Comparative study on diffuse dielectric barrier discharges excited by unipolar positive versus bipolar pulses in atmospheric air

Abstract

Diffuse discharges excited by unipolar positive and bipolar pulses can be achieved by a self-designed dielectric barrier discharge (DBD) structure (a metal rod is inserted into a traditional parallel-plate DBD structure) exposed in airflow. For a self-designed DBD excited by unipolar positive pulses, only a primary discharge occurs in a voltage pulse. When the applied voltage is low, a diffuse discharge first appears near the anode. As the voltage further increases, a diffuse discharge appears in a larger area near the anode. Until the applied voltage is high enough, the discharge fills the whole discharge gap. Additionally, there is a priority region around the metal rod for the development of a diffuse discharge. However, for a self-designed DBD excited by bipolar pulses, two separate discharges are observed in a voltage pulse. The primary discharge occurs at the rising front of the voltage pulse, and the secondary discharge (reverse discharge) takes place at the falling front of the voltage pulse. When the applied voltage is low, the diffuse discharge first starts from the priority region around the metal rod placed in the center of the discharge electrode. As the voltage further increases, the diffuse discharge appears in a larger area around the metal rod. The above observations about the different spatial evolutions of diffuse discharge areas excited by unipolar positive and bipolar pulses are mainly ascribed to the difference of a strong local electric field caused by residual charges. This diffuse discharge has potential applications in surface treatment of materials and thin film deposition.