硫酸改性TiO2粒子的表征与电流变性能研究

采用硫酸溶液浸渍TiO₂干凝胶的方法制备了硫酸改性的TiO₂粒子, 并组成了具有显著电流变性能的电流变材料. 用FT-IR、XRD、比表面积分析仪等表征了样品结构, 并测试了其电流变性能. 结果表明：由于硫酸根对晶粒生长的阻碍作用, 与纯TiO₂粒子相比, 硫酸改性的TiO₂粒子的晶粒尺寸降低, 比表面积提高, 并含有大量的强极性键SO. 当电场强度为3kV/mm时, 纯TiO₂粒子电流变液的场致剪切应力与零场剪切应力之比（τ_E/τ₀）仅为80, 而硫酸改性TiO₂电流变液的τ_E/τ₀高达500. 产生这些现象可归因于硫酸改性TiO₂粒子带来的结构改变赋予其明显的界面极化能力.     

添加剂对铁/聚丙烯酸锂复合微粒-硅油电流变和磁流变效应的影响

采用反相乳液聚合技术合成了铁/聚丙烯酸锂复合微粒, 将其悬浮分散于含有不同添加剂的硅油中形成电磁流变体, 考察了添加剂的种类和用量对复合微粒的电流变和磁流变效应的影响。结果表明, 添加剂对电流变效应有较大影响, 且不同添加剂对电流变效应的影响差别较大, 对磁流变效应的影响却较小。     

复合颗粒电流变液的制备及其性能

制备了ＳｉＯ２／Ｐ（ＭＭＡ－ＭＡＡ）微囊复合颗粒电流变液,测试了该电流变液的力学性能和材料性能。结果指出：这种复合颗粒电流变液的稳定性有较大的提高;剪切强度随外加电场强度的增大而增大。     

聚邻苯二胺/蒙脱土纳米复合材料的合成及其电流变效应

用乳液共混插层法制备了聚邻苯二胺/蒙脱土纳米复合材料微粒,通过IR、XRD及TEM对其结构进行了表征。 结果发现,邻苯二胺插入蒙脱土层间聚合后,导致蒙脱土片层之间的剥离,形成纳米复合材料。 将其分散在甲基硅油中(体积分数,22%)配制成无水电流变液,该复合材料表现出较大的协同效应,具有较好的电流变行为。实验结果表明在外加电场下,其电流变效应比聚邻苯二胺、蒙脱土均有显著提高。 在3 kV/mm(DC, 74.5 s-1)时,剪切强度达8.27 kPa;同时抗沉降性极好,静置60 d沉淀率小于3%。介电性能测试表明,聚邻苯二胺/蒙脱土纳米颗粒的介电常数和介电损耗较蒙脱土和聚邻苯二胺均有一定提高,电导率也达到了最佳范围。     

Direct numerical simulation of two-dimensional channel flows of electro-rheological fluids

Direct numerical simulation (DNS) of electro-rheological (ER) fluid flows in two-dimensional (2D) electrode channel has been performed by adopting a combined finite element method (FEM). Hydrodynamic interactions between the particles and the fluid are described by the Navier-Stokes equations for the fluid in combination with the equations of motion for the particles, while the multi-body electrostatic interaction is represented by the point-dipole model.ER effects on the plane channel flow for a given pressure gradient have been studied by varying the Mason number and volume fraction of the particles, and interrogating the motion of the particles in views of the formation of ER chain structures, the fluid velocity profile in the channel, and the shear stress versus the shear rate. As the Mason number decreases and volume fraction increases, the tendency that particles align to form chain structures becomes stronger. The yield stress of the ER fluid increases with the electric field intensity and the particle concentration. The quadratic correlation between the yield stress and the electric field intensity has been extracted from the present direct numerical simulation. Lastly, it has been shown that the yield stress linearly increases with the volume fraction in the intermediate range.     

