Ultrafine Nickel Research Articles

Preparation and Thermal Stability of Ultrafine Nickel Powders Containing hcp-Ni Nanocrystallites Using Liquid-Phase Reduction Method

Ultrafine nickel powders containing hexagonal close-packed nickel (hcp-Ni) nanocrystallites were prepared using liquid-phase reduction with NiC2O4, NaOH, polyvinylpyrrolidone (PVP), and ethylene glycol (EG). The nickel powders were characterized by XRD and SEM. TG analysis was used to determine the thermal stability of ultrafine nickel powders. The results showed that nickel powders with 45.1 pct of hcp-Ni nanocrystallites were synthesized under the following conditions: a reflux time of 3 hours, an NiC2O4-to-EG molar ratio of 0.01, 5 g/L PVP, and 85 g/L NaOH. SEM results illustrated that spherical particles of size 500 nm were obtained. The results of thermal stability showed that the antioxidant property at high temperature was improved with the increase of hcp-Ni content. The oxidation rate of nickel powders with 43.3 pct hcp-Ni was less than 50 pct even if the temperature was up to 873 K (600 °C).

Magnetic NiFe2O4 nanoparticles: efficient, heterogeneous and reusable catalyst for synthesis of acetylferrocene chalcones and their anti‐tumour activity

A robust synthesis of magnetic NiFe2O4 nanoparticles via a hydrothermal technique was investigated. The prepared magnetic NiFe2O4 nanoparticles were characterized using powder X‐ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), high‐resolution TEM, energy‐dispersive X‐ray spectroscopy, thermogravimetric analysis, infrared spectroscopy and vibrating sample magnetometry. XRD and TEM analyses confirmed the formation of single‐phase ultrafine nickel ferrite nanoparticles with highly homogeneous cubic shape and elemental composition. Moreover, the prepared magnetic NiFe2O4 nanoparticles were used as an efficient, cheap and eco‐friendly catalyst for the Claisen–Schmidt condensation reaction between acetylferrocene and various aldehydes (aromatic and/or heterocyclic) yielding acetylferrocene chalcones in excellent yields, with easy work‐up and reduced reaction time. The products were purified via crystallization. The structures of the produced compounds were elucidated using various spectroscopic analyses (1H NMR, 13C NMR, GC–MS). The catalyst is readily recovered by simple magnetic decantation and can be recycled several times with no discernible loss of catalytic activity. Furthermore, the prepared chalcone derivatives were evaluated for their anti‐tumour activity against three human tumour cell lines, namely HCT116 (colon cancer), MCF7 (breast cancer) and HEPG2 (liver cancer), and showed a good activity against colon cancer. Copyright © 2016 John Wiley & Sons, Ltd.

Electrodes from carbon nanotubes/NiO nanocomposites synthesized in modified Watts bath for supercapacitors

Abstract A modified Watts bath coupled with pulsed current electroplating is used to uniformly deposit ultrafine nickel oxide particles (diameter

In situ embedding of ultra-fine nickel oxide nanoparticles in HMS with enhanced catalytic activities of styrene epoxidation

In this paper, a new templating assemble route (S0M+I−) was proposed to construct a nickel-based mesoporous silica catalyst. During this method, the neutral surfactant dodecyl amine was used as a special agent for both capturing the metal ions and structure-directing of the mesoporous silica. Based on the templating assemble route, metal cations were highly enriched in the interface of micelles and silicate wall by the physiochemical interaction among the surfactant (S0), metal cations (M+, Ni2+) and silicate oligomers (I−). Besides, instead of original hydrogen-bonding, the addition of metal cations in the assemble process made the interaction between micelles and silicate oligomers improved significantly through the counterion-mediated interaction. According to these effects, highly-dispersed, ultra-fine and accessible nickel oxide nanoparticles (NPs) were in situ produced and embedded in the channels and the exposed level of the active sites on these NPs would reach to the highest. Moreover, as expected, the synthesized catalyst exhibited superior catalytic activities for the epoxidation of styrene.

