Ni Nanowires Research Articles

Morphology and Magnetic Properties of Ni Nanowires in Thin Film Anodic Alumina Templates

The features of the morphology and magnetic properties of Ni nanowire arrays have been studied. Aluminum oxide matrices are used as a template for electrolytic deposition of nanowires. The matrices are obtained by anodizing the aluminum films with a thickness of 2 μm that are formed on glass substrates by high frequency ion sputtering. Electrochemical deposition of the metal is carried out using direct and alternating currents. Morphology and microstructure studies show that the nanowire arrays are polycrystalline and have a branched dendritic structure due to the morphological features of aluminum oxide matrices. A relationship between the magnetization reversal patterns and the modes of electrodeposition of Ni nanowire arrays is established. The process of magnetization reversal of an array of this kind of structures is simulated.

ZnS-zeolitic imidazolate framework nanostructure anchored on Ni nanowires as a bifunctional electrocatalyst for high-efficiency overall water splitting

The design and construction of stable and inexpensive bifunctional catalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) present a challenge in electrocatalytic water splitting. In this study, we utilized zeolitic imidazolate frameworks-8 (ZIF-8) as the precursor to fabricate ZnS-ZIF-8 via facile sulfidation processes. The ZnS-ZIF-8 nanostructures were anchored on the surface of the nickel nanowire (denoted as Ni NWs@ ZnS-ZIF-8 nanocomposite) and their catalytic activity for HER, OER, and overall water splitting were studied. The prepared Ni NWs@ ZnS-ZIF-8 revealed a low overpotentials value of 90 and 260 mV at 10 mA cm−2 for HER and OER in 1.0 M KOH solution, respectively. The alkaline electrolyzer assembled by Ni NWs@ ZnS-ZIF-8 provides a low cell voltage of 1.61 V at 10 mA cm−2 current density to boost the overall water splitting and robust stability for 15 h. The superior electrocatalytic activity of Ni NWs@ ZnS-ZIF-8 is owing to the facile and effective electron transport of Ni NWs, accessible active sites of ZnS-ZIF-8, and as well as the synergistic effect of the nanocomposite structures. This finding presents a viable methodology for synthesizing a proficient noble-metal-free catalyst for energy conversion and storage.

Preparation of Ni Nanowires Covalent Organic Framework Composites with High Electrochemical Stability and Supercapacitor Performance

Preparation of Ni Nanowires Covalent Organic Framework Composites with High Electrochemical Stability and Supercapacitor Performance

Fabrication and Magnetic Behavior of Jellyfish-Like Ni Nanowires Synthesized Using Bilayered Nanoporous Anodic Alumina Templates.

The potential to produce nanostructures with intricate shapes in large quantities holds promise for a range of applications in the fields of nanoelectronics and biomedicine. Here a method for fabricating jellyfish-like Ni nanowires (JFNWs) using bilayered nanoporous anodic alumina templates with through pores of varying diameters in each layer is presented. To assess the capabilities of this method,samples are created with different voltages during the second step of anodization, resulting in distinct geometrical characteristics of the second layer of the template,and subsequently synthesizeNiJFNWs. By employing magnetometry and first-order reversal curve (FORC)method, the magnetic properties are examined and a significant alteration in their magnetic behavior,attributed to the differing shapes of theJFNWsand the magnetostatic interactions within the array,is observed.The study utilizes magnetic force microscopy to evaluate the stray magnetic fields generated by the individualJFNWsand unveils their unusual and asymmetric distribution. Through simulations based on the experimental data, the study analyzes the field- andcurrent-induced domain wall movement in a singleJFNWand their array. The findings revealnon-trivial micromagnetic configurations in these structures, including a remarkable 'corkscrew' state, and allowfor an examination of the process of magnetization switching.

