close to covalent, whereas the Al-X bonds are the intermediate type bonds.

Air–methane and nitrogen–hydrogen DC thermal plasma confined flows were used to synthesize tungsten carbide and vanadium carbide nanopowders. The influence of input process parameters such as C/W and C/V molar ratio, plasma jet chemical composition, plasma jet enthalpy, and reactants flow rates on the average nanoparticle size, chemical and crystallographic phase compositions were investigated. During post heat treatment, the synthesized MeC1−x nanopowders were fully carburized to monocarbides WC and VC with particles size less than 80 and 40 nm correspondently.

The formation of layers of copper and tungsten nanoparticles on the surface streamlined by a flow of products of plasma synthesis in a confined-jet flow reactor has been investigated. The distribution of heat and mass fluxes onto the surface of the plasma reactor has been studied for various values of the enthalpy, thermal-plasma flow velocity, and reactant concentrations.

The spatial and electronic structures of a series of substituted germylene molecules are calculated by DFT and HF methods using the PC GAMESS-Firefly program package. Molecular structures are optimized at the DFT (B3LYP/6-31G(2d,p)) level; wave functions and topological characteristics of the electron density distribution are calculated in the HF/acc-pvtz approximation. By means of NBO and AIM methods, the main characteristics of Ge-X bonds in these molecules are determined. The Ge-X bonds are shown to be the intermediate type bonds. The energies of these bonds are estimated.

The ECG is used to monitor cardiovascular diseases. ECG parameters obtained by averaging over statistically significant arrays of data are assumed to be normal. Individual normal ECG parameters may differ from statistical level, but such difference is not a symptom of pathology. Comparative ECG analysis is the subject of this work.

The PRIRODA (riDFT method, BLYP functional, hf.bas basis set) and Gaussian 98 (HF method, 6-311G(d,p) basis set) programs are used to calculate the spatial and electronic structures of a number of molecules of substituted germocanes with a general formula of R,Rs’Ge(XCH2CH2)2Y (where X = C, O, S, and Y = N, O, S). With the use of the AIM method the topological characteristics of Ge—Y donation bonds are calculated in these molecules. An analysis of the obtained data shows that up to the values of Ge—Y interatomic distances of ~2.7 A these bonds can be considered as the intermediate type bonds. At Ge—Y distances of ~3.0 A these bonds become ionic, therefore the Coulomb interaction between oppositely charged Ge and Y atoms mainly contributes to Ge—Y bonding.

The results of an investigation into the microstructure of composite materials based on an aluminum matrix reinforced by intermetallic phases, which are formed by in situ reactions in the presence of nanosize ceramic particles, are presented. The possibility of modifying and stabilizing the structure of such composite materials with nanopoweder additives is determined.

The spatial and electronic structures of molecules with three substituents at the germanium atom (tricoordinated germanium) were calculated by the DFT method (Gaussian-98 program package, B3LYP functional, 6-311G(d,p) basis set). The main characteristics of Ge-X bonds in these molecules were determined by NBO and AIM procedures. It is shown that Ge-X are weak, “intermediate” type bonds. The bond energies were calculated.

The molecular and crystal structure of three organogermanes Cl 3 GeCH 2 OC(O)R (where R = –NHC 6 H 11 , –C 10 H 15 , and –NH 2 ) has been determined by X-ray diffraction method in order to investigate geometrical regularities of these molecules. The nature of Ge–O bonding in these molecules was investigated by quantum chemistry method. It was shown that the influence of the nature of ligand, attached to carbon atom of the carbonyl group, on Ge⋯O interatomic distance is incidentally small in isolated molecule while in the crystal it is much more pronounced due to the crystal packing effect. The nature of Ge⋯O bonding corresponds to intermediate type of interatomic interaction in terms of “Atoms in molecules” theory.

The generation of atoms and radicals by the equilibrium thermal dissociation of oxygen and the same process involving water vapor are similar in terms of the reactive-species yield and energy consumption. The energy input into the generation of atoms and radicals is the smallest at 4500 K; about 70% of the energy is spent directly for the breaking of chemical bonds. From the calculations of the kinetics of oxygen atom recombination, it follows that cooling at a rate higher than 107 K/s makes it possible to achieve considerable deviations from the equilibrium atom concentration. The lifetime of atoms in cooling thermal plasma is estimated at 10−5 s. It has been established experimentally that a thermal plasma jet plunging into the water bulk generates hydrogen peroxide. The totality of factors affecting the hydrogen peroxide accumulation rate can be represented in as a generalized parameter, specifically, the atomic oxygen feed rate.

Theoretical analysis is given to one of the promising processes for the preparation of nanosized metal powders, namely, plasma chemical synthesis by the action of thermal plasma on a material distributed in the plasma. Special attention is given to the methodology of investigation of such plasma jet processes, which may ensure the prediction of results of experimental studies; qualified data processing; and, ultimately, preparation of powders with a prescribed composition and required nanoscale dimensions by means of controlled plasma-chemical synthesis.

The reaction of adamantane-1-carboxylic acid chloride with trichlorogermylmethanol afforded (trichlorogermyl)methyl adamantane-1-carboxylate, whose molecular structure was established by 1H NMR spectroscopy and X-ray diffraction analysis.

The spatial and electronic structures of substituted germatranes were calculated by the DFT method (GAUSSIAN-98, B3LYP functional, 6-311G(d, p) basis set). The topological characteristics of Ge-N dative bonds in these molecules were calculated using the AIM method. Analysis of the data demonstrated that Ge and N atoms interact with each other as “closed-shell” atoms and that Coulomb interaction of germanium and nitrogen atoms with opposite charges makes the major contribution to Ge-N bonding. However, it is also possible to suggest that the interpenetration mechanism for van der Waals spheres of Ge and N atoms takes place, as in the case of hydrogen bond formation.