丙三醇/羧甲基淀粉/改性氧化钛复合颗粒的电流变性能

结合改进的水解法和溶胶-凝胶法,制备了丙三醇/羧甲基淀粉/改性纳米氧化钛复合颗粒,分析表明羧甲基淀粉和纳米氧化钛之间存在有相互作用;同时,介电测试表明此颗粒配制的电流变液的介电极化特性有很大改善.经流变学测试,此复合颗粒电流变液的动态剪切应力在颗粒质量分数为25%,剪切速率为100s-1,3kV/mm DC下为960Pa,剪切增幅比为35.同时,此电流变液的静态屈服应力在更高浓度,5kV/mm DC下可达到18kPa,比同等条件下改性氧化钛和CMS电流变液的静态屈服应力均有所提高.此外,这种电流变液还表现出较好的抗沉降性能.     

电流变体智能材料在交变电场下的透光性能研究

电流变体作为智能材料作动器的一种,在外加电场的作用下,其材料性能会发生显著的变化。本文主要研究了二氧化硅／淀粉复合颗粒电流变体在交变电场作用下的透光性能的变化。对不同浓度的流体、不同外加电场强度,不同外加电场频率以及不同电极间距几种情况下电流以变体的透光性均进行了测试。     

Fabrication of ammonium persulfate coated silica microsphere via chemical grafting and its electrorheology

Silica/ammonium persulfate (APS) microspheres were fabricated by coating APS on the surface of ~2 μm sized silica particles and applied as a candidate for electrorheological (ER) materials. The morphologies of these particles were observed by SEM. Chemical compositions and structure of the particles were confirmed by EDS and FT-IR. Thermogravimetric analysis was used to examine the amount of APS coating on the silica particles. A 10 vol% ER fluid based on the fabricated particles was prepared by dispersing them into hydroxyl group-terminated silicone oil. Typical ER properties were obtained using a rotational rheometer under an applied electric field at a controlled shear rate test. These properties were also correlated with its dielectric spectra.     

智能复合材料结构的主动振动控制

本文提出应用电流变体(Electro-Rheological Fluids)材料作为复合材料结构振动主动控制的材料,针对含电流变体材料的智能复合材料悬臂梁,进行了振动的主动控制,测试了智能复合材料悬臂梁在外加电场作用下,弹性模量、衰减系数、固有频率等振动特性的变化,同时,针对不同的梁材料,给出了材料变化对梁振动控制的影响.     

Electroactive response of mesoporous silica and its nanocomposites with conducting polymers

Electroactive response of suspensions of mesoporous silica and its nanocomposites with conducting polyaniline and copolyaniline inside its channels were examined under an electric field, mainly focusing on their rheological characteristics. Initially these conducting polymer/mesoporous silica nanocomposites were synthesized and their physical properties were studied by scanning electron microscopy, transmission electron microscopy and N₂-adsorption isotherm. Then, mesoporous silica and its nanocomposites were dispersed in silicone oil as an electrorheological (ER) material. Typical ER behaviors of shear stress and shear viscosity curves as a function of electric field and shear rate were observed. Without an electric field, the suspensions behaved almost like a Newtonian fluid. However, under an electric field, their shear stresses increased with shear rate, demonstrating a yield stress. Compared with mesoporous silica and polyaniline, polyaniline/mesoporous silica-based ER fluid showed enhanced ER performance due to the anisotropic characteristics. In addition, it was found that a suggested shear stress model (Cho–Choi–Jhon model) well described the flow curves.     

新型聚合物电流变材料的合成及性能

以间苯二胺,2,5-二氧环己二甲酸二甲酯为原料,经缩合、闭环、氧化等反应,制得了聚喹吖(2,3b)啶-12,14(5,7)二酮(PQA)并进行了表征;并以PQA为基础粒子制备了无水型电流变流体(ERF),研究了其电流变性能。考察了溴代二苯甲烷(BDPM)-PQA体系中粒子浓度、电场强度、剪切速率等对电流变流体性能的影响,并从聚合物粒子的分子结构特点出发,对该体系的电流变效应进行了解释;对比了不同分散介质(BDPM及硅油)对电流变效应的影响。结果表明,PQA在BDPM中具有较佳的电流变效应,当粒子的质量分数为30%,外加电场为3 kV/mm时,屈服应力达4.0 kPa。     

