Electrode Configuration Designs And Characteristics Of Needle-Ring Dielectric Barrier Discharge Plasma Jet Device At Atmospheric Pressure

Compared with traditional atmospheric-pressure nonthermal plasma devices, the atmospheric-pressure cold plasma jet devices have some advantages:(1) the plasma jet is formed in open air rather than confined discharge gap;(2) either direct or indirect treatment, most of the short lifetime active species can be reached the treated object before disappearing;(3) there is no limitation on the size and shape of the object to be treated;(4) the three-dimensional treatment can be processed by moving the plasma jet device for the object to be treated. In addition, the desirable properties of atmospheric-pressure nonthermal plasma are inherited by the cold plasma jet, which have a large number of chemical active species such as O, OH, etc. And the gas temperature is only several hundred K and in extreme cases, the gas temperature is close to room temperature. Therefore, the atmospheric-pressure cold plasma jets received much attention from a large number of industrial applications, such as biomedical applications, material surface modification, thin film deposition, and etching, etc, which have became the international research hot spot.The design and improvement of cold plasma jet devices, the characteristic diagnosis of plasma jet, and the improvement of diagnosis method, etc, are very important for plasma sciences and engineering researches. For this reason, the following works are done in this paper:1. An atmospheric-pressure Ar cold plasma jet is generated with screw ring-ring electrodes in surface dielectric barrier discharge. By the electrical and optical diagnostics, it is found that the effective power and gas temperature is relatively low, and the effective power, rotational and vibrational temperature of N2, electronic excitation temperature, oxygen atomic density, nitrogen molecular density and average electron density are increased with peak applied voltage, among which the oxygen atomic density, nitrogen molecular density and average electron density are in the orders of magnitude of1016cm-3,1016cm-3, and1012cm-3.2. An atmospheric-pressure Ar cold plasma jet is developed with tube-ring electrodes in surface dielectric barrier discharge. The plasma jet device is designed to improve the screw ring-ring electrodes plasma jet device by enhancing the axial electric filed. By the electrical and optical diagnostics, it is found that the plasma jet device has a low effective power, a high electric field in discharge space, and a high electron temperature. The vibrational temperature of N2, electronic excitation temperature, oxygen atomic density, and average electron density are obviously higher than that of screw ring-ring electrodes plasma jet, among which the oxygen atomic density is34%higher than that of the screw ring-ring electrodes plasma jet.3. An atmospheric-pressure Ar cold plasma jet is generated with rod-tube-ring electrodes in dielectric barrier hybrid discharge. The plasma jet device is obtained by inserting the rod high voltage electrode to the tube high voltage electrode in the tube-ring electrodes plasma jet device. By the electrical and optical diagnostics, it is found that the conduction current peak value, effective power, vibrational temperature of N2, electronic excitation temperature, spectral intensity, oxygen atomic density, nitrogen molecular density and average electron density is obviously higher than that of the tube-ring electrodes plasma jet device, among which the oxygen atomic density is21%higher than that of the tube-ring electrodes plasma jet.4. To improve the disadvantages that plasma is ignited in the inside of dielectric for the aforementioned three kinds of dielectric barrier discharge plasma jet device, an atmospheric-pressure Ar cold plasma jet is generated with syringe needle-ring electrodes in dielectric barrier discharge. By the electrical and optical diagnostics, it is found that the plasma can be ignited in the outside of dielectric at low applied voltage for the syringe needle-ring electrodes plasma jet device. The plasma jet has a high electric fied in the syringe needle tip, a relatively low gas temperature, and the oxygen atomic density is in the order of magnitude of1016cm-3.5. Based on the syringe needle-ring electrodes Ar plasma jet device, an atmospheric-pressure Ar/O2cold plasma jet is generated with syringe needle-ring electrodes in dielectric barrier discharge. By the electrical and optical diagnostics, it is found that the plasma jet device can stably discharge in the Ar/O2mixed gas of oxygen content as high as12.5%and the generated plasma jet has a high electric fied in the syringe needle tip, and the gas temperature is closer to room temperature. Further more, the plasma jet has a high electron temperature, high average electron energy, and high oxygen atomic density. Besides, the methylene blue solutions are treated by the plasma jet, finding that the removal efficiency is higher than90%.6. Using the syringe needle-ring electrodes plasma jet device, an atmospheric-pressure air cold plasma jet is generated with syringe needle-ring electrodes in dielectric barrier discharge. By the electrical and optical diagnostics, it is found that the air plasma jet can be generated with or without air flow and the air plasma jet has a high electric fied in the syringe needle tip, and the gas temperature is closer to room temperature. Further more, the plasma jet has a high electron temperature and energy, a long plasma jet length, and a large number of active species.