Electrorheological Behavior Research Articles

Smart electrorheological behavior of Cr-doped multiferroelectric FeBiO3 nanoparticles

A series of Cr-doped multiferroelectric FeBiO3 nanoparticles were synthesized via a facile sol gel method. The resultant Cr-doped FeBiO3 was characterized by means of different techniques, such as scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and electrorheological (ER) tests. Under an external electric field, electrorheological properties of the suspension containing such Cr-doped and undoped FeBiO3 particles were investigated by steady shear experiments. It was found that the suspension of Cr-doped FeBiO3 particles possesses a better ER effect than that of pure FeBiO3 particles. Furthermore, different Cr-doped concentration plays an important role on the ER behavior. Combining the dielectric analysis, the enhanced ER effect of Cr-doped FeBiO3 suspension can be attributed to the improved interfacial polarization.

Electrorheological behaviour of a starch-oil system

A simple system consisting of a suspension of 10 wt % of starch in silicone oil was subjected to electrorheological testing. The system exhibits a complex behaviour depending on the electrical field. On one hand, the application of an external electric field induced the formation of a linear structure, aligned with the electric field. The formation of that structure was studied by several rheological methods. The rate of modifying the electric field intensity resulted to be related to the electric field value at which percolation is observed. On the other hand, master curves for the structure formation and breakdown in squeeze experiments were obtained.

Polypyrrole-wrapped halloysite nanocomposite and its rheological response under electric fields

Conducting polypyrrole (PPy)-wrapped halloysite nanotube (HNT) nanocomposites (PPy/HNT) were prepared using an in situ polymerization process of pyrrole monomer in the presence of a HNT dispersion, and its electrorheological (ER) properties were investigated under applied electric fields. The morphology of both HNT and PPy/HNT nanocomposite was examined by scanning electron microscopy and transmission electron microscopy. The synthesized PPy/HNT nanocomposites were also analyzed using a physisorption analyzer, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The ER properties of the PPy/HNT nanocomposite dispersed in silicone oil measured using a rotational rheometer under different electric field strengths exhibited ER behaviors of shear stress, dynamic moduli, and relaxation modulus with a change in slope from 1.5 to 1.0.

Bionic cactus-like titanium oxide microspheres and its smart electrorheological activity

Abstract Bionic cactus-like titanium oxide microspheres were synthesized, and their electrorheological (ER) activities under an applied electric field were investigated. Firstly, monodispersed amorphous titanium oxide submicrospheres were fabricated previously using a controlled hydrolysis procedure, and then 3D cactus-like hierarchical titanium oxide microspheres was obtained via a hydrothermal treatment of monodispersed titanium oxide submicrospheres. The morphology and structure of the bionic cactus-like titanium oxide microspheres were characterized by scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, Energy-dispersive spectroscopy and nitrogen adsorption, respectively. The nanostructure of hierarchical microspheres evaluated with increasing hydrothermal time was studied and complex 3D hierarchical morphological microspheres can be obtained. The ER behaviors of the cactus-like titanium oxide microspheres are characterized using a rotational rheometer.

Enhanced effect of dopant on polyaniline nanofiber based electrorheological response

As a potential candidate for electrorheological (ER) materials, polyaniline (PANI) nanofibers were synthesized via an interfacial polymerization route, because of their easy synthesis, high stability, controllable conductivity and good ER response. In this study, a new dopant, indole-2-carboxylic acid, was used to improve the ER performance. The synthesized PANI nanofibers were dispersed in silicone oil at 10 vol% and their rheological properties as an ER fluid were examined using a rotational rheometer under a variety of electric field strengths. In addition, their dielectric properties were studied using a LCR meter. The results showed that indole-2-carboxylic acid, which has high polarizability, enhanced the ER effect of PANI nanofibers, showing that polarizability is an important parameter affecting the ER behavior.

Modeling and analysis of an electrorheological flow behavior containing semiconducting graphene oxide/polyaniline composite particles

The flow behavior of electrorheological suspensions containing graphene oxide/polyaniline composite particles was reanalyzed using a model we proposed recently. The shear stress data obtained experimentally from an electrorheological fluid revealed that the structural reformation of the aligned fibers depended on the shear rate, in good agreement with the model. The static yield stress was depended quadratically on the field strength, in agreement with the predictions of the polarization model. A scaling function was used to model the yield stress behavior of the fluid over a range of electric fields, and it correctly predicted the static yield stress behavior.

