Amorphous Fe-B Alloys Research Articles

The influence of the cluster connection modes on the soft magnetic properties in the Fe78Si9B13 amorphous ribbon

The structures and magnetic properties of Fe78Si9B13 amorphous ribbons were detected after annealing at different temperatures. Compared with the clusters in the FeB amorphous alloy, the second shell of BB coordination is replaced by SiB coordination in the clusters of the Fe78Si9B13 amorphous alloy. The interaction between Fe and B atoms is strengthened at a higher annealing temperature. Based on the Gaussian decomposition toward the splitting second peaks in g(r) curves, the shared connection modes of the clusters have been obtained. The main connection modes between the clusters of all the samples are the three-atom-shared connection and the one-atom-shared connection. With the increasing annealing temperature, the three-atom-shared connection is enhanced, and the one-atom-shared connections are weakened. Combined with the results of the magnetic hysteresis curves, it is found that the enhancement of the three-atom-shared connection is responsible for the increase of the saturation magnetization.

Application of the Mixing Rule to Evaluation of the Thermophysical Properties of Amorphous Fe80B20 Alloy

Application of the Mixing Rule to Evaluation of the Thermophysical Properties of Amorphous Fe80B20 Alloy

Effects of the Addition of Co or Ni Atoms on Structure and Magnetism of FeB Amorphous Alloy: Ab Initio Molecular Dynamics Simulation.

The effects of the substitution of Fe by Co or Ni on both the structure and the magnetic properties of FeB amorphous alloy were investigated using first-principle molecular dynamics. The pair distribution function, Voronoi polyhedra, and density of states of Fe80−xTMxB20 (x = 0, 10, 20, 30, and 40 at.%, TM(Transition Metal): Co, Ni) amorphous alloys were calculated. The results show that with the increase in Co content, the saturation magnetization of Fe80−xCoxB20 (x = 0, 10, 20, 30, and 40 at.%) amorphous alloys initially increases and then decreases upon reaching the maximum at x = 10 at.%, while for Fe80−xNixB20 (x = 0, 10, 20, 30, and 40 at.%), the saturation magnetization decreases monotonously with the increase in Ni content. Accordingly, for the two kinds of amorphous alloys, the obtained simulation results on the variation trends of the saturation magnetization with the change in alloy composition are in good agreement with the experimental observation. Furthermore, the relative maximum magnetic moment was recorded for Fe70Co10B20 amorphous alloy, due to the induced increased magnetic moments of the Fe atoms surrounding the Co atom in the case of low Co dopant, as well as the increase in the exchange splitting energy caused by the enhancement of local atomic symmetry.

Fe2O3@FeB composites facilitate heterogeneous Fenton process by efficient Fe(III)/Fe(II) cycle and in-situ H2O2 generation

In this study, we fabricated a micro-nano structured Fe2O3@FeB composites by treating commercial Fe2O3 with sodium borohydride. The outside amorphous FeB alloy shell endowed the Fe2O3@FeB with remarkable Fenton-like performance in organic pollutants oxidation by efficient Fe(III)/Fe(II) cycle. For instance, the pseudo first-order rate constants of RhB degradation using Fe2O3@FeB as Fenton reagent was 74.6 times that of the Fe2O3 counterpart, the hydroxyl radical generation rate of Fe2O3@FeB was 1-3 orders of magnitude larger than that of other heterogeneous Fenton reagent. Further mechanistic study unveiled that FeB was oxidized accompanying with Fe(0) and B(0) continuously donated electrons to Fe(III) to secure the efficient generation of surface Fe(II), which could generate additional H2O2 by consecutive single-electron molecular oxygen activation (O2→•O2−→H2O2), leading to enhance •OH production and Fenton-degradation toward typical pollutants. This study provides a facile route for efficient heterogeneous Fenton and strengthens the vital role of molecular oxygen activation on Fenton-like process.

A Non-Isokinetic Approach for Modeling Solid-State Transformations: Application to Crystallization of a Fe-B Amorphous Alloy.

Solid-state phase transformations like crystallization of amorphous alloys can be described by an analytical model incorporating a nucleation index a. However, this model cannot be used to examine isochronal transformations with abrupt changing of enthalpy differences performed with differential scanning calorimetry. Based on the model, a non-isokinetic approach is proposed and applied to analyze the isochronal crystallization kinetics of Fe85B15 amorphous alloy. The approach enabled us to obtain the kinetic parameters and activation energies for nucleation and growth.

