Low-temperature Discharge Plasma Research Articles

Phenol Degradation Features in Aqueous Solutions upon Dielectric-Barrier Discharge Treatment

The formation kinetics and mechanism were studied for the intermediate and final products of degradation of aqueous phenol solutions in air and oxygen low-temperature dielectric-barrier discharge plasmas in a reactor with different geometric arrangements of electrodes. It was shown that the plasma-enhanced oxidation of phenol could be described in the general form by the well-known mechanism of enzymatic oxidation of toxic pollutants (β-mechanism). The estimated effective rate constant of phenol degradation in an aqueous solution in an О2 plasma in reactors with the parallel-plate and coaxial arrangement of electrodes was 2.2 × 10–3 s–1 and 5.8 × 10–2 s–1, respectively. It was found that the potential toxicity of solutions after treatment was 7.5 times lower than that of the untreated solutions.

Kinetics of Gaseous Product Formation in the Surface Treatment of Polypropylene with Nitrogen–Oxygen Plasmas

The results of measurements on the composition and the formation rates of gaseous products in the surface treatment action of polypropylene with a low-temperature dc discharge plasma in a nitrogen–oxygen mixture are reported. The amount of oxygen in the mixture was varied within 0–100%. It was found that almost stoichiometric plasma-induced oxidative degradation occurred in an oxygen plasma, whereas the buildup of oxygen-containing functional groups on the surface took place in a mixed nitrogen–oxygen plasma at a nitrogen content of ∼10–60%.

The Kinetics of Plasma-Induced Degradation of Organic Pollutants in Sewage Water

The processes of treatment of actual surface water and model solutions in a low-temperature dielectric-barrier discharge (DBD) plasma were studied. The general evaluation of the efficiency of the plasma treatment procedure for sewage purification was made, and a conclusion on the reasonability of its use in combination with conventional treatment methods was drawn. Schemes of conversion processes for organic compounds upon DBD treatment of surface water were proposed, and the effective rate constants of corresponding reactions were estimated (for phenol, k = 0.46 × 10–5 s–1). It was found that the reaction of oxidation of pollutants in solutions modeling surface runoff occurs in the diffusion region.

Low-frequency electromagnetic solitary and shock waves in an inhomogeneous dusty magnetoplasma

It is shown that the nonlinear dynamics of one-dimensional Shukla mode [Phys. Lett. A 316, 238 (2003)] is governed by a modified Kortweg–de Vries–Burgers equation. The latter admits stationary solutions in the form of either a solitary wave or a monotonic/oscillatory shock. The present nonlinear waves may help to understand the salient features of localized density and magnetic field structures in molecular dusty clouds as well as in low-temperature laboratory dusty plasma discharges.

A new low-temperature plasma discharge reactor for polymerisation of unsaturated compounds

The polymerisation of amphiphilic monomers effects a stabilisation of shape and size of the micelles formed by these amphiphiles. The polymerisation was carried out in aqueous media initiated by low-temperature plasma in a dielectric barrier discharge reactor. To our knowledge this method has not been reported in contrast to the UV polymerisation. A dependence of the turnover and the molecular weight of the polymers on treatment conditions was found. The low-temperature plasma polymerisation shows advantages in comparison with the UV-initiated polymerisation.

Instability of a broadband Langmuir wave spectrum in a dusty plasma

The nonlinear interaction between broadband Langmuir waves and electrostatic dust–acoustic perturbations in a uniform collisional dusty plasma is considered, taking into account the combined effects of the Langmuir wave ponderomotive force and the electron Joule heating nonlinearity. This coupling is governed by a Liouville equation for a Langmuir wave packet and an equation for a dust–acoustic perturbation that is driven by the ponderomotive and thermal forces of the random phase Langmuir waves. The mode coupling equations are then Fourier decomposed to derive the nonlinear dispersion relation. The latter is analyzed numerically for a Gaussian Langmuir wave spectrum, by taking parameters that are relevant for low-temperature dusty plasma discharges. It is found that a broadband spectrum of Langmuir waves is subjected to a rapidly growing modulational instability in a dusty plasma.

Instability Produced by the Ion Drag Force in Dusty Plasmas

It is shown that the ion drag force acting on the charged dust grains can cause an instability of electrostatic waves in dusty plasmas. The instability can be responsible for the great void, which is observed in low-temperature dusty plasma discharges.

