Glow Discharge Method Research Articles

Effects of nitrogen concentration on the microstructure and mechanical properties of nanocrystalline (TiZrNbTaMo)N high-entropy nitride coatings: Experimental investigations and first-principles calculations

Novel (TiZrTaNbMo)N high-entropy alloy nitride (HEAN) coatings were prepared by double cathode glow discharge method, at various nitrogen flow ratios (RN = N2/Ar), on to Ti-6Al-4V substrates. The effects of different nitrogen pressures, RN, on the microstructure and mechanical properties of these coatings were studied by X-ray diffraction, electron microscopy and nanoindentation. Over the range of RN values investigated, from 5% to 30%, these coatings exhibit a face centered cubic (FCC) structure and are composed of equiaxed nanocrystals between 8 and 12 nm in diameter. The thicknesses of the coatings range between 14.4 and 23.6 μm, far exceeding that of typical HEAN coatings prepared by magnetron sputtering. The (TiZrTaNbMo)N coating prepared at RN = 20% exhibits the highest values for both hardness and Young's modulus (39.7 GPa and 310.2 GPa, respectively), thus approaching the level of superhard coatings. Combined with the results of first-principles calculations, one of the most important factors governing the high hardness of these coatings is the existence of both covalent and ionic bonds between the N atom and the surrounding metal atoms. Moreover, compared with most HEAN coatings, the coatings prepared by this method exhibit an improved strength-toughness balance, which is essential for surface protection.

Multifaceted Ag-alloyed α-Ta5Si3 nanostructured coating for high-performing bioimplants

With the growth of the elderly population worldwide especially in developed countries, bioimplants with a multifunctional surface that embraces self-sterilizing trait, biocompatibility with mammalian cells, favorable bioactivities and high wear/corrosion resistance are in acute need. To meet such demand, the Ag-containing nanostructured α-Ta 5 Si 3 coating was fabricated onto Ti6Al4V alloy via double cathode glow discharge method. The effect of Ag addition on the mechanical properties of α-Ta 5 Si 3 was analyzed using first-principles calculations. The as-deposited α-(Ta 0.85 Ag 0.15 ) 5 Si 3 coatings consist of equiaxed nanocrystallites and greatly enhance the surface hardness of Ti6Al4V alloy. Moreover, the electrochemical characteristic, apatite-inducing ability, biocompatibility and antimicrobial trait of the α-(Ta 0.85 Ag 0.15 ) 5 Si 3 coatings were systematically studied for potential orthopedic application. The new coatings were found to remarkably reduce the corrosion damage of Ti6Al4V alloy in Ringer's solution. The coatings also promoted the formation of bone-like apatite layers and have a beneficial effect on MC3T3-E1 cells functions, including adhesion, spreading and proliferation. Ag alloying markedly increased the antibacterial capacity of the α-Ta 5 Si 3 coating against both Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ) strains, and the released Ag ions were found to enhance antibacterial performance. Therefore, a unique combination of diverse functional traits makes Ag-alloyed α-Ta 5 Si 3 coating an attractive choice in the design of next-generation biomedical implants for aging population. • The (Ta 0.85 Ag 0.15 ) 5 Si 3 coating improves biocorrosion resistance of Ti-6Al-4 V alloy. • Ag addition enables the antibacterial activities of the coating against both E. coli and S. aureus . • The (Ta 0.85 Ag 0.15 ) 5 Si 3 coating enhances the cytocompatibility and in vitro bioactivity of Ti-6Al-4V alloy. • Ag ion release plays a major role in the antibacterial performance of the coating.

