Glow Discharge Treatment Research Articles

Oxidation of 1020 steel in the abnormal glow discharge

1020 steel is a material very used for surface treatment in the abnormal glow discharge. Because the composition of the gaseous atmosphere has an important influence on the results of plasma treatment, in this work the oxidation process of 1020 steel is verified on the abnormal glow discharge under different concentrations of air (20% to 100%) at temperatures of 600°C and 900°C. For each atmosphere used mass variation is measured during the process of surface oxidation, the structure and microstructure of the oxide film formed is observed and also its mechanical properties through its microhardness.

Quantitative measurement of hydrophilicity/hydrophobicity of the plasma-polymerized naphthalene film (Super Support Film) and other support films and grids in electron microscopy.

Hydrophilicity/hydrophobicity of the surfaces of plasma-polymerized naphthalene film (Super Support Film, Nisshin EM Co. Ltd., Tokyo), carbon and formvar support films, and copper and nickel grids were quantitatively estimated by contact angles measured from diameters and heights of water droplets placed on various specimens. With treatment of glow discharge, the surfaces of plasma-polymerized naphthalene and carbon support films became fully hydrophilic in 20 s. They remained hydrophilic for 6 h. The surfaces of copper and nickel grids became fully hydrophilic with 60 s of glow discharge treatment. They remained hydrophilic for only 1 h. This information is useful for negative staining, ultrathin sectioning and rapid freezing of biological specimens using the sandwich method.

Fabrication of SERS substrate for the detection of rhodamine 6G, glyphosate, melamine and salicylic acid

We report on the development of a highly sensitive and novel surface enhanced Raman scattering (SERS) substrate for the detection of analytes, such as rhodamine 6G (R6G), glyphosate, melamine and salicylic acid. The fabrication steps include (a) cleaning the surface of the Cu-grids on carbon support layer with an initial glow discharge treatment, (b) layering of carbon film with a thickness of 3nm, (c) application of 24μl volumes of silver colloid to form silver dendrites, and (d) a glow discharge treatment of silver dendrites to remove surface debris or particles. The substrate demonstrated excellent SERS measurement reproducibility, along with a significant SERS enhancement factor of 6.1×105 of Raman signals and highly informative chemical signature of R6G. The SERS substrate can be used as a quantitative tool. The protocols for fabrication of the substrate are inexpensive and it is more sensitive than conventional Raman technique and a commercial product. Highly sensitive detection limits for R6G (240ppb), glyphosate (845ppb), melamine (630ppb) and salicylic acid (600ppb) were achieved with this substrate. This study has shown that the Ag-Cu-grid substrate is well suited for routine environmental monitoring of chemical residues and the detection of plant metabolites. The stability of the nano-structured Ag-Cu-grid was demonstrated during a 4 week storage period.

Fabrication of a flexible graphene–TiO2/PDMS photocatalytic film by combining air atmospheric pressure glow discharge treatment

This work reported a universal and effective route to fabricate a kind of flexible photocatalyst film to broaden the scope of application (wearable photocatalyst devices for example). This technology roadmap is premised on the air atmospheric pressure glow discharge (AAPGD) pretreatment. Through treating poly (dimethyl siloxane) (PDMS) with AAPGD technique, the PDMS surface is functionalized by hydroxyl groups and the contact angle gains a minimum value of about 26.0, which make it easy to be decorated for the desired efficiency. Then the PDMS surface can be endowed with photocatalytic activity through wet-chemical method without the bondage of inherent hydrophobic-nature. Owing to the hydrophilic surface, the graphene can be inserted to improve the photocatalytic performance and the flexibility of graphene was kept. Compared with the photocatalysts films without AAPGD pretreatment, the photocatalytic performance of films suffering from AAPGD pretreatment is much higher. Therefore this flexible film strategy, based on AAPGD pretreatment, is of great significance to design flexible photocatalysts films, pushing forward the development of wearable photocatalyst devices.

