Iron-silicon Alloys Research Articles

Spontaneous Skyrmion Bubbles in an Iron-Silicon Alloy with Uniaxial Magnetic Anisotropy.

The magnetic skyrmions exhibit intriguing topological behaviors, holding promise for future applications in the realm of spintronic devices. Despite recent advancements, achieving spontaneous magnetic skyrmions and topological transitions in magnets featuring uniaxial magnetic anisotropy, particularly at elevated temperatures (>100 K), remains a challenging endeavor. Here, single-crystal Fe5Si3 nanorods with the central symmetry and uniaxial magnetic anisotropy were successfully synthesized on a mica substrate through chemical vapor deposition, which exhibit a high Curie temperature (TC) of about 372 K. The real-time observation, facilitated by Lorentz transmission electron microscopy, revealed the spontaneous formation of magnetic skyrmions and evolution of domains in focused ion beam-prepared Fe5Si3 thin foils. Moreover, Fe5Si3 device transport measurements expose notable magnetoresistance (MR) effects, enabling the interchange between positive and negative MR across specific temperature settings. These results offer various potential avenues for exploring diverse topological spin textures and their formation mechanisms, indicating inventive applications for iron-silicon alloy in the realm of spintronics.

Properties of Glass-Ceramics Prepared from Industrial Multi-Wastes

Because of their excellent properties, glass-ceramics have been widely developed and applied in many fields, and there are many potential application values to be disseminated. The preparation of glass-ceramics from industrial slag and metallurgical waste provides a new way for the comprehensive utilization of solid waste. Coal gangue is the largest of all kinds of industrial waste slag, while iron tailings and high-carbon ferrochrome slag also occupy a large proportion of China’s industrial solid waste. With cheap industrial solid waste as the main raw material, the production of high-value-added glass-ceramics can reduce pollution, protect the ecological environment, and have good economic and social benefits. Cordierite glass-ceramics were prepared using the sintering method with coal gangue, iron tailings, and high-carbon ferrochrome slag as the main raw materials. Meanwhile, an iron silicon alloy containing chromium was obtained. The heat treatment system of basic glass was determined by differential scanning calorimetry (DSC), and the sintered product was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). An orthogonal test was used to analyze the effects of the mass of basic glass powder, molding pressure, and holding time on the grain size and crystallinity of the samples. The hardness, acid and alkali resistance, density, and water absorption of the sintered products were determined. The results show that the main crystal phase of the prepared glass-ceramics is cordierite. The optimal combination for the green body is “basic glass powder mass 6 g, molding pressure 35 MPa, holding time 10 min”. The properties of glass-ceramics are good. At the crystallization temperature of 970 °C, the Vickers hardness is up to 866 HV, and the bulk density is up to 2.99 g/cm3. This study may provide a useful reference for the treatment of industrial solid waste.

A model to account for magnetic permeability changes resulting from edge damage caused by laser cutting in a high performance cobalt-iron alloy

Laser cutting is the mainstay of electrical machine stator core manufacture for prototyping and for high value, small and medium batch sizes. However, it can introduce localized damage into electrical steels, with reduction in magnetic permeability and increase in core loss in regions adjacent to the edge. These phenomena have been studied in Silicon-iron alloys, but there is little published data on Cobalt-iron. This paper presents experimental measurements on magnetic edge damage effect in Cobalt-iron alloys due to laser cutting. The paper then uses magnetic measurements for an increasing number of cuts in test samples to develop a model that represents the deterioration of magnetic permeability with distance from the cut edge, including cumulative damage effects from multiple cuts. The model is suitable for incorporation into finite-element models, either as a continuous function of position or to generate individual magnetization curves for discrete layers in finite-element mesh. The paper concludes by using the model to generate a series of magnetization curves which include the damage effect and in turn uses these to predict the net magnetic behavior of a series of rectangular strips. Good agreement is obtained between these predictions and measurements of samples from the same batch of Cobalt-iron.