Metal nanowires grown on Cu (100) substrate

We present the growth mechanisms of Ag, Ni, Pd, Co and Fe nanowires on Cu(100) substrate studied by the KMC simulations. It has been allows to found the optimum growth parameters (T, F, θ). Their effects have been discussed in details. The quality of nanowires has been determined by calculating the filling ratio. Our simulations exhibit that the best quality is obtained for Ag NWs. In fact, the maximum filling ratio of Ag NWs is reached for temperature range between 200 and 500 K. The increasing of the deposition flux makes decreases the filling ratio. We get an inverse behavior when the coverage is increased for two different temperatures.

Uniaxial Magnetization and Electrocatalytic Performance for Hydrogen Evolution on Electrodeposited Ni Nanowire Array Electrodes with Ultra-High Aspect Ratio.

Ni nanowire array electrodes with an extremely large surface area were made through an electrochemical reduction process utilizing an anodized alumina template with a pore length of 320 µm, pore diameter of 100 nm, and pore aspect ratio of 3200. The electrodeposited Ni nanowire arrays were preferentially oriented in the (111) plane regardless of the deposition potential and exhibited uniaxial magnetic anisotropy with easy magnetization in the axial direction. With respect to the magnetic properties, the squareness and coercivity of the electrodeposited Ni nanowire arrays improved up to 0.8 and 550 Oe, respectively. It was also confirmed that the magnetization reversal was suppressed by increasing the aspect ratio and the hard magnetic performance was improved. The electrocatalytic performance for hydrogen evolution on the electrodeposited Ni nanowire arrays was also investigated and the hydrogen overvoltage was reduced down to ~0.1 V, which was almost 0.2 V lower than that on the electrodeposited Ni films. Additionally, the current density for hydrogen evolution at -1.0 V and -1.5 V vs. Ag/AgCl increased up to approximately -580 A/m2 and -891 A/m2, respectively, due to the extremely large surface area of the electrodeposited Ni nanowire arrays.

Real-Time TEM Observation of the Role of Defects on Nickel Silicide Propagation in Silicon Nanowires.

Metal silicides have received significant attention due to their high process compatibility, low resistivity, and structural stability. In nanowire (NW) form, they have been widely prepared using metal diffusion into preformed Si NWs, enabling compositionally controlled high-quality metal silicide nanostructures. However, unlocking the full potential of metal silicide NWs for next-generation nanodevices requires an increased level of mechanistic understanding of this diffusion-driven transformation. Herein, using in situ transmission electron microscopy (TEM), we investigated the defect-controlled silicide formation dynamics in one-dimensional NWs. A solution-based synthetic route was developed to form Si NWs anchored to Ni NW stems as an optimal platform for in situ TEM studies of metal silicide formation. Multiple in situ annealing experiments led to Ni diffusion from the Ni NW stem into the Si NW, forming a nickel silicide. We observed the dynamics of Ni propagation in straight and kinked Si NWs, with some regions of the NWs acting as Ni sinks. In NWs with high defect distribution, we obtained direct evidence of nonuniform Ni diffusion and silicide retardation. The findings of this study provide insights into metal diffusion and silicide formation in complex NW structures, which are crucial from fundamental and application perspectives.

Morphology dependent EMI shielding performance of Ag-Ni core-shell nanowires

The proposed work reports a facile chemical reduction method for synthesizing the hierarchical silver-nickel core-shell nanowire structures with controllable morphologies by varying the Ag concentration. The growth of Ni shells around the Ag core to make thorny and smooth Ag-Ni core-shell nanowires is studied for addressing electromagnetic interference (EMI). The synthesized Ag-Ni nanowires show better EMI shielding effectiveness (SE) than Ni nanowires with much-improved absorption loss (SEA). Due to high electrical conductivity (8630 S cm−1), magnetic permeability (44.1 emu/g), and heterojunction core-shell interfaces, the bimetallic nanowires flakes exhibit exceptional average EMI SE of 90.5 dB in the X-band frequency range (8–12 GHz) with a thickness of 0.11 mm, taking specific EMI SE to 822.72 dB/mm. In addition, the EMI shielding performance of the smooth Ag-Ni nanowires showed a 45% enhancement in SEA with marginal change in reflection loss (SER) compared to the thorny ones, indicating high absorption of EM waves. The unique core-shell nanowires with high aspect ratio with tunable physical properties can be ideal candidates for futuristic applications in microwave absorption and electromagnetic interference shielding.