Plasma-Based Graphene Functionalization in Glow Discharge

Glow discharge was utilized to add oxygen functional groups to the graphene platelets sample produced in chemical exfoliation synthesis. It was concluded based on Raman spectra that the graphene sample treated with the glow discharge preserves specific graphene features while no transformation to amorphous carbon is happening. SEM and EDS results indicated the increases of oxygen content in the graphene sample after the exposure to the glow discharge. Raman spectra also support the fact that the graphene platelets have been decorated with oxygen as the result of the glow discharge treatment.

Destruction of sodium lauryl sulfate in its aqueous solutions by contact glow discharge treatment

Degradation of the anionic surfactant sodium lauryl sulfate (C12H25SO4Na, SLS) in its aqueous solutions with concentrations of 0.02–1.1 mmol/L acting as a liquid cathode of atmospheric-pressure dc discharge in air at a discharge current ranging within 20–100 mA has been studied. The products of degradation in the liquid phase have been identified, and the kinetic characteristics of their formation at an initial SLS concentration of 5 × 10−3 g/L (∼0.02 mmol/L) and a discharge current of 40 mA have been determined.

Abstract 200: Development and Proof of Concept Testing of an Ex Vivo Perfusion Chamber for Studying Platelet Adhesion to Coronary Stents Under Physiological Conditions

Background: Current-generation drug-eluting stents unblock atherosclerotic arteries, inhibit restenosis, but also render the artery prone to thrombosis by inhibiting endothelial cell function. Hence, there is strong clinical interest in developing stents that inhibit restenosis, yet are less thrombogenic. Goals of this study were to 1) develop an ex vivo method to measure platelet adhesion and aggregation on coronary stents under clinically-relevant conditions, and 2) test the hypothesis that treating metal stents with trimethylsilane (TMS) through a novel glow discharge process that coats stents with a nanoscale layer of hydrophobic plasma coating, with or without additional post-deposition glow discharge treatment with NH 3 and O 2 gas, generating elemental nitrogen and oxygen on the stent surface, inhibits platelet adhesion to stents. Methods: Bare-metal stents (BMS) made of 316L stainless steel was deployed in Masterflex tubing by inflating an over-the-wire coronary balloon within the stent. Tubing containing stents was filled with porcine indium-labeled platelets in anticoagulated whole blood and the ends were connected to create a closed circuit, which was connected to a peristaltic pump to generate unidirectional flow with shear stress of 67 s -1 , similar to that present in human coronary arteries. After 30 min of continuous flow at 37°C the tubing was disconnected and extensively rinsed to remove blood. Platelet adhesion to stents was measured with a gamma counter and by scanning electron microscopy (SEM). Results: Platelet adhesion to metal stents treated with TMS followed by NH 3 and O 2 (DC-TMS+NH 3 /O 2 ) was 56±8.2% reduced compared to BMS (n=12; P=0.003), whereas TMS treatment alone did not significantly inhibit platelet adhesion. SEM confirmed significantly decreased platelet deposition on DC-TMS+ NH 3 /O 2 stents vs. BMS. Conclusions: A novel glow discharge surface modification involving TMS, NH 3 , and O 2 gas generates stents with a bioactive surface that resists platelet adhesion under physiological conditions. Our ex vivo perfusion circuit facilitates rapid and precise comparison of stent thrombogenicity under physiological conditions, which should prove useful to other investigators developing coronary stents for clinical use.

Destruction of sulfonol in its aqueous solutions by contact glow discharge treatment: 2. Mechanisms and kinetic simulation

A mechanism for the degradation of Sulfonol in its aqueous solutions acting as a liquid cathode of atmospheric-pressure dc discharge in air and for the formation of the products has been proposed, and the chemical kinetics of the degradation processes has been numerically simulated.

