NiFe Nanoparticles Research Articles

Optimized microwave magnetic characteristics for patterned FeNi nanoparticle films manufactured by electric field-assisted deposition

The high-density FeNi nanoparticle films with strip structures were prepared by electric field-assisted deposition technique. The electric field of 10–40kV was applied on the sputtering platform during thin film deposition in order to obtain superior in-plane soft magnetic properties. The dependence of magnetic properties and microwave behavior on electric field was investigated. It is found that these high-density films have magnetically easy-modulated characteristics, especially for the strip-patterned ones. Application of electric field is very effective to obtain stronger in-plane magnetic anisotropy field and higher saturation magnetization simultaneously for our samples. In this case, large permeability and high ferromagnetic resonance frequency are easily achieved when the strip-patterned films are used in a wide gigahertz range. The experimental results indicate that electric field-assisted deposition technique is one of the important and promising manufacture methods to prepare thin film materials with enhanced gigahertz electromagnetic wave properties.

Supported Bimetallic NiFe Nanoparticles through Colloid Synthesis for Improved Dry Reforming Performance

The conversion of methane and carbon dioxide into a synthesis gas, the so-called dry reforming of methane (DRM), suffers from a stability issue caused by coke formation at the surface of the Ni-based catalysts. Using a colloidal approach, we demonstrate that supported 3–4 nm bimetallic NiFe nanoparticles with a Ni/Fe ratio of 3 have an enhanced stability compared to the corresponding pure Ni-based catalyst and a higher activity compared to conventional NiFe catalysts. The active sites for DRM are associated with Ni0, while FeO, observed by operando XAS under DRM conditions, allows for an effective decoking of the metal centers.

Covalent Porphyrin Framework-Derived Fe2P@Fe4N-Coupled Nanoparticles Embedded in N-Doped Carbons as Efficient Trifunctional Electrocatalysts.

A new porous covalent porphyrin framework (CPF) filled with triphenylphosphine was designed and synthesized using the rigid tetrakis(p-bromophenyl)porphyrin (TBPP) and 1,3,5-benzenetriboronic acid trivalent alcohol ester as building blocks. The carbonization of this special CPF has afforded coupled Fe2P and Fe4N nanoparticles embedded in N-doped carbons (Fe2P/Fe4N@N-doped carbons). This CPF serves as an "all in one" precursor of Fe, N, P, and C. The porous property and solid skeleton of the CPF endow Fe2P/Fe4N@N-doped carbons with porous structure and a high degree of graphitization. As a result, Fe2P/Fe4N@N-doped carbons exhibited highly efficient multifunctional electrocatalytic performance for water splitting and oxygen electroreduction. Typically, Fe2P/Fe4N@C-800, obtained at a heat-treatment temperature of 800 °C, showed an ORR half-wave potential of 0.80 V in alkaline media and 0.68 V in acidic media, close to that of commercial Pt/C catalysts. Fe2P/Fe4N@C-800 also displayed efficient OER and HER activities, comparable to other phosphide and nitride electrocatalysts. The coupled Fe4N and Fe2P nanoparticles embedded in carbons exert unique catalytic efficiency for water splitting and fuel cells.

Synthesis and application of surface-modified NiFe nanoparticles as a new magnetic nano adsorbent for the removal of nickel ions from aqueous solution.

Surface-modified magnetic Ni2.33Fe alloy nanoparticles were prepared using a hydrothermal method. Thermogravimetric analysis (TG) and Fourier transform infrared spectroscopy (FTIR) tests demonstrated that the surface was successfully modified by sodium citrate. The surface-modified particles can be used for removing nickel ions from aqueous solution. The adsorption kinetics studies were performed and the pseudo-second-order kinetic model successfully described the kinetic data. The diffusion model indicated the adsorption was regulated by both surface and intraparticle diffusion processes. The Freundlich and Langmuir adsorption models were adopted for the mathematical description of adsorption equilibrium, and it was found that the experimental data fitted very well to the Freundlich model.

