Electrorheological Effect Research Articles

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.

Preparation of Cellulose/Laponite Composite Particles and Their Enhanced Electrorheological Responses.

Cellulose, as a natural polymer with an abundant source, has been widely used in many fields including the electric field responsive medium that we are interested in. In this work, cellulose micron particles were applied as an electrorheological (ER) material. Because of the low ER effect of the raw cellulose, a composite particle of cellulose and Laponite was prepared via a dissolution–regeneration process. Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) were used to observe the morphologies and structures of the composite particles, which were different from pristine cellulose and Laponite, respectively. The ER performances of raw cellulose and the prepared composite were measured by an Anton Paar rotational rheometer. It was found that the ER properties of the composite were more superior to those of raw cellulose due to the flake-like shapes of the composite particles with rough surface. Moreover, the sedimentation stability of composite improves drastically, which means better suspension stability.

Is Chitosan the Promising Candidate for Filler in Nature-Friendly Electrorheological Fluids?

In this study, an electrorheological effect of the suspensions containing porous chitosan particles in olive oil in a wide range of electric fields is reported. Porous chitosan particles were produ...

Electrorheological Effect of Gold Nanoparticles Coated with Fluorescent Mesogenic Groups Dispersed in Nematic Liquid Crystal

The electrorheological (ER) properties of composite materials consisting of a nematic liquid crystal (LC) and gold nanoparticles (GNPs) coated with bistolane-based mesogenic groups were studied. The GNPs were coated by normal alkyl chains and the fluorescent LC compounds, of which the molecular structure was similar to that of the LC matrix. The dispersity of the GNPs in the nematic LC was investigated by polarizing optical microscopy (POM). In order to improve the ER effect of the composite, a simple strategy was investigated from the viewpoint of a material design in surface-modified GNPs by lateral substitution of the mesogenic groups. The presence of the GNPs in the nematic LC led to a slightly enhanced ER effect compared to that observed for only the nematic LC. This study demonstrates the potential of a hybrid system consisting of LCs and GNPs to yield a larger ER effect.

Preparation and Electrorheological Properties of Peanut‐Like Hollow Core–Shell Structure TiO2@SiO2 Nanoparticles

Although titanium oxide has a high dielectric constant, ordinary titanium oxides are not a good electrorheological (ER) fluid material. Herein, hollow peanut‐like titanium oxide spheres are synthesized by hydrothermal method, and then coated with silicon oxide to form core–shell hollow TiO2@SiO2 spheres. The structure is characterized by different methods, and the TiO2@SiO2 composite particles are dispersed in silicone oil to prepare an ER suspension. The ER effect of 10% TiO2@SiO2‐based ER fluid under different electric field strengths is tested, and its performance is analyzed. The results show that the coated particles significantly enhance the current meter performance. The shear stress value exceeds 200 Pa at an electric field strength of 3.0 kV mm−1. The shear stress, shear viscosity, switching effect, and dielectric behavior of the base ER fluid are studied. And, the cause of this strong ER effect is studied. In the end, it is found that TiO2@SiO2 peanut‐shaped composite core–shell particles have a good ER effect and which is a kind of ER candidate material with simple preparation and development prospect.

Electrorheology of polyindole

Polyindole particles were prepared by the oxidative polymerization, where ammonium peroxydisulfate was used as an oxidant at several mole ratios to indole. Prepared spherical micrometre-sized polyindole particles were further used as a dispersed phase in silicone-oil electrorheological (ER) fluids and their rheological behaviour was investigated in the presence and in the absence of an electric field. While different oxidant-to-indole mole ratios did not affect the size and morphology of the particles, their electric and dielectric properties were significantly changed. The highest ER effect was observed for the ER fluid based on the particles with low oxidant-to-indole mole ratio (1:1). Such system exhibited yield stress around 100 Pa at 10 wt% concentration of solid phase. Chain-like structures created upon an application of an electric field were further investigated using an optical microscopy, where significant disparities were found according to electric and dielectric properties of the particles. These findings clearly show that varying mole ratio between the indole and oxidant provides systems with tuneable ER effect.

