Surface Of Carbonyl Iron Particles Research Articles

Atom Transfer Radical Polymerization of 2-Isopropenyl-2-Oxazoline in Solution and from the Surface of Carbonyl Iron Particles toward Fabrication of a Cytocompatible Magneto-Responsive Hybrid Filler

Atom transfer radical polymerization (ATRP) of 2-isopropenyl-2-oxazoline was optimized both in solution and initiated from carbonyl iron (CI) particle surface (SI-ATRP) in order to obtain polymers with well-defined molar mass and narrow dispersity. The polymerization procedure was thoroughly investigated by size exclusion chromatography and 1H NMR and optimized from the point of view type of initiator, ligand, copper catalyst, and solvent. Finally, the poly(2-isopropenyl-2-oxazoline) (PIPOx) with controlled molar masses up to 20,000 g/mol and dispersity in the range of 1.2–1.5 were successfully prepared, while high conversions could be reached. Polymerization conditions using halogen exchange leading to well-defined PIPOx were also developed and used for SI-ATRP. SI-ATRP was finally applied for synthesis of magnetic CI-PIPOx core–shell particles with two various molar masses of the grafted PIPOx. Finally, as a proof of applicability of such hybrid particles, the particles were dispersed in the phosphate buffer saline and glycerol to obtain the magnetorheological fluid with blood-like characteristics. Magnetorheological and cytotoxicity investigations proved that non-cytotoxic CI-PIPOx core–shell particles provided the system with sufficient yield stress values to act as an embolization agent.

Effect of interfacial shear strength between magnetic particles and carrier liquid on rheological properties of magnetorheological fluids

The interfacial mechanical strength between carbonyl iron particles (CIPs) and carrier liquid is one of the key factors for the rheological properties of magnetorheological (MR) fluids. Here, the microstructure and shear properties of the interface between CIPs and dimethyl silicone oil (DSO) are studied using molecular dynamics simulation. Results indicate that there is strong adhesive strength between Fe atoms on the surface of CIPs and DSO molecular chains during the shearing process. For the MR fluids with DSO viscosity of 50 and 200 mPa⋅s, the DSO molecular structure between CIPs is easy to break out under shear deformation owing to the short DSO chains. While as for the Fe/DSO/Fe model with DSO viscosity of 350 and 500 mPa⋅s, the interfacial shear strength is greatly higher than that with low viscosity DSO due to the entanglement between long chains of DSO. Finally, MR fluids with different viscosity DSO are prepared for rheological tests to verify our simulation results. By combining simulation and experiment, the high interfacial shear strength can improve the rheological properties of the MR fluids. These insights reveal the relationship between the interfacial shear properties of the CIPs/DSO and the rheological properties of MR fluids.

Effect of MXene nanosheets attached to carbonyl iron microspheres on the performance and stability of magnetorheological fluid

To improve the sedimentation stability of carbonyl iron (CI)-based magnetorheological fluid (MRF), a novel MRF with CI/MXene particles as dispersed phase was prepared. CI/MXene particles were prepared by attaching the lightweight MXene nanosheets onto the surface of CI particles (CIPs) as an additive. The micro-morphology, crystal structure and element composition of CI/MXene particles were analyzed by SEM, XRD and XPS characterization respectively, which confirmed the successful synthesis of CI/MXene particles. CI/MXene-based MRF possessed considerable high magnetorheological (MR) effect, and the magneto-induced shear stress was up to 49 kPa. More importantly, the sedimentation ratio of CI/MXene-based MRF was further characterized to evaluate its stability. Experimental results showed that the sedimentation ratio of MRF increased from 75.7% to 98.0% after mixing CIPs with 3 wt% MXene nanosheets. The sedimentation ratio of CI/MXene-based MRF increased by 29.5% compared to CI-based MRF. As a result, the addition of MXene nanosheets significantly improved the sedimentation stability of MRF while maintained high MR effect.

Silicone-encapsulated carbonyl iron filler for corrosion-resistant electromagnetic shielding

Carbonyl iron (CI) powder (CIP) is highly considered for use as a microwave absorber because of the high activity as well as the high magnetic permeability and saturation magnetization; yet, CIP is vulnerable to corrosion and aging in harsh conditions, such as salty and humid (e.g. ocean) or acidic environments, which limit the spectrum of its applications. The coatings can efficiently solve this problem. This study presents a novel simple approach for enhancing the electromagnetic wave absorption ability and the corrosion resistance of CI, which involves PDMS (polydimethylsiloxane) coating on the surface of CI particles using glycine (G) as a grafting agent. The properties of the resultant composite powder (G-CI/PDMS), such as thermal stability, corrosion resistance, hydrophobicity, and electromagnetic absorption, were determined. The thermal stability, hydrophobicity, and corrosion resistance of the G-CI/PDMS were enhanced, compared to CIP, ascribed to the barrier effect of PDMS. The electromagnetic parameters were reduced, but its electromagnetic wave absorption capacity was improved at specific frequencies and absorber thicknesses due to impedance matching. The polarization curves showed that the corrosion potential of the G-CI/PDMS was shifted to the positive direction and the corrosion current decreased by two orders of magnitude, compared to CIP.