Facile synthesis of bicontinuous Ni3Fe alloy for efficient electrocatalytic oxygen evolution reaction

Oxygen evolution reaction is a vital aspect of several energy generation technologies such as water splitting, metal air batteries. However, unreceptive thermodynamics and slothful kinetics of this process mandate the use of a noble metal catalyst. Substituting these noble metals by more abundant transition metals is vital for commercial application of these technologies. In this regard, we have developed a facile method for synthesis of Ni3Fe alloy with bicontinuous structure. The highly porous foam-like structure of the composite electrode offers numerous transportation channels for transfer of electrolyte and dissipation of the gaseous products. Moreover, the formation of a carbon layer during the synthesis of the composite improves the stability of the catalyst by preventing the agglomeration and dissolution of nanoparticles. Consequently, Ni3Fe nanoparticles with bicontinuous structure displayed enhanced catalytic activity for OER and required low overpotential only 248 mV to achieve a current density of 10 mA cm−2. Excellent activity and long-term durability of theses Ni3Fe nanoparticles make them an ideal substitute for the noble metal catalyst. We believe this work can provide an easy way for the synthesis of highly porous nanoparticles.

Martensitic transformation during coalescence of Fe–Ni nanoparticles. Atomistic simulation

Martensitic transformation during coalescence of two Fe–20 at.% Ni nanoparticles of size d ∼3–7 nm has been studied using molecular dynamics. Orientation relationship analysis showed that Kurdyumov–Sachs orientation relationship was observed between the initial γ-phase and the final α phase (at T=0 K) for all of the studied cases of misorientation. A significant change in the type of contact boundaries between the two nanoparticles was obtained after the completion of the martensitic transformation, which was caused by a change in the indices of the misorientation axis of the particles and in the number of symmetry elements for it.

Stabilities of Bimetallic Nanoparticles for Chirality-Selective Carbon Nanotube Growth and the Effect of Carbon Interstitials

Bimetallic nanoparticles play a crucial role in various applications. A better understanding of their properties would facilitate these applications and possibly even enable chirality-specific growth of carbon nanotubes (CNTs). We here examine the stabilities of NiFe, NiGa, and FeGa nanoparticles and the effect of carbon dissolved in NiFe nanoparticles through density functional theory (DFT) calculations and Born–Oppenheimer molecular dynamics (BOMD) simulations. We establish that nanoparticles with more Fe in the core and more Ga on the surface are more stable and compare these results with well-known properties such as surface energy and atom size. Furthermore, we find that the nanoparticles become more stable with increasing carbon content, both at 0 K and at 700 K. These results provide a basis for further research into the chirality-specific growth of CNTs.

Nitrogen–doped graphitized carbon shell encapsulated NiFe nanoparticles: A highly durable oxygen evolution catalyst

Oxygen evolution reaction (OER) plays a crucial role in various energy conversion devices such as water electrolyzers and metal–air batteries. Precious metal catalysts such as Ir, Ru and their oxides are usually used for enhancing reaction kinetics but are limited by their scarcity. The challenges associated with alternative non–precious metal catalysts such as transition metal oxides and (oxy)hydroxides are their low electronic conductivity and durability. The carbon encapsulating transition metal nanoparticles are expected to address these challenges. However, the relationship between precursor compositions and catalyst properties, and the intrinsic functions of each component has been rarely studied. Herein, we report a highly durable (no degradation after 20,000 cycles) and highly active (360mV overpotential at 10mAcm–2GEO) OER catalyst derived from bimetallic metal–organic frameworks (MOFs) precursors. This catalyst consists of NiFe nanoparticles encapsulated by nitrogen–doped graphitized carbon shells. The electron–donation/deviation from Fe and tuned lattice and electronic structures of metal cores by Ni are revealed to be primary contributors to the enhanced OER activity, whereas N concentration contributes negligibly. We further demonstrated that the structure and morphology of encapsulating carbon shells, which are the key factors influencing the durability, are facilely controlled by the chemical state of precursors.