Ultrafine nickel–copper carbonate hydroxide hierarchical nanowire networks for high-performance supercapacitor electrodes

In this work, ultrafine nickel–copper carbonate hydroxide nanowire arrays on copper foam are synthesized via a facile hydrothermal method without any adscititious surfactant and binder. The fabricated nickel–copper carbonate hydroxide hierarchical nanowire networks electrodes for supercapacitors in aqueous electrolyte exhibit a significantly enhanced specific capacitance (971Fg−1 at 1Ag−1) and energy density (48.55Whkg−1 at 541Wkg−1). Meanwhile, the nickel–copper carbonate hydroxide hierarchical nanowire networks as electrode materials have excellent long-life cycling stability, retaining 91.5% of the initial capacitance after 2000 cycles. Thereby, the nickel–copper carbonate hydroxide hierarchical nanowire networks are promising electrode materials for high-energy-density long-life cycling supercapacitor application.

Ultrafine nickel–cobalt alloy nanoparticles incorporated into three-dimensional porous graphitic carbon as an electrode material for supercapacitors

A facile method was developed to synthesize ultrafine Ni–Co alloy nanoparticles embedded into 3D porous graphitic carbon, an excellent electrode material for supercapacitors.

Ultrafine nickel oxide quantum dots enbedded with few-layer exfoliative graphene for an asymmetric supercapacitor: Enhanced capacitances by alternating voltage

A green and one-step method of electrochemical alternating voltage has been utilized to form NiO quantum dots/graphene flakes (NiO-dots/Gh) for supercapacitor applications. NiO quantum dots (∼3 nm) are uniformly deposited on few-layer graphene surfaces by oxygen functional groups on graphene surface that is naturally utilized to bridge NiO and graphene through Ni–O–C bands, which exhibits outstanding specific capacitance 1181.1 F g−1 at a current density of 2.1 A g−1 and rate behavior 66.2% at 42 A g−1 as NiO dots can be fleetly wired up to current collector through the underlying graphene two-dimensional layers. The NiO-dots/Gh composite is further undertaken in asymmetric supercapacitors with high energy density (27.3 Wh kg−1 at 1562.6 W kg−1).

Influence of the size of inclusions of ultrafine nickel particles on the laser initiation threshold of PETN

We investigated the probability of explosion of tetranitropentaerythrite (ρ = 1.73 g/cm3) containing 0.1% (by weight) ultrafine nickel particles of size 270–300 and 140–175 nm at the distribution maxima depending on the energy density of the initiating laser pulse (1064 nm, 14 ns). In the first case, the critical energy density corresponding to a 50%th probability of explosion was 1.4 J/cm2, and in the second case, 0.7 J/cm2. Dependences of the light absorption cross section and the absorption coefficient on the inclusions particle size were calculated using the microhotspot theory of laser ignition. The calculation results are consistent with the microhotspot model of the initiation of thermal explosion.

Nickel Oxide Nanoclusters for Electrocatalytic Water Oxidation

The growth and/or deposition of uniformly dispersed nanoclusters is a significant challenge for the field of electrocatalysis science. Here we employ ALD technique to obtain ultrafine nickel oxide nanoclusters uniformly dispersed on flat electrodes. Atomic layer deposition (ALD) is a versatile technique to the precise growth of a variety of materials. Specifically, the key point in ALD process is that precursor molecules evaporated at an appropriate temperature react only with chemically reactive surface sites (e.g. hydroxyl groups on surfaces), and these reactions are self-limiting, i.e. controllable at the atomic level. Thus, we utilize a self-limiting nature of ALD for nanocluster formation. Meso-tetra(4-carboxyphenyl)porphyrin (TCPP) monolayer is adsorbed parallel to the electrode surface, and subsequently metallated with Mn (or Fe)-OH (denoted by MnTCPP or FeTCPP) as reactive sites for nickel oxide growth. The nickel oxide nanoclusters, then, are grown on the -OH functional groups of MnTCPPs (or FeTCPPs) via ALD. The growth of nickel oxide nanoclusters is demonstrated in detail by transmission electron microscopy images and grazing incidence small angle X-ray scattering analysis, as well as by in-situ monitoring mass gain during deposition. Additionally, to evaluate the electrocatalytic water oxidation activity of nanoclusters, TCPP molecules are removed from nanocluster films through post-ozone-treatments at a relatively low temperature. Based on electrochemical analysis, 1-2 nm sized-nanocluster films show a significantly higher water oxidation activity (i.e. higher water oxidation currents for unit number of nickel atoms deposited on films) compared with that of a very thin film. Consequently, this shows that the uniformly dispersed nanoclusters should be very useful for many applications including electrocatalysis, catalysis, and supercapacitors.