Improving the soft magnetic properties of binder jet printed iron-silicon alloy through boron addition

Fe–Si alloys are an essential class of soft magnetic materials due to their high magnetic permeability and low hysteresis loss. Increasing the Si content above 3 wt% promotes coarser grain sizes and greater electrical resistivity, thereby enhancing the magnetic properties, such as magnetic permeability and specific loss density. However, the increased silicon content makes the machining challenging. Additive manufacturing technologies enable production of near net shape Fe–Si alloys with high silicon content, practically eliminating the machining challenges. This work investigated the effects of Si content, which ranged from 3 to 5 wt%, and B content, which ranged from 0 to 0.25 wt%, on the microstructure and magnetic properties. The Fe–Si–B alloys were binder jet printed, where the sintering temperature was varied between 1200 and 1250 °C, and microstructure-magnetic property relationships were investigated by characterizing the magnetic permeability, intrinsic coercivity, grain size, and density. The Fe-5wt.%Si alloy with 0.25% B sintered at 1200 °C exhibited the highest magnetic relative permeability (4447) and the lowest intrinsic coercivity (47.8 A/m).

Biodegradable iron-silicon implants produced by additive manufacturing

Due to many negative and undesirable side effects from the use of permanent implants, the development of temporary implants based on biocompatible and biodegradable materials is a promising area of modern medicine. In the presented study, we have investigated complex-shaped iron-silicon (Fe–Si) scaffolds that can be used as potential biodegradable framework structures for solid implants for bone grafting. Since iron and silicon are biocompatible materials, and their alloy should also have biocompatibility. It has been demonstrated that cells, mesenchymal stromal cells derived from the human umbilical cord (UC-MSC) and 3T3, were attached to, spread, and proliferated on the Fe–Si scaffolds’ surface. Most of UC-MSC and 3T3 remained viable, only single dead cells were observed. According to the results of biological testing, the scaffolds have shown that deposition of calcium phosphate particles occurs on day one in the scaffold at the defect site that can be used as a primary marker of osteodifferentiation. These results demonstrate that the 3D-printed porous iron-silicon (Fe–Si) alloy scaffolds are promising structures for bone grafting and regeneration.

Composition-dependent thermal equation of state of B2 Fe-Si alloys at high pressure

AbstractSolid iron-silicon alloys play an important role in planetary cores, especially for planets that formed under reducing conditions, such as Mercury. The CsCl (B2) structure occupies a considerable portion of the Fe-Si binary phase diagram at pressure and temperature conditions relevant for the core of Mercury, yet its thermodynamic and thermoelastic properties are poorly known. Here, we report in situ X-ray diffraction measurements on iron-silicon alloys with 7–30 wt% Si performed in laser-heated diamond-anvil cells up to ~120 GPa and ~3000 K. Unit-cell volumes of the B2 phase at high pressures and high temperatures have been used to obtain a composition-dependent thermal equation of state of this phase. In turn, the thermal equation of state is exploited to determine the composition of the B2 phase in hcp+B2 mixtures at 30–100 GPa and to place constraints on the hcp+B2/B2 phase boundary, determined to vary between ~13–18 wt% Si in the considered pressure and temperature range. The hcp+B2/B2 boundary of Fe-Si alloys is observed to be dependent on pressure but weakly dependent on temperature. Our results, coupled with literature data on liquid equations of state, yield an estimation of the density contrast between B2 solid and liquid under Mercury’s core conditions, which directly relates to the buoyancy of the crystallizing material. While the density contrast may be large enough to form a solid inner core by the gravitational sinking of B2 alloys in a Si-rich core, the density of the B2 solid is close to that of the liquid at solidus conditions for Si concentration approaching ~10 wt% Si.

High-Speed Synchronous Reluctance Machines: Materials Selection and Performance Boundaries

This paper presents a comprehensive comparative design exercise of Synchronous Reluctance (SyR) machines considering different soft magnetic materials and a wide range of speeds. First, a general design methodology able to consider all the consequences of selecting different materials is presented. In fact, magnetic non-linearities, rotor structural limitations and the rise of both stator and rotor iron losses are all considered. The adopted design approach allows achieving optimal stator and rotor geometries balancing all these competitive multi-physics aspects and keeping constant the cooling system capability. Both silicon-iron (SiFe) and cobalt-iron (CoFe) alloys with optimized magnetic and mechanical performance are examined to assess the maximum capabilities achievable with a SyR machine technology. The adoption of CoFe alloys leads to machines that outperform the SiFe counterparts up to a certain speed, above which, machines with SiFe provide better performance. Indeed, in the lower speed range, the effect of the higher saturation flux density of the CoFe materials is dominant, while for higher design speeds, their higher iron losses and lower yield strength, with respect to the SiFe ones, make the latter more convenient. All the design considerations are finally validated by comparing the predicted performance with the experimental test results on a 6.5kW, 80krpm SyR machine prototype.