Effect of a temperature threshold on the electrorheological performance of ionic liquid crystal polyanilines

A series of ionic liquid crystal polyanilines (ILCPs) electrorheological (ER) compounds were synthesized by use of polyaniline, naphthalene disulfonic acid and pyridinyl-containing mesogen. The chemical structure, thermal property, morphology, liquid-crystalline behavior, dielectric property and ER effect of the ILCPs-based ER fluids were characterized by use of various experimental techniques. The synthesized ILCPs displayed nematic liquid-crystalline phase, and the different mesogens played a determinant role in the liquid crystal behavior. The experimental results about dielectric property of the ILCPs suggested that both dielectric constant and dielectric loss increase with raising the temperature, showing a sudden change around glass-transition temperature. The ILCPs-based ER fluids contained an integrated character of liquid crystal, poly(ionic liquid) and polyaniline-base ER suspensions. These characteristics had strong dependence on operating temperature, and a temperature threshold was observed on the ER performance. The shear stress of the ER fluids increased abnormally near glass-transition temperature, which was due to the synergetic effect between the mesogenic orientation and the stretched polyaniline droplets induced by the electric field.

Creating a New Elastomeric Material with a Polyimide Filler and Studying its Viscoelastic Properties under Applied External Electric Fields and Dynamic Loads

Electrorheological elastomers (EREs) have viscoelastic properties controllable by external electric fields. For their application, it is necessary to investigate the rheological properties of EREs under various loading conditions. In this work, anisotropic EREs based on a silicone rubber with 10 wt% of PI-Na polyimide particles oriented in an electric field were first obtained. Their elastic properties were evaluated in relation to the frequency and amplitude of strain in an electric field of strength from 0 to 2 kV/mm. The elasticity of the material investigated increased by 50% when the strength of electric field raised to 1.8 kV/mm. The maximum electrorheological effect was found to be at 25°C.

Study on microscale flow characteristics of electrorheological Fluids

Electrorheological fluid is a kind of intelligent material whose rheological properties change rapidly and reversibly under the action of external electric field, It has a broad prospect in practical engineering application. It is found in the research progress of electrorheological fluids. The time scale and space scale of the electrorheological effect are very small, and the flow process has some micro-scale flow characteristics. In this paper, the dynamics of dielectric particles in electrorheological fluids under static and dynamic coupling fields is numerically simulated by dissipative particle dynamics method. The influence of surface force under static field on the submicrostructure of Electrorheological fluid and the influence of electroviscosity under dynamic coupled field on the flow rate of Electrorheological fluid are also studied.

Liquid-crystalline behaviour and electrorheological effect of phthalocyanine-based ionic liquid crystals

ABSTRACT Series of phthalocyanine-based ionic liquid crystals (PILCs) electrorheological (ER) materials were synthesised using brominated polyesters and a phthalocyanine (Pc)-containing monomer, and the chemical structure, liquid-crystalline behaviour, dielectric property and ER performance were characterised. All PILCs showed nematic phase, but some PILCs with more phthalocyanine moieties showed discotic hexagonal columnar mesophase. The dielectric permittivity increase with the increasing temperatures, but decrease with the increase of frequency for these PILCs. The PILCs-based electrorheological fluids (ERFs) contained an integrated character of liquid crystal, poly(ionic liquid) and Pc-base ER suspensions. The ERFs were made by PILC particles and silicone oil, and the ER effect was investigated at controlled test conditions including concentration, electric field strength, temperature and shear rate. When the ERFs were applied an external electric field strength, the shear stress increased instantly, and they showed non-Newtonian behaviour. At the same conditions, the ER effect improved as the measured temperature raised. Furthermore, the ER effect increased with the increase of ionic Pc moieties in the polymer systems. These results were originated from the synergetic effect among the mesogenic orientation and rearrangement of ionic Pc droplets induced by the electric field, forming an alignment-aggregated fibrillation chain.

