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Vanadium dioxide (VO2) with an insulator-to-metal (IMT) transition (∼68 °C) is considered a very attractive thermochromic material for smart window applications. Indeed, tailoring and understanding the thermochromic and surface properties at lower temperatures can enable room-temperature applications. The effect of W doping on the thermochromic, surface, and nanostructure properties of VO2 thin film was investigated in the present proof. W-doped VO2 thin films with different W contents were deposited by pulsed laser deposition (PLD) using V/W (+O2) and V2O5/W multilayers. Rapid thermal annealing at 400–450 °C under oxygen flow was performed to crystallize the as-deposited films. The thermochromic, surface chemistry, structural, and morphological properties of the thin films obtained were investigated. The results showed that the V5+ was more surface sensitive and W distribution was homogeneous in all samples. Moreover, the V2O5 acted as a W diffusion barrier during the annealing stage, whereas the V+O2 environment favored W surface diffusion. The phase transition temperature gradually decreased with increasing W content with a high efficiency of −26 °C per at. % W. For the highest doping concentration of 1.7 at. %, VO2 showed room-temperature transition (26 °C) with high luminous transmittance (62%), indicating great potential for optical applications. [ABSTRACT FROM AUTHOR]

We report the results of a comparative investigation of graphene films prepared on Si(100) and fused silica (SiO2) combining pulsed laser deposition and rapid thermal annealing using Ni catalyst. The effect of modifying the substrate and/or growth temperature (600–1,000°C) of graphene synthesis was investigated by Raman microspectroscopy mapping. Graphene grown on Si(100) was multilayered, and various nickel silicide phases had formed underneath, revealing dependence on the growth temperature. Films prepared on SiO2 mainly comprised bilayered and trilayered graphene, with no traces of nickel silicide. Analysis of Raman D, G, and 2D peak intensities and positions showed that modifying the growth temperature had different effects when a Si(100) or a SiO2 substrate is used. These findings advance our understanding of how different combinations of substrate and thermal processing parameters affect graphene synthesis from solid carbon source using nickel as a catalyst. This knowledge will enable better control of the properties of graphene film (defects, number of layers, etc.) and will have a high potential impact on the design of graphene‐based devices for scientific or industrial applications. [ABSTRACT FROM AUTHOR]

Surface functionalization has numerous applications worldwide. Silicon oxide has been a research material of choice. However, tin dioxide (SnO) films are employed in many applications especially in gas sensors, and little studied in regard to functionalization. Thus, they were chosen to be functionalized via 3-aminopropyltriethoxysilane (APTES). Different synthesis parameters were tested such as APTES grafting by vapor or liquid phases deposition. In liquid, many parameters were investigated: water presence, reaction times, and APTES concentration. The presence and reactivity of grafted amine-terminated film on SnO were carried out by Alexa Fluor molecules. In addition, APTES grafting was characterized using attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectrometry techniques. These characterizations showed how synthesis parameters affect the amount and thickness of APTES films. Optimal liquid silanization parameters were determined in order to obtain a saturated SnO surface with APTES molecules. Importantly, the addition of 5 vol% HO to the APTES solution provided denser surface coverage, by hydrolyzing the ethoxy groups to silanol. An almost 50% improvement over anhydrous liquid and vapor methods was obtained. [ABSTRACT FROM AUTHOR]

An adequate model of quantification when there are many segregating elements is required for industry and research. Hence, for the first time, surface segregation kinetics on industrial 16MND5 steel was studied by XPS spectroscopy at temperatures ranging from 500 to 600 oC. From measurements that highlight the competitive segregation of P, S, Sn, Sb, As, and Cu impurities at the surface, a quantification model was developed and successfully used to deduce the surface concentrations during segregation kinetics as well as derive the corresponding diffusion coefficients. We observed that phosphorus and sulfur are the first elements covering the surface, then they are supplanted by others' impurities. This result may reflect impurities segregation behavior at the grain boundaries that impacts mechanical behavior of the material. Indeed, to further the research, 16MND5 samples were aged in the same range of temperatures. Then, Auger spectroscopy measurements at grain boundaries were conducted on broken samples exhibiting intergranular cracking. Results show that phosphorus is the only segregating element present at grain boundaries after 2 months of aging. Importantly, it appears that phosphorus grain boundary segregation kinetics is significantly lower than at surface. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We report the synthesis, characterization and use of a robust surface enhanced Raman spectroscopy platform with a stable detection for up to one year of Rhodamine R6G at a concentration of 10 − 6 M. The detection of aminothiophenol and methyl parathion, as active molecules of commercial insecticides, is further demonstrated at concentrations down to 10 − 5 –10 − 6 M. This platform is based on large scale textured few-layer (fl) graphene obtained without any need of graphene transfer. The synthesis route is based on diamond-like carbon films grown by pulsed laser deposition, deposited onto silicon substrates covered by a Ni layer prior to diamond-like carbon deposition. The formation of fl-graphene film, confirmed by Raman spectroscopy and mapping, is obtained by thermal annealing inducing the diffusion of Ni atoms and the concomitant formation of nickel silicide compounds, as identified by Raman and Auger electron spectroscopies. The textured fl-graphene films were decorated with gold nanoparticles to optimize the efficiency of the SERS device to detect organic molecules at low concentrations. [ABSTRACT FROM AUTHOR]

