Search

Magnetorheological polishing is a potential process for the low-damage manufacture of optics, semiconductors, and related devices. However, due to magnetic materials’ size and magnetic field strength limitations, a high-efficiency material removal rate can hardly be achieved in practical application. This work presents a novel high-efficiency magnetorheological polishing process, which employs Halbach array as magnetic field excitation to improve the processing efficiency. The Halbach array provides a large-area, high-intensity magnetic field, which is verified by finite element simulation and experiments. The force analysis of carbonyl iron particles in the magnetic field revealed the distribution of polishing pressure and polishing marks. The polishing performance of the process as well as the distribution of polishing pressure and polishing marks were investigated by polishing experiments. The effects of process parameters on the removal rate and surface roughness have also been systematically investigated. The novel magnetorheological polishing process can achieve 3.8 times material removal rate compared with the previous process. In the polishing processes of fused silica, the surface roughness reduced from 1979.154 nm to 0.544 nm in 60 minutes. To sum up, Halbach array could significantly improve the efficiency of magnetorheological polishing while preserving polishing quality.

In this research, a series of hollow glass powder (HGP) reinforced magnetorheological plastomers (MRPs) were prepared to improve the impact resistance of the materials, and the dynamic compressive properties of MRPs under high strain rate were investigated by using a split Hopkinson pressure bar (SHPB) system equipped with a customized magnetic device. Experimental results showed the HGPs greatly enhanced the yield stresses of the MRPs. Especially, for MRPs with 9 vol.% carbonyl iron powders (CIPs), the magnetic-induced yield stress increased from 7.3 MPa to 17.1 MPa (134% increased) by adding 18 vol.% HGPs. The particle structures in MRPs were further simulated and the corresponding intergranular stress was calculated to study the enhancement effect of HGPs. The simulated results showed that more compact structures were formed with the excluded volume caused by secondary HGPs, so the yield stresses of the MRPs increased under a magnetic field. However, when the mass ratio of HGP to CIP was larger than 0.67, HGPs would hinder the formation of chain-like structures and reduce the magneto-mechanical properties. As a result, the replacing of CIPs by HGPs was proven to be an excellent strategy to improve the dynamic properties of MRPs.

The growing demand of wearable device and the irreplaceable roles in stealth technique have boosted the exploration of high-performance flexible microwave absorbers. Herein, a novel flexible honeycomb structural absorber (FHSA) of carbon fiber (CF)/polyamide (PA)/carbonyl iron (CIP) composite was successfully fabricated via selective laser sintering (SLS) 3D-printing. The CFs arrangement and unit-structure were rationally controlled during the SLS 3D printing process for acquiring enhanced microwave absorption (MA) property, especially for the high bending angles. Therefore, under the high bending angle of 150°, the minimum reflection loss of the designed FHSA can reach −47 dB at 16.2 GHz with a broadband absorption of 13.2 GHz, covering the whole C2, X, and Ku bands, which breaks the traditional restraints that the flexible absorbers can only have the high MA property in tiling or minor bending status. In addition, the FHSA also showed the advantages of highly flexible deformation, self-recovery and no-crease damage in repeated bending, which could largely improve the environment applicability. This work provides a controllable strategy for the design of flexible microwave absorber, showing potential applications in wearable functional devices and military stealth protection.

The separation of oil spillage from marine environments has been discussed as a global concern. Recyclable superhydrophobic magnetic particles with micro-nano structures have been considered as a potential providing a safe, practical, and easy method for removing the oil from oil-water. In this research, the hydrophobicity of magnetic particles was enhanced to achieve the maximum adsorption capacity. For this purpose, reacted carbonyl iron (CI) with glucose was reacted with stearic acid under different condition of temperature, time, and concentration. Analytical tests were performed to confirm the reaction of stearic acid with CI@glucose. The prickly shape created on the surfaces of magnetic particles led to achieving the maximum superhydrophobicity. In this connection, the optimized superhydrophobic particles based on the maximum obtained water contact angle (WCA) of 169° at 75 °C, and 3.5 h and 10% concentration of stearic acid were selected for the oil-water separation. The results revealed that the superhydrophobic particles had acceptable stability within pH range of 2–12. The adsorption capacity of the modified particles for hexane, silicone oil, gasoline, and kerosene was 4.1, 2.5, 3.1, and 3.7 g/g, respectively, with a high adsorption efficiency ( > 99.7%) in the oil-water mixture. After ten cycles of using these particles, the adsorption capacity range was 2 to 4 g/g regardless of the number of recycling times, and no significant change was observed in the contact angle.

Though press and sinter powder metallurgy (PM) steel offers cost-effective solutions for structural applications, there is a constant drive for improvement in their density. Addition of nanopowder to the conventional micrometre-sized metal powder is explored to improve the sinter density. In this study, the effect of nanopowder addition in varying amounts has been studied. Carbonyl iron powder (

