Fine Nickel Powder Research Articles

Research on the effective thermal conductivity of nickel-based bi-porous capillary wicks: Modeling and validation

This study proposed an analytical model to predict the effective thermal conductivity (ETC) of bi-sized porous capillary wicks with both interstitial pores (formed inside nickel skeleton) and with large pores created by NaCl as the pore-forming agent. The interstitial-pore model was developed utilizing the sintering neck formation theory and thermal resistance network, which was validated by measured data obtained from samples of multiple particle sizes. It is shown that the model works well for fine nickel powders with the root mean square error (RMSE) of 13.8%, while a large deviation was observed when using the coarse powders. Based on the presented interstitial-pore model, an ETC model for samples containing formation pores was formulated. A total of six types of equations were proposed, considering three packing modes and two shapes of formation pores. Samples with NaCl of various granularities (54–75 μm, 88–125 μm) and proportions (2.5, 5.0, 7.5, and 10.0 wt.%) were made for the model validation. The results demonstrated that the bi-porous ETC models, with both interstitial pores and those formed by NaCl, exhibit good performance when applying the BCC configuration, while small and large formation pores can be characterized by spherical and cubic models respectively.

Specific Surface Area Evolution and Shrinkage Control of Pre-Sintered Nickel Clusters

This study prepared pre-sintered clusters with fine nickel powders and proposed an effective method to predict and control the sintering shrinkage based on cluster size. Experiments were conducted to investigate the influence of the pre-sintering temperature and cluster size on the specific surface area and morphology of pre-sintered clusters as well as to validate the availability of the proposed shrinkage prediction method. The results show that the specific surface area decreases with an increasing pre-sintering temperature and slightly oscillates with an increasing cluster size. The linear shrinkage ratio is inversely proportional to the cluster size and decreases with an increasing pre-sintering temperature, which begins to drop rapidly at 500 °C and decreases from 19.05% to 3.18% at 800 °C. The experimental results are quite approximate to the predicted values, which strongly prove the availability of the proposed shrinkage prediction method.

Rapid Solidification and Surfaces Alloying Using Continuous CO<sub>2</sub> Laser to Generate Ni-Aluminide on Steel

Rapidly solidified thin micro-alloyed surface layers are generated by laser melting of plasma thermal sprayed steel surfaces. Samples of carbon steel are plasma sprayed with fine nickel and aluminum powders. Laser surface melting generated a thin localized molten pool of metal with steep horizontal thermal gradient. The latter triggered intense vortex formation in the molten pool which thoroughly mixed the nickel and aluminum powders within the molten pool in a fraction of a second. As the sample is moved away with a predefined velocity, the cold substrate quenched the melt pool, generating rapidly solidified micro-alloyed surfaces. A 2.5 kilowatts continuous carbon dioxide laser was used for surface melting; laser power was maintained at 800 watts while the samples were moved with respect to the laser beam at linear velocities in the range of 100-200 mm/min. The technique generated metallurgical bonded novel surfaces. Depth of the laser modified layer was achieved in the range of 0.2-0.4 mm. Refined microstructures of pre-austenite grain size in the range of 4±2 µm were generated. Micro-hardness measurements of the modified layer indicate an almost three times enhancement in the hardness values; the latter are, in general indicative of mechanical strength of the material. The shape of the solid/liquid interface of the advancing molten pool determines the orientation of the growing dendrites; at higher velocities of sample translation with respect to the laser beam, these are almost parallel to the sample surface. The orientation of the dendrites, the uniformity in surface alloying (within fraction of a second) and the resulting hardness values are explained with the help of the modeled shape of the liquid metal pool. The laser processed material proved to be a flexible technique to synthesize novel surfaces for surface sensitive applications.

Use of nickel filler powder in joining SS304-SS316 through microwave hybrid heating technique

In this work, electromagnetic microwave energy radiations at 2.45 GHz frequency have been utilized to produce 5 mm thick joints of SS304-SS316. Filler powder mixture of fine nickel powder and epoxy blumer 1450XX was taken as interface slurry between the mating faces of the joints. Nano and micro particle sized nickel powder of 70 nm (powder 1), 20 µm (powder 2) and 50 µm (powder 3) were used during three sets of experiments. Activated charcoal powder was utilized as susceptor medium to initiate the microwave heating process. Scanning electron microscopy results showed that the joints were crack free and homogenous. Elemental spectroscopy was carried out to observe and compare the presence of different elemental composition in the joining region with different filler powders.

