Pulsed Electrochemical Deposition Research Articles

Preparation and investigation of Ni-W/CeO2 composite coating and its structure and anti-corrosion properties with different ceria content and deposition time

In the current work, CeO2 nanoparticles were embedded in Ni-W alloy matrix by pulse electrochemical deposition on copper substrate to optimize their microstructure and corrosion resistance. The effects of CeO2 concentration and deposition time on Ni-W/CeO2 composite coating were investigated for optimized structure and improved corrosion resistance. The composite coatings present nodular-like surfaces with dense and compact growth profiles, containing 63.03–67.88 wt% Ni, 28.73–31.87 wt% W and 0.25–8.24 wt% Ce. The content of incorporated CeO2 in coatings increased with the increase of CeO2 concentration in electrolyte. The addition of CeO2 particles has refined the grains of the prepared coating. The surface became rougher with the extension of electrodeposition time. Ni-W/CeO2 composite coating electrodeposited at 10 g L−1 CeO2 for 60 min possessed the highest corrosion resistance, indicating enhanced corrosion protection and long-term stability. This premium coating can be applied in harsh environments to prolong the lifespan of machinery, equipment, and parts in marine, vehicle, aerospace, and chemical industries.

Pulse electrodeposited Ni–C films and its performance

In this study, Ni–C films have been fabricated via pulse electrochemical deposition and carbon sol reinforcement methods. The surfacing of prepared films significantly improved due to the uniform distribution of nanoparticles. Additionally, the maximum thickness is attained when the concentration of carbon sol is 15[Formula: see text]ml/L. X-ray diffraction analysis of the Ni–C composite films reveals adding carbon sol effectively refines the grain size of prepared films. The highest film hardness, 420[Formula: see text]HV, is achieved at a carbon sol concentration of 15[Formula: see text]ml/L, corresponding to the best wear and corrosion resistance. Excessive carbon sol can lead to agglomeration of carbon particles, resulting in defects such as cracks and pores within the coating, thereby degrading its performance.

Novel High-Entropy FeCoNiMoZn-Layered Hydroxide as an Efficient Electrocatalyst for the Oxygen Evolution Reaction

The exploration of catalysts for the oxygen evolution reaction (OER) with high activity and acceptable price is essential for water splitting to hydrogen generation. High-entropy materials (HEMs) have aroused increasing interest in the field of electrocatalysis due to their unusual physicochemical properties. In this work, we reported a novel FeCoNiMoZn-OH high entropy hydroxide (HEH)/nickel foam (NF) synthesized by a facile pulsed electrochemical deposition method at room temperature. The FeCoNiMoZn-OH HEH displays a 3D porous nanosheet morphology and polycrystalline structure, which exhibits extraordinary OER activity in alkaline media, including much lower overpotential (248 mV at 10 mA cm−2) and Tafel slope (30 mV dec−1). Furthermore, FeCoNiMoZn-OH HEH demonstrates excellent OER catalytic stability. The enhanced catalytic performance of the FeCoNiMoZn-OH HEH primarily contributed to the porous morphology and the positive synergistic effect between Mo and Zn. This work provides a novel insight into the design of HEMs in catalytic application.

Pulsed electrodeposition of homogenous and heterogeneous solid solution layered structure in high strength nanocrystalline Co[sbnd]Cu alloys

A supersaturated solid solution nanostructure of an immiscible CoCu system is among the promising nanocrystalline (NC) alloys offering enhanced thermal and mechanical stability. In this paper, experiments were conducted to study the phase transformation and tailoring microstructure from a homogeneous/single-phase to a heterogeneous/dual-phase solid solution layered CoCu nanostructure via pulsed electrochemical deposition (PED). The increasing concentration of sodium dodecyl sulfate (SDS) in electrolyte played a crucial role in stabilizing a homogeneous solid solution CoCu nanostructure. On the other hand, the opposite approach led to the formation of heterogeneous solid solution CoCu alloys in the form of multilayered nanostructure consisting of the primary and secondary solid solution CoCu differing in 10–15 at.% Cu. The separation of primary and secondary phase is more prominent with the extended pulsed periods. The mechanical properties of selected single- and dual-phase alloys were investigated through micro-pillar compression, revealing that a combination of a high yield strength and an elevated strain hardening can be achieved in NC materials through a combined solid solution strengthening and hardening through nano-twin (NT).