In this work, single- and double-layer electromagnetic wave absorbers were prepared by as-prepared MWCNTs/BaTiO3/pitted carbonyl iron composites. MWCNT/BaTiO3 (MW/BTO) was prepared via sol-gel method whereas the carbonyl iron particles (CI) were corroded via pitting corrosion method. The structural, microstructural, magnetic and microwave absorption properties of the composites were evaluated via X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM) and vector network analyzer (VNA) methods. CST studio software was employed to simulate the microwave absorption characteristics of double-layer absorbers. Moreover, the effects of changing matching and absorbing layer thickness (3 mm in total) and filler loading (10, 20 and 30 wt%) of the as-prepared composite on the microwave absorption properties were investigated. According to the results, maximum RL value for single layer absorber with 20 wt% filler loading can reach −11.5 dB at 9.7 GHz with 3 mm thickness and 0.4 GHz bandwidth. In contrast, double-layered absorber using 10 wt% of the composite in the upper layer (as matching layer) and 30 wt% of the composite in lower layer (as absorbing layer) can increase the reflection loss and absorption bandwidth values to −15.5 dB and 1 GHz respectively. Improving in absorption characteristics can be attributed to coupling interactions, impedance matching and multiple scattering. The main advantages of the prepared double layer absorber than single layer absorber are tuning the intensity and effective absorption bandwidth by adjusting the layer order, thickness and filler loading of each layer which shown good potential for practical application.

Microwave absorbing materials are of great importance on stealth technology, electromagnetic compatibility and radiation protection. The narrow absorption bandwidth restricts its further applications. Herein, the glass fiber (GF)/carbon fiber (CF) reinforced honeycomb metastructure (HM) consisting of carbonyl iron (CI) particles, multiwall carbon nanotube (MWCNT) and epoxy resin (EP) is designed by the evolutionary optimization (EO) program based on the proposed large mutation genetic algorithms (LMGA) and fabricated by vacuum bag techniques. The HM with and without GF achieves −10dB absorption bandwidth in 2–20.37 GHz and 2.76–40 GHz respectively. Wide-angle absorption in 0°–45° is realized. The GF/CF reinforced HM exhibits tensile and three-point flexural strength of 80.03 MPa and 34.66 MPa respectively. The integration of electromagnetic absorption and mechanical resistance is successful with the proposed design and fabrication methodology.

This study introduces magnetic MnFe2O4 nanoparticles and graphene oxide (GO) nanosheets to enhance magnetorheological (MR) properties and dispersion stability of the carbonyl iron (CI)-based MR fluid. The prepared CI/MnFe2O4/GO was transformed into CI/MnFe2O4/rGO through an annealing process and was used as an additive of the MR fluid. The shape, crystallinity, and magnetic properties of the composite were analyzed via SEM, TEM, EDS, XRD, and vibrating sample magnetometer. In addition, rotational rheometer and Turbiscan were used to examine the MR properties and dispersion stability of the MR fluid, respectively. The CI/MnFe2O4/rGO-based MR fluid exhibited higher shear stress, shear viscosity, and storage modulus than the CI-based MR fluid. The dispersion stability was enhanced due to GO with its low density and a large specific surface area, and the sedimentation ratio was improved approximately by 17% after 24 h owing to the reduced difference in the density between the magnetic particles and oil medium.

We demonstrated the mechanism that makes Graphene Oxide (GO) a superior material for corrosion protection over reduced graphene oxide (rGO) and nitrogen doped reduced graphene oxide (N-rGO). According to the results of our electrochemical study, supported by a host of characterization methods and density functional theory (DFT) based calculations, reduction of GO to synthesize rGO or doping of foreign heteroatoms like nitrogen to synthesize N-rGO, exposes and/or creates the defects/pores on the basal carbon plane of GO. Through these defects/pores of rGO and N-rGO, the corrodants react with the metal-surface and corrode it. A subnanometric layer of GO adhered to carbonyl iron (CI) surface through grafting by a thin Glycine (Gly) layer, repels the corrodants and shows robust corrosion protection performance in 1 M KCl solution, over a similar layer of rGO or N-rGO. Hence, our work demonstrate that a coating of GO on metallic Fe surface, grafted via a thin glycine layer, is the economical solution and has the robust performance for its direct industrial application for corrosion protection.

Magneto rheological fluids, often called smart fluids, play a significant role in effective mechanical braking systems, haptic devices, mechanical dampers and other mechanical devices. Presently, the properties of Magneto rheological fluids added with additives or nanoparticles were discussed. The introduction of an additive/nanoparticle in MR fluid alters the mechanical, thermal, structural and other properties of the fluid. The characteristic feature of this fluid is that they become solidified under the effect of an applied magnetic field. This is mainly due to the chain development of suspended molecules in the fluid medium. When these fluids are mixed with nanoparticle additives, these chain forms become stronger, as the nanoparticles occupy the spaces among the molecules of MR fluid. This in turn increases the dispersion stability, yielding strength of the fluid under action. Due to higher solubility of suspended iron particles, the Carbonyl Iron based MR fluid is the most commonly used MR fluid.

MR fluids face a major problem of sedimentation rate due to the high- density difference between the magnetic particles and the carrier medium that affects the performance of the magnetorheological devices. In this work, two MRF samples are prepared, where MRF-1 and MRF-2 are pure and coated carbonyl iron particles (CIPs) based MR fluids. The surface modification of the CIPs is performed using the solvent dispersion method to improve the sedimentation rate. The spherical shape and particle size analysis of the pure CIPs and coated CIPs’ morphology is investigated using the Scanning Electron Microscope (SEM). The Thermal Gravimetric Analysis (TGA) shows that the coated CIPs have high thermal stability and confirm that 6% by wt. coating is present in the coated sample. The chemical bonding of the coated CIPs is detected using the Fourier Transform Infrared Spectroscopy (FT-IR). The saturation magnetization (Ms) of pure and coated CIPs is 245 emu/g and 120 emu/g, respectively, at 15 kOe, which is obtained by using a superconducting quantum interface device (SQUID). The rheology flow curve properties show that MRF-1 and MRF-2 exhibit yield stress of about 10 kpa and 9 kpa, respectively, for varying magnetic fields ranging from 0 to 343 kA/m. The Herschel-Bulkley model is fitted with the experimental data and the shear thinning behaviour is observed for both MR fluids. The sedimentation study shows that MRF-2 has better settling rate than MRF-1, which is observed by using the visual observation method up to 600 h.

