Double Glow Discharge Plasma Technique Research Articles

Nanocrystalline TaCN coated titanium bipolar plate dedicated to proton exchange membrane fuel cell

To promote the corrosion resistance and surface conductivity of metal bipolar plates (BP) in proton exchange membrane fuel cells (PEMFC), a TaCN nanoceramic coating with TaN and TaC dual phase structures was engineered onto a commercially pure titanium substrate employing the double cathode glow discharge plasma (DCGDP) technique. The as-prepared TaCN coating was well-adhered to the substrate with a thickness of ∼16.5 μm. The coating exhibited a microstructure comprising equiaxed grains with an average size of ∼10.3 nm. The electrochemical behavior of the TaCN coating was evaluated in a simulated PEMFC environment containing various HF concentrations. Open circuit potential (OCP), potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), potentiostatic polarization, and Mott-Schottky tests showed that the addition of HF enhanced the corrosion rate of both the Ti substrate and the TaCN coating. Nevertheless, the TaCN coating exhibited improved corrosion potential, lower corrosion current density and larger resistance than that of Ti for all HF concentrations. The Hilbert-Huang and corrosion morphology analysis indicated that the TaCN coating maintained a passive state with increasing HF concentration. First-principle calculations investigated the adsorption capacity of the F− ions on the passive film on the TaCN coating. Furthermore, the TaCN coating possesses desirable interfacial contact resistance (ICR) (about 10 mΩ cm2 under a compressive force of 140 N cm−2) and outstanding hydrophobicity (92.9° ± 2°). Overall, the TaCN coating, which can deliver appreciable enhancement relative to the performance of titanium, represents an extremely competitive candidate as a protective coating for bipolar plates.

A reactive-sputter-deposited TiSiN nanocomposite coating for the protection of metallic bipolar plates in proton exchange membrane fuel cells

To meet the needs of corrosion resistance and electrically conductivity for metallic bipolar plates that are employed in proton exchange membrane fuel cells (PEMFCs), a TiSiN nanocomposite coating was fabricated on to a Ti–6Al–4V substrate using reactive sputter-deposition through the double cathode glow discharge plasma technique. The microstructure of the TiSiN coating comprised nanocrystallite TiN grains embedded in an amorphous Si3N4 matrix. Electrochemical measurements were employed to investigate the corrosion behavior of the TiSiN coating in the simulated operating environments of a PEMFC, specifically 0.5 M H2SO4 solution containing different HF concentrations (namely 2, 4 and 6 ppm) at 70 °C pumped with H2 at the anode and air at the cathode. With increasing HF concentration, a higher corrosion current density and lower corrosion potential were observed from both the coating and the uncoated substrate, indicating that the addition of HF accelerated their corrosion rates under these conditions. Compared to the uncoated substrate, the TiSiN coating showed a markedly higher corrosion resistance at all HF concentrations. The passive film that formed on the TiSiN coating, with a resistance of the order of magnitude of ~107 Ω cm2, displayed good electrochemical stability and was less affected by changes in HF concentration. For the TiSiN coating, the values of interfacial contact resistance (ICR) were 14.7 mΩ cm−2 and 18.3 mΩ cm−2, respectively, before and after 2.5 h potentiostatic polarization with 6 ppm HF under cathodic conditions under a compaction pressure of 140 N cm−2. Both values are much lower than those for the bare substrate. Moreover, the TiSiN coating was shown to improve the hydrophobicity of Ti–6Al–4V that would help facilitate water management in the PEMFC operating environment. This coating, which exhibited excellent corrosion resistance, electro-conductivity and hydrophobicity, is therefore a promising material for protecting metallic bipolar plates from corrosive attack.

