Search

Currently, the requirements of excellent comprehensive properties and high economic returns for microwave absorbers remain severe challenges for practical application of these materials. Herein, a composite of carbonyl iron particles (CIP) and bio-derived carbon was synthesized for microwave absorption for the first time. Brine shrimp egg shells (BSES) were chosen as the carbon precursor because the innate multilayer porous structure favours enhancing the microwave absorbing (MA) performance by inducing geometrical effect. Not only does the as-fabricated CIP/C composite exhibit outstanding MA properties, but the method is also facile and eco-friendly. Owing to the unique layered porous structure of BSES-derived carbon, well-matched complex permittivity and permeability together with the synergy of dielectric and magnetic loss, the composite displayed a remarkable reflection loss of − 55.4 dB at 13.0 GHz and a broad effective absorption bandwidth of 5.0 GHz with a thickness of only 1.5 mm, which is superior to those of most reported Fe/C composites, especially in thickness and effective absorption bandwidth. Hence, there are reasons to believe that the as-prepared CIP/C composite may have a bright prospect for practical application in civilian life and industry as an efficient MA material.

Flaky carbonyl iron particles/nano silicon dioxide/Polyurethane (FCIP/SiO2/PU) composites coatings were fabricated. And FCIP were fabricated from sphere carbonyl iron particles (SCIP) by ball milling. The electromagnetic parameters of absorbers (SCIP, FCIP and SiO2) and the reflection loss (RL) of coatings were measured in the frequency range of 2–18 GHz. The results showed that the complex permeability and absorbing properties of FCIP are significantly enhanced compared with SCIP because of its smaller thickness and easy magnetization plane. In addition, as a low dielectric material, SiO2 can build more wave-transmission channels and optimize the impedance matching, making more electromagnetic wave transmitting into the coatings and being attenuated. Due to the addition of SiO2, the absorbing properties and effective absorption bandwidth of coatings are further enhanced. The reflection loss values exceeding − 10 dB can be obtained in the frequency range of 8.5–18 GHz with a thickness of 1 mm.

FeCoNi-coated PMMA (FeCoNi@PMMA) core-shell structures prepared by an electroless plating process were investigated in this study. Further, we fabricated FeCoNi@PMMA in polydimethylsiloxane sheets with volume fractions of fillers from 10 vol% to 25 vol% to evaluate electromagnetic wave absorption performance. Subsequently, results were compared with those of carbonyl iron particles (CIP). The maximum reflection loss (RL) of FeCoNi@PMMA composite (25 vol%) reached a value of −37.2 dB at 12.2 GHz with a thickness of 1.5 mm and a broad absorption bandwidth (RL ≤ −10 dB) of 4.5 GHz, attributed to strong dielectric and magnetic losses. Though the microwave absorption performance of the core-shell structured FeCoNi@PMMA composites is similar to that of CIP composites, the weight fraction of FeCoNi@PMMA is reduced about 38% compared with CIP with the same volume fraction (25 vol%). These results indicate that FeCoNi@PMMA is a lightweight material and a good candidate for high-performance microwave-absorbing devices.

In the present work, a continuum-based material model has been developed for an isotropic magneto-active elastomer (MAE) to investigate its behavior under small deformations. Firstly, the governing magneto-mechanical equations are formulated for the flexible magneto-active medium. Subsequently, a linearization scheme is used to construct constitutive equations for the small-deformation analysis of MAEs by expressing the magnetic parameters by two constituents involving the rigid-body and perturbation states. The material constants of the constitutive model are estimated from the experiments performed on a right cylindrical sample of a magneto-active material comprising the elastic matrix with 15% volume fraction of carbonyl iron particles.

An effective solution for corrosion protection of metallic carbonyl iron (CI) substrates in strong saline environment (3 M KCl) is demonstrated in this work. A thin layer coating of graphene oxide ...

Magnetorheological (MR) gels belong to a group of smart materials whose attributes can be altered when it is exposed to an external magnetic field. In this paper, the investigation on the creep beh...

