Barrier Discharge Type Research Articles

Effect of low-temperature plasma treatment on tailorability and thermal properties of wool fabrics

Dielectric barrier discharge type of plasma reactor was used for the low-temperature plasma (LTP) treatment of the wool fabrics. Air was used as the non-polymerizing gas for the plasma treatment at different time intervals. Low-stress mechanical properties of the treated and untreated wool fabrics were evaluated using Siro-fast technique which revealed that the tensile, bending, compression, shear, dimensional stability and surface properties were altered after the LTP treatment. Other properties such as thermal conductivity, thermal resistance and pilling propensity were also evaluated. The surface topographical changes of the wool fibres after LTP treatment were analysed by scanning electron microscopy. The changes in these properties are supposed to be related closely to the interfibre and interyarn frictional force and increased surface area of the fibres induced by the etching effect of plasma.

Wake flow stabilization with DBD plasma actuators for low Re numbers

We propose to study the stability properties of a wake air flow forced by electrohydrodynamic (EHD) actuators. EHD actuators can add momentum to the flow around an object in regions close to the wall. Hence, we adopt the hypothesis of the forcing actuation modeled as a slip-wall condition.We study the flow around a cylinder modified by EHD actuators, dielectric barrier discharge (DBD) type, by means of particle image velocimetry (PIV) measures. For the sake of simplicity we observed flows at low Reynolds(Re) numbers (∼ 200) where the flow is mainly two-dimensional. As the forcing frequencies, characteristic of DBD, are much higher than the natural shedding frequency of the flow (kHz vs. Hz), we consider in this work only the forcing actuation as stationary. The actuators are disposed symmetrically near the boundary layer separation point. Thus, flow symmetry is conserved, as it remains weakly non parallel. This aspect allows us to perform stability analysis of the flow and to determine its characteristics which are governed by a strong mean flow correction. We also present results on the global mode evolution under forcing.The main motivation of this work is to optimize the forcing on the flow, leading to a more effective energy consumption of EHD actuators.

Plasma assisted heterogeneous catalytic oxidation of carbon monoxide and unburned hydrocarbons: Laboratory-scale investigations

The use of upstream plasma treatment and ozone injection for the amelioration of the performance of diesel oxidation catalysis was investigated. Experiments presented here were performed in preparation for full scale tests on diesel engines. A significant augmentation of the oxidation rate of carbon monoxide was observed when plasma was applied upstream of a diesel oxidation catalyst and was attributed to a heterogeneous reaction of ozone with carbon monoxide. This observation led to ozone injection being investigated as an alternative to the direct application of dielectric barrier discharge type plasma to the gas upstream of the diesel oxidation catalyst. Results are presented about the two modes of the combination of the non-thermal plasma with the catalyst when they were applied during the catalyst light off, and are compared in terms of pollutant removal and energy cost for carbon monoxide and hydrocarbons. Mechanisms for these effects are proposed and the performances of the two approaches are discussed.

Ｏ２／Ｎ２ガスを用いた６０Ｈｚ非平衡大気圧プラズマによるソルダーレジストとドライフィルムの表面改質

This study examined surface modification of a solder resist and dry film resist by 60 Hz nonequilibrium atmospheric pressure plasma using O2/N2 gas. Surface modification is extremely important for fine-pitch printed wiring board (PWB) manufacturing processes. Results show that the 0.1% of O2/N2 mixing ratio was the best condition for surface modification at a 0.45 m/min PWB substrate transportation speed. The triplet oxygen atom (3P) density and the quintet nitrogen atom (4S) density were measured using vacuum ultraviolet absorption spectroscopy (VUVAS). The quintet nitrogen atom was measured using VUVAS for the first time ever reported. The gas temperature, electron density, and NO-γ intensity were also evaluated. A triplet oxygen atom with extremely high density of 4.7 × 1013 cm-3 was obtained at a 0.1% O2/N2 mixing ratio, and the density value was higher than that of the conventional atmospheric pressure plasma such as dielectric barrier discharge (DBD) type. The behavior of the triplet oxygen atom density and NO-γ intensity as a function of O2/N2 mixing ratio correlated strongly with surface modification. The 60 Hz nonequilibrium atmospheric pressure plasma using low-cost O2/N2 gas with a 0.1% O2/N2 mixing ratio is expected to be useful for surface modification during fine-pitch PWB manufacturing.

