Ni Powders Research Articles

In Situ Medium Entropy Intermetallic Reinforced Composite Coating Fabricated by Additive Manufacturing

The possibility of stabilizing different amounts of medium-entropy intermetallic compounds (MEIMCs) within a multicomponent matrix using laser cladding is demonstrated. The results indicated that MEIMC with a B2 structure could be successfully formed within a multicomponent BCC matrix during laser cladding of a proper ratio of Al, Fe, Co, Cu, Mn, and Ni powders. Two coatings with different contents of MEIMC were fabricated by changing the feeding rate of the powder mixture. Based on the X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) analyses, the Al-rich intermetallic particles were qualitatively identified as (Fe0.55Co0.18Cu0.22Ni0.03Mn0.02)Al MEIMC. It was also found that the feeding rate affects the content of MEIMC, and consequently, the grain structure and microhardness values. Finally, we propose MEIMC-reinforced alloys as a more effective alternative system to be used for fabricating high-performance coatings using laser cladding.

ULTRAFINECOPPER AND NICKEL POWDERS IN THE ELECTRO-CATALYTIC HYDROGENATION OF ORGANIC COMPOUNDS

Ultrafine copper and nickel powders are synthesized by a chemical reduction of the metal cations from their salts in an aqueous ethanol solution without and with the addition of a polymer stabilizer (polyvinylpyrrolidone and polyvinyl alcohol). The structure and morphological features of the prepared metal powders were investigated by X-ray phase analysis and electron microscopy. The electrocatalytic properties of the Cu and Ni powders have been studied in the electrohydrogenation of acetophenone, nitrobenzene, p-nitroaniline, and cyclohexanone. A higher electrocatalytic activity of Cu powders, as well as skeletal copper, was established in the electrohydrogenation of the first three of the listed compounds in comparison with nickel powders, which is explained by the ability of copper cations to be reduced from its oxides in the electrochemical system under investigation. It is shown that the use of polymer stabilizers in the synthesis of Cu and Ni powders contributes to reducing metal particle sizes, but does not increase the electrocatalytic activity of the corresponding metal powders.

Preparation of Ni–Ti composite powder using radio frequency plasma spheroidization and its laser powder bed fusion densification

In this study, spherical Ni–Ti composite powder was synthesized from blended elemental Ni and Ti powders using radio frequency plasma spheroidization process. The effects of powder feeding rate and carrier gas flow rate on the spheroidization efficiency and Ni content of the obtained powders were investigated. The spherical Ni–Ti composite powder with a slightly Ti-rich composition was obtained at the optimal feeding rate of 35 g/min and carrier gas flow rate of 3 L/min. In addition to NiTi phase, elemental Ni and Ti powders were also identified in the produced powder. The prepared powder was adopted for laser powder bed fusion densification. Microcracks and pores were observed in the L-PBF-processed samples. In addition to NiTi main phase, un-melted elemental powders, Ti2Ni and Ni3Ti phases were found in the microstructure of the printed parts. Based on the DSC analysis, the transformation temperatures of austenitic NiTi to martensite and vice versa were determined.

Fabrication of ZnO/NiO:rGO coated Ni foam binder-free electrode via hydrothermal method for supercapacitor application

ZnO/NiO:rGO nanocomposite coated Ni foam binder-free electrode (ZNR/NF) and powder sample (ZNR) were synthesized through hydrothermal technique for supercapacitor applications. The synthesized powder sample have been characterized by XRD and FT-IR analysis to identify its crystalline nature and functional groups, respectively. Raman spectra of the prepared GO and rGO samples, elucidate that the rGO possess lower structural defects than GO. The uniform distribution of ZNR sample on Ni foam substrate was illustrated by SEM analysis. Besides, the nanostructures of ZnO and NiO and its fringe patterns were confirmed by HR-TEM analysis. The high purity of the ZNR and binder-free electrodes were revealed by EDS analysis. The electrochemical properties were tested under 1 M KOH electrolyte, ZNR/NF binder-free electrode exhibited a maximum of 622.3 F g−1 specific capacitance at 1 A g−1. Also, it delivers a maximum power and energy density of 2460 W kg−1 and 16.7 W h kg−1 respectively. The fabricated binder free electrode possesses 85.7% electrochemical retention after 10,000 GCD cycles and it was the one of the key advantages for long term applications.