Electrochemical Properties of Niobium Coating for Biomedical Application

The preparation of the Nb coating was performed on the bare Ti–6Al–4V alloy using the double glow discharge plasma technique. It was characterized that the Nb coating exhibited a face centered cubic (fcc) crystal structure and a pronounced (200) preferred orientation. The SEM micrograph of the cross section for the coating displayed dense microstructure with a thickness of approximately 18 µm. The critical load (Lc) of the coating was determined to be about 83.5 N by the scratch tests. The electrochemical corrosion resistance of the coating was examined in Ringer’s solution at 37 °C by a series of electrochemical techniques, including open-circuit potential (OCP), potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and a Mott–Schottky analysis. As the result of the potentiodynamic polarization, the Nb coating possessed a more positive corrosion potential and lower corrosion current density than the Ti–6Al–4V substrate. EIS fitting date showed that the Nb coating always possessed a higher value of impedance and lower effective capacitance than those of the substrate during the five days of immersion testing. The main component of the passive film developed on the Nb coating was Nb2O5, confirmed by an X-ray photoelectron spectroscopy (XPS) analysis. A Mott–Schottky analysis demonstrated typical n-type semiconductor characteristics of the Nb coating, and both the donor density and flat band potential of the coating were lower than those of the substrate at all the given formation potential. These investigations demonstrate that the Nb coating can significantly improve the corrosion protection of uncoated Ti–6Al–4V and is thus a promising coating for the surface protection of bioimplants.

Effects of pH value and temperature on the corrosion behavior of a Ta2N nanoceramic coating in simulated polymer electrolyte membrane fuel cell environment

To improve the corrosion resistance and electrical conductivity of Ti-6Al-4V bipolar plates used in polymer electrolyte membrane fuel cells (PEMFCs), a novel electro-conductive Ta2N nanoceramic coating was developed by reactive sputter-deposition using a double cathode glow discharge plasma technique. The microstructure of the coating consisted of fine equiaxed Ta2N grains with an average grain size of ∼13nm, which exhibited a strong (101) preferred orientation. To explore the influence of both pH values and temperatures on the corrosion resistance of the coating, the electrochemical behaviors and electronic properties of passive films grown on the Ta2N coating were systematically investigated using different electrochemical techniques in simulated PEMFC operating environment. It was shown that either increasing the acidity or the temperatures of the solution, the corrosion potential (Ecorr) decreased and the corrosion current density (icorr) increased. At a given temperature or pH value, the Ta2N coating had a higher Ecorr and lower icorr as compared with uncoated Ti-6Al-4V. The results of EIS measurements showed that with increasing temperature or acidity of the solution, the resistance of the passive film (Rp) formed on the Ta2N coating decreased slightly, being of the order of magnitude of 107Ωcm2, which was an order of magnitude higher than that of uncoated Ti-6Al-4V. The interfacial contact resistance (ICR) values were found to increase with increasing pH value or decreasing solution temperature, and the ICR values of the Ta2N coating were markedly lower than that of uncoated Ti-6Al-4V, due to the thinner thickness of passive films. Furthermore, the Ta2N-coated Ti-6Al-4V is more hydrophobic than bare Ti-6A1-4V, which was favorable for both the simplification of water management and improving corrosion resistance in PEMFC operating environment.

Cavitation Erosion Resistance of Sputter-Deposited Cr3Si Film on Stainless Steel

In this technical brief, a Cr3Si nanocrystalline film was deposited on 304 stainless steel (SS) substrate using a double glow discharge plasma technique. The film was characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy, nanohardness tester, and scratch tester. The as-deposited film with a thickness of 5 μm consisted of A15 structured Cr3Si phase with an average grain size of 8 nm. The hardness values of the film were determined to be 26 GPa, which was ten times greater than 304 SS. A self-designed ultrasonic vibration cavitation erosion apparatus was employed to evaluate the cavitation erosion resistance of the Cr3Si film. The results showed that after cavitation tests of 30 hrs, the erosion mass loss of the film was only 60% of that for 304 SS substrate. SEM observation of the erosion surfaces indicated that the surface damage degree of the Cr3Si film is significantly less than that of 304 SS.

Reactive-sputter-deposited β-Ta 2 O 5 and TaON nanoceramic coatings on Ti–6Al–4V alloy against wear and corrosion damage

Abstract In this study, two different types of nanoceramic coatings; namely, β-Ta2O5 and TaON, were synthesized by double glow discharge plasma technique on Ti–6Al–4V alloy to improve its wear and corrosion resistance. The new coatings were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The two coatings were found to have a thickness of about ~ 25 μm and exhibit similar microstructural characteristics, i.e., composed of equiaxed grains with an average grain size of ~ 15 nm. They are tightly adhered to the Ti–6Al–4V substrate. Nanoindentation was used to determine the hardness and elastic modulus of the two coatings and the adhesion strength between the coatings and substrate was also evaluated by scratch testing. Dry sliding wear tests were performed using a ball-on-disk type tribometer, in which the two coatings were slid against Si3N4 ceramic balls under applied loads ranging from 2.3 N to 5.3 N at room temperature. Compared with the Ti–6Al–4V, the coated samples showed a decrease of two orders of magnitude in the specific wear rate, and the specific wear rates of the two coatings were also insensitive to the applied normal loads. The electrochemical behavior of the two coatings was characterized by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and Mott–Schottky analysis in a naturally aerated 5 wt.% HCl solution. While both types of coatings were able to greatly improve the corrosion resistance of Ti–6Al–4V alloy, the TaON coating exhibit a higher corrosion resistance than the β-Ta2O5, due primarily to the TaON coating with a lower carrier density.

