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In this study, Ni50Ti50 powder was coated on the surface of graphite substrate (C) via a plasma spraying process using a radio frequency inductively coupled plasma reactor. The coating was carried out using 12- and 9-kW power under Ar atmosphere. The cross-section of coating layers and the surface were examined with Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectrum (EDX), and X-ray Diffractometer (XRD) analyses and microhardness test. The thickness and quality of the coating increased with the input power. Many pores were detected in the cross-sectional surface areas. Higher input power caused a better coating layer of NiTi alloy. The hardness of the coating layer decreases with higher input power. [ABSTRACT FROM AUTHOR]

A few atomic layers of helium adsorbed on graphite have been attracting much attention as one of the ideal quantum systems in two dimension. Although previous reports on neutron diffraction have shown fundamental structural information in these systems, there still remain many open questions. Here, we propose surface crystal truncation rod (CTR) scatterings using synchrotron radiation X-rays as a promising method to reveal surface and interface structures of helium films on graphite at temperatures below 2 K, based on the preliminary experimental results on a monolayer of 4 He on a thin graphite. Our estimation on heat generation by X-ray irradiations also suggests that CTR scatterings are applicable to even at system temperatures near 100 mK. [ABSTRACT FROM AUTHOR]

This work describes the performance of multilayer Ru–Pt coatings with Ti as the interlayer deposited on graphite substrate for applications in precision glass molding (PGM). Different from the previous evaluations with other kinds of coatings for PGM temperatures below 650 °C, we studied the anti-sticking behavior of the developed coatings by annealing them at 750 °C with aluminosilicate glass coverage in a rough vacuum environment. Glass adhesion was not observed even after 40-hour annealing suggesting the high chemical inertness of the coatings at the high temperature. In addition, the Ru–Pt multilayer coatings exhibited a better anti-sticking property than monolayer (Ru or Pt) coatings. The microstructure, surface morphology, and hardness were further characterized. High-resolution transmission electron microscopy (HRTEM) analysis confirmed the perseverance of layered structure after annealing at 750 °C and the hindrance effect on dislocation motion and diffusion arising from the Ru-Pt interfaces. After long-term annealing, interdiffusion leads to Pt-Ru solid solutions, which further enhance the mechanical performance and stability of the noble metal coatings, beneficial for prolonging the lifespan of PGM molds and the optical quality of molded glass. The high anti-sticking and mechanical performances of the developed coatings were finally confirmed in industrial tests.

In this study, a W–ZrC composite coating was applied on graphite substrate by a novel TIG-aided cladding process. The obtained overlay was uniform exhibiting no crack and discontinuity. In-situ reaction between WC and ZrO 2 powders promoted by the heat of the TIG source resulted in overlay formation. To investigate and compare the effect of TiC and Co addition on composite microstructure and functionality, TiC and Co powders were added to WC powder. The phase formation, microstructure, adhesion, microhardness and toughness of the coating were the targets of the examinations and characterizations. The cross-sectional image of the coatings indicated a desired metallurgical bonding at the clad/substrate interface. The examined microhardness and toughness values of the composite coating with pure WC were 1700 HV and 4.7 MPa m , respectively. These values were 2500 HV and 4 MPa m for the sample containing TiC and Co additives. Extensive formation of solid solution between carbide materials and liquid phase formation by W and Co in the composite coating containing TiC and Co led to enhancement of the mechanical performance of the latter. Meanwhile, the improved resistance of the graphite against the oxidation and ablation is expected in presence of the composite clad layer in contrast to the bare graphite sample. [ABSTRACT FROM AUTHOR]

Silicon (Si) films were deposited on low-cost graphite substrates by the electrochemical reduction of silicon dioxide nanoparticles (nano-SiO2) in calcium chloride (CaCl2), melted at 855 °C. Cyclic voltammetry (CV) was used to analyze the electrochemical reduction mechanism of SiO2 to form Si deposits on the graphite substrate. X-ray diffraction (XRD) along with Raman and photoluminescence (PL) results show that the crystallinity of the electrodeposited Si-films was improved with an increase of the applied reduction potential during the electrochemical process. Scanning electron microscopy (SEM) reveals that the size, shape, and morphology of the Si-layers can be controlled from Si nanowires to the microcrystalline Si particles by controlling the reduction potentials. In addition, the morphology of the obtained Si-layers seems to be correlated with both the substrate materials and particle size of the feed materials. Thus, the difference in the electron transfer rate at substrate/nano-SiO2 interface due to different applied reduction potentials along with the dissolution rate of SiO2 particles during the electrochemical reduction process were found to be crucial in determining the microstructural properties of the Si-films.

