Carbonaceous Coatings Research Articles

On the Distinctive Hardness, Anti-Corrosion Properties and Mechanisms of Flame-Deposited Carbon Coating with a Hierarchical Structure in Contrast to a Graphene Layer via Chemical Vapor Deposition.

Two carbonaceous (amorphous carbon and graphene) coatings were catalytically grown on bulk Ni plates. It was found that the flame-deposited carbon (FDC) layers exhibited a unique hierarchical structure with the formation of FDC/Ni nano-interlocking interface. The effect of the flame coating time on its corrosion protective efficiency (PE) was studied and compared with that of graphene coating produced via chemical vapor deposition. The FDC grown for 10 min exhibited a PE of 92.7%, which was much greater than that of the graphene coating (75.6%). The anti-corrosive mechanisms of both coatings were revealed and compared. For graphene coatings, the higher reaction temperature than that for FDC resulted in large grain boundaries inherent in the coating. Such boundaries were weak points and easily initiated grain boundary corrosion. In contrast, corrosion started at only certain local defects in FDC layers, whose unique interface structure likely promoted its PE as well. Moreover, after the coating process, the hardness of FDC-coated Ni remained almost unchanged, in contrast to that of graphene-coated samples (reduced by ~30%). This is suggested to be related to the crystal structure evolution of the Ni substrate caused by the heat treatment accompanying the coating process.

Distinguishing cellular from abiotic spheroidal microstructures in the ca. 3.4 Ga Strelley Pool Formation.

The morphogenesis of most carbonaceous microstructures that resemble microfossils in Archean (4-2.5Ga old) rocks remains debated. The associated carbonaceous matter may even-in some cases-derive from abiotic organic molecules. Mineral growths associated with organic matter migration may mimic microbial cells, some anatomical features, and known microfossils-in particular those with simple spheroid shapes. Here, spheroid microstructures from a chert of the ca. 3.4 Ga Strelley Pool Formation (SPF) of the Pilbara Craton (Western Australia) were imaged and analyzed with a combination of high-resolution in situ techniques. This provides new insights into carbonaceous matter distributions and their relationships with the crystallographic textures of associated quartz. Thus, we describe five new types of spheroids and discuss their morphogenesis. In at least three types of microstructures, wall coalescence argues for migration of carbonaceous matter onto abiotic siliceous spherulites or diffusion in poorly crystalline silica. The nanoparticulate walls of these coalescent structures often cut across multiple quartz crystals, consistent with migration in/on silica prior to quartz recrystallization. Sub-continuous walls lying at quartz boundaries occur in some coalescent vesicles. This weakens the "continuous carbonaceous wall" criterion proposed to support cellular inferences. In contrast, some clustered spheroids display wrinkled sub-continuous double walls, and a large sphere shows a thick sub-continuous wall with pustules and depressions. These features appear consistent with post-mortem cell alteration, although abiotic morphogenesis remains difficult to rule out. We compared these siliceous and carbonaceous microstructures to coalescent pyritic spheroids from the same sample, which likely formed as "colloidal" structures in hydrothermal context. The pyrites display a smaller size and only limited carbonaceous coatings, arguing that they could not have acted as precursors to siliceous spheroids. This study revealed new textural features arguing for abiotic morphogenesis of some Archean spheroids. The absence of these features in distinct types of spheroids leaves open the microfossil hypothesis in the same rock. Distinction of such characteristics could help addressing further the origin of other candidate microfossils. This study calls for similar investigations of metamorphosed microfossiliferous rocks and of the products of in vitro growth of cell-mimicking structures in presence of organics and silica.