Enhanced electrorheological activity of porous chitosan particles

Novel porous filler for electrorheological fluids was fabricated from chitosan via freeze drying technique. An exceptional electrorheological effect was discovered in suspensions of polydimethylsiloxane (silicone oil) filled by highly porous chitosan particles. The electrorheological activity was studied by rotational rheometry and visualized by optical microscopy. High porosity of the filler allows preparing highly efficient electrorheological fluids at rather low (< 1 wt%) concentration of dispersed phase. The mechanism of chain-like structure formation was considered. The electrorheological behavior of suspensions and the filler structural organization at different concentration were comprehended in terms of dielectric properties. The rheological data were approximated by Bingham and Cho-Choi-Jhon equations. The sedimentation stability of chitosan suspensions in polydimethylsiloxane was significantly affected by particles porosity.

Detonation nanodiamonds dispersed in polydimethylsiloxane as a novel electrorheological fluid: Effect of nanodiamonds surface

Using deagglomerated nanodiamond particles of 4–5 nm suspended in polydimethylsiloxane (PDMS) we have fabricated fluids demonstrated pronounced electrorheological effect. It has been revealed that the type of functional groups on nanodiamond particle surface plays a crucial role in the behavior of the suspensions under electric field. Suspension of hydrogenated nanodiamonds has demonstrated the most powerful electrorheogical effect. The high values of yield stress of the order of 80–90 Pa have been detected at extremely low concentrations of nanodiamond particles (3–4 wt%). The suspensions has outstanding sedimentation stability: the sedimentation ratio is more than 90% after 30 days. A power law dependence of the yield stress on the electric field, τ ∼ E1.0-1.5 indicates mainly the conduction mechanism of the effect. Suspensions of carboxylated nanodiamonds in PDMS reveal qualitatively different behavior and the electrophoresis occurs. The paper discusses the reasons of different rheological behavior depending on nanodiamond surface functionalization. The prospects of nanodiamonds application as filler for electrorheological fluids have been shown.

Temperature-dependent electrorheology of a suspension based on copolymeric P(NIPAM-co-[AMIm]Cl) colloidal particles

A imidazolium-based poly (ionic liquid), poly(1-allyl-3-methyl imidazolium chloride) (P[AMIm]Cl) was combined with the temperature-sensitive polymer poly(N-isopropylacrylamide) (PNIPAM) via random copolymerisation of the monomers [AMIm]Cl and NIPAM. The synthesised copolymer was characterised by nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscope (SEM). Then its stimuli-responsive properties were studied at different electric field strengths and temperatures when it was dispersed in silicone oil. It was found that the colloidal copolymer particles were electro-responsive, showing excellent electrorheological (ER) effect. It was interesting that the ER effect of the copolymer was temperature-dependent. As the temperature increased from 5 °C to 50 °C, the dynamic yield stress of the suspension was found to increase with temperature. The temperature dependence of both yield stress and current density became stronger as the temperature was higher than 30 °C. The significant temperature-dependence of the suspension was attributed to the PNIPAM segment in the copolymer which could be swelled by silicone oil at higher temperature.

Dielectric Polarization and Electrorheological Response of Poly(ethylaniline)-Coated Reduced Graphene Oxide Nanoflakes with Different Reduction Degrees.

We prepared poly(ethylaniline)-coated graphene oxide nanoflakes and then treated them with different concentrations of hydrazine solution to form dielectric composite nanoflakes having different reduction degrees of reduced graphene oxide core and insulating polyethylaniline shell (PEANI/rGO). The morphology of PEANI/rGO was observed by scanning electron microscopy, while the chemical structure was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectrometer. The influence of reduction degrees on the conductivity, dielectric polarization and electrorheological effect of PEANI/rGO in suspensions was investigated by dielectric spectroscopy and rheological test under electric fields. It shows that the PEANI/rGO has two interfacial polarization processes respectively due to rGO core and PEANI shell. As the number of hydrazine increases, the conductivity and polarization rate of rGO core increase. As a result, the difference between the polarization rate of rGO core and that of the PEANI shell gradually becomes large. This increased difference does not significantly decrease the yield stress but causes the flow instability of PEANI/GO suspensions under the simultaneous action of electric and shear fields.

