Search Results (128)

This study investigates the effects of molybdenum (Mo) additions on the crystallization behavior and soft magnetic properties and of Fe_82-xSi₄B₁₂Nb₁Mo_xCu₁ (x = 0–2) nanocrystalline alloys. Molybdenum enhances glass-forming ability (GFA) and magnetic properties by increasing negative mixing enthalpy ($∆{\mathrm{H}}_{\mathrm{m}\mathrm{i}\mathrm{x}}$), mixing entropy ($∆{\mathrm{S}}_{\mathrm{m}\mathrm{i}\mathrm{x}}$), and atomic size mismatch ($\delta$), which stabilize the amorphous phase. X-ray diffraction (XRD) analysis shows that Mo addition improves amorphous phase stability, further enhancing GFA. The simultaneous addition of Mo and Nb increases mixing entropy, promotes nucleation rates, and creates favorable conditions for optimizing nanocrystallization. Upon annealing, this optimized microstructure demonstrated low coercivity and high permeability. Notably, the Fe₈₀Si₄B₁₂Nb₁Mo₂Cu₁ ribbon, annealed at 470 °C for 10 min, exhibited exceptional soft magnetic properties, with a coercivity of 4.54 A/m, a maximum relative permeability of 48,410, and a saturation magnetization of 175.24 emu/g. High-resolution transmission electron microscopy (TEM) revealed an average crystal size of 18.16 nm. These findings suggest that Fe_82-xSi₄B₁₂Nb₁Mo_xCu₁ (x = 0–2) nanocrystalline alloys are suitable for advanced electromagnetic applications pursuing miniaturization and high efficiency. Full article

High-Cu-content (Cu-content > 1.3 at.%) nanocrystalline alloys exhibit wide heat-treatment windows and favorable soft magnetic properties due to the presence of pre-existing α-Fe nanocrystals. By fabricating ribbons with varying thicknesses to tailor cooling rates, distinct structural characteristics were achieved in Fe₈₂B_16.5Cu_1.5 alloy ribbons. Notably, the face-centered cubic (fcc) γ-Fe phase was identified in Fe-based nanocrystalline alloys. The precipitation of the fcc γ-Fe phase originates from a phase-selection mechanism under specific cooling conditions, while its retention in the as-quenched ribbon with a thickness of 27 μm is attributed to kinetic suppression during rapid cooling and the nanoscale stabilization effect. The formation of the fcc γ-Fe phase significantly reduced the saturation flux density (B_s) and increased coercivity (H_c), concurrently destabilizing the residual amorphous matrix. By suppressing the precipitation of the γ-Fe and Fe₃B phases through precise control of ribbon thickness and annealing parameters, the alloy ribbon with a thickness of 16 μm achieved an optimal combination of B_s (1.82 T) and H_c (8.3 A/m). These findings on anomalous fcc γ-Fe phase precipitation provide novel insights into metastable phase engineering and offer structural design guidelines for alloys containing pre-existing α-Fe nanocrystals. Full article

The ongoing electrification process also requires improvements in the efficiency of power transmission devices, such as transformers, the main part of which is the magnetic core. Despite great progress in the development of core material, losses and audible noise during their operation is still a critical issue to be solved. Currently, a magnetic material used to produce the transformer core is amorphous steel, which is gaining popularity. Compared to traditionally used grain-oriented silicon electrical steel, a significantly larger number of very thin amorphous ribbons is needed to produce the core, which is due to the fact that they are about an order of magnitude thinner, making mechanical stability a challenge. The presented article describes the preparation of a hybrid binder for amorphous steel based on the two types of silanes, tetraethyl orthosilicate and 1,2-bis(triethoxysilyl)ethane, for which their anticorrosive character and good dielectric properties were confirmed. Using the obtained binders, model toroidal cores were produced and their magnetic and acoustic properties were tested. The obtained results indicate that the applied silane-based hybrid binders improved important functional properties by reducing the magnetic no-load losses and audible noise. Full article

