Electrorheological Behavior Research Articles

Preparation of a MIL-125/MoS2/SiO2 Ternary Nanohybrid and Its Smart Electrorheological Behavior.

In this work, a kind of ternary hybrid material, MIL-125/MoS2/SiO2, was prepared by a solvothermal and Stöber method. In this system, MIL-125, as the matrix material, not only furnishes a large specific surface area for MIL-125/MoS2/SiO2, thereby providing a basis for stronger interfacial polarization, but also effectively enhances the antisettlement ability of the electrorheological fluids (ERFs). Different characterizations, such as scanning electron microscopy, transmission electron microscopy, XRD, XPS, FT-IR, BET, electron mapping, etc., were used to analyze the ternary nanohybrid. The ERFs prepared by combining the different advantages of the three materials in the hybrid system were studied by a HAAKE high-speed rotary rheometer. In addition, the combination of MoS2 and SiO2 provides suitable electrical conductivity and dielectric properties for the system to promote the generation of interface polarization, ensuring that the entire system exhibits stronger electrorheological behavior without electrical breakdown and thus obtains higher shear stress.

Rheology and electrorheological effects of waxy oils with different carbon number distribution

High-voltage electric treatment is an emerging technology for enhancing the cold flowability of crude oil. The primary mechanism involves the accumulation of charged particles (resins and asphaltenes) onto wax particles under the electric field. This electrorheological effect varies with different oil compositions. We have investigated the impact of resins and asphaltenes on the electrorheological behaviors of waxy oils. However, the impact of the carbon number distribution of wax on this effect remains unexplored. Therefore, the objective of this work is to investigate the interaction between waxes with various carbon numbers and charged particles and its impact on the electrorheological behaviors of waxy oils. Model waxy oils containing distinct wax fractions (paraffin and microcrystalline waxes) and varying charged particle concentrations were prepared and studied. The results unveiled that microcrystalline wax model oils exhibited substantial reductions in viscosity and yield stress after electric treatment, up to 80% and 60%, respectively, surpassing the improvements observed in paraffin wax model oils which were less than 50%. This disparity is attributed to the better capacity of resins and asphaltenes to be eutectic with paraffin wax, improving the original flowability of paraffin wax model oil, thus involving fewer charged particles in the interaction with wax under electric treatment, resulting in a weakened electrorheological effect. Resins and asphaltenes struggle to form eutectic mixtures with microcrystalline wax, resulting in minimal flowability improvement of microcrystalline wax model oils by charged particles. Consequently, under the electric field, a substantial proportion of free resins and asphaltenes can interact with microcrystalline wax particles, leading to superior electrorheological effects in microcrystalline wax model oils.

Electrorheological behavior of cellulose in silicon oil. The effect of filler morphology

Electrorheological behavior of cellulose in silicon oil. The effect of filler morphology

Synthesis and electrorheological behaviour of silica-coated porous metal-organic frameworks

In this paper, Ti-based metal-organic frameworks (MOF-Ti) with internal holes were prepared by a solvothermal method. The Stöber hydrolysis method was used to coat silicon dioxide (SiO2) on the surface of MOF-Ti with ethyl silicate as the silicon source, and the conductivity of the composite particles was controlled by the amount of TEOS added. Furthermore, core-shell MOF-Ti@SiO2 composite nanoparticles were successfully synthesized. Some analyses were performed to determine the morphology, crystal structure, elemental state, and N2 adsorption/desorption properties of MOF-Ti@SiO2 composite particles, and the results show that the synthesis of core/shell structure composite particles was successful. The electrorheological fluid (ERF) with a concentration of 10 wt% made from composite particles demonstrated good electrorheological (ER) performance and anti-settlement capacity. It has been found that the amount of TEOS has a significant impact on the ER performance of ERFs. Furthermore, it is also found in dielectric performance analysis that MOF-Ti with internal holes exhibited a distinctive dual relaxation peak in the ERFs and showed stronger interfacial polarization after SiO2 coating, which is useful for enhanced ER behaviour.