Rod-like magnetite/sepiolite nanocomposite particles were fabricated using a chemical co-precipitation process and introduced as an added ingredient in a carbonyl iron (CI)-based magnetorhological fluid (MRF). The morphologies of the composite particles and CI-magnetite/sepiolite mixture were observed by scanning electron microscopy. Two types of MRFs with and without magnetite/sepiolite additive were fabricated, and their MR behaviors and sedimentation stability were investigated using a rotation rheometer and an optical analyzer system of Turbiscan, respectively. The results showed that the addition of rod-like magnetite/sepiolite additives enhanced both the dispersion and MR properties of CI-based MRF, making its potential application more promising.

Spherical carbonyl iron (Fe) powders were coated with magnesioferrite (MgFe2O4) insulating coating layer and then mixed with epoxy-modified silicone resin (ESR). Soft magnetic composites (SMCs) were fabricated by compaction of the coated powders and annealing treatment. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS) revealed that the MgFe2O4 layer was coated on the surface of the iron powders. The magnetic properties of SMCs were determined using a vibrating sample magnetometer and an auto testing system for magnetic materials. The results showed that the SMCs prepared at 800 MPa and 550 °C exhibited a significant core loss of 167.5 W/kg at 100 kHz and 50 mT.

Impedance matching and enhanced microwave attenuation have been proven to be effective strategies for improving reflection loss (RL) and widening of the effective absorption (RL

High-energy ball milling is a very common method to produce materials with high magnetic permeability due to its ability to produce flaky shape particles on the nano-scale. It is an efficient technique to improve microwave absorbing properties. Therefore, this study aims to achieve an ideal microstructure and improve microwave absorption properties of flake carbonyl iron powder fabricated by high-energy ball milling. The influence of pre-heating at different times/temperatures on magnetic absorbing properties is also investigated. Further, the relationship between heat treatment temperature, permeability is analyzed. Microstructural analyses reveal that the phase of the material does not change with the change of pre-heating temperature. However, the material made by ball-milling has a finer grain size and a higher flattening ratio. The results show that the length to diameter ratio of the flake material can be increased by pre-heating, and thus improve the magnetic permeability and absorbing performance of the material. The optimal parameters of pre-heating are obtained at the temperature and time of 200 °C and 2 h, respectively, wherein the real part of the permeability reaches up to 3.20 at 2 GHz, the imaginary part reaches 1.61 at 6.2 GHz.

For the aspheric optical surface finished with a doughnut-shaped MCF (magnetic compound fluid) polishing tool, the performance of the polishing tool depends mainly on the properties of the MCF slurry. Therefore, understanding the effect of each MCF slurry component on the polishing characteristics is crucial to developing novel polishing techniques. In this paper, the polishing principle was depicted and the corresponding polishing jig was constructed with a six-degree-of-freedom manipulator. The conical surfaces, which were considered as special aspheric surfaces, were experimentally polished under proper polishing conditions to examine the effects of the carbonyl iron particles (CIPs) concentration and the sizes of the abrasive particles (APs) on the polishing ability to remove material/tool marks and improve work surface qualities. Theoretical analyses were also performed to gain a more comprehensive understanding of the behaviors of CIPs and APs in the magnetic field. The results were shown as follows: (1) The CIPs concentration affected positively the magnetization of the MCF slurry, leading to better performance in the removal rate of material/tool marks when a higher CIPs concentration of was applied. The best surface quality was attained with a CIPs concentration of 45 wt%. (2) Larger APs were beneficial for obtaining higher removal rates of material/tool marks. The APs with 1 μm in diameter were preferred for achieving a better surface quality. (3) Ferric clusters were formed along the magnetic line of force and their orientations changed periodically to stir the APs with the magnet revolution. (4) The Aps, at a given working gap, can squeeze the work-surface. The squeezing action was much more intense when larger APs and the MCF slurry with a higher magnetization were employed. (5) The material removal model suggested that the material was removed due to the APs and the relative motion between the work-surface and APs.

Iron coated carbon nanotube (CNT) nanocomposite absorbents were prepared by a metal organic chemical vapor deposition method using carbonyl iron as the Fe precursor. The microstructures and electromagnetic properties of the composites were characterized by XRD, FESEM, TEM, and a vector network analyzer. Results show that the morphology and microwave absorption properties of these core-shell composites are controlled by changing the deposition temperature. The number of iron nanoparticles deposited on the surface of the CNTs gradually increases with increasing deposition temperature in the range 210–240 oC. Too high a temperature (270 oC) causes agglomeration of the Fe nanoparticles on the surface of the CNTs. When the thickness of the electromagnetic coating is 2.9 mm, the composite prepared at 240 oC has the best microwave absorption, with a maximum absorption bandwidth of 6.1 GHz (10.2-16.3 GHz), a minimum reflectivity of −28.3 dB and an absorption intensity less than −10 dB at 6.1 GHz.