The Microstructure and Properties of Carbon Thin Films on Nanobainitic Steel

The aim of this study was to assess whether it is possible to produce a high adhesive carbon coating by applying low-temperature RFCVD and glow discharge methods on nanobainitic X37CrMoV5-1 steel with and without nitrided sublayer. For this purpose, several methods of investigation were used: observations of coating morphology by scanning electron microscopy (SEM), analysis of bonds found in coatings (Raman spectroscopy), microhardness tests and adhesion of coatings (Scratch tests). Our research has shown that low-temperature RFCVD and glow discharge processes of nanobainitic X37CrMoV5-1 steel allow producing carbon coatings that can be described as hardened carbon coatings with very high hardness—> 2000 HV 0.25 in case of RFCVD processes and > 3300 HV 0.025 for glow discharge process and low friction coefficient—near 0.12 at 5 N load. However, the adhesion of produced coatings to the steel substrate strongly depends on the appropriate selection of the process parameters and on the proper preparation of the substrate before the deposition regarding the thermal stability of nanobainite.

Remarkable cavitation erosion–corrosion resistance of CoCrFeNiTiMo high-entropy alloy coatings

A CoCrFeNiTiMo high entropy alloy (HEA) coating was prepared onto a Ti-6Al-4 V substrate using the double cathode glow discharge method. This innovative HEA coating exhibited a duplex phase microstructure, composed of a BCC-structure solid solution phase and a tetragonal structured intermetallic phase, Co2Mo3, and possessed high hardness, high load bearing capacity and strong adhesion to the substrate. The HEA coating underwent much less severe cavitation erosion damage in a 3.5 % NaCl solution relative to Ti-6Al-4 V according to the results of electrochemical measurements and the cumulative weight loss, because of its unique combination of excellent mechanical properties and high corrosion resistance.

Synthesis and evaluation of TaC nanocrystalline coating with excellent wear resistance, corrosion resistance, and biocompatibility

To improve the mechanical properties, corrosion resistance, and biocompatibility of implanted titanium alloys, a TaC nanocrystalline coating was deposited on Ti–6Al–4V alloy using a double-cathode glow discharge method. The microstructure of the newly developed coating was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The coating exhibits a dense and uniform structure, composed of equiaxed TaC grains with an average grain size of 15.2 nm. The mechanical properties of the TaC-coated Ti–6Al–4V alloy were evaluated by a scratch tester, a nanoindentation tester, and a ball-on-disc tribometer. The average hardness of the TaC nanocrystalline coating is about 6 times higher than that of uncoated Ti–6Al–4V alloy and the specific wear rate of the coating is two orders of magnitude lower than that for Ti–6Al–4V at applied normal loads of 4.9 N under dry sliding condition. The electrochemical behavior of the TaC nanocrystalline coating after soaking in Ringer's solution for different periods was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Furthermore, in vitro cytocompatibility of the coating was assessed using MC3T3-E1 mouse osteoblastic cells. The results showed that the TaC coating exhibits better corrosion resistance and biocompatibility as compared to uncoated Ti–6Al–4V alloy.

High Quality Graphene Thin Films Synthesized by Glow Discharge Method in A Chemical Vapor Deposition System Using Solid Carbon Source.

Arc discharge is traditionally used to synthesize randomly arranged graphene flakes. In this paper, we substantially modify it into a glow discharge method so that the discharge current is much more reduced. The H2 and/or Ar plasma etching of the graphitic electrode (used to ignite the plasma) is hence much gentler, rendering it possible to grow graphene in thin film format. During the growth at a few mbar, there is no external carbon gas precursor introduced. The carbon atoms and/or carbon containing particles as a result of the plasma etching are emitted in the chamber, some of which undergo gas phase scattering and deposit onto the metallic catalyst substrates (Cu-Ni alloy thin films or Cu foils) as graphene sheets. It is found that high quality monolayer graphene can be synthesized on Cu foil at 900 °C. On Cu-Ni, under the same growth condition, somewhat more bilayer regions are observed. It is observed that the material quality is almost indifferent to the gas ratios, which makes the optimization of the deposition process relatively easy. Detailed study on the deposition procedure and the material characterization have been carried out. This work reveals the possibility of producing thin film graphene by a gas discharge based process, not only from fundamental point of view, but it also provides an alternative technique other than standard chemical vapor deposition to synthesize graphene that is compatible with the semiconductor planar process. As the process uses solid graphite as a source material that is rich in the crust, it is a facile and relatively cheap method to obtain high quality graphene thin films in this respect.

