Alexey Gnedovets

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Alexey verified their affiliation via an institutional email.

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• PhD
• Senior Researcher at Baikov Institute of Metallurgy and Materials Science

The features of interaction of a spherical metallic particle with a rarefied thermal plasma flow due to the presence o charges-electrons and ions in the gaseous phase-are considered. Analytical expressions describing charge, momentum, and energy exchange between the plasma and the particle fr the cases of strong and weak Debye screening are obtaine...

A novel technology of plasma spraying three‐dimensional capillary porous (3DCP) titanium coatings with principally new structures consisting of ridges and cavities has been developed. The surface area of the 3DCP coatings increases in direct proportion to the increase of the thickness of the deposited coating. The process of fabrication of the 3DCP...

Permeable (~70% porosity) nickel with a pronounced hierarchical structure was synthesized by powder metallurgy methods in sintering–evaporation process from a nickel nanopowder and an ammonium bicarbonate micropowder as a space holder. The obtained porous nickel contained pores of three spatial scales: macropores (30–50 μm in size), their connectin...

Pulsed laser ablation of MoS2 and WO3 targets at appropriate pressures of background gas (Ar, air) were used for the preparation of new hybrid nanostructured catalytic films for hydrogen production in an acid solution. The films consisted of a nanostructured WO3−y underlayer that was covered with composite MoS3/np-Mo nanocatalyst. The use of dry ai...

Permeable nickel metallic and nickel oxide ceramic materials with nanostructured surface and multilevel hierarchical porosity were created by cyclic redox post-treatment of biporous nickel(II) consolidated in the sintering–dissolution process. Additional levels of intraparticle porosity — Kirkendall pores and shrinkage nanopores — were formed durin...

The results of research by the team of authors of the article in the field of obtaining metal nanopowders using the chemical-metallurgical method are presented. Justifications are given for the conditions and duration of passivation of powders to prevent their spontaneous combustion during storage. The prospects for using nanopowders to create high...

By performing high-temperature cyclic oxidation-reduction (redox) post-treatment of biporous nickel fabricated in the sintering-dissolution process using micron nickel powder and sodium chloride as a space holder, permeable materials with multilevel hierarchical porosity were created. After an oxidation stage in an air atmosphere, a porous material...

Permeable metallic nickel and ceramic nickel-oxide materials with nanostructured surface and multilevel hierarchical porosity were created by cyclic redox post-treatment of biporous nickel (II) consolidated in the sintering-dissolution process. Additional levels of intraparticle porosity – Kirkendall pores and shrinkage nanopores – were formed duri...

By performing high-temperature cyclic oxidation-reduction (redox) post-treatment of biporous nickel fabricated in the sintering-dissolution process using micron nickel powder and sodium chloride as a space holder, permeable materials with multilevel hierarchical porosity were created. After an oxidation stage in an air atmosphere, a porous material...

In this work, we obtained porous materials based on Cu – Zn alloy with high permeability and developed surface. This was achieved by creating multilevel porosity in the material by a combined method that combines the use of a removable pore former and chemical etching. The effect of synthesis conditions on the structure and properties of the obtain...

Highly porous permeable nickel materials with a hierarchical structure were consolidated by powder metallurgy methods in sintering-dissolution and sintering-evaporation processes from nickel nanopowder and micropowders of two different types of space holders – water-soluble sodium chloride NaCl and thermally unstable ammonium bicarbonate NH4HCO3, r...

Nanopowder nickel materials with trimodal porosity were consolidated in the sintering-dissolution process using bidispersed NaCl porogen powders. The dependence of the permeability of the fabricated porous nickel materials on the ratio of coarse and fine components of bidisperse porogen was investigated. The studies were carried out on samples made...

A cylindrical titanium implant simulator with flanges and plastic, which is a composite material, was modelled in shear tests to imitate the behaviour of the connection between an implant and bone tissue. The shear strength of a composite material was estimated by the rule of mixtures, taking into account the strength of the titanium-plastic bounda...