Properties of aniline-modified strontium titanyl oxalate-based electrorheological suspension

Aniline-modified strontium titanyl oxalate (STO) particles were fabricated with a precipitation method. The structures of the particles were analyzed by x-ray diffraction analyses, Fourier transform infrared spectrometry and thermogravimetric analysis. Scanning electron microscopy was used to analyze the morphology of the particles. The results indicate chemical bonds are formed between STO and aniline. By tuning the molar ratio of aniline to Ti, the morphology of the aniline-modified STO particles can be sphere, polyhedron and a mixture composed of clusters of nano particles and micro rod-like particles. Electrorheological (ER) properties, temperature effect, thixotropy and sedimentation stability of the ER fluids based on the pure STO and the aniline-modified STO were tested. The results indicate all the properties strongly depend on the content of the aniline during the fabrication process of the particles. The ER fluid with a molar ratio of aniline/Ti of 2 presents the highest shear stress, yield stress, leak current density and the most stable ER behavior at changing temperatures. The reason is the particles have polyhedron morphology and absorbed polar aniline molecules. Because of the stable space grid structure formed by the particles with a molar ratio of aniline/Ti of 3, the ER fluid exhibits better thixotropy and sedimentation stability than the others.

Nano titanium dioxide particles modified with poly(lauryl methacrylate) and its electrorheological and electrophoretic behavior

In this paper, we reported a new non-aqueous electrorheological (ER) fluid structured by TiO2 nano-particle modified poly(lauryl methacrylate) (PLMA/TiO2) dispersed in low viscosity isoparaffin and studied its electrorheological behaviors. Moreover, the ER fluid was applied to electrophoretic display at the first time. PLMA/TiO2 particles were prepared via graft copolymerization using γ-methacryloxypropyltrimethoxysilane and lauryl methacrylate, successively. The thickness of the cladding layer of nano titanium dioxide surface was about 2.9nm. When an external electric field was applied to this dispersed system, from 0 to 4.5kV/mm, the ER fluid showed a good rheological property and the viscosity of ER fluid was increased from 20 to 160mPas. The shear stress strengthened with PLMA/TiO2 particles weight fraction increase in dispersed system. As a white medium, the ER fluid was mixed with carbon black to prepare a micro-cup electrophoretic display device, which could successfully realize electrophoretic display for white and black state under an electric field. The maximum contrast ratio of the micro-cup device was 6.2, and response time was 288ms, and the clock micro-cup device could maintain display state than 24h in the absence of electric fields.

Acetylacetone stimulus effect on electrorheological properties of TiO2 aggregated nanoparticles

We present experimental results on electrorheological behavior under an ac electric field, and dielectric properties of colloidal suspensions composed of aggregated titanium dioxide nanoparticles dispersed in insulating PDMS silicon oil, as a function of adsorbed acetylacetone (Acac) dipolar molecules on TiO2 surface. The results show that the elastic modulus G′ of TiO2–Acac/PDMS ER fluid decreases when the electric field frequency is increased gradually from 10 to 104 Hz. In the range of tested electric field frequencies, we observe that the dielectric properties are given essentially by an interfacial polarization which is maximal at low frequency. At low frequency (υ = 10 Hz), G′ increases with the increasing Acac/TiO2 surface coverage θ from 0 to 0.45, due to the high polarization of the particles caused by the increase of the charge carriers that move to the interface between TiO2 particles and the insulating medium. For θ = 0.35, G′ reaches 1.80 MPa which is 3.6 times greater than that of pure TiO2/PDMS ER fluid. However, G′ decreases by increasing θ beyond 0.45; in such cases, the mismatch on dielectric constant and conductivity between dispersed phase (TiO2) and insulating medium (PDMS) begins to fall as θ increases because of the increase of Acac dipoles remaining free in PDMS. The performance of TiO2–Acac/PDMS ER fluid at low frequency was validated by a reversibility test where elastic modulus G′ increases dramatically and returns to its initial state as soon as several cycles of a switching electric field were applied between 0 and 1 kV/mm successively.

Synthesis of polyacene quinone radical polymers with controllable conductivity and their smart electrorheological behavior

Polyacene quinone radical (PAQR) polymers were synthesized by the step-growth condensation of aromatic hydrocarbon derivatives reacting with pyromellitic anhydride via a solvothermal method. The morphology and structures of PAQRs with varied polymerization processes were confirmed by the analysis of X-ray, IR, SEM and TG measurement. The effects of different aromatic hydrocarbons on the synthesis and morphology of PAQR polymers were investigated and then utilized as an electrorheological (ER) material by dispersion in silicone oil. The ER performances are investigated as a function of electric field strength by using a rheometer and the relationship between the conductivity and electrorheological (ER) properties of different polyacene quinone radical (PAQR) polymers were discussed.