Thermal Spray Multilayer Ceramic Structures with Potential for Solid Oxide Cell Applications

The objective of this paper is to manufacture free-standing solid oxide cells (SOCs) through the atmospheric plasma spray process (APS), without the aid of a metallic support nor the need for a post-process heating treatment. A five-layered cell was fabricated. Fused and crushed yttria-stabilized zirconia (YSZ) powder in the 5–22 μm particle size range was used in order to achieve a dense electrolyte layer, yet still permitting satisfactory ionic diffusivity. Nickel oxide (NiO) powder that was obtained by in-house flame spray (FS) oxidation of pure nickel (Ni) powder was mixed and sprayed with the original Ni-YSZ feedstock, so as to increase the porosity content in the supporting electrode. Two transition layers were sprayed, the first between the support electrode and the electrolyte (25% (Ni/NiO)–75% YSZ) and the second at the electrolyte and the end electrode interface (50% YSZ–50% lanthanum strontium manganite (LSM)). The purpose of intercalation of these transition layers was to facilitate the ionic motion and also to eliminate thermal expansion mismatches. All the as-sprayed layers were separately tested by an in-house developed acetone permeability comparative test (APCT). Electrodes with adequate porosity (25–30%) were obtained. Concerning electrolytes, relatively thick (150–200 µm) layers derived from fused and crushed YSZ were found to be impermeable to acetone, while thinner YSZ counterparts of less than 100 µm showed a low degree of permeability, which was attributed mostly to existent microcracks and insufficient interparticle cohesion, rather than to interconnected porosity.

Bi-functional modular graphene network with high rate and cycling performance

Three-dimensional bi-functional modular graphene network (3D bmG) is developed by using metal powder assisted soluble salt templates method. The 3D bmG contains two kinds of modules with different functions: the 3D graphene catalyzed by Ni powder (3D bmG-n) and the 3D graphene grown on NaCl crystals (3D bmG-s). The 3D bmG-n with high crystallization degree ensures the high electrical conductivity and structural stability and protects the 3D bmG-s from etching in electrolyte. The 3D bmG-s with more defects and pores provides high capacity and rate properties. Thus, the synergistic effects of the two modules endow the 3D bmG excellent electrochemical performance as both cathode and anode of lithium-ion capacitors (LICs). The as-prepared “all-carbon” bmG//bmG full LIC with a high voltage window of 4.5 V presents high energy densities of 278 Wh kg−1 and 52.2 Wh kg−1 at power densities of 405 W kg−1 and 16200 W kg−1, respectively, and excellent cycling stability with a capacity retention ratio of 88.57% after 3000 cycles, which is superior compared with LICs reported previously. These properties indicate promising application of 3D bmG in high performance energy storage devices, and the modular design in this work will inspire more designs and types of 3D materials.

Development of Ni + TiB2 metal matrix composite coating on AA6061 aluminium alloy substrate by gas tungsten arc cladding process

In the present research work Ni + TiB2 metal matrix composite coating was deposited on AA6061 aluminium alloy substrate using nickel and titanium diboride as precursor by gas tungsten arc cladding process. The TIG torch was used as heat source to melt the preplaced powder mixture. The mixture of TiB2 and Ni powders were taken as 10 wt% and 90 wt% respectively. The three level of currents were used as variable parameters to melt the pre-placed powder layer viz. 120Amp, 140Amp and 150Amp. The microstructure of coated layer was investigated by field emission scanning electron microscope (FESEM) and the chemical composition of the coated layer was detected by energy dispersive spectroscopy (EDS). From the microstructural study it was found that the coating exhibits good metallurgical bond between coated layer and substrate. For analyzing the micro-hardness of coated layer Vickers micro hardness testing was performed along the cross-section of the coated samples. The maximum microhardness value of coated layer was 1233 HV, for sample cladded at current of 150 Amp. It was observed that increase in micro hardness value of coated sample was about 11 times higher than that of the aluminium alloy substrate (110HV). It was found that with increase in applied current, amount of microhardness of coated sample increased.