Pulsed magnetization reversal in Ni nanowire

Pulsed magnetic field-induced magnetization reversal in Ni nanowires is investigated using micromagnetic simulation. The pulse amplitude, duration, and size of the nanowire are proven to have substantial impacts on the magnetization reversal process. Increasing pulse amplitude and duration leads to faster magnetization reversal for 10 nm-diameter nanowires. But for 40 nm-diameter nanowires with the same aspect ratio, the pulse parameters have a complicated influence on the magnetization reversal process due to the formation and propagation of magnetic domain walls. Further investigations reveal that applying a pulsed field at a certain angle from the long axis of the nanowire or raising the temperature can significantly accelerate the magnetization reversal process.

Optical analysis of aligned Ni nanowire arrays with different degree of oxidation for terahertz polarizer application

The optical properties of aligned nickel nanowire arrays (NiNWAs) with different degrees of oxidation for terahertz (THz) polarizer applications have been investigated by using THz time-domain spectroscopy. In frequency-domain spectra, the full width at half maxima of transmitted peaks was broadened and the peak positions have a blue shift with increasing oxidation levels, besides the enhancement in peak intensity. It is indicated that the oxidation of Ni nanowires (NWs) has a significant influence on the interaction between Ni NWs and THz wave. The transmittance of the aligned NiNWAs increases with annealing temperature increasing. Conversely, the degree of polarization and extinction ratio (ER) decreases. A corresponding relationship between the change of ER and degree of oxidation is summarized by means of thermogravimetric analysis. The change of ER for the annealing sample with the degree of oxidation of 0.507% is 27.32%, which induced the polarization properties of aligned NiNWAs to be sensitive to the oxidation of Ni NWs. These findings can provide new positive features in the development of future polarization-based device applications for THz electronics and photonics.

Magnetic Properties of Ni Nanowires in Porous Anodic Alumina Matrix

Magnetic Properties of Ni Nanowires in Porous Anodic Alumina Matrix

Ni nanowires decorated with Pd nanoparticles as an efficient nanocatalytic system for Suzuki coupling of anisole derivatives

Suzuki-Miyaura reaction enables the formation of biaryl compounds containing diverse functional groups. This work reports the development of a nanocatalytic system, which enhances the coupling of anisole derivatives using this reaction framework. Composite nanocatalysts were prepared by decorating nickel nanowires (Ni NWs) made in-house with spherical palladium nanoparticles (Pd NPs). Sonochemical deposition of noble catalytic centers on metallic nanowires proved to be fast and effective under mild conditions. Precise control of the concentration of Pd NPs on the nanowire surface enabled studying the impact of the content of noble metal on the reaction course. The lowest evaluated load of Pd (0.34 %) exhibited the best catalytic performance. Moreover, it was noted that the application of microwaves considerably increased the catalytic activity of the system due to the formation of hot spots on Pd NPs. As a result, the reaction times were shortened substantially without negatively influencing the yields of the transformations. The proposed novel approach for nanocatalyst design should inspire further studies in modern organic chemistry, especially since the proposed catalytic system is highly efficient and entirely reusable.

