Plasma-chemical Synthesis Research Articles

Formation of ultra- and nanodispersed "core-shell" structures Ti0.8Mo0.2C0.5N0.5-Ni-Mo in the process of plasma-chemical synthesis of a mechanical mixture of titanium carbonitride with metallic nickel and molybdenum

Formation of ultra- and nanodispersed "core-shell" structures Ti0.8Mo0.2C0.5N0.5-Ni-Mo in the process of plasma-chemical synthesis of a mechanical mixture of titanium carbonitride with metallic nickel and molybdenum

SYNTHESIS OF MATERIALS BASED ON COMPOUNDS OF RARE EARTH ELEMENTS WITH TITANIUM, HAFNIUM AND ZIRCONIUM AS PROMISING NEUTRON ABSORBERS FOR NUCLEAR REACTORS

A review of the methods for the synthesis of titanates, hafnates, and zirconates of rare earth elements, primarily dysprosium, which have been applied as neutron-absorbing materials for nuclear reactors or are promising due to their high radiation resistance, phase stability, compatibility with structural materials, and corrosion resistance is presented. The characteristics of titanates, hafnates, and zirconates of dysprosium obtained by these methods are presented: high-temperature solid-phase synthesis in compacted mixtures of initial oxides; induction melting of oxides in a “cold” container; chemical methods based on co-precipitation and heat treatment of aqueous solutions; mechanochemical activation of oxide powders in planetary mills followed by heat treatment; plasma-chemical syn-thesis.

Plasma-chemical synthesis of highly dispersed core–shell structures from a mechanical mixture of titanium carbide and titanium nickelide

Plasma-chemical synthesis of highly dispersed core–shell structures from a mechanical mixture of titanium carbide and titanium nickelide

Plasma-chemical synthesis of carbide-based vacuum-plasma functional coatings and study of tribological characteristics of friction pairs

The work is devoted to the search for new materials with high functional characteristics using the Avinit vacuum-plasma technologies developed by us, based on the complex use of coating methods (plasma-chemical CVD, vacuum-plasma PVD (vacuum-arc, magnetron), processes of ion saturation and ion surface treatment), stimulated by non-equilibrium low-temperature plasma.Processes of controlled plasma-chemical synthesis of the formation of multicomponent coatings in "metal-carbon" systems – Avinit coating (TiC, MoC) using vacuum-arc sources of ionized atomic fluxes of titanium and molybdenum in an argon-benzene plasma environment were developed and their characteristics were studied depending on their conditions formation.Metallographic studies confirm the possibility of low-temperature application of high-quality wear-resistant high-hard "metal-carbon" coatings with a hardness of 18,000-30,000 MPa, while ensuring good adhesion to the substrate materials (steel DIN 1.2379) without reducing strength and without deteriorating the cleanliness class of the original surface.The conducted tribological tests using the "cube-roller" scheme reveal high tribological characteristics of steel DIN 1.2379 tribopairs with developed coatings and testify to the promisingness of the developed multi-component multilayer coatings Avinit (Ti-C, MoS) for increasing wear resistance and reducing the coefficient of sliding friction in friction nodes.The developed plasma-chemical vacuum-plasma coatings are applied to mock-up samples of the working compressor blades of the GTE of aircraft engines. Proven modes allow to get high-quality, uniform coatings with high adhesion.This gives reason to consider the developed process as an alternative for expanding the range of new Avinit vacuum-plasma erosion-resistant coatings and developing structures of anti-friction wear-resistant coatings to increase the performance of friction pairs in "coating-steel" and "coating-coating" systems.

