Characteristic Study On The Plasma Jet Generated In Capillary At Atmospheric Pressure And Its Preliminary Applications

Atmospheric pressure (AP) plasma exhibits advantages in reducing operating cost and caning out various material treatments under extreme condition compared with low pressure plasma technology. Atmospheric pressure cold plasma jet is a type of glow-like plasma generated technology in recent years, which has the main mode of RF capacitive coupling block excitation discharge and DC micro-hollow cathode discharge. However, it has the disadvantage of short jet length and low electron density. Moreover, the starting discharge is hard to achieve, so its reproducibility is poor. Thus, it will be a significant work to investigate a simple and practical technology of generating cold plasma jet.In this paper, we use the ordinary syringe needle as electrode, and the insulating tube with small inner diameter as dielectric tube. By applying a sinusoidal voltage at the frequency of 45 kHz, we materialize a super long argon plasma jet in a single-electrode configuration, and a high electron density plasma discharge generated between two needles in quartz capillary. And we also do the electric and spectral diagnosis on the two kind of plasma under different experimental parameters, such as applied voltage, power frequency, active gas concentration, etc..In the study of the single needle electrode AP plasma jet, it is observed that corona, glowlike plume, and filamentary discharges evolve individually with the increasing applied voltage. The super long argon plasma discharge propagating in the thin quartz tube is actually a filamentary discharge wriggling along the tube wall. Furthermore, the length of discharge column is in direct proportion to the operating frequency and applied voltage of power supply, which almost has the same rising tendency as discharge current. But the absorbed power density of the plasma discharge in filament mode is almost unchanged. When mensurating the oxygen atom generated in single-electrode argon/oxygen plasma jet by optical actinometry, we find that there exists an optimal value of oxygen concentration (1.4%) in the production of oxygen radicals.In the study of the plasma discharge generated between two needles in quartz capillary, it is found that there exists a discharge mode transition process from abnormal glow to arc along with the rise of applied voltage. Moreover, judging from the current-voltage characteristic curve, we find that different power frequency and needle spacing can all influence it. In addition, the gas temperature of the arc plasma is above 1000 K, which is determined by simulating the OH A-X (0,0) vibrational band around 300nm and comparing with measured spectrum by means of optical emission spectroscopy; the electron density of the arc plasma is approximately 10^-14 cm^-3, which is measured by means of Stark broadening method. However, when mensurating the oxygen atom generated in argon/oxygen arc plasma discharge by optical actinometry, we find that the amount of oxygen atoms is almost unchanged along with the rise of oxygen concentration.In addition, we also make a preliminary study on applications of the AP argon plasma discharge with a single-electrode configuration. We do not only make the nitriding experiment by using the single electrode argon/nitrogen plasma jet, but also do the hydrophilicity treatment of some material surfaces and Acidification treatment of water by using the single electrode argon/oxygen plasma jet.