Role of Phase-Dependent Dielectric Properties of Alumina Nanoparticles in Electromagnetic-Assisted Enhanced Oil Recovery.

The utilization of metal-oxide nanoparticles in enhanced oil recovery (EOR) has generated considerable research interest to increase the oil recovery. Among these nanoparticles, alumina nanoparticles (Al2O3-NPs) have proved promising in improving the oil recovery mechanism due to their prominent thermal properties. However, more significantly, these nanoparticles, coupled with electromagnetic (EM) waves, can be polarized to reduce water/oil mobility ratio and create disturbances at the oil/nanofluid interface, so that oil can be released from the reservoir rock surfaces and travelled easily to the production well. Moreover, alumina exists in various transition phases (γ, δ, θ, κ, β, η, χ), providing not only different sizes and morphologies but phase-dependent dielectric behavior at the applied EM frequencies. In this research, the oil recovery mechanism under EM fields of varying frequencies was investigated, which involved parameters such as mobility ratio, interfacial tension (IFT) and wettability. The displacement tests were conducted in water-wet sandpacks at 95 °C, by employing crude oil from Tapis. Alumina nanofluids (Al2O3-NFs) of four different phases (α, κ, θ and γ) and particle sizes (25–94.3 nm) were prepared by dispersing 0.01 wt. % NPs in brine (3 wt. % NaCl) together with SDBS as a dispersant. Three sequential injection scenarios were performed in each flooding scheme: (i) preflushes brine as a secondary flooding, (ii) conventional nano/EM-assisted nanofluid flooding, and (iii) postflushes brine to flush NPs. Compared to conventional nanofluid flooding (3.03–11.46% original oil in place/OOIP) as incremental oil recovery, EM-assisted nanofluid flooding provided an increase in oil recovery by approximately 4.12–12.90% of OOIP for different phases of alumina. It was established from these results that the recovery from EM-assisted nanofluid flooding is itself dependent on frequency, which is associated with good dielectric behavior of NPs to formulate the oil recovery mechanism including (i) mobility ratio improvement due to an electrorheological (ER) effect, (ii) interfacial disturbances by the oil droplet deformation, and (iii) wettability alteration by increased surface-free energy.

Experimental studies of electrorheological properties of lubricating oils containing ionic liquid. Part 3. Microscopic examination of the ER effect mechanism

The article presents the results of in situ microscopic observations of quasihomogenic mixtures of hydrocarbon oils containing ionic liquids. Observations were made using NIKON ECLIPSE LV 100 D optical microscope. The mechanism of generating the ER effect in two mixtures was observed, i.e., in silicone damping liquid GP-1, which is polimethylsiloksane mixture containing 2% (v/v) of ionic liquid CJ 001, i.e., tetrafluoroboran 1-methyl-3-octyloxymethylimidazolium and base polialfaolefine oil PAO-6 which containing 2% (v/v) of ionic liquid CJ 008, i.e., trihexyltertradecylfosfonium bis(trifluoromethylsulfonyl) imide as well as in the two-component standard liquid LID3354s. The ob-servations carried out showed that the prepared mixtures had generated the ER effect. At the threshold value E = 0.3 kV·mm–1, the ER effect disappeared. Photographs, presented in the paper, show changes in the structure of mixtures containing ionic liquids that occur under the influence of an external elec-tric field, consisting in the formation of „fibril chains and/or fibril streams” and then, their destruction and accumulation of ionic liquid particles at the electrodes. Keywords: electrorheological effect (ER), lubricating oils, ionic liquids, microscopy.