[Display omitted] • Evaluation of Ru–Cr coatings for precision glass molding. • Diffusion barrier effect of Ru and non-adherence of developed Cr-oxide scale to glass surfaces. • Formation of columnar structure of the coated layers with preferred crystalline orientation. • Development of a multi-phase field model for quantitative analysis of Cr-oxide growth during annealing. This study evaluates the performance of Ru–Cr nanolayers used as protective coatings for precision glass molding (PGM) applications. Because the direct growth of Cr-oxide from Cr at high temperatures does not yield a dense oxide scale, Ru is employed as a diffusion barrier to stabilize the growth process. The fabricated coatings were subjected to annealing at 750 °C for different durations, with the coverage of aluminosilicate glass (ASG) pieces. During the annealing process, the outward diffusion of Cr resulted in the formation of thin and stable chromium oxide (Cr 2 O 3) films, which remained unadhered to the glass pieces. Therefore, the Ru–Cr bilayer is a cost-effective coating design to protect mold surfaces in PGM. Detailed analysis using transmission electron microscopy (TEM) revealed that while columnar grains with vertical grain boundaries facilitate the outward diffusion of Cr, a thick Ru layer can effectively hinder Cr diffusion leading to a stable oxide film at a high temperature. A diffusion-oxidation phase-field model quantitatively elucidates oxide film thickness dependence on Ru thickness (>600 nm). Thinner Ru layers (<600 nm) display limited Ru thickness influence and some metallic Cr content in the scales, causing incomplete densification. [ABSTRACT FROM AUTHOR]

TiO2 film was applied to graphite substrate through chemical bath deposition (CBD) method with TiCl4 as precursor. CdS was deposited on TiO2/graphite (TiO2/G) by CBD with precursors of CdSO4. A UV-Vis diffuse reflectance (UV-Vis DR) analysis was used to analyze the optical properties and band gap energy. Meanwhile, photocatalytic activity was determined from the quantum yield (QY) value of isopropanol degradation. The X-ray diffraction pattern shows that the TiO2 film contains rutile and anatase phases. UV-Vis DR spectrum shows the photoactivity in the visible light area and provides lower band gap value due to CdS deposition. TiO2/G provide energy gap at 3.0 eV, which indicates that rutile phase is dominant. Meanwhile, CdS-TiO2/G shows multiple energy gaps representing CdS at 2.4 eV, rutile at 3.0 eV, and anatase at 3.2 eV. The QY values of CdS-TiO2/G are 7.98×10-3 and 8.62×10-4 at 450 and 380 nm of radiation light, respectively. These values are higher than the QY of TiO2/G and TiO2-P25/graphite (TiO2-P25/G), which are 1.19×10-4 and 5.0×10-4, respectively. The photocatalytic reaction follows the first-order reaction. CdS deposition allows the rate constant to increase from 2×10-3 to 13×10-3 under UV radiation.