Investigation of slurry erosion-corrosion behavior of Ta(Si1−xAlx)2 nanocrystalline coatings

To enhance the erosion-corrosion resistance of titanium alloys, two Ta(Si1−xAlx)2 coatings with different Al content were deposited on Ti−6Al−4V alloy by double cathode glow discharge method. The coatings consist of single hexagonal C40 structured TaSi2 phase, which forms an equiaxed grain structure with an average diameter of ∼5 nm. Al addition was found to enhance the values of H/E and adhesive strength between the substrate and coating. The erosion–corrosion behavior of the coatings was studied in a liquid–solid acid slurry flow (specifically a medium of 5 wt% HCl solution that contained a 10 wt% concentration of silica-based sand) using electrochemical measurements, weight loss tests and SEM observation. The results indicated that the ternary Ta(Si0.875Al0.125)2 coating provided better protection, compared to the binary TaSi2 coating, against the combined attack of mechanical erosion and electrochemical corrosion in a liquid–solid acid slurry flow. This is attributable to high self-healing ability of the surface passive film and a higher H/E ratio.

Influence of Ag alloying on the antibacterial properties, bio-corrosion resistance and biocompatibility of α-Nb5Si3 nanocrystalline coating

To improve the corrosion resistance and impart the bioactivity and antibacterial functionalities to titanium alloys for biomedical applications, α-(Nb1-xAgx)5Si3 compounds, with three different Ag contents, were deposited on Ti–6Al–4V by double cathode glow discharge method. The new α-(Nb1-xAgx)5Si3 coatings, each about 16 μm in thickness, exhibited a compact uniform structure, composed of equiaxed nanocrystalline grains. Nanoindentation measurements revealed that Ag alloying reduced the hardness (H) and elastic modulus (E) values of the α-(Nb1-xAgx)5Si3 coatings. Compared to Ti–6Al–4V, the α-(Nb1-xAgx)5Si3 coatings exhibited improved corrosion resistance in Ringer’s physiological solution, as well as newly added in-vitro bioactivity and antibacterial ability against both E. coli and S. aureus. A MTT assay experiment shows that the two α-(Nb1-xAgx)5Si3(x = 0 and 0.05) coatings were as non-cytotoxic as bare Ti-6Al-4V. However, the MC3T3-E1 osteoblast-like cell viability for the α-(Nb0.9Ag0.1)5Si3 coating was slightly reduced, suggesting that the proliferation of MC3T3-E1 osteoblast-like cell was affected to some degree by excess Ag added to α-Nb5Si3. Overall, the α-(Nb0.95Ag0.05)5Si3 coating provides an attractive combination of good bioactivity, high corrosion resistance and new antibacterial function, and thus demonstrates great potential for applications in orthopedic devices.

Biomineralization of Titanium Alloy with Surface Micro - and Nanoscaled Modifications

The aim of the present study was to characterize two kinds of TiN/TiO2 coatings in terms of topography, composition, and electrochemical stability after immersion in simulated body fluid (SBF). Micropatterning of the substrate (Ti-5Al-4V alloy) was done by using electron beam modification (EBM) by scanning electron beam while nanostructured TiN/TiO2 films were deposited over EBM Ti5Al4V substrates using two physical vapor deposition techniques: 1) magnetron sputtering, and 2) cathodic arc and glow-discharge methods. When immersed for 7 and 14 days in SBF at static conditions (37±0.05 °C, pH 7.4), Ca/P ratio of the apatite deposits increased from approximately 1.5 up to near stoichiometric (1.67), respectively. After the initial decrease, the pH of the solution during soaking increased gradually reaching values close to 7.7 for both coatings. However, the weight gain of the samples with Arc coatings after the immersion period in SBF was nearly three times more than those with magnetron deposited coating. The electrochemical potentiodynamic tests performed in SBF indicated a shift in the corrosion potentials towards nobler direction after 7 and 14 days of immersion compared to non-immersed samples, whereas the corrosion current density was slightly increased.