Fabricating TiNiCu Ternary Shape Memory Alloy by Directed Energy Deposition via Elemental Metal Powders

In this paper, a TiNiCu shape memory alloy single-wall structure was fabricated by the directed energy deposition technique with a mixture of elemental Ti, Ni, and Cu powders following the atomic percentage of Ti50Ni45Cu5 to fully utilize the material flexibility of the additive manufacturing process to develop ternary shape memory alloys. The chemical composition, phase, and material properties at multiple locations along the build direction were studied, using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Vickers hardness testing, tensile testing, and differential scanning calorimetry. The location-dependent compositions of martensitic TiNi and austenitic TiNi phases, mechanical properties, and functional properties were investigated in detail. Variations were found in atomic compositions of Ti, Ni, and Cu elements along the build direction due to the complex interaction between elemental powders and laser processing. Good correlations were present among the chemical composition, phase constituent, hardness, and feature of phase transformation temperatures at various locations. The ultimate tensile strength of the as-deposited TiNiCu alloy is comparable with the previously reported additively manufactured TiNi binary alloys. By adding Cu, a much lower thermal hysteresis was achieved, which shows good feasibility of fabricating ternary TiNiCu shape memory alloys, using elemental powders in the directed energy deposition to adjust the thermal hysteresis.

Fine grained titanium carbonitride reinforcements for laser deposition processes of 316L boost tribocorrosion resistance in marine environments

316L stainless steel has recently gained relevance as metal for additive manufacturing thanks to its high versatility in many laser deposition processes combined with its excellent mechanical and corrosion properties. However, its use in oil & gas, marine or biomedical applications is limited by its poor tribocorrosion performance, since it is prone to wear-accelerated corrosion. On the quest for extending the applicability of 316L components deposited by laser processes to tribocorrosion applications, the present work develops 316L laser claddings reinforced with titanium carbonitride grains. An agglomerated and sintered (Ti,Mo)(C,N)-Ni powder was designed for preserving the chemical integrity of the hard phases during the laser deposition process. This results in 316L composites with homogeneously distributed titanium carbonitride reinforcements with a size ranging from sub-micrometre up to about 2 µm. These 316L composites improve the tribocorrosion performance in artificial seawater by over 10 fold in open circuit potential conditions and over 30 fold at an applied passive potential. The passivity of the 316L composites is maintained even though of a lower break down potential. These results highlight the enormous potential of 316L reinforced with titanium carbonitride deposited by laser processes for wear resistant components operating in saline environments.

Computational and experimental investigation on mechanical behavior of zirconia toughened alumina and nickel powder reinforced EN31 based composite material

AbstractIn the present investigation, EN31 steel alloy based composite material has been developed using zirconia toughened alumina as primary reinforcement material and Ni powder as secondary reinforcement material. The weight percent of zirconia toughened alumina varied from 1.25 % to 10 %. While Ni powder weight percent has been kept uniform (2.5 %). The microstructure of the composite material developed showed uniform distribution of reinforcement particles. Results showed that wettability of zirconia toughened alumina particles improved by adding the nickel particles in EN31 steel alloy. Tensile strength and hardness after the heat treatment were found to be 899 MPa and 120.12 BHN respectively for EN31/6.25 wt.% zirconia toughened alumina/2.5 wt.% nickel composite material. Results showed that tensile strength and hardness of EN31 steel alloy improved about 46.17 % and 100.20 % respectively after adding 6.25 % zirconia toughened alumina and 2.5 % nickel powder. However, ductility reduced by adding the zirconia toughened alumina and nickel powder in EN31 steel alloy. The Finite element analysis has also been carried out to predict the deformation and damage behavior of investigated material during tensile test process. In addition, Brinell hardness test process finite element analysis model is also developed. The finite element analysis results are in good agreement with experimental results with 5 % of percentage difference.

