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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 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 (

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.

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.

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.

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.

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.

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.

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.

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.

Oriented flaky carbonyl iron and MoS2/polyurethane (FCI & MoS2/PU) composite with wide absorption bandwidth at thin thickness was successfully prepared by shear force. The morphology, electromagnetic, and microwave absorption properties in the frequency of 2.6–18 GHz of the composites were investigated. It was observed that the flaky FCI and MoS2 particles became orienting along the tape-casting direction under shear force and parallel to each other. Compared with the un-oriented FCI & MoS2/PU composite, the higher complex permittivity and permeability were obtained after oriented, which was superior in achieving improved microwave absorption performance at thin thickness. Wider absorption bandwidths of reflection loss (RL) values below − 5 dB were obtained at the thin thicknesses of 0.5–1.2 mm for the oriented FCI & MoS2/PU composite. It suggests that the orientation by shear force is a promising approach for the preparation of materials with good microwave absorption property at thin thickness.

In the present study, development of a novel oriented polymeric composite comprising of Polycaprolactone (PCL) polymer and carbonyl iron filler particles (CIP) is presented. Incorporation of permanent magnets into solvent based extrusion 3 D printing set up produced the oriented polymeric composites. The microwave absorption properties of the oriented composite were investigated and compared with non-oriented composite and pristine PCL by utilizing vector network analyzer (VNA) and Nicolson-Ross-Weir (NRW) methodology. Higher values of permeability, permittivity, dielectric loss and magnetic loss of the oriented composite indicated the micro capacitor behaviour and domain wall motion of the parallel aligned CIP chains in the PCL matrix. The reflection and transmission loss values for the oriented composite were found to be -34 dB and -26 dB respectively. The microwave absorption of the oriented PCL/CIP composite was found to be approximately 93% suggesting the efficacy of the 3 D printed oriented composite as an excellent microwave absorber.

The use of magnetic abrasive machining in the production of components for gas-turbine airplane engines is considered. The abrasive machining of a titanium alloy, high-speed steel, and a hard WC–Co alloy by means of a suspension of diamond powder and carbonyl iron particles in a hydrocarbon liquid is analyzed.

Gelatin-based systems have great potential in bio-medical applications. Here, we report the solvent uptake and DC conductivity of glutaraldehyde-crosslinked gelatin hydrogels and ferrogels. Both the parameters are found to depend on cross-linker (glutaraldehyde) and dopant (carbonyl iron) concentrations. Higher cross-linker proportions cause decrease in solvent uptake, equilibrium swelling ratio and DC conductivity. Solvent uptake is seen to increase while equilibrium swelling ratio and DC conductivity decrease with dopant concentration in the ferrogels. The solvent uptake and DC conductivity behaviour of the studied systems are explained on the basis of variations in pore size and polymer segmental mobility which, themselves, are functions of cross-linker and dopant concentrations. The diffusion process in the hydrogels and ferrogels obeys the second-order kinetic model.

In the present work, a solvent-based extrusion 3D printing technique has been utilized to fabricate polymer composites comprising of polycaprolactone (PCL) polymer and carbonyl iron particles. A homogenous composite ink containing PCL and carbonyl iron filler particles with suitable solvent was synthesized with required viscosity for the 3D printing operation. Rectangular samples were successfully fabricated using the extrusion 3D printing technology. A response surface methodology was utilized for planning the set of fabrication experiments so as to estimate the effect of process parameters, namely infill density, printing speed and filler concentration on the printed composite density, percentage of shrinkage and compressive strength. Shrinkage was found to reduce with an increase in infill density and filler concentration. However, density was found to shoot up with an increase in infill density and filler concentration. Similarly, compressive yield strength was improved with an increase in infill density and filler concentration. Increase in shrinkage and density values and decrease in compressive yield strength value were noticed with an increase in the printing speed. Furthermore, a genetic algorithm multiobjective optimization tool was utilized to obtain optimum process parameters to minimize shrinkage, minimize density and maximize compressive yield strength for the electronics and microwave applications of the fabricated composite. A microwave shielding performance test of the developed composite was also carried out as a case study. The shielding performance test indicated the efficacy of the polymer composite fabricated using solvent-based extrusion 3D printing technique.

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

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

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

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

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

The finishing accuracy and efficiency of magnetic abrasive finishing (MAF) are mainly depending on magnetic abrasive powders (MAPs). A new kind of core–shell structured carbonyl iron powders (CI-MAPs) with a hard Fe/Al intermetallic shell for magnetic abrasive finishing is successfully synthesized by in-situ alloy-hardening the surface of spherical carbonyl iron powders in this study. The feasibility of such an in-situ alloy-hardening strategy is theoretically designed according to the Fe/Al intermetallic compound formation chemical reaction using the Gibbs free energy principle and the TG-DSC testing, and thus the experimental thermodynamics temperature and time ranges of such chemical reactions are proposed. Experimental results shown that a densely zigzag-like uniform alloy-hardening layer with a thickness of about 11 μm, which are composed of Fe3Al, FeAl, and Fe2Al5 intermetallic compounds, was in-situ chemically synthesized on the surface of the spherical carbonyl Fe powders. The achieved core–shell structured powder is performed to finishing a Zirconium tube experimentally, and the roughness (Ra) of the Zirconium tube is greatly improved from 0.361 μm to 0.085 μm by 3 MAF passes.