Recycled and devulcanized rubber modified epoxy-based composites reinforced with nano-magnetic iron oxide, Fe 3 O 4

Abstract Rubber modified epoxy based composites were designed by low cost production methods. Basically, clean and recycled materials were used to provide a solution for manufacturing of lightweight, cost efficient composites in industrial applications such as automotive and aeronautical engineering. In the present study four different compositions have been developed and characterized for their potential usage as structural materials. The matrix was prepared by treatment of epoxy with 10% recycled rubber. Nano-magnetic iron oxide, Fe3O4, was added to the matrix as reinforcement elements in different percentages. Nickel and aluminium were also add as auxiliary additional elements. Measurements of magnetic permeability and dielectrically properties have been carried out for electronic devise applications basically in aeronautical engineering. Dynamic Scanning Calorimeter (DSC) and Dynamic Mechanical Analysis (DMA) were carried out to determine thermo-mechanical properties. Static tests have been carried out by 3-point bending (3PB) tests for mechanical characterization. Furthermore, creep and wear behaviour of these compositions were evaluated by means of nanoindentation tests to analyze time dependent behaviour of these composites. Macro scratch tests were made in very high cycle test conditions for their measurements in long time resistance. Microstructural and fracture surface analyses have been carried out on the scanning electron microscopy (SEM). All of the experiments; scanning electron microscopy, nanoindentation, static (3PB), test results expose a combined effect of toughening mechanisms high strength and ductile, lightweight and low-cost composites based on the rubber modified epoxy composites reinforced with nano magnetic iron oxide and auxiliary fine nickel and nano aluminium powders.

Controlled Dissolution of Copper Coated Ni-Al Powders In 4M NaOH

Copper coatings on fine nickel powder was achieved by autocatalytic deposition using glyoxylic acid as reducing agent. Activation of the Nickel powder was done by using titanium diborate solution and chloro platinic acid. The deposition of the copper particles is carried out by electroless coating. The mechanism and composition of the coating was studied for copper coated Ni-Al powders. The coatings were characterized using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The Copper coatings have reduced the dissolution of Ni-Al powders greatly in alkaline media. The resultant product formed is recommended for relevant Industrial purposes.

Preparation of fine nickel powders via reduction of nickel hydrazine complex precursors

Fine nickel(Ni) powders with controllable particle sizes were synthesized via the reduction of nickel hydrazine complex precursors of pure [Ni(N 2H 4) 2]Cl 2 and a mixture of [Ni(N 2H 4) 2]Cl 2 and [Ni(N 2H 4) 3]Cl 2 in aqueous solution. The mechanism of the formation of metallic Ni powders experiences the reduction of nickel hydroxide by hydrazine released from the ligand exchange reaction between nickel hydrazine complex and NaOH. In comparison with the method of preparing Ni powders from nickel salts, the method of making Ni powders via the reduction of nickel hydrazine complex precursors shows the advantages of using half dosage of hydrazine for complete reduction of nickel ions in solution, and the obtained Ni particles show less agglomeration and better dispersibility. Moreover, the average particle size of nickel powders can be controlled from 180 to 260 nm by adjusting the reaction molar ratio and concentration.

Nickel release from nickel particles in artificial sweat

Nickel is widely used in a broad range of products, primarily made of alloys, used by humans on a daily basis. Previous assessments have shown that skin contact with some such products may cause nickel allergic contact dermatitis, induced by the release of nickel. However, data on nickel release from small nickel particles in artificial sweat for assessment of potential risks of workers in nickel-producing and nickel-using facilities are not available. The objective of this study was to fill this knowledge gap by determining nickel release from fine nickel powder ( approximately 4 microm diameter) of different loadings varying from 0.1 to 5 mg/cm(2), when immersed in artificial sweat. The amount of nickel released increased with increasing particle loading, whereas the highest release rate per surface area of particles was observed for the medium particle loading, 1 mg/cm(2), at current experimental conditions. All particle loadings showed time-dependent release rates, reaching a relative steady-state level of less than 0.1 microg/cm(2)/hr after 12 hr of immersion, whereby less than 0.5% of the nickel particle loading was released. Nickel release from particles was influenced by the surface composition, the active surface area for corrosion, particle size, and loading.

