Experimental Studies On Atmospheric Pressure PET Barrier Discharge Mode

The kilohertz atmospheric pressure dielectric barrier discharge does not require an expensive vacuum system and can generate active species at low temperatures.It has many important applications in the fields of material surface modification,industrial ozone generation,and CO laser excitation,etc.The generation of active species is closely related to the discharge mode.The reported discharge mode research mainly focused on the discharge of inert gas and their mixed gas under the aluminum oxide medium,but there are few studies on the discharge mode of helium / argon mixed gas under PET medium.In this thesis,the following works on the discharge mode of helium / argon mixed gas in PET medium are done:firstly,the influences of electrode voltage on the discharge characteristics in pure helium,pure argon and 1: 1 helium / argon mixed gas in PET medium were studied,the results show that(1)the glow discharge at atmospheric pressure can be obtained in both the pure helium and the pure argon discharge in PET dielectric barrier.The difference between the helium and the argon discharge is that the helium discharge is uniform at different electrode voltages.While the argon discharge shows an isolated,locally uniform glow(pattern)discharge characteristic at low electrode voltage,and evolves from an isolated,locally uniform pattern discharge to a continuous,uniform glow discharge with increasing the electrode voltage;(2)with the increase of electrode voltage,the discharge mode of helium /argon mixed gas undergoes the transition from uniform glow,glow-pattern coexistence,pattern,glow-pattern coexistence and uniform glow.The corresponding electrode voltage is1.46,1.64,1.82 and 1.92 k V,respectively.Finally,the influence of the proportion of argon gas in the helium / argon mixed gas on the discharge mode is studied,and the areas of existence for the discharge mode in an electrode voltage vs.argon / helium gas flow ratio diagram are obtained.It is found that with increasing the electrode voltage,in the 0.3?Ar/(Ar+He)region,the discharge can continuously operate from the uniform glow to the glow-pattern coexistence;In the 0.3?Ar/(Ar+He)?0.9 area,there are five characteristic areas(two uniform glow areas,two glow-pattern coexistence areas and pattern area);in the Ar/(Ar+He)?0.9 area,the discharge operates in the pattern area,the glow-spot pattern coexistence area and the uniform glow area.Simultaneously,the variations of argon atomic line intensity and electron excitation temperature with electrode voltage under different argon / helium gas flow ratiowere also studied.A physical explanation on the effect of electrode voltage and the proportion of argon in the helium / argon mixed gas on the discharge mode is given.