Cold arc-plasma jet under atmospheric pressure for surface modification

A relatively cold arc-plasma jet under atmospheric pressure was developed using a pulse power supply, called a Plasma Energized (PEN)-Jet. A needle electrode was placed in a glass tube, and a cap electrode with a center-hole (3 mm diameter) was placed at the tube end. The electric arc was discharged between the electrodes by applying intermittent bipolar pulse power. By introducing dry air, nitrogen, or oxygen gas into the tube from the other end, the plasma gas of the arc was spewed out from the center-holed cap electrode, and a plasma jet was formed. The length and temperature of this plasma jet was measured as a function of pulse frequency (10–30 kHz). Both were found to increase with the increase in pulse frequency, not being very dependent on the type of gas under present experimental conditions. Maximum jet length was approximately 15 mm at 30 kHz, and maximum temperature at 5 mm from the cap electrode was 250 °C. Various metals and polymers were treated by PEN-Jet. The water contact-angle of these materials was found to decrease.