29 research outputs found

    Single-step electrodeposition of superhydrophobic black NiO thin films

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    International audienceBlack finished surfaces have extensive applications in many domains, such as optics, solar cells, and aerospace. The single step electrodeposition of superhydrophobic black NiO films from a dimethyl sulfoxide based electrolyte is described in this paper. The physicochemical properties of the obtained film were characterized using Scanning Electron Microscopy, X-ray Diffraction, and electrochemical tests (Electrochemical Impedance Spectroscopy and potentiodynamic polarization). A rough surface with a low reflection of light was formed after the deposition process that increased the contact angle of water from about 87Âș (for bare Cu) to 163Âș (in presence of the black coating), which improved the corrosion resistance of the Cu substrate by about 30%. The formed black NiO film revealed a notably high stability and kept its appearance even after corrosion tests

    Development and tribological characterisation of nanostructured Zn-Ni and Zn-Co coatings: a comparative study

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    International audienceZn-Ni and Zn-Co alloy coatings were electrodeposited on mild steel from sulphate-based baths. The morphology, microstructure, microhardness and tribological behaviours of the coatings have been studied and discussed. While the Zn-5wt-% Co layers presented a nanocrystalline simple nodular structure (45 ± 5 nm), the Zn-14wt-% Ni showed a particular structure called cauliflower morphology (30 ± 7 nm). The X-ray diffraction analysis showed that each of the electrodeposits was formed from zinc solid solution with a uniform zinc-cobalt intermetallic phase γ 2 (CoZn 13) for Zn-5wt-% Co alloy. However, a single γ-phase (intermetallic compound Ni 5 Zn 21) was presented for the Zn-14wt-% Ni alloys. The Zn-14wt-% Ni films were found to be harder and rougher than the Zn-5wt-% Co layers. Plastic deformation and oxide layers production were the main wear mechanisms for the investigated coatings. The Zn-14wt-% Ni coatings were found to have the best wear resistance due to their microhardness and particular structure. ARTICLE HISTOR

    Optical and Electrochemical Properties of Self-Organized TiO2 Nanotube Arrays From Anodized Ti−6Al−4V Alloy

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    Due to their high specific surface area and advanced properties, TiO2 nanotubes (TiO2 NTs) have a great significance for production and storage of energy. In this paper, TiO2 NTs were synthesized from anodization of Ti-6Al-4V alloy at 60 V for 3 h in fluoride ethylene glycol electrolyte by varying the water content and further annealing treatment. The morphological, structural, optical and electrochemical performances of TiO2 NTs were investigated by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), UV-Visible spectroscopy and electrochemical characterization techniques. By varying the water content in the solution, a honeycomb and porous structure was obtained at low water content and the presence of (α + ÎČ) phase in Ti-6Al-4V alloy caused not uniform etching. With an additional increase in water content, a nanotubular structure is formed in the (α + ÎČ) phases with different morphological parameters. The anatase TiO2 NTs synthesized with 20 wt% H2O shows an improvement in absorption band that extends into the visible region due the presence of vanadium oxide in the structure and the effective band gap energy (Eg) value of 2.25 eV. The TiO2 NTs electrode also shows a good cycling performance, delivering a reversible capacity of 82 mAh.g−1 (34 ÎŒAh.cm−2.ÎŒm−1) at 1C rate over 50 cycles

    Des alliages de zinc et de manganĂšse aptes au revĂȘtement protecteur de plaques d’acier

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    Des plaques d’acier ont Ă©tĂ© revĂȘtues d’un dĂ©pĂŽt d’alliage zinc-manganĂšse prĂ©parĂ© Ă  partir d’un bain Ă  base de chlorure d’ammonium. Ces plaques ont Ă©tĂ© exposĂ©es sur le site de corrosion naturelle de Palavas, sur la cĂŽte mĂ©ditĂ©rranĂ©enne, et prĂ©sentent, aprĂšs une durĂ©e d’exposition de 2,5 ans, une couleur brune uniforme sans trace de rouille blanche ou rouge. Les analyses de ces plaques, par diffraction des rayons X, microscopies et spectroscopie photoĂ©lectronique de rayons X (XPS), ont rĂ©vĂ©lĂ© en surface la prĂ©sence d’oxydes de manganĂšse. A ce jour, les plaques sont en conditions de corrosion naturelle depuis 4,5 ans et aucun changement visuel n’est observĂ©