Comparison of the Corrosion Behaviour of Differently Deposited PVD TiN/TiO2 Coatings on Electron Beam Modified Ti5Al4V Alloy

In the particular study, the micropatterning of the Ti5Al4V alloy in as-received, solution treated and solution and precipitated condition was done using electron beam surface modification (EBSM) by scanning electron beam. The nanostructured TiN/TiO2 films were deposited over the EBSM Ti5Al4V substrates using dc magnetron sputtering and cathodic arc and glow-discharge methods. The electrochemical potentiodynamic tests were performed in Ringer saline at 37±0.05 °C and a pH of 5.7 in order to determine the corrosion resistance behavior of the coated and uncoated EBSM substrates as compared with the bare as-received, solution treated and solution and precipitated samples. The presented results gave an idea of the corrosion behavior of the examined implant systems in aggressive environment and external conditions close to the body right.

2123 A clinically relevant rabbit surgical model of pelvic reconstruction to evaluate the immune response to novel surgical materials

OBJECTIVES/SPECIFIC AIMS: Pelvic organ prolapse, a disorder in which the muscles of the pelvic floor are weakened over time, affects over a million women each year in the United States. A quarter of these women undergo a reconstructive procedure, increasingly using polypropylene mesh as mechanical reinforcement to the pelvic floor. However, the number of complications such as chronic pain and mesh erosion/exposure in women with vaginal mesh implants were reported at rates as high as 10%–20%. This indicates a limited understanding of the host response to mesh in vaginal tissue and strategies to reduce these complications. Utilizing a novel surgical technique in New Zealand white rabbits, we implant mesh analogously to human implantation and evaluate changes in the immunologic response at early (14 d) and tissue remodeling outcomes at late stages (90 and 180 d) of implantation. The mesh-tissue complex was removed from each rabbit and processed for histological staining as well as immunolabeling of immune cells, such as macrophages. Extracellular matrix protease assays and mechanical integrity of the tissue also evaluate the overall inflammatory response associated with each implant. METHODS/STUDY POPULATION: Commercially available polypropylene mesh was used to investigate the modulation of the immune response. An adapted radio frequency glow discharge method is used to create a stable negative charge on the surface of the mesh, followed by the sequential deposition of polycationic and polyanionic polymers to provide a stable, conformal, nanoscale coating. It is well known macrophages are characterized on a spectrum ranging from a proinflammatory M1 phenotype to an M2 anti-inflammatory phenotype. Interleukin-4, an immunomodulatory cytokine known to promote the M2 phenotype, is incorporated into the coating to be released in a controlled manner upon implantation. Utilizing a novel surgical technique in New Zealand white rabbits, we implant mesh using the “gold standard” abdominal sacrocolpopexy procedure and evaluate changes in the immunologic response at early (14 d) and tissue remodeling outcomes at late stages (90 and 180 d) of implantation. The procedure begins with an initial hysterectomy removing the uterus followed by creating space along the vaginal wall on both sides between the bladder and the rectum. Two 3×10 cm2 pieces of mesh are secured along both sides of the vaginal wall. The remaining flaps at the top are then secured to a ligament in the sacral/lumbar space, creating the support to the pelvic organs. Upon closing the incision, a partial thickness defect is made in the abdominal wall, and mesh is implanted inside to repair the abdominal muscle. Both of these implantations of mesh allow for the assessment of the immune response in the pelvic area (relevant for prolapse patients) and in the abdominal area (relevant for translation from hernia repair).The mesh-tissue complex was removed from each rabbit and processed for histological staining as well as immunolabeling of immune cells, such as macrophages. Extracellular matrix protease assays and mechanical integrity of the tissue also evaluate the overall inflammatory response associated with each implant. RESULTS/ANTICIPATED RESULTS: The results of this study show that implants into vaginal tissues elicited an increased host inflammatory response at 14 days as compared with those in the abdominal wall. However, at chronic time points the inflammatory response in the vagina was reduced as compared to that in the abdominal cavity. The present study also demonstrates the scale-up of a previous methodology for a nanoscale coating. We present a nanometer thickness, tunable, and uniform coating capable of releasing bioactive interleukin-4. We evaluated the biological functionality of the coated mesh via bioactivity studies and in vivo implantation. An ideal mesh would provide mechanical support to the pelvic floor while decreasing the inflammatory response and increasing integration with the surrounding native tissue. DISCUSSION/SIGNIFICANCE OF IMPACT: We developed an in vivo model clinically relevant to understanding the early host response to mesh in an anatomically relevant area, the vaginal microenvironment. Previous studies have been conducted in a rodent abdominal defect model while other work has been done in a nonhuman primate vaginal model, but the host response is only observed at later time points (>3 mo). Thus, we developed a rabbit model to investigate early responses and a novel coating to actively working towards improved tissue integration.