Electrochemical Corrosion Behavior of Nanocrystalline β-Ta Coating for Biomedical Applications.

To explore its potential as a highly corrosion-resistant coating for biomedical titanium alloys, a novel β-Ta nanocrystalline coating, composed of equiaxed β-Ta grains with an average grain size ∼22 nm, was deposited onto Ti-6Al-4V substrate using a double glow discharge plasma technique. The newly developed coating exhibited an extremely dense and homogeneous microstructure, exhibiting a strong (002) preferred orientation. The electrochemical behavior and semiconducting properties, such as donor density, flat-band potential, and diffusivity of point defects (Do), of the passive film formed on the β-Ta coating were compared to those for both uncoated Ti-6Al-4V and commercially pure Ta in Ringer's physiological solution at 37 °C, using an array of complementary electrochemical techniques. The results showed that the β-Ta coating not only provided Ti-6Al-4V with good corrosion protection but also endowed a higher resistance to corrosive attack than commercially pure Ta in Ringer's physiological solution at 37 °C. Mott-Schottky analysis revealed that the passive film formed on the β-Ta coating had a lower donor density and flat-band potential than commercially pure Ta. The calculated values of Do for the β-Ta coating (1.45 × 10-16cm2/s) are comparable to that for commercially pure Ta (1.13 × 10-16 cm2/s), both of which are 1 order of magnitude lower than that for uncoated Ti-6Al-4V (2.73 × 10-15 cm2/s). Compared with commercially pure Ta, the higher corrosion resistance of the β-Ta coating results from its nanosized grains and crystallographic orientation, which promotes the rapid formation of a robust passive film with a more compact structure.

Corrosion and wear behaviours of a reactive-sputter-deposited Ta2O5 nanoceramic coating

In order to improve the wear and corrosion resistance of Ti-6Al-4V, a novel β-Ta2O5 nanoceramic coating was synthesised using reactive sputter deposition enabled by double glow discharge plasma technique. The surface topography, chemical composition, and microstructure of the newly developed coating were characterised by a variety of surface analytical techniques. The coating microstructure was found to exhibit a compact striated pattern extending in a direction perpendicular to coating surface, which is composed of equiaxed β-Ta2O5 grains with an average grain size of ∼20nm, well adhered to the Ti-6A1-4V substrate. The hardness and the Young's modulus of the as-deposited coating were obtained by nanoindentation, and the adhesion strength between the coating and substrate was determined by a scratch tester. The dry sliding wear behaviours of the coating were investigated at room temperature against Si3N4 ceramic balls at room temperature under applied loads ranging from 2.3N to 5.3N using a ball-on-disc tribometer. The specific wear rates of the coating exhibited only a slight increase with applied normal load, and were shown to be two orders of magnitude lower than that for Ti-6Al-4V under the same loading condition. Furthermore, the electrochemical behaviour of the coating immersed in 3.5wt.% NaCl solution was systematically examined by using a range of complementary electrochemical techniques including potentiodynamic polarisation, electrochemical impedance spectroscopy (EIS), Mott–Schottky analysis as well as potential of zero charge (PZC). The results showed that the corrosion resistance of the β-Ta2O5 nanoceramic coating was better than that of Ti-6Al-4V alloy in 3.5wt.% NaCl solution. Hence, by possessing higher mechanical properties and good wear and corrosion resistance, the β-Ta2O5 nanoceramic coating is considered to be a promising candidate for protection of engineering components operating under harsh conditions.

Electrochemical Properties of a Novel β-Ta2O5 Nanoceramic Coating Exposed to Simulated Body Solutions.