In English

The article discusses methods for obtaining carbon nanostructures (CNS), as well as their use to create three-dimensional (3D) products using FDM, CJP, SLA, SLS technologies. The process of manufacturing consumables for 3D printing technologies (FDM, CJP, SLA, SLS) for creating new composite 3D products based on carbon nanostructures is described. The paper contains a detailed description of which methods of CNS synthesis are more productive and how they allow you to guarantee the production of one or another type of CNS. The paper analyzes the existing 3D printing technologies using CNS, developed a scheme for the full cycle of creating a 3D product containing CNS, taking into account various methods for the synthesis of CNS with the transformation of graphite or other carbon-containing material. It also describes the process of creating composite coils for FDM 3D printing from nanocomposite filaments (rigid polymer-CNS) based on a rigid polymer, which have undergone the process of preparation in a special mixer. The process of preparing consumables and printing a 3D volumetric product using FDM, CJP, SLA, SLS technologies using CNS is described. An overview of consumables for 3D products of FDM technology is presented. The analysis of composite 3D products (ceramic-CNS, rigid polymer-CNS) obtained by FDM and CJP technology was carried out. The paper also describes the three most productive methods for the synthesis of CNS: plasma-chemical synthesis in gas or liquid and pyrolytic method. These synthesis methods make it possible to guarantee the production of a certain type of CNS and have a high quality of the obtained nanoproducts. Various types of CNS are described, including soluble (fullerenes and fullerene-like structures) and insoluble nanostructures (graphenes, carbon nanotubes, carbon nanofibers, nanocomposites, etc.).

The effect of modification with nanocompositions on the structure and properties of foundry silumins


 Abstract. Problem. The difficulty of solving the problem lies not only in the improved quality of casting alloys, but also in the development of recommendations for achieving stability of the chemical composition, refining the structure, and increasing the mechanical and technological properties of castings. Goal. The goal of the work is to achieve a stable dispersed structure and increase the complex of mechanical properties of foundry silumins. Methodology. Based on the Al – Si influence diagram, the choice of cast aluminum alloys for modification with nanocompositions is substantiated. The technology of modification with nanodisperse compositions consisted in introducing powders of the complex nanomodifier Mg2Si+SiС into the aluminum melt. A mixture of Mg2Si+SiC nanopowders with a particle size of 50...100 nm, obtained by plasma chemical synthesis, was mixed for several hours in a special attritor with successive pressing of modifier tablets on an automatic press. Results. The technological process of modifying aluminum melts with a complex modifier was developed, the temperature and time parameters of the process were determined. Brinell hardness was measured on samples of AL4 and AL4C alloys, 25x25 mm in size. As a result of the obtained data, it is observed that in the modified samples of the AL4 alloy, the hardness increased by 6.9%, and in the AL4C samples – by 4.8%. The obtained hardness measurement data are consistent with the results of testing the strength properties of alloys before and after modification. Originality. In the modified alloys, a higher fluidity than in the initial state and a homogeneous dispersed microstructure were obtained. Practical value. In the modified alloys, an increase in strength properties was achieved: σv by 9 - 10%; σ0.2 by 11-12%, while maintaining the level of plasticity. The impact strength of modified alloys is significantly increased by 20-30%. As a result of the conducted studies of the structure and properties of cast alloys AL4 and AL4C, the effect of modification with nanodisperse compositions was confirmed.

Study of structure formation and strength indicators of aluminum alloys when modified with dispersed compositions

Promising directions of modification of aluminum alloys are studied in the field of application of powder modifiers. The use of such modifiers facilitates the technological process, is environmentally safe, leads to a uniform distribution of the introduced compositions over the cross-section of the casting, which increases the strength, plastic properties of the alloys and their stability. Purpose. The purpose of the work is to increase the mechanical properties and corrosion resistance of aluminum alloys when modified with dispersed compositions. Methodology and materials. To achieve the goal, the tasks were set: to conduct a study of a complex of mechanical properties, necessary technological characteristics, corrosion resistance and structure of alloys before and after modification. Aluminum alloys of the Al-Si, Al–Mg–Sc systems, promising for nuclear power plants, have been proposed. The materials are offered for the production of cast aluminum alloys AL9 and deformed alloys 1571. Results and discussion. The modification of aluminum alloys with a complex nano-dispersion modifier based on the plasma chemical synthesis of Mg2Si and SiC is planned. The crushed grain of modified alloys is achieved by 1.5...2 times, the mechanical strength increases by 12...18% and the corrosion resistance grows too. The results of tests on general corrosion showed that modification with a complex modifier ZrC leads to an increase in the corrosion resistance of alloys due to a decrease in the corrosion rate. The corrosion rate of AL9 alloy in the modified state was reduced from 11.04 10-6 to 9.84 10-6 kg/m2 days, which is 18%. The mechanism of complex nano-disperse modifier in aluminum melt is proposed. Conclusions. The use of such modifiers facilitates the technological process, is environmentally safe, leads to a uniform distribution of introduced nanocomposites, which increases the strength of alloys and their stability. The achieved results showed the effectiveness of modifying aluminum alloys with nano-disperse compositions.