The building blocks behind the electrohydrodynamics of non-polar 2D-inks

This work provides a complete rheological characterization of 2D-inks in electric fields with different intensities and orientations to the imposed flow field. 2D nanomaterials used in this study are graphene nanoplatelets, hexagonal boron-nitride, and molybdenum disulfide. These materials with different electric properties are dispersed in a non-polar solvent (Toluene) with different concentrations of Ethyl Cellulose (EC), providing Newtonian or viscoelastic characteristics. Shear rheology tests show that the presence of nanoparticles barely changes the fluid behavior from the carrier fluid, and the application of an electric field perpendicular to the flow does not result in electrorheological behavior. However, extensional experiments, which mimic the actual EHD jet printing conditions, allowed the observation of the influence of both the particles and the electric field aligned on the filament thinning process. It was observed that the electric field generates vortices due to an electrophoretic effect in the carrier fluid when EC is present in the formulations, which has severe consequences on the stability of the liquid bridges, whereas it scarcely affects the shear viscosity; additionally, the kind of 2D nanoparticles modifies also the conductivity and permittivity of the solution, inducing Maxwell stresses that also make the filament more stable against surface tension.

Electrorheological behavior of heat-treated sepiolite suspension

Electrorheological behavior of heat-treated sepiolite suspension

Core-Shell-Structured Electrorheological Fluid with a Polarizability-Tunable Nanocarbon Shell for Enhanced Stimuli-Responsive Activity.

The incorporation of nanocarbon-based materials into electrorheological fluids has been shown to be an effective means of improving the electrorheological (ER) response. However, the mechanism of the sp2/sp3-hybridized carbon structure and high ER response is still under investigation. Herein, barium titanate@nanocarbon shell (BTO@NCs) composites are proposed and prepared by introducing carbonized polydopamine (C-PDA) into a shell. When the polymerization time of dopamine is tuned, the shell thickness, surface polar functional groups, and sp2/sp3-hybridized carbon can be effectively controlled. The maximum yield stress of the BTO@NCs-24 h ER fluid reaches 2.5 kPa under an electric field of 4 kV mm-1, which is attributed to the increased content of sp3 C-OH and oxygenous functional groups within the shell, resulting in a rapidly achievable polarization. Furthermore, the SiO2@NCs and TiO2@NCs ER fluids are also prepared with enhanced ER behavior in these phenomena, confirming an approach to high-performance ER fluids based on nanocarbon composites.

Synthesis of polystyrene/poly(o-anisidine) core/shell structured microparticle and its electrorheological behavior

We fabricated core/shell typed semiconducting poly(o-anisidine) (POA) coated polystyrene (PS) composite microspheres and used them as an electrorheological (ER) material. Micro-spherical PS seeds were initially fabricated through a dispersion polymerization method, and the semiconducting POA was coated onto the PS seeds through a chemical oxidation polymerization technique. Uniform coating of the POA onto the PS particles was confirmed via morphology analysis. Their chemical structures and thermal behaviors were identified using Fourier transform infrared spectroscopy and thermogravimetric analysis, respectively. Using a rotational rheometer, PS/POA based ER fluid (5 vol%) exhibited a yield stress of about 72 Pa under an electric field strength of 2.5 kV/mm. Over the range of electric field strength, both dynamic and elastic yield stresses grew in proportion to the power of 1.5 of the electric field strength. Dielectric properties of the ER suspension were also found to be correlated with its ER properties.

Engineering Conductivity and Performance in Electrorheological Fluids Using a Nanosilica Grafting Approach

Carbonization is considered an effective process for the preparation of carbon-rich solids for various applications. Raw carbonaceous particles however often possess high electrical conductivity, limiting their applicability in electrorheology. To address this drawback, the carbonaceous particles prepared from glucose through hydrothermal synthesis, followed by thermal carbonization in an inert atmosphere, were subsequently coated by compact and mesoporous nanosilica, giving rise to semiconducting particles. The successful coating was confirmed using transmission electron microscopy and spectroscopic analysis, and the composite particles were further used as a dispersed phase in electrorheological (ER) fluids of concentration 5 wt %. While an ER fluid based on pure carbonized particles caused a short circuit of the measuring device at the electric field of intensity 1 kV mm–1, the ER behavior of its analogue based on mesoporous silica-coated particles was successfully measured up to 3 kV mm–1, giving a high yield stress exceeding even the values estimated for ER fluids based on similar carbonaceous particles coated with a compact silica layer. Even though the conductivity decreased only about one order of magnitude after the coating process, the dielectric properties of the prepared ER fluid differed significantly, the relaxation process was shifted to lower frequencies, and most importantly, the dielectric relaxation strength increased, indicating an increased amount of interactions. The presence of mesoporous nanosilica further enhanced the sedimentation stability of the ER fluids when compared to its analogue with the compact silica coating, expanding the scope of practical applicability.

