Nickel Lattice Research Articles

Synthesis and characterization of the nanostructured solid solution with extended solubility of graphite in nickel by mechanical alloying

In the present work, mechanical alloying of a powder mixture of nickel and graphite (up to 15wt%) was carried out in an attrition mill under a nitrogen atmosphere. The as-milled powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The 15wt% graphite dissolved into the nickel (exceeding the negligible solid solubility in the nickel-carbon system), thereby forming a supersaturated solid solution of graphite in a nickel matrix. The dissolved graphite occupied interstitial positions along the dislocation edges and at the grain-boundary regions. A three-step graphite dissolution mechanism has been proposed. The associated changes in the nickel lattice, such as changes in the crystallite size (62 to 43 nm), lattice strain (0.12% to 0.3%), and lattice parameter (0.3533 to 0.3586 nm), which led to the formation of the supersaturated solid solution, were also evaluated and discussed.

Evidence of Variations in Atomic Distribution in Disordered Mixed Metal Hydroxides

ABSTRACTNumerous fabrication protocols are known to yield transition metal oxides with structures related to layered double hydroxides, but the effect of fabrication protocol on the uniformity of mixed-metal compositions remain largely unexplored. We have analysed the apparent solubility limits and the structural implications of iron ions in nickel hydroxide lattices for materials prepared by four different fabrication protocols. Opposing shifts in the (100) and (001) reflection in powder X-ray diffraction results revealed a contraction of the nickel lattice upon successful incorporation of iron, with Ni-M distances exhibiting an apparently linear decrease with respect to iron content. This feature revealed the amount of iron incorporated into nickel-based materials to be dependent on fabrication protocol, varying from apparently negligible concentrations to over fifty atomic percent. The dependency of structure on fabrication protocols provides a handle to improve fundamental understanding of catalytically relevant coordination environments.

Pd–H and Ni–H phase diagrams using cluster variation method and Monte Carlo simulation

ABSTRACTThis work focuses on interstitial solid solutions of hydrogen in the face-centred cubic (fcc) host lattice of palladium and nickel, using a first-principles based approach. Cluster Variation Method (CVM) and Monte Carlo simulation algorithms were especially designed, allowing a coupled use of both techniques, to study hydrogen–vacancy interactions inside an fcc metallic host lattice. First-principles calculations provided the H–Vac interaction energies by structure inversion method. The phase diagrams and thermodynamic properties were computed using only theoretical inputs. The mechanisms leading to the formation of the miscibility gaps observed for both Pd–H and Ni–H systems and the hydrogen ordering on palladium interstitial lattice were reproduced without any empirical term.

Molecular dynamics study of two-dimensional discrete breather in nickel

A discrete breather (DB) is a spatially localized vibrational mode of large amplitude in a defect-free anharmonic lattice. Generally, zero-dimensional DB is considered to be localized in all [Formula: see text] directions of the [Formula: see text]-dimensional lattice. However, the question of existence of DBs localized in [Formula: see text]–[Formula: see text] directions and delocalized in other [Formula: see text] directions remains open. In the present paper, for the first time, the case of [Formula: see text] and [Formula: see text] is considered by constructing a two-dimensional (2D) DB in the fcc nickel lattice using molecular dynamics methods. In order to excite such DB, one of the delocalized vibrational modes of the triangular lattice was used (the (111) plane in fcc crystal is a triangular lattice). All simulations were carried out at zero temperature. The investigated 2D DB demonstrates hard-type nonlinearity, when its oscillation frequency increases with increasing amplitude. The oscillation frequencies of the DB are above the upper edge of the phonon spectrum for nickel, which is 10.3[Formula: see text]THz. The maximum DB lifetime is found to be 9.5[Formula: see text]ps. The obtained results expand our understanding of diversity of nonlinear spatially localized vibrational modes in nonlinear lattices.

