| Atmospheric discharge is an important method to develop non-equilibrium plasma, whereas cold plasma jet is of a novel discharge technology at atmosphere. Moreover, atmospheric pressure cold plasma jets have the properties of low temperature, good controllability as well as simplicity of operation, which make them promising for some areas, such as surface modification, etching, sterilization and the biomedical applications. As we know, the applications of plasma are based on its characteristic study, thus it is both important and essential to obtain the parameters of plasma.According to mechanism of plasma discharge, there are such different ways as corona discharge, dielectric barrier discharge (DBD), and arc discharge, etc. Comparing with the other two mechanisms of discharge, DBD discharge is an appropriate way to generate cold plasma jets at atmospheric pressure. In this paper, based on DBD configurations, two different kinds of Ar cold plasma generators are designed. At the same time, the following work is done in this study:1. A novel high density plasma generator equiped with double power electrodes is designed, which is based on DBD configuration. The pure argon (99.999%) acts the role of woking gas, at the same time, the sinusoidal excitation voltage at 38 kHz is used to drive the power electrodes. With regards to this kind of high density plasma jet, the electron density is measured by using Stark broadening of the hydrogen Balmer Hβline (486.13 nm). Based on the experimental results, the electron density is found to be on the order of 1014 cm-3, furthermore, the value of electron density is found to increase with the peak voltage and decrease with argon gas flow rate.2. A new-type glow-like discharge device is designed, which is equiped with two power electrodes as well as a grounded ring electrode. The working gas and power source are the same with those refered in 1. Comprehensive electrical and optical diagnostics are carried out on this glow-like discharge plasma jet. For electrical diagnostics, applied voltage, root mean square value of conducting current, and average absorbed power are obtained. For optical diagnostics, electron excitation temperature as well as the gas temperature in discharge tube are estimated by using Boltzmann's plot method. In addition, the temperature of plasma effluent (plasma jet outside of the quartz tube) is observed by using fiber optic temperature sensor (FOT-L-SD). It has been found that the root mean square value of conducting current, the average average absorbed power, electron excitation temperature and the gas temperature increase with the peak to peak value of applied votage, however, these parameters decrease with argon gas flow rate. Still, the production of oxygen radical density is investigated by means of optical actinometry, which is found to increase with the peak to peak voltage. At last, the preliminary study on the surface modification of Polyethylene (PE) Film by using this cold plasma jet is carried out. The experimental results show that the static contact angle of PE Film after treament decreases obviously (decreasing from 92.55°to 35.55°), which demonstrates that the hydrophily of PE Film is enhanced greatly. |
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