Preliminary Insights into Electro-Sensitive Ecolubricants: A Comparative Analysis Based on Nanocelluloses and Nanosilicates in Castor Oil

The newest generation of lubricants needs to adapt to stricter environmental policies. Simple and sustainable formulations with tunable rheological properties under the action of electric potentials may be the key. The present research explored the feasibility of producing electro-sensitive ecolubricants based on nanocellulose (crystalline and fibrillar) or nanoclay (Cloisite 15A montmorillonite and halloysite nanotubes) dispersions in castor oil, at concentrations that ranged from 2 to 6 wt.%. Broadband dielectric spectroscopy (BDS) measurements allowed for a first estimate on the electro-responsive potential of the nanofluids. The nanocelluloses and the montmorillonite suspensions presented a relaxation event in the dielectric loss, ε″, centered at ca. 2–4 kHz, which is related to interfacial polarization. Moreover, their actual electro-rheological (ER) effect under high electric potentials up to 4 kV/mm was assessed by determining the magnitude of the yield stress from steady flow curves at 25 °C. It was found that the nanocelluloses and the montmorillonite showed an enhancement of three orders of magnitude in their yield stress values at 4 kV/m. This enhancement was much greater than in the halloysite nanoclay, which did not exhibit any polarization). This is the starting point for the development of environmentally friendly ER lubricating fluids, based on nanocellulose and montmorillonites (layered nanosilicates), which might assist in reducing the friction and wear through the application of controlled electric fields.

Influence of geometry of mobile countercations on conductivity, polarization and electrorheological effect of polymeric anionic liquids at ice point temperature

To understand structure-property relationship and guide molecular design of poly(ionic liquid)-based electrorheological materials with high performance at low temperature, we investigated geometry influence of mobile counterions in poly(ionic liquid)s on glass transition temperature, conductivity, polarization, and electrorheology at 0 °C by synthesizing poly[4-styrenesulfonyl (trifluoromethylsulfonyl) imide]-based anionic poly(ionic liquid)s containing mobile countercations with similar molecular weight but different geometries. It found that as countercations changes from tetrahedral to planar geometry, the glass temperature decreases but the conductivity and polarization rate increase and, consequently, the electrorheological effect at 0 °C increases. Raman spectra, density functional theory calculation and activation energy analysis indicated that as countercations change from tetrahedral to planar geometry, the dissociation and transport of countercations are promoted due to increased plasticization effect, and this is responsible for poly(ionic liquid)s with planar countercations have larger ionic conductivity and interfacial polarization for stronger electrorheological effect at low temperature.

Electrorheological Fluids Based on Bismuth Ferrites BiFeO3 and Bi2Fe4O9

A comparative analysis has been made for the dielectric and electrorheological properties of suspensions of highly dispersed powders of bismuth ferrites BiFeO3 and Bi2Fe4O9 in polydimethylsiloxane PMS-300. Dielectric characteristics (dielectric constant, dielectric loss tangent) for the suspensions in frequency range 2.5–106 Hz have been determined and non-Debye character of relaxation processes in these systems has been revealed. The measured values of dielectric constant for the disperse bismuth ferrites at zero and infinite frequency (e0 and e∞) are 150 and 59 for BiFeO3, 22 000 and 14 for Bi2Fe4O9, respectively. Electrorheological properties of bismuth ferrite suspensions in static electric field (up to 5 kV) in tension, compression, and shear modes have been analyzed. It has been found that the values of electrorheological effect for BiFeO3 suspensions in polydimethylsiloxane PMS-300 are small even at high concentrations of disperse phase (60 wt %). On the contrary, the suspensions of highly disperse Bi2Fe4O9 exhibit distinct electrorheological effect. For 80 wt % Bi2Fe4O9 suspension, the tensile yield point reached ~7 kPa in electric field of 5 kV, while compressive stress was 12 kPa.

Enhanced Electrorheological Properties of PMMA–Titanium Oxide Nanocomposites

The electrorheological (ER) effect is crucial for development of responsive materials controlled by electric fields. To exploit the ER effect for designing better phase-change materials with improv...