Electric field induced stress moduli of polythiophene/polyisoprene suspensions: Effects of particle conductivity and concentration

Electrorheological properties of polythiophene/polyisoprene suspensions were investigated in the oscillatory shear mode under electric field varying from 0 to 2 kV/mm. Poly(3‐thiophene acetic acid) particles were synthesized via an oxidative polymerization and doped with perchloric acid in order to vary electrical conductivity. ER responses can be enhanced with increasing electric field strength, particle electrical conductivity, and particle concentration. The storage modulus (G′) increases dramatically by 3 and 4 orders of magnitude, with the variations of particle conductivity and particle concentration as the electric field strength is increased from 0 to 2 kV/mm The results can be interpreted in terms of the difference in the polarizability between the particles and the matrix, and the particle agglomeration existing at high particle electrical conductivity and high particle concentration. The suspensions exhibit the transitions from the fluid‐like behavior to the solid‐like behavior at the critical electric field strengths. In particular, the sol‐to‐gel transitions occur at lower electrical field strengths with higher particle electrical conductivity and at higher particle concentration.     

Strain-hardening in the oscillatory shear deformation of a dedoped polyaniline electrorheological fluid

An electrorheological (ER) fluid, consisting of polydisperse dedoped polyaniline (PANI) particles, having irregular shapes, dispersed in silicone oil, was subjected to cyclic strain annealing treatments using oscillatory shear, under an external electric field. After each annealing period, the sample was subjected to a controlled-strain sweep, to determine the yield stress, and to erase the ER structure. During each annealing cycle, the storage modulus and the yield stress were observed to increase, and the loss modulus to decrease, each eventually approaching an asymptotic constant value. These observations in oscillatory shear complement our previous observations of a strain-hardening effect in a PANI/silicone oil ER fluid subjected to unidirectional creep tests.     

Electrorheological properties of pumice/silicone oil suspension

Pumice particles-based electrorheological (ER) suspensions were prepared in silicone oil and its ER behavior was investigated as a function of shear rate, electric field strength, concentration and temperature. Sedimentation stabilities of suspensions were determined. ER activity of all the suspensions was observed to increase with increasing electric field strength, concentration and decreasing shear rate. Yield stress of pumice suspensions increased linearly with increasing applied electric field strength and with concentrations of the particles. The pumice suspensions show a typical shear thinning non-Newtonian viscoelastic behavior, in which viscosity of suspension decreased sharply with increasing shear rate. Effect of high temperature onto ER activity of pumice/silicone oil system was also investigated.     

乳状电流变基液及其对材料性能的影响

研究试制了乳状电流变基液，以二甲基硅油为基体，二甲基亚砜作添加剂，在超声波的作用下使二甲基亚砜分散于硅油中形成稳定的乳状液，测试了该乳液的介电常数，电导率及介电损耗。以此乳液作基液，与稀土改性TiO2和BaTiO3等固体颗粒配成电流变液，并对其流变性能进行测试。实验结果表明：用该乳液作基液配制的电流变液化用纯硅油作基液配制的电流变液介电性能有较大的改善，电流变性能显著提高。     

Control of radiation heat transfer through a composite window featuring ER fluid: A conceptual investigation

Radiation heat transfer control through the application of an electric field upon an Electroheological (ER) fluid based composite material is an innovative new area of research. A conceptual experiment has been conducted to study radiation heat transfer through a composite window featuring an ER fluid. The composite window is composed of two thin glass plates with a layer of ER fluid contained between them. The glass walls were transparent except for a very thin coating of an electric-conductive film which enabled the inside of the glass surfaces to serve as electrodes. The ER fluid was contained between the glass surfaces and consisted of a suspension of micron sized crystalline zeolite particles in a silicon oil. This study has demonstrated the unique capability of ER fluids to regulate and control radiation heat transfer via transmittance measurements. A semi-empirical model is developed from the experimental data to correlate the dependence of radiation transmission through ER fluids based on several physical parameters (f_v, V^*, and L). This model agrees reasonably well with the measured data. The results obtained in this study are very important to those concerned with the development of a thermally smart material for heat transfer control.Presented at the Second Minsk International Heat and Mass Transfer Forum, May 18–22, 1992.     

