Plasma Chemical Technology Research Articles

The investigation of movement dynamics of an AC electric arc attachment along the working surface of a hollow cylindrical electrode under the action of gas-dynamic and electromagnetic forces

Stationary electric arc alternating current plasma torches are used today for realization of plasma chemical technologies requiring relatively high energy input. Waste treatment is one these directions. The paper reports on experiment results directed towards the increase in the lifetime characteristics of electrode units of the powerful high-voltage electric-arc AC plasma torches. The solution to the problem of obtainment the uniform wear of a copper hollow cylindrical electrode achieved by the controlled movement of the arc attachment along the working surface was offered. Organization of gas supply in the near electrode area and application of alternating magnetic field ensured movement of arc attachment along the surface with average speed from 2 to 14 m/s. Arc current was about 47 A and 84 A, gas flow rate in near electrode area was about 5 and 4.5 g/s. Due to researches on the experimental prototype of a hollow cylindrical electrode, the erosion of its material reached only 3 μg/C, that enables production of the electrode assembly with life time above 1000 hours at currents in the arc up to 100–200 A.

Plasma-chemical technology of preparation of air-fuel mixture for engine operation on various motor fuel

The experimental researches of a new adaptive system plasma-chemical managements of processes of preparation air-fuel mixtures and burning of fuel in combustion chamber conducted on Russian serial engines in the laboratories of Institute of Engineering Physics, allow to draw a conclusion on opportunity of operation of internal combustion engine on various liquid motor fuels, including kerosene and diesel fuel.

Plasma-chemical technology of treatment of halogen-containing waste including polychlorinated biphenyls

We consider the developed plasma-chemical technology of halogen-containing substances treatment. The paper contains the experimental plant schematic and the positive results obtained after the treatment of tetrafluoromethane, ozone-damaging freon 12, polychlorinated biphenyls (PCB), the waste containing fluoride and chloride organics. The technology is proposed for industrial application.

Bismuth activated alumosilicate optical fibers fabricated by surface-plasma chemical vapor deposition technology

Plasma chemical technology is experimentally applied to the fabrication of a Bi-activated alumosilicate-core pure-silica-cladding fiber preform. To the best of our knowledge, this is the first time this technology has been applied in this way. We measure gain efficiency at pumping by a 1058 nm wavelength Yb fiber laser in a piece of a newly obtained fiber 20 m in length within 100-1200 nm wavelengths band. The gain efficiency reaches as high as 0.2 dB/mW. Bi-activated alumosilicate-core pure-silica-cladding fiber that is not more than 12 m in length serves a basis for a 1 W output power fiber laser emitting at the wavelength of 1160 nm with 8% slope efficiency. We also measure the photoluminescence spectrum and kinetics of Bi centers responsible for laser emission under the excitation of 193 nm wavelength ArF laser pulses.

Double clad tapered fiber for high power applications

We report a novel type of active fiber - tapered double clad fiber suitable for pumping by low brightness sources with large beam parameter product of 50/300 mm x mrad. Ytterbium double clad all-silica fiber (core/1(st) clad/2(nd) clad diameters 27/834/890 mum, NA(core)=0.11, NA(clad)=0.21), tapered down by a factor 4.8 for a length of 10.5 m was drawn from a preform fabricated by plasma chemical technologies. At a moderate Yb-ion concentration and 1:31 core/cladding ratio, the tapered double clad fiber demonstrates 0.9 dB/m pump absorption at 976 nm and excellent lasing slope efficiency. An ytterbium fiber laser with 84 W of output power and 92% slope efficiency, a 74 W superfluorescent source with 85% slope efficiency and amplifiers operating both in CW and pulsed regimes have been realized. All devices demonstrated robust single mode operation with a beam quality factor of M(2)=1.07.

Absorption and luminescence in amorphous silica synthesized by low-pressure plasmachemical technology

A comparison study of as-deposited by the hydrogen-free SPCVD process silicon dioxide with and without fluorine as well as the one in the form of fused materials is performed to define whether glass forming processing affects its optical properties. Raman scattering, optical absorption in the vacuum ultraviolet region as well as luminescence at different temperatures and various excitation conditions are measured. A difference in Urbach rule parameters and intrinsic defect concentrations for different samples is revealed. No significant impact on the structure responsible for Raman scattering is observed.

