Ferromagnetic Composites Research Articles

Self-Induced Magnetic Anisotropy in 3-D Printed Ferromagnetic Composites

Self-Induced Magnetic Anisotropy in 3-D Printed Ferromagnetic Composites

Microwaves in ferromagnetic composites Fe/Epoxy with aggregates of nanoparticles: Theory and experiment

Microwave transmission through plates of a composite material containing spherical Fe nanoparticles in an epoxyamine matrix and reflection from plates have been studied. Measurements were carried out at the frequencies from 26 to 32 GHz in the magnetic fields up to 12 kOe. The ferromagnetic resonance phenomenon in the composite has been investigated. The theory of electromagnetic waves transmitting through a composite material containing ferromagnetic particles, taking into account aggregating the particles, has been developed. A good agreement of calculation results and experimentally obtained field dependences of the transmission and reflection coefficients, as well as microwaves dissipation, has been achieved.

Variation of color of magnetic noise in Er3+ molecular magnets contacting metal surface in ferromagnetic composite

Interaction between single molecule magnets (SMMs) and metal surface is a hot topic promising controllable deposition of SMMs, programmable frequency of magnetic relaxation and addressed reading of information. In this paper, we develop strategy of the Er3+ based SMM functionalization by its penetration inside the arrays of Ferromagnetic Micro Particles (FMPs). We show that predictable residual magnetic field of the FMPs arrays is an effective tool for regulation of the frequency maximum of imaginary magnetic susceptibility. We analyzed color of magnetic noise in respect to physical origin of magnetic relaxation. An additional channel for control over spin noise is formation of chemical bonds between SMM and the FMPs surface. Oxidation of an Er complex transforms 20 ± 5 % of the initial 10-coordinated SMM complex to the 9-coordinated complex with reduced relaxation time. Memorized residual magnetization of the composite material allows one to set desirable relaxation frequency in the individual micronized cells to create a sound frequency register. The proposed compaction of SMMs of different types in ferromagnetic composites provides engineering of the chemically designed spin interface on ferromagnetic surface for spintronics and quantum computing.

Building TiO2-doped magnetic biochars from Citrus sinensis peels as low-cost materials for improved dye degradation using a mathematical approach

TiO2-doped ferromagnetic (TiFeBC) composites were synthesised from lignocellulosic orange peel biochar (BC) material using co-precipitation method. Several characterization techniques (XRD, SEM, EDX, FT-IR, EIS and N2 adsorption-desorption) were used to confirm the presence of Fe3O4 and TiO2 particles impregnated within the carbonaceous matrix of the biochar. Electrochemical impedance spectroscopy revealed that the sample obtained using 2.5 wt. % of TiO2 (TiFeBC1) has the lowest charge transfer resistance compared to those of 5 wt.% and 7.5 wt.%. TiFeBC1 was used for the optimization of the degradation of reactive yellow-145 from Cameroon Textile Industry using Fenton process. Optimum operational parameters were found to be: pH of 2.02, initial dye concentration of 75 mg/L, mass of material of 5998 mg/L and a time of 16.01 min. Using the CCD of the Response Surface Methodology, a predicted optimum response of 98.89 % was obtained in agreement with an experimental response of 97.95 % of dye degradation. Analysis of variance presented good correlation between the experimental data and the postulated model (R2 = 94.24 % and R2adjusted = 87.52 %). The degradation reaction was found to obey the first order kinetic rate law (R2 = 0.986) with respect to the dye. The study of interfering processes revealed that adsorption and H2O2/daylight-assisted degradation are two phenomenon that could possibly contribute to a negligible extent to the elimination of the dye during the Fenton process. The stability and efficiency of TiFeBC1 was evaluated over ten cycles and the material was found to lose approximately 5 % of its efficiency.