Integration of MoO2 Composite on the Micro-evolution and Anticorrosion Mitigation of Zn–Ni–MoO2 Thin Films Coating by Electrodeposition System

Zinc–nickel–molybdenum nano-composite coating was deposited on carbon steel substrate using electrolytic deposition technique. The MoO2 integration into zinc–nickel matrix was investigated with reverence to particulate concentrations from 10 to 15 g/L, voltage 5–1.0 V and 1 A/dm2. The effect of the percentage variation of MoO2 particle inclusion into the zinc–nickel lattices’ was seen, and surface morphology, with intermetallic phase transformation of the nano-composite were obtained using scanning electron microscopy coupled with energy dispersive spectroscopy. The corrosion behaviour and micro-hardness characteristics of the Zn–Ni–MoO2 composite deposits were studied using linear polarization technique. The result shows that the incorporation of MoO2 particles into the zinc–nickel matrix disperses evenly with increasing concentration of MoO2 particle and significantly modified the crystal orientation of the Zn–Ni–MoO2 deposit. A content of 10 g vol.% MoO2 particle incorporated Zn–Ni–MoO2 nano-composite deposit was found to obtained good corrosion, wear and better micro-hardness properties.

Charge transfer and hybridization effect at the graphene-nickel interface: A tight binding model study

We have investigated here, the electronic and magnetic properties of graphene–nickel system by tight-binding mean-field approach. Strong hybridization between the 2pz orbital of graphene and 3dz2 orbital of nickel occurs when monolayer graphene is placed over a single layer of ferromagnetically ordered Ni (111) metal due to the excellent lattice matching between the two layers. This hybridization greatly affects the electronic and magnetic properties of the bilayer system, resulting in a significantly reduced local magnetic moment of the nickel layer and an enhanced induced spin polarization on the graphene layer. The calculated Hamiltonian revealed critical information regarding the first-, second-and third-nearest-neighbour hopping integrals of π− electrons of graphene besides the Coulomb correlation of electrons in nickel (111). The Hubbard type Coulomb interactions present in nickel lattices were treated within the mean-field approximation. Zubarev's technique was employed to calculate electronic Green's functions and subsequent investigation of the temperature dependent ferromagnetic magnetization of nickel (111)was carried out through self-consistent calculation. Further calculations regarding the induced magnetization in the graphene, total magnetization in bilayer layer system, electronic band dispersion, spin resolved density of states (DOS) and spin polarization efficiency have been carried out. The results were corroborated by experimental observations.

Role of Boron and Phosphorus in Enhanced Electrocatalytic Oxygen Evolution by Nickel Borides and Nickel Phosphides

AbstractThe modification of nickel with boron or phosphorus leads to significant enhancement of its electrocatalytic activity for the oxygen evolution reaction (OER). However, the precise role of the guest elements, B and P, in enhancing the OER of the host element (Ni) remains unclear. Herein, we present insight into the role of B and P in enhancing electrocatalysis of oxygen evolution by nickel borides and nickel phosphides. The apparent activation energy, Ea*, of electrocatalytic oxygen evolution on Ni2P was 78.4 kJ/mol, on Ni2B 65.4 kJ/mol, and on Ni nanoparticles 94.0 kJ/mol, thus revealing that both B and P affect the intrinsic activity of nickel. XPS data revealed shifts of −0.30 and 0.40 eV in the binding energy of the Ni 2p3/2 peak of Ni2B and Ni2P, respectively, with respect to that of pure Ni at 852.60 eV, thus indicating that B and P induce opposite electronic effects on the surface electronic structure of Ni. The origin of enhanced activity for oxygen evolution cannot, therefore, be attributed to such electronic modification or ligand effect. Severe changes induced on the nickel lattice, specifically, the Ni‐Ni atomic order and interatomic distances (strain effect), by the presence of the guest atoms seem to be the dominant factors responsible for enhanced activity of oxygen evolution in nickel borides and nickel phosphides.

Synthesis of Filamentary Carbon Material on a Self-Organizing Ni–Pt Catalyst in the Course of 1,2-Dichloroethane Decomposition

A series of model microdisperse Ni1–xPt x alloys (x =0–0.05) was synthesized by a coprecipitation method with the subsequent sintering of the precipitate in an atmosphere of H2 at 800°C. Their chemical and phase compositions were determined (by AAS and XRD analysis, respectively), and it was found that the synthesis method proposed afforded Ni–Pt solid solutions based on the face-centered nickel lattice. The kinetic features of the carbon erosion of Ni1–xPt x alloys in their contact with 1,2-dichloroethane vapor in a temperature range of 550–700°C were studied. It was found that the presence of Pt in the alloy increased the rate of accumulation of carbon product by a factor of ~1.5 regardless of the concentration of Pt. The catalyst did not undergo deactivation for 5 h of reaction to ensure a high yield of carbon material (103 g/gCat). With the use of electron microscopy (SEM and TEM techniques), it was found that the carbon product consisted of carbon fibers with a segmented structure. An increase in the concentration of Pt in the alloy to 4.3 wt % sharply changed the disintegration of the alloy to cause the formation of carbon product with a bimodal fiber diameter distribution (dav = 0.4 and 1.2 μm).