Facile fabrication of novel cobalt-based carbonaceous coatings on nickel-titanium alloy fiber substrate for selective solid-phase microextraction

Fabrication of selective adsorption coatings plays a crucial role in solid-phase microextraction (SPME). Herein, new strategies were developed for the in-situ fabrication of novel cobalt-based carbonaceous coatings on the nickel-titanium alloy (NiTi) fiber substrate using ZIF-67 as a precursor and template through the chemical reaction of ZIF-67 with glucose, dopamine (DA) and melamine, respectively. The adsorption performance of the resulting coatings was evaluated using representative aromatic compounds coupled to high-performance liquid chromatography (HPLC) with ultraviolet detection (HPLC-UV). The results clearly demonstrated that the adsorption selectivity was subject to the surface elemental composition of the fiber coatings. The cobalt and nitrogen co-doped carbonaceous coating showed better adsorption selectivity for ultraviolet filters. In contrast, the cobalt-doped carbonaceous coating exhibited higher adsorption selectivity for polycyclic aromatic hydrocarbons. The fabricated fibers present higher mechanical stability and higher adsorption capability for model analytes than the commercial polydimethylsiloxane and polyacrylate fibers. These new strategies will continue to expand the NiTi fibers as versatile fiber substrates for metal-organic frameworks (MOFs)-derived coating materials with controllable nanostructures and tunable properties.

Fabrication of onion-like fullerene nanostructure film by electrochemical reduction

Onion-like fullerenes possess distinctive physical and chemical performance, and thus are believed to have great significance in theoretical study and engineering applications. In this exploratory research, we introduced a novel way, namely electrochemical reduction method performed in aqueous solution at room temperature and very low voltages, for preparing a film composed of onion-like fullerene nanostructures. The method was discovered by accident. During the preparation of thick Cr coating by electrodepositing from Cr (III) electrolyte, a layer of black film was found at the interface between the steel substrate and Cr coating. XPS analysis shows that the main element contained in the film is C. The results from Raman spectrum, HRTEM and SAED reveal that the carbonaceous film is composed of the nanostructures roughly having onion-like fullerene unit. This means with significant advantages has the potential to develop into a practical technique for fabricating carbonaceous films or coatings.

Microstructures, mechanical properties and tribological behaviors of amorphous carbon coatings in-situ grown on polycarbonate surfaces

Pure amorphous carbon (a-C) coating, chromium doped amorphous carbon (a-C/Cr) coating and silicon doped amorphous carbon (a-C/Si) coating were synthesized on Polycarbonate (PC) plastic substrates by continuous treatment of different plasma combinations. Microstructures, mechanical properties and tribological behaviors of the as-presented coatings were systematically investigated. As a result, the in-situ growth mechanisms were demonstrated for all of these carbonaceous coatings. This in-situ growth meant an in-situ transformation from the polymer structure into inorganic structure from the surface or subsurface of the substrate followed by an epitaxial growth on the transformed inorganic layer. Cr and Si dopant generated a bulky microstructure, leading to a higher density of in-situ grown a-C/Cr and a-C/Si coatings than the a-C coating on PC substrates. The hardness and elastic modulus of PC substrate were significantly improved by these in-situ grown carbonaceous coatings. Pure a-C coating showed the best protective effect on PC substrate under sliding-friction condition, with scaly protection mechanism, among these different coatings. The fundamental for good protective effect of pure a-C coating on PC was the in-situ growth mechanism, which endowed reliable adhesion of hard a-C coating on soft PC substrate even if there were cracks under sliding condition.

Effect of Functionalization of Reduced Graphene Oxide Coatings with Nitrogen and Sulfur Groups on Their Anti-Corrosion Properties.

Electrophoretic production of anticorrosion carbonaceous coatings on copper could be successfully performed by anodic oxidation of negatively charged graphene platelets suspended in an aqueous solution. The various platelets were synthesized by Hummer’s method followed by a hydrothermal reduction in the presence of NH4SCN which was expected to substitute some parts of graphene structure with nitrogen and sulfur groups. X-ray photoelectron spectroscopy analysis confirmed that the graphene precursors, as well as the coatings, contained typical nitrogen groups, such as pyridinic and pyrrolic, and sulfur groups, such as thiol, thiophene, or C-SO2. However, due to oxidation during deposition, the qualitative and quantitative composition of the graphene coatings changed relative to the composition of the precursors. In particular, the concentration of nitrogen and sulfur dropped and some thiophene groups were oxidized to C-SO2. Studies showed the functionalized coatings had a uniform, defect-free, hydrophobic, more adhesive surface than nonmodified films. The corrosion measurements demonstrated that these coatings had better protective properties than the ones without these heteroatoms. This behavior can be assigned to the catalytic activity of nitrogen towards oxidation of C-SO2 groups to C-SO3H with oxygen.