Experimental design optimization of different vegetable oils based electrorheological fluids

Electrorheological (ER) behavior under applied electric field stimulus was optimized for three different vegetable oils (VOs) with lead dioxide (PbO2) particles and additives. Response surface methodology tool Box-Behnken method (BBM) was applied to optimize experimental parameters such as electric field strength, PbO2 particle size, and additive volume to determine the optimized dynamic viscosity responses for these ER fluids. Three different VOs such as olive, sunflower and soyabean oils were used to record the oil chemical structure effect on the dynamic viscosity of the ER fluids. BBM resulted maximum dynamic viscosity values viz., 139.4, 137.6 and 136.4 mPa.s. respectively for olive, sunflower, and soyabean oils suspensions at optimized parameters such as electric field strength of 2.43 kV/mm, PbO2 particle size of 4.6 µm, and additive volume of 5.6 ml. In addition, olive oil ER fluid shows the highest dynamic viscosity among the three fluids indicating the chemical structure of the VOs affects the viscosity performance.

A further investigation to mechanism of the electrorheological effect of waxy oils: Behaviors of charged particles under electric field

Exposing waxy oils to an electric field may significantly improve their cold flowability. Our previous study has shown that interfacial polarization, i.e., charged particle accumulation on the wax particle surface, is the primary mechanism of the electrorheological behavior of waxy oils. However, the way that charged particles interact with wax particles under an electric field remains unknown. In this study, we found no viscosity and impedance change for two waxy crude oils after their exposure to a high-voltage electric field. However, the yield stresses were reduced obviously. We thus proposed that the collision of colloidal particles such as resins and asphaltenes with the wax particles could be an essential mechanism that the wax particle structure was weakened. To verify this hypothesis, a series of ad hoc experiments were carried out, i.e., by performing electrorheological tests on model waxy oils containing additives removable under an electric field, including electrically-neutral colloidal particles (Fe3O4), charged colloidal particles (resins), and oil-soluble electrolyte (C22H14CoO4), respectively, and demonstrated that upon application of a high-voltage electric field, charged particles in a waxy oil may move and thus collide with wax particles, and consequently adhere to the wax particle surface. The particle collision results in damage to the wax particle network, and the electrostatic repulsion arising from the adhesion of the charged particle on the wax particle diminishes attraction between wax particles. This study clarifies the process of interfacial polarization.

The mechanism of viscosity reduction of waxy oils induced by the electric field: A correlation between the viscosity reduction and the charged particle accumulation on wax particles

Wax molecules crystallize at ambient temperature, causing the crude oil to become a dispersed system, which poses challenges in the flow assurance of pipelines. Improving the cold flowability of crude oil is the fundamental solution to tackle these problems. Applying an electric field to waxy oil may markedly improve its cold flowability. The adhesion of charged particles on wax particles’ surface under the electric field has been demonstrated as the essential mechanism of the electrorheological effect. However, the correlation between the accumulated charged particles and the induced viscosity reduction has not been explored quantitatively. In this study, the viscosity and impedance of four crude oils before and after electric treatment were measured. The conductivity changes of the oils’ continuous phase were obtained by an equivalent circuit model. And then, the charged particles’ concentration before and after electric treatment was calculated by the Stokes equation. The results showed there is a positive correlation between viscosity reduction and charged particle concentration reduction in the continuous phase. Importantly, this correlation is also quantitatively applicable to the results of ten different waxy oils which has been published. This study provides a quantitative basis for the mechanism of electrorheological behavior of waxy oils.

