Summary: Electrorheological properties in steady shear of perchloric acid doped poly(3‐thiopheneacetic acid), PTAA, particles in silicone oil were investigated to determine the effects of field strength, particle concentration, doping degree (conductivity values), operating temperature and nonionic surfactant. The PTAA/silicone oil suspensions show the typical ER response of Bingham flow behavior upon the application of electric field. The yield stress increases with electric field strength, E, and particle volume fraction, ?, according to a scaling law of the form, τy ∝ Eα · ?γ. The scaling exponent α approaches the value of 2, predicted by the polarization model, as the particle volume fraction decreases and when the doping level of the particles decreases. The scaling exponent γ tends to unity, as predicted by the polarization model, when the electric field strength is low. The yield stress under electric field initially increases with temperature up to 25 °C, and then levels off. At electric fields above of 1.5 kV/mm, the yield stress increases significantly by up to 50% on addition of small amounts of a nonionic surfactant.
Effect of switching the applied electric field on the viscosity of a 20 wt.‐% highly HClO4 doped polythiophene suspensions during stress sweep test. 相似文献
Dodecylbenzene-sulfonic acid (DBSA)-doped polyaniline (PANI) was prepared by emulsion polymerization, where DBSA was used as both an emulsifier and a dopant. The chemical structure and morphology of the DBSA were examined via FT-IR and SEM, respectively. Electrorheological (ER) properties of DBSA-doped PANI particles dispersed in silicone oil were studied under different operating temperatures and an applied electric field. Shear stress data as a function of shear rate fitted quite well with the Cho-Choi-Jhon (CCJ) shear stress model. Both deduced static and dynamic yield stresses were found to be collapsed into a universal scaling function. Furthermore, the Cole-Cole plot and the dielectric spectra gave relaxation times of the ER systems for different operating temperatures of dielectric measurements, confirming the correlation of dielectric properties with ER performance. 相似文献
Two-dimensional dielectric sheets composed of graphene-supported amorphous carbon were prepared by annealing polyaniline-coated graphene oxide sheets in vacuum. The morphology and structure were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and Fourier-transform infrared spectroscopy. This showed that annealing the polyaniline-coated graphene oxide had little influence on its plate-like morphology but transformed the graphene oxide core into conducting graphene and the polyaniline shell into insulating nitrogen-enriched amorphous carbon. An electrorheological suspension was prepared by dispersing the graphene-supported carbonaceous sheets in silicone oil and its electrorheological property was investigated by rhelogical tests under electric fields. The suspension demonstrated a strong electrorheological effect. Its yield stress and shear stress were about three times as large as those of a suspension of pure carbonaceous particles at equal electric field strengths. The storage modulus of the suspension was also higher than that of a suspension of pure carbonaceous particles, indicating stronger electrorheological activity. Dielectric measurements indicated that the presence of the graphene core had increased the polarization property, and this is responsible for the increased electrorheological activity. 相似文献
Bipolar electrochemistry is a conventional method based on the polarization of an isolated substrate under an applied electric field. This technique has been applied to electrolysis, corrosion, and other areas of chemical engineering since the twentieth century. However, it has been recognized as a powerful tool in many modern domains after water splitting has been demonstrated to be possible using micrometer-sized bipolar electrodes. Modifying inorganic objects in novel ways, such as creating electrical contacts between metal particles using directed electrochemical growth or shaping and exploring the micro- and nanoworld are some of the new applications in this field. Fabrication of electronic devices, electroanalytical purposes, generation of molecular and material gradients, functionalization of single micro- and nanopores, synthesis of Janus particles, design of swimmers, and asymmetric modification of nanoparticles will be discussed in this article as a focal point of future research in bipolar electrochemistry. 相似文献
A new rheological model is applied to the analysis of the behavior of electrorheological (ER) fluids. A comparison of the model’s predictions with experimental data shows that the proposed model correctly predicts the shear stress behavior both quantitatively and qualitatively. The shear stress data for the aligned particles’ structure reformation can be fitted as a function of shear rate with the new model. Proposed model using less parameters than CCJ model affords good agreement with the experimental data and consistent parameter values through the whole shear rate range and different applied electric field strengths. Furthermore, the yield stress was found to be almost linearly dependent on the field strength, different from the predictions of the polarization model. 相似文献
Semiconducting graphene oxide/polyaniline (GO/PANI) composite particles for potential electrorheological (ER) fluid applications were synthesized by the in situ dispersion polymerization of aniline in the presence of GO particles, which were prepared using a modified Hummers method. The electroresponsive ER characteristics of the composite when dispersed in silicone oil exhibited a phase transition from a liquid-like to solid-like state under an applied electric field. The morphology and composition of the composite particles were characterized by scanning and transmission electron microscopy and Raman spectroscopy. Its fibrillation phenomenon was observed by optical microscopy during the application of an external electric field. The bulk rheological characteristics of both the flow curve and yield stress were examined using a rotational rheometer equipped with a high voltage generator. The GO/PANI composite showed typical ER behavior, which demonstrated its potential applications as an ER smart material. 相似文献
In order to improve the stability of magnetorheological (MR) fluids, viscoelastic medium having 2.2 Pa yield stress has been
used as a continuous phase and nanosized CrO2 particles are added too. The rheological properties as well as the dispersion stability of MR fluids have been studied by
using a stress-controlled rheometer and sedimentation test. The steady-shear MR response was independent of the continuous
and nano additives and the fieldinduced yield stress increased subquadratically with the flux density. Since the constant
stress is generated within the limit of zero shear rate, the plateau in the flow curve corresponds to the Bingham yield stress.
