Nickel-cobalt Alloys Research Articles

Bamboo-like nitrogen-doped porous carbon nanofibers encapsulated nickel-cobalt alloy nanoparticles composite material derived from the electrospun fiber of a bimetal-organic framework as efficient bifunctional oxygen electrocatalysts.

The development of low-cost bifunctional electrocatalysts with both a high activity and long durability is critical for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The reasonable design and construction of bifunctional electrocatalysts is the key to energy storage and energy conversion technologies. In this study, transition metal carbon nitrides were used as a substitute for the precious metal catalyst, the Ni-Co-BTC (metal organic framework (MOF)) mixed with polyacrylonitrile (PAN) using electrostatic spinning technology to prepare the bamboo-like nanofibers precursor (Ni-Co-BTC@PAN). A series of electrocatalytic materials (NiCo-X@N-CNFs-Ts, T = 700, 800, 900 °C) were synthesized with nitrogen-doped carbon nanofibers coated with NiCo alloy nanoparticles using high temperature carbonization at different temperatures. We studied the effects of different calcination temperatures and different Ni/Co molar ratios of NiCo-X@N-CNFs-Ts (T = 700, 800, 900 °C) on the bifunctional catalytic performance of the ORR/OER. The composite, NiCo-0.8@N-CNFs-800, exhibited a highly doped-N level, uniform NiCo alloy nanoparticle dispersion and decentralized NiCo-Nx active sites, therefore affording an excellent bifunctional electrocatalytic performance. The ORR onset potential on NiCo-0.8@N-CNFs-800 was 0.91 V and the half-wave potential (E1/2) was 0.82 V, the NiCo-0.8@N-CNFs-800 corresponded to the minimum potential of 1.61 V at the current density of 10 mA cm-2 among all of the NiCo-X@N-CNFs-Ts hybrids under the OER condition. The NiCo-0.8@N-CNFs-800 catalyst exhibited a low reversible overpotential of 0.79 V between the ORR (E1/2) and OER (Ej = 10 mA cm-2) with excellent stability, durability and methanol tolerance, even surprisingly superior to the commercial Pt/C and RuO2 catalysts. This work provides a general strategy and useful guidance for the design and development of a variety of multifunctional non-noble metal catalysts for energy applications.

Enhanced Electromagnetic Wave-Absorbing Performance of Magnetic Nanoparticles-Anchored 2D Ti3C2Tx MXene.

Two-dimensional Ti3C2Tx MXene-based hybrids-anchored magnetic metal nanoparticles show a huge potential application as effective wave absorbers due to the synergistic electromagnetic (EM) loss effect. In this work, uniform and size-controllable nickel, cobalt, or nickel-cobalt alloy nanoparticles were in situ grown on the surface of MXene via a facile and moderate co-solvothermal method for the first time. As an example, a nickel nanoparticles-anchored MXene (Ni@MXene) hybrid was homodispersed into dielectric polyvinylidene fluoride to develop its EM wave-absorbing capacity to a great extent. As expected, the results showed strong reflection loss (RLmin = -52.6 dB at 8.4 GHz), broad effective absorption bandwidth (EAB = 3.7 GHz including 71% of X-band), low loading (10 wt % Ni@MXene), and thin thickness (3.0 mm). By adjusting the sample thickness, EAB can cover completely the whole X-band with a maximum of 6.1 GHz, showing a huge potential of Ni@MXene hybrid applying as aircraft stealth coating. The mechanism analyses revealed that the excellent impedance matching, magnetocoupling effect, conductance, magnetic loss, and multiple scatterings contribute to the splendid EM wave-absorbing performance of the Ni@MXene hybrid. Considering the excellent overall performance, the Ni@MXene hybrid was identified as a promising candidate for EM wave absorption.

