Microstructure and composition of catalytic layers formed by the ion-beam-assisted deposition of platinum onto carbon substrates

The results of investigating the microstructure and composition of layers formed by platinum deposition onto carbon carriers used as electrocatalysts—MG-1 graphite, SU-2000 glassy carbon, and AVCarb® P50 carbon fiber paper—are presented. The layers have been created via the ion-beam-assisted deposition of platinum, in which metal deposition and mixing between the deposited layer and substrate-surface atoms accelerated by ions of the same metal (U = 10 kV) occur, respectively, from a neutral vapor fraction and the vacuum-arc discharge plasma of a pulsed ion source. The layers are examined via scanning electron microscopy, electron probe microanalysis, electron backscatter diffraction, Rutherford backscattering spectrometry, and X-ray photoelectron spectrometry. The formed layers (their thicknesses are ～100 nm and the platinum content is ～10¹⁶ atom cm^?2) are characterized by an amorphous atomic structure that repeats the surface microstructure of the carbon carrier.     

Investigation of the composition and properties of catalytic layers prepared by the ion beam-assisted deposition of tin and platinum on carbon supports

Catalytic layers are prepared by the vacuum ion-beam-assisted deposition of tin and platinum onto carbon-based AVCarb® Carbon Fiber Paper P50 and Toray Carbon Fiber Paper TGP-H-060 T supports to produce electrocatalysts for direct methanol and ethanol fuel cells with a polymer-membrane electrolyte. The layers are formed in the mode of ion-assisted deposition, wherein ions of the deposited metal are used as ions assisting deposition. Metal deposition is performed from a neutral vapor fraction, while mixing of the deposited layer with the substrate by accelerated ions of the same metal is carried out from the vacuum arc discharge plasma of a pulsed electric arc ion source. The morphology and composition of the layers is studied using scanning electron microscopy, electron probe microanalysis, X-ray fluorescence analysis, and Rutherford backscattering spectrometry. It is demonstrated by means of voltammetric measurements that the resulting electrocatalysts exhibit activity in the oxidation of methanol and ethanol.     

Ion-beam formation of electrocatalysts for fuel cells with polymer membrane electrolyte

Active layers of electrocatalysts are prepared by the ion-beam assisted deposition (IBAD) of platinum onto carbon-based AVCarb® Carbon Fiber Paper P50 and Toray Carbon Fiber Paper TGP-H-060 T supports and Nafion® N 115 polymer membrane electrolyte in the mode where the deposited metal ions are used as ions assisting the deposition process. Metal deposition and mixing of the deposited layer with the substrate under an accelerating voltage of 10 kV by the same metal ions are carried out from a neutral fraction of metal vapor and the ionized plasma of a pulsed vacuum-arc discharge, respectively. The composition and microstructure of the surface layers obtained are studied by Rutherford backscattering spectrometry (RBS), scanning electron microscopy (SEM), electron-probe microanalysis (EPMA), and X-ray fluorescence (XRF) analysis. The platinum concentration in the layers is (0.5–1.5) × 10¹⁶ at/cm². The prepared electrocatalysts exhibit activity in the process of the electrochemical oxidation of methanol and ethanol, which form the basis for the principle of operation of low temperature fuel cells (direct methanol fuel cells (DMFC) and direct ethanol fuel cells (DEFC)).     

Composition and electrocatalytic properties of the coatings formed by the ion-beam-assisted deposition of platinum from a pulsed arc-discharge plasma onto aluminum

The structure, composition, and electrocatalytic properties of the coatings formed on aluminum by ion-beam-assisted deposition of platinum from the plasma of a pulsed arc discharge under conditions where deposited-metal ions are used as deposition-assisting ions are studied. The coating thickness reaches ~30 nm, and the near-surface content of platinum atoms in the coatings is ~2.6 × 10¹⁶ cm^-2. The electrocatalytic activities of aluminum-based electrodes with the coatings in the reactions of electrochemical oxidation of methanol and ethanol, which form the basis for the principle of operation of low-temperature fuel cells (considered as promising chemical sources of an electric current), are significantly higher than the activity of a platinum electrode.     

