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A nonequilibrium plasma flow produced uniformly in a tube was developed in this paper. The plasma was generated in polyvinyl chloride tube, 3 mm in inner diameter and 100 mm in length, between a wire electrode, 0.2 mm in diameter, and a grounded flat electrode located at the bottom of the tube. We investigated the spectrum, temperature, and ozone concentration of this plasma flow and its sterilization efficacy against Geobacillus stearothermophilus. The temperature in the tube showed uniformity along the wire electrode and increases as applied voltage was increased. With a wire electrode temperature of 337 K at a peak-to-peak applied voltage of 10 kVpp in the sine wave and a frequency of 6 kHz, sterilization of 105 cells was obtained. This result suggests the potential of the application of plasma flow rather than ethylene oxide for sterilization of the inner wall of tubes, such as catheters and artificial blood vessels. [ABSTRACT FROM AUTHOR]

Indoor air quality was improved by controlling particulate matter (PM) consisting of components such as house dust and bacteria, using an atmospheric pressure plasma. Two types of electrode, which generate corona discharges, were placed inside a reactor and energized to generate a nonthermal plasma, i.e., a disc-type reactor and a needle-type reactor. A plasma can decompose harmful substances by various active species such as reactive radicals (e.g., N^\ast,\;O^\ast,\;\and\;OH^\ast) and ions, and a strong electric field. The particle collection rate depended on the discharge voltage, number of mesh filters, flow rate, and reactor characteristics. The dust-collecting rate in the case of the disc-type reactor was 95% and in the case of the needle-type reactor was 98%. Formaldehyde removal was also performed to confirm the improved performance of the nonthermal plasma and reduction of formaldehyde to below the permitted value of 0.08 ppm. [ABSTRACT FROM AUTHOR]

Atmospheric pressure plasma graft polymerization-treated fluorocarbon plastics are bonded with a metal, to evaluate adhesiveness. In this research, the atmospheric nonthermal plasma graft polymerization technique is used in treating the surface of polytetrafluoroethylene (PTFE) in a dry process, capable of reducing environmental loading. The treated PTFE is joined with the stainless steel plate to perform a peeling test. We examine the peeling strength and the best condition for practical application using peeling strength as an optimization variable. A concrete numerical target is 2 N/mm, which is the standard adhesive strength applicable for industry uses. To conduct the graft polymerization, we use a monomer such as acrylic acid (CH2 = CHCOOH) and target material such as PTFE. Peeling strength is maximized (averaged value of 1.56 N/mm, largest value of 2.0 N/mm) when the temperature of the acrylic acid is 60 °C and the Ar main flow rate is 40 L/min. Influence of plasma torch cover on peeling strength and entrained flow near the torch are investigated to realize the stronger adhesion, and better shape of the cover is determined. Furthermore, by analyzing X-ray photoelectron spectroscopy and scanning electron microscope images, we evaluate the atmospheric pressure plasma graft polymerization process from a different perspective and search for optimal operating conditions of the processing method. [ABSTRACT FROM AUTHOR]

Microplasma has the advantage of reducing the discharge voltage compared with other atmospheric plasmas. It is generated at atmospheric pressure at only around 1.0 kV since its discharge gap is on the order of micrometers. The experiment was performed with air and argon as the process gases, to confirm the influence of different radical species in the microplasma, on the bacteria cultures. The process gas flows through the parallel plate electrodes with holes which were covered with dielectric material and energized at about 1.0 kV. The active species generated by the dielectric-barrier discharge microplasma flows toward the exposed Escherichia coli on the agar media at a distance of 2 mm from the electrodes. The process is known as remote microplasma sterilization method. Microplasma generated by both air and Ar is effective for sterilization. Observation by the scanning-electron-microscope images shows that the E. coli had a shrunk shape after the microplasma treatment. [ABSTRACT FROM AUTHOR]

In the study reported herein, chemical reactive flow fields of nonthermal plasma were clarified by using both experimental and numerical methods. The plasma was generated by using needle-plate electrodes. The operating gas was air injected at a rate of 1-10 NL/min through a cylindrical reactor with a diameter of 6 mm. Applied voltage of 12 kV was positive or negative with a square wave of 20 Hz. Distributions of gas velocity, gas temperature, and NO and NO2 concentrations were analyzed by experimental and numerical methods. Conservation equations of mass, chemical species, momentum and energy, and 22 chemical species and 89 chemical reactions are taken into consideration in the model herein proposed. Distributions of axial velocity and gas temperature, their concentrations of NO and NO2, and the effects of gas flow rate were clarified. For these characteristics of the parameter, the same tendency was obtained by both experimental and numerical methods. Furthermore, distributions of radical species such as N and O were predicted by numerical analysis using experimental results. [ABSTRACT FROM AUTHOR]