Nickel Tungsten Research Articles

Elemental tungsten, tungsten–nickel alloys and shotgun ammunition: resolving issues of their relative toxicity

Failure to distinguish between elemental tungsten and tungsten alloys has caused confusion, especially about their relative toxicity in shotgun ammunition. Controlled experiments indicate that the carcinogenicity of embedded tungsten–nickel–cobalt alloys derives from their nickel and cobalt content, and not the tungsten. The carcinogenicity of metallic nickel and cobalt implants in animal tissues is well-established. Studies in which pure tungsten metal is embedded in animal and human tissues indicate that there is no toxicity or carcinogenicity developed locally or systemically. The exposed tungsten corrodes slowly in the tissue fluids and is excreted from the body. Chronic studies in which pure tungsten-based shot are placed, continuously, in the foregut of ducks over 150 days indicate that there are no adverse physiological effects, nor disruption of ducks’ reproduction and development of their progeny. This type of shot is environmentally safe and non-toxic to animals. Shot containing nickel could pose health problems to animals if embedded in their tissues. The use of known toxic metals in lead-free shot should be subjected to further examination and, if warranted, regulation.

Hydrocracking of vacuum gas oil in the presence of catalysts NiMo/Al2O3–amorphous aluminosilicates and NiW/Al2O3–amorphous aluminosilicates

Supported nickel–molybdenum and nickel–tungsten hydrocracking catalysts prepared using a support that consists of 70% Al2O3 and 30% amorphous aluminosilicate were characterized by nitrogen and mercury porosimetry, IR spectroscopy of adsorbed CO, and high-resolution electron microscopy. The catalytic tests in hydrocracking of vacuum gas oil containing 3.39% sulfur showed that the nature of the hydrogenating component (NiMo or NiW) only slightly influences the vacuum gas oil conversion and the diesel fraction yield, but noticeable influences the properties of the diesel fraction obtained. The catalyst NiMo/Al2O3–amorphous aluminosilicates, compared to NiW/Al2O3–amorphous aluminosilicates, ensures lower sulfur content in the diesel fraction obtained, whereas the catalyst NiW/Al2O3–amorphous aluminosilicates allows obtaining a diesel fraction with lower content of polyaromatic compounds.

Sliding wear behavior of electrodeposited Ni–W alloy and hard chrome coatings

Present study deals with the comparative sliding wear behavior of electrodeposited nickel–tungsten (Ni–W) alloy and conventional hard chrome (HCr) coatings. Ni–W alloys with different W (7.4, 10.5 and 11at%) content in Ni were systematically deposited using pulsed electrodeposition from citrate bath. In addition, pure Ni coatings were also obtained from Watt׳s bath for comparison purpose. The dry sliding wear behavior of Ni, Ni–W and HCr coatings was compared using pin on disc configuration against WC–Co disc at three different loads. The results indicate that the wear rate is lowest for NiW10.5 amongst all the coatings despite of the fact that HCr coating is 12% harder than NiW10.5 coating. The wear behavior was attributed to ductile wear mechanism in NiW10.5 coatings as opposed to brittle fracture in the case of HCr coatings.

Highly flexible conductive fabrics with hierarchically nanostructured amorphous nickel tungsten tetraoxide for enhanced electrochemical energy storage

Amorphous nickel tungsten tetraoxide (NiWO4) nanostructures (NSs) were successfully synthesized on a flexible conductive fabric (CF) using a facile onestep electrochemical deposition (ED) method. With an applied external cathodic voltage (–1.8 V for 15 min), the amorphous NiWO4 NSs with burl-like morphologies adhered well on the seed-coated CF substrate. The burl-like amorphous NiWO4 NSs on CF (NiWO4 NSs/CF) are employed as a flexible and binder-free electrode for pseudocapacitors, which exhibit remarkable electrochemical properties with high specific capacitance (1,190.2 F/g at 2 A/g), excellent cyclic stability (92% at 10 A/g), and good rate capability (765.7 F/g at 20 A/g) in 1 M KOH electrolyte solution. The superior electrochemical properties can be ascribed to the hierarchical structure and large specific surface area of the burl-like amorphous NiWO4 NSs/CF. This cost-effective facile method for the synthesis of metal tungsten tetraoxide nanomaterials on a flexible CF could be promising for advanced electronic and energy storage device applications.

