Plasma Chemical Process Research Articles

Direct One-Stage Plasma Chemical Synthesis of Nanostructured Thin Films of the System β-Ga<sub>2</sub>O<sub>3</sub>-GaN of Different Composition

For the first time, nanostructured thin films of the β-Ga2O3−GaN system were obtained by plasma chemical deposition from the gas phase (PECVD) on c-sapphire substrates. High-purity metallic gallium, as well as high-purity gaseous nitrogen and oxygen were used as sources of macro components. The low-temperature nonequilibrium plasma of an inductively coupled HF (40.68 MHz) discharge at a reduced pressure (0.01 Torr) was the initiator of chemical transformations between the starting substances. A mixture of oxygen and nitrogen was used as a plasma-forming gas. The plasma chemical process was studied using the optical emission spectroscopy (OES) method. The obtained thin films of the β-Ga2O3−GaN system with a GaN phase content of 2 to 7% were characterized by various analytical methods.

Interfacial strength and its regulation in the carbon monofiber/epoxy binder system

The strength of polymer composite materials (CMs) is largely determined by the strength of interfacial interactions at a fiber/matrix interface. In this work the strength in a unit cell of CM carbon monofiber/cured epoxy matrix is investigated. The relevance of the work is due to direct measurements of strength at the monofiber/matrix interface, excluding defects of micro-droplet and technological errors associated with impregnation in a traditional assessment of polymer composite materials strength. Changes of surface morphology and energy characteristics of fibers in plasma chemical treatment process is shown. The study of fiber surface energy and formation of carbon monofiber/epoxy matrix interface of carbon fiber reinforced composite unit cell was carried out on the specially developed original device Drop-Sting test. Micro pull-out test was used to investigate the shear mechanical properties of interface and to determine the strength of carbon fiber reinforced composite unit cells before and after treatment in oxygen discharge plasma. It is shown that the increase in the strength of the monofiber/matrix interfacial interface after the treatment of carbon fiber in plasma occurs due to the increase in the surface energy and wettability of monofibers.

Non-Linear Phenomena in Voltage and Frequency Converters Supplying Non-Thermal Plasma Reactors

Atmospheric pressure cold plasmas have recently been the subject of intense research and applications for solving problems in the fields of energy, environmental engineering, and biomedicine. Non-thermal atmospheric pressure plasma sources, with dielectric barrier discharges, plasma jets, and arc discharges, are non-linear power loads. They require special power systems, which are usually designed separately for each type of plasma reactor, depending on the requirements of the plasma-chemical process, the power of the receiver, the type of process gas, the current, voltage and frequency requirements, and the efficiency of the power source. This paper presents non-linear phenomena accompanying plasma generation in the power supply plasma reactor system, such as harmonic generation, resonance, and ferroresonance of currents and voltages, and the switching of overvoltages and pulse generation. When properly applied, this can support the operation of the above-mentioned reactors by providing improved discharge ignition depending on the working gas, thus increasing the efficiency of the plasma process and improving the cooperation of the plasma-generation system with the power supply.

An Investigation of Fly Ash and Slag Processing and Fiber Production Using Plasma Technology

As the world’s population grows and resource consumption rises, there will be an increase in household waste and, consequently, the fly ash and slag from after the incineration of this waste need to be properly recycled or used as secondary raw materials in other industries. The authors of this work propose an innovative technology that has not yet been studied much in the literature; the obtained slag and fly ash are processed by plasma technology, and from those, fiber is formed. As shown by SEM studies, the raw material (before plasma–chemical treatment) consists of irregularly shaped granules or rod-shaped microforms. EDS studies show that both the original material and the products obtained after plasma–chemical processing are composed of various metal elements, but they make up a significantly small part, as the predominant elements are C, O, Cl, Si, and Ca. BET studies show that when the fiber is obtained with a plasma torch power of 55.5; 55.6 and 74 kW, respectively, the specific surface area is 11.9; 8.5 and 3 m2/g. It is worth noting that the raw material obtained after plasma–chemical processing is sufficiently clean and harmless to the environment, so it can be used as a secondary raw material, e.g., for the production of thermal insulation, in the production of catalysts, as a component in the production of concrete, or in other industries.

