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Journal ArticleDOI

Influence of mode of electrodeposition, current density and saccharin on the microstructure and hardness of electrodeposited nanocrystalline nickel coatings

TL;DR: In this article, the influence of current density, deposition mode and the presence of saccharin as an additive on the microstructure, sulfur content, grain size and microhardness of nanocrystalline Ni coatings was studied.
Abstract: The main purpose of the present work is to study the influence of current density, deposition mode and the presence of saccharin as an additive on the microstructure, sulfur content, grain size and microhardness of nanocrystalline Ni coatings. Towards this purpose, nanocrystalline nickel (Ni) coatings were deposited at various current densities in Watt's bath using direct, pulse and pulse reverse current (PRC) electrodeposition and subsequently characterized for sulfur content, grain size and hardness. It was observed that, the current density has no influence on the grain size/hardness of nanocrystalline Ni coatings in direct and pulsed current electrodeposition mode. However, the grain size increased from ~ 20 to ~ 200 nm with decrease in current density in PRC mode of deposition. In addition a substantial change in microstructure and texture of PRC Ni coatings was also evident. The experimental results have been rationalized based on the adsorption–desorption type of mechanism during electrodeposition.
Citations
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Journal ArticleDOI
TL;DR: In this article, a simplified mechanism of composite electrodeposition is proposed to account for the incorporation of SiC was attributed to pulse current effect at cathode-solution interface leading to changes in pulsating diffusion layer thickness.

141 citations

Journal ArticleDOI
TL;DR: Li et al. as discussed by the authors fabricated a metal-insulator-semiconductor structure of NiOx/Ni/n-Si photoanodes for highly efficient water splitting, which showed highly enhanced charge separation and transport efficiency.
Abstract: Converting solar energy by photoelectrochemical water splitting has been regarded as a promising way to resolve the global energy crisis and alleviate environmental pollution. Silicon, which is earth-abundant and has a narrow band gap, is an attractive material for photoelectrochemical water splitting. However, Si-based photoelectrodes suffer from photocorrosion, which leads to instability in electrolytes and high overpotential. Herein, we have fabricated a metal–insulator–semiconductor structure of NiOx/Ni/n-Si photoanodes for highly efficient water splitting. NiOx/Ni nanoparticles, which act as well-known oxygen evolution catalysts, are deposited on the surface of silicon by facile pulsed electrodeposition. Light absorption and catalytic activity are greatly affected by the coverage of Ni nanoparticles, and the highly efficient NiOx/Ni catalyst structure is induced by simple annealing. The NiOx/Ni nanoparticles show highly enhanced charge separation and transport efficiency, which are vital factors for ...

74 citations

Journal ArticleDOI
TL;DR: In this article, the authors deal with the electrodeposition and structural characterization of as-deposited and heat treated nickel-tungsten (Ni-W) alloy coatings.
Abstract: The present study deals with the electrodeposition and structural characterization of as-deposited and heat treated nickel-tungsten (Ni-W) alloy coatings. The coatings were deposited using pulse reverse electrodeposition (PRED) and pulse electrodeposition (PED) from a Ni-W plating bath. Wide range of alloy compositions have been obtained with tungsten (W) percentage in the alloy ranging from 0% to 25 at% by altering pulse parameters. The coatings were subsequently heat treated at a temperature of 700 °C for 1 h and were characterized in terms of phases present, grain size, hardness and elastic modulus. It was observed that the coatings were crystalline up to 12 at% W and beyond which the coatings were found to be a mixture of amorphous and crystalline phases. Heat treatment resulted in crystallization of amorphous phase and precipitation of secondary phases. Substantial grain growth had occurred after heat treatment and as a result, the hardness of heat treated coatings was found to be less than that of their as-deposited counterparts up to 17 at% W. Beyond 17 at% W hardness of heat treated Ni-W was found to be higher due to dispersion hardening.

