| In the dielectric barrier micro-discharge system,the micro-discharge mode will affect the chemical reaction of plasma and thus affect the generation of reactive oxygen species.Based on the pin-plate DBD micro-discharge structure,this paper studies the evolution and formation mechanism of micro-discharge mode,and the influencing factors of the characteristics of micro-discharge mode,and then analyzes the influence of micro-discharge mode on the chemical reaction efficiency of oxygen plasma.The results are as follows:(1)In the pin-plate DBD micro-discharge system,sinusoidal high frequency and high voltage ac excitation voltage is applied.Many micro-stream discharges occur in the positive half period,and the negative half period is converted into a micro-glow discharge.During the transition period when the micro-discharge mode changes,a small amount of micro-negative corona discharge occurs in the early stage of micro-glow discharge.This kind of micro-streamer and micro-glow alternates to cause the phenomenon of discharge,which is mainly caused by the establishment of strong electric field in discharge space and the electrostatic field caused by the deposition of electric charge.The electrostatic field generated by the deposition of positive charge in the micro-discharge phase is conducive to the generation of micro-glow discharge.The electrostatic field formed by the electrons on the surface of the dielectric in the micro-glow discharge phase is prepared for the micro-flow discharge in the next cycle.The two discharge modes promote each other and are generated alternately.(2)The changes of excitation voltage,discharge gap and dielectric layer thickness have significant effects on the discharge intensity,discharge start time and discharge morphology of micro-discharge.The excitation voltage increases,the excitation electric field intensity increases,the electron is accelerated to obtain more energy per unit time,more easily ionized to form a discharge channel,the discharge start time is advanced,the discharge intensity increases,the number of micro-stream discharge increases,the micro-glow discharge negative area intensity increases.With the increase of discharge gap,the electric field strength and ionization degree in the discharge gap are weakened.On the macro level,the discharge is delayed in each discharge stage of micro-discharge,the discharge intensity is weakened,and the discharge quantity of micro-stream is reduced.The dielectric layer thickness is increased,the discharge intensity is weakened,the discharge start time is delayed,the number of micro-stream discharge is small,and the discharge form of incomplete glow discharge will appear in the micro-glow.(3)The alternations of micro-flow and micro-glow contribute to the existence of O particles with different spectral lines and a large number of O2+ particles in the discharge.The O in the micro-glow discharge mode is more than the other two modes,and O2+ is only generated in the micro-glow discharge mode.This is due to the discharge time of micro-glow discharge lasting tens of microseconds and the continuous strong electric field action in the cathode potential drop zone,which is the key to the generation of a large number of high-energy electrons,and is more conducive to the chemical reaction of oxygen plasma and the generation of reactive oxygen species particles.Based on the self-developed oxygen plasma reactor,when the pressure changes within the range of 60 kPa?100 kPa,the micro-glow discharge mode has a great influence on the micro-glow discharge mode,and the change of the micro-glow discharge mode is the main factor leading to the change of the performance of the oxygen plasma reactor.The pressure drops from 100 kPa to 80 kPa,and the micro-glow discharge intensity increases,resulting in the increase of the concentration of reactive oxygen particles and the reactor efficiency. |
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