Electrorheological Effect Research Articles

Transformation of Cellulose via Two-Step Carbonization to Conducting Carbonaceous Particles and Their Outstanding Electrorheological Performance.

In this study, cellulose was carbonized in two-steps using hydrothermal and thermal carbonization in sequence, leading to a novel carbonaceous material prepared from a renewable source using a sustainable method without any chemicals and, moreover, giving high yields after a treatment at 600 °C in an inert atmosphere. During this treatment, cellulose was transformed to uniform microspheres with increased specific surface area and, more importantly, conductivity increased by about 7 orders of magnitude. The successful transition of cellulose to conducting carbonaceous microspheres was confirmed through SEM, FTIR, X-ray diffraction and Raman spectroscopy. Prepared samples were further used as a dispersed phase in electrorheological fluids, exhibiting outstanding electrorheological effects with yield stress over 100 Pa at an electric field strength 1.5 kV mm−1 and a particle concentration of only 5 wt%, significantly overcoming recent state-of-the-art findings. Impedance spectroscopy analysis showed clear interfacial polarization of this ER fluid with high dielectric relaxation strength and short relaxation time, which corresponded to increased conductivity of the particles when compared to pure cellulose. These novel carbonaceous particles prepared from renewable cellulose have further potential to be utilized in many other applications that demand conducting carbonaceous structures with high specific surface area (adsorption, catalyst, filtration, energy storage).

Basic exploration and research on magnetoelectric synergistic rheological finishing

Both the magnetorheological effect and the electrorheological effect can effectively constrain and clamp abrasives for polishing processing. This paper proposes a magneto-electric synergy rheological finishing (MERF) method. Based on a magnetoelectric composite field simulation, magnetoelectric synergistic rheological finishing equipment is built. A polishing slurry with both electrorheological and magnetorheological effects is prepared for processing a 2-inch single-crystal silicon wafer. Comb-type electrodes and cylindrical flat-bottomed magnetic poles are used to construct magnetoelectric composite fields. Under the action of a magnetoelectric composite field, a hemispherical polishing pad with abrasives distributed in strips can be obtained. By conducting a test, a smooth and gentle arc cross section of the removed contour can be obtained. The removal rate of MERF was 4.04 mg/h, which was between those of electrorheological finishing (ERF) and magnetorheological finishing (MRF). The surface roughness Ra reached 1.80 nm, and the depth and width of the machining traces were the largest. Magnetoelectric synergistic rheological finishing equipment can realize processing under electric fields, magnetic fields, and magnetoelectric composite fields. The MERF method can effectively enhance the semifixed binding force and distributional uniformity of the abrasive and achieve a more efficient and uniform planarization process.

Electro-responsive electrorheological effect and dielectric spectra analysis of topological self-crosslinked poly(ionic liquid)s

By changing the amount of vinylimidazole grafted on phenyl ring, we designed and prepared a series of topological self-crosslinked poly(ionic liquid)s (TS-PILs) with different number of spacer arms by free radical polymerization. The influences of the number of spacer arms on the electrorheological (ER) effect of TS-PILs in insulating carrier liquid were studied by rheological test under electric stimulus and the influence mechanism was analyzed by broadband dielectric spectroscopy. It was found that the ER effect of TS-PILs containing organic counterion bis(trifluoromethane sulfonylimide) (TFSI-) increased with the increase of the number of spacer arms. Broadband dielectric spectra analysis showed that the increased ER effect with the number of spacer arms was attributed to the increase of interfacial polarization strength and the decrease of electrode polarization with the number of spacer arms. Activation energy analysis indicated that increasing the number of spacer arms could promote ion pair dissociation and ion number density but inhibit long-range movement of ions, which was responsible for the increase of interfacial polarization strength and the decrease of electrode polarization. The results provided a guidance insight for the design and preparation of high-performance crosslinked PIL-based ER materials.

Shear Motion Characteristics Analysis of Electrorheological Fluids Between Flat Disk and Corrugated Disk

In order to improve the transmission torque caused by the electrorheological effect, a corrugated disk is proposed to replace traditional flat disk by changing the electrode surface shape. The new mechanism puts the device in a shear-squeeze mode of operation. Based on the constitutive equation of electrorheological fluids, the shear motion characteristics of the ER fluids between the flat disk and the corrugated disk are analyzed, including the pressure distribution, torque equations, and the comparison with double-flat-disk mechanism. The analysis shows that compared with the double-flat-disk structure, the flat-disk-corrugated-disk structure can enhance the transmitted torque over 2.6 times under the same operating parameters. The magnification of the torque is not related with the curve number of the corrugated disc, but mainly depends on the structural parameters of the device and corrugations, and the characteristic parameters of electrorheological fluid. It is proved that the mechanism can provide new ideas and new methods for the engineering application of electrorheological transmission technology.