Characterization of tungsten–nickel simultaneous Ohmic contacts to p- and n-type 4H-SiC

Ohmic contacts to p- and n-type 4H-SiC using refractory alloyed W:Ni thin films were investigated. Transfer length measurement test structures to p-type 4H-SiC (NA = 3 × 1020 cm−3) revealed Ohmic contacts with specific contact resistances, ρc, of ∼10−5 Ω cm2 after 0.5 h annealing in argon at temperatures of 1000 °C, 1100 °C, 1150 °C, and 1200 °C. Contacts fabricated on n-type 4H-SiC (ND = 2 × 1019 cm−3) by similar methods were shown to have similar specific contact resistance values after annealing, demonstrating simultaneous Ohmic contact formation for W:Ni alloys on 4H-SiC. The lowest ρc values were (7.3 ± 0.9) × 10−6 Ω cm2 for p-SiC and (6.8 ± 3.1) × 10−6 Ω cm2 for n-SiC after annealing at 1150 °C. X-ray diffraction shows a cubic tungsten–nickel–carbide phase in the Ohmic contacts after annealing as well as WC after higher temperatures. Auger electron spectroscopy depth profiles support the presence of metal carbide regions above a nickel and silicon-rich region near the interface. X-ray energy dispersive spectroscopy mapping showed tungsten-rich and nickel-rich regions after annealing at 1100 °C and above. W:Ni alloys show promise as simultaneous Ohmic contacts to p- and n-SiC, offering low and comparable ρc values along with the formation of WxNiyC.

Nickel‐Molybdenum and Nickel‐Tungsten Dithiolates: Hybrid Models for Hydrogenases and Hydrodesulfurization

AbstractThe heterobimetallic complexes [(dppe)Ni(pdt)Mo(CO)4], [(dcpe)Ni(pdt)Mo(CO)4], [(dppe)Ni(pdt)W(CO)4] and [(dcpe)Ni(pdt)W(CO)4] {dppe = Ph2P(CH2)2PPh2; dcpe = Cy2P(CH2)2PCy2; pdt2– = –S(CH2)3S–} have been prepared and structurally characterized. The internuclear separation in these NiIIM0 species is highly sensitive to diphosphine basicity and is smallest in the dppe complexes wherein the planar Ni centres are electron‐poor and require interaction with the group 6 metal. The NiIIW0 species [(dppe)Ni(pdt)W(CO)4] was converted into its stable conjugate acid [(dppe)Ni(pdt)HW(CO)4]+, a rare example of a nickel–tungsten hydride. This NiIIHWII complex is an electrocatalyst for H+ reduction and is relevant to both biological and synthetic H2‐processing catalysts.

Physical Properties of Electroless Nickel-Tungsten Coating on Mild Steels Obtained from Acetic Bath

Electroless deposition of nickel tungsten on mild steel was conducted using acetic bath, containing nickel sulphate and sodium tungstate in the alkaline medium. The influence of sodium acetate and sodium tungstate on deposits was investigated and characterized using scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDX) and x-ray diffraction (XRD) to assess the phase, content and microstructure features. The surface roughness of coating was measured using atomic force microscope (AFM) while the hardness was investigated using Vickers microhardness. The results show that deposits have smooth surfaces, Ra = 0.53 μm, with a nanocrystalline structure, crystallite size hardness of deposits decreases as the concentration of sodium tungstate increases.

Corrosion and wear behavior of laser cladded Ni–WC coatings

A nickel–tungsten carbide (Ni–WC) composite is an ideal protective coating for a harsh environment. In this study, the corrosion and wear behavior of a laser cladded Ni–WC coating fabricated by a high power direct diode laser (HPDDL) with different chemical compositions was investigated. In the modified Ni–60%WC, the chemical compositions were enhanced by the addition of lanthanum oxide (La2O3) and molybdenum and by replacing a portion of micro-sized WC with nano-WC particles. The corrosive resistance of the coatings was investigated utilizing potentiodynamic polarization, long-term immersion tests, and surface analytical techniques. The corresponding wear response was studied by using a dry unidirectional sliding wear test according to the ASTM G99 standard. Modification of the laser-cladded coatings was interpreted on the basis of its microstructure, microhardness, and phases of chemical composition. It has been observed that an optimal addition of nano-WC (5wt.%), La2O3 (1wt.%), and Mo (1wt.%) refines the grain size of the Ni binder and improves hardness, passivation capability of the coating under corrosion, and wear resistance. The pitting corrosive resistance of the modified coatings was enhanced due to a higher chemical stability, a more uniform surface potential, and a higher passivation capability.