In Situ Synthesis of Heterostructured Fe–Ni Nanowires with Tunable Electromagnetic Wave Absorption Capabilities

In Situ Synthesis of Heterostructured Fe–Ni Nanowires with Tunable Electromagnetic Wave Absorption Capabilities

Nanowires based solid-state asymmetric self-charging supercapacitor driven by PVA–ZnO–KOH flexible piezoelectric matrix

The development of an efficient mechanical to electric energy conversion system and its functional integration with an energy storage device for self-powered portable devices are advanced research fields. In the traditionalconfiguration, an additional energy harvesting device is connected with an energy storage device for developing a self-charging unit. As a result, large amount of energy is lost because of the external rectifiers. Moreover, this type of external circuit makes the system bulky and thus, limits the practical applications of such devices. In this work, nanoparticles of Zinc oxide (ZnO) are employed as a piezoelectric material, and are combined with an asymmetric device for developing a self-charging asymmetric piezo-supercapacitor. The developed asymmetric piezo-supercapacitor comprises of Ni and Mg-Co nanowires-based binder-free electrodes that were employed as the anode and cathode, respectively, as well as a ZnO-based separator as energy harvester along with KOH as electrolyte. The electrochemical results reveal tremendous cyclic stability with capacitive retention of 100% and 96.5% for Mg-Co and Ni nanowires array based electrodes even after 10,000 repeated GCD cycles, respectively. In addition, the device attained a maximum voltage of ∼99 mV as a result of the compressive force via thumb press. The proposed facile as well as cost-effective approach for smart self-chargeable power package supercapacitor provides new insights for developing next generation all-in-one energy harvesting and storage devices.

Effects of structure, size and non-magnetic Cu layer thickness on magnetization switching behavior in Ni/Cu/M (M [formula omitted] Ni, Co) cylindrical nanowires

We have investigated the dependence of the magnetization switching behavior on the structure, size and nonmagnetic Cu layer thickness (tCu) in Ni/Cu/M (M = Ni, Co) cylindrical nanowires fabricated by electrodeposition using porous polycarbonate templates. The crystal structure of the Ni nanowires was (111)- or (200)-oriented polycrystalline fcc, while that of Co nanowires was (100)- or (101)-oriented hcp and/or (111)-oriented polycrystalline fcc. When the wire diameter (d) was 50 nm, the squareness ratio (Mr/Ms) for M = Ni, as estimated from the magnetization curve, is almost constant at Mr/Ms∼0.79 (Mr/Ms∼0.64 for M = Co) when tCu increases from 0 to 500 nm. When d=100nm, Mr/Ms decreases by 41% from 0.71 to 0.42 with increasing tCu from 0 to 700 nm for M = Ni, while Mr/Ms decreases by 25% from 0.53 to 0.40 with varying tCu from 0 to 500 nm for M = Co. The threshold Cu layer thickness (tCuth) beyond which Mr/Ms becomes constant at d=100nm is ∼500 nm for M = Ni and ∼300 nm for M = Co. The results are qualitatively consistent with those obtained from our micromagnetic simulation and analysis. The observed difference in the tCuth dependence of Mr/Ms between M = Ni and Co is attributed to the change in the magnetic domain structure of the nanowires as it sensitively varies with the magnetocrystalline anisotropy. On the other hand, the coercive force of the nanowires shows a small tCu dependence for both d=50 and 100 nm. These results indicate that the layered structure in the nanowires governs the magnetic domain structure, though the effect on the magnetization switching behavior is indeed relatively small.

Amorphous co-modified catalyst based on interfacial coupling effect for efficient hydrogen production by water electrolysis

Development of synthesis procedures of efficient amorphous heteroatom coupling interfaces is important for the improvement of electrocatalyst performance. Herein, the Co/Ni NWs/NF composite electrode was prepared using magnetic effect, where Ni nanowires were initially grown on Ni foam to increase its specific surface area, followed by the electrodeposition of amorphous cobalt nanosheets to form multiple active sites for the hydrogen evolution reaction (HER). The electrochemical results show that the prepared Co/Ni NWs/NF can deliver a current density of 10 mA cm−2 at an overpotential of 49 mV in 1 M KOH electrolyte. The physical test results demonstrate that the introduction of cobalt species onto Ni nanowire result in the interface coupling effect, which can efficiently increase the HER active surface sites and modify the interface charge distribution. The study provides new approach for design and preparation of highly active hydrogen evolution catalysts for water electrolysis.