    Mécanisme d'action d'additifs utilisés lors de l'électrocristallisation de cuivre confiné dans des matrices poreuses (étude par méthodes électrochimiques classiques couplées à la microbalance à quartz)

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    Dans ce travail, nous avons Ă©tudiĂ© les mĂ©canismes d'Ă©lectrocristallisation du cuivre Ă  partir d'une solution acide de sulfate de cuivre en prĂ©sence de trois additifs : les ions C1-, le polyĂ©thylĂšne glycol (PEG10000), le 3-mercapto-1-propane sulfonate de sodium (MPSA). L'Ă©tude Ă©lectrochimique classique (voltamĂ©trie cyclique, mĂ©thodes potentiostatiques et galvanostatiques ) a e tĂ© couplĂ©e Ă  des analyses de variation de masse par microbalance Ă©lectrochimique Ă  quartz (EQCM). Des mĂ©thodes non Ă©lectrochimiques (DRX, EDAX, MEB, AFM) ont permis en outre de prĂ©ciser la composition des dĂ©pĂŽts Ă©pais de cuivre et d'observer les changements de morphologie et de texture induits par l'ajout des additifs. AprĂšs l'Ă©tude de l'action individuelle de chaque additif sur les mĂ©canismes d'Ă©lectrodĂ©position et de dissolution du cuivre, nous avons Ă©valuĂ© l'effet de la combinaison des additifs en solution. Ainsi l'ajout simultanĂ© de PEG et C1-, via un mĂ©canisme d'adsorption active, provoque une inhibition de la cristallisation du cuivre avec diminution de la rugositĂ© par rapport au dĂ©pĂŽt de cuivre massif sans additif et une amĂ©lioration de l'homogĂ©nĂ©itĂ©. En prĂ©sence des trois additifs, le mĂ©canisme de rĂ©duction des ions cuivriques se dĂ©roule en deux Ă©tapes : une action catalytique induite par MPSA et un effet inhibiteur Ă  travers les sites bloquĂ©s par la couche PEG-C1-.Un tel mĂ©canisme est attendu lors des procĂ©dĂ©s d'Ă©lectrodĂ©position au travers de structures poreuses isolantes (par le procĂ©dĂ© damascĂšne) : un inhibiteur bloque la surface et un catalyseur accĂ©lĂšre la dĂ©position au fond des pores. Le but ultime de ce travail a Ă©tĂ© de dĂ©poser des nanofils de cuivre Ă  travers des moules d'alumine nanoporeuse. Les matrices d'alumine ont Ă©tĂ© prĂ©parĂ©es par anodisation en deux Ă©tapes de feuilles d'aluminium massif, puis caractĂ©risĂ©es. Elles prĂ©sentent des pores rĂ©guliers et hexagonaux de diamĂštre de 50 nm qui peuvent ĂȘtre Ă©largis et dĂ©collĂ©s du substrat d'aluminium non anodisĂ© sous jacent. Cependant la fragilitĂ© des membranes d'alumine et l'agressivitĂ© de notre solution d'Ă©tude n'ont pas permis de dĂ©poser rĂ©guliĂšrement du cuivre au travers.AIX-MARSEILLE1-BU Sci.St Charles (130552104) / SudocSudocFranceF

    Amélioration des propriétés de corrosion de film minces de NiP par utilisation de différents additifs

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    International audienceNiP amorphous coatings are considered as important engineering alloys. In this paper, the effects of various additives on the properties of NiP thin films were investigated, including saccharine, glycine, pyridinium propyl sulfonate, coumarin, sodium citrate, and cerium sulfate. Potentiodynamic polarization and electrochemical impedance spectroscopy tests, scanning electron microscopy, X-ray fluorescence and diffraction, and atomic force microscopy were employed to study the properties of the samples. It was found that a proper concentration of these additives, except saccharine, noticeably improved the corrosion resistance, especially at high potentials (about 25% increase in instantaneous corrosion efficiency and about 300% in corrosion efficiency at high potentials) and decreased the surface roughness (by about 10 to 55 %) of NiP thin films. Thinner, more uniform, and less porous coatings were formed in the presence of additives. Except saccharine, all the additives enhanced the P content of NiP films, which thus kept their amorphous structure; saccharine highly suppressed the incorporation of P inside the Ni lattice and a mixed amorphous-crystalline structure was stabilized
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