FERROCENE DISPROPORTIONATION REACTIONS IN A PLASMA-LIQUID SYSTEM WITH A ROTATING GLIDING DISCHARGE

A plasma-liquid system with the activation of H2O distillate and 0.1 M ferrocene solution in organic solvents (ethanol, acetonitrile) with a rotating gliding discharge plasma was studied. The research was conducted using various plasma-forming gases (air, Ar, N2, CO2). Determination of plasma parameters was performed by plasma emission spectroscopy methods. It was shown that the plasma of both the rotating gliding discharge and the plasma of the secondary discharge supported by the gliding discharge are non-isothermal. The study of the physicochemical properties of the synthesis products was performed by adsorption, luminescence analysis, polarimetry, chromatographymass spectrometry and NMR methods. It was found that cyclopentadiene ligands of ferrocene disproportionate into saturated cyclic hydrocarbons (cyclopentane and pentane). Also, as a result of plasma chemical synthesis, aromatic compounds (benzene and its derivatives) are formed.

Investigation of the Plasma-Chemical Synthesis of Thin Ga2O3 Films Doped with Zn in One Step in Plasma

Investigation of the Plasma-Chemical Synthesis of Thin Ga2O3 Films Doped with Zn in One Step in Plasma

Energy efficiency of N2 vibrational excitation in the spark-and-glow phases of a long-pulse air discharge at atmospheric pressure

The vibrational excitation of N2 molecules has a significant impact on plasma chemical synthesis, including nitrogen fixation and ammonia formation, by reducing the energy barrier of chemical reactions. However, experimental data for energy efficiency of N2 vibrational excitation is very rare. In this work, vibrational coherent anti-Stokes Raman scattering was applied to a 200 μs long-pulse air plasma, and the time behaviours of rotational and vibrational temperatures of N2 in two different discharge modes, namely the spark and glow modes in the long discharge pulse, were quantified. It reveals that the spark discharge produced a vibrational temperature exceeding 5000 K but with a gas temperature as low as 400 K, while the glow discharge resulted in efficient gas heating with a gas temperature as high as 3500 K and a vibrational temperature higher than 5000 K. Combined with the 0D simulation of the air plasma, it demonstrates that the energy efficiency of N2 vibrational excitation in the glow phase is about three times higher than that of the spark phase. These results provide essential inspiration for further studies of plasma chemical synthesis dominated by N2 vibrational excitation.

Investigation of the Plasma-Chemical Synthesis of Thin Ga2O3 Films Doped with Zn in One Step in Plasma

A process for fabricating Zn-doped (up to 10 at %) β-Ga2O3 thin films by plasma-enhanced chemical vapor deposition has been studied. High-purity gallium, zinc, and oxygen were used as starting materials, and hydrogen was chosen as the carrier and plasma gas. A low-temperature nonequilibrium RF (40.68 MHz) discharge plasma at a reduced pressure (0.01 torr) was used to initiate chemical reactions of precursors. Theplasma-chemical process was monitored using optical emission spectroscopy. Structural properties and morphology of the deposited β-Ga2O3 films were studied by various methods.

