Propagation dynamics of a room-temperature pulsed argon plasma plume through a simple dispersion-grating diagnostic method

In this paper, a novel grating-ICCD camera dispersion diagnostic method was designed to investigate the propagation behaviors of an open-air pulsed argon plasma plume. Based on the dispersion feature of gratings, the irradiative plasma plume was dispersed into several emission-volumes corresponding to different wavelengths. And a series of high-speed dispersed emission-image sequences were captured by the ICCD camera. From these sub-microsecond emission-images at different wavelengths, the temporal and spatial propagation behaviors of excited species in the plasma plume were observed clearly

Positive- and negative-pulsed argon plasma plumes in the open air

Cold atmospheric pressure plasma plumes have obtained great interests for their attractive features and application potentials. In this work, cold argon plasma plumes were generated in the open air by a single medical-needle excited by a high-power pulsed excitation source. Characteristic comparision was carried out in the plasmas under different polarties of applied voltages. The results showed that the positive pulsed plasma plume performed a larger discharge current and stronger optical emission than the negative case. Gas temperature of the plasmas were obtained by the Boltzmann plot method and fitting the syntheric-to-experimental spectrum of the OH (A-X) transition emission bands. It is found that both the positive and negative pulsed plasma plumes are under a relative low gas temperature about 400 K. Through the high-speed imaging, an interesting propagation process was observed for the positive pulsed plasma plume, during which the plasma first propagates in the form of plasma ‘bullets’, and then transits into typical stream propagation as soon as the ‘bullets’ disappears in the open air, which is much different with the negative case

Hydrogen peroxide generation by DC and pulsed underwater discharge in air bubbles

The generation of H(2)O(2) in underwater discharge in air bubbles is studied with consideration of the influence of electrodes polarity, input power, solution conductivity and the inter-electrode distance. The efficiency of hydrogen peroxide generation strongly depends on the polarity, input power and the inter-electrode distance. Discharges in air bubbles with water as a cathode have significantly higher energy yield of hydrogen peroxide in comparison with negative DC or pulsed discharges. The generation of hydrogen peroxide by DC discharge increases with decrease in the inter-electrode distance, but it is opposite for pulsed discharges. Different efficiency of H(2)O(2) production is explained based on physical processes which result to formation of OH radicals

Plasma modification of poly lactic acid solutions to generate high quality electrospun PLA nanofibers

Physical properties of pre-electrospinning polymer solutions play a key role in electrospinning as they strongly determine the morphology of the obtained electrospun nanofibers. In this work, an atmospheric-pressure argon plasma directly submerged in the liquid-phase was used to modify the physical properties of poly lactic acid (PLA) spinning solutions in an effort to improve their electrospinnability. The electrical characteristics of the plasma were investigated by two methods; V-I waveforms and Q-V Lissajous plots while the optical emission characteristics of the plasma were also determined using optical emission spectroscopy (OES). To perform a complete physical characterization of the plasma-modified polymer solutions, measurements of viscosity, surface tension, and electrical conductivity were performed for various PLA concentrations, plasma exposure times, gas flow rates, and applied voltages. Moreover, a fast intensified charge-couple device (ICCD) camera was used to image the bubble dynamics during the plasma treatments. In addition, morphological changes of PLA nanofibers generated from plasma-treated PLA solutions were observed by scanning electron microscopy (SEM). The performed plasma treatments were found to induce significant changes to the main physical properties of the PLA solutions, leading to an enhancement of electrospinnability and an improvement of PLA nanofiber formation

A branching streamer propagation argon plasma plume

Cold atmospheric-pressure plasma plumes have obtained great interests for their attractive features and application potentials. In this paper, a pulsed argon plasma plume was generated in the open air. Characteristic propagation of the argon plasma plume was carried out through high-speed imaging by an ICCD camera. An interesting propagation process was observed for the plasma plume, during which the plasma first propagated in a single streamer channel, and then with side branching as the applied voltage increased. The side branches are generated surrounding the main plasma channel but not split from the anode tip. This branching streamer propagation behavior was much different from the bulletlike development of typical plasma jets or streamers in point-wire or point-plane gaps

Atmospheric pressure glow discharge for CO2 conversion : model-based exploration of the optimum reactor configuration

We investigate the performance of an atmospheric pressure glow discharge (APGD) reactor for CO2 conversion in three different configurations, through experiments and simulations. The first (basic) configuration utilizes the well-known pin-to-plate design, which offers a limited conversion. The second configuration improves the reactor performance by employing a vortex-flow generator. The third, "confined" configuration is a complete redesign of the reactor, which encloses the discharge in a limited volume, significantly surpassing the conversion rate of the other two designs. The plasma properties are investigated using an advanced plasma model

Under water discharge in bubbles in very low conductive solutions

This contribution presents experimental results obtained with underwater electric discharge created in rising gas bubbles. This discharge configuration is relatively new, and combines both gas and liquid phase discharges. The properties and mechanism of bubble discharge generation were investigated using a single pulsed high voltage. The electric discharge was generated in a pin-to-plate electrode configuration submerged in deionized water with conductivity of 2.0–5.0 μS/m. The gas bubbles were formed by injecting the gas through a glass filter disc at the bottom of the water tank. Air and helium were used as inlet gas. A spark gap pulse generator triggered the single negative high voltage pulses with rise times below 10 ns and peak voltages of 15–20 kV. The bubble position at the moment of high voltage application was accidental. The measured spectra were qualitatively reproducible, but significant quantitative differences were observed. We observed two types of discharge inside the bubble: delayed and direct spark discharge. The emission spectra of these two discharge kinds were qualitatively very similar