Sol–gel synthesis of titanium oxide supported nickel catalysts for hydrogen and carbon production by methane decomposition

TiO2-supported NiO hybrids have been synthesized by the sol–gel method and further processed into catalysts for hydrogen production by methane decomposition. The structures of the metal oxides and catalysts are characterized using field emission electron microscopy, transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and N2 adsorption-desorption test. The catalytic performance of the catalysts is evaluated in terms of hydrogen yield rate, methane conversion and carbon yield. It is found that the TiO2-supported catalysts show better catalytic performance when compared with the unsupported catalyst, which is attributed to the uniform dispersion of ultrafine nickel particles as well as the appropriate metal-support interaction. The catalyst performance is dependent on the ratio of NiO and TiO2. The 1NiO–2TiO2 exhibits the highest carbon yield of 321.1 g C g−1 Ni at 500 °C. The structures of the produced carbons are characterized by transmission electron microscopy and X-ray diffraction. It is found that the resulting filamentous carbon materials exhibit uniform diameters and various morphologies including hollow tube, platelet, bow-like and herringbone structures.

Study on Preparation Technology of Nickel Powder with Liquid Phase Reduction Method

Ultrafine nickel powder was prepared without dispersant by liquid phase reduction method. The hydrazine hydrate was used as the reductant, the nickel sulfate as the raw material and NaOH was the pH regulator. The influences of the reaction temperature, pH, concentration of Ni2+ ions, mole ratio of N2H4·H2O/Ni2+ on the particle size, the morphology and the dispersion of nickel powder were studied. The samples were characterized by the scanning electron microscope (SEM), X-ray diffraction (XRD), laser particle size analysis etc. The results show that the high purity and spherical nickel powder with face-centered cubic structure can be prepared when the temperature is 80 C, pH is 11, the concentration of Ni2+ ions is 0.5 mol/L, the mole ratio of N2H4·H2O/Ni2+is 4. The average particle size of nickel powder is about 400 nm.

ВЛИЯНИЕ РАЗМЕРА ВКЛЮЧЕНИЙ УЛЬТРАДИСПЕРСНЫХ ЧАСТИЦ НИКЕЛЯ НА ПОРОГ ЛАЗЕРНОГО ИНИЦИИРОВАНИЯ ТЭНА

ВЛИЯНИЕ РАЗМЕРА ВКЛЮЧЕНИЙ УЛЬТРАДИСПЕРСНЫХ ЧАСТИЦ НИКЕЛЯ НА ПОРОГ ЛАЗЕРНОГО ИНИЦИИРОВАНИЯ ТЭНА

Magnetically separable Ni/SPL@Carbon nanocomposite for removal of Pb(II) from the aqueous solution