The available magnetic field assisted finishing process is considered as the critical stage for improvement of workpiece surface quality. This paper aims to investigate the key quality performance of an enhanced magnetic abrasive finishing in achieving nanolevel finish on Ti–6Al–4V workpieces with initial micrometer surface roughness values. The finishing media, combining the intelligent shear thickening fluids (STFs), carbonyl iron particles and SiC particles, is developed. Finishing experiments for Ti–6Al–4V workpieces are conducted using an established platform, aiming to investigate the effects of varying STFs concentration, working gap, feed rate and spindle rotational speed. It is observed from the experimental results that the developed finishing media is effective for surface finishing comparing to the finishing media without STFs. The surface roughness of 54 nm was achieved from the initial value of 1.17 μm, which improved by over 95%, under the experimental conditions of 0.8 mm working gap, 15000 mm/min feed rate, 900 rpm spindle rotational speed and 15 wt% STFs. Surface observations showed that a smooth surface without obvious scratches was obtained.

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.

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

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

In this study, novel CIP@EP composites with a core-shell structure were prepared by using the in-situ polymerization method. The phase structure, morphology and thermal stability were investigated by FTIR, XRD, SEM, TEM and TG. The results indicated that EP were densely covered on the surface of CIP particles, and with the increase of EP contents, the EP shell became thicker, which effectively strengthened the thermal stability of the materials. The magnetic and electromagnetic properties of the composites were systematically investigated. It was found that the content of EP played an important role in improving the magnetic and dielectric properties. High EP content can effectively improve the impedance matching between the dielectric and magnetic loss of the absorbers and enhance the EM wave absorption ability of the composites. This study proves that the CIP@30%EP exhibits an excellent EM wave absorption ability, which has higher value of RL and wider absorption width than other CIP@EP composites. The CIP@30%EP has a strong reflection loss peak of −16.1 dB and wide effective absorption bandwidths of 5.4 GHz at the thickness of 2.2 mm. Furthermore, the method utilized to synthesis the CIP@EP composites can be a suitable and efficient way to prepare other spherical microwave absorption materials.

Electrical capacitors (EC) are manufactured having environmental-friendly and cost-effective bioactive hybrid magnetorheological suspensions (hMRSs) as dielectric material. hMRSs are prepared by soaking a cotton fabric with a liquid solution based on honey bee (HB), wax and various concentrations of carbonyl iron (CI) microparticles. We investigate the response of EC to a static magnetic field with and without an electric field, and to time-periodic magnetic fields. We show that the induced magnetodielectric properties are sensibly influenced by concentration of CI, and are comparable to those of MRSs based on chemically synthesized components.

This study deals with different magnetic additives based on ferrites (MnZn, LaCa (Co and Ti)), carbonyl iron (CI), and iron filaments (IF) formulated in epoxy resin. Morphological and structural characteristics of the additives were evaluated. Based on these additives samples with both different thickness and weight fractions (1–70 wt%) were prepared. The formulated composites were analyzed considering different electromagnetic characteristics: reflectivity, shielding effectiveness, the complex parameters of dielectric permittivity (e) and magnetic permeability (µ), and the corresponding loss tangents in the microwave X-band. Scanning electron microscopy assisted with energy-dispersive spectrometry (SEM-EDS) analyses show that the additives have different morphologies, with varied sizes, shapes, and compositions. X-ray diffraction (XRD) analyses allowed determining the structural phases of the magnetic additives: CI and IF are constituted by Fe-α phase, the ferrite of MnZn has an unique phase, and the two ferrites of LaCa-Co and LaCa-Ti have the same phase in the presence of different metallic oxides. In general, the complex parameters of e and µ increased with the additive concentration increase in the composites, as expected, considering the magnetic characteristics of all additives studied. Reflectivity measurements show different attenuation values with promising results for composites based on CI, IF, and MnZn ferrite. The composites based on the ferrites show the worst performance on the reflectivity measurements. The shielding effectiveness measurements show good results (20 dB) over the entire X-band for specimens based on the LaCa-Co ferrite. In this case, the dominant shielding mechanism is due to the multiple scattering (SEM) in the material.

Secondary iron-air batteries re-gained considerable scientific attention due to their excellent energy densities, pronounced environmental friendliness and exceptional reversibility compared to other metal-air batteries. In order to exploit the energy density of iron on full-cell level, the ratio between anode- and overall battery material should be as large as possible, aiming at practically competitive iron-air battery performances in the future. Therefore, here, we report the investigation of comparatively thick, pressed-plate, carbonyl iron-anodes and the distinctive attempt to further elucidate the processes behind the electrochemical formation. In order to do so, the electrode thickness-dependent charge-/discharge performance, the wetting behavior and the specific surface area of the electrodes were examined. In addition to the established dissolution and precipitation mechanism of iron, we propose that a gradually increasing number of electrochemically active carbonyl iron particles may be an additional source of active iron surface for the steeply increasing discharge capacity during the formation, which is particularly relevant for thick rather than thin electrodes. Furthermore, substantiated by cross-section SEM-images, we propose that the increasing number of active carbonyl iron particles is induced by microstructural changes of the electrode, hypothetically driven by hydrogen evolution during the formation period. Bound to the access of electrolyte, the process suggests the presence of active material on the outside and inactive, since non-wetted, material on the inside of porous carbonyl iron-anodes depending on their state of formation.