The process of producing permeable highly porous nickel-based powder materials is described. The porous structure of the materials is formed due to the partial sintering of pressed metal powder, as well as due to the addition of a temporary pore filler. The system of interconnected macropores, formed due to large particles of porogen, ensures the p...

The paper reports on the synthesis of nanostructured low-temperature transition alumina island coatings on the surface of macropores of permeable monolithic hierarchically porous nickel. It is established that hexagonal alumina nanoplates are the primary structural elements of the coating.

Nanostructured island coatings composed of the low-temperature alumina modification were synthesized on the surface of macropores of hierarchically porous permeable monolithic nickel. The primary structural elements of the coating were determined to be hexagonal alumina nanoplates.

This paper reports on the creation of a highly porous material with a hierarchical structure using powder metallurgy methods based on nickel nanopowder and ammonium bicarbonate NH4HCO3 as a space holder.

The possibility of obtaining permeable highly porous materials based on nanopowders of nickel using ammonium bicarbonate as a space holder is shown. In the fabrication of porous samples, a sintering-evaporation process (SEP) was carried out, in which a thermally unstable pore former was decomposed and distilled from the compacts during preheating b...

The possibility of obtaining permeable highly porous materials based on nanopowders of nickel using ammonium bicarbonate as a space holder is shown. In the fabrication of porous samples, a sintering-evaporation process (SEP) was carried out, in which a thermally unstable pore former was decomposed and distilled from the compacts during preheating b...

The films of tungsten oxides were prepared by pulsed laser ablation of W target in a reactive gas atmosphere (air of laboratory humidity). Optical analysis and ion signal measurements for the laser plume allowed to recognise a threshold gas pressure that suppresses the deposition of non-scattered atomic flux from the plume. When the pressure exceed...

The morphology of micrometer-sized silver particles obtained by liquid-phase chemical reduction of silver nitrate with ascorbic acid depends appreciably on the solution pH. The synthesis carried out at 100°C for 20 min at pH < 4 or pH > 9 yields anisotropic faceted nanocrystalline particles, while the synthesis at pH = 5–8 results in self-assembly...

Irradiation of MoSe2 target with intensive laser pulses caused the formation of micro- and nanoparticles. The particles were observed on the target surface and in MoSex films prepared by deposition of the laser-induced plume. Content of nanoparticles on the film surface was markedly larger than that of microparticles. Transport of the plume in vacu...

The online version of the original article can be found at http://dx.doi.org/10.1134/S2075113316040389 An erratum to this article can be found at http://dx.doi.org/10.1134/S2075113316040389.

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...

Synthesis of the single-phase γ′-Fe4N on the surface of the micron-sized particles of iron at low-temperature gaseous nitriding of carbonyl iron powder in a stream of ammonia is studied. It is shown that synthesis of particles with such structure is possible with simultaneous control of the number of process parameters: temperature, degree of disso...

Four types of the three-dimensional plasma capillary-porous titanium coatings for model intraosseous implants were developed. By means of pulsed microplasma oxidation in solutions or plasma spraying of powders, the additional bioactive coatings on the base of calcium phosphates have been deposited on the Ti coating surface. Shear strength values of...

The results of studies on the synthesis of single-phase gamma'-Fe4N shells on micron-sized particles of iron at low temperature gaseous nitriding of carbonyl iron powder in a stream of ammonia are presented. The synthesis of particles with such a structure is possible while controlling the number of process parameters: temperature, degree of dissoc...

Shadow-masked pulsed laser deposition (SMPLD) enables the preparation of films that contain none of the droplets that are normally formed in laser irradiation of the target. The platinum (Pt) film produced by SMPLD was studied using scanning electron microscopy (SEM), atomic force microscopy (AFM), and Rutherford backscattering spectroscopy (RBS) o...

The practical possibility of synthesizing micron-size corrosion-resistant powder materials based on lower and higher nitrides of the Fe-N system in the form of both a bulk composition and a “core-shell” system was implemented at relatively low temperatures. Information on the elemental and chemical composition of iron nitrides was obtained using th...