苯胺-SrTi(C2O4)2颗粒制备及其电流变性能

用沉淀法制备了苯胺-草酸氧钛锶（SrTi（C₂O₄）₂）颗粒。FTIR分析表明,苯胺已引入到SrTi（C₂O₄）₂颗粒的表面;XRD分析表明,苯胺-SrTi（C₂O₄）₂颗粒为含少量结晶的无定形态。采用SEM观察颗粒的形貌,结果表明,随反应体系中苯胺与钛原子物质的量比n_aniline/n_Ti的增大,苯胺-SrTi（C₂O₄）₂颗粒由近似球状（n_aniline/n_Ti =0）变为多面体状（n_aniline/n_Ti =2）,而后变为棒状与团簇状颗粒的混合体系（n_aniline/n_Ti =3）。以苯胺-SrTi（C₂O₄）₂颗粒为分散相制备颗粒质量分数为66.7%电流变液,电流变性能测试结果表明,在n_aniline/n_Ti =2时,电流变液具有较高的剪切应力和剪切屈服强度、较大的漏电流密度。苯胺在颗粒制备过程中起控制颗粒形貌的作用,在电流变液体系中起极性分子的作用,其对苯胺-SrTi（C₂O₄）₂电流变液性能的影响是两种效应综合作用的结果。     

Synthesis and electrorheological properties of polyaniline/silicon dioxide composites

This study was to synthesize the inherently conductive polymer polyaniline using an optimized process to prepare polyaniline/silicon dioxide (PANI/SiO₂) composites by in situ polymerization and ex situ solution mixing. PANI and PANI/SiO₂ composite films were prepared by drop-by-drop and spin-coating methods. The morphology of particles and films were examined by a scanning electron microscope (SEM). SEM measurements indicated that the SiO₂ were well-dispersed and isolated in composite films. The electrorheological (ER), characteristics of the PANI/SiO₂ composites were investigated. A volume fraction series (φ = 5–25 %) of the PANI/SiO₂/silicone oil dispersions were prepared and sedimentation stabilities were determined. An ER activity was observed from the samples, when subjected to external electric field strength thus, they were classified as smart materials. Some parameters affecting the ER properties of the dispersions such as volume fraction, shear rate, electric field strength, frequency, and temperature were investigated.     

Linear viscoelasticity of semiconducting polyaniline based electrorheological suspensions

A dry-base electrorheological (ER) fluid was prepared by dispersing synthesized semiconducting polyaniline (PANI) particles into silicone oil, and its viscoelastic properties were investigated under applied electric fields using a rotational rheometer. Within the linear viscoelastic region, the ER fluid was observed to be elastic, due to columnar structure of PANI particles sustaining the deformation. Its rheological functions (G and G) were interpreted based on the dimensional analysis, and they showed roughly linear electric-field dependence of the dimensional collapse of the viscoelastic behavior with frequency suggesting that the interactions between highly irregular particles are saturating even at these relatively low values of the dielectric mismatch. Furthermore, the recovery percentage obtained from the creep and recovery experiments increased with applied electric fields.     

Polar‐Molecule‐Dominated Electrorheological Fluids Featuring High Yield Stresses

Recent works on the development of various electrorheological (ER) fluids composed of TiO₂, Sr? Ti? O, and Ca? Ti? O particles coated with C? O/H? O polar groups are summarized, in which an extremely large yield stress up to 200 kPa is measured and the dynamical yield stress reaches 117 kPa at a shear rate of 775 s^?1. Moreover, unlike that of traditional dielectric ER fluids, the yield stress displays a linear dependence on electric field strength. Experimental results reveal that it is the polar molecules adsorbed onto the dielectric particles that play the decisive role: the polar‐molecule‐dominated ER effect arises from the alignment of polar molecules by the enhanced local electric field in the gap between neighboring particles. The pretreatment of electrodes and the contrivance of new measuring procedures, which are desirable for the characterization and practical implementation of this material, are also discussed. The successful synthesis of these fluids has made many of the long since conceived applications of the ER effect available.