The fabrication and properties of magnetorheological elastomers employing bio-inspired dopamine modified carbonyl iron particles

To obtain magnetorheological elastomers (MREs) with improved mechanical properties and exhibiting an enhanced magnetorheological (MR) effect, bio-inspired dopamine modification has been used to improve the functionality at the surface of carbonyl iron (CI) particles. Various techniques including x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to confirm that a polydopamine (PDA) layer of about 27.5 nm had been successfully deposited on the surface of the carbonyl iron particles prior to their inclusion in the MRE composites. The magnetic properties of PDA modified CI particles were shown to be almost the same as those for untreated CI particles. With the introduction of a PDA layer to the surfaces of the particles, both the tensile strength and the elongation at break of the MREs were improved. Furthermore, the MRE composites filled with PDA-coated CI particles exhibited lower zero-field storage moduli but higher magnetic field induced storage moduli when magnetization saturation was reached. The absolute and relative MR effect for the MREs reached 0.68 ± 0.002 MPa and 294% respectively, which were higher than those of MREs with pristine CI particles whose absolute and relative MR effect were 0.57 ± 0.02 MPa and 187% respectively. The findings of this work provide insights into enhanced fabrication of MREs with both improved mechanical properties and magneto-induced performance.

Enhanced electromagnetic interference shielding and antioxidation properties of silver/carbonyl iron particles by electroless plating

Silver (Ag)/carbonyl iron particles (CIPs) were prepared by electroless plating successfully to improve the electromagnetic interference (EMI) shielding and antioxidation properties of CIPs. The microstructure, phase composition, thermogravimetric (TG), electromagnetic and EMI shielding properties were analyzed respectively. Experimental results show that Ag particles were uniformly distributed on the surface of CIPs. TG results show the apparent weight gain temperature of Ag/CIPs was deferred compared with the weight gain temperature of CIPs. The total EMI SE value of Ag/CIPs/EP composite reaches about 36 dB with thickness 1.5 mm, which is far superior to the value of CIPs/EP composite. The EMI shielding result shows such Ag/CIPs composite material has an outstanding EMI shielding effect in the measured frequency band (8.2 GHz–12.4 GHz).

Role of calcium carbonate as an interfacial compatibilizer in the magneto-rheological elastomers based on ethylene/acrylic elastomer (AEM) and its magneto-induced properties

The interfacial interaction between carbonyl iron particles (CIPs) and elastomer matrix impacts the damping and mechanical properties of magneto-rheological elastomers (MREs). In this work, the calcium carbonate as a kind of compatibilizer was used to prepare high performances MREs based on ethylene/acrylic elastomer (AEM). The interfacial structure, mechanical properties and magneto-induced dynamic properties were characterized. The results showed that CaCO3 not only reinforced the AEM rubber, but also absorbed on the surface of CIPs. It acted as compatibilizer in the MREs based on AEM. The tensile strength of MREs increased with increasing the CaCO3 content. The magneto-induced properties had been enhanced due to the stress transfer among magnetic particles via additional of non-magnetic particles.

Modification of carbonyl iron particles by carboxyl-containing polydimethylsiloxanes

The possibility of preparing magnetic particles with the “core–shell” structure was demonstrated. The procedure is based on the treatment of carbonyl iron particles with polydimethylsiloxanes (PDMS) containing terminal or distributed over the chain carboxyl groups attached via the alkyl or aryl spacer. The presence of carboxyl-containing PDMS grafted to the surface of carbonyl iron particles was revealed by electron microscopy. Magnetorheological fluids and magnetic elastomers containing magnetic particles with the “core–shell” structure were obtained, and their rheological properties were studied.