Nanocrystalline soft magnetic materials from binary alloy precursors with high saturation magnetization

A brief survey of the recent advances in Fe-based nanocrystalline soft magnetic alloys has shown that the saturation magnetization (Js) of these alloys is governed by the mass fraction, rather than the atomic fraction, of the nonmagnetic additives. Thus, the ultimate limit of Js in the alloys prepared by nano-crystallization of amorphous precursors is expected in an Fe-B binary system where amorphization by rapid quenching takes place with the lowest mass fraction of glass forming elements in Fe-based systems. We will demonstrate that nano-crystallization is possible in this binary system when the precursor amorphous phase is annealed ultra-rapidly. While the grain size after conventional annealing for amorphous Fe-B alloys is too large for the exchange softening effect, a small grain size well below the exchange length is obtained after annealing with a heating rate of 103 – 104 K/s. This results in magnetically soft nanostructures with Fe content up to 97.2 wt. %, leading to a high Js ≥ 1.9 T with a small coercivity (Hc) between 3.8 and 6.4 A/m. An addition of Co to nc-Fe87B13 results in a higher Js of 2.0 T with a slight increase of Hc to 9.3 A/m. The soft magnetic properties of these ultra-rapidly annealed alloys (named HiB-Nanoperm) is well understood by the random anisotropy model. The formation of nano-meter scale microstructures in a simple binary system unlocks previously unavailable alloy design strategies in nanostructured systems which is not only relevant to magnetic materials but, also to structural materials.

Facile chemical synthesis of amorphous FeB alloy nanoparticles and their superior electromagnetic wave absorption performance

Currently, the magnetic metal based electromagnetic wave absorber have attracted extensively interest. However, how to control the high conductivity of magnetic metals and achieve good impedance matching of electromagnetic absorbing materials made by them have become a big problem at present. Herein, amorphous FeB nanoparticles were rationally synthesized by a wet method, which involves a simple three-step solution reaction. The obtained products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and vibrating sample magnetometer (VSM). Benefiting from their amorphous structure, the resulting FeB nanoparticles show good magnetic properties, dielectric losses and proper impedance matching, thus good microwave attenuation ability can be achieved in the low frequency range. The maximum reflection loss is −15 dB at 3.5 GHz with a thickness of 8 mm which can be mainly attributed to its excellent impedance matching in the frequency range of 2.5–4.5 GHz. These amorphous FeB alloy nanoparticles are expected to be promising candidates for efficient microwave absorbers in the S band.

Formation of micro/nano pits with high catalytic activity on Fe80B20 amorphous alloy

In this work, micro/nano size pits were introduced to the surface of Fe80B20 amorphous ribbons by electrochemical etching treatment. The results show that the size of the pits is more sensitive to the applied etching potential, while the pit homogeneity is time dependent. The etching treatment at −0.30 V (vs saturated calomel electrode) for three hours in 1 M HCl solution saturated by KCl leads to the formation of numerous pits with an average diameter of 222 nm. The large amount of pits results in higher degradation efficiency on Direct Blue 15 when compared with the as-spun amorphous alloy.

On the Concentration and Phase-relation Dependence of Seebeck Coefficient and the Contact Angle in Metallic Solutions

The focus of this paper is the deeper understanding of the effect of the change in the electronic structure on the wetting angle and transport properties. For this purpose, using the alloys from the earlier study, the thermopower has been measured and the Seebeck coefficient has also been determined in room temperature (solidified state). During the experiments in both case the modification of the electronic structure were performed by alloying on a way, that the investigated systems are terminal (α) solutions in solid state. The concentration dependence of property changes are interpreted on the bases of free electron model elaborated earlier for this alloy types. This prediction fits well also to the concentration dependence of heat of formation in these alloys. Similar concentration dependence has been also found between the Seebeck coefficient, the resistivity and the heat of mixing in α-phase Fe-Ni alloys. The shift of thermopower were also monitored in order to detect the crystallization (first oreder transformation) starting form amorphous Fe-B alloys.