Layers of tungsten were deposited on two types of graphite substrates at three different angular position by a low energy plasma focus device. First series of substrates included only raw graphite while carbon interlayers were used for the second type. Tungsten deposition process was carried out at 0°, 15°, and 30° angular location with respect to the device anode axis during 40 focus shots at optimum argon gas pressure. The characterization of the deposited tungsten coatings was verified by X-ray diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy and Nanoindentation analyses. Tungsten-carbon structures such as WC 1-X , W 2 C, WC, and W 2 (C, O) were detected by XRD analysis. Compounds such as WC 1-X , W 2 C and W 2 (C, O) were identified on raw graphite substrate while WC 1-X , WC, W 2 C were formed on the graphite substrates with carbon interlayer. For both types of samples positioned at 30 degrees with respect to device axis, the WC 1-X phase, which is a high temperature structure with high melting point, was detected more than other tungsten-carbon structures. The coating of carbon interlayer on substrates changes surface morphologies and leads to homogenous deposition of tungsten layer on the surface. The increase in angular position of substrates led to creation of flat and smooth surfaces. Raman spectroscopy shows the presence of WO 3 and amorphous carbon structures in both types of prepared samples. Nanoindentation analysis indicates that the hardness of samples increases after tungsten deposition process. The substrate angular position with respect to anode axis is an effective parameter in deposition process of tungsten layers. • Deposition of tungsten on graphite substrate by a low energy plasma focus device • Effects of substrate angular position on characteristics of coated layers • Production of tungsten-carbon structures • Presence of the highest WC 1-X content at 30° substrate angular position [ABSTRACT FROM AUTHOR]

Here, we prepared nano-SiO2-coated graphite films using a novel laser-assisted sol–gel method. The SiO2 sol–gel prepositioned on the graphite substrate was irradiated by the fiber laser at different energy densities. The growth mechanism of the coatings under laser irradiation was studied and the effects of processing parameters on the coating structure were systematically investigated. In addition, the high-temperature oxidation resistance of these samples was examined. Surface morphology and elemental composition were examined using scanning electron microscopy and energy-dispersive spectrometer. Phase constituents and microstructure were identified by x-ray diffraction and transmission electron microscopy. The oxidation resistance was analyzed by thermal gravimetric analysis. The results found that laser irradiation significantly modifies the sol–gel-deposited nano-SiO2 layer. A uniform and compact nano-SiO2 coating was obtained when irradiated by laser energy density of 14.4 kJ/cm2. Optimum high-temperature oxidation resistance was achieved for the two-layer SiO2-coated films. [ABSTRACT FROM AUTHOR]

Highlights • Deposition of carbon nitride on graphite substrate at different angular positions. • Deposition of thin films by plasma focus device. • Observance of two distinct trends at various substrate angular positions. Abstract Amorphous carbon nitride (a-CNx) thin films were deposited on graphite substrate at different angular positions using a low energy (up to 4.9 kJ) Mather-type plasma focus device. The deposition processes were carried out during 20 focus shots at optimum nitrogen gas pressure of 0.4 mbar. The formation of amorphous carbon nitride was confirmed by Raman Spectroscopy, SEM, EDX, FTIR, and XRD analyses. The intensity ratio of D and G peaks (I D /I G) recorded by Raman Spectroscopy showed two distinct trends at various angular positions. The sample deposited at 30° had the highest I D /I G ratio and correspondingly the highest sp3 CH x content in FTIR spectrum. Samples with lower I D /I G ratio appeared with smaller grain size and more smooth surfaces in SEM images. The highest C N intensities in FTIR spectrum belonged to those samples deposited at 30 and 75° angular positions. [ABSTRACT FROM AUTHOR]

Silicene is considered to be the most promising anode material for lithium-ion batteries. In this work, we show that transmutation doping makes silicene substantially more suitable for use as an anode material. Pristine and modified bilayer silicene was simulated on a graphite substrate using the classical molecular dynamics method. The parameters of Morse potentials for alloying elements were determined using quantum mechanical calculations. The main advantage of modified silicene is its low deformability during lithium intercalation and its possibility of obtaining a significantly higher battery charge capacity. Horizontal and vertical profiles of the density of lithium as well as distributions of the most significant stresses in the walls of the channels were calculated both in undoped and doped systems with different gaps in silicene channels. The energies of lithium adsorption on silicene, including phosphorus-doped silicene, were determined. High values of the self-diffusion coefficient of lithium atoms in the silicene channels were obtained, which ensured a high cycling rate. The calculations showed that such doping increased the normal stress on the walls of the channel filled with lithium to 67% but did not provoke a loss of mechanical strength. In addition, doping achieved a greater battery capacity and higher charging/discharging rates.