The effect of nitric oxide donation on the severity of mitochondrial disfunction to the renal tissue in cardiopulmonary bypass simulation: an experimental study

INTRODUCTION: Acute kidney injury is one of the common complications in cardiosurgical operations with cardiopulmonary bypass (CPB). A number of studies have shown that donation of exogenous nitric oxide (NO) reduces episodes of аcute kidney injury. However, subcellular mechanisms of realization the nephroprotective properties of NO remain unknown. OBJECTIVE: To study the safety of the technology of plasma-chemical synthesis of nitric oxide and to evaluate the effect of the delivery resulting nitric oxide on mitochondrial damage to the renal tissue in the simulation of cardiopulmonary bypass. MATERIALS AND METHODS: Experiment included 12 rams of the Altai breed. Animals were divided into 2 groups: 6 animals were modeled CPB; 6 animals were simulated CPB with NO delivery. Mitochondrial damage was assessed by calcium-binding capacity and transmembrane potential of mitochondria 1 h after weaning from the CPB. The safety of the NO delivery according to the proposed method was assessed by the concentration of nitrogen dioxide on inspiration, the level of methemoglobin. The efficiency of NO delivery according to the proposed method was assessed by the level of stable NO metabolites: endogenous nitrite, nitrate and total concentration of NO metabolites. RESULTS: In the group of animals with NO delivery the average level of transmembrane potential of mitochondria was (171.66 ± 20.41 vs 126.66 ± 18.61; p = 0.00256) and calcium-binding capacity of mitochondria was (1466.66 ± 216.02 vs 866.66 ± 216.02; p = 0.000712) of renal parenchyma. Methemoglobin levels above the recommended thresholds in clinical practice were not recorded in the CPB+NO group. The values of total concentration of NO metabolites and nitrate in the CPB+NO group compared to the CPB group are statistically significantly higher, p = 0.00006; p = 0.0035, respectively. CONCLUSIONS: Plasma-chemical synthesis of nitric oxide is a safe technology, and the use of the resulting nitric oxide in cardiopulmonary bypass leads to a decrease in the severity of mitochondrial dysfunction in the kidney parenchyma.

Carbides of transition metals: Properties, application and production. Review. Part 2. Chromium and zirconium carbides

The properties, application, and methods for producing chromium and zirconium carbides are considered. These carbides are oxygen-free refractory metal-like compounds. As a result, they are characterized by high values of thermal and electrical conductivity. Their hardness is relatively high. Chromium and zirconium carbides exhibit significant chemical resistance in aggressive environments. For these reasons, they have found application in modern technology. Chromium carbide is used mainly as component of surfacing mixtures to create protective coatings that resist intensive abrasive wear, including at elevated temperatures (up to 800 °C) in oxidizing environments. This compound is also used in the manufacture of tungsten-free hard alloys and carbide steels. Chromium carbide, along with vanadium carbide, is used as a grain growth inhibitor in WC – Co hard alloys. Powdered zirconium carbide can be used to polish the surface of items made of ferrous and non-ferrous metals. The properties of refractory compounds depend on the content of impurities and dispersion (particle size). To solve a specific problem associated with the use of refractory compounds, it is important to choose the right method for their preparation, to determine the permissible content of impurities in the initial components. This leads to the existence of different methods for the synthesis of carbides. The main methods for their preparation are: synthesis from simple substances (metals and carbon), metallothermal and carbothermal reduction. Plasma-chemical synthesis (vapor-gas phase deposition) is also used to obtain carbide nanopowders. A characteristic is given to each of these methods. Information on the possible mechanism of the processes of carbothermal synthesis is presented.

Effect of Size on Conductivity of Nanoparticles of NiO Obtained through Plasma Chemical Synthesis

Effect of Size on Conductivity of Nanoparticles of NiO Obtained through Plasma Chemical Synthesis

PECVD Synthesis and Thermoelectric Properties of Thin Films of Lead Chalcogenides (PbTe)1−x(PbS)x

Lead-based ternary-chalcogenide thin films of the (PbTe)1−x(PbS)x system were obtained using the plasma-enhanced chemical-vapor-deposition (PECVD) technique under conditions of a nonequilibrium low-temperature argon plasma of an RF discharge (40.68 MHz) at a reduced pressure (0.01 Torr). High-purity elements were directly used as starting materials, namely Pb, S and Te. Plasma–chemical synthesis was carried out on the surface of c-sapphire and silicon substrate. The physicochemical properties of the films were studied using various analytical methods. The dependence of the Seebeck coefficient, resistivity and power factor on the structural properties and composition has been studied. The thermoelectric characteristics were found to be dependent on film composition. Upon the selection of optimal sulfur concentration, one can increase the power factor compared to single-phase PbS or PbTe films.