Electrorheology of Suspensions Containing Interfacially Active Constituents

We recently showed that a suspension of micrometer-sized polystyrene (PS) particles in a PDMS liquid, mixed with small (1 wt %) amounts of a nanocage, sulfonated polyhedral oligomeric silsesquioxane (s-POSS), exhibited significant electrorheological (ER) behavior. This behavior was associated with the formation of a thin adsorbed layer of s-POSS onto the surfaces of PS and the subsequent formation of polarization-induced aggregates, or structures, responsible for the ER effect in an applied electric, E, field. Current theory suggests that the ER effect would largely be determined by the dielectric and conductive properties of the conductive layer of core/shell particles in ER suspensions. We show here that sulfonated-PS (s-PS)/PDMS suspensions exhibit further increases in the yield stress of over 200%, with the addition of s-POSS. The yield stress of this system, moreover, scales as τy [proportionality] E(2). The dielectric relaxation studies reveal the existence of a new relaxation peak in the s-POSS/s-PS/PDMS system that is absent in the s-POSS/PS/PDMS suspension. The relative sizes of these peaks are sensitive to the concentration of s-POSS and are associated with changes in the ER behavior. The properties of this class of ER fluids are not appropriately rationalized in terms of current theories.

Double template assisting synthesized core–shell structured titania/polyaniline nanocomposite and its smart electrorheological response

Abstract Monodispersed titanium oxide nanospheres were synthesized via the controlled hydrolysis method in this study firstly. Then the rapid mixing method was used to in situ oxidation polymerize aniline, which can modify the surface of titanium oxide nanospheres to form a core/shell nanostructure. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and rotational viscometer were used to investigate its structure, morphology and properties. The different type and dosage of surfactants, different acids, crystal forms of titanium oxide and different dosages of aniline were studied to analysis the impact on the TiO2/PANI nanocomposites. The suitable type and dosage of surfactants, the ratio of aniline to titania were the key to synthesize the nanocomposite, which can include nanoring, nanofiber or nanoparticles core/shell composite depending the synthesis condition. The titania/polyaniline composite showed typical electrorheological (ER) behavior, which demonstrated its potential applications as an ER smart material.

An effect of carbonization on the electrorheology of poly(p-phenylenediamine)

Particles of poly(p-phenylenediamine) were synthesized by the oxidation of p-phenylenediamine with ammonium peroxydisulfate at two oxidation levels. They were carbonized at 200–800°C in inert atmosphere and subsequently tested in electrorheological (ER) suspensions. Scanning electron microscopy, Raman spectroscopy and thermogravimetric analysis were used to characterize an influence of the carbonization on the molecular structure and particles size and shape. Subsequently, ER suspensions were prepared by mixing polymer particles and silicone oil. In order to determine an effect of carbonization on the ER behaviour, a number of rheological measurements under various external electric fields were carried out. Dielectric spectroscopy was used for the evaluation of the influence of particles carbonization on the ER performance of suspensions as well. Although the particles carbonized at 600°C exhibited nearly the same ER effect as the original particles due to significantly higher specific surface area, the efficiency of ER performance was the highest for original, i.e. non-carbonized particles. This is due to lower field-off viscosity in comparison to ER fluids based on carbonized particles.

Electrorheological and dielectric behavior of new ionic liquid/silica systems

New phosphonium-based ionic liquids, denoted, 11-carboxyundecyltriphenylphosphonium bromide (IL1) and octadecyltriphenylphosphonium iodide (IL2), were employed on the sol–gel synthesis to prepare new silica-based matrices. The fastest gelation during the sol–gel process was observed in hydrolysis/condensation of tetraethoxysilane in the presence of IL1. The confinement of ionic liquids (especially IL1) inside the silica networks was suggested by thermogravimetric analysis and Fourier transform infrared spectroscopy. The resulting ionogels present higher permittivity than pure silica and were used as the solid component for the development of new electrorheological fluids, presenting good ER behavior, mainly those prepared with IL1.

Negative electrorheological responses of mono-dispersed polypyrrole-SAN copolymer suspensions

The mono-dispersed polypyrrole (PPy)-poly(acrylonitrile-co-styrene) (SAN) copolymer particles were synthesized by emulsion polymerization and the electrorheological (ER) behavior of their suspensions was investigated. The suspensions of the mono-dispersed PPy-SAN copolymer particles showed negative ER effects. It was quite unexpected to negative ER effects for ER suspensions of conducting polymers or conducting polymer composites. The ER responses decreased with increasing electric field strength and particle size. A power-law dependence on the particle size and the electric field strength, τ(E)-τ0=−103.95 d−2E, showed a reasonable fit to the dynamic yield stress differences. It was observed that particles separated between the electrodes during experiments under the applied electric field. The migrations due to charge injection, by which the gap between the electrodes devoid of particles, seem to play a role in the yield stress decrease, leading to the negative ER response. Open image in new window