Facile In-Situ Electrosynthesis of MnO2/RGO Nanocomposite for Enhancing the Electrochemical Performance of Symmetric Supercapacitors

One-pot galvanostatic reverse pulse electrochemical deposition (RPED) was used to create a supercapacitive electrode made of manganese dioxide/reduced graphene oxide (MnO2/RGO) nanocomposite. Systematic changes of two independent parameters of the reverse pulse current, including times of the anodic and cathodic pulses (ta and tc), were investigated to achieve the desired physicochemical and electrochemical properties. Galvanostatic charge–discharge, cyclic voltammetry, and electrochemical impedance spectroscopy tests were employed to perform electrochemical evaluations. According to the results, the MG50-5 nanocomposite, synthesized at ta = 50 ms, tc = 5 ms, and anodic peak current density of 2 mA cm−2, was selected as the optimal sample. This sample showed the highest specific surface area of 284.6 m2 g−1 and the specific capacitance of 789.0 F g−1 at a current density of 0.5 A g−1. The specific capacitances of the MG50-5 symmetric supercapacitor at current densities of 0.5 and 10 A g−1 were 660.14 and 402.50 F g−1, respectively. Maintaining 84.8 % of the specific capacitance after 5000 consecutive cycles at 4 A g−1 indicated stable cycle performance of the MG50-5 symmetric cell. The MG50-5 symmetric supercapacitor presented the maximum energy density of 22.92 Wh kg−1 at a power density of 156.3 W kg−1 and the maximum power density of 3.125 kW kg−1 at an energy density of 13.97 Wh kg−1. Therefore, optimizing reverse pulse current parameters in the galvanostatic RPED of MnO2/RGO nanocomposite leads to an outstanding electrochemical performance of the fabricated supercapacitors.

Features of the formation of nickel-containing nanoparticles on glassy carbon electrodes using electrodeposition from solutions of sodium pectate complexes

Problem statement. Currently, many leading companies in the field of electronics, radio engineering, and aerotechnics are concerned about the depletion of non-renewable resources such as platinum, gold, silver, indium and even the more common lithium, nickel and copper, which they actively use in their products. The design and synthesis of nanostructures with controlled morphology has attracted the attention of many researchers and engineers, since it is much more efficient to deposit a small amount of metal on the surface being used than to create a part entirely from this metal. There are several main methods for producing nanostructures on a surface: chemical deposition, electron beam lithography, pulsed laser deposition, electrochemical deposition and other methods. Electrochemical deposition is worth highlighting among all methods, because it makes it possible to obtain such surfaces relatively cheaply and on a large scale and control their morphology by changing deposition conditions, such as time, potential, solution pH, etc. Purpose of the study. Obtain nickel-containing nanoparticles on glassy carbon by electrodeposition from an aqueous solution of biopolymer complexes of sodium pectate with divalent nickel; to determine the influence of electrodeposition conditions, namely, the duration of deposition and the content of Ni(II) ions in sodium petectate complexes, on the morphology of the resulting surface. Results. Studies have been carried out of the influence of electrodeposition conditions on the morphology of the resulting glassy carbon electrode surface. It was found that biopolymer ligands act as a stabilizing agent for the formation of nickel-containing nanoparticles instead of a nickel-containing layer. The standard sizes of the resulting nanoparticles are in the range of 20 – 90 nm. The nickel content in the complexes, as well as the deposition time, proportionally affects the amount of deposited nanoparticles, but has little effect on their sizes. Practical significance. The results obtained make it possible to use them for controlled electrodeposition of nickel-containing nanoparticles on conducting surfaces in the development of nonlinear optical devices, LEDs, diodes, transistors, logic gates, sensors and other electronic devices.