电弧增材成形中熔积层表面形貌对电弧形态影响的仿真

电弧增材成形常采用单道多层或多道搭接的熔积方式,不同的熔积方式下对应的熔积层表面形貌不同,从而影响电弧的形态及其传热传质过程.本文建立了纯氩保护电弧增材成形的电弧磁流体动力学三维数值模型,以及不同表面形貌的熔积层模型,并在保持阳极与阴极之间距离和熔积电流不变的条件下,通过模拟计算获得增材成形特有的单道和多道搭接熔积条件下的不同表面形貌对应的电弧形态以及相应的温度场、流场、电流密度、电磁力、电弧压力分布.数值模拟结果表明:平面基板上起弧情况下电弧中心具有较高的温度、速度、电流密度以及压强;单道多层熔积情况下熔积层数对电弧的各个参量影响较小;多道搭接熔积情况下电弧呈非对称分布,电弧中心温度较前两者低,电流密度、电磁力和电弧压强的分布偏向熔积层一侧.     

沉积温度对钛硅共掺杂类金刚石薄膜生长、结构和力学性能的影响

采用中频磁控溅射Ti80Si20复合靶在单晶硅表面制备了共掺杂的类金刚石薄膜.研究了沉积温度对薄膜生长速率、化学成分、结构、表面性质和力学性能的影响.结果表明:随沉积温度升高,薄膜生长速率降低,薄膜Ti和Si原子浓度增加,C原子浓度降低;在高温下沉积的薄膜具有低sp3C含量、低表面接触角、低内应力和高的硬度与弹性模量.基于亚表层注入生长模型分析了沉积温度对薄膜生长和键合结构的影响,从薄膜生长机制和微观结构解释了表面性质和力学性能的变化.     

Improvement of hot-dip zinc coating by enriching the inner layers with iron oxide

The performance of hot-dip galvanic coating formed on steel not only depends on the alloy composition of the superficial layer but also significantly, on the composition of the inner alloy layers at the coating/substrate interface. Further, the presence of barrier oxide layers, if any can also improve the performance of galvanic coating. In the present work, the effect of inner iron oxide barrier layer formed prior to hot-dip galvanization was investigated. A continuous and adherent iron oxide layer was formed on steel by anodic oxidation of the steel substrate. Although the wettability of oxide surface by liquid zinc was initially poor, the increase in dipping time and the transition of the oxide layer to unstable form due to the presence of Cl⁻ ion in the flux facilitated localized growth of Fe-Zn alloy phases. The inhibitive nature of the oxide layer was temporary, since the presence of Cl⁻ induces micro cracks on the oxide surface thereby facilitating better zinc diffusion. The modification of the substrate structure during galvanization was found to influence the galvanizing process significantly. The present study predicts scope for application of this process for protection of rusted steel specimens too.     

Determination of the element distribution in films deposited using the plasma focus facility by Rutherford backscattering

The C, Cu and W element profiles in films deposited using a plasma focus facility are studied by the Rutherford backscattering of 2-MeV He⁺ ions. The films are deposited onto glass substrates in Ar plasmaforming gas. The element profiles are found to depend significantly on the kinetic energy of particles. The penetration depth of particles with the velocity ~10⁵ m/s is about 1.5 μm. The corresponding element profiles showing the distribution of elements over the thickness of the glass are non-linear. For each element, the maximum layer depth is observed under the glass surface. The formation of Cu, W and C layers under the glass surface and their overlapping is a feature of films deposited using the plasma focus facility. Such an arrangement of layers evidences the significant difference between this method of film deposition and conventional techniques at low rates of atom deposition, as well as diffusion-based methods. The obtained films are found to have dielectric properties.     