Improving the Soft Magnetic Properties of Binder Jet Printed Iron-Silicon Alloy Through Boron Addition

Improving the Soft Magnetic Properties of Binder Jet Printed Iron-Silicon Alloy Through Boron Addition

Surface Phenomena at the Interface between Silicon Carbide and Iron Alloy.

The paper discusses a potential composite produced using the casting method, where the matrix is gray cast iron with flake graphite. The reinforcement is provided by granular carborundum (β-SiC). The article presents model studies aimed at identifying the phenomena at the contact boundary resulting from the interaction of the liquid matrix with solid reinforcement particles. The scope of the research included, primarily, the metallographic analysis of the microstructure of the resulting composite, carried out by using light (LOM) and scanning electron (SEM) microscopy with energy dispersive X-ray spectroscopy (EDS) analysis. The occurrence of metallic phases in the boundary zone was indicated, the contents and morphology of which can be optimized in order to achieve favorable functional properties, mainly the tribological properties of the composite. In addition, the results obtained confirm the possibility of producing similar composites based on selected iron alloys.

Twin Roll Casting and Secondary Cooling of 6.0 wt.% Silicon Steel

Iron–silicon alloys with up to 6.5 wt.% Si offer an improvement of soft magnetic properties in electrical steels compared to conventional electrical steel grades. However, steels with high Si contents are very brittle and cannot be produced by cold rolling. In addition to solid solution hardening, it is assumed that the B2- and DO3-superlattice structures are responsible for the poor cold workability. In this work, two cast strips with 6.0 wt.% Si were successfully produced by the twin roll strip casting process and cooled differently by secondary cooling. The aim of the different cooling strategies was to suppress the formation of the embrittling superlattice structures and thus enable further processing by cold rolling. A comprehensive material characterization allows for the understanding of the influence of casting parameters and cooling strategies on segregation, microstructure and superlattice structure. The results show that both cooling strategies are not sufficient to prevent the formation of B2- and DO3-structures. Although the dark field images show a condition which is far from equilibrium, the achieved condition is not sufficient to ensure cold processing of the material.

Strong shear softening induced by superionic hydrogen in Earth's inner core

Geophysical and geochemical evidence suggests that Earth's core is predominantly made of iron (or iron-nickel alloy) with several percent of light elements. However, Earth's solid inner core transmits shear waves at a much lower velocity than expected from mineralogical models that are consistent with geochemical constraints. Here we investigate the effect of hydrogen on the elastic properties of iron and iron-silicon alloys using ab initio molecular dynamic simulations. We find that these H-bearing alloys maintain a superionic state under inner-core conditions and that their shear moduli exhibit a strong shear softening due to the superionic effect, with a corresponding reduction in VS. Several hcp-iron-silicon-hydrogen compositions can explain the observed density, VP, VS, and Poisson's ratio of the inner core simultaneously. Our results indicate that hydrogen is a significant component of the Earth's core, and that it may contain at least four ocean masses of water. This indicates that the Earth may have accreted wet and obtained its water from chondritic and/or nebular materials before or during core formation.

Evolving Highly Active Oxidic Iron(III) Phase from Corrosion of Intermetallic Iron Silicide to Master Efficient Electrocatalytic Water Oxidation and Selective Oxygenation of 5-Hydroxymethylfurfural.

In a green energy economy, electrocatalysis is essential for chemical energy conversion and to produce value added chemicals from regenerative resources. To be widely applicable, an electrocatalyst should comprise the Earth's crust's most abundant elements. The most abundant 3d metal, iron, with its multiple accessible redox states has been manifold applied in chemocatalytic processes. However, due to the low conductivity of FeIII Ox Hy phases, its applicability for targeted electrocatalytic oxidation reactions such as water oxidation is still limited. Herein, it is shown that iron incorporated in conductive intermetallic iron silicide (FeSi) can be employed to meet this challenge. In contrast to silicon-poor iron-silicon alloys, intermetallic FeSi possesses an ordered structure with a peculiar bonding situation including covalent and ionic contributions together with conducting electrons. Using in situ X-ray absorption and Raman spectroscopy, it could be demonstrated that, under the applied corrosive alkaline conditions, the FeSi partly forms a unique, oxidic iron(III) phase consisting of edge and corner sharing [FeO6 ] octahedra together with oxidized silicon species. This phase is capable of driving the oxyge evolution reaction (OER) at high efficiency under ambient and industrially relevant conditions (500mAcm-2 at 1.50±0.025VRHE and 65°C) and to selectively oxygenate 5-hydroxymethylfurfural (HMF).