Composition-Tunable Properties of Cu(Ag) Alloy for Hybrid Bonding Applications

In the present study, the properties of Cu(Ag) alloy films were studied to evaluate their potential use as an alternate material for interconnection in hybrid bonding. Thin alloy films of Cu(Ag) were deposited by pulsed electrochemical deposition (PED) using a sulfuric acid-based bath, rotating disk electrode, and hot entry. Secondary ion mass spectrometry (SIMS) was used to measure the silver content of the films, with us finding that it decreases with increasing duty cycle. Thereafter, bright field scanning transmission electron microscope (STEM) imaging in combination with energy-dispersive x-ray spectroscopy (EDS) was used to visualize the thin film microstructure and to confirm the uniform distribution of silver throughout the film, with no bands being seen despite the pulsed nature of the deposition. Film resistance was measured by a four-point probe to quantify the impact of Ag content on resistivity, with us finding the expected linear relationship with the Ag content in the film. Furthermore, the coefficient of thermal expansion (CTE) of the films was measured using X-ray diffraction, and modulus and hardness were measured via nanoindentation, revealing linear dependences on the Ag content as well. Notably, the addition of 1.25 atom% Ag resulted in a significant increase in the CTE from 17.9 to 19.3 ppm/K, Young’s modulus from 111 to 161 GPa, and film hardness from 1.70 to 3.99 GPa. These simple relationships offer a range of properties tunable via the duty cycle of the pulsed plating, making Cu(Ag) a promising candidate for engineering wafer-to-wafer metal interconnections.

Ag-Based Gas Diffusion Electrodes for the Electrochemical CO2 Reduction by Pulsed Hydrogen Bubble Templation

Energy-conversion technologies like the electrocatalytic nitrogen reduction reaction (N2RR), carbon monoxide reduction reaction (CORR) and in particular the electrochemical carbon dioxide reduction reaction (CO2RR) can contribute decisively to overcome the challenge of reducing greenhouse gas emissions. By reducing CO2 electrochemically, the carbon-cycle can be closed and industrially desired chemicals like syngas (CO + H2), formic and acetic acid, or hydrocarbons, such as methanol and ethylene, can be produced fossil-fuel free, depending on the catalyst material applied. Ag-based catalysts are very promising in the field of CO2RR, since they show high selectivities towards the reduction of CO2 to CO and current efficiencies of up to 100 %. In aqueous-fed systems, a significant drawback is the limited CO2 solubility, resulting in long diffusion pathways of CO2 within the bulk electrolyte 1, 2. Consequently, industrial conditions cannot be reached for CO2 electrolysis in aqueous solution in H-cell configurations due to the CO2 depletion within the porous electrodes that limit lab scale testing of CO2RR to current densities of approx. 35 mAcm-². One way to achieve commercially relevant current densities (> 200 mAcm-²) is the utilization of gas diffusion electrodes (GDEs) in flow cell configuration. These enable a decrease in CO2 diffusion lengths to approx. 50 nm, enhancing the mass transport to the catalyst 3.In our contribution, we will demonstrate a facile and fast production process of Ag-based GDEs by combining pulsed electrochemical deposition of the Ag catalyst with ionomer infiltration of the electrode. Using the dynamic hydrogen bubble templation method (DHBT), we utilized the parasitic hydrogen evolution reaction (HER) to aid in a solvent free structuring of the 3D catalyst network. In this work, we focused on the deposition parameters by varying different pulse-to-pause ratios in order to increase the amount of deposited catalyst and thus, successfully reduced the overpotential during CO2RR operation (Fig. 1, left). To inhibit electrode flooding and decrease CO2 mass transport limitations during CO2RR, we infiltrated the electrode with a perfluorinated ionomer. SEM and EDS analyses showed a uniform Ag/F distribution along the cross section of the electrodes (Fig. 1, right), which resulted in the conversion of CO2 to CO at industrially viable current densities.References S. Hernandez-Aldave and E. Andreoli, Catalysts, 10(6), 713 (2020).Z. Sun, T. Ma, H. Tao, Q. Fan and B. Han, Chem, 3(4), 560–587 (2017).T. Burdyny and W. A. Smith, Energy Environ. Sci., 12(5), 1442–1453 (2019). Figure 1