Magnetically separable nanocomposite adsorbents have been synthesized by a simple hydrothermal/solid-state method, in which sepiolite (abbr. SPL) clay, glucose and nickel nitrate were used as the role of template, carbon and the magnetic medium, respectively. In the present work, carbon firstly was covered onto the surface of rod-like SPL clays by hydrothermal treatment, and further ultrafine nickel particles (0.5–1nm) were loaded into the above carbons, giving rise to unique ternary structures with various kinds of surface areas, pore volumes and pore size distributions. The Ni/SPL@Carbon-1:10 sample possesses the largest surface area (92.0m2g−1) compared with that of Ni/SPL@Carbon-1:1 (49.6m2g−1) and Ni/SPL@Carbon-1:5 (51.8m2g−1). The impact of several key factors, mainly including contact time, initial metal ion concentration and initial pH, upon the adsorptive performance was investigated in depth. The Ni/SPL@Carbon-1:10 sample, as an effective adsorbent, thus exhibits the highest uptake amount (28.04mgg−1) for the removal of Pb(II) ions from an aqueous solution. More importantly, the present adsorbents can be readily separated with an external magnetic field, implying their potential superiority in practical applications.

A two-stage reduction process for the production of high-purity ultrafine Ni particles in a micro-fluidized bed reactor

A novel two-stage reduction process for synthesis of ultrafine nickel powder with a high purity and low density in a fluidized bed reactor has been developed in this work. The raw ultrafine NiO particles are first pre-reduced using hydrogen at lower temperatures (340–400°C), followed by further reduction at higher temperatures (500–600°C). The self-agglomeration of Ni particles formed during low-temperature reduction decreases the sintering activity of the newly formed ultrafine Ni particles, leading to good fluidization quality, even for the subsequent high-temperature reduction process. The agglomerated Ni particles have a high Ni content (above 99wt%), a low density (0.78g/cm3) and a uniform particle size (approximately 100μm). A concept design for a novel two-stage fluidized bed reactor process used to produce high-purity Ni powder was also proposed. This approach may be extended to the synthesis of other ultrafine/nanosized metals or metal oxides through a fluidization method.

Positron annihilation studies of defects and fine size effects in nanocrystalline nickel oxide

Ultrafine nickel oxide nanoparticles were prepared by sol–gel method using a solution of nickel nitrate hexahydrate and ammonium hydroxide and subsequently annealed in air at different temperatures in the range 200–275 °C for different hours to vary the particle sizes. They were characterised for phase, purity, structure and sizes by X-ray diffraction and high-resolution transmission electron microscopy. They were found polycrystalline in nature and possessed face-centred cubic (NaCl-type) structure with lattice parameter varying with annealing temperature. The ultrafine structure clearly revealed the formation of hexagons with average diameter about 5 nm. Ultraviolet–visible absorption spectroscopy was carried out to study the optical properties and for the estimation of the bandgap. The nanoparticles exhibited weak and strong quantum confinement in the size ranges of 10.47–8.47 and 6.57–5 nm. The samples were then investigated through positron annihilation spectroscopy to characterise and closely monitor the evolution of vacancy-type defects and defect clusters during particle growth in the samples. The positron lifetime drastically increased at very low particle sizes, supporting the confinement effects demonstrated by optical absorption studies. The results from coincidence Doppler broadening measurements were consistent and indicated changes also in the electron momentum distribution during the occurrence of these finite size effects in the nanoparticles.

Effect of reductant and PVP on morphology and magnetic property of ultrafine Ni powders prepared via hydrothermal route

The ultrafine nickel particles with different shapes including sphere, pearl-string, leaf, fish-bone, hexagonal sheet and silknet were prepared through one-step hydrothermal reduction using hydrazine hydrate, sodium hypophosphite and ethylene glycol as reductants, polyvinylpyrrolidone as structure-directing agent. It has been verified with the characterization of X-ray powder diffraction and transmission/scanning electronic microscopy that as-prepared products belong to face-centered cubic structure of nickel microcrystals with high purity and fine dispersity. The magnetic hysteresis loops measured at room temperature reveal that the values of saturation magnetization, remanent magnetization and coercivity rise sequentially from silknet, sphere to hexagonal sheet. In comparison with nickel bulk counterpart, the coercivity of the hexagonal sheet nickel powders increases by 25%.