Evaporation-assisted phase separation preparation and electrorheological effect of poly(ionic liquid) microspheres with dual and mixed counterions

We prepare poly(ionic liquid) (PIL) microspheres containing dual counterion and single counterion in a unitary unit via an evaporation-assisted phase separation method, and study the influence of the number and type of counterions on the electrorheological (ER) effect and dielectric properties of the PIL microspheres. The morphology and structure of PIL microspheres are characterized and the ER effect of PIL microspheres in insulating carrier liquid is measured under electric fields. It shows that when the type of counterions is identical, the dual-ion PIL (D-PIL) microspheres have a stronger ER effect than that of the single-ion PIL (S-PIL) microspheres. Dielectric spectra analysis indicates that D-PIL microspheres have higher interfacial polarization rate compared to S-PIL microspheres due to enhanced charge density and ion transport dynamics according to Raman spectra and activation energy analysis. This should be responsible for the stronger ER effect of D-PIL microspheres. However, when the type of counterions is different, the ER effect of D-PIL microspheres is largely reduced. This is because the mixed alkali effect of mixed counterions significantly increases the activation energy of ion transport and decreases conductivity and interfacial polarization rate of PIL microspheres containing mixed counterions. The result can provide a new understanding of structure-property relationship for PIL-based ER material design and preparation.

Dielectric nanoparticle suspensions for increased electrostatic forces

Dielectric suspensions of nanoparticles for electrostatic force production applications have been developed. To avoid viscosity increases due to the electrorheological effect, aliphatically coated BaTiO3 nanoparticles were synthesized and mixed with n-decane to form concentrated dielectric suspensions. The synthesis and characterization of the nanoparticles and the suspensions are described. The increased electrostatic force on electrodes due to the increased relative permittivity of the dielectric suspensions is verified with force test stand measurements, consistent with a standard electrostatic model.

Impact of molecular chain structure of suspension phase on giant electrorheological performance

We demonstrate the impact of diester structure, in particular the alkyl chain length and branching structure, on the giant electrorheological (GER) effect and suspension stability. The existence of oil–particles interaction is of critical importance to induce the GER effect. To quantify GER performance and colloidal stability, we examine the yield stress, current density, field-off viscosity and sedimentation ratio with respect to the variation of chain length and branching structure. The oil–particles interaction is quantitatively analyzed by investigating the cluster size of particles in different diesters by a multiple light scattering analyzer, along with the wettability of different chain lengths of diesters and solid particles by the Washburn method. Our results indicate that long chain lengths favor the formation of particle agglomerates, thereby enhancing the GER effect (such as high yield stress). The attachment of branches on diester causes the formation of electronic correlation between branches and main chain, depending on the position of branches located, and hence results in superior GER performance and favorable suspension stability. An optimal GER fluid constituted by bis(2-ethylhexyl) sebacate is acquired with the achieved yield stress of 113 kPa at electric field strength of 4 kV mm−1 and the prominent integrated GER properties.

Electrorheology and dielectric polarization of backbone, pendant and cross-linked poly(ionic liquid)s

Backbone, pendant and cross-linked poly(ionic liquid) (PIL) particles with the same ion pair and similar ion number density have been prepared and the electro-responsive electrorheological (ER) effect of their suspensions in insulating carrier liquid has been comparably studied by rheology and dielectric spectroscopy. It has found that the ER effect of cross-linked PILs is strongest and that of backbone PILs is weakest. Dielectric spectrum analysis has showed that the difference of ER effect is mainly due to the difference in the ion leakage and effective interfacial polarization of PIL particles under electric fields. Although the backbone PILs have the largest interfacial polarization strength, its ion leakage conductance is also largest and this results in its weakest ER effect. The cross-linked PILs well restrains the ion leakage conductance and the ER effect is largely enhanced. The difference in ion leakage conductance and ER effect is further related to the difference of PIL matrix structure according to X-ray diffraction characterization. This study clarified the influence of matrix structure on ER effect and dielectric polarization of PILs and provided a guidance for the design of PIL ER materials.