Ferromagnetic metal organic framework (MOF)/alginate hybrid beads for atmospheric water capture and induction heating-enabled water release

Atmospheric water harvesting (AWH) using sorbents has been proposed as a promising alternative to tackle the pressing issue of freshwater scarcity, particularly in densely populated metropolitan cities. However, successful deployment of this technology hinges on two critical prerequisites: high water capture capacity and low energy consumption for quick water release. In this work, a novel hybrid ferromagnetic MOF-alginate composite (MOF-AG@IO) bead for atmospheric water harvesting is presented. Using an ionic gel polymerization technique, instantaneous formation of MOF-AG@IO bead was achieved. SEM-EDX and XRD analysis revealed successful incorporation of MOF-808 crystals in the hydrogel together with CaCl2 and Fe3O4 particles. The composite exhibited high water capturing capacity from the atmosphere (∼ 1.02 gH2O/gMOF-AG@IO, 75 % RH, 25 °C) and, owing to Fe3O4 presence, quick water releasing capability (∼ 85 % water release within the first 30 min.) when exposed to magnetic induction, a technology not limited by the natural day-light cycle. The composite also showed cyclic stability, high water uptake kinetics (∼0.8 g/g at 75 % RH and 25 °C within 4 h) and excellent feasible water productivity of ∼9.11 LH2O/kgMOF-AG@IO/day. This potential productivity surpasses any previously reported values for MOF and MOF composites. Further, the composite sorbent exhibited high stability in outdoor conditions with no decline in water uptake capacity for multiple cycles. In summary, the novel ferromagnetic composite, which demonstrates a synergy of its constituent properties, offers itself as an attractive candidate for next-generation water harvesting devices integrated with electrified heating technology.

Synthesis and characterization of ferromagnetic polyaniline-cobalt chloride composite through in situ oxidative polymerization technique

Synthesis and characterization of ferromagnetic polyaniline-cobalt chloride composite through in situ oxidative polymerization technique

A finite element based heterogeneous multiscale method for the Landau-Lifshitz equation

We present a Heterogeneous Multiscale Method for the Landau-Lifshitz equation with a highly oscillatory diffusion coefficient, a simple model for a ferromagnetic composite. A finite element macro scheme is combined with a finite difference micro model to approximate the effective equation corresponding to the original problem. This makes it possible to obtain effective solutions to problems with rapid material variations on a small scale, described by ε≪1, which would be too expensive to resolve in a conventional simulation.

Ho-Ion-Polymer/Graphene Heterojunctions Toward Room-Temperature Ferromagnets.

Organic ferromagnetic materials offer great promise for spintronic devices, carbon-based chips, and quantum communications, but remain as a challenging issue due to their low saturation magnetization and/or unsustainable ferromagnetic properties. To date, magnetic ion polymers have displayed paramagnetism without exception at room-temperature. In this study, it is reported for the first time that, owing to the structural restriction and charge exchange of Ho ion by polymer/graphene π-π stacking heterojunctions, holmium ion polymer composites exhibited typical hysteresis lines of ferromagnetic materials at room temperature. The room-temperature ferromagnetic ion polymer composite presented the highest saturation magnetization value of 3.36 emu g-1 and unprecedented sustainable ferromagnetism, compared to reported room-temperature organic ferromagnetic materials. Accordingly, prepared ferromagnetic composites also achieved impressive wave absorption properties, with a maximum reflection loss of as much as -57.32dB and a broad absorption bandwidth of 5.05GHz. These findings may promote the development of room-temperature organic ferromagnetic materials.

A ferromagnetic composite of PEDOT:PSS and nitrogen-graphene decorated with copper oxide nanoparticles with high anisotropic thermoelectric properties

PP/CuONG system has been designed for high TE properties. CuONG plays a dual role in increasing S by the dipole and interfacial polarizations and the spin Seebeck coefficient and lowering k by phonons scattering and gaseous (N-/static air) environs.

