Monthly Archives: February 2013

Microstructure and Particle Incorporation Behavior of Electrocodeposited Ni-Al2O3 Nanocomposites


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Nickel-alumina composite films were obtained by electrocodeposition using different deposition techniques, viz. direct current (DC) deposition and pulse-reverse plating (PRP). Particle incorporation was determined by means of energy-dispersive X-ray spectroscopy and glow discharge optical emission spectrometry (GD-OES). The structure of the films was analyzed using electron microscopy, viz. scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and X-ray diffraction. A <100> fiber texture was found for pure nickel films, which was reduced due to a change in plating conditions and particle incorporation. EBSD mappings indicate that the nanosized particles inhibit nickel growth and thus lead to a smaller nickel crystallite size combined with a distinct loss of the <100> texture. Scanning transmission electron microscopy (STEM) and TEM reveal that the inclusion of alumina nanoparticles preferentially takes place in the grain boundary region where the particles terminate the growth of nickel. High-resolution TEM imaging proves a complete embedding of nanoparticles by the nickel matrix without any voids.

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Electrochemical Deposition and Microstructure Characterization of Lead-Tin-Layers


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Fig. 3

The present study investigated the formation of a binary alloy of lead and tin. Both elements represent a thermodynamic system with strongly limited miscibility in solid state. The deposition of the layers was carried out under potentiostatic conditions at various deposition potentials from a sulfonate-based electrolyte. The layer formation was characterized by electrochemical techniques (cyclovoltammetry, chronoamperometry). The microstructure development was investigated by SEM/EDX measurements and X-ray diffraction. The layer formation is compliant with the Stranski-Krastanov growth mode. The current efficiency of the deposition was approximately 100%. According to the thermodynamic theory the layers show a dual-phase microstructure. The composition of the Pb-Sn layers was depending on the deposition potential. Supersaturated α-Pb-solid solution could not be observed. The morphology is also strongly depending on the deposition potential. The diffusion coefficient of the metal ions in the sulfonat-based electrolyte was measured by rotating disc electrode experiments. The formal diffusion coefficient in the electrolyte containing Pb2+– and Sn2+– ions is close to the diffusion coefficient of lead ions.

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