A silicone oil based magnetorheological fluid (MRF) containing carbonyl iron-wrapped multi-walled carbon nanotubes (CI-MWCNTs) and fumed silica were fabricated for antisedimentation. CI-MWCNTs as magnetic materials were synthesized by a mild ultrasonication method through 4-Aminobenzoic acid (PABA) as a grafting agent and fumed silica as a filler. Additionally, the density of the carbonyl irons (CIs) was reduced by carboxyl group functionalized multi-walled carbon nanotubes (MWCNTs) and the density of the silicone oil was improved by fumed silica to balance the density between the magnetic materials and carrier fluid. Furthermore, the superparamagnetic materials of CI-MWCNTs maintained a saturation magnetization of 206 emu/g at a magnetic field of 10000 Oe, which was investigated via a vibrating sample magnetometer (VSM). Finally, the CI-MWCNT-based MRF was better than the CI-based MRF based on the magnetorheological effect and antisedimentation.

Designing novel structure to optimize the dielectric constant and permeability was believed as an effective way to improve the performances of wave-absorbing material. In this work, PVA coating containing homogeneously-distributed graphene oxide (GO) was firstly deposited onto the surface of carbonyl iron powder (CIP), which was then followed by a heat-treatment to obtain rGO/PVA/CIP composite materials. The electromagnetic parameters (relative complex permittivity and permeability) and corresponding loss mechanism of the as-prepared rGO/PVA/CIP composites were investigated in a frequency of 2.0–18.0 GHz. It was found that the presence of well-dispersed rGO could effectively improve the dielectric loss of the composites and microwave absorption capability without sacrificing magnetic loss. The effective absorbing width (reflection loss lower than −10 dB) of PVA/CIP composite containing 1 mg/g GO was measured to be ∼8.4 GHz.

Spinel ferrite nanoparticles with enhanced magnetism were prepared by non-stoichiometric doping of Zn cation to magnetite and adopted as an additive into carbonyl iron (CI)-based magnetorheological (MR) suspension, with the expectation of improved MR effect and suspension stability. Rheological characteristics of the MR fluids both with and without an additive were analyzed using a rotational rheometer. The addition of 0.5 wt% Zn-doped ferrite (ZnxFe3-xO4) to the MR fluid enhanced not only the MR performance but also sedimentation stability, as confirmed by Turbiscan. The nanoparticles of truncated octahedron-like shape were thought to be inserted into the free volume between microparticles.

To evaluate the microwave absorption properties of the graphene oxide (GO) sheets capsulated on carbonyl iron particles (CIP), we synthesized the GO capsulated on carbonyl iron particles (GOCIPs) by a simple wet stirring process. Complex permittivity were increased with the increment of mass ratio of GO in GOCIPs from 0.5 to 2 wt% while the complex permeability values were not changed. The maximum reflection loss (RLmax) and frequency bandwidth at −10 dB (BW@-10 dB) of the 1.9 mm thick-GOCIP composite with 2.0 wt% of GO in GOCIPs exhibited about −56.4 dB @10.8 GHz and 5.1 GHz. The RLmax frequency shifted to lower frequency with the increment of absorber thickness from 1 mm to 3 mm. BW@-10 dB decreased with the increment of absorber thickness.

We fabricated magnetorheological (MR) elastomers using polyurethane and carbonyl iron based MR suspensions. Using dipolar approximation and linear elasticity theory for small deformations, we determined their components of deformations and tensions, showing that their elasticity state depends not only on magnetic field intensity but also on volume fraction. MR characteristics of elastomers’ dynamic properties and creep-recovery values were also measured using a rotational rheometer equipped with a magnetic field supplier. Experimental results from both plane capacitors and viscoelastic tests showed similarities between static and dynamic elasticity states regarding their dependence on magnetic field intensity and volume fraction of magnetizable phase.

To achieve ultra-broadband radar absorption at small thickness, the integrated design of component and configuration of a rubber matrix flexible radar absorbing composite (RAC) is performed in the present study. At the material component level, hydrogenated acrylonitrile butadiene rubber (HNBR) reinforced by flaky carbonyl iron particles (FCIP) ensures the considerable permeability of RAC, as well as its good flexibility, mechanical strength and elongation to break. At the structure design level, a novel modified step-configuration (MSC) is proposed through full-wave calculation. The preparation process of RAC with the modified step-configuration includes components mixing in a two-roll mixer and hot-press moulding. Radar reflectivity testing experiment demonstrates that, by integrated design of component and configuration, the absorbing bandwidth corresponding to −10dB can span from 2 GHz to 30 GHz for a 5 mm-thick composite absorber.

In this work, electromagnetic (EM) wave absorbing properties of polypyrrole/silicone rubber (PP-SI) filled nano-carbon and carbonyl iron (CI) nanocomposites have been investigated in the X-band. The PP-SR matrix was provided by the incorporation of polypyrrole and liquid silicone rubber in the ratio of 10:90. The PP-SR serves not only as a matrix but also promotes the flexibility and EM wave absorption of the nanocomposite sheets. In the present research, the chemical, morphology, thermal, wetting, absorption, and mechanical properties of the EM wave absorber sheets are investigated. The EM wave absorber sheet with 3 wt% nano-carbon and 37 wt% CI and a thickness of 1 mm, exhibits a minimum reflection loss around −13 dB at 10.27 GHz. The absorber sheet with an elongation of 520% could be qualified as a superior elastic sheet. The specimen represents higher thermal stability compared with pure SR, and the contact angle of the sheet proved that their surface should be hydrophobic.