On the structural characteristics of 45S5-xSFO bioglass-ceramic composites for medical applications

Bioactive ferromagnetic glass-ceramics composites have been prepared through the combination of the quenching and solid-state reaction (SSR) sintering methods, viewing their integration in biomedical applications. The material under study consists of a glassy system with the chemical formula (94-2x)SiO2−xNa2O−xCaO-6P2O5, which acts as host-matrix for the magnetic phase (strontium ferrite). The samples were obtained by a modified incorporation technique, where the magnetic phase, previously synthetized by the SSR method, was added to the glass-matrix in desired proportions. The physical properties were investigated considering the analysis of the X-ray diffraction as well as Raman spectroscopy techniques, both performed at room temperature. Results revealed the formation of partially crystallized bioglass-ceramics, with a strong influence of the magnetic phase on the crystallization kinetics, which suggests the obtained bioactive composites promising materials for clinical treatments.

Determination of a quantitative relationship between deposition duration and magnetic performance of soft ferromagnetic composites via data-analysis and theoretical models

The industrial production of soft ferromagnetic composites demands a quantitative description of process parameters and magnetic performance. Here, Fe–Si/SiO2 soft ferromagnetic composites were prepared via a two-step method combining chemical vapour deposition and hot-pressed sintering. Investigations of surface and section morphology, phase composition and crystal structure were undertaken to characterise the deposition duration-dependence of SiO2 insulation coating thickness in Fe–Si/SiO2 soft ferromagnetic composites. A vibrating sample magnetometer, a resistivity tester and a B–H analyser were used to study the magnetic behaviours of Fe–Si/SiO2 soft ferromagnetic composites. Based on curves of deposition duration-dependence of SiO2 insulation coating thickness and other theoretical models, quantitative relationships between deposition duration and magnetic performance were determined for Fe–Si/SiO2 soft ferromagnetic composites. These results demonstrate that the coating and crystallisation of SiO2 insulation coatings had no influence on the crystal structure of Fe–Si substrate particles and that SiO2 insulation coating thickness increased linearly with deposition duration. Total core loss of Fe–Si/SiO2 soft ferromagnetic composites was strongly predicted by SiO2 insulation coating thickness. A quantitative equation relating magnetisation intensity to Fe–Si/SiO2 soft ferromagnetic composite deposition duration was derived on the basis of experimental data and subsequent model selection. Additional quantitative equations relating electrical resistivity and eddy current loss to Fe–Si/SiO2 soft ferromagnetic composite deposition duration were determined according to electromagnetic theory. These results establish a precise adjustment mechanism for magnetic behaviour in Fe–Si/SiO2 soft ferromagnetic composites and promote the industrialisation of a new preparation process combining chemical vapour deposition and hot-pressed sintering.

Development of quantitative parameter–property relationship and technology parameter choosing software of Fe(Si)–SiO2 soft ferromagnetic composites

Intelligent technology parameter choosing software is the future development trend of realizing precisely control and efficient production. However, the technology parameter choosing software has not been reported probably due to the lack of in-depth understanding of quantitative relationship between technology parameter and magnetic properties for soft ferromagnetic composites. This paper describes a novel strategy to construct quantitative relationship model and develop technology parameter choosing software. Using gas precursor concentration parameter during fluidized bed chemical vapor deposition as an example, the microstructure and performances of Fe(Si)–SiO2 soft ferromagnetic composites obtained were systematically studied. The quantitative relationships between gas precursor concentration and magnetic performances were built based on the gas precursor concentration dependence of SiO2 insulating layer thickness and other classical theoretical models. The findings suggest that the saturation magnetization increase with the gas precursor concentration; however, the impacts of the gas precursor concentration on electrical resistivity and eddy current loss are relatively complex. Informed by these quantitative relationship models, the supporting software has been designed, which can configure the technology parameter automaticity according to the target performance of soft ferromagnetic composites. The results may deepen the understanding on the quantitative relationship and provide ideas for developing efficient production control software.