To enhance the corrosion resistance, biocompatibility and mechanical durability of biomedical titanium alloys, a novel β-Ta2O5 nanoceramic coating was developed using a double glow discharge plasma technique. The surface morphology, phase composition and microstructure of the as-deposited coating were examined by atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The coating exhibits a striated structural pattern along the growth direction, which consists of equiaxed β-Ta2O5 grains, 15-20 nm in diameter in cross-section, showing a strong (001) preferred orientation. The mechanical properties and contact damage resistance of the β-Ta2O5 coating were evaluated by nanoindentation. Additionally, scratch tests were performed to evaluate the adhesion strength between the β-Ta2O5 coating and the Ti-6Al-4V substrate. The β-Ta2O5 coating shows high hardness combined with good resistance to both indentation and scratch damage, thus favoring it for long-term load-bearing application in the human body. Electrochemical behavior of the coating was analyzed in both a 0.9 wt % NaCl solution and Ringer's solution at 37 °C, by various electrochemical analytical techniques, including potentiodynamic polarization, electrochemical impedance spectroscopy, potential of zero charge and Mott-Schottky analysis. Compared with uncoated Ti-6Al-4V and commercially pure tantalum, the β-Ta2O5 coating possesses a more positive Ecorr and lower icorr in both aqueous solutions, which is attributed to the thicker and denser β-Ta2O5 coating that provides more effective protection against corrosive attack. In addition, the β-Ta2O5 coating shows stable impedance behavior over 5 days immersion under both simulated body solutions, corroborated by the capacitance and resistance values extracted from the EIS data. Mott-Schottky analysis reveals that the β-Ta2O5 coating shows n-type semiconductor behavior and its donor density is independent of immersion time in both aqueous solutions. Its donor density is of the order of 1 × 1019 cm-3, which is an order of magnitude less than that of the passive films formed on either commercially pure Ta or uncoated Ti-6Al-4V. Moreover, according to the differences between corrosion potential and potential of zero charge, the β-Ta2O5 coating exhibits a greater propensity to repulse chloride ions than both commercially pure Ta and uncoated Ti-6Al-4V. Therefore, the newly developed coating could be used to protect the surface of biomedical titanium alloys under harsh conditions.

Promoting bone-like apatite formation on titanium alloys through nanocrystalline tantalum nitride coatings.

The study aims to advance the applicability of titanium alloys as bone implant materials by tackling some important aspects of surface robustness and bioactivity. To do so, biologically active Ta-N nanocrystalline coatings were engineered on Ti-6Al-4V alloy substrates by reactive sputter deposition using a double glow discharge plasma technique. The surface morphology, phase composition and structure of the coatings were characterized using atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The newly developed coatings are extremely dense, adherent and composed of a cubic TaN phase and a minor fraction of hexagonal Ta2N phase. The microstructure of Ta-N coatings consists of nanocrystallites of about 15-20 nm in diameter, having a strong TaN(200)-oriented texture. Moreover, the coatings exhibit a uniform nanopillar structure on the surface, critical for the observed bioactivity. Scratching tests were performed to evaluate the adhesion strength between the Ta-N coatings and Ti-6Al-4V alloy substrates. The Ta-N coatings were found to exhibit a high scratch resistance and are thus suitable for load-bearing applications. The apatite-inducing ability of the coatings was evaluated in vitro using a simulated body fluid (SBF) that has almost equal compositions of inorganic ions to human blood plasma. After soaking in the solution for up to 14 days, only a few apatite particulates were observed on the surface of untreated Ti-6Al-4V alloy. By contrast, the surface of the Ta-N coatings was completely covered by a compact, AB-type apatite layer free of micro-cracks. High resolution transmission electron microscopy (HRTEM) observations reveal that after soaking for 14 days, the apatite layer, formed through a biomimetic process, comprises closely packed, needle-shaped apatite crystals of 34.5 ± 12.4 nm in length and 6.0 ± 0.2 nm in width. Moreover, nanotwins were identified in apatite, reminiscent of those found in bone minerals. The negatively-charged surface, combined with a unique surface structure of the Ta-N nanoceramic coatings, is believed to be responsible for the formation of a homogenous, compact bone-like apatite layer. The Ta-N nanoceramic coatings are expected to find applications as an integral part of biomaterials used in bone repair and replacement.