56 citations

Journal ArticleDOI
TL;DR: In this article, the influence of molybdenum (Mo) content on the grain size, hardness, corrosion and wear behavior of Ni-Mo alloy coatings electrodeposited from citrate electrolyte has been studied.
Abstract: In the present work, the influence of molybdenum (Mo) content on the grain size, hardness, corrosion and wear behavior of Ni-Mo alloy coatings electrodeposited from citrate electrolyte has been studied. Crack free Ni-Mo alloy with different Mo content (3, 5, 6, 9 and 12 at.%) was obtained using direct current and pulsed current electrodeposition. It was observed that the grain size of Ni-Mo alloy decreased with increase in Mo content. Hardness of the coatings increased with Mo content and decreased subsequently above 9 at.% Mo as per inverse Hall-Petch effect. Potentiodynamic polarization tests carried out in 2 N H2SO4 suggested increase in both corrosion current and passive current density with increase in Mo content. In addition, both friction coefficient and dry sliding wear rate of Ni-Mo coatings decreased with increase in Mo content. The results are rationalized based on grain size and Mo content in the coatings. Finally, Ni-Mo and Ni-W coatings were compared with hard chrome with respect to mechanical properties, wear and corrosion resistance. Results indicated that, Ni-Mo coatings exhibit least friction coefficient (0.2–0.3) amongst Ni-W and hard chrome coatings.

48 citations

Journal ArticleDOI
TL;DR: In this paper, the wear behavior of Ni-14 at.% W/SiC nanocomposite was analyzed under dry sliding wear test conditions using pin on disk method and the interrelationship between SiC content, interparticle spacing, mechanical properties and wear behavior was analyzed.
Abstract: Ni-14 at.% W/SiC nanocomposite coatings containing 0-6 vol.% of submicron size (0.35 μm) SiC particles were obtained using pulsed electrodeposition technique on mild steel substrate. The coatings were subsequently characterized for uniformity of SiC distribution, grain size and mechanical properties (hardness and elastic modulus) using SEM, XRD and nanoindentation techniques, respectively. It was observed that the SiC particulates were uniformly distributed within the coating. The coating matrix (Ni-W) also exhibited nanograin size. Tribological behavior of Ni-14 W/SiC nanocomposite was analyzed under dry sliding wear test conditions using pin on disk method. The interrelationship between SiC content, interparticle spacing, mechanical properties and wear behavior was analyzed. The results suggest that whereas hardness and modulus of nanocomposite coatings varied with SiC content as per Rule of Mixtures, wear mechanism can be best explained on the basis of Inverse Rule of Mixtures.

45 citations

References
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Book
01 Jan 2001

19,319 citations

Journal ArticleDOI
TL;DR: The mechanical properties of nanocrystalline materials are reviewed in this paper, with emphasis on their constitutive response and on the fundamental physical mechanisms, including the deviation from the Hall-Petch slope and possible negative slope, the effect of porosity, the difference between tensile and compressive strength, the limited ductility, the tendency for shear localization, fatigue and creep responses.

3,828 citations

Journal ArticleDOI

2,605 citations

Book
20 Oct 2011
TL;DR: In this paper, the structure of the metal-solution interface is discussed and the potential distribution in the volume of solution and current distribution on the electrode surface is analyzed. But the current density distribution on rough surfaces is not discussed.
Abstract: Basic terms and concepts.- The structure of the metal-solution interface.- Electrochemical thermodynamics and electrochemical kinetics.- Influence of diffusion on the rate of electrochemical process.- Nucleation.- Morphology of the growing metal surface.- Potential distribution in the volume of solution and current distribution on the electrode surface.- Current density distribution on rough surfaces.- Using of pulse and periodic currents in electrodeposition and in electrochemical experiments.- Electrodeposition of alloys.- Codeposition of impurities. Hydrogenation.- Technologies for deposition of several metals and alloys.- Structure of electrodeposited metals and alloys.- Physical properties of deposited macrolayers of metals and alloys. Control of quality and testing methods.- Conclusion

340 citations

Journal ArticleDOI
TL;DR: In this article, the grain boundary segregation of Ni-W alloys has been investigated and it has been shown that the W content controls the grain size over a very broad range: ∼2-140nm.

297 citations