Surface Treatment with Atmospheric Pressure Plasma

Various surface treatments on zirconia have been reported for dental porcelain veneer. However, it has not been determined which of these treatments provide the highest bond strength. The purpose of this study is to compare the effect of airborne particle abrasion and atmospheric pressure plasma treatment on the shear bond strength between zirconia and dental porcelain veneer. The groups were divided into four groups according to the surface treatment method: the control group, the atmospheric pressure plasma treated group (group P), the airborne particle abrasion group (group A), the atmospheric pressure plasma treated group after the airborne particle abrasion (group AP). Atmospheric pressure plasma was applied on the specimens using a plasma generator (Plasma JET, POLYBIOTECH Co. Ltd., Gwangju, Korea) and airborne-particle abraded with 110 µm. The characteristics of surface treated zirconia were analyzed by 3D-OP, XRD, XPS and contact angle. The shear bond strength was tested using a universal testing machine. The shear bond strength of group P was significantly increased compared to that of the control group (P < 0.05). The shear bond strength of group AP was significantly increased as compared to group A (P < 0.05). There was no significant difference between the group P and group A (P > 0.05). As a result of this study, the atmospheric pressure plasma treatment showed significantly higher shear bond strength than control group, but similar to the airborne particle abrasion, and the atmospheric pressure plasma treatment after the airborne particle abrasion provided the highest shear bond strength. This study demonstrated that application atmospheric pressure plasma treatment on zirconia may be useful for increasing bond strength between zirconia and dental porcelain veneer.

The reaction process model during initial nitridation of Si (111) using atmospheric pressure plasma source was constructed and it was compared to that using a radio frequency plasma source. In atmospheric pressure plasma, emission lines from the N2 second positive system were dominantly observed. By exposing the atmospheric pressure plasma to Si substrate at the temperature ranging from 25to500°C, silicon nitride films with a thickness below 1.8nm were formed. In order to study the nitridation process, the changes in the film thickness against the substrate temperature and nitridation time were systematically studied at a pressure ranging from 50to700Torr. The film thickness increases with increasing the nitridation pressure below 400Torr and it saturates above 500Torr. It was completely regardless of the substrate temperature. From the time dependence of the film thickness at various nitridation pressures, it was revealed that these experimental results were well fitted to a Langmuir-type adsorption model. In the case of nitridation using atmospheric pressure (AP) plasma, molecular species play an important role for nitridation without thermal diffusion. The difference of silicon nitride films fabricated using AP plasma and rf plasma originates from the difference in the active species.

Carbon fiber reinforced polymer (CFRP) has a wide range of applications in aerospace, automobile, marine, and other industries, due to its remarkable mechanical properties and lightweight. It can enhance the performance of the structural components and has been presented to be a good alternative over conventional materials. Adhesive bonding has been widely employed, and research studies on the surface modification of CFRP have been conducted to improve the load resistance of adhesive bonding, of which atmospheric pressure (AP) plasma is the most preferred method. However, there is still a lack of study on the effectiveness and strategies of AP plasma surface modification. To gain more insight, possible sources that would have influence on the adhesive bonding were analyzed by preparation of different surface configurations of CFRP. It is confirmed that AP plasma can increase the surface polarity and wettability of the carbon fiber surface. It can contribute to the removal of surface contamination element as well. Although the surface morphology and surface roughness before and after the AP plasma treatment does not show noticeable changes, the single‐lap shear strength of the contaminated samples can be effectively improved. This study validates that AP plasma is effective on surface contamination removal and bonding quality improvement, which provides a potential alternative for the adhesive bonding improvement and surface modification of carbon fiber.Highlights Surface polarity and wettability increase of CFRP by AP plasma. Surface contamination removal and bonding quality improvement by AP plasma. AP plasma provides a potential alternative method for adhesive bonding pre‐treatment. AP plasma surface modification mechanism analysis via surface characterization.

