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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.

Magnetorheological elastomers (MREs) are smart materials whose mechanical properties can quickly respond to changes in the external magnetic field. This phenomenon is known as the magnetorheological (MR) effect and is the key to the application of magnetorheological elastomers. Previous studies have found that the interface between magnetic particles and elastomers is a critical factor that influencing the MR effect of MREs. To improve the interfacial interaction between silicone rubber (SR) and carbonyl iron (CI) particles, in the MREs considered in this work, CI particles were subjected to surface modification through polydopamine (PDA) deposition and n-dodecyltrimethoxysilane (DTMS) grafting. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the successful deposition of PDA@DTMS coating layer with a thickness of about 30.6 nm. The tensile strength of anisotropic MREs increased by 31.5% after surface modification of CI particles. The study of magnetic field induced changes in viscoelastic properties showed that CI-PDA@DTMS based MREs exhibited a superior MR effect to the CI-based MREs.

To improve dispersion stability and magnetorheological (MR) characteristics of carbonyl iron (CI) particles, we proposed novel hydrogel magnetic microspheres (MPs) dual-coated with alginate (AL) and chitosan (CTS) for the first time. The double-network structures formed by biological crosslinking and chelation reactions are capable to enhance its own structural stability and mechanical properties. The structural characterization, MR properties, and dispersion stability for different MPs were investigated. Additionally, the swelling behaviors were studied by swelling the dried MPs in the deionized water and sodium chloride solution, respectively. The results showed that the AL/CTS hydrogel core/shell MPs displayed the advantages of simple manufacturing, superior MR properties and deformability compared to pure micron-sized CI particles, indicating the improved dispersion stability of the MR fluids compared to that of the pure CI particles-based MR fluids. The introduction of double network structures with natural biopolymers will provide a new thought for the development of MR materials.

A novel magnetic ionic liquid (IL) based on 1-methylethyl ether-3-butylimidazole cation and [FeCl4]− anion was synthesized for application as a carrier of magnetorheological fluids (MRFs). Stability and magnetic response of the MRFs were investigated as a function of the anion chemical structure and content of carbonyl iron fibers. The MRFs based on the magnetic ILs displayed better redispersibility, slower settling rates, and increased magnetic-induced stress compared with conventional MRFs based on oils or ILs. Furthermore, the mechanism of MRFs with good performance was investigated and proposed by molecular dynamic simulation. These results do not only confirm that the magnetic ILs are potential carriers of MRFs but also provide a new way to improve the stability and magnetic response of MRFs for various applications.

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 (

Two-dimensional materials have already been considered as promising microwave absorbing materials due to their unique and charming layered structure. However, it is difficult to achieve excellent absorption performance at a thin thickness. Herein, the polyhedral Fe3O4 was prepared in-situ using sheet-shaped carbonyl iron powder, which not only retained the sheet-like structure of carbonyl iron powder but also formed polyhedral Fe3O4 on the surface. By tuning the ratio of Ti3C2TX/carbonyl iron powder/Fe3O4 microwave absorption capabilities in terms of the minimum reflection loss (RL) value and absorber thickness could be readily optimized. This result is verified by the explanation of the quarter-wavelength law and impedance matching degree. Specifically, when the thickness of the C–F–M 10% composite material is 2.2 mm, the minimum RL value at 9.16 GHz is − 52.1 dB, and the effective absorption bandwidth is 3.32 GHz. The thickness of the C–F–M 15% composite is 2.0 mm, the minimum RL value at 11.12 GHz is − 49.9 dB, and the effective absorption bandwidth is 4.59 GHz. Therefore, Ti3C2TX composite material is expected to become a candidate material for ultra-thin and lightweight absorbers.

A genetic algorithm was employed as a novel method to determine the best combination of materials for a double-layer electromagnetic shielding composite with good electromagnetic wave absorption efficiency at high frequencies from numerous magnetic materials. A carbonyl iron soft magnetic composite and a flaky FeNi soft magnetic composite were used to form the double-layer composite. The reflection and transmission parameters of the double-layer composite were measured using a vector network analyzer. The electromagnetic shielding effectiveness (SE) of the double-layer composite was calculated and analyzed. The double-layer composite was composed of two shielding materials with different electromagnetic parameters and demonstrated an excellent electromagnetic SE greater than 20 dB above 4 GHz; the ratio of the absorption efficiency (SEA) to SE (SEA/SE) was greater than 0.95, which indicates that more than 95% of the electromagnetic waves at high frequencies were attenuated by the shielding material, rather than being scattered into the surrounding environment. The double-layer composite exhibits excellent performance toward high electromagnetic waves absorption during the EMI shielding process.