Synthesis, structure and magnetic properties of Fe3N nanoparticles

Iron nitride (Fe3N) is a promising material with excellent magnetic properties, but the synthetic methods are difficult to operate in previous literatures. Here, we report a facile synthetic method using ferrous chloride tetrahydrate and ethanediamine as iron and nitrogen sources, followed by calcined at 540 °C for 1 h. The iron nitride with tunable morphology was obtained by changing the experimental conditions. More importantly, the magnetic performances have greatly been improved because of the tunable morphology. The coercivity can reach 408.84 Oe under the optimal conditions with superior retentivity and squareness, showing good ferromagnetic behaviors. This finding broadens our vision to realize the importance of morphology control and paves the way for other transition metal nitrides in obtaining tunable performances by controlling their morphologies.

Characterization of carbon-encapsulated permalloy nanoparticles prepared through detonation

Carbon-encapsulated Fe–Ni alloy nanoparticles were synthesized through detonation using two composite explosive precursors doped with Fe (NO3)3 · 9H2O and Ni(NO3)2 · 6H2O · The morphology, components, and magnetism of the synthesized carbon-encapsulated alloy nanoparticles were characterized through x-ray diffraction studies (XRD, Rigaku, D/Max 2400, Japan), Raman spectroscopy (Raman, Thermo Fisher, DXR Microscope, USA), Transmission electron microscopy (TEM, FEI, Technai F30, USA) attached with energy dispersive x-ray spectroscopy (EDS), and vibrating sample magnetometer (VSM, JDM-13, China) analyses. The denotation products of the two precursors were compared. The influence of the components of the two precursors on the products was also analyzed. Results showed that both precursors detonated and synthesized the carbon-encapsulated Fe–Ni nanoparticles with a core–shell structure. The grains exhibited sizes ranging from 10 nm to 100 nm and were uniformly distributed. The encapsulated metal core was mainly composed of different proportions of Fe and Ni. The outer shell was composed of graphite and amorphous carbon. VSM analysis indicated that the detonated composite nanoparticles showed superparamagnetism at room temperature.

Enhancement of in-plane uniaxial magnetic anisotropy for patterned nanoparticle films fabricated by electric field-assisted deposition

The patterned FeNi nanoparticle films with strip width 60µm were prepared by electric field-assisted deposition technique. Application of electric field drove the accelerating deposition of the condensed nanoparticles, promoting the formation of the films with high stacking density. Besides the excellent soft magnetic characteristics, the samples showed an obvious enhancement of in-plane uniaxial magnetic anisotropy when they were annealed in vacuum environment at proper temperatures. The increase of in-plane uniaxial magnetic anisotropy, which is due to the release of stress with increasing temperature, is also confirmed by scanning microwave permeability spectra in GHz range. The experimental results imply that optimization of in-plane uniaxial magnetic anisotropy is particularly attractive for the application of electric field deposited soft magnetic nanoparticle films in the high-temperature processing electromagnetic devices.

A versatile sensor for determination of seven species based on NiFe nanoparticles

A facile one-pot route was developed to synthesis NiFe bimetallic nanoparticles via a controlled co-reduction of Ni(II) acetylacetonate and Fe(II) acetylacetonate in oleylamine (OAm). Due to its unique properties originating from the synergistic effects of transition metals, NiFe exhibited excellent electrochemical catalytic activities. The electrochemical sensor based on carbon supported NiFe nanoparticles (NiFe/C) was constructed to determine various small biomolecules, and intensively showed high selectivity towards the oxidation of ascorbic acid (AA), dopamine (DA), uric acid (UA) and four DNA bases (guanine (G), adenine (A), thymine (T) and cytosine (C)), with large peak separations of 179mV (AA-DA), 123mV (DA-UA), 128mV (G-A), 274mV (A-T), 112mV (T-C) and little mutual interference. The detection limits were AA (1.0μM), DA (0.1μM), UA (0.1μM), G (0.25μM), A (0.25μM), T (10μM) and C (10μM) at S/N=3, respectively. The feasibility of the proposed sensor for real sample analysis was also investigated. These results demonstrate that NiFe bimetallic catalyst is a promising candidate of electrode material for determination of various analytes, which make it a fascinating sensor with versatile application.