A hybrid composite based on 30 wt.% and 50 wt.% of MnZn ferrite and Carbonyl Iron (CI) with 1 wt.% of carbon nanotube (CNT) dispersed on silicone rubber was produced to investigate the electromagnetic absorption performance on X Band frequency range (8.2–12.4 GHz). The MnZn ferrite, CI and CNT powder were characterized by Scanning Electron Microscope (SEM) to analyze the pallet morphology. The influence of the CNT on magnetic composites was studied by comparison with MnZn ferrite and CI composites on the electrical and magnetic properties using a rectangular waveguide based on the Nicholson-Ross-Weiner model. On the MnZn ferrite structure, the CNT increased the magnetic storage capability and reduced its property in CI composite. The Reflection Loss demonstrates the increases in absorption due to the CNT link between magnetic pallets. MnZn ferrite with CNT showed a minimum RL value of −21 dB with 2.3 mm of thickness. The hybrid composite demonstrated a better electromagnetic performance than the composite with the same weight% of the magnetic pallet, which is very interesting to the aerospace and aeronautic applications that require a high electromagnetic absorption and lightweight. Keywords: Hybrid composite, MnZn ferrite, Carbonyl iron, Carbon nanotube, Electromagnetic characterization

This article discusses the influence of carbonyl iron powder, grade VK, on compactability, sintering, and mechanical properties of samples made of atomized iron powder, grade PZhRV 2.200.26, produced on commercial scale in Russia. It is demonstrated that the relative density of compacted samples made of dispersed PZhRV 2.200.26 iron powder can be increased by addition of particles of carbonyl iron powder, grade VK, which are predominantly located in pores between the particles of atomized powder. Additional introduction of solid lubricants in PZhRV 2.200.26 and VK mixture does not lead to further increase in relative density of pressed samples (more than 90%). It is established that addition of the VK carbonyl powder to the atomized PZhRV 2.200.26 powder in the amount of 15–20 wt % atomized the bending strength of green compacted pieces because of difficulties of plastic deformation of atomized particles into pores, but it increases the bending strength of the material after sintering owing to more developed contacts.

The present paper deals with the development of dense Fe–Ag and Fe–Cu high-strength nanocomposites from blends of nanocomposite powders employing cold sintering (high-pressure consolidation). Nanocomposite powders were obtained by high-energy attrition milling of micron-scale powder of carbonyl iron (Fe) and nanosized silver oxide powder (Ag2O) as well as of nanopowders of Fe and cuprous oxide (Cu2O). Phase identification was done by X-ray diffraction. Microstructure was viewed in a high-resolution scanning electron microscope. Compacts with ~70% theoretical density were annealed in hydrogen to reduce silver and cuprous oxides to metals and to remove oxide layers from the powder particle surface. This was followed by cold sintering, i.e. consolidation in a high-pressure gradient at ambient temperature. The obtained data on the specimen density were analyzed depending on the applied pressure in the range 0.25–3.00 GPa. At the pressure 3.00 GPa, all the nanocomposites are sintered to more than 95% theoretical density. The compositions demonstrate high mechanical properties in three-point bending and compression. The nanocomposites were found to have substantially higher mechanical properties as compared to composites with micron-scale grains. It was revealed that Fe–Ag and Fe–Cu nanocomposites have a higher ductility as compared to nanostructured Fe, which is due to more plastic Ag and Cu phases in the nanocomposites as compared to the Fe phase. It was shown that loading of antibiotic Vancomycin into the interconnected nanopore system of cold-sintered nanocomposites results in nanoencapsulation of the drug and its slow release from the nanocomposite.

Silicone-based Magnetorheological Fluids (MRFs) were prepared with 10% volume fraction of carbonyl iron powder. Rheometer Physica MCR 301 was used to test the rheological performances of MRFs.The experimental results show Bingham model and Casson model could well describe rheological behaviors of MRFs. Shear stress of MRFs increases but apparent viscosity is significantly decreased and tends to be stable with the increase of shear rate in the presence of magnetic field. The results also show that MRFs are shear thinning fluids. The dependence of shear stress on magnetic field was tested under the condition of constant shear rate and increasing magnetic field, shear stress of MRFs increases remarkably.

