Magnetic Properties Of Composites Research Articles

Preparation and Magnetic Properties of Low-Loss Soft Magnetic Composites Using MgO-Phenolic Resin Coating.

Optimizing the interface between a magnetic powder matrix and an oxide-insulating layer is an effective method to improve the permeability and lower eddy current loss of iron-based soft magnetic composites. In this study, in order to improve the bonding strength of the substrate and insulation layer, soft magnetic composites were prepared by pressing and heat treating with reduced iron powder as a magnetic matrix, high-temperature MgO nanoparticles as insulating coating, and phenolic resin as an adhesive. The effects of MgO content on the microstructure and magnetic properties of the composites were investigated. The results of a scanning electron microscopy and an energy-dispersive spectrometer analysis corroborate that the results obtained regarding the frequency characteristics and the resistivity of the iron powder agree with the scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) analysis and confirm their improvement by the presence of an insulating layer of MgO. The resistivity of the sample coated with 4 wt.% MgO is nearly 45 times higher than that of the uncoated sample under the same conditions. The MgO-insulating film formed on the surface of iron powder makes the coated sample have low effective grain size, high resistivity, and low magnetic loss at a high frequency. At 1 kHz, the magnetic loss of the 4 wt.% MgO-coated sample is reduced by 77.3%, and the magnetic loss is only 5.8% compared with the uncoated sample at 50 kHz. This magnetic loss separation study shows that the addition of MgO insulation material can effectively reduce the eddy current loss of the magnetic powder core. The 4 wt.% MgO-coated sample has the lowest hysteresis loss factor and relatively low eddy current loss factor, so it can be determined that the addition of 4 wt.% MgO is the optimum content to attain a low magnetic loss.

4D printing of magneto-responsive polymer structures by masked stereolithography for miniaturised actuators

ABSTRACT Masked stereolithography printing can be used to produce functionalised magneto-responsive polymer structures. Magnetic filler additivation of the photopolymer enables the production of powerful and fast soft robotics. However, current approaches require high filler concentrations, reducing the mechanical properties and compromising the processability. In this study, FeNi nanoparticles were added to a photopolymer to take advantage of their soft magnetic response and high magnetisation. Field-assisted printing gives rise to magnetic anisotropy by arranging laser-synthesised FeNi nanoparticles into uniaxial magnetic strands of up to 500 μm length. Favoured by the small size and even distribution of the nanoparticles, only 0.02 wt% are needed to detect magnetic responsivity. Thus, the impact on the mechanical property is reduced while facilitating the control over the composite magnetic properties. The practical feasibility of the composites is demonstrated by actuating gripper and impeller structures which offer possibilities in applications like drug delivery and tissue engineering.

Tailoring the Magnetic and Electrical Properties of Epoxy Composites Containing Olive-Derived Biochar through Iron Modification.

The combination of conductive carbon together with magnetic particles is a consolidated strategy to produce cutting-edge fillers for the production of polymer composites able to shield against microwave radiation. In this work, we developed and characterized an iron-tailored biochar obtained from the pyrolysis of olive pruning which was added as filler for the preparation of epoxy composites. The biochar-based composites were obtained by keeping the filler concentration at 10 and 40 wt.%. An extensive characterization was carried out in order to assess the electrical and magnetic properties of the composites containing biochar and iron-tailored biochar. The highest DC electrical conductivity of 59 mS/m was observed in the 40 wt.% iron-tailored biochar-loaded composite, while the reduction of the filler loading led to a drastic reduction in conductivity: 60 μS/m in the 10 wt.%-loaded composite. Ferromagnetic behavior of composites containing iron-tailored biochar is visible in the emerging hysteretic behavior, with a magnetic signal increasing with the filler concentration. Finally, both the complex permittivity (ε') and the AC conductivity (σ) are enhanced by increasing the BC filler amount in the matrix, regardless of the presence of iron.