Diamond micro powders have been synthesized by chemical vapor deposition via etching a graphite substrate in hydrogen microwave plasma, without a hydrocarbon (methane) gas addition. The graphite temperature, varying from 700 to 1000 °C, was found to significantly affect the diamond nucleation and growth, the growth rate of the diamond particles increasing from 2.4 to ≈ 4 μm/h with the temperature. The diamond powders had a better crystalline quality at the substrate temperature of 900 °C. Because of low adhesion of the deposited grit to the substrate the particles can be collected easily and mechanically disaggregated. The average size of ≈ 12 μm of the dispersed particles grown for 5 h, was determined with a laser particle size analyzer, while the maximum grain size estimated with electron microscopy, varied between 12 and ≈ 20 μm. The particle's surface exhibited many micro-pyramids with sharp tips, that could be beneficial for abrasive applications. X-ray diffraction and Raman spectroscopy revealed high purity and quality of the diamond powders. [ABSTRACT FROM AUTHOR]

Nickel nanoparticles of the size 50−60 nm were deposited on graphite particles by electroless plating. The sensitized and activated graphite powder was used as substrate precursor. The depositions of nickel and under layers of Pd and Sn on graphite particles were characterized by the Field Emission Scanning Electron Microscopy (FESEM), XRD, XPS and Energy Dispersive X-ray (EDX) techniques. The FESEM images have shown the deposition of the nickel nanoparticles. The Zeta particle analyser (ZPA) has inferred about the conductivity and average particle sizes of graphite and nickel/graphite powder. The calculated active surface area and surface coverage of Ni-deposited electrode are 0.15 × 10 cm and 2.4409 × 10 mol cm, respectively. The Electrochemical studies of graphite and Sn/graphite, Pd/Sn/graphite and finally the Ni−Pd/Sn/graphite were carried out using cyclic voltammetry (CV) in the potential range between −1.0 and 1.0 (V versus SCE) at the scan rate of 50 mV s. The electrocatalytic activity of the catalyst substance was investigated for methanol oxidation in KOH medium. Electrochemical Impedance Spectroscopy (EIS) studies of the above electrodes for methanol oxidation in 0.5 M KOH solution have shown a very small arc in the high-frequency region, which corresponds to low charge resistance and high capacitance. This implied that nickel supported on graphite would be a better electrocatalyst for fuel cell application. Graphical Abstract: Nickel nanoparticles of 50-60 nm size were deposited on graphite substrates by electroless nickel plating. The formation of Ni/graphite powders were proven by SEM, XRD, ZPA, XPES and EDX techniques. A significant electrochemical/catalytic activity of the Ni/graphite electrode was observed by impedance spectroscopy and cyclic voltammetry for methanol oxidation. [ABSTRACT FROM AUTHOR]

TiO2 film was applied to graphite substrate through chemical bath deposition (CBD) method with TiCl4 as precursor. CdS was deposited on TiO2/graphite (TiO2/G) by CBD with precursors of CdSO4. A UV-Vis diffuse reflectance (UV-Vis DR) analysis was used to analyze the optical properties and band gap energy. Meanwhile, photocatalytic activity was determined from the quantum yield (QY) value of isopropanol degradation. The X-ray diffraction pattern shows that the TiO2 film contains rutile and anatase phases. UV-Vis DR spectrum shows the photoactivity in the visible light area and provides lower band gap value due to CdS deposition. TiO2/G provide energy gap at 3.0 eV, which indicates that rutile phase is dominant. Meanwhile, CdS-TiO2/G shows multiple energy gaps representing CdS at 2.4 eV, rutile at 3.0 eV, and anatase at 3.2 eV. The QY values of CdS-TiO2/G are 7.98 × 10-3 and 8.62 × 10-4 at 450 and 380 nm of radiation light, respectively. These values are higher than the QY of TiO2/G and TiO2-P25/graphite (TiO2-P25/G), which are 1.19 × 10-4 and 5.0 × 10-4, respectively. The photocatalytic reaction follows the first-order reaction. CdS deposition allows the rate constant to increase from 2 × 10-3 to 13 × 10-3 under UV radiation. [ABSTRACT FROM AUTHOR]