The interplay between melting viscosity, amorphous forming ability (AFA), nanocrystalline structure, and soft magnetic properties (SMPs) in Fe-based multicomponent alloys remains unclear. This study systematically explores the effects of Sn doping on the viscosity, precursor structure, and nanocrystallization behavior of Fe-Si-B-Nb-Cu-Al-P alloys. Sn doping reduces melting viscosity and induces an abnormal viscosity rise during cooling, lowering the fragility parameter ratio (F) between high- and low-temperature zones, thereby enhancing the AFA of the precursor ribbons. High-temperature heat preservation treatment (HTP) of the melt further reduces the F, improves precursor disorder, and refines nanocrystals, leading to reduced average magnetocrystalline anisotropy and optimized SMPs. The HTP-treated Sn-dopped alloy shows superior SMPs, including low coercivity of 0.4 A/m and high permeability of 32,400 at 5 kHz, making it highly promising for advanced electromagnetic device applications. This work reveals the relationship between viscosity, precursor structure, nanocrystalline structure, and SMPs of Fe-based alloys, which provides an approach for the optimization of SMPs. Full article

In this paper, the structure characteristics and magnetic properties of Fe₈₃Si₆B₆P_1.5C_1.5Cu₁Nb₁ amorphous alloy ribbons annealed at 550 °C for different times were systematically investigated using X-ray diffraction, vibrating sample magnetometer, and atom probe chromatography. The results show that high-density Cu atomic clusters of appropriate sizes help to stabilize the α-Fe(Si) phase and improve the uniformity of the grains to enhance the soft magnetic properties. The solubility difference between the α-Fe(Si) phase and the B-rich phase, the formation of a localized amorphous structure in the transition region, and the inhibition of nanograin growth. However, when the annealing time is extended, the size of the α-Fe(Si) grains decreases, the grain boundary density increases and secondary phases such as Cu clusters become pinning sites for magnetic domain walls. This leads to a decrease in soft magnetic properties, an increase in hard magnetic properties, and a rapid increase in coercivity. When annealed at 550 °C for 20 min, the number density of Cu atomic clusters was 9.18 × 10²² m⁻³, the spherical equivalent radius was 1.13 ± 0.29 nm, and the ribbons had good soft magnetic properties with a coercivity of 4.59 Oe. The saturation magnetic induction reached a peak value of 185.11 emu/g. Full article

The magnetoelastic effect is known as the dependence between the magnetic properties of the material and applied mechanical stress. The stress might not be applied directly but rather generated by the applied torque. This creates the possibility of developing a torque-sensing device based on the magnetoelastic effect. In this paper, the concept of an axially twisted toroidal magnetic core as a torque-sensing element is considered. Most known works in this field consider the utilization of an amorphous ribbon as the core material. However, Ni-Zn ferrites, exhibiting relatively high magnetostriction, also seem to be promising materials for magnetoelastic torque sensors. This paper introduces a theoretical description of the magnetoelastic effect under torque operation on the basis of total free energy analysis. The methodology of torque application to the toroidal core, utilized previously for coiled cores of amorphous ribbons, was successfully adapted for the bulk ferrite core. For the first time, the influence of torque on the magnetic properties of Ni-Zn ferrite was investigated in a wide range of magnetizing fields. The obtained magnetoelastic characteristics allowed the specification of the magnetoelastic torque sensitivity of the material and the determination of the optimal amplitude of the magnetizing field to maximize this parameter. High sensitivity, in comparison with previously studied amorphous alloys, and monotonic magnetoelastic characteristics indicate that the investigated Ni-Zn ferrite can be utilized in magnetoelastic torque sensors. As such, it can be used in torque-sensing applications required in mechanical engineering or civil engineering, like the evaluation of structural elements exposed to torsion. Full article

Microcantilevers (MCs) are highly sensitive sensors capable of detecting mass changes on the surface at the nanogram and even picogram scale. In this study, microcantilevers were fabricated for the first time using the Sodick AP250L Wire electrical discharge machining (EDM) from amorphous 2826MB (Fe₄₀Ni₃₈Mo₄B₁₈) ferromagnetic ribbons. This method is advantageous because it allows for the simultaneous production of a large number of microcantilevers, with about 100 MCs being produced in a single manufacturing process. Additionally, a straightforward and cost-effective measurement system was developed to measure the resonance frequency and frequency shift of the MC entirely through magnetic means, a technique not previously reported in the literature. To evaluate the performance of the MC, we employed it as a humidity sensor. For the TiO₂-NT-coated MC, a frequency shift of approximately 202 Hz was observed when the humidity level changed from 5% to 95% relative humidity (RH). Full article