Interplay between thermal and magnetic properties of polymer nanocomposites with superparamagnetic Fe3O4 nanoparticles

Magnetic nanoparticles embedded in polymer matrices have excellent potential for multifunctional applications like magnetic remote heating, controlled drug delivery, hyperthermia, and thermally functionalized biomedical devices. A solvent-based processing method was developed to produce magnetic composites consisting of magnetite (Fe3O4) superparamagnetic nanoparticles embedded in a biomedical-grade polyurethane (ChronoFlex® C). The particles had a log-normal size distribution spanning from 4−16 nm, with a mean-size of 9.5 ± 2 nm. X-ray diffraction, transmission electron microscopy, and scanning electron microscopy with elemental mapping were used to assess the phase purity, surface morphology, particle size, and homogeneity of the resulting nanocomposite. The magnetic properties of composites with 7–13 wt% of Fe3O4 were studied between 5 and 300 K using vibrating sample magnetometry. Room temperature magnetic attraction was observed, with a saturation magnetization of up to 5 emu/g and a low coercive field (Hc < 50 Oe), where the non-zero coercive field was attributed to a small fraction of larger particles that are ferromagnetic at room temperature. Field-cooled and zero-field-cooled magnetometry data were fitted to a numerical model to determine the superparamagnetic mean blocking temperature (TB = 90 K) of the embedded magnetite particles, and an effective magnetic anisotropy of 6×105 erg/cm3. Using an AC magnetic field operating at 85 kHz, we demonstrate that remote heating of the base polyurethane material is greatly enhanced by compositing with Fe3O4 nanoparticles, leading to temperatures up to 45 °C within 18 min for composites submerged in water. This work demonstrates the fundamental principles of a custom-designed thermomagnetic polymer composite that could be used in applications, including medical and heat management.

Evaluation of Equivalent Permeability of Soft Magnetic Composites Considering Manufacturing Process

A method for evaluating the equivalent permeability of soft magnetic composites is presented. Firstly, a new microstructural characterization model of soft magnetic composites is proposed, which introduces the concepts of pores and gaps. The effect of these two structures on the magnetic properties of composites is analyzed, and an analytical model is derived from the microstructural parameters. Secondly, the compaction process is numerically simulated by discrete element method and powder particle 3D reconstruction technique. The microstructure models of soft magnetic composites under different compaction conditions are established. Finally, the magnetic field characteristics of the microstructure model are analyzed by finite element method, and the equivalent permeability is accurately evaluated. The correctness and feasibility of the simulation method proposed in this paper is verified by comparing with the measured results.

Sterculia lychnophora seed-derived porous carbon@CoFe2O4 composites with efficient microwave absorption performance

Recently, biomass-derived porous carbon materials demonstrate great potential to develop high-efficient microwave absorbers. Herein, magnetic porous composites consisting of CoFe2O4 nanoparticles and biomass-derived carbon from sterculia lychnophora seeds are prepared via hydrothermal and pyrolysis methods. The dielectric and magnetic properties of composites are modulated by tuning the content of CoFe2O4 nanoparticles to optimize impedance matching characteristics and improve attenuation capabilities. Benefitting from multicomponent compositions and porous structures, the optimized composite exhibits superior microwave absorption performance with the minimum reflection loss value of −67.04 dB at 2.0 mm and an effective absorption bandwidth of 5.52 GHz (11.92–17.44 GHz) at the filler loading of 20 wt%. Besides, the composite achieves strong microwave absorption in multiband (3.92–18 GHz) by adjusting matching thickness. The outstanding microwave absorption properties of magnetic porous composites are attributed to the synergistic effect of interfacial polarization, dipolar polarization, conductive loss, magnetic loss, multiple reflection and scattering of incident microwaves. This work could provide references for the advanced development of biomass-derived porous microwave absorbers.