A judicious approach to induce large size growth of hydroxyapatite via applying graphene modified silicon nitride nanowires

Mimicking the structure of natural bone collagen fibers/hydroxyapatite (HA) to synthesize large size of HA for accelerated bone repair remains a challenge. Herein, silicon nitride nanowires (SN)-graphene (GE) was designed by the chemical vapor deposition, forming SN-GE (SG) similar to collagen fibers. Then, the large size HA was assembled onto SG by pulsed electrochemical deposition, the SG/HA (SGH) mimics the collagen fibers/HA structure of bone. The introduction of SG induces HA to large size grow in the form of coral-like. HA can be grown on a large size inextricably with the existence of GE modified layers. On the one hand, the upright GE sheets effectively increases the surface roughness which enhances the nucleation site of HA. On the other hand, the CO provides chemical bonding and induces HA nucleation. Compared with SN/HA(SH), the porosity of SGH decreased by 71%. The average diameter of the SGH is (9.76 ± 0.25) μm. Compared with SH, the diameter of SGH is 22 times larger than the diameter of SH. Indicating that SG induces large size growth of HA. Our work can provide a general strategy for the efficient preparation of biological scaffolds with large size HA that can be used in bone tissue engineering.

Fabrication of blue silver substrate with 10 nm grains by an electrochemical deposition and application in SERS

Nanosized-silver substrates with smooth surface and fine particles were fabricated by a non-cyanide pulse electrochemical deposition. The electrochemical behavior of silver electrochemical deposition was investigated with a series of electrochemical methods. Cyclic Voltammetry and chronopotentiometry showed that the overpotential was significantly reduced when silver ions were continuously deposited on the silver layer. During deposition, the nucleation mechanism gradually changed from the progressive nucleation to the instantaneous nucleation with the negative shift of potential. The effect of pulse period θ on the Surface Enhanced Raman Scattering performance of the substrate was investigated. Combined with Scanning Electron Microscope, X-ray diffraction, 2D SERS Mapping and Raman spectrum, the pulse period θ was optimized. The enhancement effect of the substrates was relatively uniform, and the enhancement factor for rhodamine 6G was 5.34 × 106, the detection limit could be as low as 1.0 × 10−13 mol·L−1. The optimized substrate obtained good linear range and low detection limit in the detection of contraband pigment sunset yellow, indicating that the substrate may have a good application prospect in the actual detection.

In Vitro Evaluation of Ag- and Sr-Doped Hydroxyapatite Coatings for Medical Applications.

Osseointegration plays the most important role in the success of an implant. One of the applications of hydroxyapatite (HAp) is as a coating for metallic implants due to its bioactive nature, which improves osteoconduction. The purpose of this research was to assess the in vitro behavior of HAp undoped and doped with Ag and/or Sr obtained by galvanostatic pulsed electrochemical deposition. The coatings were investigated in terms of chemical bonds, contact angle and surface free energy, electrochemical behavior, in vitro biomineralization in acellular media (SBF and PBS), and biocompatibility with preosteoblasts cells (MC3T3-E1 cell line). The obtained results highlighted the beneficial impact of Ag and/or Sr on the HAp. The FTIR spectra confirmed the presence of hydroxyapatite within all coatings, while in terms of wettability, the contact angle and surface free energy investigations showed that all surfaces were hydrophilic. The in vitro behavior of MC3T3-E1 indicated that the presence of Sr in the HAp coatings as a unique doping agent or in combination with Ag elicited improved cytocompatibility in terms of cell proliferation and osteogenic differentiation. Therefore, the composite HAp-based coatings showed promising potential for bone regeneration applications.

Novel Label-Free Nanocrystalline Gold Interdigitated Microelectrode Immunosensor for the Rapid and Ultrasensitive Detection of SARS-CoV-2.