Self-heating and dynamic mechanical behavior of isotropic silicone rubber composite (SRC) filled with micro-sized carbonyl iron particles (CIPs) subjected to cyclic compressive loading have been studied. Effects of pre-strains from 5 to 20%, strain amplitudes from 1 to 5%, and excitation frequencies from 10 to 50 Hz on the self-heating and dynamic mechanical response of the isotropic SRC were investigated. The self-heating temperatures were measured on the surface and at the center of cylindrical SRC specimens. The self-heating temperatures of the isotropic SRC samples showed a fast increase in an initial transient stage and the following isothermal stage. The temperature distribution in the isotropic SRC specimens was non-homogeneous and the temperature decreased from the center to sample edges. The self-heating temperatures of the isotropic SRC increased gradually with raising the strain amplitude and frequency. However, the difference between the internal and surface temperatures was slight for low strain amplitudes and frequencies, while it was significant for high strain amplitudes and frequencies. The temperatures of the isotropic SRC boosted rapidly with increasing the pre-strain to 10% and thereafter gained slightly. Although the isotropic SRC dynamic moduli reduced with the rise of the strain amplitude, they enhanced with increasing the pre-strain and frequency. Besides, the storage modulus of the isotropic SRC varied slightly with time, while the loss modulus reduced markedly especially at the initial period. The decrease in the loss modulus of the isotropic SRC under cyclic compressive loading is attributed to its self-heating temperature rise. A finite element simulation of the heat transfer in the SRC cylinder was conducted. The calculated temperatures in the SRC cylinder were in good agreement with the measured ones at different strain amplitudes and frequencies.

We report on a new class of magnetoactive elastomers (MAEs) based on bottlebrush polymer networks filled with carbonyl iron microparticles. By synergistically combining solvent-free, yet supersoft polymer matrices, with magnetic microparticles, we enable the design of composites that not only mimic the mechanical behavior of various biological tissues but also permit contactless regulation of this behavior by external magnetic fields. While the bottlebrush architecture allows to finely tune the matrix elastic modulus and strain-stiffening, the magnetically aligned microparticles generate a 3-order increase in shear modulus accompanied by a switch from a viscoelastic to elastic regime as evidenced by a ca. 10-fold drop of the damping factor. The developed method for MAE preparation through solvent-free coinjection of bottlebrush melts and magnetic particles provides additional advantages such as injection molding of various shapes and uniform particle distribution within MAE composites. The synergistic combination of bottlebrush network architecture and magnetically responsive microparticles empowers new opportunities in the design of actuators and active vibration insulation systems.

A magnetorheological shear thickening fluid (MSTF) is prepared through adding carbonyl iron particles and Al2O3 abrasives into the traditional shear thickening fluid (STF) to improve low shear stress characteristic of STF in this work. To select the optimal sample as base fluid for MSTF, a series of STFs was pre-prepared and its rheological characteristics were further tested, which contained different concentrations of starch polymer and abrasive. Furthermore, different character parameters of MSTFs, such as magnetic field intensity and carbonyl iron particle’s concentration, were experimentally tested to explore its rheological characteristics. Then, the magnetorheological effect on shear thickening formation of MSTFs was furtherly discussed. Experimental results show that with the same base fluid the viscosity and the shear stress of MSTFs are both higher than of STFs under the action of magnetic field. Moreover, the MSTF exhibits a good shear thickening effect under the weak magnetic field intensity and at low level of iron particle concentration, because the existence of hydrogen bonds and magnetic particle chains makes the shear thickening effect of MSTF enhanced by particle clusters. The results indicate that the MSTFs as polishing fluid contribute to develop a higher efficiency polishing method in the future.

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.

Thermorheological characterizations of magnetorheological (MR) grease thickened with polytetrafluoroethylene (PTFE) and molybdenum disulphide (MoS2) used as an additive for two different greases prepared with 50% (MRG50) and 70% (MRG70) weight fractions of spherical carbonyl iron (CI) particles, respectively, are presented. The magnetic properties and glass transition temperature of prepared MR greases (MRGs) have been measured using vibrating sample magnetometer (VSM) and differential scanning calorimetry (DSC), respectively. The MR properties are investigated at different temperatures ranging from 25 °C to 65 °C at magnetic fields ranging from 0 to 0.75 T under rotational and oscillatory sweep tests using a magnetorheometer. It is observed that for MRG70, the shear stress and apparent viscosity increase with increasing temperature. This is explained based on the formation of monolayers of MoS2 as it interacts with MRG and the effect of thermal conductivity on magnetorheology. Yield stress of PTFE-based MRG has been shown to increase with temperature and magnetic field. Formation of PTFE particle clusters decreasing the localized heat dissipation has been explained to be the reason for this. With increasing magnetic field strength, the flow properties show an increasing trend. ON-state storage and loss modulus are studied to understand the effect of temperature and magnetic field on the viscoelasticity of PTFE-based MRG.