On homogenization of the Landau–Lifshitz equation with rapidly oscillating material coefficient

In this paper, we consider homogenization of the Landau-Lifshitz equation with a highly oscillatory material coefficient with period e modeling a ferromagnetic composite. We derive equations for th ...

Lattice Phase Field Model for Nanomaterials.

The lattice phase field model is developed to simulate microstructures of nanoscale materials. The grid spacing in simulation is rescaled and restricted to the lattice parameter of real materials. Two possible approaches are used to solve the phase field equations at the length scale of lattice parameter. Examples for lattice phase field modeling of complex nanostructures are presented to demonstrate the potential and capability of this model, including ferroelectric superlattice structure, ferromagnetic composites, and the grain growth process under stress. Advantages, disadvantages, and future directions with this phase field model are discussed briefly.

Partial oxidation of high entropy alloys: A route toward nanostructured ferromagnets

The present work proposes a new approach to the development of nanostructured ferromagnetic composites based on progressive oxidation of high entropy alloys. Sequential ‘subtraction’ of the metals with the lowest oxidation energy destabilizes the remaining solid solution and induces phase separation at the nanoscale. By exploring immiscibility routes in the multidimensional phase diagrams, the strategy can be used to promote intimate contact between mixed oxides and metallic solid solutions with desired magnetic properties. To demonstrate the concept, the relation between oxidation energy, phase separation, and magnetic behavior has been investigated across the (CoCrCuFeNi)Ox composition space, for 0.1 ≤ x ≤1.3, in materials produced by reactive sputtering. The results point out directions for tuning the composition when aiming for phases with specific magnetic properties arranged in complex microstructures.

Microstructural Design of Necklace-Like Fe3O4/Multiwall Carbon Nanotube (MWCNT) Composites with Enhanced Microwave Absorption Performance

In order to manufacture microwave absorbers with strong attenuation abilities and that are light weight, in this paper, ferromagnetic carbon matrix composites were prepared by the composite of carbon nanotubes with adjustable dielectric constant and Fe3O4. Fe3O4/MWCNT composites with well-designed necklace-like structure and controllable size in the range of 100–400 nm have been successfully achieved by a simple solvent thermal method. A series of samples were prepared by changing experimental parameters. The microwave absorption characteristics of these samples were studied from the dielectric constant and magnetic permeability in two aspects. The electromagnetic absorption properties of the composites show obvious differences with different microsphere sizes, different microsphere density and different proportion of additives. When the solvothermal time is 15 h and the microsphere size is 400 nm, the reflection loss reaches −38 dB. The interfacial polarization caused by the unique structural design and good impedance matching produce composites that possess excellent electromagnetic loss ability.

Micromechanics-based simulation of anisotropic magneto-mechanical properties of magnetorheological elastomers with chained microstructures

Magnetorheological elastomers (MREs) are ferromagnetic particle-reinforced composites that have a wide application prospect in engineering because of their tunable stiffness with applied magnetic fields. While a large number of experimental efforts have been carried out to characterize the magneto-mechanical properties of MREs, few physics-based quantitative modeling and simulation have been explored. Here a micromechanics-based finite element model and computational homogenization is developed to determine the field-dependent shear moduli of MREs. The magneto-elastic coupling is realized with the magnetic field-induced body forces in the local mechanical field. The three-dimensional body forces are solved with consideration of magnetization and demagnetizing fields. Effects of essential microstructure parameters (particle concentration and particle spacing) are investigated on the effective magneto-mechanical properties of chain-structured MREs. The numerical results demonstrate that the microstructures and demagnetizing field have significant effects on the field-induced moduli of MREs. RVEs with appropriate microstructures are selected to compare our model predictions of magneto-mechanical properties with multiple groups of experiment data in the literature, showing the capability and validity of the proposed model.