The role of the spray pyrolysed Al<Subscript>2</Subscript>O<Subscript>3</Subscript> barrier layer in achieving high efficiency solar cells on flexible steel substrates

Thin film chalcopyrite solar cells grown on light-weight, flexible steel substrates are poised to enter the photovoltaic market. To guarantee good solar cell performance, the diffusion of iron from the steel into the CIGSe absorber material must be hindered during layer deposition. A barrier layer is thus required to isolate the solar module from the metal substrate, both electronically and chemically. Ideally the barrier layer would be deposited by a cheap roll-to-roll process suitable to coat flexible steel substrates. Aluminium oxide deposited by spray pyrolysis matches the criteria. The coating is homogeneous over rough substrates allowing comparatively thin barrier layers to be utilized. In this article, solar cell results are presented contrasting the device performance made with a barrier layer to that without a barrier layer. Secondary Ion Mass spectrometry (SIMS) measurements show that the spray pyrolysed barrier layer diminishes iron diffusion to the chalcopyrite absorber layer. The role of sodium, imperative for the growth of high efficiency chalcopyrite solar cells, and how it interacts with Al₂O₃ is discussed.     

Electron-beam modification of a surface layer deposited on low-carbon steel by means of arc spraying

State-of-the-art means of physical materials science are used to study the structure, phase composition, defect substructure, and tribological properties of a coating formed on low-carbon Hardox 450 martensite steel via the electrocontact deposition of an Fe–C–Ni–B wire and modified through subsequent irradiation with high-intensity pulsed electron beams. It is shown that electron-beam treatment results in the formation of a modified 50-μm thick surface layer, the main phases of which are the α-phase, iron boride FeB, and boron carbide B₄C. In the layer modified by electron-beam treatment, the transverse size of batch martensite crystals is reduced by a factor of 3, relative to the initial Hardox 450 steel, and ranges from 50 to 70 nm. It is established that the wear resistance of the deposited layer after electron-beam treatment grows by more than 20 times with respect to the wear resistance of Hardox 450 steel, and the friction coefficient is reduced by a factor of 3.5. The microhardness of a deposited layer ~7 mm thick is more than double that of the base metal.     

Effects of laser power density on the microstructure and microhardness of Ni–Al alloyed layer by pulsed laser irradiation

Laser alloying of Ni–P electroless deposited layer with aluminum substrate was carried out by Nd–YAG pulsed laser. The phase composition and microstructure of the alloyed layers produced by different laser power densities were identified by X-ray diffractionary (XRD), scanning electron microscope (SEM) accompanied by energy dispersion X-ray analysis (EDS) and transmission electron microscope (TEM). Furthermore, the surface roughness of the alloyed layers was characterised by confocal laser scanning microscope (CLSM). The results showed that the characteristic dendritic or lamellar microstructures were observed in the alloyed layers. The phase constituents of the alloyed zones were intermetallic compounds of nickel–aluminum NiAl, Al₃Ni and Al₃Ni₂, as well as some non-equilibrium phases and amorphous phases depending on the employed laser power density. As a result, the microhardness of the alloyed layer with Ni–P amorphous phases formed at laser power density 5.36×10⁹ W/m² reached to HV_0.1 390.     

Surface and interface properties of thin pentacene and parylene layers

To improve Organic Thin Film Transistor (OTFT) properties we study OTFT semiconductor/dielectric interfacial properties via examination of the gate dielectric using thin Parylene C layer. Structural and morphology properties of pentacene layers deposited on parylene layer and SiO₂/Si substrate structure were compared. The surface morphology was investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM topography of pentacene layer in non-contact mode confirmed the preferable pentacene grain formation on parylene surface in dependence on layer thickness. The distribution of chemical species on the surfaces and composition depth profiles were measured by secondary ion mass spectroscopy (SIMS) and surface imaging. The depth profiles of the analyzed structures show a homogenous pentacene layer, characterized with C or C₂ ions. Relatively sharp interface between pentacene and parylene layers was estimated by characteristic increased intensity of CCl ions peak. For revealing the pentacene phases in the structures the Micro-Raman spectroscopy was utilized. Conformal coatings of parylene and pentacene layers without pinholes resulted from the deposition process as was confirmed by SIMS surface imaging. For the pentacene layers thicker than 20 nm, both thin and bulk pentacene phases were detected by Micro-Raman spectroscopy, while for the pentacene layer thickness of 5 and 10 nm the preferable thin phase was detected. The complete characterisation of pentacene layers deposited on SiO₂ and parylene surface revealed that the formation of large grains suggests 3D pentacene growth at parylene layer with small voids between grains and more than one monolayer step growth. The results will be utilized for optimization of the deposition process.      