Fabrication of Ni 3Al by hot pressing from element powders

Abstract Ni 3Al intermetallic was synthesized by hot pressing from element powders of nickel, aluminum, and boron. The influences of parameters on the properties of Ni 3Al were investigated. The parameters include the particle size of nickel powder, adding or without boron powder, hot pressing temperature, etc. The properties include the density of hot-pressed samples, resultant ratio of Ni 3Al phase, and bending strength. The microstructures of hot-pressed samples were investigated by X-ray diffraction and scan electronic microscopy, and the properties, such as density and bending strength, were also measured. The results show that a higher bending strength was obtained under the same hot pressing conditions by the fine nickel powder than the coarse one, and there is little difference about density. Boron powder added in this process accelerates the formation of Ni 3Al and markedly increases the hot pressed density. In the temperature range of this study, the density increases along with the hot pressing temperature. Full dense Ni 3Al samples were obtained under the condition of 860°C, 10 min, 45 MPa from Ni-22.89Al-0.5B powder.

Synthesis of Fine Nickel Powders by Solvothermal Method

Fine nickel powders have been prepared by chemical reduction between nickel acetate and alcohol under solvothermal conditions. The effect of adding surfactant and varying solvent on the particle size of the as-synthesized nickel powders have been explored. SEM, XRD and TG were employed to characterize the size, morphology, crystalline structure and the thermal stability of the as-synthesized nickel powders. It is revealed that the FCC-structured nickel powders are of uniform spherical shape with good crystallinity and thermal stability. Typically, nickel powders with an average size of 300 nm were obtained at 200°C for 8 h using 0.04 mol/L solution of Ni(CH3COO)2·4H2O in n-butyl alcohol under solvothermal conditions.

Spark Plasma Sintering of Nanoscale (Ni+Al) Powder Mixture

An attempt was made to produce nickel aluminides with fine microstructure from nanoscale nickel and aluminum powders produced by wire electric explosion (WEE). The powders were mixed and spark plasma sintered (SPS) for simultaneous reaction and densification of the material. Various mixing methods were tested to give the best homogeneity of the nanopowders mixtures. Utrasonic pre-treatment of the powders did not result in any positive effect on mixing homogeneity. Sintered compact contained NiAl and Ni3Al phases, showed fine grain size and unexpectedly high hardness possibly due to the presence of aluminum oxide in the starting nanopowders.

Preparation of fine Ni powders from nickel hydrazine complex

Fine nickel powders with narrow size distribution have been prepared from the reduction of nickel hydrazine complexes in aqueous solution. The pure nickel hydrazine complexes, [Ni(N 2H 4) 3]Cl 2 were prepared with the molar ratio of N 2H 4/Ni 2+ = 4.5, while a mixture of complexes, such as Ni(N 2H 4) 2Cl 2, [Ni(N 2H 4) 3]Cl 2, and [Ni(NH 3) 6]Cl 2 were formed with N 2H 4/Ni 2+ < 4.5. By the X-ray diffraction (XRD), FT-IR, and scanning electron microscopy (SEM) analyses, it was found that the reduction of Ni 2+ to metallic Ni powder proceeded via the formation of nickel hydroxide which was reduced by hydrazine liberated from the ligand exchange reaction between the nickel hydrazine complex and NaOH. The standard deviation of the particle size decreased with the decreasing molar concentration of nickel hydrazine complex while the mean particle size increased. As the amount of hydrazine increased, the surface roughness of the particles was improved significantly due to the catalytic decomposition of the excess hydrazine at the surface of the nickel particle. It was found that average particle size could be controlled from 150 to 380 nm by adjusting the reaction molar ratio and temperature.

Preparation of fine nickel powders in aqueous solution under wet chemical process

Abstract Ultrafine nickel powders have been prepared by chemical reduction of aqueous NiCl2 with hydrazine at various reaction conditions as wet chemical process. The reductive atmosphere was produced by the dissolution of hydrazine hydrate in basic solution. The nickel powders were characterized by the means of an X-ray diffractometry, a scanning electron microscopy, BET method, a thermo-gravimetry and an X-ray photoelectron spectroscopy. In this investigation, the average particle size of the nickel powders decreased by increasing the Ni2+ concentration, and also decreased without agglomeration by the introduction of the surfactant and the 1-propanol containing solvent. It was found that the nickel powders prepared at 60 °C for 45 min using various 1-propanol/water solvents while fixing the molar ratio of N2H4 to Ni2+ at 2.0, Ni2+ concentration at 0.8 M, and Na-CMC at 4.0 g/L were spherical in shape, ranged from 0.27 to 0.85 μm in size, and not agglomerated.