Metallic ferromagnetic selenospinel composites of CuCr2Se4–CdCr2Se4 with double negative electromagnetic parameters

Random metamaterial with negative electric permittivity (ε < 0) and negative magnetic permeability (μ < 0) is a group of attractive alternatives to ordered double negative metamaterials (DNMs) with periodic unit cells; however, the preparation of random DNMs with a relatively convenient preparation process and their electromagnetic property adjustment are of challenge. Here, we report the preparation of metallic ferromagnetic selenospinel composites, xCdCr2Se4·(1−x)CuCr2Se4, from metallic powders by using a simple solid-state reaction process, and double negative ε and μ have been observed in the frequency range of 120–650 MHz for 0.2CdCr2Se4·0.8CuCr2Se4 and 73–520 MHz for 0.4CdCr2Se4·0.6CuCr2Se4. The negative ε is owing to the plasmonic state of delocalized carriers in the metallic ferromagnetic CuCr2Se4, which can be described with the Drude model. The suppression of the magnetic resonance induced by the eddy current has been alleviated by the proper addition of the paramagnetic semiconductor CdCr2Se4. A theoretical model deduced from Maxwell's equation has been constructed based on the skin effect to elucidate the magnetic resonance-dependent negative permeability. Our work introduces the metallic ferromagnetic chalcospinels into the field of random DNMs and sheds light on the theoretical understanding and tuning mechanism on the double negative properties.

Reconfigurable Three‐Dimensional Mesotructures of Spatially Programmed Liquid Crystal Elastomers and Their Ferromagnetic Composites

AbstractReversible programming of 3D soft mesostructures is desired for many applications including soft robotics and biomedical devices. The large, reversible shape changes of liquid crystal elastomers (LCEs), which result from the coupling between the alignment of liquid crystal (LC) molecules and the macroscopic deformation of polymer networks, have attracted much attention for such applications. Here, a facile and versatile strategy is introduced to create reconfigurable, freestanding 3D mesostructures of LCEs and magnetic LCE composites that are inaccessible with existing techniques via spatially programming LC molecules through mechanical buckling. Demonstrations include experimental and theoretical results of more than 20 reconfigurable 3D LCE mesostructures of diverse configurations, from coils and spirals to structures that resemble fences and frameworks, with characteristic feature sizes and thicknesses ranging from micro to macro. The large, reversible shape‐switching behaviors of these structures over multiple cycles are also demonstrated. An LCE gripper is shown to grab/release objects of both regular and irregular geometries. Furthermore, a robot of ferromagnetic LCE composites that simultaneously responds to magnetic and thermal stimuli for diverse biomimetic behaviors, especially crawling underneath a narrow crack, illustrates the integration of other functional materials to LCEs for multifunctional systems.

Large and sensitive magnetostriction in ferromagnetic composites with nanodispersive precipitates

Large and sensitive magnetostriction (large strain induced by small magnetic fields) is highly desired for applications of magnetostrictive materials. However, it is difficult to simultaneously improve magnetostriction and reduce the switching field because magnetostriction and the switching field are both proportional to the magnetocrystalline anisotropy. To solve this fundamental challenge, we report that introducing tetragonal nanoprecipitates into a cubic matrix can facilitate large and sensitive magnetostriction even in random polycrystals. As exhibited in a proof-of-principle reference, Fe–Ga alloys, the figure of merit—defined by the saturation magnetostriction over the magnetocrystalline anisotropy constant—can be enhanced by over 5-fold through optimum aging of the solution-treated precursor. On the one hand, the aging-induced nanodispersive face-centered tetragonal (FCT) precipitates create local tetragonal distortion of the body-centered cubic (BCC) matrix, substantially enhancing the saturation magnetostriction to be comparable to that of single crystal materials. On the other hand, these precipitates randomly couple with the matrix at the nanoscale, resulting in the collapse of net magnetocrystalline anisotropy. Our findings not only provide a simple and feasible approach to enhance the magnetostriction performance of random polycrystalline ferromagnets but also provide important insights toward understanding the mechanism of heterogeneous magnetostriction.