Advanced ODA-GO/CIP capsules with highly enhanced durability and dispersion for multi-purpose material delivery systems

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.

In principle, bare particles used in magnetorheological suspensions exhibit apparent corrosion instability. To suppress substantially this adverse phenomenon, the carbonyl iron particles modified with cholesteryl group (CI-chol) were suspended in silicone oil. There was found a deterioration of magnetorheological efficiency in comparison when only bare carbonyl iron (CI) particles are used; nevertheless, from the viewpoint of applicability, this change is fully acceptable. However, an anti-corrosion stability was significantly improved. Furthermore, dynamic oscillatory measurements and other characterizations were carried out and analyzed when both CI and CI-chol particles are applied.

Conventional polyurethane foam has non-tunable sound absorption properties. Here, a magneto-induced foam, called magnetorheological (MR) foam, was fabricated with the feature of being able to tune sound absorption properties, primarily from the middle- to higher-frequency ranges. Three different samples of MR foams were fabricated in situ by varying the concentration of Carbonyl Iron Particles (CIPs) (0, 35, and 75 wt.%). The magnetization properties and tunable sound absorption characteristics were evaluated. From the magnetic saturation properties, the results showed very narrow and small coercivity of hysteresis loops relative to the soft magnetic properties of the CIPs. MR foam with 75 wt.% CIPs showed a higher magnetic saturation at 91.350 emu/g compared to MR foam with 35 wt.% CIPs at 63.896 emu/g. For tunable sound absorption testing, the effect of ‘shifting’ to higher frequency was also observed when the magnetic field was applied, which was ~10 Hz for MR foam with 35 wt.% CIPs and ~130 Hz for MR foam with 75 wt.% CIPs. As the latest evolution of semi-active noise control materials, the results from this study are valuable guidance for the advancement of MR-based devices.

Corrosion and magnetic properties of encapsulated carbonyl iron particles in aqueous suspension by inorganic thin films for magnetorheological finishing application

Impact of corrosion process of carbonyl iron particles on magnetorheological behavior of their suspensions

Polymer composites embedded with ferromagnetic particles are widely applied in many engineering areas and have been extensively investigated for the past decade because of their outstanding magneto‐dependent properties. In this article, a series of addition cured polydimethylsiloxane (PDMS) composites with a mixture of carbonyl iron and cobalt particles at a given weight amount were prepared for the first time. Influences of the mass ratios of two additives on thermal stability, magnetic, mechanical properties, and magnetic actuating performance were studied experimentally. Experiment results demonstrated that the PDMS composite reinforced by carbonyl iron granule has a high thermal stability and saturation magnetization, and there is an optimal mixture ratio for the large and small particles. However, the loss factor is increased with an increase in Co contents for the binary blend system of RDE/Co and RXE/Co, respectively. For a comprehensive evaluation, the magnetoelastic ratios of all samples are obtained to demonstrate that the samples filled with carbonyl iron particles are easy to produce bending deflection in a uniform magnetic field. Under the influence of gradient magnetic field, the bending deflection of rectangular magnetized samples including Co particles show dependence on the direction of applied magnetic field, even, bidirectional and reversible responsive behavior are possible appearing for some special cases. These obtained results will provide some basic guidelines for selecting the proper materials to develop novel actuators. POLYM. COMPOS., 40:337–345, 2019. © 2017 Society of Plastics Engineers

Thermal characterization of magnetically aligned carbonyl iron/agar composites

Sound velocity of magnetic elastomers containing carbonyl iron and barium ferrite particles has been investigated by using an ultrasound pulse-echo method at 10 MHz. The sound velocity for magnetic elastomers containing barium ferrite was independent of the sample thickness, and the mean sound velocity was determined to be 1187 ± 5 m s−1. The sound velocity for magnetic elastomers containing carbonyl iron linearly decreased with the sample thickness, and the values (954–1031 m s−1) were lower than those of barium ferrite. Microphotographs revealed that carbonyl iron particles were randomly dispersed and barium ferrite particles were heterogeneously dispersed in the polyurethane matrix. The relationship between the sound velocity and the particle dispersibility is discussed. Barium ferrite particles showing heterogeneous dispersion showed low values of sound velocity of ca. 1200 m s−1, carbonyl iron particles showing random dispersion exhibited much lower values of sound velocity of ca. 1000 m s−1.

Magneto-rheological elastomer (MRE) is a new kind of smart material. Its rheological properties can be altered and controlled in a real time manner when it is applied an external magnetic field. For calculating magnetic properties of MRE material, usually Maxwell-Garnet equation is used to acquire an approximately effective permeability. This equation treats the magnetic property of particles as linear. However, when the applied magnetic field is alternating or rotating, the nonlinearity of magnetic property and magnetic hysteresis cannot be neglected. Hence, the measurement and modelling of the magnetic properties under alternating and rotating magnetic fields are essential to explore new applications of the material. This paper presents the investigation on the magnetic hysteresis properties of MRE material under one-dimensional (1-D) alternating and two-dimensional (2-D) rotating magnetic field excitations. A kind of MRE material, consisting of 70% carbonyl iron particles, 10% silicone oil, and 20% silicone rubber, was used to investigate the magnetic properties. The diameter of carbonyl iron particles is 3–5 μm. The measurement results, such as the relations between magnetic field intensity (H) and magnetic flux density (B) under different magnetic field excitations on the MRE sample, have been obtained and analyzed. These data would be useful for design and analysis of MRE smart structures like MR dampers.