This study aims to enhance the amorphous formation ability and magnetic properties that are crucial for the production of high-quality nanocrystalline alloys. The structural, thermal, and magnetic characteristics of the alloy ribbons were analyzed through a systematic adjustment of Nb content, and, including Nb, significantly improved the amorphous formation ability and thermal stability of the alloy, which is vital for nanocrystalline production. By varying the Nb content within Fe_85-xSi₂B₈P₄Cu₁Nb_x (x = 0.0, 0.5, 1.0, and 1.5), we explored finer adjustments to achieve homogeneous amorphousness during the melt spinning process. Careful control over the Nb content facilitated the production of amorphous ribbons with consistent homogeneity, which was critical for the subsequent fabrication of nanocrystalline structures through heat treatment. As a result, the amorphous ribbon of Fe_85.5Si₂B₈P₄Cu₁Nb_0.5 showed a low coercivity of 7 A/m. The heat treatment showed a remarkably high saturation magnetic flux density of 1.94 T. Additionally, the grain size (D) decreased as the Nb content increased, with D values ranging from 25.09 nm to 24.29 nm, as calculated by the Scherrer formula. Mössbauer spectroscopy confirmed the formation of nanocrystalline and residual amorphous phases. The hyperfine magnetic field values (B_eff) decreased from 25.7 T to 24.7 T in the amorphous samples and reached 33.0 T in the nanocrystalline phases. This study highlights Nb’s positive impact on thermal stability and amorphous formation capacity in Fe-Si-B-P-Cu alloys, culminating in the successful fabrication of nanocrystalline ribbons with superior structural and magnetic properties. Full article

The nanoporous copper (NPC)-copper oxides (Cu₂O/CuO)/reduced graphene oxide (rGO) composite structure was synthesized by combining the dealloying process of Cu₄₈Zr₄₇Al₅ amorphous ribbons with a microwave-assisted hydrothermal technique at a temperature of 200 °C. The main advantage of the microwave-assisted hydrothermal process is the oxidation of nanoporous copper together with the in situ reduction of graphene oxide to form rGO. The integration of rGO with NPC improves electrical conductivity and streamlines the process of electron transfer. This composite exhibit considerable potential in electrochemical catalysis application, due to the combined catalytic activity of NPC and the chemical reactivity of rGO. Our study relates the transition to n-type rGO in microwave-assisted hydrothermal reactions, and also the development of an electrode material suitable for electrochemical applications based on the p-p-n junction NPC-Cu₂O/CuO/rGO heterostructure. To confirm the formation of the composite structure, structural, morphological, and optical techniques as XRD, SEM/EDX, UV-Vis and Raman spectroscopy were used. The composite’s electrochemical properties were measured by EIS and Mott-Schottky analyses, showing a charge transfer resistance (Rp) of 250 Ω and indicating the type of the semiconductor properties. The calculated carrier densities of 4.2 × 10¹⁸ cm⁻³ confirms n-type semiconductor characteristic for rGO, and 7.22 × 10¹⁸ cm⁻³ for Cu₂O/CuO indicating p-type characteristic. Full article

A novel amorphous Fe₈₈Pr₆Ce₄B₂ ribbon with better magnetocaloric properties near 285 K is reported in the present work. The Fe₈₈Pr₆Ce₄B₂ ribbon exhibits a typical second-order ferromagnetic–paramagnetic transition near its Curie temperature (T_c, ~284 K), with a maximum magnetic entropy change (−ΔS_m^peak) of ~4.15 J/(kg × K) under 5 T and a maximum adiabatic temperature rise (ΔT_ad) of ~2.57 K under 5 T, both of which are almost the largest amongst the iron-based metallic glasses with T_c = 285 ± 10 K. The high −ΔS_m^peak enables several amorphous hybrids with table-like −ΔS_m–T curves to be synthesized by appropriately proportioning the Fe₈₈Pr₆Ce₄B₂ ribbon and other amorphous ribbons with different T_c. The larger average −ΔS_m and effective refrigeration capacity, as well as the appropriate temperature range, make the two amorphous hybrids potential candidates for use as refrigerants in household magnetic air conditioners. Full article