Highly open one-dimensional PtNi architectures with subnanometer walls as efficient catalysts for alcohol electrooxidation

The design of efficient and sustainable platinum-based catalysts is the key to developing direct alcohol fuel cells. Here, we designed highly open, one-dimensional Pt–Ni architectures with controllable wall thickness by selectively etching Pt–Ni nanowires. Pt atoms of both the inner and outer Pt–Ni architectures can participate in the electrochemical process, dramatically increasing the number of active sites and resulting in excellent alcohol electrooxidation performance. The obtained Pt1Ni5-M architecture with an ultrathin wall of 1.18 nm and a more open structure shows the best performance. The methanol oxidation reaction and ethanol oxidation reaction mass activities of Pt1Ni5-M are 7.4 (1.93 A/mgPt) and 4.6 (0.96 A/mgPt) times higher than that of Pt/C, respectively. After 3600s chronoamperometry tests, these Pt–Ni architectures also show improved durability with limited decay. This simple strategy inspires us to create more suitable catalysts with open structures for direct alcohol fuel cells.

IoT Electrochemical Sensor with Integrated Ni(OH)2–Ni Nanowires for Detecting Formaldehyde in Tap Water

Simple, low-cost methods for sensing volatile organic compounds that leave no trace and do not have a detrimental effect on the environment are able to protect communities from the impacts of contaminants in water supplies. This paper reports the development of a portable, autonomous, Internet of Things (IoT) electrochemical sensor for detecting formaldehyde in tap water. The sensor is assembled from electronics, i.e., a custom-designed sensor platform and developed HCHO detection system based on Ni(OH)2–Ni nanowires (NWs) and synthetic-paper-based, screen-printed electrodes (pSPEs). The sensor platform, consisting of the IoT technology, a Wi-Fi communication system, and a miniaturized potentiostat can be easily connected to the Ni(OH)2–Ni NWs and pSPEs via a three-terminal electrode. The custom-made sensor, which has a detection capability of 0.8 µM/24 ppb, was tested for an amperometric determination of the HCHO in deionized (DI) and tap-water-based alkaline electrolytes. This promising concept of an electrochemical IoT sensor that is easy to operate, rapid, and affordable (it is considerably cheaper than any lab-grade potentiostat) could lead to the straightforward detection of HCHO in tap water.

Exchange Bias Effect of Ni@(NiO,Ni(OH)2) Core/Shell Nanowires Synthesized by Electrochemical Deposition in Nanoporous Alumina Membranes.

Tuning and controlling the magnetic properties of nanomaterials is crucial to implement new and reliable technologies based on magnetic hyperthermia, spintronics, or sensors, among others. Despite variations in the alloy composition as well as the realization of several post material fabrication treatments, magnetic heterostructures as ferromagnetic/antiferromagnetic coupled layers have been widely used to modify or generate unidirectional magnetic anisotropies. In this work, a pure electrochemical approach has been used to fabricate core (FM)/shell (AFM) Ni@(NiO,Ni(OH)2) nanowire arrays, avoiding thermal oxidation procedures incompatible with integrative semiconductor technologies. Besides the morphology and compositional characterization of these core/shell nanowires, their peculiar magnetic properties have been studied by temperature dependent (isothermal) hysteresis loops, thermomagnetic curves and FORC analysis, revealing the existence of two different effects derived from Ni nanowires' surface oxidation over the magnetic performance of the array. First of all, a magnetic hardening of the nanowires along the parallel direction of the applied magnetic field with respect their long axis (easy magnetization axis) has been found. The increase in coercivity, as an effect of surface oxidation, has been observed to be around 17% (43%) at 300 K (50 K). On the other hand, an increasing exchange bias effect on decreasing temperature has been encountered when field cooling (3T) the oxidized Ni@(NiO,Ni(OH)2) nanowires below 100 K along their parallel lengths.

Energy competition and the contribution of Cu layer to the anisotropy field in Ni nanowires

Energy competition and the contribution of Cu layer to the anisotropy field in Ni nanowires