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Evaluation of the stiffness and friction of Ti6Al4V ELI treated by glow discharge nitriding

In this study, an evaluation of the elastic-plastic surface hardening on Ti6Al4V ELI titanium nitride films obtained by glow discharge method was carried out by nanoindentation tests according to the standard ISO 14577. The nanotribological properties (metal-metal) were also evaluated using the pin-on-disc system Ti6Al4V surface deposition ELI with nitrogen, obtaining a correlation between the coefficient of friction of Ti6Al4V ELI treated by PVD and the Young's modulus of the respective substrate modified by PVD. To characterize the substrate for the characterization tests, scanning electron microscopy, atomic force microscopy and X-ray diffraction and contact angle were carried out. The results demonstrated that the substrates nitrided improved mechanical and tribological properties, hardness, Young's modulus and coefficient of friction, making the alloy Ti6Al4V ELI support axial loads in tension and compression.

Surface modification of austenitic steel by various glow-discharge nitriding methods

Recent years have seen intensive research on modifying glow-discharge nitriding processes. One of the most commonly used glow-discharge methods includes cathodic potential nitriding (conventional method), and active screen plasma nitriding. Each of these methods has a number of advantages. One very important, common feature of these techniques is full control of the microstructure, chemical and phase composition, thickness and the surface topography of the layers formed. Another advantage includes the possibility of nitriding such materials as: austenitic steels or nickel alloys, i.e. metallic materials which do not diffuse nitrogen as effectively as ferritic or martensitic steels. However, these methods have some disadvantages as well. In the case of conventional plasma nitriding, engineers have to deal with the edge effect, which makes it difficult to use this method for complexly shaped components. In turn, in the case of active screen plasma nitriding, the problem disappears. A uniform, smooth layer forms, but is thinner, softer and is not as resistant to friction compared to layers formed using the conventional method. Research is also underway to combine these methods, i.e. use an active screen in conventional plasma nitriding at cathodic potential. However, there is a lack of comprehensive data presenting a comparison between these three nitriding processes and the impact of pulsating current on the formation of the microstructure and functional properties of austenitic steel surfaces. The article presents a characterisation of nitrided layers produced on austenitic X2CrNiMo17-12-2 (AISI 316L) stainless steel in the course of glow-discharge nitriding at cathodic potential, at plasma potential and at cathodic potential incorporating an active screen. All processes were carried out at 440 °C under DC glow-discharge conditions and in 100 kHz frequency pulsating current. The layers were examined in terms of their microstructure, phase and chemical composition, morphology, surface roughness, hardness, wear and corrosion resistance. Studies have shown a strong influence of the type of nitriding method used and of the electrical conditions on the microstructure and properties of the diffusion layers formed.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7404