Improvement of microwave permeability spectra in high stacking density FeNi nanoparticle films prepared by electric field-assisted deposition

We proposed an advanced method to improve saturation magnetization of soft magnetic nanoparticle films, which are of great concern for application in modern electromagnetic devices operated in the GHz range. Fe50Ni50 nanoparticle films with a particle size of about 6 nm were fabricated at room temperature by electric field-assisted deposition. An electric field of 10–20 kV was applied on the deposition platform during the film’s manufacture to obtain high stacking density and superior in-plane soft magnetic properties in the films. Based on the results of the microwave permeability spectra, it is found that the samples with higher saturation magnetization have excellent microwave response. These results indicate that magnetic softness and microwave behavior of FeNi nanoparticle films can be modulated by applying electric field during deposition.

Corrosion investigation of Co–Ni–Fe-coated mild steel electrodeposited at different current densities and deposition times

PurposeThe purpose of this study is to determine the effect of current density on the surface roughness and corrosion performance of electrodeposited Co–Ni–Fe-coated mild steel. Process variables are the key factor in controlling the electrodeposition process. It is important to study the processing parameter to optimize the mechanical and corrosion resistance performance of the coating substrate.Design/methodology/approachA low-cost electrodeposition method was used to the synthesize Co–Ni–Fe coating on the mild steel substrate. In the electrodeposition, electrochemistry concept was applied. The temperature of the process was controlled at 50 ± 5°C in an acidic environment. The influence of current density (11, 22 and 33 mA/cm2) and deposition time (15, 20 and 30 min) toward the surface roughness, hardness and corrosion rate was investigated.FindingsThe increases of time deposition and current density have improved the microhardness and corrosion resistance of Co–Ni–Fe-coated mild steel. The Co–Ni–Fe nanoparticles deposited at 30 min and current density of 33 mA/cm2 experienced the smallest surface roughness value (Ra). The same sample also obtained the highest Vickers microhardness of 122.6 HV and the lowest corrosion rate. This may be due to the homogenous and complete protection coating performed on the mild steel.Practical implicationsThe findings from the study are important for future application of Co–Ni–Fe on the mild steel parts such as fasteners, car body panels, metal chains, wire ropes, engine parts, bicycle rims, nails and screws and various outdoor uses. The improvement of corrosion resistance using optimum electrodeposition parameters is essential for these applications to prolong the life span of the parts.Originality/valueA new process which pertains to fabrication of Co–Ni–Fe as a protective coating on mild steel was proposed. The Co–Ni–Fe coating can enhance the corrosion protection and thus prolong the lifespan of the mild steel parts.

2D NiFe/CeO2 Basic-Site-Enhanced Catalyst via in-Situ Topotactic Reduction for Selectively Catalyzing the H2 Generation from N2H4·H2O.

An economical catalyst with excellent selectivity and high activity is eagerly desirable for H2 generation from the decomposition of N2H4·H2O. Here, a bifunctional two-dimensional NiFe/CeO2 nanocatalyst with NiFe nanoparticles (∼5 nm) uniformly anchored on CeO2 nanosheets supports has been successfully synthesized through a dynamic controlling coprecipitation process followed by in-situ topotactic reduction. Even without NaOH as catalyst promoter, as-designed Ni0.6Fe0.4/CeO2 nanocatalyst can show high activity for selectively catalyzing H2 generation (reaction rate (molN2H4 mol-1NiFe h-1): 5.73 h-1). As ceria is easily reducible from CeO2 to CeO2-x, the surface of CeO2 could supply an extremely large amount of Ce3+, and the high-density electrons of Ce3+ can work as Lewis base to facilitate the absorption of N2H4, which can weaken the N-H bond and promote NiFe active centers to break the N-H bond preferentially, resulting in the high catalytic selectivity (over 99%) and activity for the H2 generation from N2H4·H2O.