Characteristics of Ni–W bimetallic nanoparticle via reactive RF thermal plasma synthesis

Nickel–tungsten binary nanoparticle was synthesized by the inductively coupled radio-frequency thermal plasma process which belongs to vapor phase condensation technology. Nanoparticles are nucleated from supersaturated vapor species. Accordingly, vaporization of feedstock micro-powder is the pre-requisite step for nanoparticle synthesis. In this context, nickel hydroxide and tungsten trioxide micro-powders were chosen for precursor feedstock of each Ni and W because of their low boiling points. It was confirmed that each feedstock was fully vaporized and mostly reduced by argon–hydrogen thermal plasma as the results of pure nanoparticle synthesis from each feedstock. Blended feedstock was prepared by turbulent mixing and the weight fraction of nickel hydroxide in the blended powder was 0.5. Weight fraction of tungsten in the synthesized binary nanoparticle was 0.588 and it was well consistent to theoretical one of blended feedstock (0.556). However, chemical composition at the particle level showed a substantial distribution. Full vaporization of each feedstock resulted in coincidence of overall chemical composition, however, particle level chemical composition distribution was due to inhomogeneous condensation of Ni–W vapor mixture. X-ray diffraction and convergent beam electron diffraction revealed that Ni–W binary nanoparticles were composed of γ-Ni and amorphous phase. Rapid cooling driven co-condensation as well as supersaturating of alloying element and oxygen caused non-equilibrium phase evolution.

Amorphous nickel/cobalt tungsten sulfide electrocatalysts for high-efficiency hydrogen evolution reaction

The hydrogen evolution reaction (HER), an appealing solution for future energy supply, requires efficient and inexpensive electrocatalysts with abundant active surface sites. Although crystalline MoS2 and WS2 are promising candidates, their activity is dominated by edge sites. Amorphous tungsten sulfide prepared so far lacks the required active sites and its application has thus been hampered. In this work, nickel and cobalt incorporated amorphous tungsten sulfide synthesized by a thermolytic process is demonstrated to enhance the HER efficiency dramatically. The amorphous nickel tungsten sulfide (amorphous NiWS) annealed at 210°C delivers the best HER performance in this system boasting a Tafel slope of 55mV per decade and current density of 8.6mAcm−2 at 250mV overpotential in a sustained test for 24h. The introduction of Ni or Co into the catalyst and subsequent thermal treatment alters the porous structure and chemical bonding states thereby increasing the density of active sites on the surface.

Production and Structure of Nickel-Phosphorus Electrolytic Coatings Modified with Metallic Tungsten or Nickel Oxide

Electrodeposited Ni-P, Ni-W-P, Ni-P+W and Ni-P+NiO+W coatings were obtained in the galvanostatic conditions at the current density jdep = -200 mA cm-2. A stereoscopic microscope was used for surface characterization of the coatings. The phase composition of the coatings was determined using X-ray diffraction (XRD) method. The chemical composition of the deposits was determined using atomic absorption spectroscopy (AAS). It was found out that the introduction of the tungsten powder in one case, and the nickel oxide and tungsten powder in the other into the electrolytic Ni-P matrix results in obtaining the coatings with a very rough surface. The coatings obtained in this way may be useful while applying them as electrode materials in electrochemistry.

