Nickel

About: Nickel is a research topic. Over the lifetime, 79308 publications have been published within this topic receiving 1210058 citations. The topic is also known as: Ni & element 28.

Pulse electrodeposition of nanocrystalline nickel using ultra narrow pulse width and high peak current density

Abstract: The synthesis of nanocrystalline nickel by electrodeposition has been studied for more than 10 years. However, most attention has been on the adjustment of bath composition or development of new chemical additives. In this paper, a new method was developed to synthesize bulk nanocrystalline nickel without using any additives. Pulse plating with ultra narrow pulse width and high peak current density was employed to increase the deposition current density and the nucleation rate. At an on-time of 10 μs and an off-time of 90 μs, it was found that different surface morphologies, grain sizes, textures, and hardness were obtained at different current densities. Grain sizes ranging from 50 to 200 nm were obtained when the current density varied from 300 to 60 A dm −2 . The preferred orientation of the nickel deposit changed from a weak (2 0 0) fiber texture to a strong (2 0 0) fiber texture when the peak current density increased from 40 to 100 A dm −2 . It was obtained however that the intensity of the (2 0 0) fiber orientation decreased when there was a further increase in the current density. The hardness of the nickel deposit was also found to increase with increasing peak current density when it changed from 20 to 150 A dm −2 , but the hardness tended to decrease when the current density was above 150 A dm −2 . These experimental findings are considered to relate to the change in cathodic overpotential which affects both the grain size, the internal stress, the porosity, and the preferred orientation.

One-electron oxidized nickel(II)-(disalicylidene)diamine complex: Temperature-dependent tautomerism between Ni(III)-phenolate and Ni(II)-phenoxyl radical states

Abstract: The one-electron oxidized species of a Ni(II)-phenolate complex has been shown to be in the Ni(II)-phenoxyl radical state at room temperature and the Ni(III)-phenolate state at < -120 degrees C, indicating that the oxidation state is temperature dependent.

Nickel-tungsten carbide catalysts for the production of 2,5-dimethylfuran from biomass-derived molecules.

Abstract: The development of new catalytic systems for the conversion of biomass-derived molecules into liquid fuels has attracted much attention. We propose a non-noble bimetallic catalyst based on nickel-tungsten carbide for the conversion of the platform molecules 5-(hydroxymethyl)furfural into the liquid-fuel molecule 2,5-dimethylfuran (DMF). Different catalysts, metal ratios and reaction conditions have been tested and give rise to a 96% yield of DMF. The catalysts have been characterized and are discussed. The reaction mechanism is also explored through capture of reaction intermediates. The analysis of the reaction mixture over different catalysts is presented and helps to understand the role of nickel and tungsten carbide during the reaction.

Comparative carcinogenic effects of nickel subsulfide, nickel oxide, or nickel sulfate hexahydrate chronic exposures in the lung.

Abstract: The relative toxicity and carcinogenicity of nickel sulfate hexahydrate (NiSO 4 ·6H 2 O), nickel subsulfide (Ni 3 S 2 ), and nickel oxide (NiO) were studied in F344/N rats and B6C3F 1 mice after inhalation exposure for 6 h/day, 5 days/week, for 2 years. Nickel subsulfide (0.15 and 1 mg/m 3 ) and nickel oxide (1.25 and 2.5 mg/m 3 ) caused an exposure-related increased incidence of alveolar/bronchiolar neoplasms and adrenal medulla neoplasms in male and female rats. Nickel oxide caused an equivocal exposure-related increase in alveolar/bronchiolar neoplasms in female mice. No exposure-related neoplastic responses occurred in rats or mice exposed to nickel sulfate or in mice exposed to nickel subsulfide. These findings are consistent with results from other studies, which show that nickel subsulfide and nickel oxide reach the nucleus in greater amounts than the do water-soluble nickel compounds such as nickel sulfate. It has been proposed that the more water-insoluble particles are phagocytized, whereas the vacuoles containing nickel migrate to the nuclear membrane, where they release nickel ions that effect DNA damage. The findings from these experimental studies show that chronic exposure to nickel can cause lung neoplasms in rats, and that this response is related to exposure to specific types of nickel compounds.