The Synthesis and Analysis of the Cytotoxicity of Al2O3-Supported Silver Nanoparticles Prepared by the Plasma Chemical Process Initiated by Pulsed MW Radiation in the Al2O3-Ag Powder Mixtures.

An original plasma chemical process initiated by microwave discharge in a mixture of metal and dielectric powders was applied to prepare specific materials, which consisted of microsized spherical particles of aluminum oxide covered with silver nanoparticles. The prepared materials are highly uniform in shape, size distribution, and composition. Their cytotoxicity was investigated using the human cell lines MCF7, HEK293T, A549, and VA-13 and the bacterial strains E. coli JW5503 (ΔtolC) and E. coli K12. Their cytotoxicity was found not to exceed the cytotoxicity of the starting materials. Thus, the prepared materials can be considered highly promising for catalysis and biotechnology applications.

Plasma-Chemical Processing of Fuel Oil

Plasma-Chemical Processing of Fuel Oil

Development and Performance Evolution of Medium-Pressure He/SF6/O2-Based Plasma and Wet Chemical Etching Process for Surface Modification of Fused Silica

Development and Performance Evolution of Medium-Pressure He/SF6/O2-Based Plasma and Wet Chemical Etching Process for Surface Modification of Fused Silica

Plasma-chemical waste processing: numerical analysis and experiment. Part 4. Ash-and-slag waste and oil refinery wastes

Plasma-chemical waste processing: numerical analysis and experiment. Part 4. Ash-and-slag waste and oil refinery wastes

Optimization of PDMS Surface Treatment Using Atmospheric Pressure Plasma for Microfluidic Applications

Abstract Polydimethylsiloxane (PDMS) is widely used for microfluidic and biomedical applications because of its chemical inertness and affordability. However, its low surface energy limits its adhesion properties, thus necessitating mandatory surface activation, via plasma treatments or chemical processing, especially for improving its hydrophilicity. In this study, we employed an atmospheric pressure plasma jet (2 W) in order to enhance the PDMS surface adhesion for application in microfluidic devices. Treatment variables, including exposure and recovery time and adhesion quality, were investigated. It was possible to achieve a minimum exposure time of 15 s/cm2 for thin PDMS (sheet, 250 μm) and 30 s/cm2 for thick (resin, 3 mm) PDMS. A robust and efficient methodology for scaling the jet system treatment of larger areas was developed. Additionally, we examined the effect of ambient humidity on the plasma treatment. Results showed that water adsorption on PDMS-treated surfaces indicated a difference between the well-established contact angle method for determining surface hydrophilicity (and thus, its adhesion) and the real adhesion properties of the treated surfaces.

Plasma-Enhanced Chemical Vapor Deposition of Thin GaS Films on Various Types of Substrates

Gallium monosulfide (GaS), a representative of Group III monochalcogenide layered materials, is a wide-bandgap semiconductor. It is considered an ideal material for light detectors in the blue and near ultraviolet ranges of the spectrum. In this work, for the first time, the method of plasma-enhanced chemical vapor deposition (PECVD) was applied to obtain thin GaS films on various substrates, where high-purity gallium and sulfur served as starting materials. To initiate the interaction between the reactants, a nonequilibrium RF discharge (40.68 MHz) plasma at a pressure of 0.1 torr was used. The influence of the substrate nature on the stoichiometry, structure, and surface morphology of GaS films has been studied. The plasmachemical process was monitored using optical emission spectroscopy.

Plasma-Chemical Processing of Fuel Oil with Lignite

Plasma-Chemical Processing of Fuel Oil with Lignite

Plasma-chemical waste processing: numerical analysis and experiment. Part 3. Rubber of used tires

Plasma-chemical waste processing: numerical analysis and experiment. Part 3. Rubber of used tires

Plasma-chemical waste processing: numerical analysis and experiment. Part 2. Fuels and lubricants

Plasma-chemical waste processing: numerical analysis and experiment. Part 2. Fuels and lubricants

Плазмохимический синтез нитропроизводных аценафтена в поле токов высокой частоты при пониженном давлении