Cold Gas-Dynamic Spray for Catalyzation of Plastically Deformed Mg-Strips with Ni Powder.

Magnesium hydride (MgH2) has received significant attention due to its potential applications as solid-state hydrogen storage media for useful fuel cell applications. Even though MgH2 possesses several attractive hydrogen storage properties, it cannot be utilized in fuel cell applications due to its high thermal stability and poor hydrogen uptake/release kinetics. High-energy ball milling, and mechanically-induced cold-rolling processes are the most common techniques to introduce severe plastic deformation and lattice imperfection in the Mg/MgH2. Furthermore, using one or more catalytic agents is considered a practical solution to improve both the de-/rehydrogenation process of MgH2.These treatments are usually dedicated to enhance its hydrogen storage properties and deduce its thermal stability. However, catalyzation of Mg/MgH2 powders with a desired catalytic agent using ball milling process has shown some disadvantages due to the uncontrolled distribution of the agent particles in the MgH2 powder matrix. The present study has been undertaken to employ a cold gas-dynamic spray process for catalyzing the fresh surfaces of mechanically-induced cold-rolled Mg ribbons with Ni powder particles. The starting Mg-rods were firstly heat treated and forged 200 times before cold rolling for 300 passes. The as-treated ribbons were then catalyzed by Ni particles, using cold gas-dynamic spray process. In this catalyzation approach, the Ni particles were carried by a stream of Ar gas via a high-velocity jet at a supersonic velocity. Accordingly, the pelted Ni particles penetrated the Mg-substrate ribbons, and hence created numerous micropores into the Mg, allowed the Ni particles to form a homogeneous network of catalytic active sites in Mg substrate. As the number of coating time increased to three times, the Ni concentration increased (5.28 wt.%), and this led to significant enhancement of the Mg-hydrogen storage capacity, as well as improving the de-/rehydrogenation kinetics. This is evidenced by the high value of hydrogen storage capacity (6.1 wt.% hydrogen) and the fast gas uptake kinetics (5.1 min) under moderate pressure (10 bar) and temperature (200 °C). The fabricated nanocomposite MgH2/5.28 wt.% Ni strips have shown good dehydrogenation behavior, indicated by their capability to desorb 6.1 wt.% of hydrogen gas within 11 min at 200 °C under 200 mbar of hydrogen pressure. Moreover, this system possessed long cycle-life-time, which extended to 350 h with a minimal degradation in the storage and kinetics behavior.

Composite Si–Ni nanoparticles produced by plasma spraying physical vapor deposition for negative electrode in Li-ion batteries

Si–Ni composite nanoparticles have been produced by a single and continuous plasma spray physical vapor deposition (PS-PVD) from Si and Ni powder feedstocks and their electrochemical performances as anode in lithium-ion batteries (LiB) are investigated. Si nanoparticles with 20–40 nm on which Ni is directly attached with Si/NiSi2 epitaxial interface are formed spontaneously through co-condensation of high temperature elemental gas mixtures during PS-PVD. When only a little amount of Ni is added to Si, the effect of the epitaxial Ni attachment on the Si nanoparticles becomes evident; the cycle capacity is appreciably improved to reach a 1.6 times higher capacity than that of the Si only cell after 50 cycles, due to reduced charge-transfer resistance and nanosized Si particle. In contrast, excessive Ni addition to Si feedstock leads to formation of various silicides as a result of the accelerated silicidation during PS-PVD, which results in a significant decrease in the cycle capacity due to reduction of the active Si phase amount despite reduced charge-transfer resistance.