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

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

This paper presents the effect of the micro-sized particles on the storage modulus and durability characteristics of magnetorheological elastomers (MREs). The initial phase of the investigation is to determine any associations among the microparticles’ weight percent fraction (wt%), structure arrangement, and the storage modulus of MRE samples. In order to carry out this, both isotropic and anisotropic types of MRE samples consisting of the silicone rubber matrix and 50, 60, 70, 75, and 80 wt% microparticles of carbonyl iron fractions are prepared. It is identified from the magneto-rheometer that the increase in storage modulus and decrease in linear viscoelastic region limit are observed in varying consistency depending on wt% and particle arrangement. The consistency of this dependency feature is highlighted by superimposing all of the graphs plotted to create the proposed the samples’ behavior model. In response to increasing magnetic stimulation, a sample of 70 wt% microparticles with an isotropic arrangement is found to be significant and stable. The experimentally defined fraction is then used for the durability test as the second phase of the investigation. During this phase, the durability evaluation is subjected to stress relaxation for an extended period of time. After undergoing durability testing, storage modulus performance is decreased by 0.7–13% at various magnetic stimulation levels. This result directly indicates that the storage modulus characteristics of different forms of MRE are sensitive to the different iron particle fractions’ and microparticles’ alignment. Therefore, important treatments to alter the storage modulus can be undertaken before the practical implementation to accommodate any desired performance of MRE itself and MRE application systems.

Magnetorheological fluids (MRFs) are peculiar of smart fluids whose rheological properties can be efficiently controlled by varying applied magnetic field. Owing to this peculiar property, it can be utilized in industrial applications in semi-active devices such as dampers, actuators, etc. In this work, an effort has been attempted to produce MRFs using natural oils as carrier fluids and tested for potential replacement of conventional carrier fluids such as silicone oil. The MR fluids are prepared using silicone oil and two natural oil namely Mahua oil and Simarouba oil. Carbonyl iron (CI) and Electrolytic iron (EI) are used as suspended particles with lithium grease as an additive. The MRF using two natural based oil are known as Green magneto rheological fluids (GMRF). The characterization of suspended particles and carrier liquids was performed, followed by tests on sedimentation stability of prepared samples. To compare the sedimentation stability, the graphs of sedimentation ratio versus time are plotted for all MR fluids samples. It is found that the sedimentation stability of natural oils based MRFs are relatively better than silicone oil based MRFs for the same concentration of magnetic particles. There is potential of these natural oils based MRFs to replace the conventional MRFs However, other rheological properties like yield strength, flow characteristics etc. needs further investigation.

Single-layer and double-layer polyurethane (PU) matrix coatings containing spherical carbonyl iron (SCI) and flaky carbonyl iron (FCI) were designed and prepared by using a simple and effective manufacturing method, and the thickness of the coatings was kept at 1.5 mm. The complex permittivity, complex permeability and absorption properties of the coatings were investigated in the frequency range of 2–18 GHz. The results indicate that all the single-layer and double-layer coatings exhibit excellent absorption properties and wide absorption bands. By optimizing the filler radio and coating structure, the optimal reflection loss (RL) value can reach − 35 dB at 8.6 GHz and make the widest absorption band reach 15.5 GHz (2.5–18.0 GHz) and 4.9 GHz (10.7–15.6 GHz) for RL

Low-frequency microwave absorption remains a key issue to plague the attenuation of electromagnetic energy in conventional absorber. In this work, lightweight and flexible composite textiles were fabricated by in situ synthesis method. The microstructure and electromagnetic properties of the composite textiles were studied. The carbonyl iron/reduced graphene oxide/non-woven fabric (NW-RGO-CI) composite textiles possess excellent microwave absorption performance at low frequency range (2.91–5.1 GHz), and the qualified bandwidth of the composites reaches 9.2 GHz, which originates from synergistic effect of electricity and magnetism. The as-fabricated flexible and lightweight composite textiles could serve as potential materials in wearable electromagnetic absorption coatings and devices.

This paper presents material characteristics of a rigid magnetorheological (MR) foam that comprises polyurethane foam matrix and carbonyl iron particles (CIPs). Three different samples of MR foams are prepared by changing the concentration of CIPs (0, 35, and 70 g) in isotropic condition. In-depth characterization on the morphological properties, the field-dependent rheological behavior in terms of linear viscoelastic region and storage modulus, and the off-state sound absorption properties are then experimentally investigated. In the morphological observation, it is seen from the fluorescence micrographs that MR foam consists of open pore structure and the average size of the pores is decreased with the increment in CIPs content. In the rheological test of MR foam, it is identified that MR foam with the addition of 70 g of CIPs to the total of polyol and isocyanates (100 g) can enhance the storage modulus up to 112% compared with MR foam without CIPs. In the meantime, from the acoustic absorption test, it is shown that the maximum peaks of sound absorption coefficient (SAC) are shifted to the low frequency and the SAC is increased up to 229% due to the decrement in the pores size and increment in the storage modulus. The results achieved from this material characterization of MR foam provide useful guidelines for the development of new type smart materials associated with MR fluids and for the findings of appropriate applications which require controllability of both the stiffness and acoustic properties.

Biopolymeric Arabic gum (AG) coated carbonyl iron (CI) particles were synthesized using a solvent casting process, and then their coating was confirmed using scanning electron microscopy analysis. Thermal property and chemical structure of the produced AG coated CI particles were investigated by thermalgravimetric analysis and Fourier transform infrared spectroscopy. In addition, from the measurement using vibration sample magnetometer, magnetic properties including saturation magnetization were also observed. The magnetorheological (MR) fluid was prepared by dispersing CI/AG particles in silicone oil and then its typical MR behaviors of shear stress and shear viscosity were compared to those of the pure CI suspension. Sedimentation stability of the CI/AG based MR suspension was observed to be improved compared to that of the pure CI suspension according to the Turbiscan test.

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.