This study shows that the corrosion behaviour of 12 wt% Cr steel in CO 2 at 550 °C is determined in the first stage of oxidation by reaction with O 2 impurities. Depending on the amount of theses impurities and the thermal ramp rate, selective oxidation of chromium could lead to the formation of a protective chromium-rich oxide. An oxidation model describing qualitatively the nature of the oxide layer formed in the initial period of oxidation is presented. From these observations, surface engineering processes for protecting 9–12 wt% chromium steels from fast corrosion rate have emerged. [ABSTRACT FROM AUTHOR]

A complete chromium depletion profile with its depth resolution in the nanometre range was obtained on a Ni–16Cr–9Fe model alloy after a 10h oxidation at 950°C in air. Auger electron spectroscopy coupled to ion sputtering and energy-dispersive X-ray spectroscopy were used to measure the chromium depletion profile. The chromium content at the oxide/alloy interface is below 0.5wt.%. This exceptionally low Cr content is in agreement with Wagner’s model for binary alloys. [Copyright &y& Elsevier]

Graphene-based materials are widely studied to enable significant improvements in electroanalytical devices requiring new generations of robust, sensitive and low-cost electrodes. In this paper, we present a direct one-step route to synthetize a functional nitrogen-doped graphene film onto a Ni-covered silicon electrode substrate heated at high temperature, by pulsed laser deposition of carbon in the presence of a surrounding nitrogen atmosphere, with no post-deposition transfer of the film. With the ferrocene methanol system, the functionalized electrode exhibits excellent reversibility, close to the theoretical value of 59 mV, and very high sensitivity to hydrogen peroxide oxidation. Our electroanalytical results were correlated with the composition and nanoarchitecture of the N-doped graphene film containing 1.75 at % of nitrogen and identified as a few-layer defected and textured graphene film containing a balanced mixture of graphitic-N and pyrrolic-N chemical functions. The absence of nitrogen dopant in the graphene film considerably degraded some electroanalytical performances. Heat treatment extended beyond the high temperature graphene synthesis did not significantly improve any of the performances. This work contributes to a better understanding of the electrochemical mechanisms of doped graphene-based electrodes obtained by a direct and controlled synthesis process. [ABSTRACT FROM AUTHOR]

Abstract The trends in automotive industry are towards higher performance, improved reliability, reduced tolerances and more environmental friendly products. Wear resistance enhanced mechanical components exhibiting lower friction help achieving this major challenge. Diamond-Like Carbon (DLC) deposited on mechanical components operating under lubricated conditions at temperatures between 100 and 250 °C, efficiently decrease the friction coefficient and insure wear protection. Wear induced debonding and blistering of hard surface coatings is still a major problem in the automotive industry. There are several open questions. Where does debonding start? Where does the interface crack propagate? Where does it deviate leading to delamination? In this work, we show how the combination of the latest experimental techniques allows to answer these questions and thus better control wear. Blistering is influenced by the overall stress in the coating and the very local microstructure of the substrate. A combination of AFM and nano-indentation measurements, as well as FIB milling with in situ FEG-SEM observations and local chemical measurements by EDX, allows to observe closely and better understand wear-induced delamination. The new availability of such physical and chemical investigations should improve mechanical and physical-based models to predict wear and enhance coating adhesion. Graphical abstract Unlabelled Image Highlights • Debonding of diamond-like coating on M2-steels is simulated by tribological test. • The debonding starts some nm under the interlayer inside the M2-steel. • Cracks propagate parallel to the interlayer M2-steel interface. • If an interface crack encounters a carbide, it may deviate and propagate through the coating. [ABSTRACT FROM AUTHOR]