In this paper, we present the procedure for fabricating a new magneto-tactile sensor (MTS) based on a low-cost commercial polyurethane sponge, including the experimental test configuration, the experimental process, and a description of the mechanisms that lead to obtaining the MTS and its characteristics. It is shown that by using a polyurethane sponge, microparticles of carbonyl iron, ethanol, and copper foil with electroconductive adhesive, we can obtain a high-performance and low-cost MTS. With the experimental assembly described in this paper, the variation in time of the electrical capacity of the MTS was measured in the presence of a deforming force field, a magnetic field, and a magnetic field superimposed over a deformation field. It is shown that, by using an external magnetic field, the sensitivity of the MTS can be increased. Using the magnetic dipole model and linear elasticity approximation, the qualitative mechanisms leading to the reported results are described in detail.

In this work, a highly efficient and environmentally friendly method for extracting palladium from hydrochloric acid media was developed. The method uses a magnetic sorbent carrying an organophosphorus extractant, which is not washed from the sorbent into the aqueous phase. The extractant was characterized by 1H, 13C, and 31P NMR spectroscopy and MALDI TOF mass spectrometry, and the palladium complex based on it was characterized by IR spectroscopy. According to an in vitro microbiological study, the extractant was non-toxic to soil microflora. It was established that the water uptake and saturation magnetization of the magnetic sorbent were sufficient for use in sorption processes. The sorption efficiency of palladium(II) with the developed sorbent can reach 71% in one cycle. After treatment of the spent sorbent with 5 M hydrochloric acid, palladium was completely extracted from the sorbent. The new sorbent is proposed for the extraction of palladium from hydrochloric acid media obtained by the leaching of electronic waste.

This study investigates dynamic mechanical properties and creep and recovery behaviors of disc-shaped magnetic Fe3O4 nanoparticles with carbonyl iron (CI) flake-shaped microparticles in water-based MR fluid. The experimental study is performed using a parallel plate rheometer. Dynamic performance and creep and recovery behaviors help understand deformation mechanism for its practical applications in MR devices like seismic vibration control, active dampers, earthquake dampers, etc., under applied strain, and stress levels. The oscillatory experiment reveals a transition from viscoelastic-to-viscous behavior at the critical strain of 0.1%. The storage modulus [Formula: see text] of CI/Fe3O4 MR fluid showed a stable plateau region over the small strain area and storage modulus [Formula: see text] independent of strain amplitude. The frequency experiment demonstrated that storage moduli [Formula: see text] exhibit elastic response and stable plateau region over the complete external frequency range, suggesting the distinguished solid-like behavior of the MR fluid. Creep and recovery experiments showed that fluid acts as a linear viscoelastic material at lower stress levels. As the stress levels increase, the contribution of retardation strain and viscous strain decreases, and it acts like nonlinear viscoelastic material. In summary, this work is expected to obtain MR fluid results for application in MR devices under applied strain, frequencies, and constant stress levels.

Magnetorheological fluid (MRF) is an intelligent material, which can be controlled by an external magnetic field. It is widely used in damping, finishing, mechanical transmission, sealing, and other engineering fields due to its magnetorheological (MR) effect. However, despite decades of research and experimental development, the wide application of MRF is still restricted by its serious settlement problem owing to the density difference between the magnetic particles and carrier liquid. Here, using the coprecipitation method, a kind of Fe3O4-modified nanolignocellulose (Fe3O4/NLC) composite fiber was characterized by its unique advantages such as low density, soft magnetism property, and high specific surface. These Fe3O4/NLCs were used as a kind of reinforcing particle with carbonyl iron powder in the new bidisperse MRF system. The performances of MRF samples were enhanced by these superior properties. We found that all MRF samples with composite fibers exhibited excellent antisettlement and dynamic mechanical characteristics and cooperativity between Fe3O4 and NLCs. Furthermore, redispersibility of MRF is qualitatively evaluated by a shearing test in this paper, explaining the high property of antihardening. This composite fiber improves the comprehensive performance of MRF and has the potential to be repeatedly used in engineering applications.

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.