Improved ferroelectric and piezoelectric properties of (Na0.5K0.5)NbO3 ceramics via sintering in low oxygen partial pressure atmosphere and adding LiF

Dense ([Formula: see text][Formula: see text]NbO3 lead-free ceramics with the simple composition were prepared via sintering in low oxygen partial pressure (pO2, [Formula: see text][Formula: see text] atm) atmosphere and adding LiF. All the ceramics have pure orthorhombic structure. Compared to the LiF-added ([Formula: see text][Formula: see text]NbO3 ceramics sintered in air and the low pO2-sintered pure ([Formula: see text][Formula: see text]NbO3 ceramics without LiF addition, the present ceramics exhibit improved piezoelectric and ferroelectric properties. The piezoelectric constant [Formula: see text] is 125 pC/N, and the converse piezoelectric constant [Formula: see text]* is 186 pm/V. The dielectric constant and dielectric loss of the ceramics at room temperature and 1 kHz are 451 and 0.03, respectively. Under the measured electric field of 70 kV/cm, the remanent polarization is 25.9 [Formula: see text]C/cm2 and the coercive field is 13.9 kV/cm. Furthermore, if the base metals such as Cu and Ni powders were mixed into the green pellets and sintered in the low pO2 atmosphere, the base metals cannot be oxidized, suggesting possibility of using base metals as electrodes.

Study on Coating Material and Preparation Technology of Aluminum Alloy Tube by Low Temperature Self-Propagating Molding

Low temperature self-propagating forming coating material system for aluminum alloy cylinder parts was designed with Al, Fe2O3, Mo, Cu, Ni and Ti powders as raw materials. Low temperature self-propagating wear-resistant coating was prepared on the inner wall of aluminum alloy cylinder parts by thermal spraying ignition condensation centrifugal self-propagating fusion technology. XRD, DSC and SEM were used to study the microstructure, thermodynamic properties and cross-section morphology of the coating after thermal reaction of four kinds of low-temperature self-propagating materials with different proportions. The preparation process parameters of the coating were optimized by orthogonal test, including the amount of coating, the rotation speed of self-propagating centrifuge and the reaction time of self-propagating coating. The results show that the addition of Si, Mo and Zn powders in the four low temperature self-propagating powder systems can reduce the occurrence temperature of aluminothermic reaction; the optimal process parameters for coating preparation are rotational speed of 2000r/min, powder filling amount of 0.9g/cm3 and rotational reaction time of 16S.The results show that the coating with 20wt.% Al, 60wt.% Fe2O3, 12wt.% Si, 4wt.% Mo and 4wt.% Zn has better density and interface adhesion.

Influence of Cr and Al to FeCoNiCr x Al2-x alloys synthesised by mechanochemistry

In this study, soft magnetic FeCoNiCrAl high-entropy alloys (HEAs) were synthesised by high-energy ball milling using Fe, Co, Ni, Cr and Al powders as raw materials. The phase evolution was detected by X-ray diffraction, and the results showed that only 12 h were required to convert all the raw materials into the HEAs nanoparticles. It was shown that the prepared particles formed aggregates of approximately 1 μm in size. Furthermore, the influence of the amounts of Cr and Al on the formation process, magnetic properties and microwave absorption of the FeCoNiCr x Al2-x alloys was investigated. The saturation magnetisation reached 80.43 emu g−1 when x = 1, and the minimum calculated reflection loss reached 41.99 dB at 2.40 GHz with a layer thickness of 4.2 mm when x = 1.5.

Ni coatings for corrosion protection of Mg alloys prepared by an in-situ micro-forging assisted cold spray: Effect of powder feedstock characteristics

Three nickel (Ni) powders, i.e. gas-atomized spherical Ni (GA-Ni), carbonyl irregular Ni (C-Ni), and electrolytic dendritic porous Ni (E-Ni), were sprayed on magnesium alloys by an in-situ micro-forging assisted cold spray method. Although all deposited coatings present extremely low porosity, the C-Ni and E-Ni coatings reveal poorer inter-particle bonding than GA-Ni coating. Electrochemical tests reveal that the inter-particle gaps will act as fast pathways for the corrosive media to penetrate the coatings, thereby the GA-Ni coating with intimate inter-particle boundaries can isolate the corrosive media for 3000 h and the C-Ni and E-Ni coatings fail after <10 h corrosion.