Charge distributions of aerosol dioctyl sebacate particles charged in a dielectric barrier discharger

The collection efficiencies of submicron aerosol particles using a two-stage, dielectric barrier discharge (DBD) type electrostatic precipitator have been reported previously [ Byeon et al. (2006). Collection of submicron particles by an electrostatic precipitator using a dielectric barrier discharge. Journal of Aerosol Science, 37, 1618–1628]. In this paper, the charge distributions of aerosol dioctyl sebacate (DOS) particles, which had a mobility equivalent diameter of 118, 175, and 241 nm and were charged in a DBD charger, were examined using a tandem differential mobility analyzer (TDMA) system at applied voltages of 9–11 kV and frequencies of 60–120 Hz. The mean number of elementary charges for positively or negatively charged particles increased slightly with increasing applied voltage or frequency. However, the number of elementary charges increased significantly with increasing particle size. At any applied voltage and frequency, the charge distributions of these particles of these sizes indicated asymmetric bipolar charging. The positive-to-negative charge ratios were 10.4, 4.7, and 3.0 for particle sizes of 118, 175, and 241 nm, respectively, at a DBD voltage and frequency was 9 kV and 60 Hz, respectively. Fluorometric analysis showed that average positive-to-negative charge ratios were 11.5, 4.9, and 3.7 for particle sizes of 118, 175, and 241 nm, which agrees well with the TDMA results. Further fluorometric analyses with larger particles (514 and 710 nm) and higher frequencies (1 and 2 kHz) showed that the positive-to-negative charge ratio reached almost unity with increasing particle size or frequency.

Surface analysis of groundwood paper treated by diffuse coplanar surface barrier discharge (DCSBD) type atmospheric plasma in air and in nitrogen

Abstract Paper made of groundwood was surface treated by atmospheric plasma of the diffuse coplanar surface barrier discharge (DCSBD) type in air and in nitrogen. Changes in surface composition and chemical bonding of the constituent elements were studied by X-ray photoelectron spectroscopy (XPS), and alterations in wetting were examined by contact angle measurements. Air plasma treatment resulted in strong oxidation but no N incorporation, while the ratio of the area of the O1 component (binding energy 532.1 eV) to that of the O2 component (533.2 eV) decreased, reflecting an increase in the proportion of O in C–O type bonds. Nitrogen plasma treatment followed by exposure to the atmosphere resulted in a slight N incorporation (1.5 at.%) and oxidation even more intense than observed for air plasma treatment. The O1/O2 ratio slightly increased, implying more O in C=O type bonds. The time dependence of surface oxidation showed a local maximum at treatment time of approximately 2 s for both the air and nitrogen plasmas.

Toluene removal by a DBD-type plasma combined with metal oxides catalysts supported by nickel foam

The performance on toluene removal in a dielectric barrier discharge (DBD) type plasma system under different background gases, including N 2, Ar, N 2/Ar, and N 2/O 2 was studied at room temperature and atmospheric pressure. For comparison, another laboratory-scale plasma-catalysis system was set up and four kinds of metal oxides, i.e., copper oxide, iron oxide, cobalt oxide, and manganese oxide supported on alumina/nickel foam (NF), were used as catalysts. The reaction mechanism and dynamics analysis on toluene removal were suggested. In addition, the characterization of the catalysts was performed by BET, XRD, SEM, FT-IR, and EDS. It has been found that adding argon in the background gas could improve the toluene removal efficiency significantly in the plasma system. Combining plasma with catalyst in situ could improve the toluene removal efficiency, increase the carbon dioxide selectivity and suppress byproducts formation. In addition, manganese oxide/alumina/NF was confirmed as the most effective catalyst for toluene removal. The XRD and SEM results showed that the proportion of metal oxide increased while aluminate decreased after plasma application. The granularity of the grain on the catalyst surface became smaller and the distribution became more uniform after discharge. The results of FT-IR and EDS suggested that some organic compounds deposited on the catalysts after plasma reaction.

Analysis of sterilization effect by pulsed dielectric barrier discharge

Atmospheric pressure (AP) plasmas can sterilize against almost all kinds of bacteria because many ions and reactive species, such as oxygen atoms and ozone, etc., are generated during AP plasmas. So AP plasmas are proper processes for application to air cleaners and sterilizers. The aim of this paper is to evaluate a germicidal effect caused by pulsed plasma system in air utilizing a dielectric barrier discharge (DBD) type reactor incorporating alumina, glass, etc. Escherichia coli, Bacillus subtilis and Pseudomonas aeruginosa bacteria were used for this sterilization experiment. For analysis of the relationship between sterilization results and chemical species generated in the discharge, we used optical emission spectroscopy and we checked emission spectra by atomic oxygen (394.2 and 436.8 nm) and second positive system of nitrogen (337.1 nm). Experimental results showed that DBD treatment during 70 s sterilized E. coli with 99.99% effectively and ozone molecules were the dominant germicidal species. From these results we concluded that the pulsed DBD system is very effective for sterilization.