Investigation of Magnetic Properties of Poly Vinyl Chloride Composites Prepared Using Different Ratios of Fe2O3 (Maghemite) Nanoparticles

Composites were prepared using polyvinyl chloride (PVC) and different percentages of Fe2O3 nanoparticles. All composites were characterized by FT-IR spectroscopy. Then, the thermal properties of the composites prepared in 1% and 10% ratios were examined. It was observed that the initial decomposition temperature (Ti) values of PVC composites prepared with Fe2O3 nanoparticles addition were lower than pure PVC. Magnetic properties of composites were examined with a vibrating sample magnetometer (VSM). The saturation magnetization values of PVC composites prepared by using 1% and 10% Fe2O3 were 2.77 and 7.06 emu / g, respectively.

Graphitization of flax shive cellulose modified by citric acid: properties of magnetic composites and their dye adsorption capacity

Magnetic composites were synthesized in an inert medium within the temperature range T = 500–1000 °C by one-stage pyrolysis of microcrystalline flax shive cellulose modified by citric acid (MCCA) and homogeneously impregnated with Fe(NO3)3. Catalytic graphitization was studied by the thermogravimetric analysis method. The crystal structure, pore development, morphological structure and surface chemistry of carbon composites were characterized by the N2 adsorption-desorption, XRD, SEM and FTIR methods. The onset temperature of MCCA graphitization was found to be equal to 600 °C. The magnetic carbon materials were tested as adsorbents for removal of anionic methyl orange (MO) and cationic methylene blue (MB) dyes. The highest equilibrium adsorption capacity in MB and MO was found in the magnetic composites synthesized at 700 and 800 °C.

Development of emphatic catalysts for waste water remediation via synchronized free radical and non-free radical routes with composites of strontium hexaferrite, graphene and multi-walled carbon nanotubes

Magnetic nanoparticles have shown exceptional potential in catalysis, however, their tendency to agglomerate has confined their use. The present work encompasses synthesis of eco-friendly and magnetic retrievable catalysts with different fractions of reduced graphene oxide (rGO) and multiwalled carbon nanotubes (MWCNT) as support for strontium hexaferrite (SrFe12O19) for the oxidative degradation of organic pollutants. The morphological, structural and magnetic properties of composites were estimated via PXRD, FT-IR, VSM, FE-SEM, HR-TEM, XPS and BET. The crystallite size decreased from 41.46 nm for SrFe12O19 to 35.85 nm and 33 nm for composites with 20% rGO and MWCNTs, respectively while the surface area increased substantially from 88.1 m2/g for SrFe12O19 to 118.4 and 131.3 m2/g. Further, the composites were employed as catalysts for the oxidative degradation of selected antibiotics and colourant via stimulation of two different oxidants, potassium peroxymonosulphate (PMS) and hydrogen peroxide (H2O2). The degradation followed pseudo first order kinetics with rate constant values increasing with rGO and MWCNT content. The increase in catalyst effectiveness can be ascribed to the synergistic interactions between rGO or MWCNT and SrFe12O19, which provided larger specific surface areas for adsorption and augmented number of catalytically active sites. Systematic chemical quenching studies unveiled a combined role of radical and non-radical species in oxidative degradation of pollutants. Moreover, the synthesized composites exhibited excellent recyclability upto four cycles forming the basis for their utilization as industrial catalysts.

Novel chemical route for synthesis of CeO2–ZnO nanocomposite towards high electrochemical supercapacitor application

Herein, CeO2–ZnO nanocomposite was synthesized by a simple chemical precipitation method. The crystallite size and structure of composite were investigated using X-ray diffraction spectroscopy (XRD). The morphology and actual size of nanocomposite are determined using scanning electron microscopy (SEM) and high-resolution electron microscopy (HR-TEM), revealing mono-dispersed spherical-shaped articles with size of ~ 5 nm. Optical and magnetic properties of composite were examined by UV–Vis, PL and EPR studies. The electrochemical supercapacitor performance of CeO2–ZnO nanocomposite was employed by cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) and impedance spectroscopy (EIS). The highest specific capacitance of 424 Fg−1 at scan rate of 5 mVs−1 from CV and 377 Fg−1 at current density of 1 Ag−1 from GCD was achieved. High capacitance retention of 94.6% was attained at the current density of 1 Ag−1. This work demonstrates that good reversibility, better rate capability and long-term stability of CeO2–ZnO composite electrode were applicable in wide-range potential applications.

