Carbonyl Iron Microspheres Research Articles

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.

Fabrication and Magnetorheological Characteristics of Core–Shell-Typed Poly(2-Methylaniline)/Carbonyl Iron Microspheres

Core–shell particles of the poly-2-methylaniline (PMAN)/carbonyl iron (CI) composite material were prepared by dispersion polymerization. Dopamine was used as a chemical grafting agent to modify the surface of CI particles to enhance the affinity between PMAN particles and pure CI particles. The morphology and crystalline structure of the prepared core–shell PMAN/CI microspheres were tested by TEM and X-ray diffraction, respectively. Their magnetic behaviors were analyzed using a vibrating-sample magnetometer. The sedimentation stability of the particles was further analyzed using a Turbiscan analyzer. The analysis results revealed that the dispersion stability of the particles was better than that of the pure CI particles. The characteristics of the PMAN/CI particle-based magnetorheological fluid with a yield stress of 4800 Pa at 342 kA/m were measured using a rheometer.

Facile Synthesis of Solvent Cast Arabic Gum Coated Carbonyl Iron Microspheres and Their Magnetorheological Characteristics.

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.

Synthesis of core-shell formed carbonyl iron/polydiphenylamine particles and their rheological response under applied magnetic fields

Soft-magnetic carbonyl iron (CI) microspheres were coated with conducting polydiphenylamine (PDPA) using an oxidative dispersion polymerization process to produce core-shell-structured CI/PDPA particles for magnetorheological (MR) applications. The CI particles were initially modified with a p-amino benzoic acid to enhance their affinity to PDPA. The surface morphology of the CI/PDPA core-shell particles was characterized by scanning electron microscopy. The chemical composition, weight and atom percentage, thermal properties, and magnetism of the composites were investigated by X-ray energy dispersive spectroscopy, Fourier-transformed infrared spectroscopy, thermogravimetric analysis, and vibrating-sample magnetometry, respectively. The rheological behavior of the MR fluids for both pristine CI and CI-PDPA particles dispersed in silicone oil was measured using a rotating rheometer. The sedimentation characteristics of the CI/PDPA-based MR fluid with improved dispersion stability due to the reduced density mismatch was analyzed further using a Turbiscan.

Graphene-oxide coating for corrosion protection of iron particles in saline water

The corrosion resistance behavior of graphene oxide (GO) sheets-coated carbonyl iron (CI) microspheres (GO/p-CI sample) was investigated and compared with that of bare CI particles. The GO coating on the CI particles was achieved by utilizing 4-aminobenzoic acid as grafting agent. The cyclic voltammetry of the electrode containing this GO/p-CI sample in 1 mol/L KCl solution does not show any oxidation-peak in contrast to that of the bare carbonyl iron (CI) containing electrode. The charge transfer resistance of GO/p-CI sample was measured to be higher than that of bare CI. The corrosion-potential shifts towards the positive potential direction confirming higher passivity/less corrosive nature of the GO/p-CI sample. Furthermore, the corrosion-current of GO/p-CI sample was lower than that of the bare CI particles. Our results confirm the passivity and excellent corrosion protection behavior of the GO coating on iron structures.

Enhanced microwave absorption characteristics of nanocomposite based on hollow carbonyl iron microspheres and polyaniline decorated with MWCNTs

This work presents the preparation of a novel lightweight microwave absorber nanocomposite based on a combination of hollow microspheres of iron carbonyl (CI) and polyaniline (PANI) decorated with MWCNTs by a simple blending technique. The weight ratio of hollow CI to PANI decorated with MWCNTs is 2:1. The morphology of the hollow CI microspheres-prepared by Pitting corrosion of CI powder immersed into corrosive solution at different concentrations and for different periods of time-was investigated by scanning electron microscope (SEM). The complex permittivity, permeability and microwave absorption properties of the composite are studied in the frequency range of 8.5–12.5 GHz with 30 wt% of composite in paraffin. The optimal reflection loss (RL) of −25.5 dB is observed at 11 GHz with a matching thickness of 2.0 mm and a bandwidth of 3.6 GHz.