In situ calibration of microchannel-plate-based x-ray pinhole camera for observation of magnetically trapped plasma

The electronic amplification gain of a microchannel plate (MCP), as employed for detector and image amplifier of an x-ray pinhole camera, tends to decrease as the output current increases, posing problems both in quantitative analyses and in construction of a three-dimensional emissivity distribution. We report that the output-current dependent MCP gain is described in a simple empirical formula that is determined by an in situ calibration experiment using a steady-state low-temperature discharge plasma. We examine the validity of the formula affirmatively in correcting raw data of x-ray images of magnetically trapped hot plasma. It is also demonstrated that the correction leads to a three-dimensional distribution of soft x-ray emissivity in a quadrupole-mirror-trapped hot plasma that is consistent with other indirect measurements.

Experimental studies on intermittent phenomena in a plasma

An intermittent process occurring in a low-temperature plasma discharge has been investigated. During a continuous scan of the discharge voltage, one kind of intermittency evolves from random upward bursts to a periodic oscillation, while the other evolves to chaos from random downward bursts. A critical exponent concerning the onset of the latter intermittency is quantitatively determined to be ??=?0.912.

Analysis of low-temperature surface discharge plasma products from gaseous organic compounds

Nonequilibrium low-temperature discharge plasma decomposition products of 1000 ppm gaseous organic compounds contaminated in atmospheric pressure air, nitrogen, or oxygen, such as chlorofluorocarbon (CFC-113), organic chloride (trichloroethylene), and carbon tetrachloride, were studied for a better understanding of the decomposition mechanism of the plasma processing. A gas chromatograph-mass spectrometer was used as a main analyzing equipment. When the decomposition rate is not high (20-80%) for CFC-113, many various halogenated carbons or halogenated hydrocarbons are identified as intermediate products by the plasma processing. As the electric discharge power consumption increases, the decomposition rate of CFC-113 increases and intermediate products decrease. At the decomposition rate of more than 90%, some elemental products of hydrochloric acid, carbon dioxide, and nitrogen suboxide are recognized as final products. On the other hand, if the environmental gas is pure nitrogen without any oxygen and water vapor, the decomposition products are still intermediate with sufficient electric discharge power consumption, suggesting the existence of double decomposition mechanisms of nitrogen radicals and oxygen radicals. In the case of trichloroethylene decomposition, harmful intermediate decomposition products were observed when the decomposition rate was 20-90%.

Transformation of polymers in a stream of low‐temperature arc discharge plasma

AbstractSpraying of polymer materials in a low‐temperature plasma stream is a very efficient way of depositing polymer coatings on large surfaces. The deposition of powdered polymers by an arc discharge plasma flow and spraying from the bulk have been compared. The properties of powdered polymers do not change considerably during transportation by the stream because of the short residence of the particles in the plasma. When spraying from the bulk, polymers are transported in the form of melt droplets (polyethylene, polycarbonate) or in gaseous phase (polytetrafluoroethylene); autohesion of the droplets or secondary polymerization occurs, respectively, on the substrate surface. This process offers high‐quality thin films and coatings whose structure depends significantly on the characteristics of the substrate as well as on the structure of the source polymer. Obtained polymer coatings contain nitrogen and oxygen entrapped from the atmosphere as well as (on the glass surface) the products of glass etching. This fact enables one to vary widely the properties of the coatings. Furthermore, the problem of obtaining combined protective coatings in which polymer melt fills the pores between metal particles can be solved successfully in a united technological cycle including plasma spraying of the polymer and the metal. © 1995 John Wiley & Sons, Inc.

Discharge-plasma-x-ray-laser resonant couples for x-ray nonlinear optics.

We demonstrate the feasibility of x-ray resonant nonlinear effects (absorption saturation and nonlinear refractive index) for the radiation of some of existing x-ray lasers (XRL's) when it propagates in relatively low-temperature discharge plasmas different from those used in the respective XRL. We identified 12 resonant ``XRL-plasma'' couples suitable for such effects.

Reflection of Pseudowaves

Ion bursts (pseudowaves) in a low temperature discharge plasma are reflected from the potential barrier of a gridded energy analyzer. The energy of the reflected ions increases monotonically with the increasing potential.