Destruction of sulfonol in its aqueous solutions by contact glow discharge treatment: 1. Product formation kinetics

Degradation of the anionic surfactant Sulfonol (sodium alkylbenzenesulfonate) in its aqueous solutions acting as a liquid cathode of atmospheric-pressure dc discharge in air has been studied. The products of plasma-chemical decomposition of Sulfonol in the liquid phase have been identified. The kinetic characteristics of the formation of products of plasma-chemical reactions at a substrate concentration of 5 × 10−3 g/L (0.014 mmol/L) and a discharge current of 40 mA have been determined.

Effect of plasma-chemical and thermal treatment in oxygen on the activity of Na3ZrM(PO4)3 phosphates (M = Zn, Co, Cu) in the transformation of butanol-2

The catalytic properties of plasma-chemically and thermally treated triple zirconium orthophosphates Na3ZrM(PO4)3 (M = Zn, Co, Cu) in the transformation of butanol-2 are studied. X-ray photoelectron spectroscopy data indicate that the surface composition of the samples differs from the stoichiometry, especially in the case of M = Cu. The partial reduction of copper ions occurs during plasma-chemical treatment (PCT), while the amount of Cu on the surface of Na3ZrCu(PO4)3 diminishes. Treatment in an oxygen glow discharge results in a 3–8 times greater yield of the alcohol dehydrogenation product, methyl ethyl ketone. The energy of the alcohol’s bonds with the surface is reduced and the dehydration active sites become fully inactivated. In contrast, thermal treatment (TT) results in an increase in the activity of Na3ZrM(PO4)3 in the dehydration of butanol-2.

Bone Response to Surface-Modified Titanium Implants: Studies on the Early Tissue Response to Implants with Different Surface Characteristics

In a series of experimental studies, the bone formation around systematically modified titanium implants is analyzed. In the present study, three different surface modifications were prepared and evaluated. Glow-discharge cleaning and oxidizing resulted in a highly stoichiometric TiO2 surface, while a glow-discharge treatment in nitrogen gas resulted in implants with essentially a surface of titanium nitride, covered with a very thin titanium oxide. Finally, hydrogen peroxide treatment of implants resulted in an almost stoichiometric TiO2, rich in hydroxyl groups on the surface. Machined commercially pure titanium implants served as controls. Scanning Auger Electron Spectroscopy, Scanning Electron Microscopy, and Atomic Force Microscopy revealed no significant differences in oxide thickness or surface roughness parameters, but differences in the surface chemical composition and apparent topography were observed. After surface preparation, the implants were inserted in cortical bone of rabbits and evaluated after 1, 3, and 6 weeks. Light microscopic evaluation of the tissue response showed that all implants were in contact with bone and had a large proportion of newly formed bone within the threads after 6 weeks. There were no morphological differences between the four groups. Our study shows that a high degree of bone contact and bone formation can be achieved with titanium implants of different surface composition and topography.

Diminished fracture initiation sites in ceramic layers bonded to glow-discharge treated substructure

A mechanically retentive structure and meticulous surface cleanliness are critical factors in providing fracture resistance and clinical success of metal ceramic restorations. This investigation compared the porcelain/metal interfaces of deliberate compressive fractures of ceramic crowns between conventional preparation and application of the Radio Frequency Glow Discharge Treatment (RFGDT) before each bonding step. It evaluated RFGDT’s capacity to improve wetting effectiveness and minimize porosity. Twelve metal ceramic crowns were fabricated identically. RFGDT was applied to the metal substructures of half the specimens before the ceramic layering process. All specimens were fractured in the same manner by an applied compressive force to simulate dental occlusive failure. Fracture surfaces were inspected by light and scanning electron microscopy. Quantitative analyses of images were performed to identify numbers, locations of cracks, porosity patterns, and other morphological correlates of the fracture zones. There were significantly fewer voids per millimeter at the interfaces in the RFGDT group than in the non-RFGDT group (t = 2.377, df = 9, p = 0.021). There was a significant difference in the number of horizontal cracks per millimeter between the groups (t = 2.132, df = 7, p = 0.035), with more cracks occurring in the non-RFGDT group. RFGDT can improve the integrity of metal ceramic crowns by increasing the substratum surface energy, improving porcelain wetting and spreading and thereby diminishing the numbers of interfacial voids available for initiation of fracture. Routine application of RFGDT should result in fewer cracks along metal/ceramic interfaces in all restorative preparations.