Solid lubricant films were obtained by pulsed laser deposition (PLD) on steel substrates in such a way as to form an underlayer of diamond-like carbon film, and then the concentration of carbon was gradually reduced in Mo–Se–Ni–C films to obtain a pure MoSex(Ni) top layer. The use of a shadow mask configuration (SMPLD) avoids the deposition of micr...

Results of in situ studies into the coagulation of gold nanoparticles in amorphous carbon and silicon dioxide films exposed to an electron beam are presented. Special attention is paid to the final stage of coagulation (nanoparticle merging). The results clearly demonstrate the possibility of modifying the structure in a local film region by exposi...

Pulsed laser deposition of WSex films was carried out in a buffer gas (Ar). The mask was placed between a WSe2 target and a substrate in order to prevent the deposition of micro- and nanoparticles. At Ar pressure of 2 Pa the laser plume was effectively scattered by the gas into a shadow area, and the ion bombardment of the film was the most intense...

A pulsed plasma plume obtained by pulsed laser irradiation of a Pt target was used to fabricate a hydrogen sensor on a 6H-SiC single crystal by means of ion implantation followed by thin film deposition. To realize the ion implantation, high voltage pulses with positive polarity were applied to the Pt target when the laser plasma expanded from the...

The effect of the conditions of pulse laser deposition of MoSex thin-film coatings on the structural and phase state of surface layer on an iron substrate and on the distribution of elements over the thickness of the coatingsubstrate interface is investigated. Model multilayer test pieces bearing a thin film of 57Fe are studied. The speed distribut...

A multilayer WSe1.7/57Fe/54Fe structure was created by sequential pulsed laser deposition on a Si substrate of 54Fe-rich, 57Fe-rich, and WSe1.7 thin films subjected to laser plasma ion implantation (LPII). Electric pulses of negative polarity with amplitude 45 kV were applied to the 54Fe laser target. The turn-on time of the pulse, with a duration...

Thin-film structures based on gas-sensitive tungsten oxide Ag/WOx /W exhibiting a bipolar resistive switching effect were prepared. The current-voltage characteristics of the structures were studied in air with laboratory humidity and after hydrogen feeding into the chamber to a concentration of 2% in the air. The chemical state of the surface laye...

We have studied factors influencing the formation of particles with the structure of a spherical metal W core inside a WSe2 shell during pulsed laser deposition (PLD) of thin films of tungsten diselenide under variable conditions (buffer gas (Ar) pressure, substrate temperature). It is established that the metal core is formed at the stage of laser...

The origination and evolution processes of gold clusters in a three-layer carbon-(gold + carbon)-carbon system have been observed in situ in the column of a transmission electron microscope. It has been shown that the sizes of the gold nanoclusters depend on the duration of the impact of a fast electron beam. Under long-term exposure (about 2 h) wi...

Thin film Mo–Se–Ni–C coatings for tribologycal applications were prepared by pulsed laser co-deposition from two targets — MoSe2(Ni) and graphite. Two methods of deposition from the MoSe2(Ni) target were used: deposition with unhindered expansion of the laser plume (standard PLD) and deposition of a plume scattered in collisions with Ar gas (pressu...

Experimental data and results of mathematical modeling have been used to determine the energy characteristics of an ion beam used to assist pulsed laser deposition (PLD) of MoSe2 layers under conditions of positive high-voltage pulses applied to a laser-ablated target. It is shown that PLD assisted by implantation of ions at energies up to 100 keV...

WSex thin films were obtained by pulsed laser deposition in vacuum and at various Ar gas pressures up to 10 Pa. Stoichiometry and chemical state of the WSex films were studied by means of Rutherford backscattering spectrometry and X-ray photoelectron spectroscopy. In the case of pulsed laser deposition of WSex films in vacuum the value of stoichiom...

The features of the structural formation and chemical composition of thin films of tungsten oxide grown under various conditions of pulsed laser deposition on a substrate of single crystal silicon carbide followed by annealing have been investigated. To obtain doped films of tungsten oxide deposited by the laser plume expanding from a tungsten targ...