THE NATURE OF THE ELECTRORHEOLOGICAL AND ELECTROPHORETIC EFFECTS OF DETONATION NANODIAMONDS SUSPENSIONS IN MINERAL OIL

Qualitative differences in the nature of the electrorheological response of a detonation nanodiamonds suspensions in mineral oil depending on the type of particle surface functionalization were established from a number of rotational and oscillation tests. The type of modification and the chemical composition of the surface for particles of hydrogenated and carboxylated nanodiamonds were studied by infrared spectroscopy. Particles morphology and their structural organization in a mineral oil medium were studied by small-angle X-ray scattering method. It was found that suspensions of hydrogenated and carboxylated particles under an electric field exhibit an electrorheological and electrophoretic effects, respectively. The reasons for the electrophoretic motion of carboxylated nanodiamonds in a mineral oil medium were analyzed in comparison with the previously observed effect in the medium of weakly amphiphilic polydimethylsiloxane (silicon oil). The water content on the surface of both hydrogenated and carboxylated nanodiamond particles was determined by Karl Fischer titration of suspensions. The correlation between the electrophoretic effect and the adsorbed water content on the surface of the particles was suggested. The method of rotational viscometry revealed the dependences of the static yield stress for suspensions filled with hydrogenated and carboxylated nanodiamonds at various electric field strength. The flow curves of the fluid filled with hydrogenated particles without and under an electric field were fitted by Bingham and Cho-Choi-Jhon rheological models. An analysis of the used models matching to practical results was performed. Based on the dependences of the storage and loss moduli on the deformation amplitude, a linear range of the viscoelastic properties of the fluid was revealed. An increase in the values of the storage and loss moduli, as well as a narrowing of the linear viscoelasticity range with an increase in the electric field strength was detected.

Dynamic Response of Polyindole Coated Zinc Ferrite Particle Suspension under an Electric Field.

ZnFe2O4 particles initially synthesized through a simple solvothermal method were coated using polyindole (PIn) to prepare an actively controllable core-shell typed hybrid material under both electric and magnetic fields. An advantage of this process is not needing to add the stabilizers or surfactants commonly used for uniform coating when synthesizing core or shell-structured particles. The synthesized ZnFe2O4/PIn particles have a lower density than conventional magnetic particles and have suitable properties as electrorheological (ER) particles. The expected spherical shape of the particles was proven using both scanning electron microscopy and transmission electron microscopy. The chemical characterization was performed using Fourier-transform infrared spectroscopy and X-ray diffraction analysis. To analyze the rheological properties, a ZnFe2O4/PIn based suspension was prepared, and dynamic rheological measurements were performed for different electric field strengths using a rotary rheometer. Both dynamic and elastic yield stresses of the ER fluid had a slope of 1.5, corresponding to the conductivity model. Excellent ER effect was confirmed through rheological analysis, and the prepared ER fluid had a reversible and immediate response to repeated electric fields.

Strong Electrorheological Performance of Smart Fluids Based on TiO2 Particles at Relatively Low Electric Field

Electrorheological (ER) fluids are a type of smart material with adjustable rheological properties. Generally, the high yield stress (>100 kPa) requires high electric field strength (>4 kV/mm). Herein, the TiO2 nanoparticles were synthesized via the sol–gel method. Interestingly, the ER fluid-based TiO2 nanoparticles give superior high yield stress of 144.0 kPa at only 2.5 kV/mm. By exploring the characteristic structure and dielectric property of TiO2 nanoparticles and ER fluid, the surface polar molecules on samples were assumed to play a crucial role for their giant electrorheological effect, while interfacial polarization was assumed to be dominated and induces large yield stress at the low electric field, which gives the advantage in low power consumption, sufficient shear stress, low leaking current, and security.

Research on shear stress of electrorheological fluid containing piezoelectric powders

This paper describes experimental trials that were performed to increase the electrorheological (ER) effect in ER fluids (ERFs) by introducing piezoelectric particles (PEPs). Five sample solutions were made using different PEPs, ER powders, and liquids that included ERFs provided with different solutions and silicone oil. The shear stress of each sample was measured by shearing the sample between parallel plate electrodes. Samples containing the PEP showed the same shear stress under steady voltage inputs but showed somewhat higher shear stress under sinusoidal voltage inputs. This suggests that mixtures of the piezoelectric powders (at approximately 5 wt.%) and the ERF may shorten the response time of the ERF to DC inputs or increase the response frequency to AC inputs.