Synthesis of nickel boride by thermal explosion in ball-milled powder mixtures

In this work, a synthesis route of Ni3B, an attractive material for making heating elements and a promising component for catalysts, was developed using high-energy ball milling of nickel and boron powder mixtures. The milling duration was varied from 1 to 15 min. Ball milling led to partial dissolution of boron in the crystalline lattice of nickel and crystallite size refinement of nickel. Heating of the ball-milled mixtures at a constant rate led to thermal explosion, the indications of which were a rapid temperature rise and the formation of boride phases. The duration of ball milling was shown to influence the phase composition of the products of thermal explosion. The time of milling ensuring the formation of single-phase Ni3B was determined to be 7 min. The ignition temperature of thermal explosion decreased with the milling time: a decrease by more than 300 °C was observed for the mixture milled for 15 min relative to the non-milled mixture. The maximum temperature developed during thermal explosion increased in the mixture milled for 1 min relative to the non-milled mixture and then decreased with the milling time reaching the level of the non-milled mixture after 15 min of milling. The observed dependence of the maximum temperature on the milling time is related to the net effect of mixing uniformity improvement between the reactants and a partial transformation of the reaction mixtures into Ni(B) solid solutions and Ni3B during milling. The proposed synthesis route of a single-phase Ni3B powder has advantages of short processing time and low-energy consumption.

Magnetic correlations and transport properties in triangular-lattice nickel germanide Ni1.8Ge single crystal

Magnetic and transport properties of triangular-lattice Ni1.8Ge single crystal have been studied. The results reveal that Ni1.8Ge is a metal with an obvious magnetic anisotropy. The compound exhibits ferrimagnetic correlations along both directions. However, the long-range magnetic order was not observed due to the geometrical frustration arising from the triangular nickel lattice. At low temperature, the electron-magnon scattering and spin fluctuation have obvious contributions to the resistivity and magnetoresistance, indicating the existence of short-range dynamic magnetic ordering.

Adsorption of graphene to nickel (111) using the exchange-hole dipole moment model

Graphene is a promising material for a number of technological applications due to its unique electronic properties. It can be mass produced by depositing carbon atoms on metal scaffolds, such as nickel. This work presents a detailed study of graphene adsorption on the nickel (111) surface using the exchange-hole dipole moment (XDM) dispersion correction. XDM is shown to accurately model graphene-nickel interactions, providing adsorption energies in excellent agreement with available experimental data and with RPA calculations. All six graphene-nickel orientations studied present a physisorption energy minimum, but only three exhibit chemisorption. The physisorption and chemisorption minima are close in energy, and are separated by a barrier of ∼1 kJ/mol per carbon. The relative strength of the chemisorption and physisorption interactions is found to depend heavily on the nickel lattice constant. Thermal expansion stabilizes chemisorption relative to physisorption. The pairwise dispersion coefficients depend strongly on the graphene-nickel distance, and their variation is determined by the exchange-hole dipole moments. If this dependence of the dispersion coefficients with the environment is properly captured, a pairwise dispersion correction (like XDM) is suitable to model surface adsorption.

Promoting Effect of Co, Cu, Cr and Fe on Activity of Ni-Based Alloys in Catalytic Processing of Chlorinated Hydrocarbons