Compositional Optimization of Alloy FexNiy(OH)2 Nanoparticles for Alkaline Electrochemical Oxygen Evolution

Alloy FeNi nanoparticles were synthesized and evaluated as electrocatalysts for the oxygen evolution reaction in alkaline electrolyte. Electron microscopy imaging indicates nanoparticles were formed with a spherical morphology, and initial elemental analysis suggests significant oxygen content in the bimetallic particles. A molar ratio range from 5:1 to 1:5 Fe:Ni in the as-synthesized nanoparticles was tested. The effect of polyvinylpyrrolidone stabilizer on nanoparticle performance was also evaluated. Catalytic performance of the nanoparticles increased with decreasing Fe:Ni molar ratio and PVP:Ni molar ratio. Alloy nanoparticles synthesized with a Fe:Ni ratio of 1:5 and a PVP:Ni ratio of 0.001 resulted in an overpotential of 295 mV at 10 mA/cm2, a Tafel slope of 40 mV/dec, and a mass-based activity of 3343 mA/mg at 1.6 V vs. RHE.

Well dispersed Fe2N nanoparticles on surface of nitrogen-doped reduced graphite oxide for highly efficient electrochemical hydrogen evolution

Abstract

Facile and Scalable Synthesis of Robust Ni(OH)2 Nanoplate Arrays on NiAl Foil as Hierarchical Active Scaffold for Highly Efficient Overall Water Splitting.

Developing highly efficient low‐cost electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline electrolyte is essential to advance water electrolysis technology. Herein, Ni(OH)2 nanoplates aligned on NiAl foil (Ni(OH)2/NiAl) are developed by simply dealloying NiAl foil in KOH, which exhibits high electrocatalytic activity for OER with a small overpotential of 289 mV to achieve 10 mA cm−2 and outstanding durability with no detectable degradation during long‐term operation. Furthermore, such Ni(OH)2/NiAl can effectively act as an active and robust hierarchical scaffold to simply electrodeposit other catalysts with intrinsically higher activity such as NiMo and NiFe nanoparticles for highly efficient HER and OER, respectively. The prepared NiFe/Ni(OH)2/NiAl displays superior OER catalytic activity with overpotentials of 246, 315, and 374 mV at 10, 100, and 500 mA cm−2, respectively. While NiMo/Ni(OH)2/NiAl catalyst exhibits remarkable HER performance with a small overpotential of 78 mV to deliver 10 mA cm−2. Consequently, the electrolysis device composed of the above two electrocatalysts demonstrates superb water splitting performance with a cell voltage of 1.59 V at 10 mA cm−2. These results open up opportunities to explore and optimize low‐cost advanced catalysts for energy applications.

Synthesis and properties of magnetic multi-walled carbon nanotubes loaded with Fe4N nanoparticles

High saturation magnetization (>90emu/g) multi-walled carbon nanotubes (MWCNTs) and Fe4N nanoparticles composite were successfully synthesized by gas nitriding at 550°C. Almost all Fe4N nanoparticles were evenly distributed inside the carbon nanotubes and formed a special composite microstructure. This composite microstructure shows excellent soft magnetic property, structural stability, and chemical stability at room temperature. The investigations of electromagnetic and microwave absorption performances indicate that microwave absorbing capacity of low frequency band of MWCNTs were greatly improved by addition of Fe4N nanoparticles.

Fe–Ni Nanoparticles: A Multiscale First-Principles Study to Predict Geometry, Structure, and Catalytic Activity

Nanoparticles of iron and nickel are promising candidates as nanosized soft magnetic materials and as catalysts for carbon nanotube synthesis and CO methanation, among others. To understand geometry- and size-dependent properties of these nanoparticles, phase diagram of Fe/Ni alloy nanoparticles was calculated by density functional theory and cluster expansion method. Ground state convex is presented for face-centered cubic (FCC), body-centered cubic (BCC), and icosahedral (ICO) particles. Previous experimental observations were explained by using multiscale model for particles with realistic size (diameter ≥2 nm). At size 1.5 nm, geometry changes from BCC at low X(Ni) to icosahedral at high X(Ni). FCC is stabilized over icosahedral geometry by increasing number of atoms from 561 to 923. In large FCC particles, there is enrichment of Fe atoms from core to shell beneath surface, while surface and core are enriched by Ni atoms. Catalytic enhancement effect in CO methanation was found to be due to Ni incorpo...