A novel method for fabricating the two-layer honeycomb sandwich structure absorber (THSSA) was developed. The honeycomb cores with different pore sizes coated with epoxy resin filled with conductive carbon black as lossy filler have been fabricated by dipping processes. The microwave absorption properties of the honeycomb sandwich structure absorber (HSSA) with one-layer honeycomb core and two-layer honeycomb core have been designed and measured using arch measurement system within 2–18 GHz. The matching layer on the top of the honeycomb core can enhance the microwave absorption properties. The value of reflection loss can reach −10 dB in the frequency range of 4.9–18 GHz with an absorber thickness 9 mm for the fabricated THSSA with the flaky carbonyl iron powder (FCIP)/epoxy resin composite at the bottom. It was shown that the THSSA with lightweight and broadband absorption properties have a promising future in decreasing electromagnetic wave irradiation and interference.

Microwave absorbers as an effective way to reduce microwave radiation in stealth technologies and electromagnetic compatibility have attracted great attentions recently. Herein, a novel multifunctional carbon fiber (CF)/glass fiber (GF) reinforced lossy lattice metastructure for broadband microwave absorption and effective load bearing is proposed for the first time based on the structural similarity of photonic crystal and lightweight mechanical lattice. The lossy lattice is fabricated with nano lossy composite composed of multiwall carbon nanotube (MWCNT) and spherical carbonyl iron (CI) particles to manipulate complex permittivity and complex permeability. Sub-wavelength effect and structural optimization are applied for the metastructure to extend −10 dB absorption bandwidth from 3.42 GHz to 19.73 GHz with thickness of 3.5 mm. With solid attachment of CF and GF, the metastructure achieves high average equivalent strength of 167.35 MPa and fracture strain of 5.45%. A long plastic stage of the metastructure is observed after GF fracture or GF delamination in three-point flexural test. The integrated design of microwave absorbing and mechanical properties make it promising for practical applications in mass production.

Impedance matching is primary for broadband and strong absorption. Here, we optimized the impedance matching condition of the carbonyl iron powders (CIPs) layer by stacking the layered ultra high molecular weight polyethylene (UHMWPE). The double-layer absorber with its absorption more than 90% within the frequency range of 4.4–18 GHz is obtained by simulation and validated by experiment, while the single CIPs layer shows its broadest bandwidth only within 4.8–8.4 GHz. By simulating the angular performance, the double-layer has been confirmed to be omnidirectional and polarization insensitive. Besides, the impedance matching property of the double-layer is highly correlated with the thickness of UHMWPE layer, and the broadband absorption is resulted from the combination of the impedance matching layer and the absorbing layer. The designed absorber, stacked with the impact resistant UHMWPE layer, has great prospects for practical application under the requirement for bulletproof property.

This paper investigated the rheological properties of a novel magnetorheological elastomer (MRE) with plate-like carbonyl iron particles (CIPs) as magnetic particles. MRE samples with different shape of CIPs; plate-like (MRE-P) and spherical-like (MRE-S), were prepared. The current work further highlights the effects of varying curing magnetic field towards the rheological properties. X-ray diffraction and magnetic properties analysis were carried out to observe not only the surface morphology of the CIPs but also the cross-section of CIPs in the MRE samples. Rheological properties such as strain amplitude, frequency, and magnetic field sweep test were measured using a rotational rheometer. The MRE-P samples demonstrated higher storage modulus and the loss factor lower than MRE-S. Besides that, the MR effect of MRE-P samples is slightly lower than that of MRE-S correspond to 114% and 137%, respectively.

Novel core@shell@shell structured carbonyl iron powder (CIP)@SiO2@ Mn0.6Zn0.4Fe2O4 ferrite composites having great microwave absorption characteristics were successfully synthesized using chemical co-precipitation. The microstructure, morphology and microwave absorption performance of CIP@SiO2@Mn0.6Zn0.4Fe2O4 ferrite composites were systematically investigated. The results show that both coating layers of SiO2 and Mn0.6Zn0.4Fe2O4 are uniform and fine. The prepared CIP@SiO2@Mn0.6Zn0.4Fe2O4 composites in this study display better dielectric loss and frequency characteristic at high frequency than CIP, CIP@SiO2 and CIP@Mn0.6Zn0.4Fe2O4. The results of electromagnetic parameters also indicate that the enhanced microwave absorption performance primarily originates from the substantial contributions of magnetic loss to reflection loss. The optimal value of reflection loss of CIP@SiO2@Mn0.6Zn0.4Fe2O4 having the thickness of 2 mm can reach up to −44.24 dB at 11.57 GHz as well as the bandwidth (RL ≤ −10 dB) from 9.04 to 16.16 GHz among the frequency range from 2 to 18 GHz. In addition, the greatly enhanced microwave absorption performance is attributed to good wave impedance matching, high attenuation constant, multi-relaxation processes and multiple interfacial polarization.

The magnetization of a magnetoactive elastomer (MAE) with microparticles of soft magnetic carbonyl iron embedded in a highly elastic matrix has been studied. It is shown that at high temperatures its magnetization curve has the form of a specific hysteresis loop. This hysteresis is attributed to the influence of displacement of magnetized particles in the elastically soft elastomer matrix under the effect of magnetic forces, leading to the change of magnetic interaction between the particles. In this case, there is a maximum in the field dependence of the magnetic susceptibility, the occurrence of which has been associated with the competition between re-arrangement of particles, when they are displaced in a magnetic field, and saturation of particles’ magnetization. When the MAE is cooled below approximately 225 K, both the magnetic hysteresis and the maximum in the field dependence of the magnetic susceptibility disappear. When the MAE material is cooled below the solidification temperature of the elastomer matrix, the displacements of the magnetic particles during magnetization are blocked by the rigid matrix. The magnetization reversal of the MAE is reversible. This means that the shape of subsequent magnetization loops remains constant and the sample returns into the initial non-magnetized state after the magnetic field is turned off.