Treatment on Low NOx Concentration and DEP Collection with Barrier Discharge System Superposing TiO2

The automobiles exhaust carbon particles and NOx into the air, and then gases accumulate in expressway tunnels. DC corona discharge is used widely in electrostatic precipitator (ESP). However, the ESP with DC corona discharge can little remove NOx. Therefore, we proposed a new barrier discharge type precharger to replace corona discharge type prechargers to remove NOx. When discharge is generated in the air, NOx necessarily is generated. Then, we need to grasp the lower limit NOx concentration to remove NOx from the gas. We focus attention on photocatalyst because it is effective in NOx removal. However, photocatalyst needs ultraviolet ray. Therefore, TiO2 is painted on barrier discharge electrodes, an ultraviolet ray included in discharge luminescence was irradiated to TiO2. Furthermore, the relationship between initial NOx concentration and removal characteristic is investigated in detail.

Basic Parameters of Coplanar Discharge Ozone Generator

ABSTRACT Coplanar discharge is a new type of barrier discharge, and has some advantages for high-concentration ozone generation. In this article, basic parameters of coplanar discharge are clarified by experimental and theoretical approaches. Coplanar electrodes consist of many pairs of line electrodes printed on a glass plane, and are covered with dielectric layer. The discharge properties, ozone diffusion process, and surface reaction are discussed. Finally, the scaling rule of a coplanar discharge ozone generator is demonstrated by fabrication of a 3 kg/h ozone generator.

Effect of electrode shape on discharge current and performance with barrier discharge type electrostatic precipitator

In general corona discharge is used as precharger in electrostatic precipitator (ESP). The corona discharge type electrostatic precipitator can remove diesel exhaust particles (DEP) at high efficiency but at low efficiency for NO x . We propose here a barrier discharge type ESP which gives a high removal efficiency for both NO x and DEP. To study the influence of electrode shape of precharger on the collection efficiency, we carried out experiments using metallic electrodes with/without punched holes as a barrier discharge electrode. As results, discharge current was higher for the electrode with punched holes than for plane electrode. The collection efficiency obtained with punched electrode was higher than that with at plane electrode. In the next step, additionally change of metallic electrode shape, and then discharge current and performance are evaluated.

Simultaneous removal of aerosol particles, NOx and SO2, from incense smokes by a DC electrostatic precipitator with dielectric barrier discharge prechargers

In this paper, electrostatic precipitators (ESPs) under positive corona discharge operation with and without wire-rod and wire-quadrupole type barrier discharge prechargers were tested for simultaneous removal of submicron particles, NOx and SO2. High dielectric constant ferro-electric materials and hard glass were used as the barrier for barrier discharge type precharger.The results show that aerosol particles, NOx and SO2, were simultaneously removed by DC positively biased wire-plate ESPs, and that the particle collection efficiency was improved by an addition of wire-quadrupole type barrier discharge precharger in front of the wire-plate ESP. The addition of the prechargers, however, had little effect on the overall removal efficiencies of NOx and SO2.

Characteristics of Electrode Length and Mean Gas Velocity with Barrier Discharge Type ESP

Characteristics of Electrode Length and Mean Gas Velocity with Barrier Discharge Type ESP

Reduction of particles and NOx exhausted from diesel engine by barrier discharge type ESP

Reduction of particles and NOx exhausted from diesel engine by barrier discharge type ESP

Decomposition of dilute trichloroethylene by nonthermal plasma

Decomposition performance of a dilute toxic organic compound, trichloroethylene (TCE), in air by using nonthermal plasma processing was studied extensively. The nonthermal plasma was generated by the high-frequency (2 kHz) or commercial-frequency (50 Hz) barrier discharge in a fused silica tube. Three types of reactors, bolt type, rod type (both are barrier-discharge type), and coil type (surface-discharge type), were tested. Analysis of byproducts, residual materials, and end products generated by the plasma process was performed by a gas chromatography mass spectrometer or gas chromatography. Most organic byproducts decrease with an increase of the electric discharge power, but only toxic phosgene increases with the increase of the discharge power. As a post process, NaOH solution was used to test effluent from the plasma reactor. The solution was found effective in phosgene absorption. Comparison between nonthermal plasma and UV irradiation for TCE decomposition was also made. In regard to the energy efficiency of TCE decomposition, UV irradiation is found much better than discharge plasma.