Study of Characteristics of Excited O Atom Generated in Multi-Needle-to-Plate Corona Discharge by Emission Spectroscopy
ABSTRACT The emission spectra of O(3p 5 P --> 3s 5 S2(0) 777.4 nm) produced by multi-needle-to-plate negative corona discharge and positive streamer discharge in air were successfully recorded at one atmosphere. The influences of discharge power, electrode gap, content of N2 and relative humidity on the excited O atom production were investigated in negative corona discharge. Meanwhile, the distribution of relative density of excited O atom in discharge space was also studied in positive streamer discharge. The results indicate that, for negative corona discharge, the amount of O active atom increases with the increase in power, decreases with increased discharge gap. And with the increase in relative humidity and N2 content, its amount firstly increases and then decreases; whereas for positive corona discharge, the relative density of O active atom from needlepoint to plate firstly increases and then decreases.
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ABSTRACT: Ozone is an undesirable byproduct of non-thermal plasma (NTP) for volatile organic compounds (VOCs) control. Photocatalysis combined downstream the NTP reactor and ozone was utilized to oxidize toluene. The multiple synergies of O(3)/UV/TiO(2) system and the mechanism of toluene decomposition were investigated. The influence factors such as energy density, humidity and UV sources were also intensively studied. The combination of photocatalysis in the post-plasma increased the conversion of toluene and ozone to almost 80 and 90%, respectively. Water vapor played a dual role in toluene destruction and ozone removal. In total, 0.75% humidity had the best conversion of toluene and ozone at these experimental conditions. The conversion of toluene enhanced with increasing ozone removal. Among the multiple oxidation processes in the O(3)/UV/TiO(2) system, the O(3)/TiO(2) process played a key role in the decomposition of toluene.Journal of hazardous materials 07/2009; 171(1-3):535-41. DOI:10.1016/j.jhazmat.2009.06.033 · 4.33 Impact Factor
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ABSTRACT: An atmospheric-pressure plasma jet has been used to etch polyimide films at 1.0[endash]8.0[plus minus]0.2 hthinsp;[mu]m/min at 760 Torr and between 50 and 250 hthinsp;[degree]C. The plasma was produced by flowing helium and oxygen between two concentric electrodes, with the inner one coupled to 13.56 MHz rf power and the outer one grounded. The etch rate increased with the O[sub 2] partial pressure, the rf power and the substrate temperature. The apparent activation energy for etching was 0.16 eV. Langmuir-probe measurements revealed that the ion densities were between 1[times]10[sup 10] and 1[times]10[sup 11] hthinsp;cm[sup [minus]3], 5 mm from the end of the powered electrode. Biasing the substrate had no effect on the rate. Ozone, singlet sigma metastable oxygen (b hthinsp;[sup 1][Sigma][sub g][sup +]), and singlet delta metastable oxygen (a hthinsp;[sup 1][Delta][sub g]) were detected in the plasma by emission spectroscopy. More ozone was produced in the effluent through the recombination of O atoms with O[sub 2]. Based on the production rate of O[sub 3], the concentration of O atoms 6 mm from the powered electrode was estimated to be [approximately]7[times]10[sup 14] hthinsp;cm[sup [minus]3] at 6.6 Torr O[sub 2] and 200 W power. It is proposed that O atoms are the principal reactive species involved in etching polyimide. [copyright] [ital 1999 American Vacuum Society.]Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 09/1999; 17(5):2581-2585. DOI:10.1116/1.581999 · 2.14 Impact Factor
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ABSTRACT: Atmospheric pressure air plasmas are often thought to be in local thermodynamic equilibrium owing to fast interspecies collisional exchange at high pressure. This assumption cannot be relied upon, particularly with respect to optical diagnostics. Velocity gradients in flowing plasmas and/or elevated electron temperatures created by electrical discharges can result in large departures from chemical and thermal equilibrium. This paper reviews diagnostic techniques based on optical emission spectroscopy and cavity ring-down spectroscopy that we have found useful for making temperature and concentration measurements in atmospheric pressure plasmas under conditions ranging from thermal and chemical equilibrium to thermochemical nonequilibrium.Plasma Sources Science and Technology 05/2003; 12:125-138. DOI:10.1088/0963-0252/12/2/301 · 3.06 Impact Factor