Coke Minimization during Conversion of Biogas to Syngas by Bimetallic Tungsten–Nickel Incorporated Mesoporous Alumina Synthesized by the One-Pot Route

Dry re-forming of methane with CO2 was investigated over bimetallic W and Ni incorporated mesoporous alumina catalysts prepared by the one-pot sol–gel route. Powdered materials were thoroughly characterized (N2 physisorption, XRD, XPS, SEM-EDX, TGA-DTA, TPH) prior to and after catalytic runs performed at 600 and 750 °C. High surface area W–Ni incorporated mesoporous alumina catalysts (SBET = 178–192 m2/g) synthesized in this work showed excellent performance for the conversion of model biogas to synthesis gas. The Ni–W containing materials exhibited high catalytic activity, which was maintained throughout 150 h of time-on-stream (TOS) long-term operation at 750 °C. Increase of the W loading (0–10–15 wt %) at fixed nickel amount (5 wt %) resulted in prevented deactivation of the catalyst, most prominent at 600 °C, and minimization of coke formation on the surface of the catalyst. Tungsten incorporation was thus proven to significantly enhance and stabilize the overall catalyst performance.

Simulation study on radiation shielding capability of tungsten nickel combination and their alloys

Simulation study on radiation shielding capability of tungsten nickel combination and their alloys

Physical properties of rf magnetron sputter deposited NiO:WO3 thin films

The present study describes various physical properties of mixed nickel–tungsten oxide (NiO:WO3) (95:5) thin films prepared on glass substrate by rf magnetron sputtering due to the variation in rf power (100, 150, and 200 W). X-ray diffraction study shows that all the deposited films are amorphous in nature. The maximum transmittance of 97% in the infrared region was observed for the film deposited at 100 W rf power. A systematic reduction in the optical band gap is observed with increasing rf power, which is associated with the rf power induced effect leading to the production of localized states near the band edges of NiO:WO3. The Urbach energy (EU) value was found to increase with rf power, which may be due to the increased defects in the NiO matrix. From the optical study, we have evaluated various parameters such as refractive index, packing density, lattice dielectric constant, ratio between free carrier density and free carrier effective mass, plasma frequency, and dispersion energy parameters, etc. These results are discussed and correlated well with the light of possible mechanisms underlying the phenomena. The compositional purity of the film was confirmed by energy dispersive x-ray analysis (EDAX) and Auger electron spectroscopic (AES) measurements. The Raman spectra of NiO:WO3 films show two peaks corresponding to one-phonon LO mode at 560 cm−1 and two-phonon LO mode at 1100 cm−1 due to the vibrations of Ni–O bonds and a strong peak at 860 cm−1 corresponds to the stretching vibration of W–O pair in the WO6 group. The band edge emission at 369 nm was observed in photoluminescence spectra.

Processing and microstructural characterization of liquid phase sintered tungsten–nickel–cobalt heavy alloys

In this study, the effects of composition and sintering temperature on the microstructural characteristics of liquid phase sintered 90W–Ni–Co alloys were investigated. 90W–Ni–Co alloys having Ni/Co ratios of 3/1, 4/1 and 6/1 were examined. It was found that the alloys studied have reached almost to full density when sintered at and above 1475°C. The microstructures of the alloys were typical of liquid phase sintered alloys, which consisted of rounded, nearly pure W grains embedded in a ternary Ni–Co–W binder matrix phase. The binder matrix phase in these alloys was observed to dissolve up to 42wt.% W. The relative amount of the binder matrix phase and the average size of the W grains were found to increase with increasing sintering temperature. The activation energies for grain coarsening are determined for the investigated alloys by assuming that the coarsening process is mainly governed by Ostwald ripening mechanisms in the liquid state. The calculated activation energies, which were within 113–162kJ/mol range, were found to be in rather close agreement to the literature data given for W–Ni–Fe alloys. This indicates that grain coarsening in W–Ni–Co and W–Ni–Fe alloys most probably takes place through similar diffusional processes.

Niobium-Based Nickel-Tungsten Hydrotreatment Catalysts with Enhanced Isomerization Properties

A balancing act: The presence of niobium leads to a highly improved performance of nickel–tungsten-based catalysts for the isomerization of cyclohexane (CC6). Importantly, the hydrogenation activity is preserved at high nickel–tungsten ratio and tungsten content.