A series of sponge-like Ni1−xMx (M = Cu, Co, Cr, Fe; x = 0.00–0.10) alloys was prepared via synthetic routes with subsequent reduction in H2 atmosphere at 800–1000 °C. Formation of Ni-based solid solutions with face-cantered cubic (fcc) lattice of nickel was proven by X-ray diffraction analysis for all prepared samples. Ni1−xMx alloys were explored as precursors for self-organizing catalysts active in processing of 1,2-dichloroethane into carbon nanomaterial (CNM). According to kinetic studies of CNM growth performed at 600 °C, the catalytic activity of Ni1−xMx samples changes as follows: Cr > Co–Cu ≫ Fe. Ni–Cr sample showed rather stable performance during 4 h whereas Ni–Co, Ni–Cu and Ni (reference) samples underwent rapid deactivation after ~150 min of reaction. The presence of the residual amount of Cr (0.5 at.%) found by energy dispersive X-ray microanalysis method in the composition of active Ni particles responsible for the growth of CNM is considered to be a key factor providing the stable catalytic performance. The obtained carbon product is represented by well-ordered segmented fibers (0.4–0.8 μm in diameter) and characterized with comparatively high textural parameters (surface area 290–330 m2/g, pore volume 0.43–0.57 cm3/g).

Laser synthesis, structure and chemical properties of colloidal nickel-molybdenum nanoparticles for the substitution of noble metals in heterogeneous catalysis

Platinum and iridium are rare and expensive noble metals that are used as catalysts for different sectors including in heterogeneous chemical automotive emission catalysis and electrochemical energy conversion. Nickel and its alloys are promising materials to substitute noble metals. Nickel based materials are cost-effective with good availability and show comparable catalytic performances. The nickel-molybdenum system is a very interesting alternative to platinum in water electrolysis. We produced ligand-free nickel-molybdenum nanoparticles by laser ablation in water and acetone. Our results show that segregated particles were formed in water due to the oxidation of the metals. X-ray diffraction shows a significant change in the lattice parameter due to a diffusion of molybdenum atoms into the nickel lattice with increasing activity in the electrochemical oxygen evolution reaction. Even though the solubility of molecular oxygen in acetone is higher than in water, there were no oxides and a more homogeneous metal distribution in the particles in acetone as seen by TEM-EDX. This showed that dissolved molecular oxygen does not control oxide formation. Overall, the laser ablation of pressed micro particulate mixtures in liquids offers a combinational synthesis approach that allows the screening of alloy nanoparticles for catalytic testing and can convert micro-mixtures into nano-alloys.

Defects in a lattice of pure nickel subjected to fast-neutron irradiation followed by annealings: Neutron-diffraction examination

Nickel specimens subjected to fast-neutron irradiation followed by annealings have been examined using neutron and X-ray diffraction. The type of structural defects, which result from the fast-neutron irradiation of nickel crystals, has been first identified using neutron diffraction and the experimental dependence of the lattice parameter on the concentration of interstitial defects has been determined. It is shown that the changes in the lattice parameters due to both irradiation and annealings are primary related to the variations in the concentration of interstitial atoms in the lattice.

Hydrogen purification of synthetic water gas shift gases using microstructured palladium membranes

Novel microstructured palladium composite membranes are fabricated using microfabrication technologies. The membranes have a thickness of 1 micron, and are supported by a microstructured nickel lattice 10 micron in thickness. The membranes' flux versus hydrogen partial pressure are evaluated, and a linear correlation found, indicating a deviation from Sieverts Law due to their relative thinness. The permeance of the membrane are found to be approximately 3 × 10−6 mol*m−2*s−1*Pa−1. The membranes are tested under Department of Energy specified synthetic water gas shift mixtures at temperatures of 320 °C and 380 °C and exhibited fluxes between 0.2 and 0.4 mol*m−2*s at 275 kPag (40 psig). The membranes have stable performance at 320 °C, while alloying of the palladium and nickel support slowly occurs at 380 °C, causing a decline in flux. A permeance selectivity of 458:1 H2:He is observed at a pressure gradient of 1.37 MPag (205 psig) and 380 °C, however a true ‘burst pressure’ is unable to be determined due to the maximum output limitations of the pressure regulator. Hydrogen sulfide reduces membrane performance, as expected of a pure palladium membrane.

Assessment of the dislocation bias in fcc metals and extrapolation to austenitic steels

A systematic study of dislocation bias has been performed using a method that combines atomistic and elastic dislocation-point defect interaction models with a numerical solution of the diffusion equation with a drift term. Copper, nickel and aluminium model lattices are used in this study, covering a wide range of shear moduli and stacking fault energies. It is found that the dominant parameter for the dislocation bias in fcc metals is the width of the stacking fault ribbon. The variation in elastic constants does not strongly impact the dislocation bias value. As a result of this analysis and its extrapolation, the dislocation bias of the widely applied austenitic stainless steels of 316 type is predicted to be about 0.1 at temperature close to the swelling peak (815 K) and typical dislocation density of 1014 m−2. This is in line with the bias calculated using the elastic interaction model, which implies that the prediction method can be used readily in other fcc systems even without EAM potentials. By comparing the bias values obtained using atomistic- and elastic interaction energies, about 20% discrepancy is found, therefore a more realistic bias value for the 316 type alloy is 0.08 in these conditions.