Magnetorheological properties and polishing characteristics of silica-coated carbonyl iron magnetorheological fluid

While magnetorheological fluids can be used for ultra-precise polishing, for example, of advanced optical components, oxidation of metallic particles in water-based magnetorheological fluids causes irregular polishing behavior. In this study, carbonyl iron microspheres were initially coated with silica to prevent oxidation and were used to polish BK7 glass. In addition, their rheological and sedimentation characterizations were investigated. Material removal and surface roughness were analyzed to investigate the surface quality and optimal experimental conditions of polishing wheel speed and magnetic field intensity. The maximum material removal was 0.95 µm at 95.52 kA/m magnetic field intensity and 1854 mm/s wheel speed. A very fine surface roughness of 0.87 nm was achieved using the silica-coated magnetorheological fluid at 47.76 kA/m magnetic field intensity and 1854 mm/s wheel speed.

Effects of surface treatment on magnetic carbonyl iron/polyaniline microspheres and their magnetorheological study

To achieve better chemical affinity between conducting polyaniline (PANI) and soft magnetic carbonyl iron (CI) microspheres, we initially attached hydroxyl groups to the surface of CI using p-toluenesulfonic acid monohydrate. The PANI-coated CI composite particles were then fabricated via a chemical oxidation polymerization method. Both the aniline monomer and anilinium cation tended to surround the activated surface of the CI microspheres due to hydrogen bonding and electrostatic interactions, providing a better core-shell shape of the CI/PANI particles. Crystallinity of the product particles and bonding between CI and PANI were measured by X-ray diffraction and FT-IR spectroscopy, respectively, while the shell morphology and thermal stability were measured by scanning electron microscope and thermogravimetric analysis, respectively, confirming the successful coating performance. Viscoelastic behaviors of the MR fluid prepared by suspending the magnetic particles in medium oil were measured via a rotation rheometer under an induced magnetic field. It also exhibited a typical MR flow behavior, which was analyzed using various rheological models. Its sedimentation was detected using a Turbiscan, showing a 60% and 11% improved dispersion stability at 200min and 900min, respectively, compared to the pure CI particles by decreasing the density mismatch between composite particle and silicone oil.

The magnetorheological fluid of carbonyl iron suspension blended with grafted MWCNT or graphene

In this work, the magnetorheological (MR) fluids containing MWCNT/CI (carbonyl iron) complex and graphene/CI complex were prepared and have the better dispersity in silicone oil than CI powders alone. 1, 4-Aminobenzoic acid (PABA) was used as a grafting agent to modify CI powders to have NH2-end-group so that such nanoparticles can adsorb to acid-treated MWCNT or graphene via attraction of NH2 and COOH groups. The MWCNT/CI complex and graphene/CI complex have a structure of carbonyl iron nanoparticles adsorbed to MWCNT and graphene by self assembly, respectively. Because the carbonyl iron particles possessing magnetic permeability in nanometer scale adsorb to MWCNT or graphene which usually has a nanometer-scaled diameter and a micrometer-scaled length in this work, the dispersity of MWCNT/CI or graphene/CI complex in silicone oil is superior than the previous report [15] that the micrometer-scaled carbonyl iron microspheres were coated with multiwalled carbon nanotubes. Among CI (unmodified), MWCNT/CI and graphene/CI, graphene/CI has the best dispersity while MWCNT/CI still has the better dispersity than unmodified CI. At the temperature T=300K, the saturation magnetizations of CI, MWCNT/CI, graphene/CI are 208, 211emu/g, and 204emu/g, respectively, indicating that MWCNT/CI complex and graphene/CI complex still maintain the saturation magnetization as high as CI without being interfered by the blended MWCNT or graphene. A wide dynamic range of the yield stress adjusted through varying the electric current can be achieved by the MR fluids containing 69wt% MWCNT/CI and graphene/CI which is useful in a shock absorber or damper. The result of the yield stress indicates the suspended MWCNT/CI particles are oriented more easily toward the direction perpendicular to the flow direction to block the flow stream lines.