Magnetorheological suspensions based on modified carbonyl iron particles with an extremely thin poly(n-butyl acrylate) layer and their enhanced stability properties

This study is focused on the modification of magnetic carbonyl iron (CI) particles with a thin polymer shell utilizing the atom-transfer radical polymerization (ATRP) technique, enabling control of the molecular weight and polydispersity of the final grafted polymer chains on the surface of CI particles and therefore also allowing tuning of the magnetorheological (MR) performance as well as stability properties (chemical, sedimentation). Hence, the bare CI particles were coated with a poly(butyl acrylate) (PBA) shell by the ATRP technique. The polymerization procedure of polymer grafting on the surface of the CI particles was characterized by gel permeation chromatography and nuclear magnetic resonance. The presence of the PBA chain on the CI particles was confirmed by Fourier infrared spectroscopy and energy dispersive spectroscopy. A saturation magnetization analysis using vibrating sample magnetometer proved that a thin polymer shell negligibly affects their magnetic properties, and data fit into the Jiles–Atherton model allowed the finite magnetization saturation for both bare CI and CI-PBA particles to be obtained. Furthermore, it was proved that a thin PBA coating provides sufficiently enhanced chemical and sedimentation stability properties for such a system, while the MR performance investigated using a rotational rheometer was affected negligibly. Finally it can be stated that a controllable coating performed via the ATRP technique is a useful tool to significantly improve stability properties, while the MR performance maintains values suitable for real-life applications.

Magnetorheology of core-shell carbonyl iron/ZnO rod-like particle silicone oil suspensions under oscillatory shear

The aim of this study is a preparation and application of inorganic coating on the surface of carbonyl iron particles. The two step solvothermal synthesis provides core-shell CI/ZnO rod-like morphology. Compact coating of particles has a slightly negative impact on their magnetic properties (measured for magnetic field strength in the range from 0 to 213 mT); however, there is a suitable magnetorheological performance investigated under oscillatory shear, suitable to be applied in real applications.

Graphene/graphene oxide: A new material for electrorheological and magnetorheological applications

The presence of functional groups provides graphene oxide sheets amphiphilic abilities with lower electrical conductivity and relatively high polarizability, which is appropriate for its electrorheological effect. In addition, because the graphene oxide sheets possess high surface area and relatively low particle density, graphene-/graphene oxide–supported materials have also attracted significant interest for fascinating magnetorheological applications. In this article, we briefly review the fabrication mechanisms and electrorheological characteristics of graphene-/graphene oxide–based electrorheological systems, such as pure graphene oxide sheets and various graphene-/graphene oxide–based polymer composites and nanocomposites of graphene/graphene oxide sheets with inorganic particles. As for the magnetorheological fluid application, the fabrication of graphene oxide sheets coated on the surface of carbonyl iron particles and graphene oxide/iron oxide composites are covered regarding improved dispersibility of the magnetorheological suspensions.

Magnetorheology of carbonyl iron particles coated with polypyrrole ribbons: The steady shear study

The aim of this study is a preparation and application of polymer coating on the surface of carbonyl iron particles. Oxidative polymerization of the pyrrole provides ribbon-like morphology. Compact coating of particles has a slightly negative impact on their magnetic properties (measured for magnetic field strength in the range from 0 to 300 mT); however, there is a significant increase in sedimentation stability. The effect of the particle concentration and temperature on the toughness of the internal structures was also investigated.

Surface modification of iron particles with a polyfluorinated disulfude: Effect of solvent and temperature

Adsorption of bis(2-chloro-3-oxaperfluorobutyl) disulfide from nonaqueous solutions onto the surface of carbonyl iron particles was studied with the aim of modification of these particles. The adsorption parameters were calculated using the Langmuir equation from the adsorption isotherms obtained in the interval 20-60°C. With an increase in temperature and in the solvent affinity for the modifying agent, the limiting amounts of the reagent that has interacted with the iron particle surface increase. This fact suggests the chemisorption nature of the process. The products of the reaction of iron with the disulfide can be desorbed from the particle surface.

Carbon nanotube coated magnetic carbonyl iron microspheres prepared by solvent casting method and their magneto-responsive characteristics

In order to improve not only the magnetorheological (MR) properties of soft magnetic carbonyl iron (CI) but also its dispersion stability, we fabricated a dense network of multi-walled carbon nanotubes (MWCNTs) on the surface of CI particles by using 4-aminobenzoic acid as a grafting agent through a two-step method: ultrasonication and solvent casting, based on the self-assembly of MWCNTs which have a similar density to the polymer but better magnetic properties due to the iron catalyst located in the MWCNT. The influence of coating layers on magnetic properties along with MR performance such as yield stress behavior and shear viscosity were investigated by a vibrating sample magnetometer and rotational rheometer. The suspension stability was found to be improved from a Turbiscan test.

