Ni Nanowires Research Articles

Wettability, Diffusion Behaviors, and Modeling of Ni Nanoparticles and Nanowires in Brazing Inconel 718

Ni nanoparticles (NPs) and nanowires (NWs) are compared as brazing filler metals for joining Inconel 718. NWs significantly enhance the strength of brazed joints compared to NP joints (270 MPa). Herein, joints formed with a pure NW pellet and a NW–NP mixed pellet yield average lap shear bonding strengths of 319.2 and 370 MPa, respectively. The experiment displays that the contact angle in brazing with NPs is higher than that with NWs. A modified Hart's equation is also proposed for predicting the effective interdiffusion coefficients of nanomaterials that account for surface diffusion in addition to lattice and grain boundary diffusion. The diffusion coefficients calculated by the modified Hart's equation are consistent with the values determined by Sauer–Friese analysis for NPs, but for NWs, the diffusion coefficients determined by Sauer–Friese are mainly controlled by grain boundary diffusion, significantly higher than those predicted by the modified Hart's equation due to size‐dependent transient liquid phase diffusion. This explains the enhanced brazing strength with NW fillers.

Peroxidase-like recyclable SERS probe for the detection and elimination of cationic dyes in pond water

A peroxidase-like MOF coated magnetic surface-enhanced Raman scattering (SERS) probe as Ni@Mil-100(Fe)@Ag nanowires (NMAs) was developed, which can detect multiple cationic dyes with a good recyclability and a high sensitivity. Specifically, Mil-100(Fe) with peroxidase-like activity was fabricated on the magnetic prickly Ni nanowires through layer-by-layer (LBL) method. With the presence of 10 mM H2O2, hydroxyl radical (•OH) produced by peroxidase-like catalytic reaction of Mil-100(Fe) layer can easily eliminate the pollution molecules within 1 min without any requirement for expensive equipment or complicated process. The magnetic NMAs can provide a rapid refreshment for at least 10 times. In addition, carboxyl-functionalized Mil-100(Fe) can not only increase the decoration efficiency of Tollens but also promote the selective enrichment of the cationic dyes, which endows the probe with a greatly improved sensitivity with a limit of detection (LOD) as low as 10−10 M for crystal violet (CV). Following the erasure by H2O2, multiple cationic fishery drugs in pond water can be sequentially detected. Such a recyclable SERS probe holds a great potential in various applications as aquaculture, biomedicine and chemical analysis.

Controllable voltammetric formation of a structurally disordered NiOOH/Ni(OH)2 redox pair on Ni-nanowire electrodes for enhanced electrocatalytic formaldehyde oxidation

In present work, we report on the enhanced electrocatalytic activity of formaldehyde oxidation in alkaline media for modified Ni nanowires (NWs)-based electrodes. Electrochemically deposited Ni NWs composed of metallic Ni and surface NiO were modified in KOH via cyclic voltammetry using different scan rates (10, 200 and 400 mV s−1) in order to transform an inactive NiO to the surface-catalytic-active structurally disordered β-NiOOH/β-Ni(OH)2. Various characterisations (XRD and FT-IR) and calculations based on the electric charge were performed to understand the surface transformations which were found to be scan-rate dependant. The cyclic voltammetry results and kinetic parameters (Tafel plot) of formaldehyde oxidation revealed the superior electrocatalytic activity of the Ni-NW-electrode modified at 200 mV s−1. The enhanced electrocatalytic performance, i.e., decreased onset overpotential by 400 mV when compared to Ni-based electrocatalysts, of this electrode was attributed to the thickness of structurally disordered the Ni–NiOOH/Ni(OH)2 and composite layered structure that enables the electron injection to reduce the NiOOH work function and thus promote the catalysis of formaldehyde oxidation. The proposed technique provides advances with a novel synthesis strategy for the preparation of highly active, structurally disordered β-Ni(OH)2/β-NiOOH redox systems on the surface of Ni-based nanostructured electrocatalysts for HCHO oxidation.

General Fabrication of 3D Hierarchically Structured Bamboo-like Nitrogen-Doped Carbon Nanotube Arrays on 1D Nitrogen-Doped Carbon Skeletons for Highly Efficient Electromagnetic Wave Energy Attenuation.