Direct laser-induced deposition of AgPt@C nanoparticles on 2D and 3D substrates for electrocatalytic glucose oxidation

We present a new approach for the preparation of electrocatalytically active carbonaceous coatings embedding bimetallic nanoparticles (NPs) - AgPt@C structures, on surfaces with 2D and 3D geometry such as glass covered with indium tin oxide (ITO) film and anodic aluminum oxide substrates, respectively. We provide extensive characterization of the deposited structures and demonstrate their performance towards the electrocatalytic glucose oxidation, one half-reaction of biofuel cells. We observe that a preliminary surface treatment of the porous alumina substrate is essential for a homogeneous laser-induced deposition of AgPt@C nanoparticles across the whole pore depth.

Constructing hydrothermal carbonization coatings on carbon fibers with controllable thickness for achieving tunable sorption of dyes and oils via a simple heat-treated route

Tremendous efforts have been dedicated to developing sorbents for water remediation due to their high efficiency and non-secondary pollution. However, the majority of sorbents still face the challenges of complex processing, low mechanical strength and volume absorption. Hence, the functional hydrothermal carbonization coatings (HTCCs) were prepared on carbon fibers in carbon fiber braid via a facile hydrothermal carbonization process of widely sourced carbohydrate to obtain a robust sorbent, which possessed the controllable microstructure and composition for various requirements of water remediation. The gradient surface structure of carbon fiber braid with interior smooth coatings carbon fibers and exterior rough surface could be fabricated at pH value of 1. The HTCCs-carbon fiber braid had superior yield strength and compressive strength. By regulating the reaction process, the yield strength could range from 0.044 MPa to 0.235 MPa and the max compressive strength change from 0.198 MPa to 1.113 MPa. The HTCCs-carbon fiber braid showed excellent adsorption for Rhodamine B with a high removal degree of 98.5%, which kept more than 90% even after 10 squeezing adsorption cycles. The HTCCs-carbon fiber braid could be adjusted to effectively absorb oil pollutants from water by a facile heat treatment. After heat treatment, the HTCCs-carbon fiber braid exhibited excellent volume absorption capacity for contaminants, which could change from 83.9% to 88.5%. Thus, the HTCCs-carbon fiber braid prepared by a green, high-efficiency and low-cost process has great potential for sorption multiple contaminations in water by virtue of the combination of controllable carbonaceous coatings and robust carbon fiber braid.

Mechanical Desensitization of an Al/WO3 Nanothermite by Means of Carbonaceous Coatings Derived from Carbohydrates

Nanothermites show great developmental promise in the near future in civilian, military and aerospace applications due to their tuneable reactive properties (ignition delay time, combustion velocity and pressure release). However, the high mechanical sensitivities of some of these energetic nanocomposites can make transportation and handling of them hazardous. Here, a mechanical desensitization (shock and friction) of an Al/WO3 nanothermite is successfully obtained by means of carbon adding through the pyrolysis of naturally occurring molecules (carbohydrates). The combustion behaviour of the carbon-based energetic mixtures were also evaluated and a respectable reactivity has been evidenced.

Measuring scattering light distributions on high-absorptive surfaces for stray-light reduction in gravitational-wave detectors.

In order to establish scattering measurements in material investigations for gravitational-wave detectors, we have built-up devices for measuring the hemispherical scattering distribution of materials which are planned to be used in those detectors as suppressors of scattered light. The measurement benches we have built, a hemispherical goniometer and a direct back-scatterometer, have a maximum background noise of ∼10-4sr-1 BRDF at 1.064 μm wavelength which is the wavelength of the laser-light for our large interferometer for detecting gravitational waves, KAGRA. With these instruments, we have characterized the surface scattering of, e.g., NiP platings, metals, and different carbonaceous coatings, which are supposed to minimize the amount of scattered light in interferometers. The three most important materials for KAGRA's construction (SiC, "Solblack", and "VantaBlack") are presented in this paper. Furthermore, we will try to explain the scattering distributions with the generalized Harvey-Shack model (smooth-surface approximation) which is a common method for surface-scattering calculations. At the end, we give also some valuations about the vacuum compatibility of the materials, which is important for instruments like KAGRA that work under ultra-high vacuum conditions.