The W/a-C:H:Zr and W/a-C:H:W multilayer coatings were prepared on a porous graphite substrate by hybrid method combines of arc evaporation and electron beam evaporation processes (Arc-EB). The tungsten interlayer was deposited first to enhance coating adhesion. Phase composition of coatings was examined by Raman spectroscopy and X-ray diffraction. The measurement of hardness and Young's modulus has indicated a significant increase in mechanical properties after the deposition of upper layer. Microstructure was investigated by SEM and TEM revealing columnar morphology and lack of porosity in both samples. The a-C:H:Zr coating was characterized by lower wettability by liquid copper than a-C:H:W coating and pure tungsten interlayer. [ABSTRACT FROM AUTHOR]

Tungsten coating on graphite substrate is considered as one of promising candidate materials of plasma facing components. In this study, tungsten coatings on graphite substrate were successfully prepared by direct current (DC) and pulse current (PC) electrodeposition methods in NaWO-WO molten salt under the air atmosphere. Pores were found on the surfaces of the tungsten coatings produced by DC electrodeposition method. For the coatings fabricated by PC method, compact and smooth tungsten coatings were successfully obtained. The crystal structure, morphology, density, microhardness, adhesive strength, oxygen content and the thermal conductivity of the coatings fabricated by PC method were investigated. The obtained tungsten coatings had a body centered cubic structure. After electro-deposition for 100 h, the thickness of the tungsten coating reached 810.02 ± 10.40 μm and the oxygen content was 0.03 wt%. The thermal conductivity of the tungsten coating was 134.29 W m K. The density of the tungsten coating was 18.83 g cm. The hardness of the coating was 492.0 ± 7.8 HV. After deuterium plasma irradiation, the tungsten coatings were prone to blistering. [ABSTRACT FROM AUTHOR]

Hydrogenated intrinsic amorphous silicon (a-Si:H) was investigated as a surface passivation method for crystalline silicon thin film solar cells on graphite substrates. The results of the experiments, including quantum efficiency and current density–voltage measurements, show improvements in cell performance. This improvement is due to surface passivation by an a-Si:H( i ) layer, which increases the open circuit voltage and the fill factor. In comparison with our previous work, we have achieved an increase of 0.6% absolute cell efficiency for a 40 μm thick 4 cm 2 aperture area on the graphite substrate. The optical properties of the SiN x /a-Si:H( i ) stack were studied using spectroscopic ellipsometer techniques. Scanning transmission electron microscopy inside a scanning electron microscope was applied to characterize the cross section of the SiN x /a-Si:H( i ) stack using focus ion beam preparation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ru and Pt monolayers, and Ru-Pt multilayer coatings were evaluated for precision glass molding. • Multilayer coatings revealed better surface quality and anti-sticking performances than monolayer coatings. • Hindrance in dislocation movement and atomic diffusion was explained by the addition of interfaces, and perseverance of multilayer structure was observed after long-term annealing. • The performance of multilayer coatings was also validated by industrial testing. This work describes the performance of multilayer Ru–Pt coatings with Ti as the interlayer deposited on graphite substrate for applications in precision glass molding (PGM). Different from the previous evaluations with other kinds of coatings for PGM temperatures below 650 °C, we studied the anti-sticking behavior of the developed coatings by annealing them at 750 °C with aluminosilicate glass coverage in a rough vacuum environment. Glass adhesion was not observed even after 40-hour annealing suggesting the high chemical inertness of the coatings at the high temperature. In addition, the Ru–Pt multilayer coatings exhibited a better anti-sticking property than monolayer (Ru or Pt) coatings. The microstructure, surface morphology, and hardness were further characterized. High-resolution transmission electron microscopy (HRTEM) analysis confirmed the perseverance of layered structure after annealing at 750 °C and the hindrance effect on dislocation motion and diffusion arising from the Ru-Pt interfaces. After long-term annealing, interdiffusion leads to Pt-Ru solid solutions, which further enhance the mechanical performance and stability of the noble metal coatings, beneficial for prolonging the lifespan of PGM molds and the optical quality of molded glass. The high anti-sticking and mechanical performances of the developed coatings were finally confirmed in industrial tests. [ABSTRACT FROM AUTHOR]