Impurity reduction in a plasma by using the deuterium and helium glow discharge method

To reduce the levels of impurities such as water, oxygen and nitrogen in a plasma chamber, we evaporated and deposited carborane (C2B10H12) powders on a silicon substrate by using a glow discharge method, and investigated the effects of boronization as functions of the carborane temperature and the rates of the flowing gases between deuterium and helium. The reduced amount of impurities after boronization was estimated by measuring the partial pressures of the corresponding gases in the chamber and the concentrations of nitrogen and oxygen in a deposited carborane film. The ratio of deuterium to hydrogen in the deposited film was analyzed by using secondary ion mass spectrometry (SIMS). When carborane powders were evaporated under a deuterium atmosphere, the residual gas analyzer showed a significant decrease in the partial pressure of water while less change was noted from the partial pressures of nitrogen and oxygen. The most efficient removal rate for water was obtained when carborane powder was flown under deuterium atmosphere at 150 °C. The SIMS data showed higher concentrations of nitrogen and oxygen in the carborane films deposited on Si substrates under a deuterium atmosphere, demonstrating that boronization under a deuterium atmosphere is an effective method to remove impurities.

Chemical Etching and Patterning of Copper, Silver, and Gold Films at Low Temperatures

Copper, silver, and gold share unique properties that offer numerous application possibilities. For instance, low resistivity and high electromigration resistance make them attractive as interconnect layers in integrated circuits and microelectronic devices, while the optical properties of their nano-scale structures allow fabrication of plasmonic devices. Etching or patterning techniques are required in order to fabricate nano-structures, devices, and circuits. Although liquid or vapor phase techniques can be applied, plasma or glow discharge methods are typically invoked due to the need to generate anisotropic nanometer pattern sizes. Group 11 metals (Cu, Ag, and Au) form few volatile compounds at temperatures below 150°C, which limits the approaches that can be used to perform etching/patterning. Halogenated plasmas are widely used to etch metal layers; however, the low volatility of Cu, Ag, and Au halides precludes low temperature processes. Group 11 metals form hydrides readily in plasmas containing hydrogen species. Despite the thermodynamic instability of these metal hydrides, they appear to form at low (below room) temperature and can be desorbed from the etching surface by ion- or photon-assisted processes. Similarly, methylated metal etch products can be generated with hydrocarbon etching plasmas. As a result, etch rates above 12 ± 1 nm/min can be achieved, even when polymer forming plasmas (e.g., methane or other hydrocarbons) are used for patterning. These simple subtractive plasma etching approaches offer significant advantages relative to other vapor phase or liquid techniques in the manufacture of nano-scale devices and circuits.

Surface-modified bacterial nanofibrillar PHB scaffolds for bladder tissue repair

The aim of the study is in vitro investigation of the feasibility of surface-modified bacterial nanofibrous poly [(R)-3-hydroxybutyrate] (PHB) graft for bladder reconstruction. In this study, the surface of electrospun bacterial PHB was modified with PEG- or EDA via radio frequency glow discharge method. After plasma modification, contact angle of EDA-modified PHB scaffolds decreased from 110 ± 1.50 to 23 ± 0.5 degree. Interestingly, less calcium oxalate stone deposition was observed on modified PHB scaffolds compared to that of non-modified group. Results of this study show that surface-modified scaffolds not only inhibited calcium oxalate growth but also enhanced the uroepithelial cell viability and proliferation.