Uniform Multilayer Graphene-Coated Iron and Iron-Carbide as Oxygen Reduction Catalyst

The industrialization of fuel cells is coming. Non-noble metals with carbonaceous coatings, as cathodic catalysts for fuel cells, expected to replace platinum for catalyzing the oxygen reduction reaction (ORR), have attracted the attention of researchers. This is mainly due to the low price, easy availability, high stability, and gratifying catalytic activity of these materials. However, the high density and uniform dispersion of coated particles still face a challenge. In view of this, we prepared Fe3C/Fe@G catalysts with a structure of nitrogen-doped multilayer graphene uniformly coated on iron and iron carbide (Fe3C/Fe) in a very simple way. The half wave potential of Fe3C/Fe@G-800 is comparable to that of commercial Pt/C, and it also highlights the excellent stability that is a benefit of the complete coating of graphene layers to internal particles; highly dispersed Fe3C/Fe nanoparticles with small size in the graphene layer; the equilibrium degree of graphitization and the defect density.

Clarification of effect of surface energy on friction properties of carbonaceous hard coatings by in-situ measurement of ESEM

Clarification of effect of surface energy on friction properties of carbonaceous hard coatings by in-situ measurement of ESEM

Dual or multi carbonaceous coating strategies for next-generation batteries

Dual or multi carbonaceous coatings construct continuous electron-transport pathways within the entire electrodes together with conformal surface protection.

The Clarification of Low Friction Mechanism for Hydrogenated Amorphous Carbon by In-Situ Observation of Frictional Area

Hydrogenated amorphous carbon (a-C:H) coating which is one of carbonaceous coatings shows ultra low friction coefficient (μ < 0.01) in dry Nitrogen gas. At present, it is expected to clarify low friction mechanism of a-C:H coating to apply a-C:H coating to industrial components. It was reported that hydrogen concentration, density, thickness and volume fraction of chemical bonds of surface layer (transformed layer) on bulk a-C:H coating during friction test were important to clarify low friction mechanism. But it is difficult to measure hydrogen concentration and density of transformed layer during friction test. In this study, we estimate the thickness and volume fractions of C-Csp2, C-Csp3 and C-H bond of transformed layer during friction test by reflectance spectroscopy. In addition we calculate hydrogen concentration from volume fraction of C-H bond and filling factor related to density of transformed layer during friction test. After friction test, surface energy of transformed layer is measured by sessile drop method. As a result, it is suggested that a-C:H coating shows low friction coefficient by reducing real contact area due to densification of transformed layer and repulsion force in hydrogen-terminated surface.

Surface phase transition on silicon crystals (100) with low-temperature microwave plasma chemical vapor deposition

Using the Langmuir model of adsorption from the precursor state, the phenomenon of self-organization of nanosized domains with low-pressure ethanol chemical vapor deposition of submonolayer carbonaceous coatings on the atomically-clean surface of silicon crystals (100) is investigated. The dependence of the substrate temperature and the electrical bias on the kinetics and the mechanism of the domain structuring, which is the phase transition on the silicon surface (100), is analyzed. It is shown that, in some chemically-active gaseous environments, the high etching selectivity of silicon and carbon makes it possible to use carbon islands being formed as nonlithographic masks to create nanosized integrated column structures in silicon crystals (100) by means of high-resolution plasma-chemical etching.

F221001 カーボン系硬質膜の薄膜潤滑理論による摩擦力の推定

F221001 カーボン系硬質膜の薄膜潤滑理論による摩擦力の推定

The Study of Iron-based Nanoparticles Stability in Biological Fluids by Stripping Voltammetry

The possibility of application of voltammetric methods for evaluating the stability of nanoparticles in biological fluids has been shown for the first time. The kinetics of degradation both of uncoated nanoparticles and with different coatings in a simulated solution of gastric juice in a wide range of time has been studied. It has been shown that by using carbonaceous coatings nanoparticles resistance increases 2-4 times, and when modifying the surface with aryldiazonium salts - 5-6 times.

