Spectral Diagnosis of Plasma Jet at Atmospheric Pressure

A new approach to surface modification of materials using dielectric barrier discharge (DBD) plasma jet at atmospheric pressure is presented in the present paper. The emission spectral lines of argon plasma jet at atmospheric pressure were recorded by the grating spectrograph HR2000 and computer software. The argon plasma emission spectra, ranging from 300nm to 1000nm, were measured at different applied voltage. Compared to air plasma emission spectra under the same circumstance, it is shown that all of the spectral lines are attributed to neutral argon atoms. The spectral lines 763.51 and 772.42nm were chosen to estimate the electron excitation temperature. The purpose of the study is to research the relationship between the applied voltage and temperature to control the process of materials' surface modification promptly. The results show that electron excitation temperature is in the range of 0.1-0.5 eV and increases with increasing applied voltage. In the process of surface modification under the plasma jet, the infrared radiation thermometer was used to measure the material surface temperature under the plasma jet. The results show that the material surface temperature is in the range of 50-100 degrees C and it also increases with increasing applied voltage. Because the material surface was under the plasma jet and its temperature was decided by the plasma, and the material surface temperature increased with increasing the macro-temperature of plasma jet, the relationship between the surface temperature and applied voltage indicates the relationship between the macro-temperature of the plasma jet and the applied voltage approximately. The experimental results indicate that DBD plasma jet at atmospheric pressure is a new approach to improving the quality of materials' surface modification, and spectral diagnosis has proved to be a kind of workable method by choosing suitable applied voltage.