Nanoparticles of nonstoichiometric magnetite obtained by controlled oxidation of carbonyl iron (α-Fe) in water are studied. The Fe : H2O mole ratio is 3 : 4, 4 : 4 and 3 : 10. The particles are synthesized in a high-power Activator 2S mill in an air atmosphere by 24-h milling. X-ray diffraction and spectrum analyses of the synthesized magnetite nanoparticles are performed. Formulas describing the crystal chemistry of the nanoparticles are derived using the data of Mossbauer spectroscopy. The magnetic properties and the microstructure of the nanoparticles are studied.

Abstract Magnetorheological fluids are obtained on the basis of star-shaped and linear PDMS containing 70, 75, and 80 wt % of carbonyl iron microparticles. While pure PDMS polymers are Newtonian fluids, composites exhibit pseudoplasticity. The viscoelastic properties of the obtained magnetorheological fluids of different composition are studied in magnetic fields up to 1 T. The viscosity and storage modulus of the magnetorheological fluids in the maximum magnetic field reach ~0.19–0.65 MPa s and 0.4 MPa, respectively. The relative increase in the viscosity and storage modulus of the magnetorheological fluids based on the star-shaped PDMS with a magnetic filler concentration of 70 wt % in a magnetic field exceeds four orders of magnitude. In the magnetic field, the yield stress of the magnetic composites is as high as 70 kPa at a magnetic field strength of 1 T.

In this work, the rheological response and sedimentation stability of micron-sized flake-shaped carbonyl iron (CI) water-based magnetorheological (MR) fluid were investigated using iron nanopowder with hydrophilic carbon shell as an additive. The rheological behaviors of MR fluid containing 1 wt% iron nanopowder were measured with and without a magnetic field under shear rate, shear strain, and shear stress sweep mode using a parallel plate rotational rheometer. The magnetic field strength was varied from 0 to 131 kA/m, and in the presence of magnetic field strength, micron flake-shaped CI and iron nanopowder particles lead to form a robust columnar structure. It was observed that using 1 wt% of iron nanopowder with hydrophilic carbon shell, the rheological responses and sedimentation stability of MR suspension were enhanced. We fitted the shear stress as a function of shear rate curves using the Bingham-plastic flow model, which shows a good agreement with the experimental results. We find that yield stress obtained in shear rate sweep mode was larger than that in the shear strain and shear stress sweep mode because, in shear strain and shear stress mode, the responding strain (or stress) may be unable to follow the stress (or strain) applied and a smaller value of strain (or stress) was observed. The amplitude sweep reveals a transition from viscoelastic-to-viscous behavior at the critical strainγcrt = 0.1%. The storage modulus (G') of the MR fluid showed a stable plateau region over the small strain area γ ≤ γcrt and G'independent of strain amplitude. The frequency sweep demonstrated that storage moduli (G') exhibit elastic response and stable plateau region over the entire frequency range, suggesting the distinguished solid-like behavior of the MR fluid.

Particle oxidation constitutes a serious ageing phenomenon in magnetorheological suspensions, bringing about deterioration in performance. This study describes commercial carbonyl iron particles that were successfully coated with poly(amidoamine) dendrons and then applied as an oxidation-resistant dispersed phase in magnetorheological suspensions. A synthesis method was adhered to whereby the particles were sequentially treated with ethylenediamine and methyl acrylate, leading to the formation of generation 2 and 2.5 dendrons; these had the capacity for composite particles with a nano-scale dendritic layer to be prepared on their surfaces. Success in applying the coating was confirmed by various techniques, including XPS, TEM, EDX, FTIR and Raman spectroscopy. The controlled approach adopted to coating the carbonyl iron particles resulted in them exhibiting sufficient oxidation stability, with only an ~ 4.5–4.7% decrease in saturation magnetization. Of interest was that their magnetorheological suspensions demonstrated ca 4.8% and 4% higher dynamic yield stress than a suspension based on non-modified particles at the highest intensity of magnetic field investigated, i.e. 438 kA m–1. Notably, sedimentation stability was evaluated by a unique method that involved the use of a tensiometer with a specific testing probe. The aforementioned coating process led to enhanced sedimentation stability of the magnetorheological suspensions based on coated particles possibly due to decrease in the overall density of the particles, enhanced dispersion stability and reduction in the size of their agglomerates in the silicone oil mixtures that were confirmed by optical microscopy. Modification of the particles as proposed has the potential to overcome one of the primary drawbacks of magnetorheological suspensions, this being oxidation instability (which leads to what is referred to as “in-use-thickening”), without negatively affecting their performance in the presence of a magnetic field.

