A comparative study on the crystallization behavior of electroless NiP and NiCuP deposits
ABSTRACT The crystallization behavior of electroless NiP and NiCuP was studied comparatively by using differential scanning calorimetry and X-ray diffractometry. It is apparent that low-P NiP deposits transform to the stable phase Ni3P directly, but low-P (high-Cu) NiCuP deposits transform to the metastable phase Ni5P2 first, and then to the stable Ni3P. Both the hypereutectic amorphous NiP deposits and amorphous NiCuP deposits with high phosphorus content transform to the metastable phases Ni5P2 and Ni12P5 first, then to the stable phase Ni3P. For the amorphous NiP and NiCuP deposits with P content of approximately 10 wt.%, the crystallization temperature of the latter is markedly higher than that of the former. In addition, the crystallization temperature of the hypereutectic NiP deposit is nearly the same as that of the amorphous NiCuP deposit with a similar P content. For the crystalline NiP and NiCuP deposits with low P content, the temperature at which the stable Ni3P forms in the latter is obviously higher than that of the former.
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ABSTRACT: Electroless nickel coated fibres have been used as reinforcement for the fabrication of aluminium matrix composites by liquid processing. Uniform, continuous and well-adhered nickel coatings are obtained with different phosphorus contents. Coated carbon fibres were mixed with AA6061 aluminium powders, compacted and heated at temperatures from 650 to 950 °C to study the reactivity, the nickel diffusion, and the resulting interfaces. Coatings improve the wetting behaviour of carbon fibres by molten aluminium because of the formation of a transient Al–Ni intermetallic at the matrix–fibre interface, limiting fibre segregation to obtain a homogeneous reinforcement distribution. Finally, the mechanical properties of the composite have been measured through nanoindentation tests.Composites Part A: Applied Science and Manufacturing. 01/2007;
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ABSTRACT: Electroplating technique was applied to coat carbon fibers with nickel. Before plating, the initial fibers were pretreated to improve the wettability in bath. The electroplating parameters were optimized to obtain high-quality nickel-coated carbon fibers, and the effects on plating were studied. The coated carbon fibers were characterized by SEM, XRD, and XPS. The coatings are uniform, smooth, bright, and adherent to carbon fibers not only along length but also along the diameter of the filaments, and mainly composed of pure nickel. Metal-carbon-oxygen bonds are present at the interface between nickel coatings and fibers, which provides the interfacial binding force. The results of performance tests showed that the nickel-coated fibers possess a good bonding strength not less than 78.5kPa, and exhibit excellent oxidation resistance at high temperature. Compared with the initial fibers, the wettability with aluminum is also improved obviously. Keywordsadvanced characterization–carbon fibers–coatings–electron microscopy–electroplating–nickelJournal of Materials Engineering and Performance 01/2012; 21(3):324-330. · 0.92 Impact Factor
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ABSTRACT: Amorphous Ni–P coating was plated on AZ31 magnesium alloy via the electroless plating technique, and the plated alloy was subsequently annealed. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and differential scanning calorimetry (DSC) were used to characterize the coating. The results show that the hardness of the coating is much higher than that of bare magnesium alloy, which further increases after crystallization. The electrochemical polarization and salt spray tests show that the coating exhibits a much higher corrosion resistance than that of the bare magnesium alloy. Moreover, the crystallized coating still exhibits a much stronger corrosion resistance than that of the bare magnesium alloy, although its corrosion resistance is lower than that of the as-plated one.Rare Metals · 0.49 Impact Factor