Electrorheology of aniline oligomers

Aniline oligomers were prepared by the oxidation of aniline with p-benzoquinone in aqueous solutions of methanesulfonic acid (MSA) of various concentrations. Their molecular structures were assessed by Fourier transform infrared spectroscopy. The electrorheological (ER) behavior of their silicone oil suspensions under applied electric field has been investigated. Shear stress at a low shear rate, τ 0.9, was used as a criterion of the rigidity of internal structures created by the application of an electric field. It was established from the fitting of the dielectric spectra of the suspensions with the Havriliak–Negami model that dielectric relaxation strength, as a degree of polarization induced by an external field contributing to the enhanced ER effect, increases and relaxation time, i.e., the response of the particle to the application of the field, decreases when a higher molar concentration of MSA is used. The best values were observed for suspensions of the sample prepared in the presence of 0.5 M of MSA. This suspension creates stiff internal structures under an applied electric field strength of 2 kV mm−1 with τ 0.9 of nearly 50 Pa, which is even slightly of higher value than that obtained for standard polyaniline base ER suspension measured at the same conditions. The concentration of the MSA used in the preparation of oligomers seems to be a crucial factor influencing the conductivity, dielectric properties and, consequently, rheological behavior, and finally ER activity of their suspensions.

Electrorheological behaviour under oscillatory shear of TiO2 rod-like particles prepared via microwave-assisted molten-salt synthesis

Titanium dioxide (TiO2) rod-like particles were synthesized by a simple and rapid microwave-assisted molten-salt method. The X-ray diffraction analysis and electron microscopy provided information on particle composition and morphology, respectively. It was found that during the synthesis process the crystalline phase of TiO2 transformed from anatase into rutile while the morphology changed from nanospheres into micrometer sized rod-like particles. The electrorheological (ER) properties were investigated via oscillatory shear tests. It was found that TiO2 rod-like particles based silicone oil suspensions exhibited higher ER activity than those of original anatase TiO2 nanoparticles probably due to side-by-side solid friction between particles as well as shorter time of their polarization. The changes in ER properties of rod-like particle based suspensions as a function of the applied electric field strength and particles weight fraction were also investigated.

Synthesis and electrorheological effect of Cr doped TiO2 nanorods with nanocavities in silicone oil suspensions

Titanium dioxide (TiO2) nanorods with nanocavities doped with chromium (Cr) were synthesized by hydrothermal method. The morphology of prepared nanorods was determined by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). The electrorheological (ER) behaviour of suspensions based on TiO2 was investigated under the steady shear, and the yield stress was chosen as a suitable tool for a comparison of ER performance. Some optimum in level of Cr doping of TiO2 was found.

The negative and positive electrorheological behavior and vibration damping characteristics of colemanite and polyindene/colemanite conducting composite

In this study, the electrorheological (ER) properties of colemanite and polyindene (94.8% PIn)/colemanite (5.2%) conducting composite were investigated by dispersion in silicone oil (SO). The zeta (ζ)-potentials and antisedimentation ratios of the materials were determined. Some parameters which affect the ER properties of all the dispersions such as the volume fraction, electric field strength (E), shear rate, frequency and temperature were investigated. The rather unusual behavior known as the negative ER effect was observed for colemanite/SO above E = 1.5 kV mm−1 and for PIn/colemanite/SO under all values of the electric field strength even at high volume fraction. This negative ER response was converted to a positive one by the addition of non-ionic surfactant. Furthermore, glycerol was used as a polar promoter and observed to enhance the ER activity of the colemanite/SO system. Creep-recovery tests were applied to all the dispersions studied to investigate their behavior under sustained shear stress. Finally, 28% and 30% vibration damping capacities were achieved using an automobile shock absorber for the glycerol/colemanite/SO and non-ionic surfactant/PIn/colemanite/SO systems under the E = 0.17 kV mm−1 condition, respectively.

Dynamic response of a graphene oxide-polyaniline composite suspension under an applied electric field

A suspension of semiconducting graphene oxide/polyaniline (GO/PANI) composite particles dispersed in silicone oil is considered as one of the potential candidates for an electrorheological (ER) fluid. The GO/PANI composite was synthesized by using chemical oxidation polymerization of aniline in the presence of a GO dispersion that contained GO that had been prepared by using a modified Hummers method. The characteristics of the composite were examined by using SEM images and FT-IR spectra and indicated the coexistence of GO and PANI in the composite. The GO/PANI-composite-based ER fluid was prepared by dispersing the fabricated particles in silicone oil, and its dynamic viscoelastic properties were measured using a rotational rheometer under different electric fields, which showed that the ER fluid exhibited typical solid-like ER behaviors.