Self-healing magnetic polyurethanes have been fabricated with 4,4′-methylene diphenyl diisocyanate (MDI), poly(1,4-butylene adipate) (PBA-2000), furfurylamine (FMA), bismaleimide (BMI), and magnetic materials (magnetite, carbonyl iron, and magnetite-coated carbonyl iron which was prepared by a vortex mixer in a solid-state process). The magnetic polyurethanes have three properties of self-healing, thermal radiation shielding, and reducing the temperature of the retro Diels–Alder reaction. The magnetic polyurethanes showed the self-healing performance of a notch at 110 °C in a short time, the self-healing recovery was 82.1% in the breaking strength after the healing process, and the excellent thermal radiation shielding. The polyurethanes were investigated by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), optical microscope (OM), ultraviolet–visible (UV–Vis) spectroscopy, tensile testing, and thermal conductivity. Finally, the self-healing magnetic polyurethanes which with the properties can be promising materials for the building or the constructing applications in the future.

The electrical and thermal conductivity of the ternary epoxy composites (CMs) with two-component fillers, multiwall carbon nanotubes (MWCNT)/TiO2, and MWCNT/carbonyl iron (Fe) have been investigate...

Thermal effect in absorbing composite is concerned gradually due to electromagnetic environment tends to high power, high frequency and wide bandwidth. Microstructure characteristics and some basic material properties of carbonyl iron powder/silicone rubber (CIP/SR) are obtained by experiments method. Complex permittivity and permeability of CIP/SR composite as an absorbing material is measured by the vector network analyzer. CIP/SR composite with 78 wt% particles filling exhibits excellent absorption performance in C and X band. A numerical model coupled with electromagnetic wave, heat transfer and mechanics theory is presented to study the thermal effect and mechanical damage of absorbing composite under microwave radiation. Microwave heating and attenuation mechanism of CIP/SR composite are discussed. Electric field, temperature, stress and deformation in CIP/SR composite are quantitatively characterized. The results indicate temperature distribution relates to electric polarization and hysteresis loss. Temperature of CIP/SR composite increases by 36 °C as microwave radiation lasts 2 s at 9.37 GHz. Thermal expansion and stress concentration will be aggravated as frequency increases.

Toroid-shaped Fe-based soft magnetic powder cores (SMPCs) were prepared by cold pressing commercial FeSiCr and carbonyl iron powder (CIP) insulated with epoxy resin. The effect of the CIP mass ratio on the magnetic properties of powder cores, which included the dependences of the effective permeability (μe), DC bias characteristic, and core loss (Pcv), was investigated. By optimizing the CIP content, the μe of the magnetic powder cores reaches 31 when the CIP content is 30 wt%, and it exhibits a stable permeability in the frequency range up to 1 MHz. Meanwhile, the DC bias characteristic increases to 78%, and the Pcv is minimized to 1684 mW/cm3, which is reduced by 15% at 50 mT and 250 kHz.

Fe-powder and paraffin-based or similar systems are widely used for low-temperature injection molding. The main attention of research efforts on such compositions is focused on the study of their rheology. At the same time, such materials can be adapted for 3D printing by layer-by-layer surfacing, requiring only necessary rods or filaments with a sufficient level of mechanical properties so as not to break during printing. Hence, this paper examines the influence of paraffin content on the compressive strength of samples made of carbonyl iron powder and paraffin in the ratio: 50/50, 60/40, 70/30, and 80/20 vol.%. Computer calculations of critical deformation, elasticity modulus, and compressive strength of such composites have been performed. According to the examination and calculation results, the modulus of elasticity varies from 1358 to 113 MPa with a higher paraffin content, the critical deformation ranges between 0.257 and 3.310, and the compressive strength is between 0.339 and 0.761 MPa. Iron powder was mixed with paraffin in a planetary mill for 3 min with a subsequent sieving of the mixture. Afterward, pressed cylindrical samples with a volume of ~1 cm3 and a height of ~10 mm were used to determine the density and compressive strength. It was found that the density of the samples after pressing is 1.3 times lower than the calculated by the additivity formula at a binder content of 20 vol.%. Only when the binder content increases to 50 vol.%, the actual density approaches the calculated values, that is, the relative porosity varies from 0.212 to 0. With an increase in paraffin content from 20 to 50 vol.% the strength of the samples increases along the concave curve from 3 to 11 MPa. The dependences of the calculated and experimentally obtained compressive strength are similar, indicating the adequacy of the established models. However, significant variation in values is due to the difference between the properties of paraffin under study and that used for testing. Samples of rods with 40 and 60 vol.% Fe was extruded and tested by 3D printing. The obtained experimental data can be used in the creation of other similar working materials for 3D printing in the layer-by-layer surfacing.

