Direct-current discharge

Abstract: Due to the unique properties of ionic liquids such as their extremely low vapor pressure and high heat capacity, we have succeeded in creating the static and stable gas (plasmas)-liquid (ionic liquids) interfacial field using a direct current discharge under a low gas pressure condition. It is clarified that the ionic liquid works as a nonmetal liquid electrode, and furthermore, a secondary electron emission coefficient of the ionic liquid is larger than that of conventional metal electrodes. The plasma potential structure of the gas-liquid interfacial region, and resultant interactions between the plasma and the ionic liquid are revealed by changing a polarity of the electrode in the ionic liquid. By utilizing the ionic liquid as a cathode electrode, the positive ions in the plasma region are found to be irradiated to the ionic liquid. This ion irradiation causes physical and chemical reactions at the gas-liquid interfacial region without the vaporization of the ionic liquid.

Abstract: The work was aimed to study an effect of direct current discharge on chemical structure, surface properties and cell response to the plasma modified composite films. The film samples were prepared by solvent casting from colloidal solution of the ternary blend of chitosan, gelatin and poly(L,L-lactide), PLLA, obtained by solid-state reactive blending (SSRB), in CH 2 Cl 2 and treated with air plasma at pressure of 10–20 Pa and a discharge current of 50 mA for 60 s. The model film samples casted from the initial components were treated and studied as well. Contact angle of wettability measurements of the films showed that plasma modification led to increase of hydrophilicity and surface energy. Contact angle changes after plasma treatment of chitosan/gelatin/PLLA (CGP) film were more similar to those for the poly(L,L-lactide) film. X-ray photoelectron spectroscopy (XPS) data confirmed that a surface layer of the blend films was enriched with a polyester component. However, study of mouse fibroblast (L929) attachment and growth on the films showed that the CGP film provided an enhanced cell growth compared to this on the poly(L,L-lactide) film. Plasma modification of the polymer films resulted in a substantial increase in fibroblast viability on the plasma treated poly(L,L-lactide) films and to a rather strong decrease of cell growth on the plasma treated CGP and chitosan ones. Thus, plasma surface modification could be proposed as a good tool to control cell response on the material surface.

Abstract: The invention relates to a method for depositing a diamond coating on a workpiece, for instance a drawing die or a tool punch, whereby a reactive plasma supported coating method is used. According to the invention the generation of the plasma is made by a direct current discharge, whereby additionally a flow of charged particles is fed into the discharge gap; according to the invention the workpiece to be coated is positioned in the discharge gap. Due to the inventive design a relatively long discharge gap can be used, such that also large surface areas can be coated; the coating is made at a location of the highest homogeneity and density of the plasma. By means of the invention a method is provided which can be controlled regarding financial expenses and in a reliable manner and which is suitable for large surface area coating.