Wettability Modification and Cleaning Performance of Net Electrode Surface Dielectric Barrier Discharge Plasma

A net electrode surface dielectric barrier discharge plasma device and a plasma cleaning platform based on the electrode were designed and built to solve the problems of poor uniformity, high temperature, and small plasma area in existing atmospheric plasma cleaning device. The device structure parameters were optimized by electrostatic field simulation and experiments. The final mesh diagonal size was determined to be 6 mm, and mica flakes with a thickness of 0.3 mm were used as the dielectric material. By measuring the discharge waveform, the discharge characteristic of the device was studied. A cleaning platform based on the discharge device was built to carry out the cleaning experiment on the glass and aluminum surface coated with lubricating oil. The mechanism of plasma cleaning was studied by measuring the surface morphology and elemental components before and after cleaning through AFM, SEM and EDS. The electrostatic field and discharge power of the discharge device were positively correlated to the mesh size, the relative permittivity of the dielectric barrier and the discharge voltage, and were inversely correlated to the thickness of the barrier. With increasing frequency, the discharge power firstly increased and then decreased. The contact angle of the sample surface decreased significantly with the increase of voltage, and decreased firstly and then increased with the increase of discharge frequency, and reached a maximum discharge power of 79 W at 5.29 kHz. The optimal cleaning parameters for the glass derived from the experiments were: voltage peak-to-peak value of 11.52 kV, discharge frequency of 5.29 kHz, treatment distance of 0.3 mm, treatment duration of 20 min, and sample movement speed of 2 mm/s. After plasma cleaning, tiny dirt was removed from the glass surface, the maximum height difference on the surface decreased from 0.15 μm to 71 nm, and the carbon content decreased from 4.46% to 1.49%. At the same time, the oxygen content was slightly increased, the tiny dirt on the surface of the aluminium sheet was removed and the maximum height difference of the sample remained basically unchanged, while the carbon content on the surface of the aluminium sheet was reduced and the oxygen content was increased at the same time. This indicated that part of the active oxygen generated by the plasma combined with carbon to form small molecules that were easy to remove, and the other part generated hydrophilic groups to improve the adhesion of the sample surface. No obvious damage was observed on the sample surface after plasma treatment. The optimal cleaning parameters for the aluminium sheet were discharge voltage peak-to-peak of 11.60 kV, discharge frequency of 5.29 kHz, treatment distance of 0.3 mm, treatment duration of 30 min, and sample movement speed of 2 mm/s. The experiment shows that the cleaning platform can effectively clean the lubricating oil on the surface without causing damage and significantly improve its wettability. Plasma cleaning is dominated by chemical reactions and can clean organic contaminants from surface without damaging the surface. © 2023 Chongqing Wujiu Periodicals Press. All rights reserved.