Preparation of Co-Ni Alloy Coating with Stable Composition by Jet-Electrodeposition

Cobalt-Nickel (Co-Ni) alloy coatings were prepared by jet electrodeposition on brass substrate under different Co2+/Ni2+ ratio contents (M = 2:1, 1:1, 1:2 and 1:3) and solution flow rates (from 2.0 to 4.5 L/min). The surface morphology, element content, and phase structure of the coating were observed by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and X-ray diffractometer (XRD). The hardness and wear resistance of the coatings were also measured. The results showed that the Co content in coatings was greater than 70%, no matter at what flow rate and concentration. With an increase of the flow rate, the Co content in the coating increases, and the grain size on the surface of the coating decreases, which leads to increased hardness of the coating. However, the flow rate of the plating solution has little effect on the grain growth orientation, and the phase structure is dominated by the elemental content of the coating. The coatings are in a single phase of hexagonal close-packed (HCP) when the Co content is more than 80%, while the coatings are in dual phases of the HCP and face-centered cubic (FCC) when the Co content is less than 80%. With an increase in the Co content, the grain size decreases, and consequently, the hardness and wear resistance of the alloy increase. A Co-Ni alloy coating with stable composition can be obtained when the ratio of Co2+ to Ni2+ is 2:1.

Electrochemical behavior and electrodeposition of Ni-Co alloy from choline chloride-ethylene glycol deep eutectic solvent

In this work, nickel-cobalt (Ni-Co) alloy was prepared in choline chloride-ethylene glycol deep eutectic solvent by deposition. Metal ion complex structure and stability were studied using UV–Vis. The electrochemical behavior in different metal salts was studied by voltammetry (CV) and chronoamperometry (CA). The corrosion resistance was studied using potentiodynamic polarisation and electrochemical impedance (EIS). Surface and phase composition of Ni-Co alloy coatings were characterized by scanning electron microscopy (SEM/EDS) and X-ray diffraction (XRD). The results from the voltammetry showed that the reduction peak appear among −0.6 V ∼ −1.13 V, which belonged to Ni-Co codeposition. The reduction of Ni-Co alloy in the CE was an irreversible process under diffusion control. Chronoamperometric results indicated that the electrodeposition of Ni-Co on a glassy carbon electrode followed the mechanism of instantaneous nucleation and three-dimensional growth. The results of microstructure and phase composition showed that the control of deposition potential could effectively control the microstructure and Co content of Ni-Co alloy. Nano crystal structure could be obtained with a grain size in the range of 3.1–4.0 nm. Comparison in the corrosion behaviour of the coatings showed that the change of Co content had an effect on the corrosion resistance of Ni-Co alloy.

Diameter dependent structural and magnetic properties of CoNi alloy nanotubes

Cobalt-Nickel (CoNi) alloy nanotubes (NTs) with diameters 50 nm (D1), 100 nm (D2), 150 nm (D3), and 200 nm (D4) have been fabricated using Anodic Aluminum Oxide (AAO) membranes. X-ray diffraction spectroscopy (XRD), field-emission scanning electron microscopy (FE-SEM), vibrating-sample magnetometer (VSM), and physical property measurement system (PPMS) analysis methods were employed to systematically investigate the structural, morphological and magnetic properties of CoNi NTs samples. Magnetization reversal mechanism has been explained by angular dependence of coercivity. Low temperature studies have shown that coercivity Hc of nanotubes follows the thermal activation model. Temperature dependence of Hc follows the 3/2 power law for the field dependence of energy barriers.

Calculation of the exchange integrals for Co1-xNix alloy by Korring-Kohn-Rostoker method

In this work we investigate the cobalt-nickel alloy magnetic properties. Calculations of lattice constants for Co, Ni and Co1-xNix alloy with different concentrations were performed with the VASP framework. Calculations of the exchange integrals were carried out using the SPR-KKR package (spin-polarized relativistic Korring-Kohn-Rostoker method). For pure ferromagnets, the Co exchange interaction is ferromagnetic. For Ni, the exchange interaction of the nearest neighbors also is ferromagnetic, but the exchange interaction of the next nearest neighbors has a very weak antiferromagnetic character. In the Co1-xNix alloy, the exchange interaction of the nearest neighbors JNi–Co1 and JCo–Co1 increases with increasing nickel concentration. The next nearest neighbors exchange interaction at a concentration of Ni x ≥ 0.5 has an antiferromagnetic character.