Plasma-chemical processing devices are widely used in practice and are an integral part in microelectronics, medicine, light industry and nanotechnology. In addition, they are used as methods for modifying the modern materials surfaces and in liquids processing. The paper considers preparation of the aromatic compound nitro derivatives under the action of capacitive high-frequency electrodeless discharge at the gas--liquid interface with the reduced pressure. During the plasma-chemical treatment of the reaction mixture containing the 1,2-dihydroacenaphthylene (acenaphthene), its complete conversion was observed, which was confirmed by detection of the acenaphthene mono- and dinitro-derivatives, as well as of the side chain oxidation products, in the reaction products. The proposed method of implementing nitration reaction of the aromatic substances, which belongs to the new instrumental methods of organic synthesis along with photochemistry and electrochemical synthesis, allows direct binding of the molecular nitrogen and oxygen into the valuable nitrogen-containing organic compounds. Study results demonstrate effective introduction of the plasma chemistry methods in chemical technology not only for the purposes of oxidative destruction of the organic substances, but also as the physicochemical tools for the fine organic synthesis allowing selective functionalization of the polynuclear aromatic compounds

Plasma-chemical waste processing: numerical analysis and experiment. Part 1: Medical-biological waste and fuel biomass

The paper presents the results of thermodynamic calculations and experimental studies of plasma processing of biomedical waste and fuel biomass, including waste from the woodworking industry and agriculture, which have shown the promise of using plasma-chemical technology for processing various wastes with production of combustible gas and inert mineral material. Comparison of the experimental results and calculations showed their satisfactory agreement. Both in calculations and in experiments, no harmful impurities were found in the products of plasma processing of the investigated wastes.

Developing generalized model representations of thermal shock for local non-equilibrium heat transfer processes

Objectives. Processes of energy transfer in solids and resultant thermal loads are widespread in nature and technology. This explains the scientific and practical significance of constructing a theory of these processes, as well as developing effective methods for studying the modeled concepts developed on this basis. The purpose of such studies is to determine basic flux patterns of complex processes occurring especially under conditions of powerful energy impacts in various technological operations. These include plasma-chemical processing of materials, their processing in infrared furnaces and solar plants, intense heating of materials carried out by laser or electron beams, and the use of powerful radiation emitters for thermal hardening and hardening of the surface of products. In these cases, the phenomenon of thermal shock arises, forming one of the central topics in thermomechanics and strength physics of solids. The present work considers an open theoretical problem of thermal shock in terms of a generalized model of dynamic thermoelasticity under conditions of a locally nonequilibrium heat transfer process. Depending on the type and curvature of the boundary surface of the considered massive body, the model can be used to study the problem in three coordinate systems: cartesian coordinates—a massive body bounded by a flat surface; spherical coordinates—a massive body with an internal spherical cavity; cylindrical coordinates—a massive body with an internal cylindrical cavity. Three types of intensive heating are considered: temperature heating, thermal heating, and heating by medium. Following the development of an analytical solution, the results of conducted numerical experiments are presented along with their physical analysis.Methods. The study applies methods and theorems of operational calculus according to the theory of special functions.Results. Generalized model representations of thermal shock are developed in terms of dynamic thermoelasticity for locally nonequilibrium heat transfer processes simultaneously in three coordinate systems: Cartesian, spherical, and cylindrical. The presence of curvature of the boundary surface of the thermal shock area substantiates the initial statement of the dynamic problem in displacements using the proposed corresponding “compatibility” equation.Conclusions. A generalized dynamic model of the thermal reaction of massive bodies with internal cavities simultaneously in Cartesian, spherical, and cylindrical coordinate systems under conditions of intense temperature heating, thermal heating, and heating by medium is proposed. The model is considered in terms of displacements based on local nonequilibrium heat transfer. A numerical experiment carried out according to the obtained analytical solution for stresses forms a basis for a description of the wave nature of the propagation of a thermoelastic wave. A comparison with the classical solution is made without taking into account local nonequilibrium. The calculation of engineering relations carried out on the basis of the operational solution of the problem is important in practical terms for the upper estimate of the maximum thermal stresses.