The effect of regimes of reactive pulsed laser deposition (PLD) of WOx thin films on gas sensing performance of a metal-oxide-silicon carbide device potentially applicable for monitoring explosive gases, in particular, hydrogen, and environmentally harmful gases at elevated temperatures was investigated. The films were deposited from a tungsten tar...

Nanopowders of iron nitrides γ'-Fe4N, ε-Fe2-3N and ζ-Fe2N were obtained by low-temperature gas-phase nitriding process in the flow of NH3 at atmospheric pressure. Complete nitriding of the Fe-nanopowder was reached after ~90 min.

The crack resistance of fuel pellets in fuel elements is examined. When fuel elements are in operation, fuel pellets fracture as a result of the appearance of tangential tensile stresses of thermal origin. These stresses can be decreased by creating a gradient microstructure in a uranium dioxide pellet so as to decrease the radial variation of the...

A fairly simple method of surface doping of a SiC substrate with a catalytic metal (in particular, platinum) from a pulsed laser plasma is suggested. Doping is attained due to implantation of high-energy ions and ion mixing of the plasma-deposited film with the surface layer of the SiC substrate. The developed mathematical model makes it possible t...

The formation of the chemical composition of dichalcogenide films at pulsed laser deposition in vacuum and in rarefied gases (Ar, H2) is investigated with MoSex thin-film coatings. It is found that deposition in gases increases the selenium concentration and somewhat flattens the composition over the substrate surface. To elucidate the mechanisms u...

Peculiarities of WOx films fabrication by reactive pulsed laser deposition for high temperature Pt-oxide-SiC devices formation were investigated. Deposition of the oxide film was also carried out in such a way as to prevent deposition of droplet fraction (deposition with anti-droplet screen). Direct Simulation Monte Carlo and Kinetic Monte Carlo me...

A relatively simple technique of high-energy ion implantation of the pulsed laser plasma under the influence of an external pulsed electric field is suggested. The developed mathematical model allows forecasting depth distribution of implanted atoms on the basis of experimental measurements of fundamental physical characteristics of the pulsed lase...

Physical, chemical and tribological properties of the MoSex and MoSexCy coatings for micromechanical applications grown by pulsed laser deposition in vacuum and in a rarefied inert gas (argon) atmosphere are studied. In a number of experiments a disk-shaped screen was used that is placed on the path of the expansion of laser plume in order to trap...

The features of platinum film formation on n-6H-SiC substrates were experimentally studied for different methods of pulsed laser deposition, i.e., by both the conventional method in vacuum and in an inert gas atmosphere. In the latter case, a disk screen was placed on the plume expansion axis between the laser target and substrate to protect the la...

The formation of thin-film coatings of molybdenum diselenide is studied during the deposition of a laser-induced material flux using a shield that is placed on the path of the expansion of this flux in order to trap the droplet fraction. To increase the efficiency of atomic scattering into the shadow zone (behind the shield), deposition is carried...

The formation of thin-film coatings of molybdenum diselenide is studied during the deposition of a laser-induced material flux using a shield that is placed on the path of the expansion of this flux in order to trap the droplet fraction. To increase the efficiency of atomic scattering into the shadow zone (behind the shield), deposition is carried...

The chemical composition and tribological properties of the thin-film diselenide molybdenum coatings grown by pulsed laser deposition in vacuum and a rarefied inert gas (argon) atmosphere are studied. Upon deposition in a gas at a pressure of ~2 Pa, stoichiometric coatings with improved antifriction properties as compared to vacuum-deposited coatin...

The chemical composition and tribological properties of the thin-film diselenide molybdenum coatings deposited by pulsed laser deposition in vacuum and a rarefied inert gas (argon) atmosphere are studied. Upon deposition in a gas at a pressure of ∼2 Pa, stoichiometric coatings with improved antifriction properties as compared vacuum-deposited coati...