Process and Kinetics of Extracting Cobalt from Complex High-Silicon White Alloy by Sulfuric Acid Oxidation Leaching

A sulfuric acid system was used to recover Co from cobalt white alloy, and the leached cobalt was electrochemically dissolved.i This is a key step to separate the iron-silicon alloy phase from valuable metals when leaching cobalt white alloys with high silicon and iron contents. As an additive, sodium hypochlorite (NaClO) acts as an oxidant to break cobalt encapsulation and enhances leaching. It generates chloride ions, which further enhance Co leaching based on their corrosive ability. The results showed that the maximum leaching ratio of Co from the waste cobalt white alloy was 97.76%. Kinetic analysis showed that the apparent activation energy of Co leaching was 34.58 kJ/mol, and the surface chemical reaction was a controlling step for this process. The kinetic equation for the leaching of Co can be expressed as $$1 - \left( {1 - \alpha } \right)^{\frac{1}{3}} = 0.065t \times \left( {r_{0}^{ - 1} } \right) \times \left[ {{\text{H}}_{2} {\text{SO}}_{4} } \right]^{2.44} \times \exp \left( {\frac{ - 34580}{{8.314T}}} \right)$$ .

Accretion formation on the refractory lining during the melting of ferrosilicon

SYNOPSIS Accretions often form in furnaces when slag and charge materials attach to the refractory wall and build up over time. Accretion formation is usually unwanted because it reduces the working volume of the reactor and hinders material flow through the reactor. However, in some instances a thin, stable accretion layer may be desirable to protect the underlying refractory material. In order to prevent and/or manage accretion formation, it is important to understand the underlying principles of this phenomenon in the particular reactor. Excessive accretion formation hampered production at the Exxaro FerroAlloys ferrosilicon melting and atomization plant. This plant uses induction furnaces in which a 15% silicon-iron alloy is produced by batch smelting a mixture of ferrosilicon of 75%Si grade and low-carbon steel. The molten ferrosilicon alloy is then gas-atomized to a powdered product for use as a dense medium in mineral processing plants. The objective of this study was to investigate the effect of different impurity levels in the ferrosilicon feed material on the extent of accretion formation as well as the effect on the accretion properties, which influence the ease of accretion removal upon furnace shut-down. Refractory and accretion samples were collected after a furnace shut-down and characterized using X-ray diffraction and scanning electron microscopy-energy dispersive spectroscopy. It was concluded that the trace elements in the FeSi-75 feed material (Al, Ca, Mn) were mostly responsible for accretion formation, but that rust on the low-carbon steel and oxidation of the steel contributed to accretion attachment to the lining. The total contaminant content, calcium to aluminium ratio in the FeSi-75 feed material, and thereby the liquid to solids ratio in the accretion at temperature determine the strength of attachment as well as growth of the accretion. Keywords: Accretion, build-up, slag, refractory lining, ferrosilicon.

Physico-Mechanical and Rheological Properties of Epoxy Adhesives Modified by Microsilica and Sonication Process.

Industrial waste from the production of metallic silicon and silicon–iron alloys, which includes silica fumes (microsilica), is subject to numerous applications aiming at its reuse in concrete and polymeric composites. Recycling solves the problem of their storage and adverse environmental impact. Six different formulas of epoxy resins were tested, differing in the type of polymer, the mixing process (sonication or not) and the presence of microsilica. The study showed that microsilica added to the epoxy resin changes its viscosity and free surface energy, and these are the parameters that determine the adhesion of the polymer to the concrete surface. Strength tests and SEM analysis have determined how microsilica molecules can penetrate the structure of polymer macromolecules by filling and forming temporary chemical bonds. Mixing the fillers with the adhesive was achieved by using a sonication process. The analysis of the obtained results showed that, depending on the initial composition of the polymer, the addition of microsilica can change the chemical, physical and mechanical properties of the hardened adhesive to varying degrees. In the case of adhesives used in the construction industry to strengthen and glue structural elements, these changes significantly affect the durability of the adhesive joints.