Hierarchically three-dimensional (3D) micro-nanostructures have promising applications in multifarious fields. Herein, we report a general strategy, that is, in situ catalysis process, for fabrication of nitrogen-doped carbon nanotube (NCNT) arrays on one-dimensional (1D) nitrogen-doped carbon (NC) skeletons. The NCNT arrays branch out from the 1D NC surfaces, resulting in the formation of hierarchically 3D micro-nanostructures. The strategy is involved in the pyrolysis of M-precursor (M = Fe, Co, and Ni) nanowires with the assistance of dicyandiamide. During the synthesis process, the metal components in the precursors serve as catalysts for growing NCNTs, while dicyandiamide provides carbon and nitrogen sources. With the ongoing reaction, the NCNTs were catalytically grown and branched out from 1D NC skeletons. Through the strategy, three kinds of hierarchically 3D structures with encapsulated Fe/Fe3C, Co, and Ni nanoparticles, respectively, were fabricated successfully. As functional materials for attenuating electromagnetic wave energy, these hierarchically 3D structures exhibit satisfactory performances even at a low matching thickness, exceeding most of the carbon-based materials. Typically, the minimal reflection losses of the 3D structures can reach -10.0 dB even as the matching thickness is in the range of 1.4-2.0 mm. Experimental results demonstrate that the excellent attenuation properties toward electromagnetic wave energy are relative to high conduction loss at a low frequency and high dielectric relaxations at a high frequency as well as better impedance matching with the input impedance of the free space. Our method presented here opens a general way for the development of hierarchically 3D carbon-based micro-nanostructures for their practical applications.

Influence of orientation and temperature on the mechanical properties and deformation behavior of nickel nanowire under bending: A large scale molecular dynamics simulation

The present work reports the mechanical properties of Ni nanowire (NW) of different orientations ([0 1 0] (orientation −1); [1 1 1] (orientation-2); [1–10] (orientation-3)) and temperatures (10 K, 100 K and 300 K) via molecular dynamics (MD) simulations using a three-point bending test. For the above studies Ni NW of size 100 Å (x-axis) × 1000 Å (y-axis) × 100 Å (z-axis) is considered. Embedded atom method potential is used for Ni-Ni atomic interaction. From the load–displacement curves, Young’s modulus and yield strength are calculated. With the increase of NW temperature, a decrease in Young’s modulus and yield strength values are noticed. Twisting of NW is observed only at orientation-2 NW at 300 K and orientation-3 NW at all three temperatures under bending. Fracture of NW at the left rigid region is noticed only at 100 K samples for orientation-2 and orientation-3.

Electronic Structure and Chemistry of Nanomaterials Embedded in a Matrix Using Atomically Resolved Near-edge Structures: The Example of Ferromagnetic Ni Nanowires Grown in SrTiO3

Electronic Structure and Chemistry of Nanomaterials Embedded in a Matrix Using Atomically Resolved Near-edge Structures: The Example of Ferromagnetic Ni Nanowires Grown in SrTiO₃

Mechanical and vibrational characteristics of functionally graded Cu–Ni nanowire: A molecular dynamics study

Functionally graded material (FGM) is a class of advanced materials, consisting of two (or more) different constituents, that possesses a continuously varying composition profile. With the advancement of nanotechnology, applications of FGMs have shifted from their conventional usage towards sophisticated micro and nanoscale electronics and energy conversion devices. Therefore, the study of mechanical and vibrational properties of different FGM nanostructures is crucial in exploring their feasibility for different applications. In this study, for the first time, we employed molecular dynamics (MD) simulations to investigate the mechanical and vibrational properties of radially graded Cu–Ni FGM nanowires (NW). Distribution of Cu and Ni along the radial direction follows power-law, exponential and sigmoid functions for FGM NWs under consideration. Our results demonstrate that distribution function parameters play an important role in modulating the mechanical (elastic modulus and ultimate tensile strength) and vibrational (natural frequency and quality factor) properties of FGM NWs. The study also suggests that elastic moduli of FGM NWs can be predicted with relatively good accuracy using Tamura and Reuss micromechanical models, regardless of NW diameter. We found that Euler-Bernoulli beam theory under-predicts the natural frequencies of FGM NWs, whereas He-Lilley model closely approximates the MD results. Interestingly, FGM NWs are always found to exhibit beat vibration because of their asymmetrical cross sections. Finally, this is the first atomistic scale study of FGMs that directly compares MD simulations with continuum theories and micromechanical models to understand the underlying mechanisms that govern the mechanical and vibrational properties of FGM NWs in nanoscale.