Ion treatment by low pressure arc plasma immersion surface engineering processes

The gaseous plasma of low pressure arc discharges has been used extensively for various surface treatment applications including heat treatment, ion nitriding, ion implantation, PECVD and duplex processes. Highly ionized low pressure arc plasmas with electron density up to ~1018m−3 can be generated by a shielded vacuum arc cathode, a hollow cathode or by a thermionic cathode. In this paper, plasma properties are characterized by electrostatic probes and optical emission spectroscopy. A range of different species can be produced in low pressure arc plasma immersion processes via decomposition of precursor molecules by electron collisions. Surface treatment of different steels and metal alloys in such a dense plasma environment can substantially affect the surface profile. The ion nitriding of different types of steel in a low pressure arc plasma environment is investigated. The rate of ion nitriding as a function of plasma parameters, such as ion current density, pressure and gas composition is established for several types of steel and ranging from 0.1 to 1μm/min. Ionitrided layers can be produced in arc plasma immersion processes at substrate biases as low as −30V and substrate temperatures as low as 200°C, depending on the type of steel. Alternatively, low energy ion implantation of nitrogen can be produced at bias voltages exceeding −500V and substrate temperatures less than 100°C. The distribution of plasma density and the uniformity of ion nitriding layers in industrial scale vacuum processing chambers are investigated. Duplex coatings were also produced by ion nitriding in an arc plasma immersion environment followed by deposition of TiN coatings. The ion nitriding and duplex coating layers are characterized by structure, thickness, microhardness depth profile, surface roughness and coating adhesion. Surface treatment in conventional glow discharge compared to low pressure arc plasma immersion processes is presented. The results of processing complex shape components are discussed.

CF4 plasma surface modification of asymmetric hydrophilic polyethersulfone membranes for direct contact membrane distillation

Abstract This paper describes the use of CF 4 plasma modification of a hydrophilic membrane into a hydrophobic one for membrane distillation. Plasma surface modification conditions were optimized with respect to plasma glow discharge power and treatment duration using a flat sheet PES membrane. The modified membranes were characterized by X-ray photoelectron spectroscopy (XPS), SEM, contact angle measurements, pore size distribution, liquid entry pressure and atomic force microscopy. Results revealed that the plasma modification converted hydrophilic membranes of a contact angle 0° into hydrophobic ones with water contact angle above 120°. Fluorination was ascribed to the wettability change of the membrane from hydrophilic to hydrophobic via insertion and possibly deposition. Direct contact membrane distillation of the hollow fibers using 4% NaCl solution yielded a water flux of 45.4 kg/m 2 h at a feed temperature of 63.3 °C. A rather high evaporation efficiency of the membrane distillation process was estimated in comparison with literature results. Direct contact membrane distillation (DCMD) stability test showed a water flux of 42.1 kg/m 2 h using 4 wt% NaCl as feed (at the temperature of 60.5 ± 0.2 °C). No leakage was observed for 54 h indicating a stable membrane performance. The high evaporation efficiency and water flux were ascribed most probably to the high porosity of the base membrane.