Ion-implantation surface treatment by means of highly ionized plasma is considered. The plasma is formed close to the machined part by the action of intense laser pulses on a target made of the implantation material. A mathematical model is developed to describe the plasma dynamics and the formation of a high energy ion flux at the machined surface...

The paper discusses effects of novel nanostructured composite coatings on mechanical properties of bone-implant systems. The composite coatings comprise thick Ti underlayer featured by 3-dimentional capillary-porous morphology and thin top ceramic layer with enhanced biological activity. The Ti layer is produced by plasma spraying under low inciden...

A new technology was developed for deposition of composite coatings, in which a hydroxyapatite (HA) layer is arc-plasma sprayed on the top of thick 3D capillary porous (3DCP) Ti underlayer in the atmosphere of air. The parameters of plasma spray process were optimised using Monte-Carlo simulation of the coating formation on each stage. The composit...

A mathematical model describing the dynamics of a pulsed laser plasma with multiply charged ions, as well as the formation of the accelerated ion flow in an external magnetic field, is developed. Experimental studies and mathematical simulation by the particle-in-cell method are used to determine the role of multiply charged ions in the process of...

The opportunity of application of the kinetic Monte-Carlo method for modeling of thin-film coatings growth at pulsed laser deposition is shown. Cases of low-temperature deposition of a stream of atoms (excluding transport processes on a surface and in a volume of a growing coating) and differing by incidence conditions on its surface are considered...

The opportunity of application of the kinetic Monte-Carlo method for modeling of thin-film coatings growth at pulsed laser deposition is shown. Cases of low-temperature deposition of a stream of atoms (excluding transport processes on a surface and in a volume of a growing coating) and differing by incidence conditions on its surface are considered...

Results are presented from experimental and theoretical studies of current, dose and energy characteristics of ion beams in the process of ion implantation from pulsed laser plasma containing multicharged ions in an external accelerating electric field. Physical processes in expanding laser-produced plasma are simulated by the particle-in-cell meth...

Composite coatings are subsequently formed using two plasma-assisted methods, i.e. plasma spraying of metallic Ti followed by plasma electrolytic anodic treatment. Effects of major parameters of the duplex coating process on the surface layer structure, phase comosition and biological properties are discussed.

3D discrete ballistic model of plasma sprayed coatings structure formation is presented. Effect of the spraying angle on a porous structure of the coatings has been investigated by numerical computations. Results of computer simulation as well as experimental data show that at a sputtering angle less than 45°, change of the mechanism of a surface r...

Results are presented from computer modeling of the expansion of pulsed laser plasma containing single and double charged ions between two parallel electrodes – laser target and work piece. To ensure high-energy ion implantation, a negative high-voltage pulse with a given shape was applied to a work piece. The possibility is shown of application of...

Results are presented from computer modeling of the expansion of pulsed laser plasma containing single and double charged ions between two parallel electrodes – laser target and work piece. To ensure high-energy ion implantation, a negative high-voltage pulse with a given shape was applied to a work piece. The possibility is shown of application of...

Experiments on pulsed laser deposition of Fe films on Si substrates were performed with the aim to analyze an energy spectrum and a dose of ions bombarding the film in strong pulsed electric fields. The goal of the study was to clarify the physical nature of the processes determining characteristics of the ion beam produced from the expanding plasm...

Novel technology of plasma spraying of three-dimensional capillary-porous coatings with principally new structure consisting of ridges and cavities has been developed. The process of fabrication of these coatings is performed under a sharp incidence angle of the plasma spray to the substrate. The method of spraying is based on the effect of shadow...

Composite coating for intrabone implants as a combination of capillary-porous titanium coating with deposited bioactive ceramic top layer is proposed. Porous coating is formed on an implant surface by atmospheric plasma spraying and bioactive ceramic layer is deposited over it by microplasma process in electrolytic solutions. High values of porosit...

A crucially new composite coatings consisting of plasma sprayed 3D capillary-porous (TCP) titanium coatings and bioactive ceramic (BC) ones deposited by microarc oxidation have been developed. These composite coatings are designed for use on the surface of intrabone coxofemoral implants. Combination of TCP having an open hollow macroporosity with B...