Magnetic field strength controlled liquid phase syntheses of ferromagnetic metal nanowire

The effect of the external magnetic field strength on the morphology of metal nickel (Ni) nanowires synthesized via electroless deposition is investigated. Under strong magnetic fields, Ni nanoparticles, precursors of Ni nanowires, easily align along the magnetic field to form straight nanowires with smooth surfaces. In contrast, under weak magnetic fields, branched Ni nanowires with rough surfaces are formed. By leveraging this magnetic effect on the morphology of Ni nanowires, simply changing the external magnetic field can synthesize various types of Ni nanowire nonwovens. Furthermore, different forms of Ni nanowires were grown on the sheet by the similar electroless deposition reaction on a non-magnetic copper metal sheet. The macroscopic morphology of this composite is closely correlated with the microstructures of Ni nanowires.

Possible Effects of Antiferromagnetic Crystalline Phases on the Temperature Dependence of Coercivity for Ni and Co Nanowires Obtained by Electrodeposition

Herein, the structural and magnetic properties of Ni and Co nanowires obtained by electrodeposition on alumina membranes are studied. Structural analysis shows the coexistence of Ni and Co metallic phases as well as NiO and CoO, which are associated with the preparation method. The magnetic study suggests the possibility of unidirectional anisotropy as a possible mechanism on the magnetization reversal in nickel and cobalt nanowires. For the experimental curves of coercivity versus temperature, there exists a critical value, below which only the dipole interactions are predominant. Above this temperature, the dipole magnetocrystalline and magnetostrictive energy compete in a complicated way. Alongside these three contributions, the coexistence of the “local unidirectional coupling” of antiferromagnetic nanoparticles that engage in random directions on nanowires is proposed.

Aligned Ni nanowires towards highly stretchable electrode

Easy fabrication of super-stretchable electrodes can pave the way for smart and wearable electronics. Using drop casting unidirectional nickel nanowires with polyurethane matrix, we fabricated a super-stretchable film with high electric conductivity. The as-fabricated film can withstand a 300% tensile strain in the direction perpendicular to nanowires, owing to the transformation of percolating nanowire network from 2D to 3D. In contrast to the decreased film conductivities under large tension in most stretchable electrodes, which usually associate with fractures and irreversible deformations, our film conductivity can increase with the applied strain This probably benefits from the enhanced electrical contacts between twisted nanowires under tension The developed super-stretchable film with unprecedented behavior in this work sheds light on the facile fabrication of super-stretchable electrodes with durable performance

Ordered Mesoporous Ni-P Amorphous Alloy Nanowire Arrays: High-Efficiency Catalyst for Production of Polyol from Sugar.

Mesoporous metals have shown significant potential for use in catalysis; however, controllably synthesizing highly ordered mesoporous amorphous alloys is a serious challenge. In this paper, a synthesis strategy was developed for generating ordered amorphous alloy nanowire arrays from mesoporous Ni-P by combining mesoporous silica templating with electroless plating. Mesoporous silica is externally grafted with -CH3 and internally covered with -NH2 acting as an efficient template, ensuring the formation of Ni-P nanowires inside the pore channels and endowing the final product with an ordered mesoporous array structure. The resulting ordered mesoporous Ni-P amorphous alloy nanowire arrays were subjected to a liquid-phase sugar hydrogenation to polyols and exhibited a highly superior catalytic performance (97% glucose conversion and 94% maltose conversion) within 4 h at 4 MPa hydrogen pressure and 373 K relative to those reference catalysts, including conventionally prepared Ni-P amorphous alloy nanoparticles (87% glucose conversion and 86% maltose conversion), ordered mesoporous Ni nanowire arrays (90% glucose conversion and 87% maltose conversion), and the commercial Raney Ni catalyst (76% glucose conversion and 66% maltose conversion). According to a comparative study, the enhanced catalytic efficiencies can be ascribed to the integration of amorphous alloy properties and mesoporous material characteristics. The composition- and morphology-controllable synthesis presented here might supply a general synthetic methodology for rationally designing ordered mesoporous amorphous alloys for a broader range of applications.