Nanostructured Anatase TiO2 - from Lithium- to Sodium-Ion Anodes

Lithium-ion batteries are nowadays the energy storage device of choice for portable electronic devices due to their superior energy and power density. Consequently, they are considered also as most promising power source for large-scale applications as, for instance, electric vehicles [1–3]. However, for such applications further improvement of the existing technology is required in terms of energy, power, and particularly safety. Beside Li4Ti5O12, which is already used in commercial cells, anatase TiO2 – particularly in its nanostructured form - is seriously considered as alternative anode material to replace graphite due to its enhanced safety and rate capability [4,5].Remarkably, anatase TiO2 was recently demonstrated to be highly promising as high power anode material for sodium-ion batteries [6,7], which are considered as low-cost alternative for lithium-ion batteries. These batteries are especially interesting for stationary energy storage applications in order to balance the energy supply provided by renewables, for which size and weight are less important, while cost are of major importance.Herein we will report our latest results on the utilization of nanostructured anatase TiO2 for lithium- and sodium-ion batteries, including the importance of carbonaceous coatings and percolating networks, and highlight the major differences regarding the lithium- and sodium-ion storage mechanism.

Enhanced Aerobic Epoxidation of Styrene with Copper(II), Cobalt(II), Iron(III), or Oxovanadium(IV) Salen Complexes Immobilized onto Carbon‐Coated Fe3O4 Nanoparticles Hybridized with Graphene Sheets

AbstractCore–shell structural magnetic nanocatalysts, involving carbon‐coated magnetic Fe3O4 nanoparticles supported on graphene oxide sheets (mildly reduced graphene oxide (MRGO)/Fe3O4@C) and carbonaceous coatings on magnetic Fe3O4 nanoparticles (Fe3O4@C), for immobilizing metal (CuII, CoII, FeIII or VOIV)–salen complexes were prepared by a facile, green, and efficient chemical approach and first applied in the aerobic epoxidation of styrene with air as the oxidizing agent. The prepared catalysts were characterized by different techniques, such as XRD, TEM, FTIR spectroscopy, inductively coupled plasma atomic emission spectroscopy, TEM, thermogravimetric analysis, Raman spectroscopy, and X‐ray photoelectron spectroscopy. The magnetic nanocatalysts MRGO/Fe3O4@C–salen–M (M=Cu, Co, Fe, or V) exhibited higher catalytic reactivity than that of the corresponding Fe3O4@C–salen–M (M=Cu, Co, Fe, or V) species possibly owing to site isolation, good dispersion of magnetic Fe3O4 nanoparticles, and an efficiently synergistic effect between the metal complexes and the supports. Furthermore, MRGO/Fe3O4@C–salen–Co exhibited up to 92.3 % conversion of styrene and 59.2 % selectivity to the styrene oxide upon using air as the oxidizing agent and showed good recoverability with negligible loss in activity and selectivity within successive runs owing to superparamagnetism. Most importantly, these materials can be easily recovered by simple magnetic separation.

Hybridization of graphene sheets and carbon-coated Fe3O4 nanoparticles as a synergistic adsorbent of organic dyes

Magnetic graphene–Fe3O4@carbon (GFC) hybrids with hierarchical nanostructures have been synthesized and their application as an adsorbent for the removal of organic dyes has been investigated. Graphene–Fe3O4 hybrids were first prepared via a facile one-pot solvothermal process, then carbonaceous coatings on Fe3O4 nanoparticles of nanometer thickness were synthesized by a hydrothermal carbonization process using eco-friendly glucose as a carbon source. Graphene sheets acting as two-dimensional (2D) substrates can effectively prevent the Fe3O4 nanoparticles from aggregating and enable a good dispersion of these magnetic nanoparticles. The carbonaceous layer protects the Fe3O4 nanoparticles in acidic environments and greatly enhances the specific surface area of the hybrids which is beneficial for the removal of organic dyes, such as methylene blue (MB). The resultant GFC hybrids exhibit great adsorption properties not only in water but also in acidic environments, and about 86% and 77% of the dye removal efficiency can be retained after five adsorption–desorption cycles in water and 1 M HCl, respectively. The rapid and efficient adsorption of organic dyes from water as well as acid suggests that the GFC hybrids have potential environmental applications as alternatives to commercial materials in wastewater treatment for the removal of organic dyes.