STUDY OF NANOMODIFICATION OF NICKEL ALLOY GS3 WITH TITANIUM CARBIDE

The work deals with the fundamentals of nanomodification of the GS3 heat-resisting multicomponent nickel alloy, out of which blades for gas turbine engines are made. The selection of the modifier for the experimental alloy was justified; the technology of acquiring the nanomodifier, using the plasma-chemical synthesis method, was developed; and the calculations of the specific surface of the TiC particles were performed. The required quantity of nanomodifier introduced to the liquid alloy to acquire the set structure was determined experimentally. Through electronic microprobe analysis, introduction to the metal matric of nanoparticles of titanium carbide is approved. Nanomodification allows achieving refinement of the GS3 nickel alloy structure, which is going to provide an opportunity to increase the effective life of gas turbine engine blades.

Nanomechanical and Electrochemical Corrosion Testing of Nanocomposite Coating Obtained on AZ31 via Plasma Electrolytic Oxidation Containing TiN and SiC Nanoparticles

Lightweight magnesium alloys offer excellent benefits over Al alloys due to their high specific strength and damping properties, but they are more prone to galvanic corrosion. Plasma electrolytic oxidation (PEO) coatings reinforced by nanoparticles have been shown to improve corrosion resistance and possess better mechanical properties. A lot of research has been published that focuses on the effect of nanoparticle concentration in the PEO electrolyte solution, and the type of nanoparticle, on the properties obtained. The aim of paper is to study the effect of processing time on the nanoparticle-reinforced PEO coating on AZ31 magnesium alloy. TiN and SiC nanoparticles were produced using plasma chemical synthesis and added to KOH-based electrolyte to develop PEO coatings. The concentration of nanoparticles was kept constant at 0.5 g/L and the treatment time was varied as follows: 1, 2, 3, 5, and 10 min. The coatings were tested for their microstructure, phase, chemical makeup, nano-mechanical properties, and corrosion resistance. Nanoparticles were found to be clustered in the coating and spread unevenly but led to a decrease in the size and number of pores on the PEO coating surface. The corrosion resistance and nano-mechanical properties of the coating improved with treatment time. The hardness and contact modulus of coatings with TiN particles were 26.7 and 25.2% greater than those with SiC particles. Addition of TiN nanoparticles resulted in improved corrosion resistance of the PEO coatings when the processing time was 5 or 10 min. The lowest corrosion rate of 6.3 × 10−5 mm/yr was obtained for TiN-added PEO coating processed for 10 min.

Plasma-chemical synthesis of nanocrystalline "core-shell" structures TiN-Mo-Co

Plasma-chemical synthesis of nanocrystalline "core-shell" structures TiN-Mo-Co

Обработка композитного нанопорошка системы W – C – Co в СВЧ электромагнитном поле

Experiments were carried out on the treatment of the W – C – Co system nanopowders obtained by plasma chemical synthesis in a microwave electromagnetic field with a frequency of 2.45 and 24 GHz in different gas media. The effect of treatment time, power input and carbon content in the treated nanopowder on the yield of tungsten monocarbide WC was investigated.

Сфероидизация нанопорошковых микрогранул вольфрама в термической плазме электродугового разряда

A method for producing tungsten powder consisting of spherical microparticles with dimensions of 20 – 50 µm is considered when processing a granular tungsten nanopowder in a flow of argon electric arc thermal plasma. Experimental studies of plasma chemical synthesis of tungsten nanopowder in a plasma reactor with a limited jet flow during the interaction of tungsten trioxide with a flow of hydrogen-containing plasma generated in an electric arc plasma torch have been carried out. The conditions of spray drying and the properties of a suspension consisting of tungsten nanoparticles have been experimentally determined, ensuring the production of mechanically strong nanopowder microgranules of rounded shape with a homogeneous internal nanostructure that does not contain cavities, with the yield of microgranules with a size of less than 60 µm at the level of 65 %. The influence of the parameters of the plasma processing of nanopowder microgranules in the thermal plasma flow on the degree of spheroidization and the microstructure of the resulting particles has been established.