Results are presented from experimental studies of pulsed plasma flows generated by nanosecond laser pulses with an intensity of 7 × 108 W/cm2 from a solid-state target in a strong electric field. The current pulses through the laser target and the depth distributions of the iron ions implanted in a silicon substrate to which a negative high-voltag...

Novel technology of plasma spraying of three-dimensional capillary-porous (3D-CP) coatings with principally new structure consisting of ridges and cavities has been developed. The surface area of 3D-CP coatings increases directly proportionally with the increase of the thickness of the deposited coating, that is why such coatings are called three-d...

12 A 2D gas-dynamic model of laser ablation an ambient gas atmosphere is proposed. To obtain the boundary conditions at the evaporated target surface, a nonlinear heat transfer problem in the target including the dynamics of the melt and evaporation fronts is considered. Back condensation of the vapor at the target is taken into account. At later s...

A two-stage two-dimensional (2D) gas-dynamic model of laser ablation in an ambient gas atmosphere is proposed. The initial one-dimensional stage of the process is related to the ablation plume formation under the action of a laser pulse (duration of the order of 10 ns; fluence about several J/cm2; laser spot diameter about 1 mm) and describes heati...

A two-step gas-dynamic model of laser ablation in an ambient gas atmosphere is proposed. The initial 1D stage is related to ablation plume formation and describes heating, melting and evaporation of the target, the target-vapour interaction in the boundary layer, and vapour dynamics. The final 2D stage is responsible for the formation of energy and...

Synthesis of nanoscale particles as a result of vapor condensation under laser vaporisation of materials into high-pressure surrounding atmosphere has been studied. A 2D-hydrodynamic model is developed for a simulation of nanoscale particles formation in a laser-produced erosive flow propagating from the irradiated surface into the ambient gas. The...

A model for submicron particles formation by laser evaporation in ambient gas atmosphere is proposed. Heat transport in the target, evaporation, vapour diffusion in the ambient gas, and kinetics of nucleation and particles growth are considered. The diffusion regime of evaporation is studied. Submicron particles formation by millisecond laser pulse...

A model is developed for computer simulation of nanoscale particles formation by exposing the solid targets with the millisecond laser pulses of about 104-105 W·cm-2 energy flux density. The 'soft' regime of vapour diffusion from a laser-heated surface of a target into an ambient atmosphere is studied. The laser flux is presumed to be low, so that...

A one-dimensional model of nanoscale particle formation by the exposure of solid targets to millisecond laser pulses of about 104-105 W cm-2 energy density flux is proposed. A `soft' regime of vapour diffusion from a laser-heated surface into an ambient atmosphere is studied. Laser flux is presumed to be relatively low, so that the surface temperat...

A two-stage two-dimensional gas-dynamic model of pulsed laser deposition in an ambient gas atmosphere is proposed. Initial one-dimensional stage is responsible for evaporation plume formation and describes heating, melting and evaporation of the target, the target-vapour interaction in the boundary layer, and vapour dynamics. Final two-dimensional...

Kinetic theory approach is used for the description of plasma-particle charge and momentum transfer under rarefied plasma flow conditions. The analysis is based on the choice of the velocity distribution functions of plasma species (molecules, ions and electrons) with deviations from equilibrium caused by the flow velocity, heat flux and electric c...

Synthesis of ultrafine particles as a result of condensation in an erosive jet at laser vaporization of materials (metals, metal oxides, carbon) in gases (hydrogen, oxygen, helium, argon, xenon and air) at high pressures is investigated. The granulometric, phase, and chemical composition of the condensate particles is analyzed in relation to the el...

Synthesis of ultrafine particles as a result of condensation in erosive plasma jet formed at laser vaporization of materials at high pressures has been investigated. 2D-hydrodynamical model is developed for a simulation of nanoscale particles production by means of laser-evaporation technique. The approach is based on a combined solution of the set...