Plasma nanosciences and technologies have been leading all industries with bringing about innovations in green and life fields. The non-equilibrium chemical reactions induced by the synergetic effect of ions and radicals in the plasma processing has enabled to realize the isotropic etching with a high aspect ratio, the synthesis of functional nanomaterials through the plasma assisted self-organization and the surface chemical modification and so on in low pressure plasmas. In precise etching processes, the critical size dimension for the nanoscale pattering will be below 1nm and then the control of radical based on reactions on the side wall in the fine pattern with a nanoscale in size is of crucial importance. Additionally, the precise control of radicals is also strongly demanded in nanomaterial plasma processing. Carbon nanomaterials such as nanotubes, nanographenes and nanowalls attracted much attentions. They were synthesized by the plasma assisted self-organization, which was controlled by ions and/or radicals. Recently, the atmospheric pressure plasma and the in-liquid plasma have been developed. These plasmas have been successfully applied not only to the nanomaterial processing in the green innovation but also to the medical and agriculture fields in the life innovation. In these extremely complicated reactions, spatiotemporal controlling of radicals is a key point. Therefore, the measurement of behaviors of radicals in plasma nanoprocesses and thus the control of radicals on the basis of measured results has become important. We have been synthesizing a carbon nanowall, which is a two dimensional grapheme layers are standing vertically on the substrate, by the radical-controlled plasma processing. The structural control of carbon nanowalls was successfully performed by the radical injection to the plasma. Varieties of morphologies of carbon nanowalls were synthesized by controlling radicals and applied to fuel cell devices, catalysis devices and bio template and so on. Furthermore, ultrahigh density plasmas in the atmospheric pressure and in the liquid produce high density radicals. We have synthesized nanographenes by using the in-liquid plasma with alcohols. These nanographenes were also applied to the fuel cell devices. The atmospheric pressure plasma has been exposed to various kinds of cancer cells resulting in killing them. We found that ovarian cancer cells were successfully killed selectively against normal cells by the atmospheric pressure plasma and/or the plasma activated medium. In the case of synthesis of the plasma activated medium, controlling of densities of O radicals together with N and NO radicals exposed to the liquid medium was important to produce the optimum chemical species in the medium, which will be effective to kill cancers in vitro and in vivo. The systematical control of radicals in the nanoscale space at the gas and the liquid phase is a key issue to develop the plasma medicine, too. Therefore, we have stressed on the importance of development of an autonomous control plasma manufacturing system in order to accelerate green and life innovations. This system has multi-monitors to detect chemical reactions in the gas, the surface and interface between the gas and liquid, and in the liquid. On the basis of integration of measured results, it will make the precise control of species, especially radicals in the low pressure, atmospheric pressure and in-liquid plasmas. In this article, cutting edge plasma nanoprocesses with the radical-control in the plasma nanoprocesses for the synthesis of nanocarbons in the green innovation and with that in the plasma medical treatment of cancers in the life innovation are introduced and the future vision for the next generation’s plasma nanoprocessing will be presented.

Although an adhesive joint can distribute load over a larger area than a mechanical joint, requires no holes, adds very little weight to structures and has superior fatigue resistance, it requires careful surface preparation of adherends for reliable joining and low susceptibility to service environments. The load transmission capability of adhesive joints can be improved by increasing the surface free energy of the adherends with suitable surface treatments. In this study, two types of surface treatment, namely the low pressure and the atmospheric pressure plasma treatment, were performed to enhance the mechanical load transmission capabilities of carbon/epoxy composite adhesive joints. The suitable surface treatment conditions for carbon/epoxy composite adhesive joints for both low and atmospheric pressure plasma systems were experimentally investigated with respect to chamber pressure, power intensity and surface treatment time by measuring the surface free energies of the specimens. The change in surface topography of carbon/epoxy composites was measured with AFM (Atomic Force Microscopy) and quantitative surface atomic concentrations were determined with XPS (X-ray Photoelectron Spectroscopy) to investigate the failure modes of composite adhesive joints with respect to surface treatment time. From the XPS investigation of carbon/epoxy composites, it was found that the ratio of oxygen concentration to carbon concentration for both low and atmospheric pressure plasma-treated carbon/epoxy composite surfaces was maximum after about 30 s treatment time, which corresponded with the maximum load transmission capability of the composite adhesive joint.