The preparation and smart electrorheological behavior of MOF-Ti@PANI core-shell nanoparticles

In this paper, a kind of core–shell composite nanoparticles for electrorheological (ER) fluid was successfully prepared and showed good ER effect. The material possesses the high specific surface area and low density of metal organic frameworks (MOFs), and combines with the excellent dielectric properties of polyaniline (PANI). PANI precursors were prepared by a rapid mixing method, and then MOF-Ti (an MOF containing Ti) grew in situ on PANI under the solvothermal conditions. The MOF-Ti@PANI composite nanoparticles with core–shell structure were generated. These characteristics of PANI and MOF-Ti are conducive to stronger interfacial polarization of nanoparticles, which in turn leads to a good ER effect. The nanoparticle morphology as well as its ER and dielectric properties was modulated by using different amounts of PANI addition. The addition amount of PANI had a certain effect on the particle morphology, which was proved by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). We also determined particle size at the nanoscale in this process. The measured results of the X-ray powder diffractometer (XRD) are consistent with the characteristic peaks of MIL-125 (a kind of MOF-Ti). The internal chemical structure of the material and the chemical environment of the elements were analyzed using Fourier infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Finally, the ER and dielectric properties of the nanoparticles in ER Fluids were investigated using high-speed rotational rheometry and broadband dielectric spectroscopy. The analysis revealed that the MOF-Ti@PANI core–shell nanoparticles have good ER properties under proper coating. For the core–shell modified MOFs, it is expected to be a promising development direction in the field of ER materials.

Zinc ferrite/polyaniline composite particles: Pigment applicable as electro-active paint

Hybrid conductive paint pigments composed of zinc ferrites (ZF) and polyaniline (PANI) were analysed as both a potential electro-active and corrosion-protective paint from the electrorheological (ER) point of view. The particles were characterised using scanning electron microscopy and X-ray diffraction spectroscopy. These hybrid conductive particles are used as pigments suitable for applications in paints which was confirmed by determining the consumption of linseed oil, the specific conductivity of aqueous extracts and the density of the tested pigments according to the relevant standardized methods. The chemical stability of particles was evaluated by means of durability tests in aggressive environment showing excellent results for the coated particles. Both ZF/PANI particles and pure ZF were dispersed in silicone oil and their ER behaviour was analysed through controlled shear rate and dynamic oscillatory tests. The ER performance of the pure ZF and the composite ZF/PANI suspensions were compared, showing promising results and enhanced ER performance and attention-worthy ER efficiency of the later (in particular, the ER efficiency of the coated particles exceeded 105% at 0.01 s−1). Lastly, the results were further validated via dielectric spectroscopy. Thus, the ZF/PANI particles have the potential to be applied as a hybrid ER fluid and an electro-active paint.

The size effect of faceted detonation nanodiamond particles on electrorheological behavior of suspensions in mineral oil

Suspensions of hydrogenated detonation nanodiamond (DND) particles in mineral oil are electrorheological fluids: their viscosity and yield stress increase under an electric field. The effect of the initial DND particles size obtained during the explosion on the properties of low-filled (up to 4 wt%) electrorheological fluids was considered. The small-angle X-ray scattering method revealed the differences in the structural organization of DNDs with sizes of 3 and 5 nm in a mineral oil, which affects the sedimentation stability of suspensions and their electrorheological behavior. The sedimentation ratio and the values of the yield stress are lower for 3 nm particles suspensions in the whole studied electric field strength (0–6 kV/mm). The method of impedance dielectric spectroscopy showed the differences in the electrophysical characteristics of suspensions filled with particles of 3 and 5 nm. The activation energies of polarization processes were estimated from the temperature dependences of the dielectric loss modulus. The study shows the key role of filler size for creating high performance electrosensitive materials and hypothesizes the reasons for different properties of electrorheological fluids filled by 3 and 5 nm DND particles.