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.

Composites made up of microparticles embedded in a polymeric matrix have attracted increasing attention due to the possibility of tailoring their physical properties by adding the adequate quantity of fillers. As the concentration of these fillers increases, their connectivity changes drastically at a given threshold and therefore the electrical, thermal and optical properties of these composites are expected to exhibit a percolation effect. In this work, the thermal and electrical conductivities along with the emissivity of composites composed of carbonyl-iron microparticles randomly distributed in a polyester resin matrix are measured, for volume fractions ranging from 0 to 0.55. It is shown that both the thermal and electrical conductivities increase with the particles’ concentration, such that their percolation threshold appears at volume fractions of 0.46 and 0.38, respectively. The emissivity, on the other hand, decreases as the fillers’ concentration increases, such that it exhibits a substantial decay at a volume fraction of 0.41. The percolation threshold of the emissivity is thus higher than that of the thermal conductivity, but lower than the electrical conductivity one. This dispersion on the percolation concentration is justified by the different physical mechanisms required to activate the electrical, thermal, and optical responses of the considered composites. The obtained results thus show that the percolation phenomenon can efficiently be used to enhance or reduce the physical properties of particulate composites.

Here we explore the electronic structure of the diiron complex [(dppf)Fe(CO)3]0/+ [10/+; dppf = 1,1'-bis(diphenylphosphino)ferrocene] in two oxidation states by an advanced multitechnique experimental approach. A combination of magnetic circular dichroism, X-ray absorption and emission, high-frequency electron paramagnetic resonance (EPR), and Mossbauer spectroscopies is used to establish that oxidation of 10 occurs on the carbonyl iron ion, resulting in a low-spin iron(I) ion. It is shown that an unequivocal result is obtained by combining several methods. Compound 1+ displays slow spin dynamics, which is used here to study its geometric structure by means of pulsed EPR methods. Surprisingly, these data show an association of the tetrakis[3,5-bis(trifluoromethylphenyl)]borate counterion with 1+.

In this study, micron-sized flake shaped carbonyl iron (CI) water-based MR fluids were prepared with adding laponite and oleic acid as an additive and surfactant, respectively. The MR suspensions are comprised of the fixed CI particles and water weight %, while weight % of laponite and oleic acid changes from 1 to 3 wt% and 0.5 to 1.5 wt%, respectively. The remarkable enhancement in magnetorheological properties was obtained with improved sedimentation stability for CI/water MR suspensions with the addition of laponite and oleic acid. It was found that at the lowest magnetic field strength, the higher laponite concentration is effective, while at the highest magnetic field strength, the smaller concentration was effective. It was because of the combined effect of the field-induced CI chains and the laponite clay gel network. Its storage moduli showed a stable plateau area for whole angular frequencies, suggesting distinguished solid-like behavior of the MR fluid. Finally, a novel correlation was obtained between the initial settling rate of the CI particles and magnetorheological behavior of CI/laponite/OA MR suspensions with 1 wt% laponite and 0.5 wt% oleic acid, which has less zero-field, high on-state shear stress with enhanced sedimentation stability. The prepared MR fluids are a reliable industrial application vibration-isolation, clutch, and brake.

This work examines magneto-rheological elastomers (MREs) based on isotropic and anisotropic distribution of carbonyl iron particles (CIP) in natural rubber (NR) and acrylonitrile butadiene rubber (NBR). Measurements of the compressive mechanical properties were done to determine the isotropic and anisotropic properties of the MREs. Scanning electron microscopy (SEM) and optical microscopy were employed to study the CIP filler mixing behavior in the rubber matrix and orientation of particles in an anisotropic state. CIP-NBR composites show higher ultimate compressive stress in both isotropic and anisotropic states than NR-based composites. NBR-based composites show positive increases in both the elastic modulus and compressive stress at higher deformation when changing from isotropic to anisotropic, whereas NR-based composites show a positive increase in the elastic modulus and a decrease in the compressive stress. Elastic modulus measurements of anisotropic composites under a magnetic field suggest that NBR composites have much better field-dependent magnetic properties than NR composites. Anti-stress-relaxation measurements indicate that NBR composites have better magnetic effect than NR composites. The better performance of NBR-based anisotropic composites in field-dependent and independent behaviors might be due to better filler distribution, a greater number of chain-like filler structures, and less aggregation of the chain-like filler strands. The MREs based on NBR could be more useful than NR for wide range of magneto rheological applications.