We investigated the effect of the atmospheric pressure plasma (APP) and low pressure plasma (LPP) treatments on the performance of organic light emitting diodes (OLED). The increase of surface energy was mainly attributed to polar component and Lewis base interaction, independent of either APP or LPP treatments. O2 LPP-treated surface showed more uniform roughness than Ar/O2 APP-treated surface. All plasma treatments increased the amount of oxygen, which led to the improvement of work function, while decreasing the amount of carbon. All treatments except only Ar APP treatment decreased the amount of dopant-tin. O2 LPP-treated ITO showed the highest value of work function because of the efficient removal of carbon contamination, together with the improvement of In/Sn ratio, and the uniformity of surface roughness. Thus, the organic light-emitting diode fabricated on the surface of O2 LPP-treated ITO substrate exhibited superior brightness.

Over the last decade, the number of researches has increased in the field of bonding technologies. Researchers attempt to improve surface adhesion properties by surface treatments. Adhesive bonding is one of these bonding techniques, where it is important to see what surfaces will be bonded. One such surface property is wetting, which can be improved by several types of surface treatment. In recent years, atmospheric pressure plasmas have appeared, with which research is ongoing on surface treatments. In our research, we will deal with the effects of plasma surface treatment at atmospheric pressure and its measurement. In addition, we summarize the theoretical background of adhesion, surface tension and surface treatment with atmospheric pressure plasma. Our goal is to improve adhesion properties and thus the adhesion quality.

Atmospheric pressure plasma surface modification of titanium for high temperature adhesive bonding

Among commercial polymer materials, polypropylene (PP) is the most preferred in the world. Low‐density materials such as polymers and polymer composites are increasingly used to produce lighter structures. In the automotive industry, these parts are used for painting. Due to the non‐polar surface chemistry of PP, PP surfaces have low surface energy, which causes weak bonds in coating, painting, and bonding processes. Therefore, various physical and chemical processes are used to increase the surface energy of PP first, and then the surface is prepared with a primer before painting. However, the primer material and surface treatments used have disadvantages such as extra cost, being harmful to the environment, and the use of fossil fuels. Atmospheric pressure plasma (APP) surface treatment has recently become an alternative to traditional methods. In this study, the chemical and physical changes caused by APP surface treatment on PP surfaces were examined, the effects of process parameters were investigated, and the paintability of surfaces with and without primer was investigated.Highlights Primerless painting feasibility per standards is under investigation. Eco‐friendly alternatives to traditional pre‐paint treatments are under study. Polypropylene surface properties' effects on painting are under study. Optimal atmospheric pressure plasma parameters for painting are determined.

For several years now, atmospheric pressure plasma has been discussed as a future technology. It is a key technology with a long and successful past. For many decades, corona treatment has been an atmospheric pressure plasma application, well established within the extrusion and converting industry. Corona technology has been applied in industrial use since the 1950s, mostly within converting polymer films and to some degree paper, board, and metal foil. Corona treatment is used to improve the adhesion of printing inks, lacquers, adhesives, and coatings. From this strong base, atmospheric pressure plasma is growing into new applications. This paper introduces atmospheric pressure plasma basics and compares modern atmospheric pressure plasma technologies for grafting chemical functional groups on polymer surfaces.

Surface treatment for Cu metallization on polyimide film by atmospheric pressure dielectric barrier discharge plasma system

We investigated the effect of atmospheric-pressure plasma (APP) and low-pressure plasma (LPP) treatments on the performance of organic light emitting diodes (OLEDs) with an indium tin oxide (ITO) layer. The Owens–Wendt and Lifshitz–van der Waals acid-base methods revealed that the increase of surface energy was mainly attributed to polar component and Lewis base interactions, respectively, independent of either APP or LPP treatments. Unlike APP treatment, LPP treatment more plentifully produced reactive oxygen species in the plasma. Therefore, the LPP-treated ITO surfaces slowly proceeded with reorientation compared to APP-treated ITO. The carbon content in untreated ITO was approximately 0.045%, while those of Ar APP-, APP-, and LPP-treated ITO were 0.014, 0.011, and 0.010%, respectively, mostly containing incorporated reactive oxygen. The LPP-treated surface showed more uniform roughness than Ar or APP-treated surfaces. The highest work-function value was obtained from LPP-treated ITO, intermediate values from Ar and APP-treated ITOs, and the smallest value from untreated ITO . Thus, OLED fabricated on the surface of LPP-treated ITO substrate exhibited superior performance among all plasma-treated samples.