Waves of COVID-19 outbreaks have dragged down the global economy and endangered human life. There is an urgent need for timeliness and sensitive SARS-CoV-2 detection techniques to complement the existing PCR assay. Herein, the controllable growth of gold crystalline grains was achieved by applying the reverse current during pulse electrochemical deposition (PED) interval. The proposed method validates the effects of pulse reverse current (PRC) on the atomic arrangement, crystal structures, orientations, and film characteristics in Au PED. The gap between the gold grains on the surface of the nanocrystalline gold interdigitated microelectrodes (NG-IDME) fabricated by the PED+PRC process matches the size of the antiviral antibody. Immunosensors are prepared by binding a large number of antiviral antibodies on the surface of NG-IDME. The NG-IDME immunosensor has a high specific capture ability for SARS-CoV-2 nucleocapsid protein (SARS-CoV-2/N-Pro) and completes ultrasensitive and quantification of SARS-CoV-2/N-Pro in humans and pets within 5 min (the LOQ as low as 75 fg/mL). The specificity, accuracy, stability, and actual blind sample tests show that the NG-IDME immunosensor is suitable for the detection of SARS-CoV-2 in humans and animals. This approach assists in monitoring the transmission of SARS-CoV-2-infected animals to humans.

Quaternary ammonium salt functionalized HA as an antibacterial and osteogenic coating for bone implants

The construction of hydroxyapatite (HA) antibacterial coating on titanium surface is one of the current research hot topics. Natural antimicrobial agents can promote bone production while sterilizing. In this paper, Polypyrrole (PPy) is driven in situ by pulsed electrochemical deposition. Under the oxidation potential, the amino group of Pyrrole (Py) monomer interacts with PO43− and Dexamethasone root ion(Dex−) in the electrolyte through electrostatic interaction. The phenolic hydroxyl group chitosan quaternary ammonium salt (2-hydroxypropyltrimethyl ammonium chloride chitosan, HTCC) interacts with N atom of the amino group on Py and forms hydrogen bonds to assist Py in regulating Dexamethasone (Dex) the drug. While under the reduction potential, OH− is produced near the working electrode to promote the generation of HA, and finally forms the PPy@HA/Dex/HTCC composite coating. The study show that the composite coating is spherical nanoparticles with uniform distribution, and the regulation effect of PPy reduces the release rate of Ca2+ and Dex− from the coating, making it release smoothly and slowly. The antibacterial ratio of the composite coating against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) reaches 100%, the osteoblasts and vascular endothelial cells proliferate well on the surface of the composite coating in vitro. Besides, the composite coating can induce the growth of apatite, proving that it has good bioactivity.

High-Entropy Alloy Films

High-entropy alloy films have the same excellent properties as high-entropy alloys and can better realize the practical applications of high-entropy alloys. This paper takes the high-entropy alloy films as the object of discussion. The preparation process, microstructure, hardness, wear resistance and corrosion resistance of high-entropy alloy films are mainly discussed and the influence of nitridation, sputtering power, substrate temperature, substrate bias and other factors on the phase structure of alloy films is analyzed. High-entropy alloy films can be prepared using magnetron sputtering, laser cladding, pulsed laser deposition, detonation spraying, electrochemical deposition and other processes. High-entropy alloy films tend to form a solid solution and amorphous state, and their hardness is far higher than that of traditional films. Among them, the hardness of high-entropy alloy nitride films can reach the standard of superhard films. Wear resistance is usually proportional to hardness. Due to the corrosion-resistant elements and amorphous structure, some high-entropy alloy films have better corrosion resistance than stainless steel. High-entropy alloy films have shown profound development prospects in the fields of wear-resistant coatings for tools, corrosion protection, diffusion barrier and photothermal conversion coatings.

Interfacial Design and Construction of Carbon Fiber Composites by Strongly Bound Hydroxyapatite Nanobelt-Carbon Nanotubes for Biological Applications.