Multi-dimensional modelling of plasma—solid interaction

The understanding of processes in the boundary layer between plasma and immersed substrates is important in probe diagnostics of plasmas as well as in plasma-chemical technologies. In both cases the standard one-dimensional particle codes are not sufficient for the description of complete processes. This contribution is devoted to the analysis of performance of computer codes prepared for the study of plasma-solid interaction in low-temperature plasma in more dimensions and at low and medium pressures. Besides the standard PIC-MC technique and fluid modelling the more advanced methods were used — solvers of Poisson equation based on Fast Fourier Transform and evolutionary modelling.

Features of Liquid-Fuel Plasma-Chemical Gasification for Diesel Engines

Under the present-day conditions all over the world, the attention is directed to the development of the methods protecting the environment from hazardous emission. One of the most advanced methods for a working process efficiency increasing is the combustion intensification using an air plasma (2000-3500 K). Plasma-chemical technology is used as an effective tool in accelerating the rate of chemical and physical processes. The experimental investigation of the plasma-chemical gasification system has been carried out on the motor bench stand with the diesel-operating volume 624 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The most considerable soot emission reduction of 30% has been achieved at the nominal engine mode

Nitrogen-Containing Paramagnetic Centers in Vitreous Silica

The results of a study on the structure and spectral characteristics of nitrogen-containing paramagnetic defects in vitreous silicas are presented. The UV irradiation, γ-irradiation, and mechanical destruction of nitrogen-doped vitreous silicas, which were synthesized using a plasma-chemical SPCVD technology, were used for the generation of paramagnetic centers. Another technique for producing nitrogen-containing paramagnetic centers was the target-oriented chemical modification of the surface defects of silica with the use of NH3 (ND3) molecules. Paramagnetic centers with free valences at silicon [(≡Si-O-)2Si· (-NH2) and (≡Si-O-)2Si· -N(-Si≡)2] and nitrogen atoms [≡Si-N· -H and ≡Si-N· -Si≡] were detected. The reactivity of nitrogen-centered radicals toward H2 and CO molecules was studied. Quantum-chemical calculations of model systems were employed in the interpretation of the experimental data. The strengths of Si-O and Si-N bonds in vitreous silica were compared.

Plasma-chemical preparation of nanostructured catalysts for low-temperature steam conversion of carbon monoxide: catalytic activity

The “warm walls” (WW) plasma-chemical reactors (PCR) synthesized catalyst samples (types LTC-1–3) give up by activity compared to their industrial analogues; and these synthesized in PCR with “cold walls” (CW) (types LTC-7–9) have a commensurable activity compared to those of the industrial catalysts used by the Bulgarian company CHIMCO-Vratza. Their activities were defined by using a model gas simulating the industrial one for temperatures and a volume rate of the steam–gas mixture similar to those used in the industrial process of low-temperature steam conversion of CO. The enhanced catalytic activity of the plasma-chemically synthesized samples is owing to: the faulty crystal lattice structure of the catalytically active phases; the nanodispersed sample composition (the crystal sizes of the catalytically active phases ranges from 10 to 40 nm); the presence of Cu 2O in the fresh samples, apart form the presence of CuO; the content of cuprous oxides—30–38 mass%; the even distribution of the ultradispersed components, the high porosity, specific surface and dispersity of the phases. Due to the bonding of a portion of the elemental Cu in the CuAl 2O 4 spinel crystal lattice, the plasma-chemically synthesized samples type LTC have a high thermal resistance which exceeds that of their conventional industrial analogues. The high specific surface of the plasma-chemically synthesized samples for low-temperature steam conversion of CO, their homogenous chemical composition, high formation rate of their active surface by reduction, high activity and thermal resistance, represent a precondition to extend the investigation on developing a plasma-chemical technology for their industrial synthesis in the catalyst workshops.

Kinetics of free radicals in the plasma of a spark discharge in methane

The kinetics of reactions in the plasma of a spark discharge in methane at atmospheric pressure is analyzed using numerical simulation, taking account of the gas-dynamic expansion of the channel. The processes leading to the formation and annihilation of CH x radicals are investigated and the conditions under which their maximum concentration is reached are determined. The results obtained are of interest for plasma chemical technologies for processing natural gas.

New ferro-carbon adsorbents for magnetically guided transport of anti-cancer drugs

The plasmachemical technology of iron–carbon adsorbent production was developed and optimized. The adsorbent was thoroughly studied by physical, chemical and biological methods, and was found to have high sorption capacity, long desorption time, high magnetization and low toxicity. The adsorbent is intended to be used for magnetically guided transport and forming a depot of anti-cancer drugs in the tumor zone.