Nonthermal plasmas generated under atmospheric pressure (AP) have been receiving increased attention in direct plasma technology applications for thin film deposition. This is because the atmospheric-pressure plasma-enhanced chemical vapor deposition (AP-PECVD) is expected to realize low-cost and high-throughput processing with open air systems, which are of prime importance for various industrial applications. A large number of studies have been reported on the preparation of thin films using various types of AP plasma sources such as corona, dielectric barrier and AP glow discharges excited by pulsed or low-frequency power sources that can produce a nonequilibrium AP plasma. Most of the reported films using these common AP plasma sources have been related to polymers, oxides, and carbon materials. On the other hand, by virtue of the low ion energy due to the high collision frequency, AP-plasma process can have a nature of soft or gentle processing in addition to high-rate processing. Therefore, AP-PECVD also has a potential to form good-quality functional thin films, such as high-purity semiconductor or insulator thin films, which may be applicable for electronic devices. Although the development of AP-PECVD technology for such applications are attractive in the future advanced industry, the reports on these applications are limited. The reason may be related to the fact that the high collision frequency in AP plasma enhances secondary reactions in the gas phase to generate dust particles which will deteriorate the film quality, and also limits mass transport, which leads to poor uniformity of the resulting film. In the present article, the authors review the present status of AP low-temperature plasma processes, bearing in mind their application for high-purity functional thin films including silicon and related materials. The authors first summarize recent progress in the use of common AP plasma sources for direct PECVD processes. To grasp the present status of AP-PECVD technique, the authors have picked up popular materials for AP-PECVD, such as carbon, oxides, and other inorganic materials as well as silicon and related materials. Although there already exists a plenty of good review articles dealing with PECVD using common AP plasma sources, works on reviewing PECVD using radio-frequency (RF) and very-high-frequency (VHF) excitations of AP plasma seem to be insufficient. RF and VHF excitations of AP plasma are capable of generating continuous oscillating glow discharges without unstable streamers and filaments, which will be important to form uniform and dust-free films. So, secondly, the authors discuss the key distinguishing features of PECVD using RF and VHF excitations of AP plasma from the common AP plasma sources. Finally, they describe examples of the application of AP-VHF plasma to the preparation of silicon and related thin films.

Atmospheric plasma treatment is an effective and economical surface treatment technique. The main advantage of this technique is that the bulk properties of the material remain unchanged while the surface properties and biocompatibility are enhanced. Polymers are used in many biomedical applications; such as implants, because of their variable bulk properties. On the other hand, their surface properties are inadequate which demands certain surface treatments including atmospheric pressure plasma treatment. In biomedical applications, surface treatment is important to promote good cell adhesion, proliferation, and growth. This article aim is to give an overview of different atmospheric pressure plasma treatments of polymer surface, and their influence on cell-material interaction with different cell lines.

Surface modification of polymers has been widely studied because of the industrial interest in several applications involving adhesion, packaging and metallization, among others. Plasma treatment, particularly atmospheric pressure plasma, is one of the most versatile techniques in surface modification. In this work, atmospheric pressure plasma treatment was performed to modify a polycarbonate surface. The effects of the treatment were sensitive to both the plasma ambient and the time elapsed after treatment. Surface treatment with a dielectric barrier discharge plasma torch produced an increase in the wettability of polycarbonate through the creation of COH polar groups on its surface, together with surface roughness. These effects were more pronounced by the addition of oxygen in an Ar gas mixture and the surface treatment time. In general, the atmospheric plasma torch treatment helped to enhance the wettability of the aqueous solutions to form a multi‐layered inorganic film on the polycarbonate. Copyright © 2010 John Wiley &amp; Sons, Ltd.