MWCNTs and carbon onions grown by CVD method on nickel-cobalt alloy nanocomposites prepared via novel alcogel electrolysis technique and its oxygen evolution reaction application

Novel nanocatalyst designs to synthesize carbon based electrocatalyst are highly desirable for the production of sustainable energy technologies like hydrogen through electrochemical water splitting. Herein, we report alcogel electrolysis technique to prepare nickel cobalt alloy nanoparticles in silica matrix and then growth of carbon nanostructured material by chemical vapour deposition (CVD) method for its application towards electrochemical catalysis of oxygen evolution reaction. The growth conditions of carbon nanostructures specially multiwalled carbon nanotubes (MWCNTs) and carbon onions are tuned by controlling the temperature of CVD. It is found that MWCNTs at temperature of 650 °C are preferentially formed while carbon onions are formed predominantly at 750 °C. The onion like carbon formed on Ni-Co alloy nanostructures at temperature of 750 °C is attributed to over growth of NiCo alloy nanoparticles achievable at higher temperatures. The diameter of MWCNTs were found to be in the range of 5–25 nm while carbon onions in the range 50–100 nm as revealed by TEM studies after etching silica particles by HF. The oxygen evolution reaction activity of the sample synthesized at 750 °C was found to be inferior than exhibited by MWCNTs formed at 650 °C which was possibly due to the presence of bigger size carbon onions having a less surface area. The overpotential exhibited by NiCo-MWCNTs is 340 mV which is just 35 mV higher than bench mark Ir/C catalyst. The better OER performance exhibited by NiCo-MWCNTs is devoted to encapsulated nickel-cobalt alloy particles by well graphitized carbon layers, defective side walls of nanotubes and oxygenated functional groups (C=O, C–O) which are proven active sites for OER.

Crystal structure and mechanical properties of nickel–cobalt alloys with different compositions: A first-principles study

The properties of nickel–cobalt alloys depend greatly on their composition. In this study, we investigated the crystal structure and mechanical properties (elastic properties and hardness) of nickel–cobalt alloys with different compositions based on first-principles calculations. The formation enthalpy (ΔH) values were calculated and the results showed that as the cobalt content increased in the alloys, the crystal structure of the alloys changed from face centered cubic (fcc) to hexagonal close-packed (hcp), and a coexistence zone with both the fcc and hcp phases existed when the cobalt content was 50–80 at.%. The formation enthalpy values for the fcc-phase and hcp-phase were equal when the cobalt content was 65.5 at.%. The results were in good agreement with the experimental results. Calculations of the elastic properties showed that increasing the cobalt content of the alloys could increase the stiffness as well as improving the compression and shear resistance, but the ductility was reduced. The hardness increased for the fcc and hcp phases as the cobalt content increased. When the cobalt content was 50 at.%, the hardness reached the maximum value of 1032 HV. Further analyses of the electron localization function demonstrated that the increases in the compression and shear resistance, stiffness, and hardness of the nickel–cobalt alloys as the cobalt increased could be attributed to the enhanced covalent bonds between Ni–Co and Co–Co atoms.

Nickel–cobalt alloy doping phosphorus as advanced electrocatalyst for hydrazine oxidation

Seeking high activity non-noble-metal electrocatalysts is essential to develop high performance hydrazine fuel cells. In this study, an electrocatalyst of phosphorus doped nickel-cobalt alloy is fabricated for hydrazine oxidation reaction (HzOR). A series of physical and electrochemistry results show that, among as-prepared four electrocatalysts, the NiCoP/C has the lowest Tafel slope, the highest current density, the longest durability and relative low apparent activation energy for HzOR. Moreover, the influences of KOH and N2H4 concentrations, scanning speeds as well as the temperatures as to NiCoP/C electrocatalyst towards HzOR are also investigated. Besides, electrochemical impedance test exhibits as-obtained NiCoP/C owes good charge transfer kinetics. This work would stimulate more study to explore P doped non-noble metal electrocatalyst in the future.