Ion-beam formation of the active surface of methanol oxidation electrocatalysts on the tantalum substrates

The active surfaces of electrocatalysts are formed by the ion-beam-assisted deposition of one of the rare-earth metals and platinum onto tantalum substrates from a neutral vapor fraction and the vacuum-arc discharge plasma of a pulsed ion source. Deposited metal ions are used as agents to aid deposition. The composition and microstructure of the formed surface layers are investigated via scanning electron microscopy, electron probe microanalysis, electron backscatter diffraction, and Rutherford backscattering spectrometry. Electrocatalytic activity in the electrochemical oxidation of methanol, which underlies the operation of low-temperature fuel cells, is investigated via cyclic voltamperometry.     

X-ray spectral analysis of the interface of a thin Al<Subscript>2</Subscript>O<Subscript>3</Subscript> film prepared on silicon by atomic layer deposition

The extent and phase chemical composition of the interface forming under atomic layer deposition (ALD) of a 6-nm-thick Al₂O₃ film on the surface of crystalline silicon (c-Si) has been studied by depthresolved, ultrasoft x-ray emission spectroscopy. ALD is shown to produce a layer of mixed Al₂O₃ and SiO₂ oxides about 6–8 nm thick, in which silicon dioxide is present even on the sample surface and its concentration increases as one approaches the interface with the substrate. It is assumed that such a complex structure of the layer is the result of interdiffusion of oxygen into the layer and of silicon from the substrate to the surface over grain boundaries of polycrystalline Al₂O₃, followed by silicon oxidation. Neither the formation of clusters of metallic aluminum near the boundary with c-Si nor aluminum diffusion into the substrate was revealed. It was established that ALD-deposited Al₂O₃ layers with a thickness up to 60 nm have similar structure.     

Hydrophobic properties of carbon fabric with Teflon AF 2400 fluoropolymer coating deposited from solutions in supercritical carbon dioxide

A method for uniform deposition of a hydrophobizing polymer from a solution in supercritical carbon dioxide (SC-CO₂) onto the surface of carbon fabric used for manufacturing gas diffusion layers of fuel cells is developed. This approach, based on using Teflon AF 2400, a SC-CO₂-soluble copolymer, is compared to the traditional method for hydrophobization of the gas diffusion layer of a fuel cell, based on the use of an aqueous dispersion of Teflon 30N. Hydrophobizing polymers were deposited on the surface of a highly rough carbon fabric (Saati), an electrically conductive gas diffusion layer material with good mechanical and resource characteristics. In one of the versions of the method of deposition from SC-CO₂, the hydrophobic film was subjected to additional annealing at a temperature above the glass transition temperature of Teflon AF 2400 amorphous copolymer. It is shown that this approach makes it possible to form a uniform thin fluoropolymer film on carbon fibers, which imparts the most stable superhydrophobic properties to the surface of the gas diffusion layer at very low amounts of deposited polymer. In this case, the contact angle reaches a value much greater than that previously reported in the literature for similar methods. Prolonged immersion in water (for 1000 h) or wash in the presence of detergent does not impair the superhydrophobicity of the gas diffusion layer. The developed gas-diffusion layer was used to prepare an electrode for phosphoric fuel cell, the current-voltage characteristic of which indicates a satisfactory performance. The results obtained show that adopted approach is promising for developing gas diffusion layers for fuel cell electrodes.     

Morphologies,microstructures, and mechanical properties of samples produced using laser metal deposition with 316 L stainless steel wire

Laser metal deposition (LMD) with a filler has been demonstrated to be an effective method for additive manufacturing because of its high material deposition efficiency, improved surface quality, reduced material wastage, and cleaner process environment without metal dust pollution. In this study, single beads and samples with ten layers were successfully deposited on a 316 L stainless steel surface under optimized conditions using a 4000 W continuous wave fibre laser and an arc welding machine. The results showed that satisfactory layered samples with a large deposition height and smooth side surface could be achieved under appropriate parameters. The uniform structures had fine cellular and network austenite grains with good metallurgical bonding between layers, showing an austenite solidification mode. Precipitated ferrite at the grain boundaries showed a subgrain structure with fine uniform grain size. A higher microhardness (205–226 HV) was detected in the middle of the deposition area, while the tensile strength of the 50 layer sample reached 669 MPa. In addition, ductile fracturing was proven by the emergence of obvious dimples at the fracture surface.     