In this work, an epoxy-based microwave absorbing coating (MAC) containing carbon nanotube (CNT), silicon carbide (SiC), and carbonyl iron (CI) particles was prepared. In order to achieve some optimum key properties such as high and broadband microwave absorbing properties, low density, and relatively low cost, a gradient structure and alternating multilayer structure are used simultaneously. The effect of a single layer containing one type of filler, single layer containing several types of fillers, and multilayer structures on mentioned key parameters are investigated. The electromagnetic parameters and the reflection loss (RL) versus frequency of samples were tested by network analyzer in the range of 2–18 GHz using the transmission/reflection method. As a final result, the multilayer MACs included nine layers in which each of the layers contained one type of the fillers (CNT, CI, and SiC) and three neat resin interlayers 2 mm in total thickness compared to other samples and provided a maximum return loss value of 17.6 dB at 08.50 GHz and an absorption bandwidth (RL

Magnetic microwave absorbing materials (MMAMs) possess many desirable properties, including thin thickness and wide attenuation band, and thus are widely applied in many fields. However, the mechanisms of variation in performance of MMAMs at dynamic temperature are difficult to characterize and poorly understood. In this work, we combine experiments and fluctuation-induced tunneling (FIT) simulations to delineate the effects of temperature on the microwave absorption properties of MMAMs. We find that the increase in temperature weakens the complex permeability of the carbonyl iron particles (CIPs)/epoxy coating, while also strengthening the complex permittivity. FIT simulations explain the experimental observations by showing that the tunneling current between two CIPs with a gap of a few nanometers increases with increasing temperature. Furthermore, crescendo conductance loss and decrescendo magnetic loss form an electric-magnetic complementary effect, so that the coating exhibits superior microwave absorption performance (maximum effective bandwidth 8 GHz) in the temperature range of 293 K–573 K, a result with implications for the broad understanding and design of MMAMs applied at high temperatures.

This work introduces a novel design of a fixture to be adapted to the commercial version of the capillary breakup extensional rheometer (CaBER), here termed as an extensional magneto-rheological fixture (ExMRFx), that allows the characterization of magnetic fluids under uniaxial extensional flow. The fixture consists of four solenoids that generate a homogeneous magnetic field with a tunable intensity on the fluid sample, while characterized in the CaBER under uniaxial extensional flow. The ExMRFx is designed in two configurations, one to impose a magnetic field parallel, while the other to impose a magnetic field perpendicular to the deformation axis. As an example of possible application, the ExMRFx has been tested with a magnetorheological fluid (MRF) consisting of a suspension of carbonyl iron particles dispersed in glycerine. The experimental results show that the filament thinning process of the MRF sample is influenced by the concentration of carbonyl iron particles used, the orientation of the magnetic field (parallel or perpendicular), the intensity of the magnetic field applied, and finally the Hencky strain imposed. Depending on the combination of these latter parameters, the MRF sample may result in a very stable filament bridging the two measuring plates, which will remain stable, as long as none of the experimental parameters change.This work introduces a novel design of a fixture to be adapted to the commercial version of the capillary breakup extensional rheometer (CaBER), here termed as an extensional magneto-rheological fixture (ExMRFx), that allows the characterization of magnetic fluids under uniaxial extensional flow. The fixture consists of four solenoids that generate a homogeneous magnetic field with a tunable intensity on the fluid sample, while characterized in the CaBER under uniaxial extensional flow. The ExMRFx is designed in two configurations, one to impose a magnetic field parallel, while the other to impose a magnetic field perpendicular to the deformation axis. As an example of possible application, the ExMRFx has been tested with a magnetorheological fluid (MRF) consisting of a suspension of carbonyl iron particles dispersed in glycerine. The experimental results show that the filament thinning process of the MRF sample is influenced by the concentration of carbonyl iron particles used, the orientation of the mag...

Smart materials such as Magnetorheological Fluids (MRF) have become sought-after material in wide ranging applications due to the ability to change properties in a controlled manner under application of stimulation such as a variable current, magnetization, heat, force, stress and deformation. Magnetorheological fluids in the rheological fluid domain has found use due to its ability to change its shear strength based on the applied magnetic field. Magnetorheological fluids are composed of magnetizable micron sized iron particles and a non-magnetizable base/ carrier fluid. The shear strength of commercially available MRF varies from 0 to 100kPa under the effect of the magnetic field. In a valve mode, the Magnetorheological damper (MR Damper or MRD), the MR fluid flows between two-fixed poles, which are parallel to each other. When the fluid flows between them, due to the applied magnetic field the magnetic particles align themselves in a chain form (on state) which is easily reversible when the field is removed (off state). Physical change of the fluid from liquid to semi-solid is controlled by the magnetic field, which makes the fluid a reliable member in active vibration control applications. In this study, two types of magnetizable particles (Carbonyl iron (CI) and Electrolytic iron (EI)) are taken and characterized using an Anton Paar MCR 702 rheometer set-up, in on and off states. To overcome issues like sedimentation, agglomeration and corrosion of the MR fluid, the iron particles are coated with natural gum like guar and xanthan, to the carrier fluid grease and other thixotropic additives are added. The addition of grease and thixotropic additives will inhibit the microbiological degradation of natural gum over an extended period. These engineered MR fluids are then used to analyze the performance of designed and developed stand-alone MR damper, which is tested using an electro-dynamic shaker. The response and damping performance of the MR Damper is analyzed with controlled changes in variables including percentage of additives in MR fluid & magnetization values