Printing graphene-based nanomaterials on flexible substrates has become a burgeoning platform for next-generation technologies. Combining graphene and nanoparticles to create hybrid nanomaterials has been proven to boost device performance, thanks to their complementary physical and chemical properties. However, high growth temperatures and long processing times are often required to produce high-quality graphene-based nanocomposites. For the first time, we report a novel scalable approach for additive manufacturing of Sn patterns on polymer foil and their selective conversion into nanocomposite films under atmospheric conditions. A combination of inkjet printing and intense flashlight irradiation techniques is studied. Light pulses that are selectively absorbed by the printed Sn patterns cause a temperature of over 1000 °C to be reached locally in a split second without damaging the underlying polymer foil. The top surface of the polymer foil at the interface with printed Sn becomes locally graphitized and acts as a carbon source, transforming printed Sn into Sn@graphene (Sn@G) core-shell patterns. Our results revealed a decrease in electrical sheet resistance, with an optimal value ( R s = 72 ± 2 Ω/sq) reached when light pulses with an energy density of 12.8 J/cm 2 were applied. These graphene-protected Sn nanoparticle patterns exhibit excellent resistance against air oxidation for months. Finally, we demonstrate the implementation of Sn@G patterns as electrodes for Li-ion microbatteries (LIBs) and triboelectric nanogenerators (TENGs), showing remarkable performance. This work offers new insight into the development of a versatile, eco-friendly, and cost-effective technique for producing well-defined patterns of graphene-based nanomaterials directly on a flexible substrate using different light-absorbing nanoparticles and carbon sources.

New synthesis routes to tailor graphene properties by controlling the concentration and chemical configuration of dopants show great promise. Herein we report the direct reproducible synthesis of 2-3% nitrogen-doped 'few-layer' graphene from a solid state nitrogen carbide a-C:N source synthesized by femtosecond pulsed laser ablation. Analytical investigations, including synchrotron facilities, made it possible to identify the configuration and chemistry of the nitrogen-doped graphene films. Auger mapping successfully quantified the 2D distribution of the number of graphene layers over the surface, and hence offers a new original way to probe the architecture of graphene sheets. The films mainly consist in a Bernal ABA stacking three-layer architecture, with a layer number distribution ranging from 2 to 6. Nitrogen doping affects the charge carrier distribution but has no significant effects on the number of lattice defects or disorders, compared to undoped graphene synthetized in similar conditions. Pyridinic, quaternary and pyrrolic nitrogen are the dominant chemical configurations, pyridinic N being preponderant at the scale of the film architecture. This work opens highly promising perspectives for the development of self-organized nitrogen-doped graphene materials, as synthetized from solid carbon nitride, with various functionalities, and for the characterization of 2D materials using a significant new methodology.

Improving graphene-based electrode fabrication processes and developing robust methods for its functionalization are two key research routes to develop new high-performance electrodes for electrochemical applications. Here, a self-organized three-dimensional (3D) graphene electrode processed by pulsed laser deposition with thermal annealing is reported. This substrate shows great performance in electron transfer kinetics regarding ferrocene redox probes in solution. A robust electrografting strategy for covalently attaching a redox probe onto these graphene electrodes is also reported. The modification protocol consists of a combination of diazonium salt electrografting and click chemistry. An alkyne-terminated phenyl ring is first electrografted onto the self-organized 3D graphene electrode by in situ electrochemical reduction of 4-ethynylphenyl diazonium. Then the ethynylphenyl-modified surface efficiently reacts with the redox probe bearing a terminal azide moiety (2-azidoethyl ferrocene) by means of Cu(I)-catalyzed alkyne-azide cycloaddition. Our modification strategy applied to 3D graphene electrodes was analyzed by means of atomic force microscopy, scanning electron microscopy, Raman spectroscopy, cyclic voltammetry, and X-ray photoelectron spectroscopy (XPS). For XPS chemical surface analysis, special attention was paid to the distribution and chemical state of iron and nitrogen in order to highlight the functionalization of the graphene-based substrate by electrochemically grafting a ferrocene derivative. Dense grafting was observed, offering 4.9 × 10(-10) mol cm(-2) surface coverage and showing a stable signal over 22 days. The electrografting was performed in the form of multilayers, which offers higher ferrocene loading than a dense monolayer on a flat surface. This work opens highly promising perspectives for the development of self-organized 3D graphene electrodes with various sensing functionalities.