Magnesium alloys are considered as promising materials for use as biodegradable implants due to their biocompatibility and similarity to human bone properties. However, their high corrosion rate in bodily fluids limits their use. To address this issue, amorphization can be used to inhibit microgalvanic corrosion and increase corrosion resistance. The Mg-Zn-Ga metallic glass system was investigated in this study, which shows potential for improving the corrosion resistance of magnesium alloys for biodegradable implants. According to clinical tests, it has been demonstrated that Ga ions are effective in the regeneration of bone tissue. The microstructure, phase composition, and phase transition temperatures of sixteen Mg-Zn-Ga alloys were analyzed. In addition, a liquidus projection of the Mg-Zn-Ga system was constructed and validated through the thermodynamic calculations based on the CALPHAD-type database. Furthermore, amorphous ribbons were prepared by rapid solidification of the melt for prospective alloys. XRD and DSC analysis indicate that the alloys with the most potential possess an amorphous structure. The ribbons exhibit an ultimate tensile strength of up to 524 MPa and a low corrosion rate of 0.1–0.3 mm/year in Hanks’ solution. Therefore, it appears that Mg-Zn-Ga metallic glass alloys could be suitable for biodegradable applications. Full article

The structure and physicochemical properties of polyvinyl alcohol (PVA) and PVA/glycerol films have been investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetry/differential thermal analysis (TG/DTA), and advanced scanning probe microscopy (SPM). In the pure PVA films, SPM allowed us to observe ribbon-shaped domains with a different frictional and elastic contrast, which apparently originated from a correlated growth or assembly of PVA crystalline nuclei located within individual PVA clusters. The incorporation of 22% w/w glycerol led to modification in shape of those domains from ribbon-like in pure PVA to rounded in PVA/glycerol 22% w/w films; changes in the relative intensities of the XRD peaks and a decrease in the amorphous halo in the XRD pattern were also detected, while the DTA peak corresponding to the melting point remained at almost the same temperature. For higher glycerol content, FT-IR revealed additional glycerol-characteristic peaks presumably related to the formation of glycerol aggregates, and XRD, FT-IR, and DTA all indicated a reduction in crystallinity. For more than 36% w/w glycerol, the plasticization of the films complicated the acquisition of SPM images without tip-induced surface modification. Our study contributes to the understanding of crystallinity in PVA and how it is altered by a plasticizer such as glycerol. Full article

As an efficient advanced oxidation process, the Fenton-like reaction provides a promising way toward the degradation of organic pollutants; thus, the development of a highly efficient heterogeneous catalyst is of great significance. Herein, the chemical etching behavior of Fe-Si-B metallic glass (MG) ribbons in a dilute HF solution is studied by varying the etching time. Based on this, the uniform nanoporous (NP) structures are successfully fabricated. The Fe-Si-B MG ribbons after etching for 30, 60, and 90 min still maintain an amorphous structure and possess much larger specific surface areas than untreated Fe-Si-B ribbons. The thicknesses of their nanoporous structures, with a pore size range of tens to hundreds of nanometers, are about 92.0, 180.5, and 223.4 nm, respectively. The formation of the nanoporous structure probably follows the pitting corrosion mechanism, mainly referring to the generation of corrosion pits due to the selective leaching of Si and B and pore growth and integration owing to the selective corrosion of Fe. The Fenton-like system of NPFe/H₂O₂ exhibits enhanced degradation performance toward methyl orange (MO), primarily due to the high intrinsic catalytic activity of the amorphous structure and the large specific surface areas of nanoporous structures, indicating the great potential application of NPFe in wastewater treatments. The mechanism analysis shows that MO degradation mainly contains two sub-processes: the heterogeneous reaction on the catalyst surface and the homogeneous reaction in MO solution, which exhibit a strong synergistic effect with excellent degradation performance. Full article

The constantly evolving electrification also entails an increase in requirements for the effective and efficient distribution of electricity with the lowest possible power losses. Such needs can be met by highly effective electrical devices, and one of them is a transformer whose main component is a magnetic core. Currently, one of the soft magnetic materials used alternatively for the production of transformer cores are amorphous metal strips with competitive losses. However, to successfully use these materials, a key problem must be solved: limited mechanical stability. The presented article describes the development and application of a polyimide-based binder for efficient bonding of an amorphous metal ribbon. The layered binder was characterized using confocal microscopy, scanning electron microscopy and Raman spectroscopy, and its anticorrosion and mechanical properties were examined. As a final step, a prototype of a toroidal magnetic core bonded with the binder was manufactured and subjected to the evaluation of no-load loss and the analysis of the emitted noise. It was confirmed that the proposed polyimide binder tremendously improved the mechanical stability while reducing core losses and audible noise. Full article