Magnetoactive tissues are prepared from a mixture of silicone oil (SO) and various volume concentrations Φ of carbonyl iron (CI) microparticles impregnated in a cotton cloth. The obtained tissues are examined as dielectric materials for manufacturing electrical capacitors. By using the plane capacitor method, we show that the relative dielectric permittivity, apparent viscosity, modulus of elasticity, and the components of deformations and of mechanical tensions can be sensibly influenced by an external magnetic field and by Φ . These effects make the obtained tissues versatile candidates for applications which require textiles consisting of conductive fillers, powders, yarns etc. embedded into non-conductive fabric fibers and with pre-established strength and flexibility. An immediate application is in fabrication of magnetic field sensors for detection of magnetic flux densities in the range 40 ÷ 180 mT.

In this research, a facile in-situ growth method was applied to load ZnFe2O4 nanoparticles on carbonyl iron (Fe) flakes. These loaded ZnFe2O4 exhibited cone shape with an average size of ∼200 nm. The results revealed that the frequency region with reflection loss

The tower-like absorbing structures were designed and fabricated by the 3D printing process to achieve the good absorbing property and low density. The absorbing composite was composed of the carbonyl iron particles (CIPs) and the polylactic acid (PLA). The scanning electron microscopy was done to characterize the composite morphology, and X-ray diffraction (XRD) patterns were done to analyze the particle crystal grain structure. The complex permittivity and permeability of the printed wires were measured using a vector network analyzer, and the permittivity and permeability of the hollow composite were derived, the reflection loss (RL) of the composite could be simulated. The results showed that the tower-like absorbing structure had the good absorbing property, and based on the printing pathway the density of the composite could be decreased as the filling ratio was set. The frequency band (RL

Micro and nano finished surface has its great demand in industrial as well as medical application for their superior properties. Recently newer methods are developed to get the nanometric surface finish. Magnetorheological (MR) finishing is the processes which can generate nano level surface finish. Therefore finishing of metals by using MR finishing process is required to be studied. MR finishing can remove the material of hard and difficult to cut engineering materials for their electronic, optical, etc. industrial applications. The MR finishing is a newly developed technique which uses MR fluid for finishing of the materials. MR fluid is the combination of carbonyl iron particles (CIP), abrasive and a carrier fluid such as water. In this study, introduction to the process has presented. Literature has been study in the area of MR finishing for different development of setups for different materials. MR finishing carried out on the copper alloy workpiece to investigate the MR finishing process and their parametric analysis. Results show that significant improvement in the surface finish of the work surface.

In this study we experimentally examine the mechanical stress induced by the striction of hybrid magnetoactive elastic composites in the direction parallel to an externally applied magnetic field. Elastic samples based on a polydimethylsiloxane matrix with embedded spherical magnetic soft carbonyl iron particles, spherical magnetic hard NdFeB-alloy particles as well as on a mixture of the two kinds of powder are under investigations. An effect of the structuring and pre-magnetization of the samples on the stress induced by the magnetodeformational effect is evaluated.

Electromagnetic (EM) noise interference in high-frequency communication systems has attracted considerable attention. Flake-shaped iron-based alloy powder–polymer composites are the conventionally used EM noise suppressors; however, they exhibit low stretchability and cannot effectively suppress EM noise in the range of several gigahertz. The present study demonstrated the application of carbonyl iron powder (CIP)/polydimethylsiloxane (PDMS) composites as EM noise suppressors at 1–18 GHz. The CIP/PDMS composites presented excellent mechanical properties (rupture strength 6.57 MPa, elongation 71%) even at the maximum CIP content of 40 vol%. The tensile test results and finite element method (FEM) simulations revealed a lowering of the elongation with CIP loading content, which was attributed to the localized stress at the agglomerated CIPs. The spherical CIPs exhibited multicore shell interface structures with 2–300 nm ring gaps that were larger than the skin depth of pure iron. EM absorption characterization revealed that the magnetic loss tangent at 10 GHz increased linearly with increasing CIP content. Furthermore, the power loss at 10 GHz for the 40 vol% CIP/PDMS composite was 2.25 times higher than that for the 20 vol% CIP/PDMS composite. This indicated the effective suppression of EM noise in the gigahertz bandwidth with the addition of CIP.

The magnetic permeability of three kinds of inclusions (Carbonyl iron, Ferroferric oxide, NiFe-alloy) filled polymer (Polydimethylsiloxane) is investigated at room temperature by using a Buck circuit for the dynamic test and vibrating sample magnetometer (VSM) for the static test. Unlike the traditional measurement method using an impedance analyzer, the self-built circuit can generate a maximum test current of ampere amplitude over high frequencies to simulate the transformer's operation status. The present work considers the effects of inclusion content (from 0 VOL.% to 33 VOL.%) and testing frequencies(100 kHz-1MHz). The experimental results of permeability are compared with the theoretical predictions in the previous works. Three main conclusions can be drawn: First, the magnetic permeability increases with the inclusion addition; Second, as the testing frequency increases, the permeability of the composite material maintains constant, showing no evident dependence on the testing frequency; Third, type of magnetic inclusion will gently affect the permeability of the composite material. This work systematically investigated the permeability of polymer-based magnetic materials, and the results are helpful for the soft-core transformer application of magnetoactive elastomers.