Effect of substrate temperature on structural and optical properties of nickel tungsten oxide thin films

In this work, we present the substrate temperature induced change in the structural, optical, vibrational and luminescence properties of mixed NiO:WO3 (95:5) thin films deposited on glass substrates by rf magnetron sputtering technique. X-ray diffraction analysis revealed the onset of crystallization of the films occurred at 300 °C. The average optical transmittance of the films varied between 91 and 97 % in the visible region. The refractive index and extinction coefficient of films are found to decrease with increasing substrate temperature. It was observed that the dispersion data obeyed the single oscillator of the Wemple-DiDomenico model, from which the dielectric constants, ratio between free carrier density and free carrier effective mass, plasma frequency, oscillator energy, oscillator strength, and dispersion energy parameters of NiO:WO3 films were calculated and reported for the first time due to variation in substrate temperature during deposition by rf magnetron sputtering. The micro-Raman result shows two broad peaks corresponding to one-phonon LO mode at 570 cm−1 and two-phonon LO mode at 1,100 cm−1 due to the vibrations of Ni–O bonds and the peak found at 870 cm−1 belongs to the W–O mode. Room temperature photoluminescence (RTPL) study exhibits two characteristic emission peaks at 3.32 eV (374 nm) and 2.93 eV (423 nm), which corresponding to the transition of 3d8 Ni2+ ions. We have made an attempt to discuss and correlate these results with the light of possible mechanisms underlying the phenomena.

Corrosion Behavior of WC-Co and WC-Ni in 3.5% NaCl at Increasing Temperature

Tungsten carbides (WC) are widely used as wear resistant components such as seal, valves, rings, nozzle and bearings. But in some processing operations, the environment necessarily includes severe corrosion or extremes of temperatures. In paper reveal, the corrosion performance of commercial cobalt tungsten carbide (WC-6%Co) and nickel tungsten carbide (WC-9%Ni) in seawater with 3.5% salinity. The experiment was performed in four different temperatures (20°C, 40°C, 60°C and 80°C) and the surface structure by corrosion attack was reveal under SEM. The Icorr value of WC-9%Ni is lower than WC-6%Co, elucidate that WC-9%Ni is better in corrosion resistance compare to WC-6%Co. As the temperature increased, the corrosion rate for every material increased as expected. Decreasing in hardness value for both materials reveal that, the material’s hardness decrease after corrosion has attacked.

Hydrodenitrogenation of basic and non-basic nitrogen-containing compounds in coker gas oil

The hydrodenitrogenation (HDN) performance of a Chinese coker gas oil (CGO) was tested in a micro-fixed bed reactor over a nickel–tungsten supported on citric-treated Y zeolite mixed with a titania–silica composite catalyst (NiW/CYCTS) within the temperature range of 360–420°C, operating pressure range of 5.0–8.0MPa, liquid hour space velocity (LHSV) range of 0.5–2h−1, H2/CGO ratio range of 400–1200 (v/v), and H2S concentration range of 1–5wt.%. The effects of these parameters on the relative conversions of total nitrogen (TN), basic nitrogen (BN), and non-basic nitrogen (NBN) compounds were determined. The conversion of TN compounds enhanced as the temperature and operating pressure increased and as LHSV decreased. BN compounds were easier to be removed than NBN compounds; they were also affected more significantly by the reaction conditions. With increasing H2/CGO ratio, the conversion of BN and NBN compounds initially increased and then decreased thereafter. This finding may be attributed to the addition of phenyl-sulfide (PHS) in the feedstock. The kinetic study of the HDN reaction showed that TN, BN, and NBN compounds accorded with the pseudo-first-order kinetic model. The calculation of the rate constants and activation energies indicated that the HDN of NBN compounds controlled the removal of TN compounds. Moreover, the hydrogenation of N-heterocyclic was the controlling step for the conversion of NBN compounds. The results above can guide the development of CGO hydrotreating catalyst. With the information from this paper, the development of CGO hydrotreating catalyst can adjust the properties of the catalyst by decided technology which will favor the removal of NBN containing compounds.

Synthesis of electric discharge alloyed nickel–tungsten coating on tool steel and its tribological studies

The present study examines the method of depositing nickel and tungsten on die steel surface by means of dispersing these elements in dielectric fluid in an electrical discharge alloying (EDA) process. The modified surface was mechanically and metallurgically characterized using Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDX), microhardness tester and Pin-on-disc tribometer. The phase transformations that occurred during EDA process were evaluated by XRD. The deposition of Ni and W on die steel surfaces yielded minimal cracks with excellent metallurgical bonding. Higher hardness (∼1059HV0.3) with little brittleness resulted in superior wear resistance properties, a property which was retained even at elevated temperature.