Plasma Chemistry and Plasma Processing (v.35, #5)

Improvement of the Water Stability of Plasma Polymerized Acrylic Acid/MBA Coatings Deposited by Atmospheric Pressure Air Plasma Jet by Olivier Carton; Dhia Ben Salem; Jérôme Pulpytel; Farzaneh Arefi-Khonsari (819-829).
A pulsed-arc atmospheric pressure air plasma jet has been used to deposit plasma polymerized acrylic acid/methylene-bis-acrylamide (ppAA/MBA) organic thin films. Optical emission spectroscopy has been performed to investigate the reactivity of the plasma and the dissociation of the precursor as a function of the pulse frequency and distance from the nozzle. An estimation of the OH rotational temperature, which is an indicator of the plasma gas temperature, has also been performed. By heating the substrate during deposition, it was possible to improve to a great extent the stability to water of the coatings. Stable ppAA/MBA films have been obtained with an air plasma over a large range of pulsed frequencies (from 15 to 25 kHz) when the substrate was heated to 200 °C. The composition of these coatings was investigated by FTIR and different amide/acid ratios were obtained, showing the possibility to grow stable films with different functional groups by adjusting the deposition parameters.
Keywords: Acrylic acid; Atmospheric pressure plasma jet; Coating stability; Plasma polymerization; Optical emission spectroscopy

Effects of nonthermal plasma (NTP) on the selective catalytic reduction of NO x by C3H8 (C3H8-SCR) over Co–In/zeolites were investigated in the presence of SO2 and H2O at low temperatures (3H8-SCR (PF-C3H8-SCR) hybrid system because of the enhancement of chemisorbed oxygen, acid sites, and weak adsorption species (NO2 and NO x ) on Co–In/H-(Beta/USY). The assistance of NTP significantly promoted the tolerance of SO2 and H2O on both Co–In/H-Beta and Co–In/H-(Beta/USY) in C3H8-SCR reaction. Co–In/H-(Beta/USY) even exhibited excellent SO2 tolerance in the PF-C3H8-SCR hybrid system when a relatively high concentration of SO2 (1000–2000 ppm) and 7 % H2O were introduced into the feed gas. Sulfate species formed on the active sites of Co–In/H-(Beta/USY) were unstable because of the relatively low-temperature (below 600 K) desorption of sulfate species. The unstable sulfate species contributed slight inhibition to C3H8 activation and nitrogen-containing formation on the active sites of Co–In/H-(Beta/USY) in the PF-C3H8-SCR hybrid system. The PF-C3H8-SCR hybrid system with Co–In/H-(Beta/USY) may be a potential candidate for DeNO x industrial applications.
Keywords: Nonthermal plasma; Co–In/zeolites; NO reduction; Propane; Low temperature

Dielectric Barrier Discharge Processing of trans-CF3CH=CHF and CF3C(O)CF(CF3)2, Their Mixtures with Air, N2, CO2 and Analysis of Their Decomposition Products by A. V. Tatarinov; I. V. Bilera; S. V. Avtaeva; V. A. Shakhatov; P. V. Solomakhin; R. Maladen; C. Prévé; D. Piccoz (845-862).
The experimental study of the degradation of gaseous dielectrics after processing in the dielectric barrier discharge (DBD) is presented. Two pure gases trans-CF3CH=CHF (HFO-1234ze(E)), perfluoroketone CF3C(O)CF(CF3)2 (C5K), and also the following mixtures 75 %HFO-1234ze(E):25 %N2, 12 %C5K:88 %N2, 18.5 %C5K:81.5 %dry air, 9 %C5K:57.5 %HFO-1234ze(E):33.5 %N2, 9 %C5K:56 %HFO-1234ze(E):35 %CO2 have been used as test-gases. A content of the decomposition products of the gases before and after a 5-h workout in the barrier discharge has been determined by means of the chromatography-mass spectrometry and gas chromatography methods. Dilution of C5K with dry air greatly increases the degree of conversion of the source gas in the barrier discharge. Dilution of HFO-1234ze(E) and C5K with nitrogen, and the use of ternary mixtures 9 %C5K:57.5 %HFO-1234ze(E):33.5 %N2 and 9 %C5K:56 %HFO-1234ze(E):35 %CO2 significantly reduces the degree of conversion of the mixture compared with the source gases in the barrier discharge. After the DBD processing of two test-gases a large quantity of toxic C3F6 was found in pure C5K, and also a large number of highly toxic CF3CCH was found in pure HFO-1234ze(E). The least amount of toxic products after the DBD processing was detected in mixtures HFO-1234ze(E):N2 and C5K:HFO-1234ze(E):N2. The mixture C5K:HFO-1234ze(E):N2 has the best features among studied mixtures.
Keywords: Hydrofluoroolefins; Perfluoroketone; SF6 ; Barrier discharge processing; Gas chromatography