This work describes the influence of VK carbonyl iron powder on the properties of 60Kh2N steel powder. It has been demonstrated that addition of the VK powder to sprayed powder of grade PZhRV 2.200.26 in an amount up to 15% makes it possible to increase the tensile strength from 417 to 482 MPa because carbonyl iron in combination with carbonyl nickel powder in coarse pores between the particles of sprayed iron forms a sintered frame, which positively influences the strength of the obtained material. The mechanical properties of this steel have been improved by hot rolling with subsequent annealing in a protective environment. As a consequence of this additional treatment, the ultimate tensile strength reached 595 MPa.

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.

Although smart materials, specifically magnetorheological (MR) fluids, have shown remarkable practical importance, their drawbacks such as an aggregation of magnetic fillers, insufficient compatibility with the carrier liquid, low resistance to corrosion and poor sedimentation stability still cause severe limitations for their broader utilization. To address this challenge, our study presents a facile concept for the coating of magnetic particles, leading to their enhanced utility properties and sufficient MR performance. This concentrates on the coating of magnetic carbonyl iron (CI) particles with a thin modifying layer as a surface shell utilizing four organosilanes; tetraethoxysilane, (3-aminopropyl)triethoxysilane, bis[3(trimethoxysilyl)propyl]amine and vinyltrimethoxysilane. Characterization of the modified particles and their suspensions was examined using various methods. XPS analysis confirmed the successful particle modification, while the surface free energy was evaluated by tensiometric measurements reflecting the better compatibility of particles with the dispersing medium. The lowest surface free energy possessed particles modified with (3-aminopropyl)triethoxysilane. The magnetization of the modified core-shell particles was not negatively affected by the organosilanes layer present on the particles resulting in comparable MR performance of the systems based on pure CI particles and their modified analogues as was proved by the fitting of the corresponding flow curves by the Robertson-Stiff model. Moreover, the modification of the particles improved their thermo-oxidation stability and chemical stability investigated via thermogravimetric analysis and acidic tests, respectively. Finally, the sedimentation stability of the modified particle-based systems expressed as a weight gain measured using a tensiometer device was enhanced in comparison with the pure CI particle-based system, which can be very positive in the intended applications.

With the development of mould manufacturing industry, the high precision polishing technologies of Ni–P-coated SKD11 steel are in high demand. In this work, the factors influencing the magnetic material polishing process were determined by investigating the force distribution of carbonyl iron (CIPs) and abrasive particles (APs) in the working surface of magnetorheological fluid (MRF). The influence of certain factors, such as the diameters of the CIPs and the APs and the current and working distance (K), on the polishing surface quality, was assessed by fuzzy grey and Taguchi analysis. Results showed that the values of the fuzzy grey relationships with the surface quality of the factors were 0.4914, 0.7797, 0.6686 and 0.7461. Result showed that the fuzzy grey relationship point of factors known as diameters of the AGs had the most remarkable influence on the polishing effect, and the effect of CIP diameter was insignificant. The MRF contained commercially available CIPs that had been successfully applied for polishing the surface of magnetic materials with extremely high accuracy (surface roughness Ra = 0.561 nm) without leaving scratches on the surface after polishing.

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.

This study deals with the development of a printable composite material based on a polyphenylene sulfide (PPS) matrix and carbonyl iron (Fe) particles, with controlled electromagnetic performance. More specifically, materials were simultaneous melt mixed and shaped under the form of filament with a diameter suitable for Fused Deposition Modeling. After reminding the potentialities of the printable PPS matrix, especially in terms of temperature resistance, microwave characterizations were performed on toroidal samples. The measured electromagnetic properties were compatible with absorption applications and compared to those of a commercial iron-filled PolyLactic Acid (PLA). Rectangular waveguide microwave loads were designed and fabricated by Fused Deposition Modeling with both materials. The PPS-Fe load has a volume that is 7 times lower than the PLA-Fe load due to a higher permittivity-permeability product and losses. Heat treatments demonstrated that no degradation is observed for the PPS-Fe load up to 180 ℃ while the PLA-Fe load is totally melted at 150 ℃. In the same time, it was observed that the maximum power supported by the PPS-Fe load is three times higher than the one supported by the PLA-Fe load. Finally, the temperature stability of the electromagnetic response of the PPS-Fe composite was demonstrated by measurements in the −70 ℃ to 140 ℃ temperature range. This new high temperature printable composite paves the way to the development of efficient, low-cost, low-weight, power and temperature stable absorbers for microwave applications.