Paper spray ionization for ambient inorganic analysis

The feasibility of using paper spray ionization as an ambient ionization method for inorganic analysis was investigated. Aqueous solutions were spotted onto paper triangles and high voltage was applied to induce electrospray. In-source collision-induced dissociation assisted in breaking up clusters to produce mass spectra dominated by atomic ions and their corresponding oxides and hydroxides and high-resolution exact mass measurements were used to identify atomic ions in the presence of organic interferences. A feasibility test with a standard inductively coupled plasma mass spectrometry (ICP-MS) test mixture demonstrated detection of 21 of 23 elements as M(+•) or [M + OH](+). The two undetected elements (boron and lithium) were below the minimum detectable m/z setting for the time-of-flight mass spectrometer used for these experiments. Untreated filter paper showed residual contamination from group I and group II elements. Excellent linearity was observed over the concentration range 0.1-1000 ppm for nickel(II) nitrate solutions containing 10 ppm cobalt(II) nitrate as internal standard. The method was applied to the analysis of lead-free solder, a bismuth subsalicylate tablet, permanent magnet materials and lead chromate pigment in a three-cent US postage stamp issued in 1948. Paper spray ionization was successfully applied to qualitative inorganic analysis. Quantitative analysis was shown to be possible with the use of internal standards. Initial detection limits were much higher than for comparable inductively coupled plasma and glow discharge methods, ranging from the high parts-per-billion range to the low parts-per-million range. The detection limits for some elements were limited at low levels by the presence of interferences that were not separated by the resolving power of the mass spectrometer. Despite these limitations, the simplicity and potential portability of paper spray may find some applications for elemental analysis.

Highly-branched vertically-oriented graphene nanosheets with dense open graphitic edge planes as Pt support for methanol oxidation

Vertically-oriented graphene (VG) with predominantly edge plane structure is considered as a promising catalyst support candidate for the methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFCs). Inspired by the fact that catalyst nanoparticles are spontaneously attached to the exposed graphene edges, a novel highly-branched vertically-oriented graphene (HBVG) based catalyst support is proposed in the current work. With employing atmospheric normal glow discharge (ANGD) and microwave plasma-enhanced chemical vapor deposition (PECVD) methods, HBVG and maze-like VG (MVG) are synthesized on the surface of carbon paper (CP), respectively. Pt nanoparticles are deposited on pristine CP, HBVG-CP, and MVG-CP with the same route of repeated double-potential pulse electrodeposition (RDPE). Experimental results show that HBVG-CP with dense open graphitic edge planes can desirably provide a considerable number of nuclei sites for the fast nucleation and well dispersion of Pt nanoparticles. Meanwhile, a certain amount of oxygen-containing functional groups on the HBVG surface will benefit the rapid removal of CO and accumulated carbonaceous species. Based on the electrochemical measurements on Pt utilization efficiency, catalytic activity, CO tolerance, and long-term stability, Pt/HBVG-CP is demonstrated to be able to present enhanced catalytic performance over the Pt/CP and Pt/MVG-CP counterparts, holding a great potential for fuel cell applications.

Studies on Formation of Carborane Film Prepared by Using a Deuterium Glow Discharge Method

Carborane powders (C2B10H12) were deposited on silicon substrates and the physical properties of the films were investigated as functions of the distance of the sample from the electrode, the carborane mass, and the plasma-pulse. To obtain the optimum thickness of the films, three silicon substrates were positioned at 6.5, 16.5, and 36.5 cm from the electrode, and the thickness of the samples was analyzed by using XRD, TEM, and SEM. For the deposition, the carborane powder was warmed to 80 degrees C in 10 minutes and was applied a DC-power pulse of 900 W (150 volts, 6 amps) for 2 hours. The mass of carborane and the on-time sequence were varied during the deposition. The combined results of XRD and TEM studies revealed that the structure of the deposited film is an amorphous phase. A careful analysis of the SEM images show that the thickness of the carborane films increased as increasing the mass of the flown carborane while it remained constant when a plasma-pulse time was varied. The thickest film of 353 A was achieved from the samples placed closest to the carborane inlet and the thickness became thinner as farther from the source suggesting that the density of the evaporated carborane powder in a chamber decreased as increasing the distance of the sample from the carborane inlet.