Sliding wear behavior of cold-sprayed Ni-WC composite coatings: Influence OF WC content

Metal Matrix Composites reinforced with WC particles and Co or Ni as matrices are well-known for their unique combination of hardness, toughness, and thus superior wear performance. Previous studies showed that the structure of the coating including carbide size and content, and morphology as well as matrix/binder microstructure must be carefully tailored to achieve desirable wear properties. In this study, Ni–WCNi composite coatings were deposited using the cold spray. Agglomerated WCNi powders and spherical Ni powders were used as feedstock materials. It was found that Ni–WCNi coatings can be tailored to contain 13-54 vol% WC and display a varied hardness ranging between 225 and 550 HV1. A higher concentration of WC in initial feedstock led to more compaction of WCNi particles in coatings, the lower mean free path between WC particles, and harder coatings. The sliding wear behavior of coatings was studied with a sliding speed of 3 mm/s under normal loads of 5 and 12 N. Coatings with higher WC fill ratios were found to be more wear-resistant than coatings with less or no WC. This is related to the uniform distribution of WC particles with the lower mean free path that minimized adhesive wear at the initial stages of wear and helped to develop a higher coverage of protective mechanically mixed layers. However, the protective role of mechanically mixed layers was reduced at higher load, caused by subsurface crack propagation at WC particle interfaces, and was related to strain accumulation in highly compacted WC coatings. A qualitative comparison of coating cohesion strengths was performed using scratch tests on the polished cross-section of coatings and correlated to wear properties.

Laser welding 6061 aluminum alloy with laser cladding powder

To solve the problem of low absorption and welding surface collapse in the laser welding of the 6061 aluminum alloy, the powder was first added to the surface of the weld by laser cladding. The effect of laser cladding powder type on the microstructure and hardness of the 6061 aluminum alloy was studied. The results show that laser cladding of single Al powder, Si powder, and Ni powder can all improve laser absorption during laser welding of aluminum alloy, but each material has specific limitations, such as reducing the number of strong phases, generating other phases, and the nonevening of phases. Two kinds of mixed powder, Al:Si and Al:Ni, can overcome these limitations to a certain extent. Laser cladding with three kinds of mixed powder resulted in a better welding effect than when using two kinds of mixed powder or a single powder. By applying an extreme vertices design, the optimum ratio of Al-Si-Ni powder was determined as 0.737:0.185:0.078, resulting in the uniform microstructure of the weld without delamination. The mechanical properties test shows that the hardness of the laser cladding with powder was better than that without laser cladding powder, and the tensile strength of the weld was 83% of the base material.

The Formation and Elastic Behavior of TiNi Intermetallic Sintered From a TiH2–Ni Powder Mixture

The Formation and Elastic Behavior of TiNi Intermetallic Sintered From a TiH2–Ni Powder Mixture

Parameters of crystal and electronic structure and magnetic properties of mechanically alloyed Ni3C cubic carbide

The cubic Ni3.3C carbide has been fabricated by mechanical alloying of elemental Ni powder and the multiwalled carbon nanotubes in a high energy planetary ball mill. Crystal structure of carbide obtained belongs to the defective structure of ZnS sphalerite type according to x-ray diffraction data. Parameters of the electronic structure of Ni3.3C were calculated by linearized muffin-tin orbitals method within the plane-wave approximation using as an input the defined parameters of crystal structure. Magnetic properties, such as temperature and field dependences of the magnetic susceptibility of Ni3.3C have been studied. Based on experimental data obtained by studying the crystal structure and magnetic properties of Ni3.3C, as well as on the basis of calculations of electronic structure parameters, a preferred displacement of the carbon atoms in tetrahedral voids of Ni crystal lattice has revealed.