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.

Na 2 SO 4 -induced accelerated oxidation (hot corrosion) of nickel

Abstract: The Na2SO4-induced accelerated oxidation of nickel has been studied at 1000°C. It has been found that low oxygen activities in the Na2SO4, which are produced by the formation of NiO, cause the sulfur activity of the Na2SO4 to be increased. Nickel and sulfur from the Na2SO4 combine to form nickel sulfide and the oxide ion activity of the Na2SO4 is increased. The accelerated oxidation of nickel occurs because oxide ions react with NiO to form a nonprotective oxide scale. The accelerated oxidation of nickel is not self-sustaining since oxide ions are not produced when conditions in the Na2SO4 are no longer favorable for the formation of nickel sulfide.

Preparation and properties of ferromagnetic carbon‐coated Fe, Co, and Ni nanoparticles

Abstract: Carbon‐coated iron, cobalt, and nickel particles were produced by an arc discharge process modified in the geometry of the anode and the flow pattern of helium gas. Field emission scanning electron microscopy shows that the resulting material consists of only carbon‐coated metal particles without any nanotubes or other unwanted carbon formations present. The diameters of iron, cobalt, and nickel particles range predominantly from 32 to 81 nm, 22 to 64 nm, and 16 to 51 nm, respectively. X‐ray diffraction analysis confirmed that the as‐made particles are carbon‐coated elements rather than metal carbides. High resolution transmission electron microscopy reveals that the as‐made cobalt and nickel particles are covered by 1–2 graphitic layers, while iron particles are surrounded by amorphous carbon. When the samples were treated by annealing or immersion into nitric acid, particles completely coated by carbon resisted both postdeposition treatments. However, further graphitization of the carbon coating by eith...

Transition metal adatom and dimer adsorbed on graphene: Induced magnetization and electronic structures

Abstract: Geometries, electronic structures, and magnetic properties of transition metal $M$ adatom and dimer adsorbed graphene have been studied ($M=\text{Fe}$, Co, Ni, and Cu). With adatom adsorption, we confirm the previously reported stable adsorption site, and the adatoms are chemically bonded with graphene except the copper adatom. With dimer adsorption, we observed that the stable configurations are dependent on the exchange-correlation functional for the iron dimer and nickel dimer; while the stable configurations do not depend on the functional for the cobalt and copper dimer. The adsorption energy indicates the copper dimer can barrierlessly diffuse along the graphene C-C bonds. With iron or cobalt adatom adsorption, graphene becomes a half-metal which can be used as a spin-filtering material. The iron dimer adsorbed graphene is also a half-metal, but the cobalt dimer adsorbed graphene is not. Both local-density approximation and generalized gradient approximation yield consistent results for the nickel adatom adsorbed graphene, which is the system is semiconducting and nonmagnetic due to the strong binding between nickel and graphene. However, different exchange-correlation functionals lead to controversial results for the magnetic and transport properties of nickel dimer adsorbed graphene. The copper adatom adsorbed on graphene exhibits $1{\ensuremath{\mu}}_{B}$ local magnetic moment, but the dimer does not show any magnetism. These results show that graphene properties can be effectively modulated by transition metal adsorption and that the transition metal adsorbed graphene can serve as potential materials in nanoelectronics, spintronics, or electrochemistry.

Hydrogenation of nitrophenols catalyzed by carbon black-supported nickel nanoparticles under mild conditions

Abstract: A carbon black (CB) supported nano-Ni catalyst is prepared by a facile method using nickel chloride as the nickel source and hydrazine hydrate as the reducing agent. TEM observation shows that Ni nanoparticles have a good dispersion with a narrow size distribution on the surface of carbon black. The catalyst exhibits significantly high catalytic activity for hydrogenation of nitrophenols even at 30 °C. The high performance obtained here can be attributed to the specific characteristics of the nanostructure of the catalyst and the synergistic effect of nano-Ni and carbon black, including plenty of oxygen-containing groups of carbon black for anchoring Ni atoms, strong adsorption ability for organic molecules and good conductivity for electron transfer from the carbon black to Ni nanoparticles. Moreover, the Ni-based catalyst is relatively cheap and magnetically separable, thus achieving a low-cost hydrogenation of nitrophenols to aminophenols.