Synthesis and Characterization of Fe3O4 Composites Embeded on Coconut Shell Activated Carbon

&lt;p&gt;Synthesis and characterization of Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;-coconut shell activated carbon composites has been carried out to create a magnetic adsorbents. Composites were synthesized using the coprecipitation reflux method by mixing a solution of Fe&lt;sup&gt;3+&lt;/sup&gt;/Fe&lt;sup&gt;2+&lt;/sup&gt; iron salt (mol ratio 2:1) and suspension of activated carbon in water followed by the addition of NaOH solution. The structure, functional groups, morphology and surface area of the composites were characterized using FTIR, XRD, SEM and GSA. The magnetic properties of composites are tested by response to magnetic fields. The characterization results showed that the embedment of Fe&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; on coconut shell activated carbon was successfully carried out through the interaction of hydroxyl groups at wave numbers 601.79 and 416.62 cm&lt;sup&gt;-1&lt;/sup&gt;. Diffraction peaks at 2θ 30.12° [220], 35.58° [311], 43.14° [400], 53.57° [422], 57.18° [511] and 62.83° [440] indicate the existence magnetite sized of 11.72 nm. Activated carbon has an average pore size of micropores with an average pore of 1.46 nm. Magnetite embedment reduced the surface area of activated carbon from 91.16 m&lt;sup&gt;2&lt;/sup&gt;/g to 12.04 m&lt;sup&gt;2&lt;/sup&gt;/g. The response of sample to the magnetic field indicates that composite has magnetic properties.&lt;/p&gt;

Low temperature magnetic properties and electromagnetic interference shielding effectiveness of PDMS composites

This paper presents the preparation and characterization of Polydimethylsiloxane (PDMS) composites with Carbon encapsulated iron nano particles (CEFeNPs). The mutual interactions between the CEFeNPs and PDMS were studied by Raman Spectroscopy and Scanning electron microscopy. Structural characterization on the flexible composite films and CEFeNPs was carried out using X-ray diffractometer. Transmission electron microscopy (TEM) revealed the structure of CEFeNPs, with an iron core enveloped by 5 nm thick layer of graphitic carbon. The main goal of this work was to investigate the influence of temperature on magnetic properties of composites by applying a magnetic field ranging from −1.5 to 1.5 Tesla at 10 K, 100 K and 300 K. The saturation magnetization, retentivity, coercivity and squareness ratio found to improve with increase in filler loading and by lowering temperature. For 50 wt% composite of 250 μm thickness, the electromagnetic interference shielding effectiveness (EMI SE) is found to be 21.925 dB at 8 GHz. The shielding performance of cured composites enhanced by increasing the thickness of the sample and for 1.5 mm thick film of 50 wt%, an EMI SE of 27.1 dB was obtained at 8 GHz.

Synthesis, characterization of Fe3O4@SiO2@ZnO composite with a core-shell structure and evaluation of its photocatalytic activity

Abstract The Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2@ZnO composites that can be magnetically separated were synthesized using hydrothermal and sol-gel methods. SEM-EDS, ICP-AES, TEM, XRD, FT-IR, UV–vis, VSM, and XPS analyzes were used for the characterization of the composites. With TEM and SEM results, it has been determined that the average diameters of the Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2@ZnO composites are 210, 220 and 230 nm, respectively, and the composites have a spherical structure and homogeneous distribution. The weight percentage of the composites were determined by the ICP-AES analysis. The XRD analysis determined that the crystal structures of the composites are compatible with the standard diffraction data cards. The average particle diameters of composites were calculated using the formula of Debye-Scherrer, and similar results were obtained with the diameters determined by TEM and SEM results. The properties of bond structures of composites were determined by the results of FT-IR analysis. The bandgap energies of Fe3O4, Fe3O4@SiO2, Fe3O4SiO2@ZnO were calculated by the Tauc method using the UV–vis measurement results and found as 1.3, 1.68, and 2.21 eV, respectively. The magnetic properties of composites were determined by VSM analysis. Acid Blue 161 solution was used to evaluate the photocatalytic activities of the produced photocatalyst composites. The experiments carried out in the dark medium revealed that the decomposition of Acid Blue 161 was not due to adsorption. In the experiments performed in the presence of Fe3O4 and Fe3O4@SiO2 composites, the photocatalytic activity was found to be very low. Compared with Fe3O4@SiO2@ZnO composite and commercial ZnO nanoparticles, which show the highest photocatalytic activity, Fe3O4@SiO2@ZnO composite has achieved 100 % the decomposition of Acid Blue 161 within 120 min, while the dye decomposition of ZnO nanoparticles is 70.9 %. The results revealed that the Fe3O4@SiO2@ZnO composite has an effective photocatalytic activity.