The use of liquid precursors in plasmachemical technology of obtaining a-SiC:H thin films

The analysis of experimental data has shown promise of our technological approach in obtaining hydrogenated amorphous silicon carbide films (a-SiC:H). The a-SiC:H films have been received by a plasmachemical decomposition of CH 3SiCl 3 steams, in the plasma of radio frequency (RF)-discharge. The negative potential is supplied on a substrate. For obtaining n-conductivity, the nitrogen was added in a gas mixture. For p-conductivity, BCl 3 steams were entered which were decomposed in the plasma. On the basis of the theoretical calculation of a-SiC by the recursion method of Haydock, it suggested the mechanism of influence of amorphouzation and hydrogenation on the electronic structure of the silicon carbide that is necessary for understanding the physics of the process of hydrogenation of amorphous thin films.

Strong-current arc discharges of alternating current

The review of experimental results of strong current (I=10-10/sup 4/ A) quasi-stationary ac discharges in high pressure (P/spl ges/10/sup 5/ Pa) gases is presented. Structure and properties of alternating current arc in vortex, turbulent flows of air, argon, nitrogen, and hydrogen were investigated. The existence of two arc discharge column regimes, contracted and diffusion, has been established. The processes of heat exchange between the arc and surrounding gas for these regimes were studied. Processes in the discharge volume, mechanisms of charge transition in the electrodes neighbor zone, and electrodes' erosion in the spot and without-spot regimes were investigated in dependence of current quantity, gas pressure, and electrode material. Water-cooled copper electrodes were used as well as high-melting ones (tungsten, molybdenum, and other). Prototypes of powerful (N=10-10/sup 3/ kW) ac plasma generators, intended for usage in different plasma-chemical technologies including toxic wastes destruction and treatment, were designed, developed, and manufactured on the basis of these investigations.

Fabricating lead zirconate-titanate powder and piezoceramics based on its using a plasma-chemical technology

A plasma-chemical method for fabricating lead zirconate-titanate powder is considered. The effect of the temperature at which the powder is separated in vortex precipitators on the physicochemical properties of the powder is described. The special features of shaping and the properties of piezoceramics based on the powder are investigated.

Novel plasma chemical technologies — PPCP and SPCP for control of gaseous pollutants and air toxics

The pulse corona induced plasma chemical process (PPCP) and the surface discharge induced plasma chemical process (SPCP) represent novel technologies for generating copious active radicals under ordinary temperature and pressure for control of gaseous pollutants ( NO x , SO x VOCs) and air toxics (Hg and other readily vaporized metals, trechloroethane, trichloroethylene, freons, toluene, dioxines, etc.) as well as odors. PPCP and SPCP are completely dry processes having a simple construction, and their overall cost (both initial and running) is one of the lowest among the processes for control of gaseous pollutants They can he combined with a wet ESP, a bag-filter with absorbent powder coat, a catalyst bed, or an active charcoal bed for the final removal of the reaction products.

Plasmachemical technology for high-dispersion products

Experimental results of the synthesis of ultrafine powders (UFP) under conditions which characterize quasi-equilibrium, as well as non-equilibrium low temperature plasma (LTP), are summarized. The basic steps involved in the plasmachemical processes for producing UFP are considered. The process of powder vaporization is limiting, determining the characteristics of the plasma generator. To obtain UFP with high purity, the reactions must take place in the gaseous phase. Quenching can be accompanied by a chemical reaction, and as a result, powders are obtained with either defects in the crystal structure or in the amorphous state. The mean particle size of UFP is 5 to 100 nm (specific surface ⩽ 400m2g−1). Quenching determines the phase content of the specific UFP.

Pulse corona induced plasma chemical process: a horizon of new plasma chemical technologies

Abstract

Plasma Chemical Technology—The Future of the Chemical Industry

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXT Plasma Chemical Technology—The Future of the Chemical IndustryF. B. Vurzel and L. S. PolakCite this: Ind. Eng. Chem. 1970, 62, 6, 8–22Publication Date (Print):June 1, 1970Publication History Published online1 May 2002Published inissue 1 June 1970https://doi.org/10.1021/ie50726a004RIGHTS & PERMISSIONSArticle Views209Altmetric-Citations14LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (4 MB) Get e-Alerts