This paper reports the first attempt of characterizing various physical, mechanical and chemical properties of Quiscal fibres, used by the native communities in Chile and investigating the influence of atmospheric dielectric barrier discharge plasma treatment on various properties such as diameter and linear density, fat, wax and impurity%, moisture regain, chemical elements and groups, thermal degradation, surface morphology, etc. According to the experimental observations, Quiscal fibre has lower tenacity than most of the technical grade natural fibres such as sisal, hemp, flax, etc., and plasma treatment at optimum dose improved its tenacity to the level of sisal fibres. Plasma treatment also reduced the amount of fat, wax and other foreign impurities present in Quiscal fibres as well as removed lignin and hemicellulose partially from the fibre structure. Plasma treatment led to functionalization of Quiscal fibre surface with chemical groups, as revealed from attenuated total reflection spectroscopy and also confirmed from the elemental analysis using energy dispersive X-ray technique and pH and conductivity measurements of fibre aqueous extract. The wetting behavior of Quiscal fibre also improved considerably through plasma treatment. However, untreated and plasma treated Quiscal fibres showed similar thermal degradation behavior, except the final degradation stage, in which plasma treated fibres showed higher stability and incomplete degradation unlike the untreated fibres. The experimental results suggested that the plasma treated Quiscal fibres, like other technical grade natural fibres, can find potential application as reinforcement of composite materials for various industrial applications.
Keywords: Quiscal fibre; Mechanical properties; Plasma treatment; Thermal degradation; Surface morphology

Experimental Study on the Characteristics of a Miniature Laminar Plasma Torch with Different Gas Flow Patterns by Jianguo Miao; Deping Yu; Xiuquan Cao; Yong Xiang; Meng Xiao; Jin Yao (879-893).
As laminar plasma jet has long stable plasma jet, low temperature gradient, negligible noise emission, good processing reproducibility and controllability, it is suitable for industrial applications with high precision requirement. However, the conventional laminar plasma torches are large in size and thus can hardly be applied in processing occasions with space limitation. In this paper, a miniature DC non-transferred arc laminar plasma torch with an external size of about 57 × 56 × 42 mm is proposed to meet the processing requirements in these occasions. It can generate long laminar plasma jet with a maximum jet length of about 300 mm at atmospheric pressure with pure nitrogen. Experimental study on the proposed plasma torch has been carried out to obtain its arc voltage characteristics and the jet length characteristics. It has been founded that the plasma torch with spiral gas flow pattern generally has higher arc voltage and longer jet length than that with axial gas flow pattern. In addition, a special jumping arc voltage characteristic and the variation appearances of the plasma jet were founded, which may be used to design miniature laminar plasma torch with high arc voltage and thus low arc current for the same output power as the conventional ones.
Keywords: Miniature laminar plasma torch; Laminar plasma jet; Gas flow pattern

The effect of non-thermal plasma generated by electron-beam on the behavior of polycyclic aromatic hydrocarbons (PAHs) in industrial flue gases was investigated using methods of mathematical modeling. The proposed kinetic model of the process includes mechanism of PAHs conversion caused by their interaction with OH-radicals, ion-molecular mechanism of PAHs decomposition, and ion-molecular mechanism of higher-ringed PAHs formation. The model allows to predict the main features of the process, which are observed in pilot plant installations, and to give quantitative estimations of the process efficiency. The results of calculations are compared with the available experimental data.
Keywords: Non-thermal plasma; Electron-beam irradiation; PAHs transformation; Rate constants; Flue gases

Characterization of Boron-Doped ZnO Nanorods Fabricated Using Diborane Plasma by Xiuqin Wang; Jianhua Qiu; Ying Wang; Ningyi Yuan; Jianning Ding (913-923).
ZnO nanowire or nanorod arrays have caused great interest owing to their unique properties and versatile applications in short-wavelength lasers, electroluminescent devices, photocatalytic systems, and solar cells, etc. The electrical and optical properties of ZnO nanorod arrays can be altered and controlled through doping. In this paper, B2H6 plasma treatment was employed to improve the electrical properties of ZnO nanorod arrays prepared by hydrothermal synthesis. A clear decrease in the resistivity of ZnO nanorod arrays with B2H6 plasma treatment was observed. Moreover, the measurement results of XPS and Hall measurement show that the B2H6 plasma treatment can be used to achieve n-type doping via B atoms substitution for Zn atoms.
Keywords: ZnO nanorod; Doping; Plasma; Electrical properties