Adsorption of HSA, IgG and laminin-1 on model titania surfaces – effects of glow discharge treatment on competitively adsorbed film composition

This study investigated the effect of glow discharge treatment of titania surfaces on plasma protein adsorption, by means of ellipsometry and mechanically assisted SDS elution. The adsorption and film elution of three plasma proteins, viz. human serum albumin (HSA), human immunoglobulin G (IgG) and laminin-1, as well as competitive adsorption from a mixture of the three proteins, showed that the adsorbed amount of the individual proteins after 1 h increased in the order HSA <IgG <laminin-1 ≤ protein mixture. Film elutability showed that 30 min of SDS interaction resulted in almost complete removal of adsorbed films. No difference in the total adsorbed amounts of individual proteins, or from the mixture, was observed between untreated and glow discharge treated titania surfaces. However, the composition of the adsorbed films from the mixture differed between the untreated and glow discharge treated substrata. On glow discharge-treated titania the fraction of HSA increased, the fraction of laminin-1 decreased and the fraction of IgG was unchanged compared to the adsorption on the untreated titania, which was attributed to protein–protein interactions and competitive/associative adsorption behaviour.

Synthesis and characterization of nanocrystalline calcium sulfate for use in osseous regeneration

Nanoparticles of calcium sulfate (nCS) have potential advantages as a ceramic matrix, scaffold and/or vehicle for delivering growth factors for osseous regeneration in a variety of clinical situations. The objectives of this study were to synthesize and characterize nanoparticles of hemihydrate calcium sulfate (nCS) and to develop a nCS-based system for bone regeneration. A cryo-vacuum method was used to process dihydrate CS into dihydrate nCS, which was then subjected to oven drying to produce hemihydrate. The nCS was sterilized by glow discharge treatment for use as a synthetic graft material for the treatment of bone defects. Electron microscopy showed that the nCS powder consisted of aggregates of closely arranged acicular crystals, approximately 30–80 nm in width, 400–600 nm in length and approximately 80–100 nm in diameter, providing a surface area about ten times that of conventional CS. Thorough physico-chemical characterization confirmed the composition and phase of the material. Cell viability/metabolic activity assays and alkaline phosphate assays confirmed the safety and biocompatibility of nCS. Release kinetics for adsorbed platelet-derived growth factor and bone morphogenetic protein-2 (BMP-2) suggests that nCS may serve as an appropriate vehicle for slow release delivery of these agents. The studies presented here give evidence of the advantages of nCS as a scaffold to support osteoblastic cell activity.

Selective fibronectin adsorption against albumin and enhanced stem cell attachment on helium atmospheric pressure glow discharge treated titanium

Successful tissue integration of implanted medical devices depends on appropriate initial cellular response. In this study, the effect of helium atmospheric pressure glow discharge (He-APGD) treatment of titanium on selective protein adsorption and the initial attachment processes and focal adhesion formation of osteoprogenitor cells and stem cells were examined. Titanium disks were treated in a self-designed He-APGD system. Initial attachment of MC3T3-E1 mouse pre-osteoblasts and human mesenchymal stem cells (MSCs) was evaluated by MTT assay and plasma membrane staining followed by morphometric analysis. Fibronectin adsorption was investigated by Enzyme-Linked ImmunoSorbant Assay. MSCs cell attachment to treated and non-treated titanium disks coated with different proteins was verified also in serum-free culture. Organization of actin cytoskeleton and focal adhesions was evaluated microscopically. He-APGD treatment effectively modified the titanium surfaces by creating a super-hydrophilic surface, which promoted selectively higher adsorption of fibronectin, a protein of critical importance for cell/biomaterial interaction. In two different types of cells, the He-APGD treatment enhanced the number of attaching cells as well as their attachment area. Moreover, cells had higher organization of actin cytoskeleton and focal adhesions. Faster acceptance of the material by the progenitor cells in the early phases of tissue integration after the implantation may significantly reduce the overall healing time; therefore, titanium treatment with He-APGD seems to be an effective method of surface modification of titanium for improving its tissue inductive properties.

