Multipoint-to-multipoint and multipoint-to-plane electrode geometries have been investigated to enhance corona discharge modes in atmospheric pressure weakly ionized plasma. This paper presents a new geometry approach by a protrusion array over the grounded screen along with a high-voltage (HV) needle array to obtain higher coulombic discharge. It has been observed that needle-to-grounded-screen-protrusion configuration enhances the discharge modes, especially the back corona is enhanced significantly near the protrusions in Ar/C 2 H 2 plasma. A corona mode map has been developed to depict the optimal discharge zones at various HV gaps. Similar investigations were performed in Ar/O 2 plasma to study the nature of the current pulses and discharge modes.Index Terms-Atmospheric pressure plasmas, back corona, point-to-plane corona discharge, weakly ionized plasma.

Enhanced atmospheric pressure corona-based weakly ionized plasma was investigated to modify surface properties of wood materials. The plasma was generated using a point-to-point bare electrode geometry without dielectric barriers. The gas-phase admixture used in this work was argon and acetylene. Wood fibers were processed in the post-discharge region outside of the harsh corona environment. Return corona emanating into the high-voltage gap from the grounded screen was utilized to effectively activate acetylene molecules near the substrate. Scanning electron microscopy was used to study the surface morphology of the treated and untreated substrates. The treated wood material was observed to contain on their surface nano- and micro-nodules of plasma-polymerized acetylene. Capillary rise measurements confirmed changes in the surface wettability of the substrates. The water capillary rise rate and diffusion coefficient were reduced by about 37% and 57%, respectively, for a 15-min treatment of ponderosa pine wood flour.

No abstract

A corona based weakly ionized plasma source was developed to deposit plasma polymerized acetylene coating at atmospheric pressure. The plasma source included a distinctive point-topoint geometry consisting of an array of high voltage needles and an array of protrusions placed over a grounded screen. The geometry facilitated various corona discharge modes that included return corona to contribute plasma polymerized acetylene deposition downstream from the corona section. Scanning probe techniques were used to investigate deposition on both the leading surface and the trailing surface of substrates. Deposition was initiated as distinct nodules that merged to form a thin plasma polymerized coating.