Microstructure and mechanical properties of a Mo-toughened Mo3Si-based in situ nanocomposite

To explore the plasticity of cubic A15-structured Mo3Si, mechanical parameters, including bulk modulus, shear modulus, Young's modulus, Cauchy's pressure and Poisson's ratio are obtained from first-principles calculations. Subsequently, a Mo-toughened Mo3Si-based nanocomposite coating is synthesized in-situ onto a Ti–6Al–4V substrate by a double glow discharge plasma technique. The new coating exhibits a dual-phase microstructure, where a coarser-grained Mo-rich phase is uniformly distributed within a finer-grained Mo3Si matrix. The results show that the incorporation of the “coarser-grained” Mo phase improves both damage resistance and hardness of the monolithic Mo3Si nanocrystalline coating.

Mechanical and corrosion-resistant properties of Ti–Nb–Si–N nanocomposite films prepared by a double glow discharge plasma technique

Two quaternary Ti–Nb–Si–N nanocomposite films, with differing Nb contents, were deposited onto Ti–6Al–4V substrates using a double glow discharge plasma technique. The chemical composition and microstructure of the films were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The Ti–Nb–Si–N films exhibit a typical nanocomposite structure, in which nanocrystalline (Ti,Nb)N grains, ~8nm in diameter, were embedded in an amorphous SiNx matrix. The hardness and elastic modulus of the Ti–Nb–Si–N nanocomposite films were measured by nanoindentation. The electrochemical behavior of the Ti–Nb–Si–N nanocomposite films was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in a 3.5wt% NaCl solution. For comparative purposes, these measurements were also performed on TiN and Ti–Si–N films. The results show that the Ti–Nb–Si–N nanocomposite films exhibit both higher hardness and corrosion resistance than the TiN and TiSiN films, which could be attributed to their nanocomposite structure together with the incorporation of both Nb and Si into the TiN films.

Niobium addition enhancing the corrosion resistance of nanocrystalline Ti5Si3 coating in H2SO4 solution

In this paper, novel Nb-containing Ti5Si3 (i.e., Ti56.2Nb6.3Si37.5 and Ti50.0Nb12.5Si37.5) nanocrystalline coatings were deposited onto Ti–6Al–4V substrates by a double glow discharge plasma technique. The effects of Nb alloying on the electrochemical behavior of the Ti5Si3 nanocrystalline coatings were systematically investigated in a naturally aerated 5wt.% H2SO4 solution, for which various electrochemical techniques, including potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), potentiostatic polarization and Mott–Schottky analysis, were employed. Moreover, to evaluate the corrosion performance of the as-deposited coatings over an extended period, their corrosion resistance was analyzed after 7days’ immersion in a 5wt.% H2SO4 solution by EIS measurements and observations of corroded surface morphologies. The results showed that the Ti62.5−xNbxSi37.5 (x=0, 6.3, 12.5) nanocrystalline coatings exhibit superior corrosion resistance compared with Ti–6Al–4V, and their corrosion resistance is enhanced with increasing Nb content, suggesting that Nb alloying is an effective strategy for improving the corrosion protection ability of the Ti5Si3 nanocrystalline coating. The roles of Nb additions in enhancing the corrosion resistance of the Ti5Si3 nanocrystalline coatings can be summarized as: (a) reducing the residual tensile stresses of the as-deposited coatings and (b) tailoring the composition, compactness and electronic structure of the passive films formed. These findings are expected to broaden the application of Ti5Si3 as a highly corrosion-resistant coating for engineering components operating under aggressive conditions.

Uniting superhardness and damage-tolerance in a nanosandwich-structured Ti–B–N coating

A novel nanosandwich-structured Ti–B–N coating was prepared on a Ti–6Al–4V substrate using a double glow discharge plasma technique. This coating consists of alternating Ti(N,B) nanocrystalline layers, containing nanoscale growth twins, and amorphous TiB2–BN layers. Compared with a monolithic TiB2.06 nanocrystalline coating, the new Ti–B–N coating exhibits a marked increase in both damage resistance and hardness (i.e. ∼55 GPa). The enhanced mechanical properties were found to stem from a combination of nanostructuring and nanotwinning effects.