Use of atmospheric pressure plasma to confer durable water repellent functionality and antimicrobial functionality on cotton/polyester blend

A non-thermal, high density atmospheric plasma glow discharge treatment was used to impart functionality to cotton/polyethylene terephthalate (PET) fabric to furnish a surface that is water repellent and then antimicrobial only. In this work, cotton/PET (50/50%) blend fabric was treated with a water repellent treatment through activating the surface with plasma, depositing a vaporized fluorocarbon based monomers, 1,1,2,2-tetrahydroperfluorodecyl acrylate (THPFDA) and 1,1,2,2-tetrahydroperfluorododecyl acrylate (THPFDDA), then graft polymerizing the monomer with a second plasma exposure. Samples were then further treated with an antimicrobial agent, diallyldimethylammonium chloride (DADMAC), a quaternary ammonium salt. Plasma treatment was used to induce free radical chain polymerization of the DADMAC, conferring a graft polymerized network on the fabric with potentially durable antimicrobial properties. It was shown that the water repellent treatment via plasma induced-graft polymerization was successful in yielding a highly hydrophobic fabric with a finish durable to laundering. The results of the antimicrobial tests showed that the treated fabric reduced the activity of both gram positive and gram negative bacteria by more than 99.994%, demonstrating that the antimicrobial agent can function effectively on the water repellent treated fabric. However, despite the evidence of the presence of fluorine containing compounds on the fabric following the antimicrobial treatment, which was confirmed by time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis, the water repellency was lost, which was attributed to changes in the orientation of the fluorocarbon polymer chains.

Interfacial Optimization of Acetate Taffeta Fabric/PLA Composites

For the interfacial optimization of Acetate Taffeta Fabric (ATF) with Poly Lactic Acid (PLA), steady-state uniform atmospheric glow discharge (AGD) and Silane treatments were studied, respectively. In AGD, the plasma polymerization time for ATF was varied up to 3 minutes. In silane treatments, three types of silane coupling agents, aminoethylaminopropyl-trimethoxysilane, 3-glycidoxypropyl-trimethoxysilane and 3-methacryloxypropyltrime-thoxysilane, were used respectively with concentrations ranging from 0 to 5%. Silane coupling agent was chosen since -OH in silane always reacts with -OH in PLA. Also, all three silanes have similar chemical structures with that of Lactic Acid. The sizing on the fabric was with a solution containing PVA, acryl and water at the ratio of 3:1:96. Peel tests were carried out for the surface modified fabrics before and after removing the sizing. Highest peel test results was obtained with 3% silane concentration. Tensile tests were carried out before analyzing the fracture surface of the composites by scanning electron microscope. Compared to raw fabric, plasma and silane treatments have improved the tensile strength at maximum of 30.4 and 27.4%, respectively.

Surface oxide net charge of a titanium alloy: Comparison between effects of treatment with heat or radiofrequency plasma glow discharge

In the current study, we have compared the effects of heat and radiofrequency plasma glow discharge (RFGD) treatment of a Ti6Al4V alloy on the physico-chemical properties of the alloy's surface oxide. Titanium alloy (Ti6Al4V) disks were passivated alone, heated to 600 °C, or RFGD plasma treated in pure oxygen. RFGD treatment did not alter the roughness, topography, elemental composition or thickness of the alloy's surface oxide layer. In contrast, heat treatment altered oxide topography by creating a pattern of oxide elevations approximately 50–100 nm in diameter. These nanostructures exhibited a three-fold increase in roughness compared to untreated surfaces when RMS roughness was calculated after applying a spatial high-pass filter with a 200 nm-cutoff wavelength. Heat treatment also produced a surface enrichment in aluminum and vanadium oxides. Both RFGD and heat treatment produced similar increases in oxide wettability. Atomic force microscopy (AFM) measurements of metal surface oxide net charge signified by a long-range force of attraction to or repulsion from a (negatively charged) silicon nitride AFM probe were also obtained for all three experimental groups. Force measurements showed that the RFGD-treated Ti6Al4V samples demonstrated a higher net positive surface charge at pH values below 6 and a higher net negative surface charge at physiological pH (pH values between 7 and 8) compared to control and heat-treated samples. These findings suggest that RFGD treatment of metallic implant materials can be used to study the role of negatively charged surface oxide functional groups in protein bioactivity, osteogenic cell behavior and osseointegration independently of oxide topography.