Artifacts in the sputtering of inorganics by C60

In the present study, the basic issues in C₆₀ⁿ⁺ sputtering are studied using silicon, gold and platinum samples. Sputtering yields are measured for energies in the range of 5-30 keV, by sputtering micrometre sized craters on the surface of flat clean samples and measuring their volumes using atomic force microscopy (AFM). Net deposition of carbon occurs for all three materials at 5 keV, and is not specific to silicon which forms a carbide. The threshold energy for net sputtering is dependent on the sputtering yield and the stopping power of the substrate. Away from the threshold, the sputtering yields agree well with Sigmund and Claussen's thermal spike model after allowance for the sputtering of the deposited carbon atoms. AFM images show the formation of unusual surface topography around the transition region between sputtering and deposition. Analysis of the bottom of a crater using imaging SIMS shows a significant enhancement of carbon clusters as well as various silicon-carbon groups, indicating the importance of carbon deposition and implantation in a gradual mixed layer formed from sputtering. The thickness of this interface layer is shown to be approximately 5 nm.     

Substrate effects on the microstructure of hydrogenated amorphous carbon films

In this work, plasma enhanced chemical vapour deposition was used to prepare hydrogenated amorphous carbon films (a-C:H) on different substrates over a wide range of thickness. In order to observe clear substrate effect the films were produced under identical growth conditions. Raman and near edge X-ray absorption fine structure (NEXAFS) spectroscopies were employed to probe the chemical bonding of the films. For the films deposited on silicon substrates, the Raman I_D/I_G ratio and G-peak positions were constant for most thickness. For metallic and polymeric substrates, these parameters increased with film thickness, suggesting a change from a sp³-bonded hydrogenated structure to a more sp² network, NEXAFS results also indicate a higher sp² content of a-C:H films grown on metals than silicon. The metals, which are poor carbide precursors, gave carbon films with low adhesion, easily delaminated from the substrate. The delamination can be decreased/eliminated by deposition of a thin (∼10 nm) silicon layer on stainless steel substrates prior to a-C:H coatings. Additionally we noted the electrical resistivity decreased with thickness and higher dielectric breakdown strength for a-C:H on silicon substrate.     

Analysis of the composition of Ti-based thin films deposited on silicon by means of self-ion assisted deposition

The composition of Ti-based thin films deposited on silicon using a self-ion assisted deposition (SIAD) method was investigated by utilising the Rutherford backscattering spectrometry technique and RUMP simulation code. The hydrogen affinity of the coatings produced by means of SIAD was investigated using the ¹H(¹⁵N, αγ)¹²C nuclear resonance reaction. The titanium–based films on silicon were found to have a high content of oxygen, carbon, hydrogen and substantial concentration of the substrate. Near 10% H content enrichment was found at the surface of coatings but no hydrogen enrichment at the coating–substrate interfaces was observed.     

Investigation of the Structure and Functional Properties of Diamond-Like Coatings Obtained by Physical Vapor Deposition

Diamond-like coatings with a total thickness of ~0.6 μm are obtained by physical vapor deposition with plasma separation and a pulsed carbon arc source with a cooled cathode and laser arc ignition; the substrates are titanium alloy (VT4), stainless steel (12Cr18N10T), and copper (M1). Scanning electron microscopy and profilometry are used to study the coatings surface and structure. The composition of the coatings and the fraction of sp³ bonds are studied using Raman spectroscopy. A wide peak in the 1580 cm^-1 region is observed characteristic of diamond-like coatings. The coatings have a dense, nonporous structure. The tribological properties of the coatings are evaluated by the ball-on-disk method using a friction pair with WC and technical diamond. The strength characteristics are determined using linear scratch testing and nanoindentation measurements. The strength characteristics of the coatings vary and depend on the substrate materials. The friction coefficient of a diamond-like coating on VT4 alloy is ~0.1 in a friction pair with WC and ~0.01 with technical diamond.