Thermodynamics of oxygen solutions in manganese-containing Ni – Co melts

Nickel-cobalt alloys are widely used in modern technology. Manganese is one of the alloying components in these alloys. Oxygen is a harmful impurity in Ni – Co alloys; it presents in the metal in dissolved form or in the form of oxide nonmetallic inclusions. The presence of oxygen in these alloys degrades their service properties. The study of oxygen solution thermodynamics in manganese-containing Ni – Co melts is of considerable interest for the practice of such alloys production. Thermodynamic analysis of oxygen solutions in manganese-containing Ni – Co melts has been carried out. The equilibrium constant of interaction of manganese and oxygen dissolved in the nickel-cobalt melts, the activity coefficients at infinite dilution, and the interaction parameters characterizing these solutions were determined for melts of different composition. In the interaction of manganese with oxygen in Ni – Co melts, the oxide phase, in addition to MnO, contains NiO and CoO. The values of the mole fractions of MnO, NiO and CoO in the oxide phase were calculated at 1873 K for different manganese concentrations in Ni – Co melts. In the case of nickel melt, even when manganese content is higher than 0.1 %, the mole fraction of manganese oxide is close to unity. As the cobalt content in the melt increases, the mole fraction of manganese oxide in the oxide phase decreases. In the case of pure cobalt, it is close to unity with manganese contents above 0.7 %. The dependences of the oxygen solubility on contents of cobalt and manganese in the studied melts were calculated. In nickel-cobalt melts, manganese is characterized by a high affinity for oxygen. The deoxidizing ability of manganese decreases with increasing cobalt content in the melt. In pure cobalt it is significantly lower than in pure nickel. The oxygen solubility curves in manganese-containing Ni – Co melts pass through a minimum, the position of which shifts to the higher manganese content with an increase in cobalt content in the melt.

On the Role of Support in Metallic Heterogeneous Catalysis: A Study of Unsupported Nickel–Cobalt Alloy Nanoparticles in Ethanol Steam Reforming

(Co, Ni) bimetallic nanoparticles have been prepared by reducing Ni and Co chloride solutions with sodium borohydride. The obtained materials have been characterized as cast and/or after annealing by means of XRD, magnetic measurements, IR spectroscopy, FE-SEM and TEM microscopies. The resulting nanomaterials, originally amorphous, crystallize into the cubic structure cF4-Cu as homogeneous (Co, Ni) solid solution alloy and with the additional presence of Boron containing phases due to the residual preparation impurities. The bimetallic nanoparticles are active in ethanol conversion in the presence of steam. For low Boron catalysts, the addition of Nickel to Cobalt nanoparticles improves the catalytic activity in ethanol steam reforming allowing yields as high as 87% at 773 K, at high space velocities (GHSV 324,000 h−1). The performances of the catalytic unsupported nanoparticles with a Ni/Co atomic ratio equal to 0.26 appear to be better than those of conventional supported catalysts. The state of Boron impurities affect catalytic activity of bimetallic (Co, Ni) NPs. Carbonaceous materials, such as carbon nanotubes and graphitic carbon, form on the catalyst surface upon reaction.

Wear Resistance of a Composite Galvanic Coating Based on the Nickel-Cobalt Alloy

In modern engineering the great attention is paid to the creation and implementation of new electroplating coating to ensure the durability, hardness and corrosion resistance. One of the effective methods for improving the properties of composite coatings is the method of galvanic deposition. The principle of obtaining of the composite electroplating was based on the fact that together with the metals ion some disperse particles of different sizes and nature are co-deposited. By including into metal matrix the particles are improve the performance coatings and increase the reliability and durability of products. The chloride electrolyte for application of the wear-resistant composite galvanic coating of nickel-cobalt-silicon oxide system was designed. The influences of the electrolysis modes and the electrolyte composition to a physical mechanical properties of the coating (wear resistance, firmness to corrosion, micro-hardness, internal stress, porosity, adhesion) were investigated. The possibility of the usage of received coating as the firmness to corrosion material with anti-frictional properties was showed.