Effect of Temperature on the Electrorheological Behavior of Porous Chitosan Particles in Polydimethylsiloxane

Effect of Temperature on the Electrorheological Behavior of Porous Chitosan Particles in Polydimethylsiloxane

Low-filled suspensions of α-chitin nanorods for electrorheological applications

Highly anisometric α-chitin nanoparticles isolated by TEMPO-oxidation were investigated as filler for electrorheological fluids. The dimensions of rod-like particles were determined by AFM and cryo-TEM methods. The rheological behavior of α-chitin nanoparticles in polydimethylsiloxane changes from viscous to elastic under electric field. The yield stress reaches about 220 Pa at 7 kV/mm for 1.0 wt% fluid. Despite the nanosize of particles, the suspensions sedimentation ratio was found to be low (~23%). The electrorheological behavior of the fluids was discussed in terms of the Mason numbers. The stability of fluids response under switching electric field was shown. The activation energy of polarization processes in suspensions was calculated as 58 ± 2 and 64 ± 1 kJ/mol for 0.5 and 1.0 wt% filler content from the impedance spectra. The high aspect ratio (~70) and dielectric permittivity result in high electrorheological activity of α-chitin suspensions at extremely low concentrations (≤1.0 wt%).

The electrorheological response behavior of small coral-like H2Ti2O5@SiO2 core-shell nanoparticles

BackgroundElectrorheological (ER) fluid is an important smart material that can respond to external electric field. The purpose of this work is to synthesize stronger ER nanomaterial. MethodIn this work, small coral-like H2Ti2O5 particles were prepared by hydrothermal method, SiO2 was uniformly grown on H2Ti2O5 through controlled hydrolysis, and H2Ti2O5@SiO2 core-shell nanocomposite was synthesized and used as ER material. The morphological evolution, structure and chemical composition of materials were studied by Scanning electron microscope (SEM), Transmission electron microscope (TEM), X-ray powder diffractometer (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). At the same time, dielectric and ER measurement results confirm that H2Ti2O5@SiO2 core-shell-based ER fluid has higher polarization strength and proper dielectric relaxation, which improves interface polarization and ER characteristics. ResultsThe ER results show that the ER efficiency after SiO2 coating is significantly improved, especially under higher applied electric field strength: when the voltage is 3 kV and the shear rate is 0.1 s−1, the ER efficiency can reach 160.84. Dielectric spectroscopy results show that H2Ti2O5@SiO2 fluid has a fast response time and a large difference in dielectric constant. It is a promising ER fluid material.

Monodisperse semiconducting poly(N-methylaniline) microspheres and their electrorheological response

Monodisperse semiconducting poly(N-methylaniline) (PNMA) microspheres with a suitable electrical conductivity were fabricated using a chemical oxidation process and employed in an electrorheological (ER) suspension. Morphological image of the synthesized PNMA microsphere was assessed via scanning electron microscope and transmission electron microscope. Its chemical composition and thermal behavior were determined using Fourier-transform infrared and thermal gravimetric analysis, respectively. Chain-like structure formation under an input electric field in ER fluid containing silicone oil and 10 wt% PNMA microspheres was observed directly with optical microscopy. Viscoelastic characteristics of the ER fluid under an input electric field were evaluated with a rotational rheometer. Yield stress with a power exponent of 1.5 was observed, along with typical solid-like property under electric field. Dielectric behavior of the ER suspension measured was also found to be closely associated with its ER behavior.

The influence of synthesis conditions on the electrorheological performance of iron(II) oxalate rod-like particles

This study investigates the influence of synthesis conditions of iron(II) oxalate particles on the particle morphology for their utilization in smart materials known as electrorheological (ER) fluids. Particle morphology has a significant impact on the ER behavior of the particles enabling their use in many unique practical applications. In this study, fifteen various iron(II) oxalate particles differing in synthesis conditions were prepared, out of which four variations were selected for an in depth investigation due to their promising morphology. The influence of synthesis conditions on the morphology of the resulted particles was evaluated by scanning electron microscopy analysis. An X-ray diffraction analysis was employed to confirm the dominant FeC2O4 · H2O phase presented in the synthesized particles. The ER suspensions consisted of the selected four iron(II) oxalate particles dispersed in silicone oil. An optical microscope and a rheometer, both operating under external electric field, enabled a precise and accurate investigation of the structure, the ER performance. Visual observation was used to evaluate the sedimentation stability of the suspension.