Fe-B alloy coupled with Fe clusters as an efficient cocatalyst for photocatalytic hydrogen evolution

It remains a challenge to develop efficient and inexpensive catalysts for hydrogen evolution reaction (HER). Herein, it is the first time to report a core-shell structured amorphous Fe-B alloy coupled with metal Fe nanoclusters as an efficient HER catalyst. The composite was fabricated via the transformation of the FeOOH coating on amorphous Fe-B alloy into metal Fe through a simple photoreduction approach. The Fe nanoclusters loaded on amorphous Fe-B alloy improve the catalytic HER. Thus, the as-prepared composite exhibits much better electrocatalytic and photocatalytic HER activities than single Fe and Fe-B alloy, that is, there is a synergic effect between Fe metal and amorphous Fe-B alloy. The highest apparent quantum yield (AQY) for photocatalytic HER reaches 34% at 470 nm with Eosin Y as a photosensitizer. The composite cocatalyst can be recovered by a magnetic field after the dye-sensitized photocatalytic HER. More interestingly, the electrocatalytic HER activity of Fe-B@Fe-10 in alkaline solution surpasses that of foam Ni used in industrial water electrolysis, and the core-shell composite shows excellent HER performance at high current density. The findings provide new insights to develop efficient and stable noble-metal-free HER catalysts.

High entropy effect on structure and properties of (Fe,Co,Ni,Cr)-B amorphous alloys

We examined high entropy (HE) effect on the formation, structure, thermal stability, mechanical properties and corrosion behavior for (Fe,Co,Ni,Cr)100-xBx (x = 18–26) amorphous alloys in comparison with Fe100-xBx amorphous alloys. The as-quenched structure consists of an amorphous single phase for the 18–24%B alloys, and amorphous + tetragonal Cr5B3 phases for the 26%B alloy. The broad diffraction peak position due to amorphous phase shifts to a higher wave vector side with increasing B content for the HE alloys, while that of the Fe-B alloys changes to the lower wave vector side, indicating the distinct difference in disordered atomic structure between the HE alloys and the binary alloys. All the as-spun HEA ribbons exhibit good bending ductility in spite of the coexistence with their crystalline phases, being different from the brittle nature for the 26%B binary alloy. The crystallization temperature (Tx) and Vickers hardness (Hv) increase with increasing B content, show maximum values of 803 K and 1130, respectively, at 22%B and then decrease to 793 K and 1070, respectively at 26%B, being different from the nearly constant Tx and almost linear increase in Hv with increasing B content for the Fe100-xBx alloys. The corrosion resistance in NaCl, H2SO4 and HCl solutions evaluated by potential and anode current density is much better for the HE alloys as compared with the Fe-B alloys. Thus, the Tx, Hv, bending ductility and corrosion resistance for the HE amorphous alloys containing more than 20 at%B are much superior to those for the Fe-B amorphous alloys. The fully crystallized structure consists of fcc + FeB + Fe2B + Cr5B3 phase for the HE 22–26 at%B alloys and bcc-Fe + Fe2B for the Fe-B alloys. The significant improvement of the fundamental properties caused by the HE component modification is presumably due to the formation of Cr-B pair with higher B-rich components. The improved properties in conjunction with the change in the disordered structure for the HE amorphous alloys provide an opportunity of developing a new functional material by alloy design to HE type compositions.

Effects of annealing on the structure and magnetic properties of Fe80B20 magnetostrictive fibers.

Fe80B20 amorphous alloys exhibit excellent soft magnetic properties, high abrasive resistance and outstanding corrosion resistance. In this work, Fe80B20 amorphous micro-fibers with HC of 3.33 Oe were firstly fabricated and the effects of annealing temperature on the structure and magnetic properties of the fibers were investigated. In this study, Fe80B20 amorphous fibers were prepared by the single roller melt-spinning method. The structures of as-spun and annealed fibers were investigated by X-ray diffractometer (XRD) (PANalytical X,Pert Power) using Cu Kα radiation. The morphology of the fibers was observed by scanning electron microscopy (SEM) (HITACHI-S4800). Differential scanning calorimetry (DSC) measurements of the fibers were performed on Mettler Toledo TGA/DSC1 device under N2 protection. Vibrating sample magnetometer (VSM, Versalab) was used to examine the magnetic properties of the fibers. The resonance behavior of the fibers was characterized by an impedance analyzer (Agilent 4294A) with a home-made copper coil. The X-ray diffusion (XRD) patterns show that the fibers remain amorphous structure until the annealing temperature reaches 500°C. The differential scanning calorimetry (DSC) results show that the crystallization temperature of the fibers is 449°C. The crystallization activation energy is calculated to be 221 kJ/mol using Kissinger formula. The scanning electron microscopy (SEM) images show that a few dendrites appear at the fiber surface after annealing. The result indicates that the coercivity HC (//) and HC (⊥) slightly increases with increasing annealing temperature until 400°C, and then dramatically increases with further increasing annealing temperature which is due to significant increase in magneto-crystalline anisotropy and magneto-elastic anisotropy. The Q value firstly increases slightly when the annealing temperature rises from room temperature (RT) to 300°C, then decreases until 400°C. Eventually, the value of Q increases to ~2000 at annealing temperature of 500°C. In this study, Fe80B20 amorphous fibers with the diameter of 60 μm were prepared by the single roller melt-spinning method and annealed at 200°C, 300°C, 400°C, and 500°C, respectively. XRD results indicate that the fiber structure remains amorphous when the annealing temperature is below 400°C. α-Fe phase and Fe3B phase appear when the annealing temperature rises to 500°C, which is above the crystallization temperature of 449°C. The recrystallization activation energy is calculated to be 221 kJ/mol. The coercivity increases with increasing annealing temperature, which attributes to the increase of total anisotropy. All the as-spun and annealed fibers exhibit good resonance behavior for magnetostrictive sensors.