Magnetic behavior in commercial iron-silicon alloys controlled by the dislocation dynamics at temperatures below 420 K

A decrease of the temperature dependent coercive forces up to around 370 K is discovered in iron silicon alloys, both in quenched samples and in samples which were previously thermally treated to achieve the highest magnetic quality. Alloys of composition Fe-6 wt.% Si and Fe-3 wt.% Si are studied. This reduction in the coercive force is controlled by an increase in the mobility of the domain walls due to the increase in the dislocation’s mobility enhanced by the movement of vacancies. It is worthwhile to mention that this reduction in coercive force is only present at these slightly elevated temperatures which are markedly smaller than the usual annealing temperatures for heat treatment of iron silicon alloys while it disappears again at room temperature. Neutron thermodiffraction, magnetic hysteresis loops tracer and mechanical spectroscopy are used as experimental techniques.

Low thermal conductivity of iron-silicon alloys at Earth\u2019s core conditions with implications for the geodynamo

Earth’s core is composed of iron (Fe) alloyed with light elements, e.g., silicon (Si). Its thermal conductivity critically affects Earth’s thermal structure, evolution, and dynamics, as it controls the magnitude of thermal and compositional sources required to sustain a geodynamo over Earth’s history. Here we directly measured thermal conductivities of solid Fe and Fe–Si alloys up to 144 GPa and 3300 K. 15 at% Si alloyed in Fe substantially reduces its conductivity by about 2 folds at 132 GPa and 3000 K. An outer core with 15 at% Si would have a conductivity of about 20 W m−1 K−1, lower than pure Fe at similar pressure–temperature conditions. This suggests a lower minimum heat flow, around 3 TW, across the core–mantle boundary than previously expected, and thus less thermal energy needed to operate the geodynamo. Our results provide key constraints on inner core age that could be older than two billion-years.

Comparative analysis and application area of the main materials of anode groundbeds

Anode groundbeds are intended for use as low-soluble elements of cathodic protection systems against corrosion of main pipelines and other underground metal structures. The classification of Anode groundbeds into deep, subsurface and extended ones indicates the features of their construction and the method of installation. At the time their application area is determined primarily by the material of the working electrode of the Anode groundbed. With the development of modern technologies, as well as the ability to purchase working elements for anodes on the world market, a large number of new Anode groundbeds from different materials have appeared. In this case, the declared technical characteristics of even the same type of materials from different manufacturers may vary greatly. This situation makes it difficult for design organizations and anti-corrosion protection specialists to select the most suitable Anode groundbeds for specific operating conditions. This article provides an analysis of the performance properties of the main materials of Anode groundbeds and, based on the limitations inherent in each material, provides the recommended area of their application. The materials such as mixed metal oxide (MMO), manganese dioxide, graphite, silicon iron alloy and magnetite are reviewed.

Metallographic and magnetic analysis of direct laser sintered soft magnetic composites

In this present study, soft magnetic composite samples were made from iron-silicon alloys. For the purpose of optimizing 3D printing parameters, preliminary experiments were performed. Metallographic and computed tomography investigations were used to determine the appropriate sintering settings. Besides the microscopic and CT analysis, considering the permeability spectra have been compared to the samples.

Phase, microstructure, and wear behavior of Al2O3-reinforced Fe–Si alloy-based metal matrix nanocomposites

In the present work, phase, microstructure, and wear properties of Al2O3-reinforced Fe–Si alloy-based metal matrix nanocomposites have been studied. Composites using 2 wt.% and 5 wt.% of Si and rest Fe powder mix were synthesized via powder metallurgy and sintered at different temperature schedules. Iron–silicon alloy specimens were found to have high hardness and high wear resistance in comparison to pure iron specimens. Addition of 5 wt.% and 10 wt.% alumina reinforcement in Fe–Si alloy composition helped in developing iron aluminate (FeAl2O4) phase in composites which further improved the mechanical properties i.e. high hardness and wear resistance. Formation of iron aluminate phase occurs due to reactive sintering between Fe and Al2O3 particles. It is expected that the improved behavior of prepared nanocomposites as compared to conventional metals will be helpful in finding their use for wide industrial applications.