A smart composite with both rate-sensitive and magnetic-sensitive properties was prepared by dispersing carbonyl iron powder (CIP) into a silicon-boron copolymer matrix. In addition to following the common preparation procedure, a curing process used in the rubber industry was considered. Several groups of samples were prepared with and without including this curing process. For the samples that underwent the curing process, the absolute shear thickening effect was reduced by less than half compared to the samples that did not undergo the curing process, however, the relative shear thickening effect was increased by up to 6717.50%. In total, 16 groups of samples were tested under different curing conditions, such as different curing times and curing temperatures, to investigate the performance improvement. The results showed that to obtain a better relative shear thickening effect, a curing time of at least 20 min was needed. When the curing temperature was set to 120 °C, the absolute shear thickening effect was maximized. The influences of pyroboric acid and CIPs on the properties of the materials were also studied. Interestingly, the relative magnetorheological effect did not always increase with increasing CIP content. An increase in the amount of pyroboric acid increased the absolute shear thickening effect and decreased the relative shear thickening effect.

We report a simple, versatile and low-cost method to synthesize iron oxide microfibers with high efficiency and in large quantity. The method is based on the thermal decomposition of iron pentacarbonyl (Fe(CO)5) and silicone oil (SO), and vaporization of carbonyl iron (CI) in a microwave plasma. In this process, the mixture of CI and Fe(CO)5 is brought to a bursting state, and the triggered pressure sprays the reaction products in the form of gas–vapor iron columns. At temperatures lower than that of the iron vapor dew point, the columns freeze, and within tens of seconds microfibers are formed whose dimensions can be controlled by the temperature of the environment or by the microwave field power. SEM images show that their diameters are up to about two microns, arranged in a complex hierarchical structure. Magnetic measurements and EDX elemental analysis show the presence of magnetizable fibers containing iron/oxygen atoms in two proportions. XRD measurements show that the fibers consist of α-Fe2O3, γ-Fe2O3 and Fe3O4 iron oxides. We explain the physical mechanisms underlying microfiber formation by developing a theoretical framework based on the Higbie model. The obtained results can be used for fabrication of composite materials with magnetodielectric properties.

Magnetorheological gel (MRG) is a kind of magneto-sensitive smart material mainly composed of soft magnetic particles and polyurethane, which can decrease or even avoid the severe sedimentation problem appearing in MR fluids. In this work, the rheological properties of MRG under quasi-statically monotonic and cyclic loading with large deformation were investigated, respectively. The results could provide effective guidance for the design of MR devices that are often subjected to quasi-static loading. Firstly, MRG was fabricated by mixing carbonyl iron particles (CIPs) with the polyurethane matrix. Then, variations of normal force with time and magnetic field for MRG were tested and discussed. Moreover, the influences of CIPs content, shear rate, shear strain amplitude and magnetic field on the energy dissipation density of MRG were analyzed. The results showed the magneto-induced damping performance of MRG is highly relevant to the CIPs content and magnetic field, i.e. the magneto-induced enhancement of energy dissipation density of MRG with 60% CIPs content could reach up to 104 900% when the external magnetic strength increases to 391 kA m−1. Furthermore, the related mechanisms, from the perspective of microstructure, were proposed to qualitatively explain the various mechanical phenomena occurring in shear stress and normal force.