Unraveling the mechanical and tribological properties of a novel Ti5Si3/TiC nanocomposite coating synthesized by a double glow discharge plasma technique

Abstract A novel Ti 5 Si 3 /TiC nanocomposite coating has been successfully prepared on a Ti–6Al–4V substrate by a double cathode glow discharge technique to address its poor tribological properties. The microstructural features of the Ti 5 Si 3 /TiC nanocomposite coating were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The nanocomposite coating consisted of cauliflower-like Ti 5 Si 3 grains with an average grain size of ~15 nm and TiC nanoparticles having an average grain size of ~15 nm distributed at its boundaries. The mechanical and tribological properties of the Ti 5 Si 3 /TiC nanocomposite coating were compared with those of a monolithic Ti 5 Si 3 nanocrystalline coating. The results clearly showed that the Ti 5 Si 3 /TiC nanocomposite coating exhibited a unique combination of higher fracture toughness and hardness as compared to the monolithic Ti 5 Si 3 nanocrystalline coating, which thus exerted a positive effect on its wear resistance.

Mechanical properties of Cr-alloyed MoSi2-based nanocomposite coatings with a hierarchical structure

Novel Cr-alloyed MoSi2-based nanocomposite coatings were successfully synthesized onto Ti–6Al–4V substrates by a double glow discharge plasma technique. The architecture of the nanocomposite coatings exhibited a hierarchical structure, consisting of equiaxed C40-MoSi2 with a bimodal grain size distribution and strip-shaped Mo5Si3 grains segregated to the boundaries of submicron MoSi2 grains. The results showed that the toughness of the MoSi2-based nanocomposite coatings depended strongly upon their hierarchical structure and the magnitude of compressive residual stresses in the nanocomposite coatings.

The roles of passive layers in regulating the electrochemical behavior of Ti5Si3-based nanocomposite films

A novel TiC–Ti5Si3 nanocomposite film was successfully engineered onto a Ti–6Al–4V substrate using a double glow discharge plasma technique. This type of film exhibits a self-toughened, hierarchical structure, consisting of cauliflower-like Ti5Si3 grains together with TiC nanoparticles distributed at the boundaries. The electrochemical behavior and electronic properties of the passive layers formed on the TiC–Ti5Si3 nanocomposite film were compared to a monolithic Ti5Si3 film and uncoated Ti–6Al–4V in a 3.5 wt% NaCl solution by various electrochemical analytical techniques, including low frequency impedance, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), potentiostatic polarization and Mott–Schottky analysis. The results showed that the corrosion resistance of the TiC–Ti5Si3 nanocomposite film was comparable to that of the monolithic Ti5Si3 film, but was significantly higher than that of uncoated Ti–6Al–4V. The TiC–Ti5Si3 nanocomposite film is thus an attractive candidate for surface protection of components against mechanical and chemical attacks.

Enhanced corrosion-resistance in nanocrystalline MoSi2 films enabled by Cr additions

Nanocrystalline C40-structured (Mo1−xCrx)Si2 films were engineered onto Ti6Al4V substrates by a double glow discharge plasma technique. The electrochemical behavior of the newly developed films in a 3.5wt.% NaCl solution was characterized by electrochemical techniques including open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy. To gain a deeper understanding of the role of Cr alloying in corrosion resistance, both cohesive energy and Mulliken population of the interatomic bonds in C40 (Mo1−xCrx)Si2 were calculated based on the first-principles density-functional theory.

Effect of carbon doping on electrochemical behaviour of nanocrystalline Ti 5Si 3 film in NaCl solution

The nanocrystalline Ti 5Si 3 and Ti 5Si 3C 0.8 films with an average grain size of 15 nm were prepared on Ti–6Al–4V alloy substrate by double glow discharge plasma technique. The electrochemical behaviour of two nanocrystalline films has been characterised by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution. The electronic properties of the passive films were investigated by Mott–Schottky analysis. The results revealed that the calculated donor densities are lower and the space charge region thicker for nanocrystalline Ti 5Si 3C 0.8 film as compared to nanocrystalline Ti 5Si 3 film, suggesting that the passive layer formed is more protective.

A novel synthesis method for large area metallic amorphous/nanocrystal films by the glow-discharge plasma technique

Two large-area metallic amorphous/nanocrystal films were prepared on AZ31 magnesium alloy and pure iron substrates by the double glow-discharge plasma technique. The formation mechanism of the novel amorphous films did not follow the established empirical rules for large glass-forming ability. The amorphous films were composed of binary alloys with a difference in the atomic diameter of alloying constituents of less than 12%, and an amorphous film of pure iron was successfully obtained.