Carbon fiber composites are promising candidates for orthopedic implant applications, which calls for a combination of high mechanical strength and outstanding biotribological properties. In this work, hydroxyapatite nanobelts-carbon nanotubes (HN) were designed and constructed into carbon fiber-anhydrous dicalcium phosphate (DCPA)-epoxy composites (CDE) for simultaneously optimizing the mechanical and biotribological properties via the combined methods of pulse electrochemical deposition and injected chemical vapor deposition. HN provides more nucleation sites for the growth of DCPA and favors the infiltration of epoxy. In addition, HN optimizes the fiber/matrix interface by generating strong interfacial mechanical interlocking. Owing to the synergism of a strongly bound HN, the mechanical and biotribological properties of CDE have demonstrated significant improvement. The tensile strength and elastic modulus of HN-modified CDE (HN-CDE) increase by 52 and 170% compared with CDE, respectively. The wear rate and average friction coefficient of HN-CDE are decreased by 42% and increased by 45% compared with those of CDE, respectively. HN-CDE, with superior mechanical strength and biotribological properties, has high potential as a bone substitute and orthopedic implant.

Compositionally modulated multilayer Cu-Zn alloy coatings fabricated using eco-friendly non-cyanide pulse electrochemical deposition

Pulse electrodeposition of Cu-Zn compositional modulated multilayer alloy (CMA) coatings was carried out onto AISI 304 stainless steel substrate using an environmentally friendly alkaline non-cyanide electrolytic bath. Cu-Zn alloy multilayer coating was co-electrodeposited using a trapezoidal pulse current. Multilayer coatings can have two different metals in layers or two-phase mixtures. Different sets of multilayers of 10, 20, 50, and 100 were done using a trapezoidal pulse current. In the trapezoidal pulse current module, during the higher current stage (0.1 A) Zn was deposited as compared to the lower current module (0.02 A) where Cu was deposited. Microstructural and structural analysis of the coatings confirmed nanocrystalline morphology with peaks corresponding to crystallographic planes of (002), (111), (020), and (022). Deposited coatings are hydrophilic in nature. The microhardness of the coatings is decreased with an increase in the number of layers deposited.

Generating bioactive and antiseptic interfaces with nano-silver hydroxyapatite-based coatings by pulsed electrochemical deposition for long-term efficient cervical soft tissue sealing.

Infections related to osseointegrated implants have sparked the interest in studying titanium modification for long-term effective soft tissue sealing. Constructing a silver (Ag)-hydroxyapatite (HA) coating is regarded as an effective strategy for integrating antibiosis with osteanagenesis; however, the outcome for long-term cervical soft tissue sealing in vivo is compromised. It is challenging to construct an Ag-HA coating for long-term efficient soft tissue integration that instills a maximum antibacterial effect while retaining favorable bioactivity to normal gingival mesenchymal cells in vivo. In this study, we employed gradient concentrations of Ag/CaP by pulsed electrochemical deposition to fabricate optimal Ag-HA nanocoatings. By physicochemical analyses, these uniform coatings were mainly formed with spherical metallic and hydroxyapatite nanoparticles, which facilitated good hydrophilicity, moderate rough surfaces and corrosion protection. Furthermore, the nanocoating of the 1.5Ag/CaP group exhibited superior performances in dental follicle cells' proliferation, osteogenic differentiation and antibacterial properties mainly through direct contact inhibition and partially through sustained silver ion release, which resulted in functional cervical soft tissue sealing in beagles lasting for one year. Our investigations provide a feasible strategy to balance the long-term antibacterial demand and bioactive induction around osseointegrated implants for long-term efficient cervical soft tissue sealing.

Strontium doped electrospinning fiber membrane with antibacterial and osteogenic properties prepared by pulse electrochemical method