In this study, magnetizable polyurethane sponges (MSs) were obtained from commercial absorbent polyurethane sponges (PSs) doped with carbonyl iron microparticles (CIPs). Based on MSs, we manufactured cylindrical capacitors (CCs). The CCs were subjected to both a magnetic field and an alternating electric field, with a frequency of f=1 kHz. Using an RLC bridge, we measured the series electric capacitance, Cs, and the tangent of the loss angle, Ds. From the functions Cs=Cs(δ)CCs and Ds=Ds(δ)CCs, we extracted the components of the complex dielectric permittivity. It was found that the CIPs embedded in the MS matrix aggregated, leading to magneto-dielectric effects such as the enhancement of the complex dielectric permittivity components when applying the magnetic field as a principal effect and the enhancement of the electric capacitance and time constant of the capacitors as a secondary effect. The obtained results represent landmarks in the realization of low-cost magnetic field sensors, deformation and mechanical stress transducers in the robotics industry, etc.

To investigate Haematinic definitions accessible in India arcade for their assortments of measurements structures, hard salts utilized, the substance of essential iron, recurrence of organization compulsory, the occurrence of extra supplements, levelheadedness and price. Haematinic details recorded in IDR 2018, were investigated for salts of Iron present. Arrangements of ferrous fumarate were additionally investigated for Iron substance, presence of folic corrosive and other included extra parts. A sum of 522 plans, 291 (55.74%) was oral strong measurement structure, 206 (39.46%) were oral fluids and 25 (4.7%) were parenteral. Iron salts in these details were in a type of ferrous fumarate, carbonyl iron, iron ascorbate, iron ammonium citrate, ferric hydroxide polymaltose perplexing, ferrous sulfate, sodium hydrate. Carbonyl iron was available in 92 arrangements and was most ordinarily utilized readiness in oral strong plans. A few details moreover contained Vitamin B12, zinc sulfate, histidine, lysine different multivitamins and calcium arrangements in factor extent. Out of 291 oral strong, 45 (15.46 %) arrangements required organization > three times each day to accomplish the remedial fixation. The normal expense of the sound planning was more than the normal expense of silly arrangement. Investigation of different haematinics shows there is no consistency in details. Iron and folic corrosive are included wide factor range in addition, different substances were additionally included with no very much demonstrated proof. Steps ought to be taken to normalize these details.

To analyze the effect of magnetite Fe3O4 disk-shaped nanoparticles with flake-shaped microparticles in water-based magneto rheological (MR) suspension, the rheological properties were studied using a parallel plate rheometer. The morphology, crystallinity, and magnetic property of the prepared MR suspensions were examined by field emission scanning electron microscopy (FESEM), X-ray diffraction, and vibrating sample magnetometer, respectively. In the presence of a magnetic field, micron-sized carbonyl iron (CI) particles lead to form a robust columnar structure with Fe3O4 nanoparticles and enhanced the magnetorheological performances. The magnetorheological performances of MR suspensions were examined in shear rate, shear strain, and shear stress testing sweep modes with and without a magnetic field. It was observed that adding the 1 wt% of Fe3O4, the magnetorheological performance of MR suspension enhanced. The MR fluid with CI/Fe3O4 nanoparticle mixture showed significantly higher shear viscosity and shear stress and yielded stresses than pure CI-based MR fluid. The yield stresses were higher in the shear rate sweep mode than strain and stress sweep testing modes.

A high-performance soft-magnetic composite (SMC) has been successfully fabricated in a toroidal mold without the application of compaction pressure by mixing three different alumina-coated Fe-based metal powders, namely carbonyl iron (FM), Fe-Si-Cr alloy (FSC), and Fe-Si-Al alloy (sendust), with epoxy resin in a centrifugal paste mixer. Surface coating with an alumina layer was performed via a sol–gel process, and its thickness was controlled by varying the coating time. Without the alumina coating, the SMC toroidal core with a FM:FSC:sendust mixing ratio of 8:22:70 by mass exhibited optimal magnetic properties including an effective permeability (μeff) of 33.9 and total core loss (Pt) of 252 mW/cm3 at 100 kHz with an amplitude (B) of 50 mT. With the alumina coating, however, the SMC toroidal core with the same mixing ratio exhibited a significantly reduced Pt value of 213 mW/cm3 while its μeff value was slightly decreased to 32.4, primarily due to the suppression of the macroscopic eddy-current loss from 115 mW/cm3 to 85 mW/cm3. These results indicate that an optimal mixture of the three different alumina-coated Fe-based metal powders is very effective for fabricating high-performance SMC cores without external pressure for molding, being applicable for miniature electronic components.