Soft magnetic membrane (SMM) is regarded as a potentially functional component in soft intelligent sensors, biomedical and robotic applications. In this study, SMMs composed of carbonyl iron powders (CIPs) (10 vol%–30 vol%) and ECOFLEX-0030 matrix are fabricated and placed in the magnetic field that is generated by a cylindrical neodymium-iron-boron permanent magnet. In order to investigate the magnetomechanical response of SMMs, a simple but effective model is constructed. The predictions by the model agree remarkably well with the experimental observations. Based on the results in the present work, the SMM with 15 vol% inclusion possesses the largest deformability. The maximum stretch ratio in all the cases does not exceed 1.1, which indicates that the stress–strain relation is in the linear range, though the overall deformation is non-linear due to rotation. The versatility of the proposed model provides a convenient tool in the design of SMM driving devices.

In this research, we reported a novel low-cost and efficient composite consisting of corroded carbonyl iron (CCI), calcium copper titanate (CTO) and polyaniline (PANI). The XRD analysis shows that the CTO sample exhibits a pure crystalline phase with an orthorhombic structure, while the amorphous peak of PANI appears at 25.4 ° , corresponding to the (200) crystal plane. Morphological investigations have shown that the pitching corrosion has successfully altered the smooth surface of the carbonyl iron and that the CTO sample exhibits a near cubic shape. The formation of a continuous network of the [CCI/CTO]@PANI composite is also evident in the FESEM images. The electromagnetic (EM) wave absorption capability of the [CCI/CTO]@PANI composite was investigated at the 2–18 GHz range. The [CCI/CTO]@PANI composite sample with 30 wt% and thickness of 2 mm exhibits reflection loss ( R L ) of − 22.0 dB at 14 GHz with a bandwidth of 6.5 GHz covering the range 11.5 − 18.0 dB which is more than the entire bandwidth of the Ku band.

The formation of core–shell structure is one of the standard methods to improve the corrosion resistance of carbonyl iron powders (CIPs). In this manuscript, epoxy resin (EP) was coated on the surface of flaky carbonyl iron particles (FCIPs) by a simple one-step polymerization method to form the FCIP@EP composite particles, and they were used to obtained microwave response to accurately simulate, predict and optimize the microwave absorption performance of composites. After being coated by epoxy resin, the composite exhibits a higher percolation threshold; the absorbing performance is more stable in an acidic environment. The optimal loading of FCIP@EP in the matrix can be obtained by data-driven optimization, and the model calculation results are in good agreement with the actual measured ones. At 23 vol%, the composite's effective absorption bandwidth (EAB, RL

Great attention has been paid to superhydrophobic surface with tunable water adhesion behaviors, but many challenges still remain for developing a surface with accurate regional control of the superwetting behaviors to realize on-demand responses. Herein, a superhydrophobic surface with accurately controllable water adhesion performance for local areas has been developed, by integrating carbonyl iron particles (CIPs) into a shape memory polymer (SMP) to get photothermal-responsive pillar array. The morphologies of the programmed surface can be remotely and accurately regulated through near-infrared (NIR) light irradiation, hence resulting in the accurate control of surface superwetting behaviors. By adjusting the intensity and targeted area of the NIR irradiation, the controllable surface deformation even in a minimal area of ~0.95 mm2 can be achieved. Among those, the surface with bent microstructures demonstrates high water adhesion force (98 μN) with a high water rolling-off angle (even the surface was overturned to 180°), whereas the superhydrophobic surface with the recovered micro/nanostructure arrays exhibits relatively low water adhesion force (25 μN) with an extremely low rolling-off angle (4°). We have proven that these programmable superhydrophobic surfaces can not only accurately adjust the droplet adhesive force in the target area, but also serve as ideal platforms for distinct microfluidic microreactors. These unique characteristics endow the NIR light remotely controlled superhydrophobic surfaces with special advantages for abroad applications in liquid droplet manipulations, micro reactions, biochemical detections, etc.

Magnetic absorbing materials suffer from corrosion and aging in harsh environments such as ocean and acid, which limits their practical applications. Therefore, it is important to design a material with excellent corrosion resistance and microwave absorption properties. Herein, perfluorooctyltriethoxysilane (PFOTES) modified carbonyl iron (CI) with tunable PFOTES content was prepared by the sol–gel method. The presence of PFOTES layer improved the corrosion resistance and microwave absorption of CI. The good hydrophobicity of PFOTES layer with the static contact angle of 129.73° hindered the contact of corrosive medium with CI core. The corrosion current of CI@PFOTES composite decreased significantly, and the corrosion rate was reduced by three orders of magnitude. The surface coating not only affected the electromagnetic parameters of carbonyl iron, but also improved the impedance matching of materials. Electromagnetic performance test results demonstrated that the microwave absorption performance of CI@PFOTES composite was better than that of carbonyl iron, and its minimum reflection loss was − 40.45 dB at 4.08 GHz with a matching thickness of 3.5 mm. Our work provides a new perspective for preparing composites with good microwave absorption and corrosion resistance in practical applications.