Preparation of Magnetic Composites Based on Bulk Amorphous Iron Alloys

Iron-based amorphous alloys are characterized by so-called soft magnetic properties. Unfortunately, the geometry of iron-based amorphous materials significantly limits the applicability of these materials. One way to expand the use of these materials is to make composites based on them. As part of this work, rapid-cooled alloys were produced using the injection casting method. On their basis, magnetic composites with the addition of a non-magnetic binder were produced. The results of the structure (XRD) and magnetic properties (VSM) tests of the produced materials are presented. The research results have shown that the decisive impact on the magnetic properties of composites is the fact of the separation of magnetic particles with a non-magnetic binder. In this case, the influence of exchange interactions is dominated by dipole interactions.

Structure and magnetic properties of Fe-based soft magnetic composites with an Li–Al–O insulation layer obtained by hydrothermal synthesis

In this paper, Fe-based soft magnetic composites (SMCs) hydrothermally coated with lithium aluminum oxide (Li–Al–O) with better magnetic properties and lower core losses than Al2O3 coated layers have be investigated. The microstructure and composition of the coating and magnetic properties of the composites were determined by scanning electron microscopy (SEM), X-ray diffraction (XRD) and B–H curve analyzer. Those results revealed that when Li2CO3 was added to the aluminum nitrate solution, the originally formed Al2O3 coating layer converted to a layer with a mixture of several lithium aluminum oxides. Fe-based SMCs coated with lithium aluminum oxide showed lower core losses, higher and stable effective permeability as compared with iron rings coated with Al2O3, especially in high frequency range of 100–300 kHz.

Theoretical method for calculation of effective properties of composite materials with reconfigurable microstructure: Electric and magnetic phenomena

We propose a theoretical approach for calculating effective electric and magnetic properties of composites, with field dependent restructuring of the filler. The theory combines the effective medium approximation, extended to a field-dependent (variable) percolation threshold, with an approximate treatment of the nonlinearity of material properties. Theoretical results are compared with experiments on magnetorheological elastomers, which in the context of investigated phenomena are often called magnetoactive elastomers (MAEs). In MAEs with soft polymer matrices, the mutual arrangement of inclusions changes in an applied magnetic field. This reorganization of the microstructure leads to unconventionally large changes of electrical and magnetic properties. The obtained theoretical results describe observed phenomena in MAEs well. For the magnetodielectric effect, qualitative agreement between theory and experiment is demonstrated. In the case of magnetic permeability, quantitative agreement is achieved. The theoretical approach presented can be useful for the development of field-controlled smart materials and design of intelligent structures on their basis, because the field dependence of physical properties can be predicted.