• Composite fibers were prepared by electrostatic spinning and pulse electrochemical deposition. • PPy controls the slow release of Sr 2+ and Cu 2+ for a long time. • Good physiological stability and long-term antibacterial effect. • Fiber has good osteogenic and angiogenic properties. The osteogenic differentiation and new bone formation are commonly delayed by bacterial infection of orthopedic implants, which is urgent to be resolved quickly in the clinic. The current paper prepared a strontium-doped electrospinning fiber membrane with antibacterial and osteogenic properties by pulse electrochemical method. Polylactic acid/hydroxyapatite (PLLA/HA) composite fiber substrate was fabricated by electrospinning technology, and strontium doped SrHA/Cu/Polypyrrole (PPy) composite coating was constructed with pulse electrodeposition method on its surface. The strontium doping technique, degradation of Sr 2+ and Cu 2+ , cellular compatibility, and the antibacterial activity of the fiber membrane were examined. The results revealed that the deposition of phosphorus and calcium on composite fiber was the highest, indicating good biological activity. The release of Sr 2+ and Cu 2+ was stable and gradual due to the modulation of PPy. The composite fiber presented excellent antibacterial performance and the antibacterial rate was close to 100% against Staphylococcus aureus and Escherichia coli. Furthermore, it is conducive to the adhesion, spread, and proliferation of vascular endothelial cells and osteoblasts, namely outstanding osteogenesis and angiogenesis abilities. In conclusion, the multifunctional PLLA/HA@SrHA/Cu/PPy composite fiber membrane with good antibacterial and osteogenic activity by electrospinning technology and pulsed electrochemical deposition method provides an effective strategy for the poor bone healing of infected bone defects. Strontium doped antibacterial osteogenic PLLA/HA@SrHA/Cu/PPy composite fiber was constructed by electrostatic spinning and pulsed electrochemical deposition technology, which showed good antibacterial properties and had the ability to promote bone induction and angiogenesis.

Current density-induced emergence of soft and hard magnetic phases in Fe nanowire arrays

The capability of generating magnetically soft and hard phases in a material is important in many aspects, ranging from basic science to applications. Here, the emergence of soft and hard magnetic phases is reported in Fe nanowire (NW) arrays with a diameter of 35 nm fabricated by using a pulsed electrochemical deposition method in porous aluminum oxide templates under different current density (C d ) values in the range of 25–100 mA cm−2. The variation of C d influences the grain size, crystallinity, electrodeposition efficiency and length of the Fe NWs, as characterized by x-ray diffraction, high-resolution transmission electron microscopy, vibrating sample magnetometry and field-emission scanning electron microscopy. Increasing C d from 25 to 80 mA cm−2 results in a significant decrease in coercivity and squareness from 1590 to 900 Oe and 0.9 to 0.5, respectively, inducing the soft and hard phases along the length of Fe NWs. Further increasing the C d leads to the separation of the phases, as evidenced by first-order reversal curve analysis. From a theoretical aspect, the emergence of the soft phase may lead to the occurrence of the fanning reversal mode in the NWs, for which there is no precedent in previous experimental investigations.

Magnetization reversal properties and magnetostatic interactions of disk to rod-shaped FeNi layers separated by ultra-thin Cu layers

From fast magnetic memories with low-power consumption to recording media with high densities, realizing the magnetization reversal and interaction of magnetic layers would allow for manipulating the ultimate properties. Here, we use a pulsed electrochemical deposition technique in porous alumina templates (50 nm in pore diameter) to fabricate arrays of nanowires, consisting of FeNi layers (26−227 nm in thickness) with disk to rod-shaped morphologies separated by ultra-thin (3 nm) Cu layers. By acquiring hysteresis curves and first-order reversal curves (FORCs) of the multilayer nanowire arrays, we comprehensively investigate magnetization reversal properties and magnetostatic interactions of the layers at different field angles (0° ≤ θ ≤ 90°). These involve the extraction of several parameters, including hysteresis curve coercivity (H c Hyst ), FORC coercivity (H c FORC ), interaction field distribution width (ΔH u ), and irreversible fraction of magnetization (IF m ) as a function of θ. We find relatively constant and continuously decreasing trends of H c Hyst when 0° ≤ θ ≤ 45°, and 45° < θ ≤ 90°, respectively. Meanwhile, angular dependence of H c FORC and IF m shows continuously increasing and decreasing trends, irrespective of the FeNi layer morphology. Our FORC results indicate the magnetization reversal properties of the FeNi/Cu nanowires are accompanied with vortex domain wall and single vortex modes, especially at high field angles. The rod-shaped layers also induce maximum ΔH u during the reversal process, owing to enhancements in both magnetizing and demagnetizing-type magnetostatic interactions.