The relation between the number of magnetic particles and the change in storage modulus induced by a magnetic field was investigated for weak hydrogels containing carbonyl iron, iron oxide, and barium ferrite particles with different diameters in primary particles while maintaining the magnetization of magnetic particles. The change in storage modulus exhibited a power dependency against the number of magnetic particles, which was nearly independent of the magnetic particles. The change in storage modulus was successfully scaled by the reduced number of magnetic particles using the diameter of secondary particles. Microphotographs revealed that iron oxide and barium ferrite particles form aggregations while carbonyl iron particles are well dispersed in carrageenan gels. The diameter of secondary particles determined by a relation between the change in storage modulus and the reduced number of magnetic particles showed similar values with those observed in microphotographs.

High microwave attenuation performance of planar carbonyl iron particles with orientation of shape anisotropy field

Understanding the reinforcing behaviors of polyaniline-modified carbonyl iron particles in magnetorheological elastomer based on polyurethane/epoxy resin IPNs matrix

Five types of magneto‐rheological elastomers (MREs) based on natural rubber were synthesized by incorporating carbonyl iron particles (CIP) as the primary filler. The objective was to investigate the influence of carbon fiber and magnetic particle content on the mechanical and magneto‐rheological properties of the MREs. Carbon fibers (CF) were further added as secondary reinforcement pre‐modified with polydopamine. The composite's microstructure was examined through scanning electron microscopy (SEM), while the mechanical and magnetodynamic properties were assessed using an electronic universal testing machine and an advanced rotational rheometer. The addition of appropriate amounts of CIP and CF resulted in increased rubber modulus, indicating the formation of a filler‐rubber network and the synergistic effect between carbon fibers as a supporting structure and CIP. Compared to the unfilled MREs, the mechanical and magnetodynamic properties were further improved by adding 2 and 4 wt% CF. These findings demonstrate that employing carbon fibers as reinforcing fillers and incorporating suitable magnetic fillers can enhance the magnetic and mechanical properties of the materials, providing a theoretical basis for the study of MREs' performance. Highlights CF and CIP synergistically enhance the strength of the rubber matrix. The MR effect is gradually enhanced with the increase of CIP content. Modified CF has a promoting effect on the magnetic responsivity. Magnetic responsivity increases with increasing modified CF content. Improved mechanical and magnetodynamic properties of composites.

The effect of different types of multiwall carbon nanotubes (MWCNTs) on the morphological, magnetic and viscoelastic properties of magnetorheological elastomers (MREs) are studied in this work. A series of natural rubber MRE are prepared by adding MWCNTs as a new additive in MRE. Effects of functionalized MWCNT namely carboxylated MWCNT (COOH-MWCNT) and hydroxylated MWCNT (OH-MWCNT) on the rheological properties of MREs are investigated and the pristine MWCNTs is referred as a control. Epoxidised palm oil (EPO) is used as a medium to disperse carbonyl iron particle (CIP) and sonicate the MWCNTs. Morphological and magnetic properties of MREs are characterized by field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM), respectively. Rheological properties under different magnetic field are evaluated by using parallel plate rheometer. From the results obtained, FESEM images indicate that COOH-MWCNT and CIP have better compatibility which leads to the formation of interconnected network in the matrix. In addition, by adding functionalized COOH-MWCNT, it is shown that the saturation magnetization is 5% higher than the pristine MWCNTs. It is also found that with the addition of COOH-MWCNT, the magnetic properties are improved parallel with enhancement of MR effect particularly at low strain amplitude. It is finally shown that the use of EPO also can contribute to the enhancement of MR performance.

The finishing efficiency in magnetic field assisted finishing (MFAF) process mainly depends on the rheological properties of magnetorheological (MR) polishing medium. A detailed rheological study of MR polishing fluid at different volume concentration of fluid constituents and magnetic field is conducted to predict their contribution on yield stress and viscosity. Magnetic field has the highest contribution followed by carbonyl iron particles (CIPs) concentration to the yield stress and viscosity. It is observed that Herschel–Bulkley model better fits the rheological data than other two models. Also, it has been found that when total solid contents of MR polishing fluid exceeds more than 35%, there is a decrease in the yield stress. From magnetic characterisation, it is observed that saturation magnetisation increases with CIP concentration and decreases with abrasive concentration. The surface finish of stainless steel workpiece improves with an increase in the yield stress and viscosity at higher magnetic field and CIP concentration.