To deposit TiO2 films through plasma CVD, the partial pressure ratio of O2 to TiCl4 should be greater than the stoichiometric ratio (pO2 /pTiCl4>1). However, this may lead to the formation of powder instead of film on the substrate when using volume dielectric barrier discharge (volume-DBD) at atmospheric pressure. In this study, by adding N2 into the working gas Ar, TiO2 photocatalytic films were successfully fabricated in the presence of excess O2 (pO2 /pTiCl4=2.6) by using a wire-to-plate atmospheric-pressure volume-DBD. The tuning effect of N2 on the deposition of TiO2 film was studied in detail. The results showed that by increasing the N2 content, the deposition rate and particle size of the TiO2 film were reduced, and its photocatalytic activity was enhanced. The tuning mechanism of N2 is further discussed.
A one-dimensional self-consistent fluid model was developed for radio frequency glow discharge in helium at near atmospheric pressure, and was employed to study the gas breakdown characteristics in terms of breakdown voltage. The effective secondary electron emission coefficient and the effective electric field for ions were demonstrated to be important for determining the breakdown voltage of radio frequency glow discharge at near atmospheric pressure. The constant of A was estimated to be 64±4 cm 1 Torr 1 , which was proportional to the first Townsend coefficient and could be employed to evaluate the gas breakdown voltage. The reduction in the breakdown voltage of radio frequency glow discharge with excitation frequency was studied and attributed to the electron trapping effect in the discharge gap.
Two plasma reactors have been developed and used to degrade dye wastewater agents.The configuration of one plasma reactor is a comb-like extendable unit module consisting of 5 electrodes covered with a quartz tube and the other one is an array reactor which is extended from the unit module.The decomposition of wastewater by ns pulse dielectric barrier discharge(DBD) plasma have been carried out by atomizing the dyeing solutions into the reactors.During experiments,the indigo carmine has been treated as the waste agent.The measurements of UV-VIS absorption spectroscopy and the chemical oxygen demand(COD) are carried out to demonstrate the decomposition efect on the wastewater.It shows that the decoloration rate of 99% and the COD degradation rate of 65% are achieved with 15 min treatment in the unit reactor.The efect of electrical parameters on degradation has been studied in detail.Results from the array reactor indicate that it has a better degradation efect than the unit one.It can not only totally remove the chromogenic bond of the indigo carmine solution,but also efectively degrade unsaturated bonds.The decoloration rate reaches 99% after 10 min treatment,the decomposition rate of the unsaturated bond reaches 83% after 60 min treatment,and the COD degradation rate is nearly 74%.
An atmospheric non-thermal plasma jet was developed for sterilizing the Staphylococcus aureus (S. aureus). The plasma jet was generated by dielectric barrier discharge (DBD), which was characterized by electrical and optical diagnostics. The survival curves of the bacteria showed that the plasma jet could effectively inactivate 10 6 cells of S. aureus within 120 seconds and the sterilizing efficiency depended critically on the discharge parameter of the applied voltage. It was further confirmed by scanning electron microscopy (SEM) that the cell morphology was seriously damaged by the plasma treatment. The plasma sterilization mechanism of S. aureus was attributed to the active species of OH, N 2 + and O, which were generated abundantly in the plasma jet and characterized by OES. Our findings suggest a convenient and low-cost way for sterilization and inactivation of bacteria.