Renewal of Lead Battery Electrodes Using a Plasma—Chemical Processing Method

The increasing use of renewable energy sources increases the need for electricity storage systems. In this work, the possibility of renewing worn-out battery Pb electrodes by applying Ar and O2 gas plasma in a magnetron vacuum system was investigated. As shown by the SEM results of the surface of Pb electrodes, after exposure to O2 plasma, the surface of Pb electrodes consists of irregularly shaped microstructures. Analyzing the XRD results revealed that the spectrum peaks of the Pb4O3SO4 compound are more pronounced in the case of the electrodes of the worn battery than those electrodes that were exposed to Ar and O2 gas plasma. It was observed that the process of renewing Pb electrodes in Ar and O2 plasma has a positive effect. This effect is also confirmed by the results of EDS studies, as the chemical compounds that inhibit the charge/discharge process are reduced, and the percentage of pure lead increases from 68.2% (in the case of worn electrodes) to 81–82% (when the worn electrodes were processed using Ar and O2 plasma).

Dry Emission Control Technology for Glass Melting Furnace by Plasma-Chemical Hybrid Processing

To use the continuous combustion of fossil fuels as a sustainable energy source, a low-cost and energy-saving exhaust gas treatment for NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> , SO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> , and suspended particulate matter is required. The plasma hybrid exhaust gas treatment technology proposed by the authors is not only a method of plasma treatment, but also a method that combines it with a chemical process, such as chemical solution stabilizer, to clean exhaust gas. This study reports the simulation and application of glass melting furnace exhaust gas treatment as a practical result of the plasma chemical hybrid process (PCHP). In the experiment, higher removal efficiencies of NO, NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> , and SO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> (33, 16, and 55%, respectively) were obtained. The energy efficiency of NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> removal by evaluating the electrical power using the cost of NaOH and the power of ozonizers was measured to be 23 g(NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> )/kWh. From comparison, the simulated and experimental temperature distributions and NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> concentration were found to be in good agreements. This indicates that numerical design simulation produces a satisfactory result. PCHP can potentially be the most suitable method for exhaust gas treatment in glass melting furnaces.

The Design of a Python Library for the Automatic Definition and Simulation of Transient Ionization Fronts

In recent years, the interest in nonthermal plasma dynamics has grown significantly, within both industry and research. This has been driven by the development of several novel cold plasma technologies across a wide range of different fields, for example, for plasma medicine, chemical processing, pollution control, and surface treatment. The optimization of these technologies relies heavily upon the understanding of gas discharge plasmas: their generation, electrical characteristics, and interaction with their surroundings. Moreover, the manifestation of nonthermal plasmas in the form of streamers is of high relevance and critical importance to high voltage insulation technology, and has further significance to geophysical research concerning atmospheric discharges. The present work describes the development of the StrAFE (Streamers on Adaptive Finite Elements) package, a dedicated Python library built atop the popular open-source FEniCS finite element software, designed with the objective to simplify and to automate the solution of ionization front models. The library features support for mesh adaptivity, distributed memory parallelism, and an intuitive programming interface, while providing an exceptionally high level of user configurability. This article presents the software implementation, describes its features, and presents several code verification studies performed within simple and complex domains. It is concluded that the numerical results gained from this open-source framework are comparable to other well-established software in terms of accuracy. Therefore, it further demonstrates the great potential for open-source software to make significant contributions to technologies involving nonthermal plasmas, ionization fronts, and gas discharges.

Tribological behavior of diamond particles reinforced hafnium matrix composite coatings on Ti6Al4V

The diamond particles reinforced hafnium matrix composite coatings are prepared by the double glow plasma surface alloying technique combined with the microwave plasma chemical vapor deposition process (MPCVD). The effect of the Hf diffusion layers and diamond particles on their phase transformation, microstructure evolution, and wear behavior is systematically investigated. The results reveal that the surface of the Hf-alloying coating which is fabricated by plasma surface metallurgy emerged discrete micropores due to the Kirkendall effect during the plasma reverse sputtering. With the reverse sputtering time increasing, the general pore size increases, and the deposition layer has been completely sputtered out, leaving the Hf diffusion layer with a thickness of about 10 μm. After diamond particles deposition by MPCVD, the diamond particle reinforced hafnium matrix composite coatings with carbide and diamond coexisting were formed. The wear experiments were conducted in ambient air with a reciprocating friction tester, demonstrating that the diamond particle reinforced hafnium matrix composite coatings exhibited good antifriction performance with the decrease of wear rate by ∼8 times due to the lubrication effect of the diamond and graphite particles.