Magnetorheology of dimorphic magnetorheological fluids based on iron nanorods

The aim of this paper is to document suitability of partial substitution of magnetic carbonyl iron (CI) microspheres with iron nanorods to obtain dimorphic magnetorheological (MR) suspensions with comparable MR performance to conventional MR suspensions exclusively based on (CI) microspheres while the sedimentation stability is considerably improved. The morphology of CI and iron nanorods was analyzed via scanning electron microscopy and transmission electron microscopy, respectively, and magnetic properties via vibrating sample magnetometry. The steady shear flow and small-amplitude dynamic oscillatory shear measurements were carried out to confirm effective MR performance. The sedimentation test showed positive role of dimorphic composition of dispersed phase on the sedimentation stability.

Fabrication of dopamine grafted polyaniline/carbonyl iron core-shell typed microspheres and their magnetorheology

Abstract Magneto-responsive polyaniline (PANI)-coated magnetic carbonyl iron (CI) microspheres were synthesised using a dispersion polymerisation process. The CI particles were initially modified using dopamine as a chemical grafting agent to strengthen the affinity between PANI and the CI particles. The surface morphology of the fabricated core-shell structured particles was confirmed by scanning electron microscopy. The chemical composition of the dopamine-modified CI particles was examined by X-ray energy dispersive spectroscopy, and the magnetic properties of the particles were analysed using a vibrating sample magnetometer. The magnetorheological (MR) characteristics of the CI-PANI particle-based MR fluid dispersed in silicone oil were measured using a rotational rheometer, which exhibited a typical liquid-like to solid-like phase transition. The sedimentation stability of the microspheres was analysed further using a Turbiscan apparatus with better dispersion stability than pure CI particles.

Fabrication and magnetic stimuli-response of polydopamine-coated core–shell structured carbonyl iron microspheres

Soft magnetic carbonyl iron (CI) for application to magnetic stimuli-responsive smart materials in an external magnetic field normally implies severe sedimentation problems because of the density imbalance between the CI particles and the dispersed medium. As a new method of ameliorating this problem, CI/polydopamine (PDA) composite particles with core–shell structure were synthesized via an oxidative self-polymerization process, bringing into an account of the coating efficiency of the PDA. Surface morphology of the CI/PDA composite particles was characterized by scanning electron microscopy, while Fourier transform infrared spectroscopy, X-ray energy-dispersive spectroscopy, and vibrating sample magnetometry were adopted to measure the chemical composition, weight and atomic percentages, and magnetic properties of the fabricated composites. The magnetic stimuli-response of their magnetorheological (MR) properties was examined by using a rotational rheometer at various magnetic field strengths and compared with pristine CI-particle-based MR fluid. The measured dynamic yield stress was fitted to a universal yield stress equation well. The sedimentation properties of the CI/PDA-composite-based MR fluid were further examined by a Turbiscan™. In addition, the anti-corrosion characteristic of these particles was also investigated.

Magnetorheology of a Carbonyliron Microsphere Suspension with a Halloysite Additive and Its Damping Force Characteristics

A carbonyliron (CI)-based magnetorheological (MR) suspension was prepared with halloysite nanoclay particles as an additive. The MR properties of the suspension were investigated using a rotational rheometer with a parallel-plate geometry equipped with a magnetic field supply under a range of external magnetic field strengths. From the sedimentation ratio test to assess the dispersion stability, the addition of halloysite particles to the CI suspension was found to improve the sedimentation problem. MR fluids containing both pure CI and CI/halloysite were employed in a custom-designed MR damper, and their damping characteristics, such as the damping force as a function of time, displacement, and velocity, were examined experimentally because the vibration attenuation using mechanical damper systems is one of the main applications of MR fluids. Under the same magnetic field strength, the damping characteristics of the two MR fluids were found to be related directly to their yield stresses.

Polyaniline/Fe composite nanofiber added softmagnetic carbonyl iron microsphere suspension and its magnetorheology

We synthesized PANI/Fe0nanofibers and added them to a carbonyl iron based magnetorheological fluid to study its enhanced magnetorheological behavior and sedimentation stability.

Magnetorheology of suspensions based on graphene oxide coated or added carbonyl iron microspheres and sunflower oil

Magnetorheological (MR) fluids based on carbonyl iron (CI) particles coated with graphene oxide (GO) and sunflower oils were studied and compared with MR fluids (MRFs) prepared with CI particles added with GO sheets. Adding GO sheets into CI had a negligible effect on the rheological properties of the MRF. Coating the spheres with GO markedly decreased the shear strength at high shear rates due to the remarkable lubricating function of the GO surface. Different behaviors were observed in the shear thickening phenomenon when the GO surface changed the mechanical interaction between particles. The results demonstrated the importance of the role of interparticle friction for MRF in shear mode and discussed the weak shear thickening phenomenon with fine lubricating coating layers and oils.

