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Abstract Carbon-alumina coatings on stainless steel were prepared by a sol-gel route. The dispersion of the commercial graphite flakes by an ultrasonic bath, an ultrasonic probe and a high-shear mixer, produce thinner flakes, few-layered-graphene and bi-layer-graphene (BLG), respectively. The coatings were examined by optical and electron microscopy, interferential rugosimetry, optical profilometry and Raman spectroscopy. The friction coefficient against a steel ball is decreased by a factor of 5–7 and the wear volume is reduced by a factor of 6–38 compared to a pure alumina coating. The best results correspond to the sample prepared using the high-shear mixer. Delamination of the graphite flakes into BLG during the friction test provides the system with debris suitable for tribofilm building up and lubrication but it is better to already have carbon dispersed as BLG in the coating before the test, notably because the carbon surface area available is much higher. [ABSTRACT FROM AUTHOR]

The chemical vapor deposition of carbon is performed onto a commercial silicon nitride powder bed. This produces few-layered-graphene (FLG) films or islands on the Si 3 N 4 particles. The samples are characterized by several techniques including Raman spectroscopy, scanning and transmission electron microscopy. The experimental parameters of the methane (CH 4) decomposition (temperature, CH 4 concentration, dwell time) are correlated to the average number of graphene layers (N). Complete coverage of the Si 3 N 4 particles is achieved for FLG with N controlled in the range 5–12, corresponding to 4–12 wt%. of carbon. Below that, for stacks with N = 3–4, the coverage of the surface by FLG islands is not total. The value found for the activation energy of CH 4 conversion into carbon shows that island-growth is favored over layer-growth. A macroscopical method based on a carbon proportion evaluation gives an approximation of both the coverage ratio and the average number of layers in the stack. • Few-layered-graphene (FLG) deposited on the surface of Si 3 N 4 particles, without any mixing and damaging the nanocarbons. • Complete coverage of the Si 3 N 4 particles is achieved for FLG with the average number of graphene layers in the range 5-12. • Below that range, the Si 3 N 4 particles are covered by FLG islands 3-4 layers thick. • The activation energy of CH 4 conversion into carbon shows that island-growth is favored over layer-growth. • A macroscopical carbon content evaluation gives a good approximation of the coverage ratio and the average number layers. [ABSTRACT FROM AUTHOR]

In this study, Triton X-100 was used as the WS 2 dispersion agent in the Au–Co cyanide electrolyte to deposit Au–Co/WS 2 composite coatings. Probe sonication was applied to exfoliate the commercial WS 2 powders to produce thinner and smaller WS 2 flakes, which improved the stability of the WS 2 particles in the electrolyte. According to the electrochemical analyses, the effects of adding Triton X-100 and WS 2 particles to the electroplating process were investigated. Through material characterizations, WS 2 particles were proved to be compounded into the Au–Co matrix and showed clearly {002} preferred orientation due to their flake structures. Tribological tests were performed under dry condition in 10−3 Pa vacuum against stainless steel 316L balls with diameters of 3 mm and a normal contact force of 2 N. The Au–Co/WS 2 composite coatings that developed showed the minimum coefficient of friction and wear rate of 0.05 and 8 × 10−6 mm3/N·m, which are 5 times and 3 times lower than the Au–Co reference coating, respectively. • Cyanide electrolyte for Au–Co/WS 2 composite coating deposition was developed. • WS 2 dispersion stability was improved efficiently by applying probe sonication and Triton X-100 surfactant. • Effects of adding WS 2 and surfactant on the deposition process and coating properties were investigated. • The Au–Co/WS 2 composite coating has a low coefficient of friction (0.05) and wear rate (8 × 10−6 mm3/N∙m). [ABSTRACT FROM AUTHOR]

Bi-functional water-soluble polymers have been investigated as bonding layers (BL) on aluminum surfaces to promote the adhesion of adhesives for structural bonding applications in the automotive sector. The BLs are located at the interface between two parts: the aluminum substrate and the adhesive (an epoxy-dicyandiamide). The formation and the morphology are studied mainly by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Many process parameters have been investigated such as: i) long or short immersion time in the treatment baths containing the polymers, ii) formulation using three different concentrations. The performances of the BLs under these different operating conditions are evaluated via several mechanical tests: micro-scratch, three-point bending, single lap shear. Results were compared with results obtained with already existing products, launched for the same application, surface treatment prior to structural adhesive bonding of aluminum in transportation. [ABSTRACT FROM AUTHOR]

Abstract: NaSICON-type lithium conductor Li1.3Al0.3Ti1.7(PO4)3 (LATP) is synthesized with controlled grain size and composition using solution chemistry. After thermal treatment at 850°C, sub-micronic crystallized powders with high purity are obtained. They are converted into ceramic through Spark Plasma Sintering at 850–1000°C. By varying the processing parameters, pellet with conductivities up to 1.6×10−4 S/cm with density of 97% of the theoretical density have been obtained. XRD, FEG-SEM, ac-impedance and Vickers indentation were used to characterize the products. The influence of sintering parameters on pellet composition, microstructure and conductivity is discussed in addition to the analysis of the mechanical behavior of the grains interfaces. [Copyright &y& Elsevier]

Abstract: An organic–inorganic hybrid coating was developed to improve the corrosion resistance of the aluminum alloy AA 2024-T3. Organic and inorganic coatings derived from glycidoxypropyl-trimethoxysilane (GPTMS) and aluminum tri-sec-butoxide Al(OsBu)3, with different cerium contents, were deposited onto aluminum by dip-coating process. Corrosion resistance and mechanical properties were investigated by electrochemical impedance measurements and nano-indentation respectively. An optimal cerium concentration of 0.01M was evidenced. To correlate and explain the hybrid coating performances in relation to the cerium content, NMR experiments were performed. It has been shown that when the cerium concentration in the hybrid is higher than 0.01M there are important modifications in the hybrid structure that account for the mechanical properties and anti-corrosion behavior of the sol–gel coating. [Copyright &y& Elsevier]