Magnetic Fe3O4–FeB nanocomposites with promoted Cr(VI) removal performance

In this study, amorphous FeB alloy modified magnetite nanocomposites (Fe3O4–FeB) were facilely synthesized by interfacial reduction of commercial Fe3O4 nanoparticles with NaBH4. TEM, CS-STEM integrated with EDS, Mössbauer spectroscopy analysis confirmed the formation of Fe3O4–FeB, where a shell of amorphous FeB nanoparticles with 2–4nm in size was surrounded on the inner magnetite Fe3O4 part. Fe3O4–FeB displayed a promoted Cr(VI) removal efficiency compared with the bare Fe3O4 counterpart, the interfacial reduced Fe3O4 nanoparticles with hydrogen and/or with hydrazine hydride. XPS analysis evidenced that reduction of Cr(VI) on surface of the Fe3O4–FeB was the major contribution to the Cr(VI) removal. Tafel polarization analysis of the Fe3O4–FeB and aqueous boron species measurement indicated that high Cr(VI) removal efficiency with Fe3O4–FeB was highly depended on amorphous FeB alloy shell, in which boron element containing free electrons could accelerate the electron transfer from Fe to the adsorbed Cr(VI), as well reduce Fe(III) to Fe(II) and thus promote the Fe(III)/Fe(II) cycles. The efficient Cr(VI) removal under a wide range of pH values and its easy magnetic separation make the Fe3O4–FeB be a potential for Cr(VI) contaminated water treatment.

Phase formation and controlled nanostructuring in amorphous Fe80B20 alloy

The temperature dependence of the volume fraction of the crystalline phase in Fe80B20 amorphous alloy is calculated using equations from the homogeneous nucleation theory of binary systems. It is shown that the crystallization of Fe80B20 alloy is two-stage, as is confirmed by the experimental data obtained by means of highly sensitive dilatometry and X-ray diffractometry. On the basis of results of calculations performed within the theory of the high-temperature stability of amorphous alloys, two areas of its practical application are proposed: (i) enhancing the thermal stability of amorphous alloys by isothermal annealing in the range of temperatures where crystalline nuclei can transition to the amorphous phase; (ii) controlled nanostructuring of the amorphous state with different modes of treatment. Methods are proposed for obtaining the nanostructured state from the initial amorphous state. Alloys in the nanocrystalline state are obtained, as is confirmed by the results from electron microscope investigations.

Electrochemical Synthesis of Amorphous Fe-B Alloys for Magnetostrictive Resonant Sensor

Fe-B alloy films were fabricated by an electrochemical deposition method. The effects of deposition parameters including current density, solution concentration, and ratio of precursors on crystallinity and magnetostrictivity were investigated. Amorphous Fe-B alloy films were obtained in the conditions of effective boron incorporation and high nucleation rate by increasing current density, solution concentration, and ratio of iron precursor. The results indicate that amorphous phase formation is related to deposition kinetics and chemical affinity between iron and boron precursors. The magnetostrictive characterization of the deposited amorphous Fe-B alloys demonstrated a potential biosensor platform of the films.