Brake performance of core–shell structured carbonyl iron/silica based magnetorheological suspension

Chemically stable core–shell structured magnetic particles were synthesized by coating soft-magnetic carbonyl iron (CI) microspheres with silica through a sol–gel reaction, and applied as magnetorheological (MR) materials for a specially designed small-sized MR brake. The dynamic yield stress of the MR suspension containing the synthesized particles was also measured using a rotational rheometer under an applied magnetic field. The performance characteristics of the MR brake, including field dependent torque, hysteresis, time and torque tracking control responses were examined. The results showed that with the exception of the settling time, the other response times were faster than those of the pristine CI based MR fluid.

Self-assembly of graphene oxide coated soft magnetic carbonyl iron particles and their magnetorheology

The surface of carbonyl iron (CI) microspheres was modified with graphene oxide (GO) as a coating material using 4-aminobenzoic acid as the grafting agent. The morphology, elemental composition, and magnetic properties of the GO-coated CI (GO/CI) particles were examined by scanning electron microscopy, energy dispersive X-ray spectroscopy and vibrating sample magnetometry, respectively, confirming their composite formation. The magnetorheological (MR) performance of the GO/CI particle-based suspension was examined using a rotational rheometer connected to a magnetic field supply. The GO/CI particles suspension exhibited typical MR properties with increasing shear stress and viscosity depending on the applied magnetic field strength.

Core-Shell Structured Polystyrene Coated Carbonyl Iron Microspheres and their Magnetorheology

Soft magnetic carbonyl iron (CI) microparticle, possessing high magnetic saturation with less magnetic hysteresis, was mostly applied as an active material in magnetorheological (MR) fluids. However, pure CI suspension is known to have poor dispersion stability in the MR fluid system. To overcome this problem, we fabricated polystyrene (PS)-coated CI particles through a simple coating method of dispersion polymerization. Surface morphology of synthesized PS coated CI was observed using scanning electron microscopy. Performance of this MR fluid dispersed in silicone oil, including shear stress and shear viscosity, was measured using a rotational parallel disk rheometer in a steady shear flow and suspension stability was examined by a Turbiscan apparatus. The PS-coated CI suspension was found to improve settling of the CI particles without much deterioration of MR performance.

Core–shell-structured cross-linked poly(glycidyl methacrylate)-coated carbonyl iron microspheres and their magnetorheology

Poly(glycidyl methacrylate) (PGMA)-coated soft magnetic carbonyl iron (CI) particles were fabricated by cross-linking PGMA with ethylene glycol dimethacrylate. The synthesized core–shell structured CI/PGMA microspheres were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and thermal gravimetric analysis. The CI particles were confirmed to be coated well with PGMA. A magnetorheological (MR) suspension was prepared based on the synthesized CI/PGMA particles dispersed in silicone oil and measured using a rotational rheometer at various magnetic field strengths. The sedimentation property, which was observed using a Turbiscan, indicated better settling stability than the pure CI particle-based MR suspension.

Magnetorheology of xanthan-gum-coated soft magnetic carbonyl iron microspheres and their polishing characteristics

Magnetorheological (MR) fluids are colloidal suspensions of soft magnetic particles dispersed in a non-magnetic liquid. Among their applications, MR polishing has attracted considerable attention owing to its smart control of the polishing characteristics for dedicated microelectromechanical system applications. To improve the polishing characteristics of MR fluids, we fabricated carbonyl iron (CI) microspheres coated with xanthan gum (XG) by using a solvent casting method. The morphologies and densities of both pure CI and CI/XG particles were characterized using a scanning electron microscope and a pycnometer, respectively. In addition, the rheological characteristics of the MR fluids under various applied magnetic field strengths were examined using a rotational rheometer. The MR polishing characteristics were conducted using an MR polishing machine to examine the surface roughness and the material removal by MR polishing with added nano-ceria slurry abrasives.