Co–Ni nanowires supported on porous alumina as an electrocatalyst for the hydrogen evolution reaction

Water electrolysis is a promising way to produce hydrogen fuel, but many electrocatalytic systems require electrodes made of noble metals such as platinum. There is a demand for high-efficiency, low-cost materials to replace these noble metals. Herein, porous anodic alumina (AAO) templates are prepared by direct current (DC) constant voltage anodization and the step-down method. Cobalt, nickel and Co–Ni alloy nanowires are then prepared by alternating current (AC) electrodeposition. This nanoarray system can be employed in fuel cells to minimize the use of precious metals and reduce the cost of the cathodes. The pores of the AAO template are uniform with a size range from 35 to 75 nm. Using cyclic voltammetry (CV) and linear sweep voltammetry (LSV), the Co–Ni nanowire array prepared on AAO by this method is shown to have a low overpotential for hydrogen evolution and excellent stability.

High extinction ratio terahertz broadband polarizer based on the aligned Ni nanowire arrays.

We present a broadband terahertz (THz) polarizer based on the stacks of aligned Ni nanowire (NW) arrays. We demonstrated that the polarizer has an extinction ratio of 58.8 dB and an average extinction ratio of 46.6 dB throughout a frequency range of 0.3-2.3 THz. Compared to carbon-nanotube and metallic wire-grid polarizers, our Ni-NW polarizers with rapid, reliable, low-cost fabrication processes are ideal candidates for emerging THz technologies.

Efficient solar steam generation by using metal-versatile hierarchical nanostructures for nickel and gold with aerogel insulator

Metallic nanostructure-based solar absorbers are widely used owing to their controllable range of absorption wavelengths and various potential applications. Metal-versatile solar absorbers that are not limited to noble metals are essential to reduce production costs. In this study, broadband solar absorbing surfaces were fabricated based on Ni or Au-deposited self-aggregated alumina nanowire structures. A high solar absorptance was obtained for both the Ni-deposited nanowire structures (~0.90) and Au-deposited nanowire structures (~0.92), indicating the advantage of using nickel instead of the noble metal. These high solar absorptance were theoretically analysed by comparing the electric field distributions obtained from finite-difference time-domain(FDTD) simulations and the dielectric functions of Ni and Au. In addition, efficient solar steam generation platform was designed using these broadband solar absorbers and aerogel thermal insulator. The solar steam generation efficiency was improved through heat localisation using an aerogel as a thermal insulator and a polyvinyl alcohol (PVA) sponge as a water supplier. The efficiencies of the solar steam generation platforms using black Ni and Au films under an illumination of 5 kW m−2 were 83.8% and 78.3%, respectively.

Promoting Alkaline Hydrogen Evolution Catalysis on P-Decorated, Ni-Segregated Pt–Ni–P Nanowires via a Synergetic Cascade Route

Although both the water dissociation and intermediates’ (H* and OH–) adsorption/desorption are two critical steps for alkaline hydrogen evolution, very little effort has been expended to target the latter step to further boost the alkaline hydrogen evolution catalysis. To overcome this limitation, we designed phosphorus (P)-modified, nickel (Ni)-segregated platinum (Pt)–Ni nanowires as highly efficient electrocatalysts for alkaline hydrogen evolution. The segregated Ni can be evolved into Ni(OH)x as the active site for water splitting. Then, the modified P with high oxophilicity on the catalyst surface serves as a site to anchor OH–, largely preventing the competitive adsorption of OH– and H* on active Pt sites as well as promoting the adsorption and desorption rate of H*. Consequently, it achieves excellent activity and stability in 1 M KOH with a current density as high as 42.5 mA/cm2 (@–0.07 VRHE) and limited overpotential decay after 18 h long-term test, outperforming most reported alkaline hydrogen evolution reaction electrocatalysts.

