An Empirical Study of Electrode Degradation in Gliding Arc Discharge

Abstract

Non-thermal plasma can be generated by gliding arc discharge units and is used in various applications including disinfection of the surface, inactivation of fungi, viruses, and bacteria. Degradation of the electrodes through prolonged use is common. It is caused by bombardment by plasma-charged particles causing changes to the structure and chemistry of its electrodes which in turn leads to a reduction in the efficiency of the plasma. In this study, the discharged plasma from a gliding arc unit was investigated using optical emission spectrometry (OES). Also studied were the electrodes of the unit after prolonged use. The structure and metallographic properties of the electrodes were evaluated using positron annihilation lifetime spectroscopy (PALS), X-ray diffraction analysis (XRD) and scanning electron microscopy—energy dispersive X-ray spectroscopy (SEM-EDX) and compared to data from new unused samples. The size of defects and holes were also compared using PALS. It was found that the intensity of species decreased significantly with prolonged use of the unit as the copper electrodes degraded. It was also found that the internal structure, as well as the surface of the used electrodes, had changed significantly compared to the unused samples, the radius of holes in the electrode material had decreased and the intensity of holes increased. Furthermore, the planes of the atomic structure of the copper electrode have moved closer. The approach developed in this study has been shown an effective non-destructive method for routine evaluation of the electrodes and maybe a development further for monitoring and quality assurance programs for maintaining high plasma efficiency as well as for research into improvements to electrode material design.