Invesitgation On Spectral Characteristics Of CF₄ High-Voltage Nanosecond Pulse Discharge In Atmosphere

The non-equilibrium plasma generated by gas discharge is widely used in fields such as biomedicine and industrial production,such as sterilization,wound healing,film deposition,surface etching,material modification,auxiliary combustion and so on.Non-equilibrium plasma can be obtained by using nanosecond pulse discharge in an open environment at normal pressure.The structure of device is simple and nanosecond pulse discharge has been widely used.CF₄ is an industrial gas and a strong greenhouse gas,therefore there are many problems such as gas ratio and waste gas treatment in its plasma application.In this paper,a coaxial tubular dielectric barrier needle ring electrode was selected to discharge the Ar/CF₄ mixed gas with nanosecond pulses,and the characteristics of plasma generated by different discharge conditions at atmospheric pressure were studied to provide some basic theory and experiment for surface modification of CF₄ plasma and waste gas treatment of CF₄.The detailed contents of this research are as follows:Firstly,the high-voltage pulse source was re-integrated,and the reset circuit of the pulse power supply was designed with emphasis,thus the rising edge of the power supply was compressed to about 100 ns.According to the acquisition time of the spectrum and the generation time of the pulse current,the trigger control sequence of the spectrometer was designed to realize the real-time collection of single pulse discharge spectrum.Secondly,in order to investigate the influence of the voltage,pin-ring spacing and gas composition ratio on the characteristics of the Ar/CF₄ discharge plasma under atmospheric pressure,the discharge luminescence images were taken,the ignition voltage and pulse current were obtained,and the emission spectrum of the gas discharge was collected simultaneously.It was found that there were significant differences in discharge images of different gases.The ignition voltage of the Ar/CF₄ mixed gas increased with the increase of the volume fraction of CF₄,and the spectral line intensities of Ar and F atoms both increased with the increase of the pulse voltage.The CF₃ groups and F atoms in the spectrum of Ar/CF₄ indicated that the strong greenhouse gas CF₄ could be decomposed by nanosecond pulse power discharge under atmospheric pressure.Thirdly,the Boltzmann slope method was used to calculate the electron excitation temperature of the discharge plasma,and the stark broadening of non-hydrogen-like atoms was used to calculate the electron density.When the volume fraction of CF₄ was 4%and the pin-ring spacing was 5 mm,the electron temperature(1.5 eV)of the Ar/CF₄ plasma was at the maximum,and the electron density was 1.54×10¹⁴ cm^-3corresponding.In addition,the contact angle results showed that Ar/CF₄plasma could significantly improve the surface hydrophilicity of the polyimide film.