Pasted Ni ( OH ) 2 Electrodes Using Ni Powders for High-Drain-Rate, Ni-Based Batteries

Experimental work was carried out to explore the possibility of using filamentary Ni powder to enhance the rate capability and reduce the usage of cobalt in pasted electrodes for high-drain-rate application. Testing results showed that an extra fine filamentary nickel powder, type 210, as an additive significantly improved the active mass utilization, gravimetric capacity, and volumetric capacity of pasted electrodes at high rates. In addition, the performance gain could be achieved in thicker electrodes using reduced Co content. Coarser filamentary Ni powder, type 255, was also found effective but in a lesser degree than type 210. The major contribution of a filamentary Ni powder was believed to be enhancement of conductivity by means of a secondary conductive network in the active mass within the Ni foam cells, equivalent to a reduction in Ni foam cell size. © 2003 The Electrochemical Society. All rights reserved.

Electrochemical evaluation of sintered metal hydride electrodes for electric vehicle applications

Powder-sintered technology for manufacturing thick metal hydride electrodes has been investigated. A slurry consisting of hydrogen storage alloy mixed with fine nickel powder and some additives was pasted onto porous metal substrate. The results with porous metal substrates were compared with those obtained with nickel foam, perforated nickel strips, perforated copper foil and copper mesh. The effect of sintering parameters on the electrochemical properties of the sintered metal hydride electrode has been characterized. The results show that activation and high-rate dischargeability of the sintered hydride electrode was strongly improved compared to that obtained with conventional pasting processes.

Synthesis of fine nickel powders by glycothermal process

Synthesis of fine nickel powders by glycothermal process

Enantio-differentiating hydrogenation of methyl acetoacetate over fine nickel powder with in situ modification

Enantio-differentiating hydrogenation of methyl acetoacetate (MAA) was carried out using fine nickel powder (FNiP) by adding tartaric acid (TA) and sodium salts to the reaction media (in situ modification) instead of using a conventionally modified nickel catalyst. This catalyst prepared by the in situ modification gave an optical yield up to 79%.

Preparation of Ni powder by mechanochemical process

A solid state displacement reaction between NiCl 2 and Mg, induced by mechanical milling, has been employed for the production of fine nickel powder. The reaction ignites after a definite incubation period, leading to a sharp temperature rise of the vial. The observed overall temperature rise during milling is due to two effects (i) mechanical working, and (ii) chemical reaction. Ignition has been shown to occur as a result of a critical combination of chemical mixing, lattice strain and milling induced temperature rise. This is related to the incubation time observed after a room temperature hold. The reaction product (Ni+MgCl 2) has been leached with dilute HCl to obtain nickel powder which is in the size range of 10–500 nm.

Microstructure of TiNi shape-memory alloy synthesized by explosive shock-wave compression of Ti-Ni powder mixture

Cylinders of TiNi shape-memory alloy were synthesized from mixtures of equiatomic fine irregular titanium and nickel powders by explosive-wave compression with a detonation velocity of about 6500 m s-1. B2 type parent phase, R phase, B19′ type martensite, Ti2Ni, Ti3Ni4 and Ti2Ni3 phases were observed in this as-synthesized material. In the B2 matrix high density dislocations existed. The Burgers vectors of many dislocations were determined to be parallel to \(\left\langle {111} \right\rangle \) directions. The R phase variants formed (0 0 1) B2 twinning structure. The substructure of the B19′ martensite was (0 0 1) B19′ type I twin and stacking faults on the (0 0 1) B19′ plane. When increasing the temperature of the as-synthesized material in a differential scanning calorimeter, no B19 ′ → R → B2 transitions were observed on the temperature range −50 to 100 °C. However, B2 → B19′(R) transitions occurred during the cooling cycle. After heat treating the specimen at 800 °C for 1 h and then ageing at 400 °C for 10 min, both B2 → R → B19′ and B19′(R) → B2 phase transitions were observed.

Sintering of elemental carbonyl iron and carbonyl nickel powder mixtures

Iron-nickel alloys with compositions ranging from pure iron to pure nickel at increments of 10 wt% have been prepared by mixing fine elemental carbonyl iron and nickel powders, and sintering at temperatures between 1200–1350°C. The addition of nickel to iron promoted densification and avoided abnormal grain growth at low concentrations. However the densification was retarded when the iron and nickel had approximately equivalent concentrations. As the concentration of nickel increased, the room temperature structures of the alloys gradually changed from α-Fe into γ-(Fe, Ni), with Fe-30 wt% Ni and Fe-40 wt%, Ni containing both phases. The relative abundance of each phase was determined by the degree of compositional homogeneity achieved in sintering.