Under an external field, the yield stress varied as B3/2. The yield stress has an approximately linear relation with the particle volume fraction. 相似文献
Electrorheological (ER) properties of polyaniline suspensions in silicone oil with various experimental conditions were investigated. These suspensions exhibit dramatic changes in their rheological properties which are caused by the formation of particle chain structures induced by an applied electric field. Polyaniline was synthesized by the chemical oxidation of aniline with ammonium peroxysulfate. This study examined the effects of electric field, volume fraction, polymerization temperature and operation temperature on the ER properties of polyaniline suspensions in silicone oil. Rheological measurements were carried out by using a rotational rheometer with a high voltage generator in both controlled shear stress and shear rate modes. Experimental results showed that the ER properties were enhanced by increasing the volume fraction and electric field and were independent of the operating tempertures. The best ER properties were also obtained by using polyaniline particles synthesized at -10°C, and these had a conductivity of ? 10?10 S/cm. 相似文献
Within the general category of so called generalized Newtonian fluids, there exists a class of materials which do not deform until the applied shear stress exceeds a critical value called yield stress. Conversely, such a material behaves like a solid as long as the shear stress is less than the yield stress. This class of materials is called viscoplastic fluids. The question whether the true yield stress exists or not is indeed far from settled (1), but the notion of a yield stress has proved to be quite useful in practice in describing the steady shear rheological behaviour of a range of materials especially of particulate suspensions. Consequently, yield stress appears as a parameter in all constitutive relations (which purport to describe the steady shear behaviour of viscoplastic materials), and its evaluation is important before an engineering flow problem can be solved. Conversely, there are some simple hydrodynamic situations which allow the value of the yield stress to be extracted from macroscopic quantities such as flow rate-pressure drop data. In this paper, we examine this possibility using gravity driven flow of a viscoplastic material on an inclined plane. 相似文献
Bi-disperse Electrorheological (ER) suspensions of two polarizable particles of the same size are investigated to understand
the ER behavior of poly-disperse suspensions composed of various polarizable particles. The electrostatic polarization model
is employed to describe ER suspensions, and solutions to the equation of motion are obtained by dynamic simulation. Even with
the applied electric field, metastable structures and sheared configurations at a shear rate of 0.01 and 10 s-1 show no inhomogeneous higher polarizable particle distributions (no higher polarizable particle cluster formation) regardless
of the ratio of the two types of particles. The shear stress increases with the increase of the higher polarizable particle
concentration both in the electrostatic force and hydrodynamic force dominant regions. 相似文献
In order to reduce the maximum peel and shear stress concentrations in the adhesive layer, a smart adhesively bonded scarf joint system was developed by surface bonding of piezoelectric patches onto a typical scarf joint. The forces and bending moments at the edges of the developed smart joint system can be adaptively controlled by adjusting the applied electric field on the piezoelectric patches, thus reducing the peel and shear stresses concentration in the adhesive layer. In order to verify the effect of surface bonding of piezoelectric patches in smart scarf adhesive joints, an analytical model was developed to evaluate the shear stress distribution and to predict the peel stress. It was established that the piezoelectric patched joint could reduce the stress concentrations at the scarf joint edges. The influence of the electric field and the effects of the scarf angle and the adherend Young's modulus on the peel and shear stresses were investigated. It was found that the effect of scarf angle is more significant at higher angles to raise the stresses. The effect of the electric field on the shear stress is more significant than on the peel stress. 相似文献