Influence of molecular weight on electro-responsive electrorheological effect of poly(ionic liquid)s: Rheology and dielectric spectroscopy analysis

Poly[methylmethacrylate trimethylamine][hexafluorophosphate] (P[MTMA][PF6]) poly(ionic liquid)s (PILs) with different molecular weight (polymerization degree N = 6–652) were synthesized by free-radical polymerization. The influence of molecular weight on the electrorheological (ER) effect of P[MTMA][PF6] particles dispersed in insulating carrier liquid was studied by rheological test, and the reasons behind the influence was analyzed by dielectric spectroscopy. The result shows that when the molecular weight of P[MTMA][PF6] is less than ∼30,000 (N<∼100), the ER effect is sensitive to the molecular weight and it increases as the molecular weight increases; when the molecular weight exceeds ∼30,000 (N>∼100), the ER effect tends to saturate. Dielectric spectra analysis shows that the influence of molecular weight on the ER effect of P[MTMA][PF6] is closely related to the interfacial polarization and the leaking conduction of P[MTMA][PF6], which further depends on the changes of ionic conductivity of P[MTMA][PF6] particles and dissolution ability of P[MTMA][PF6] particles in carrier liquid with molecular weight. By activation energy calculation and XRD analysis, it demonstrates that the molecular level reason for the influence of molecular weight on conductivities, polarization and ER effect is related to the changes of the elastic potential energy of P[MTMA][PF6] matrix and the limiting ability of matrix for ion dissolution in carrier liquid with the molecular weight.

Smart Table Tennis Racket with Tunable Stiffness for Diverse Play Styles and Unconventional Technique Training

AbstractSmart technologies bring innovation to the life and sports arena. To adapt to diverse play styles and improve unconventional technique of table tennis players, a smart table tennis racket with tunable stiffness based on anisotropic electrorheological elastomers (EREs) is developed. The EREs are prepared in the designed mold under the electric field to form an anisotropic structure that consisted of electrorheological particles and facilitated the generation of interparticle saturation surface polarization and the local electric field. Therefore, the electrorheological property of anisotropic EREs is significantly promoted, attaining a relative electrorheological effect of 17 160% in shear mode, and the incremental shear storage and compression modulus of 5.2 and 6.4 MPa. By applying an electric field, the smart racket successfully changes the trajectory of balls, reduced ejection angle by 11% and increased ejection velocity by 2%.

Ionic-liquid-modified TiO2 spheres and their enhanced electrorheological responses

An ionic liquid functionalised silane agent, 1-(3-triethoxysilylpropyl)-3-methylimidazolium chloride (TESPM-IL), was prepared and used to fabricate ionic liquid (IL)-grafted titanium dioxide (IL-TiO2) spheres via a sol-gel process. Thermogravimetric analysis and Fourier transform infrared spectroscopy confirmed that TESPM-IL was attached to TiO2 spheres. Morphologies of the IL-TiO2 spheres were observed by scanning electron microscopy and transmission electron microscopy, indicating the rough surface and smaller size of the IL-TiO2 particles caused by the modification of TESPM-IL. The IL-TiO2 particles were applied as a new dispersed-phase material of electrorheological (ER) fluids. The ER effect of IL-TiO2 particles was studied and compared with that of pure TiO2 particles. It was found that, upon the introduction of TESPM-IL, both yield stress and storage modulus of the IL-TiO2 ER fluid were enhanced significantly, thus improving the ER effect of TiO2- or inorganic-based ER materials effectively. Dielectric analysis was also used to observe the interfacial polarization process of the particles, which confirmed the effect of the IL layer on the surface of the TiO2 particles.

Silica-based ionogels containing imidazolium ionic liquids and their electrorheological responses at room and elevated temperatures

In this study, we report the electrorheological (ER) effects of silica-based ionogels containing imidazolium ionic liquids (ILs) when dispersed in silicone oil at different temperatures. The amount of IL agent used in the synthesis process of the silica-based ionogels by a sol-gel method significantly affected morphologies of the silica-based ionogels, resulting in particles with rough surface and agglomerations. This electric-field-tunable rheological properties of the ionogel-based ER fluids were closely related to the dosage of ILs used in the synthesis process. With a proper amount of IL, the ionogels of SiO2-IL-0.5, SiO2-IL-0.8 and SiO2-IL-1.0 showed enhanced ER effects under steady shear flow with an applied electric field compared with pristine SiO2; however, excessive ILs in ionogel (SiO2-IL-1.88) could reduce the ER effect of the ER fluid. More importantly, upon modification by IL, the SiO2-IL-0.8 ionogel exerted the highest ER effect which was stable in the temperature range of 25−120 °C, showing good applicability at high temperature.