Corrosion Resistance of VC–FeCr and VC–FeCrСо Coatings Obtained by Supersonic Gas-Flame Spraying

We study coatings of the VC–FeCr system with a thickness of 100 μm on a substrate of D16 aluminum alloy deposited by the method of supersonic gas-flame spraying (High Velocity Oxygen Fuel Flame Spraying Process; propane–oxygen fuel). For comparison, we apply the method of plasma spraying of coatings in a dynamic vacuum guaranteeing the highest quality of gas-thermal coatings. The powders for spraying were produced by the method of mechanical alloying with the use of a planetary mill. As initial components, we used powders of vanadium carbide, ferrochrome, and a cobalt–nickel alloy. We evaluate the corrosion-electrochemical properties of the coatings in a 3% NaCl solution at a temperature of 20 ± 0.2°С and show that they are characterized by high corrosion resistances, which correlates with their porosity. As a result of long-term holding of samples with coatings in a 3% NaCl solution, we observe the penetration of the corrosive medium to the coating–substrate interface, which may lead to underfilm corrosion and exfoliation of the coating. It is shown that a VC–FeCrCo coating whose porosity does not exceed 0.5% obtained by the plasma method in a dynamic vacuum has the lowest corrosion resistance. Its corrosion currents are twice weaker than for the coating obtained by the HVOF method.

Morphological variation of electrodeposited nanostructured Ni-Co alloy electrodes and their property for hydrogen evolution reaction

Nanostructured nickel-cobalt alloys of the content of Co varying from 0% to 75% for hydrogen evolution reaction were fabricated by galvanostatic electrochemical deposition processes. With the incorporation of Co into Ni matrix, the morphologies of Ni-Co alloys are changed from nanocones to lamellar structure and finally evolved to a mixed shape of nanocone structure and lamellar structure. Among these Ni-Co alloys, the optimal Ni-60%Co alloy exhibits outstanding electrocatalytic activity with a small hydrogen overpotential of −180 mV and follows Volmer-Tafel mechanism. Better performance of Ni-60%Co can be attributed to the synergetic combination of Ni and Co and unique complex mesh structure which provides the enlarged exposure of catalytically active sites. In addition, Ni-60%Co alloy also displays good electrochemical stability under 10 h galvanostatic test. With prominent electrochemical properties, Ni-60%Co alloy has a certain advantage in the catalytic hydrogen evolution material.

Corrosion- and Hydrogen-Resistance of Heat-Resistant Blade Nickel-Cobalt Alloys

We study the influence of gas-turbine fuel ash and gaseous hydrogen on the mass losses caused by longterm corrosion and the mechanical properties of heat-resistant CM-88U-VI, CM-90-VI, and CM-104-VI cast blade materials. It is shown that the level of sulfide-oxide corrosion resistance of the investigated alloys (CM-104-VI > CM-90-VI > CM-88U-VI) correlates with the chromium content. The highest resistance (among similar materials) is exhibited by CM-104-VI alloy, especially for long-term hightemperature tests. The CM-90-VI single-crystal alloy proves to be least sensitive to the action of hydrogen in short-term tensile tests carried out within the temperature range 20–900°C under a pressure of 30 MPa.

Effective conversion of cellobiose and glucose to sorbitol using non-noble bimetallic NiCo/HZSM-5 catalyst

The tandem hydrolysis and hydrogenation of saccharides into sorbitol is an especially attractive reaction in the conversion of biomass. Here, an economical and efficient bimetallic catalyst for the transformation of glucose and cellobiose into sorbitol is reported. Non-precious metal based catalysts such as NiCo, Ni, and Co, were prepared via modified impregnation method, and NiCo/HZSM-5 showed superior performance for the synthesis of sorbitol (86.9% from cellobiose, 98.6% from D -glucose). Various characterizations, such as Brunner-Emmet-Teler (BET), X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), confirmed that NiCo alloy formed and highly dispersed in NiCo/HZSM-5 catalyst. The high performance of fabricated catalyst would be attributed to the formation of nickel-cobalt alloy over HZSM-5 zeolite surface. High temperature and H2 pressure were favorable for the tandem hydrolysis and hydrogenation reaction. Besides, the reaction pathway was also proposed based on the kinetics study. Cellobitol was detected as the intermediate in the reaction mixture. Furthermore, in the catalytic stability study, it was found that active metal species of NiCo/HZSM-5 were stable. The deactivation of catalyst would be due to the covering of acidic sites over NiCo/HZSM-5.