качестве объектов исследования использовали композиции на основе ПТФЭ, наполненные дисперсных нитридом бора гексагональной модификации, оксидом титана и карбонильным железом. Образцы для испытаний изготовляли прямым прессованием в соответствии с техническими условиями на полимер. Теплофизические и структурные характеристики полученных композиций определяли в интервале 130-650 К. При взаимодействии ПТФЭ с дисперсными наполнителями макроскопические свойства полимера определяются количеством и, вероятно, размерами кристаллических надмолекулярных образований при малой дозировке наполнителя и молекулярной подвижностью в граничных слоях полимера при среднем содержании наполнителя., As objects of research, compositions based on PTFE filled with dispersed boron nitride of hexagonal modification, titanium oxide and carbonyl iron were used. The test samples were made by direct pressing in accordance with the specifications for the polymer. The thermophysical and structural characteristics of the obtained compositions were determined in the range of 130-650 K. In the interaction of PTFE with dispersed fillers, the macroscopic properties of the polymer are determined by the number and, probably, the size of crystalline supramolecular formations at a low dosage of the filler and the molecular mobility in the boundary layers of the polymer at an average content of the filler.

This work investigates the mechanical properties, microstructures, and water-swelling behavior of a novel hydrogel filled with magnetic particles. The nanoparticles of magnetite (Fe3O4) and the micro-particles of carbonyl iron (CI) were selected and filled into a polyacrylamide (PAAM) hydrogel matrix to create two types of magnetic hydrogels. The isotropy and anisotropy of magnetic hydrogels are also presented in this study. The isotropic samples were cured without applying a magnetic field (MF), and the anisotropic samples were cured by applying an MF in the direction perpendicular to the thickness of the samples. The effects of the size, content, and inner structures of magnetic particles on the magneto-responsive and swelling properties of magnetic hydrogels were investigated. It was found that the magnetorheological (MR) effect of anisotropic samples was apparently higher than that of isotropic samples, and the hydrogels with CI exhibited a noticeable MR effect than those with Fe3O4. The storage modulus can be enhanced by increasing the filler content and size, forming an anisotropic structure, and applying an external MF. In addition, the magnetic hydrogels also have a swelling ability that can be tuned by varying the content and size of the particle fillers.

The movement of isotropic and anisotropic particles of iron and graphite within the polymer matrix was predicted and examined by the COMSOL simulation method. The interfacial adhesion of filler particles within the matrix was investigated under surface features observation. Carbonyl Iron (CI) particles, considered to be regular with a uniform size of (1–5 µm), were mixed with irregular particles of graphite (20–150 µm) with 30 V% in quantity in a silicone rubber matrix. The particle–matrix and particle–particle interactions were analyzed from the inner surface features. The drag of non-spherical particles and particle Reynolds numbers (Rep) were taken into consideration in point force models for both the Stokes (Rep ≪ 1) and Newton regime for particle shape. Newton regime is based on the aspect ratio for particles with regular and irregular shapes. The boundary area of the irregular particles holds like an anchor inside the polymer matrix for strong adhesion; however, regular particles have partial attachment due to the gravitational pull of attraction from the bottom contact points. However, uniform distribution of isotropic particles has been observed in comparison to the anisotropic particles within the polymer matrix.

Rheological properties of a natural rubber based magnetorheological elastomer (MRE) with spherical carbonyl iron particles (CIPs) and plate-like Sendust particles as soft magnetic particles were investigated. Isotropic and anisotropic MRE samples were prepared by molding in the absence or presence of magnetic field. Different shape of magnetic particles provided significant effect on mechanical properties of the MRE samples. The rheological properties of the MRE samples were measured in shear mode through a modified Dynamic Mechanical Analysis system equipped with an electromagnet. MRE samples containing plate-like Sendust particles showed higher shear storage modulus than MRE samples with spherical CIPs. Isotropic structures of the two types of magnetic particles contributed to improvement in MRE's performance, such as absolute and relative MR effect. The relative MR effect had a strain-dependent behavior that increased with increasing strain amplitude due to the Payne effect.

In this study, the polyurethane (PU) foam-based microwave absorbing materials filled with graphene (GP) and flaky carbonyl iron (FCI) particles were fabricated, and the effects of GP content and morphology structure on the microwave absorption (MA) properties were investigated. Scanning electron microscopy (SEM) and vector network analyzer (VNA) were used to elucidate the morphology structure and electromagnetic properties of the composite samples. The results showed that the absorption bandwidth of the materials could be improved by increasing the cell density. In particular, for a composite with 1.5 wt.% of GP and 70 wt.% of FCI, the minimum reflection loss (RL) of −53.8 dB was achieved at 9.4 GHz with the thickness of 2.2 mm, and the effective absorbing bandwidth (RL