Tailoring the Properties of Atomic Layer Deposited Nickel and Nickel Carbide Thin Films via Chain-Length Control of the Alcohol Reducing Agents

Atomic layer deposition (ALD) of nickel and nickel carbide is reported starting from nickel acetylacetonate and a primary alcohol. The sequential reactions of both reactants with the adsorbed species are shown to be self-limited. Use of propanol or ethanol as reducing agents yields the formation of the technologically relevant carbon-Ni3C thin films, whereas the carbon content with use of methanol is less than 5 atom %. These metallic nickel thin films are electrically conductive and feature a soft ferromagnetic behavior. The thermally stable cubic lattice of nickel was grown at 300 °C with methanol as a reducing agent while the metastable hexagonal structure was obtained at lower temperatures. The morphology and the structure of the films were investigated with use of scanning electron microscopy and X-ray diffraction. The films are nanocrystalline featuring an average crystallite size of ∼10 nm. Hydrogen-free ALD of nickel is particularly appealing for the deposition of (i) conformal coatings on hydrogen-sensitive substrates such as highly reducible oxides and metals with high capacity to form hydrides and (ii) 3D nanomaterials with high aspect ratio.

Compositional dependence of serrated flow in nickel binary solid solutions during high-temperature microindentation

At 450 °C, pure nickel and nickel binary solid solutions, containing Ru, Rh, W, Re, Ir and Pt, have a smooth load–depth curves. In contrast, the alloying addition of Nb, Mo, Pd and Ta results in the occurrence of serrations in their load–depth profiles. Analyses show the load increment of the quasi-elastic segments scales linearly with the load at their starting point. The slope of such linear relationships was normalized by the solute concentration and then plotted against the diffusion rate of transition metal solutes within the nickel lattice and along dislocation cores. Linear relationships were observed in both cases. Results suggest that the solute diffusion along dislocation cores coupled with the atomic size misfit are mainly responsible for such serrations.

Erosion–corrosion resistance of Ni composite coatings with embedded SiC nanoparticles

This study assessed the erosion–corrosion behavior of pure Ni and Ni–SiC composite coatings evaluated in a corrosive environment using in situ potentiondynamic polarization and electrochemical impedance. Coatings were obtained from a Watts classical solution in which SiC nanoparticles were added. Coatings were galvanostatically deposited on carbon steel on a rotating disk electrode. The hydrodynamic conditions of the bath and the content of SiC in the electrolyte were varied. The morphology, structure and properties of the coatings were evaluated in relation to the electro-synthesis conditions. It was found that incorporation of SiC nanoparticles into the metal matrix produces morphological changes in the deposit. These are responsible for increases in the microhardness of the composite coatings and a better resistance against erosion–corrosion compared with pure nickel coatings. The increases in SiC nanoparticle content in the coating and the hydrodynamic conditions in the electroplating process cause grain refining and changes in the crystal growth of the nickel grains in the Ni deposit. As consequence of structural modification in the crystalline orientation of the Ni deposit, grain refining and strain occurred in the nickel lattice. These structural changes in the nickel deposit led to enhanced performance of the Ni–Sic composite coating in the erosion–corrosion test. Additionally, the presence of inert particles of SiC in the conductive matrix coating may have blocked the passage of the anodic Faradaic current, diminishing the corrosion rate of the coating.

Investigation of nickel lattice sites in diamond: Density functional theory and x-ray absorption near-edge structure experiments

Possible lattice incorporation sites for Ni in diamond have been investigated using ab initio density functional theoretical calculations. The results have been used to compute x-ray absorption near-edge structure spectra which were compared to spectroscopic measurements performed on a diamond single crystal grown at high pressure and high temperature in a nickel solvent. Ni at divacancy sites is proposed to be the most stable and probable configuration in this crystal.