Electrorheological response behavior of H2Ti2O5@MoS2@SiO2 core-shell nanoparticles

In this paper, a novel H2Ti2O5@MoS2@SiO2 ternary composite material was prepared by a combination of dual hydrothermal method and controlled hydrolysis method, in which H2Ti2O5 nanotubes are tightly combined with hierarchical molybdenum disulfide, and the unique structure of titanate nano whiskers, including the loosely bound alkali metal ions between the titanate layers with high dielectric constant and the large aspect ratio, which induce active response to the electric field. Flower-like molybdenum disulfide provides electrical conductivity, and silicon dioxide as a insulative coating layer can suppress excessive the electrical conductivity of the two-dimensional material. The morphological evolution was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results of showed that the sheet-shaped molybdenum disulfide coated with curved H2Ti2O5 nanotubes showed a honeycomb structure with uniform size. Silicon oxide acts as a cladding layer to increase the thickness of the flakes. The existence of H2Ti2O5, molybdenum disulfide and silicon dioxide is confirmed by X-ray powder diffractometer (XRD) and Fourier transform infrared spectroscopy (FT-IR). The prepared product was confirmed by XPS, BET test and electrorheological rheometer. Core/shell nanoparticles not only exert the active response characteristics of titanate nanoparticles and molybdenum disulfide to electric field, but also inherit the excellent characteristics of a core-shell structure produced by the interface polarization and the synergistic effect of the polar groups on the surface of the two-dimensional material further enhance the electrorheological effect.

Understanding the enhanced electrorheological effect of reduced graphene oxide‐supported polyaniline dielectric nanoplates by a comparative study with graphene oxide as the support core

Graphene has attracted scientific interest as a substrate or additive for developing high-performance stimuli-responsive materials. Research on graphene-based polymer dielectric composites has shown an enhanced electroresponsive electrorheological (ER) effect. However, the mechanism behind the enhanced electroresponse is still incompletely understood. Here, an investigation was performed into dielectric polarization and the ER effect of reduced graphene oxide-supported polyaniline nanoplates by comparing them with pure granular polyaniline and graphene oxide-supported polyaniline nanoplates based on dielectric spectroscopy and rheologic analysis. We discovered that both anisotropic morphology and electrical properties have dominant roles in the enhanced ER effect of reduced graphene oxide-supported polyaniline nanoplates, whereas only anisotropic morphology has a dominant role in the enhanced ER effect of graphene oxide-supported polyaniline nanoplates. The analysis also showed that reduced graphene oxide-supported polyaniline nanoplates have a good ER response to both DC and AC electric field actions in the wide shear rate region. This is highly desirable for practical engineering applications. Therefore, the analysis reveals the reason for the enhanced ER effect of reduced graphene oxide-supported polyaniline nanoplates and also may provide a guide for designing high-performance ER materials for practical engineering applications by combining the advantages of conducting a reduced graphene oxide core and ER active shell.

In situ X-ray analysis of montmorillonite suspensions in polydimethylsiloxane: Orientation in shear and electric field

The behavior of electrorheological fluids filled by particles with a high aspect ratio was studied in situ by X-ray scattering using special cell. An orientation phenomena of particles in suspensions of variously modified montmorillonites at low concentrations under electric field and shear stress was clearly observed. It has been revealed that the type of modifier in clay structure plays a crucial role for the particles orientation under electric field. The relationship between the electrorheological behavior of suspensions and the filler structuring was discovered. The paper discussed the reasons of different particles organization depending on external influence. Using a simple model, a road map of possible structural states of suspensions was proposed. The prospects of in situ X-ray studies to comprehending the mechanism of electrorheological effect have been shown.

Self-assembly, liquid crystalline behavior and electrorheological performance of phthalocyanine-contaning polysiloxanes

Series of phthalocyanine-based ionic liquid-crystalline polysiloxanes (ILCPs) were self-assembled by bromo-polysiloxanes and zinc tetraaminophthalocyanine, and their chemical structure, thermal and liquid-crystalline (LC) behavior were characterized by various experimental techniques. The ILCPs exhibited hexagonal columnar phase and SmA phase. The effects of ionic phthalocyanine content and LC phase on the dielectric properties including dielectric constant and dielectric loss were investigated, which was closely related to their electrorheological (ER) effect. The ILCPs-based ER fluids (ERFs) were prepared by the ILCPs and silicone oil, and the ER performance was investigated at controlled test conditions. The ER effect increased with the increase of ionic phthalocyanine moieties for these ERFs. Furthermore, the ER efficiency of the ERFs at 330 K was much higher than that at 300 K at the constant conditions. The real-time response experiments of the ERFs was performed by switching alternately turned on or off the electric field, illustrating a synergetic rearrangement and orientation of the LC mesogens and the ionic phthalocyanine moieties along the direction of the electric field. Moreover, the ERFs showed good sedimentation property due to good compatibility between ILCPs’ polysiloxane matrix and the polysiloxane-based silicon oil.