Two-layer coating with polymer and carbon nanotube on magnetic carbonyl iron particle and its magnetorheology

Magnetic carbonyl iron (CI)-based magnetorheological (MR) fluids generally posses serious dispersion defects due to the large density mismatch between the CI particles and continuous oil medium, which restricts further MR applications. Polymer coating technology has been introduced in an attempt to reduce the density or prevent CI particle aggregation. In this study, a unique functional coating composed of a polyaniline layer and multiwalled carbon nanotube nest was fabricated on the surface of CI particles using a dispersion polymerization and solvent casting method to improve the sedimentation problem of CI-based MR fluids when dispersed in medium oil. The coating morphology was analyzed by scanning electron microscopy. The effect of the functional coating on the MR performance along with the sedimentation observations was investigated using a rotational rheometer. The results showed that the sedimentation of dispersed particles was improved considerably by the reduced density and rough morphology.

Fabrication of multiwalled carbon nanotube-wrapped magnetic carbonyl iron microspheres and their magnetorheology

Magnetorheological (MR) properties and dispersion stability of magnetic carbonyl iron (CI) microspheres were examined and found to be enhanced by fabricating a dense nest composed of multiwalled carbon nanotubes (MWCNTs) on the surface of CI particles in this study. The coating process is achieved by using 4-aminobenzoic acid as a grafting agent via self-assembly mechanism under sonication in which the MWCNTs were adopted as the coating material because MWCNTs possess similar density with polymer but better magnetic properties due to the iron catalyst originally included within the walls. The coating thickness and morphology of the MWCNTs nest were found to be related with the sonication duration. The influence of the coating layers on the magnetic properties and MR performance (yield stress behavior, shear viscosity) were examined using a vibrating sample magnetometer and rotational rheometer. Sedimentation rates of the fabricated MWCNT/CI suspension and pure CI suspension were also investigated.

Synthesis and corrosion study of zirconia-coated carbonyl iron particles

This paper describes the surface modification of micrometer-sized magnetic carbonyl iron particles (CI) with zirconia from zirconium(IV) butoxide using a sol-gel method. Zirconia shells with various thicknesses and different grain sizes and shapes are coated on the surface of CI particles by changing the reaction conditions, such as the amounts of zirconia sol, nitric acid, and CI particles. A silica adhesive layer made from 3-aminopropyl trimethoxysilane (APTMS) can be introduced first onto the surface of CI particles in order to adjust both the size and the shape of zirconia crystals, and thus the roughness of the coating. The microanalyses on these coated particles are studied by field-emission scanning electron microscopy (FE-SEM) and X-ray-diffraction (XRD). Accelerated acid corrosion and air oxidation tests indicate that the coating process dramatically improved oxidation and acid corrosion resistances, which are critical issues in various applications of CI magnetic particles.

Magnetorheological characteristics of carbon nanotube wrapped carbonyl iron particles

Carbonyl iron (CI) based magnetorheological (MR) fluid exhibits serious dispersion defect in general due to large density mismatch between CI particles and continuous medium, which restricts further MR application. Thus, various strategies were explored either to reduce the density or to prevent CI particle aggregation. Among them, polymer coating technology becomes more prevalent due to favorable morphology obtained and effective decrease in density by introducing polymeric shell; nevertheless, coating polymer on the surface of CI particles is always influenced by the selected grafting agent, mole ratio of reactant or the temperature of reaction. In this work, considering self-assembling trend of carbon nanotube (CNT) which exhibits similar density with polymer but better magnetic property due to the iron catalyst, we constructed a dense nest composed of CNT on the surface of CI particles by using 4-aminobenzoic acid (PABA) as a grafting agent under sonication. Thickness and morphology of the CNT nest were found to be related with sonication duration via SEM/TEM images. MR performances (yield stress behavior, shear viscosity) of the CI/CNT particles based MR fluid were investigated via controlled shear rate and controlled shear stress methods. Finally, sedimentation observation was checked to be improved.

Noncovalent self-assembly of carbon nanotube wrapped carbonyl iron particles and their magnetorheology

Carbonyl iron (CI) particles with their superior magnetic and physical properties, widely adopted as magnetorheological (MR) fluids, have been modified via diverse strategies to get well dispersed suspension in medium oil. Recently, coating technology has become prevalent due to improved favorable morphology and effective decrease in their particle density, resulting in an abated sedimentation problem. Therefore, considering self-assembling property of carbon nanotube (CNT), a dense nest of CNT onto the surface of CI particles was constructed in this study using 4-aminobenzoic acid as a grafting agent. MR characteristics of the CI/CNT particles which were examined via a rotational rheometer in a parallel plate geometry equipped with a magnetic field supplier were found to be similar with that of pristine CI suspension, while the sedimentation ratio is expected to be improved.