Mechanism of abnormal grain growth in ultrafine-grained nickel

During annealing of ultrafine nickel powder compacts, abnormal grain growth (AGG) occurred with the formation of cube-shaped grains. The observed AGG is similar to the late-stage abnormal grain growth (LS-AGG) that is commonly observed in electrodeposited (ED) Ni sheets. The cube shape of the abnormal grains with {100} facets was identical to that of late-stage abnormal grains in ED Ni. As the temperature increased, the time to the appearance of abnormal grains decreased. After impingement of abnormal grains, little further grain growth occurred, indicating stagnant grain growth behavior. The formation of abnormal grains in the present study, however, cannot be explained by the previously suggested AGG mechanisms, i.e. the S phase wetting mechanism and initial texture mechanism, because no amorphous phase containing S was present and no texture developed in our samples. In contrast, the observed grain growth behavior can be well explained in terms of the coupling effect of the maximum driving force for grain growth and the critical driving force for appreciable migration of faceted boundaries. It is concluded that the AGG in ultrafine-grained Ni occurs via mixed migration mechanisms, i.e. diffusion and interface reaction-controlled, of faceted boundaries with respect to the driving force.

Exploiting the Influence of Oxidization on Ultra-Fine Copper and Nickel Sulfide Containing Pt-Pd in Yunnan Mine

It is known that oxidation is one of the most common ways for penlandite to be introducted into tailing during traditional coarse-particle sulfide flotation. However, it could become much more complicated and challenging problems for the low-grade, fine-disseminated Cu-Ni sulfides containing Pt and Pd in Yunnan Mine, accompanied with more than 75% of the content of MgO in the ore sample is. Direct flotation tests had been conducted to extract the metallic values as much as possible by adding traditional depressants and collectors, such as carboxylmethyl cellulose, starch, sodium silicate, butyl xanthate, (BX), butyl ammonium dithophosphate (BA) and etc., the relatively satisfied recoveries of Cu, Ni, Pt and Pd in the concentrate from bench flotation tests were obtained, however, more than 30% of metallic values still lost in the slime. In this study, bench flotation tests for the ore sample fromYunnan Mine, micro-flotation tests of serpentines and pentlandite from Jinchuan Mine and their settling rate tests were conducted to figure out how the oxidation influence the recovery of the ultra-fine nickel sulfide. All the tests results pointed to the presence of over-oxidation on the ultra-fine nickel sulfide surface and lead to the loss of Ni containing Pt and Pd in the slime tailing. Some methods which tried to slow the speed of oxidation on mineral surface during grinding and flotation were introduced in order to recover the values before over-oxidation of sulfides; however, the slime coating of serpentines also may play an important role in disturbing the floatability of ultra-fine sulfide.

The Preparation of CaZrO<sub>3</sub> Coating Ultra-Fine Nickel Powders via Chemical Deposition

Aiming at flexible oxidation in the MLCC production, the surface modification of the ultrafine nickel powders has been carried out to coat Ni powders with CaZrO3 by using chemical precipitation method. CaZrO3-coated composite ultrafine nickel powders have been synthesized in methanol-water solvent by both precipitation agents solution and zirconium-calcium solution dripped into the Ni-particle-dispersed methanol solution at the meantime. Composite nickel powders obtained under the optimum conditions were characterized, It was approved that those composite nickel powders still possessed good dispersion, the resistance to oxidation and shrinkage were improved greatly.

Microstructure and properties of ultrafine grain nickel 200 after hydrostatic extrusion processes

This paper presents the results of the studies of the structure and properties of ultrafine grained nickel 200 obtained by hydrostatic extrusion processes. Microstructure was characterized by means of optical microscopy and electron transmission microscopy. Corrosion resistance was studied by impedance and potentiodynamic methods using an AutoLab PGSTAT 100 potentiostat in 0.1 M Na2SO4 solution and in acidified (by addition of H2SO4) 0.1 M NaCl solution at pH = 4.2 at room temperature. Microhardness tests were also performed. The results showed that hydrostatic extrusion produces a heterogeneous, ultrafine-grained microstructure in nickel 200. The corrosive resistance tests showed that the grain refinement by hydrostatic extrusion is accompanied by a decreased corrosive resistance of nickel 200.