Analysis of adsorption properties of magnetic composites: preparation of multi-walled carbon nanotubes

Analysis of adsorption properties of magnetic composites: preparation of multi-walled carbon nanotubes

The effects of Fe nano-powders on compaction behaviors and magnetic properties of SMCs

Abstract Currently, metallic soft magnetic composites, due to their high saturation magnetization, have attracted much attention for application in high frequency mobile devices. These composites must approach a full densification to achieve the high permeability and magnetic flux density necessary for mobile device applications. This study was carried out to investigate the effects of Fe nano-powders on the compaction behaviors and magnetic properties of Fe-Si alloy composites. Fe-Si micro-powders were fabricated using a gas-atomizer; then, SiO2 was coated on them to suppress eddy current loss. Fe-nano-powders were obtained using spray-dried Fe2O3 powders. These nano-powders were homogeneously mixed with Fe-Si micro-powders to increase the density of the compacts. As a result, the composite with 80 wt% micro-powders showed excellent high frequency properties due to high compaction density. Microstructural analysis shows that changes in the magnetic properties of the composites are dependent on the fill factor and electrical path-ways of non-insulated nano-powders in pores between insulated micro-powders.

Synthesis and Characterization of Electromagnetic Material Based On Composite of Barium M-Ferrite and Zinc Oxide

The making of composites BaFe12O19/ZnO has been done with Wet Milling method used media toluene. Barium M-Ferrit as a matrix and Zinc Oxide as a filler used as the main raw material for composite manufacturing. The milling process of Barium M-Ferrit was done for 12 hours using the High Energy Milling (HEM). Furthermore, the calcination process used furnace at 900 ° C for 4 hours. While Zinc Oxide is milled for 3 hours and calcined at a temperature of 500 oC for 3 hours. The results of Barium M-Ferrit and zinc Oxide mixed using wet milling touluene media for 15 minutes and dried for 1 hour at 200 oC. X-ray diffraction (XRD) showed that BaFe12O19 as a matrix and ZnO as filler with hexagonal crystal structure was formed and the peak showed a single phase, where each BaFe12O19 lattice parameter a = 5.8930 Å, c = 23.1940 Å and ZnO lattice parameter a = 3.2533 Å, c = 5.2073 Å. Characterization Vibrating Sample Magnetometer (VSM) obtained the value of magnetic properties BaFe12O19 powder (matrix) obtained (Ms) magnetic saturation 54.03 emu/g, (Mr) magnet remanent 33.06 emu/g, (Hcj) coercivity 2943 Oe and (BHmax) product energy 190 kGOe and Zinc Oxide as filler values (Ms) magnet saturation 7.84 emu / g, (Mr) magnet remanent 1.27 emu/g, (Hcj) coercivity 152.4 Oe and (BHmax) energy products 10 kGOe. The results of XRD on 50% mass of composites ZnO additions using match software have two phases, namely the presence of ZnO and BaFe12O19 phases which indicate that heterogeneous structures with hexagonal crystal structures. Composite magnetic properties obtained by adding 50% mass of ZnO were (Mr) magnet 39.40 emu/ g, coercivity 2728 Oe, (BHmax) product energy 110 kGOe and for composites 75% mass addition ZnO remanent 39.36 emu/g with coefficient of 1365 Oe and ( BHmax) product energy was 60 kGOe.

Dielectric, magnetic and magnetoelectric properties of ferrite-ferroelectric based particulate composites

Particulate composites based on ferrite and ferroelectric phase viz. cobalt zinc ferrite (Co0.8Zn0.2Fe2O4) and bismuth sodium titanate (Bi0.5Na0.5TiO3) were synthesized using solid state reaction method. The formation of diphase composite was established using x-ray diffraction. Field emission scanning electron microscopy was used to study the microstructure of the composites, exhibiting fine blending of constituent phases in the composites. Dielectric behaviour of the composites was studied as a function of temperature and frequency. Variation of dielectric constant with temperature exhibits a shift in Curie temperature with increase in ferrite content. Usual dielectric dispersion is observed for the composites with increase in frequency. The consequence of addition of ferrite phase on ferroelectric and magnetic properties of composites was studied. All composites exhibit typical ferromagnetic hysteresis loops. Magnetoelctric coupling in the composites was confirmed by measuring magnetoelctric voltage coefficient (αME). The maximum αME of 7.11 mV cm−1-Oe was obtained for 10% Co0.8Zn0.2Fe2O4—90% Bi0.5Na0.5TiO3 composite.