Effect of thermomechanical processing on the thermal stability of amorphous Fe-B alloys

Results from investigating the effect of thermomechanical processing on the thermal stability of amorphous Fe-B alloys are presented. It is shown that the combined thermomechanical processing of amorphous alloys raises the temperature of intense crystallization onset by 80 K for binary alloys; by 20–50 K, for multicomponent alloys. The greater expansion of the thermal stability interval of binary alloys relative to multicomponent alloys is explained by the presence of alloying dopants such as molybdenum, nickel, and silicon that inhibit the diffusion of boron and thus hinders nucleation and the growth of the crystalline phase. The enhanced thermal stability of amorphous alloys induced by thermomechanical processing is explained by the reduction in size of amorphous-phase frozen crystallization centers and by the formation of a nanostructured state.

Influence of a magnetic field applied during the quenching process on the spin density and nanoscale structure of an amorphous Fe–B ribbon

The application of a magnetic field to the melt in the transverse direction of the wheel rotation during the solidification process induces magnetic anisotropy in amorphous magnetic ribbons. This procedure is here applied to a FeB amorphous alloy in order to check their influence on local electronic and nanoscale structure by comparing two samples (as quenched without field and field quenched). The existence of magnetic domains was showed via the Bitter technique. Mössbauer spectra analysis confirms an increase in the spin density (from 28 to 48%) in the applied field direction for the field quenched ribbon. Positron lifetime spectra analysis determines that at room temperature there is no influence on the nanoscale structure, but the annealing at 300°C provokes the beginning of the nanocrystallization process in the field quenched sample while the samples as quenched without field remain fully amorphous.

Reverse martensite transformation in iron nanocrystals under severe plastic deformation

Structure of amorphous Fe80B20 alloy was studied after high‐pressure torsion method. The deformation leads to nanocrystallization with α-Fe particle formation. Although the average size of α-Fe particles does not exceed 10nm, some particles sized of 20nm were observed as well. These particles consist of α-Fe and γ-Fe regions. The lattices of these regions are in orientation relationship testifying martensite transformation. The martensite transformation occurring in the largest nanocrystals lead to fragmentation of the nanocrystals.

Top and bottom interfaces in Fe-B multilayers investigated by Mössbauer spectroscopy

M\"ossbauer spectroscopy is frequently applied to gain information on the interfaces in multilayers, and recently the layer sequence permutation of multitrilayers was suggested to enhance its capability to characterize bottom and top interfaces of a given layer. The sequence permutation, however, in the investigated Fe-B-Ag multitrilayers affected the waviness of the layers as well, and the results hinted at the possibility that although Ag does not mix with Fe and B, the Fe-B amorphous alloy formation is influenced by the layer-sequence-dependent morphology of the Ag layers in the multitrilayers. Now we examine the interface mixing of Fe and B in the case of a fixed layer sequence and varying thickness of the Ag layers in [2 nm B/2 nm Fe/$x$ nm Ag]${}_{4}$, $0.2\ensuremath{\le}x\ensuremath{\le}10$, multitrilayer samples and in B/Fe/B and B/Fe/Ag trilayers. Below $x=5$ nm, both the ratio of the nonalloyed Fe layer and the average hyperfine field of the amorphous Fe-B interface compound change. The variation is attributed to thickness-dependent discontinuities of the Ag layers. Ag acts as a barrier to the diffusion of B from the top side and thus the discontinuities lead to a varying ratio of top and bottom interfaces. The evaluation based on this model shows that the ``B on top of Fe'' interface has an average B concentration about 11 at. % higher than the ``Fe on top of B'' interface. A slightly smaller difference, 6 at. %, is deduced from low-temperature conversion electron M\"ossbauer spectroscopy measurements of the trilayers.

Short-range order in amorphous ferromagnetic Fe-B alloys

Amorphous and quenched crystalline Fe-B alloys in the composition range of 4–25 at % B were prepared by melt spinning and investigated by 57Fe Mossbauer spectroscopy at T = 87 K. The states of iron atoms in the α-Fe phases, including iron atoms having boron atoms in the nearest coordination sphere, and in the orthorhombic (o) and tetragonal (T) Fe2B phases are detected in the microcrystalline alloys. The short-range order and the local atomic structure of the amorphous Fe-B alloys are determined. The amorphous alloys consist of microregions (clusters) with short-range order of the t- and o-Fe2B and α-Fe types. The dependence of the content of various types of clusters on the alloy composition is quantitatively estimated.