Magnetostatic dipolar anisotropy energy and anisotropy constants in arrays of ferromagnetic nanowires as a function of their radius and interwall distance

Magnetostatic dipolar anisotropy energy and the total dipolar anisotropy constant, , in periodic arrays of ferromagnetic nanowires have been calculated as a function of the nanowire radius, the interwall distance of the nanowires in the arrays and the geometry of the array (square or hexagonal), by using a realistic atomistic model and the Ewald method. The simulated nanowires have a radius size up to 175 Å that corresponds to 31 500 atoms, and the simulated nanowire arrays have interwall distances between 35 and 3000 Å. The dependence of total magnetostatic dipolar anisotropy constant on the nanowire radius, their interwall distance and the type of array symmetry has been analyzed. The total dipolar anisotropy constant, which is the sum of the intrananowire dipolar anisotropy constant, , due to the dipolar interactions inside an isolated nanowire and the main responsible of the shape anisotropy, and of the internanowire dipolar anisotropy constant, , due to the magnetostatic dipolar interactions among nanowires in the array, have been calculated and compared with the magnetocrystalline anisotropy constant for three nanowire compositions and their crystalline structures. The simulations of the nanowire arrays with large interwall distances have been used to calculate the intrananowire anisotropy constant, , and to analyze the competition between the intrananowire, internanowire and magnetocrystalline anisotropies. According to some magnetic theories, the ratio equals to the areal filling fraction of a nanowire array. Present calculations indicate that the equation for the areal filling fraction matches perfectly for any interwall distance and radius of Ni and Co nanowire arrays. This first equation is used to write a general equation that relates the radius and interwall distance of nanowire arrays with the intrananowire, internanowire and magnetocrystalline anisotropies. This general equation allows to design the geometry of nanowire arrays with the desired orientation of the easy magnetization axis.

Room temperature selective sensing of aligned Ni nanowires using impedance spectroscopy

Room temperature gas sensing behavior of arrayed one-dimensional (1D) nickel nanowires (Ni NWs) are investigated using impedance spectroscopy. Ni nanowires synthesized via electrochemical deposition method based on anodic aluminum oxide (AAO) templates. Their structural characterization verified by scanning electron microscopy (SEM), x-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) analysis. Impedance spectroscopy as an essential technique utilized to understand the mechanism of gas interaction with the wires through the changes in their electronic behavior. Bode and Nyquist plots with the real and imaginary impedances are plotted versus frequency range of 500 Hz to 2 MHz at different relative humidity values (varying from 30% to 70%) and ethanol vapor concentrations (varying from 2 to 18 ppm). The equivalent circuits are proposed and simulated for impedance responses to both humidity and ethanol vapors. The impedance plots indicate the increase in resistance of the aligned nanowires at low frequencies by the adsorption of water and ethanol molecules.

Pd modified Ni nanowire as an efficient electro-catalyst for alcohol oxidation reaction

Developing highly efficient and economically viable electro-catalyst is very crucial research topic nowadays for achieving affordable direct alcohol fuel cells. Nano-structural architecture plays a crucial role in the catalytic activity. Herein we are reporting, a cost effective one-dimensional (1D) nano structured electro-catalyst for improved methanol oxidation reaction. Pd modified Ni nanowire catalyst towards methanol electro oxidation were prepared by a simple galvanic replacement reaction. Exclusive nano-wire morphology achieved through a wet chemical reduction method without employing any capping agents or surfactants. Pd modified Ni nano-wires exhibited a supreme catalytic activity and durability towards methanol electro-oxidation. The distinctive 1D morphology and strong metal support interaction (SMSI) between Pd and NiO along with the bifunctional effects of Pd and Ni attributed to the enhanced catalytic activity. The amount of precious Pd metal was reduced by 90 wt% with enhanced catalytic efficiency. Ethanol electro-oxidation study showed an improved catalytic activity with mass activity of 1479.79 mA/mg Pd.

Lavender-Like Ga-Doped Pt3Co Nanowires for Highly Stable and Active Electrocatalysis

One-dimensional (1D) PtM (M = Fe, Co, Ni) nanowires (NWs), which represent a thriving class of electrocatalysts for fuel cells, are experiencing a restriction in long-term durability because of the...

Thermal Stability of Nano-Crystalline Nickel Electrodeposited into Porous Alumina

Through-pores alumina membranes of 50 μm thickness and 70 × 70 mm size have been fabricated to deposit Ni nanowires by electrochemical processing. Due to highly ordered microstructure of the membranes, the pores were filled by nanowires almost to 100%. The membrane nanowires composite morphology, structure and thermodynamic characteristics have been studied by scanning electron microscopy, atomic-force microscopy, X-ray diffraction and differential thermal analysis. The thermal stability of Ni nanowires into porous alumina template and whole composite was determined.