Efficiently electrocatalytic oxidation of benzyl alcohol for energy- saved zinc-air battery using a multifunctional nickel–cobalt alloy electrocatalyst

We investigate the possibility of utilizing benzyl alcohol oxidation reaction to replace sluggish oxygen evolution reaction (OER) for the charging process in a rechargeable zinc-air battery, catalyzed by NiCo alloy nanoparticles supported on activated carbon (NiCo/AC) with the multifunctional electrocatalytic activities of the oxygen reduction, oxygen evolution and benzyl alcohol oxidation reactions. As an electrocatalyst for the oxygen reduction reaction (OER), NiCo/AC exhibits superior catalytic activity with an onset potential of 0.85 V (vs. RHE), a half-wave potential of 0.74 V (vs. RHE) and a large limiting current density of 4.65 mA cm−2 at 0.2 V (vs. RHE). Moreover, NiCo/AC also demonstrates the electrocatalytic oxidation activities toward water and benzyl alcohol, moreover, the benzyl alcohol oxidation reaction is more thermodynamically and kinetically favourable with 254 mV smaller overpotential than water oxidation at 10 mA cm−2. Owing to these advantages, NiCo/AC as air cathode material is assembled into a home-made rechargeable zinc-air battery, resulting an almost 200 mV lower charging voltage at the current density of 50 mA cm−2 in the presence of 0.1 M benzyl alcohol compared to the battery without benzyl alcohol, consequently obtaining 10.5% energy saving at the charging current density of 50 mA cm−2 with high durability.

Subjective somatic symptoms among victims of offensive behaviors at the workplace

Nanostructured nickel-cobalt alloys of the content of Co varying from 0% to 75% for hydrogen evolution reaction were fabricated by galvanostatic electrochemical deposition processes. With the incorporation of Co into Ni matrix, the morphologies of Ni-Co alloys are changed from nanocones to lamellar structure and finally evolved to a mixed shape of nanocone structure and lamellar structure. Among these Ni-Co alloys, the optimal Ni-60%Co alloy exhibits outstanding electrocatalytic activity with a small hydrogen overpotential of −180 mV and follows Volmer-Tafel mechanism. Better performance of Ni-60%Co can be attributed to the synergetic combination of Ni and Co and unique complex mesh structure which provides the enlarged exposure of catalytically active sites. In addition, Ni-60%Co alloy also displays good electrochemical stability under 10 h galvanostatic test. With prominent electrochemical properties, Ni-60%Co alloy has a certain advantage in the catalytic hydrogen evolution material.

Optimization of Mechanical Properties of Nickel-Cobalt Coatings from Sulphamate Baths

Nickel-cobalt alloys are important coating materials due to their magnetic properties [1-2],wear resistance [3-4] and electrocatalytic properties [5]. Their deposition from sulfamateelectrolytes has many advantages including low internal stress, homogenous deposition athigh current densities, high current efficiencies and higher hardness as compared to theconventional Watts electrolyte [6]. A statistical experimental design was used to study theeffects of boric acid and nickel chloride concentrations, bath temperature and applied currentdensity on nickel coatings in sulphamate baths. After the optimization of the electrolytecomposition, effects of pH and Co additions to the electrolyte were investigated. The coatingthickness and its distribution were measured by XRF techniques. Microhardness, surfacemorphology and internal stress of coatings were also determined. It was found that Coaddition to the electrolyte and operation at higher pH yielded deposits of higher Co contentand enhanced hardness up to a certain point.

Cobalt–nickel alloy catalysts for hydrosilylation of ketones synthesized by utilizing metal–organic framework as template

The facile synthesis of CoNi@NC materials from a MOF precursor is reported along with the catalytic properties in ketone hydrosilylation.