共查询到19条相似文献,搜索用时 171 毫秒
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瞬变的反应时间是电流变液体的一个重要参数.本文通过实验和理论分析,建立了考虑分散相颗粒几何因素的电流变反应时间模型根据此模型,长椭球状颗粒的电流变液体反应时间比等效球状颗粒的短,扁椭球状和片状颗粒的电流变液体反应时间比等效球状颗粒的长,而棒状颗粒的电流变液体反应时间则视εp/εf比值大小或快于或慢于等效球状颗粒的反应时间.且反应时间与分散相尺寸的关系是(1)随体积增大,各种形状颗粒的电流变液体反应时间均变短;(2)同体积下,随长径比增大,长椭球状颗粒的电流变液体反应时间变短,而扁椭球状颗粒和片状颗粒的电流变液体反应时间变长,棒状颗粒的电流变液体反应时间则视。εp/εf比值大小或增快或减慢.因此,要获得反应快的电流变液体,颗粒形状除选择球状外,还可在使雷诺数较小范围内,选择一定尺寸的长椭球状或棒状颗粒。
关键词: 相似文献
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极性分子型电流变液是一种新型的电流变材料.其介电颗粒上吸附极性分子,极性分子在颗粒间强局域电场作用下发生取向是产生巨电流变效应的关键.通过对Ca—Ti—O(CTO)体系极性分子型电流变液电流密度的测量发现,其导电行为遵从Poole-Frenkel效应的规律,这是极性分子型电流变液的重要特征之一.而500 ℃处理过的CTO粉体不含极性分子,所配制的电流变液无巨电流变效应,其电流密度随外电场强度近似地呈线性关系,显示出传统电流变液特性. 相似文献
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电流变液的研究进展及应用前景 总被引:3,自引:0,他引:3
电场致流变液体(电流变液)是一些高介电小颗粒和低介电油液的混合体,它在高电场作用下呈现液体与固体间的变换,变换时间为几毫秒,而且变换可逆。阐明了电流变液的原理,综述了电流变液在机制、材料及应用等方面的研究现状,并介绍了电流变液在技术和工业上广泛的应用前景。 相似文献
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极性分子型电流变液 总被引:2,自引:0,他引:2
电流变液在电场作用下软硬连续可调的奇特性质具有广泛和重要的应用价值。传统电流变液是基于颗粒极化产生的相互作用,根据介电理论预测,其剪切屈服强度的上限约为10kPa。电流变液被发明50年来,阻碍其应用的主要原因是剪切强度低。近年来发明的"极性分子型电流变液"是一类新型电流变液,其屈服强度比传统电流变液大一个数量级以上,且与电场强度呈线性关系,这一点和传统电流变液中的平方关系也明显不同。文章作者提出了极性分子在颗粒间强局域电场中的取向并与极化电荷作用的模型,成功地解释了观察到的实验现象。根据这一原理,有可能制备出屈服强度高达MPa的电流变液。 相似文献
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理论计算表明,介质包覆导体颗粒用作电流变液的分散相,可以获得高剪切应力的电流变液.采用溶胶-凝胶技术在尺度为5—10μm的石墨颗粒表面成功地包覆了TiO2,获得了金红石相TiO2包覆石墨的复合颗粒.配制成复合颗粒/硅油电流变液,其剪切应力与纯TiO2/硅油电流变液相比,可提高一个数量级.当电场强度为1.7kV/mm时,复合颗粒/硅油电流变液的剪切应力可达1.25kPa,电流密度小于10μA/cm2.
关键词:
电流变液
包覆
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石墨 相似文献
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Interaction, polarization, and charges or electric field distribution of conducting spheres in applied electric field are in many fields including electrorheological fluids, electrophoresis, and electrical engineering. A system with two equipotential conducting spheres in an applied uniform electric field is analyzed by image method. A new method is put forward to calculate the image charges distribution when using image method, which ensures the validity of image method to analyze equipotential cases. An apparatus is constructed to measure the force experimentally as well. Results show that the distribution of electric field and electric interaction are different with the case not equipotential. 相似文献
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The Rayleigh identity, based on a multipole expansion theory, is extended to analyse the forces between particles in an electrorheological system. The shear modulus for chains of particles arrayed on a square lattice is calculated. It is found that the modulus increases linearly with the ratio of dielectric constants of the dispersed particles to that of the continuous phase; as the ratio becomes larger, contrary to the expectations from a simple dipole approximation, the modulus would saturate. In the case of conducting particles, the modulus varies with the frequency of the applied field. In a limiting case of perfectly conducting particles, the conductivity is also considered. It is found that the particle-particle forces are extremely sensitive to their separations from each other. 相似文献
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L. N. Medgyesi-Mitschang C. Eftimiu 《Applied Physics A: Materials Science & Processing》1979,19(3):275-285
The electromagnetic scattering from axisymmetric conducting or nonconducting (dielectric) obstacles, embedded in an axisymmetric
dielectric body is treated. A surface integral equation formulation, consisting of coupled Fredholm equations of the first
kind for the electric and magnetic fields, is solved by the method of moments. The outer surfaces of the internal obstacles
and the embedding dielectrics can be nonconcentric, depart significantly from a spherical shape, but must be rotationally
symmetric about a common axis. The embedding dielectric can be multilayered. Computer implementable expressions are given
for the scattering cross sections for any desired polarization and for both backscatter (monostatic) and bistatic illumination.
Comparisons are made with the extended boundary condition method for homogeneous dielectric bodies and the Mie theory extended
for dielectrically clad conducting spheres. The generality of the present formulation is demonstrated for several other cladded
scatterer configurations.
This research was conducted under the McDonnell Douglas Independent Research and Development Program. 相似文献
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采用溶胶凝胶和表面接枝的方法, 合成了一种新型核壳结构的电流变液材料, 其组成为Li0:1(TixNi1-x)0:9O/聚苯乙烯(x=0.02,0.05).通过透射电镜、X射线衍射和红外光谱分析方法研究了该材料的形貌和结构, 并利用宽频阻抗测量仪、静态电流变测量仪研究了该材料的介电性质和电流变性能, 进而讨论了其结构与电流变性能之间的关系.研究发现,随着Ti含量增加,Li0:1(TixNi1-x)0:9O的介电常数减小,电流变效应减弱,且聚苯乙烯包裹后,介电常数进一步下降,但电流变效应有明显增强.结果表明,利用核、壳两部分各自具有的不同电学和力学性质组合制备得到的核壳结构电流变材料,可具有很高的介电常数,合适的介电损耗以及较小的漏电流密度,其电流变性能可得到明显的提高. 相似文献
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Ivlev AV Morfill GE Thomas HM Räth C Joyce G Huber P Kompaneets R Fortov VE Lipaev AM Molotkov VI Reiter T Turin M Vinogradov P 《Physical review letters》2008,100(9):095003
We report the experimental discovery of "electrorheological (ER) complex plasmas," where the control of the interparticle interaction by an externally applied electric field is due to distortion of the Debye spheres that surround microparticles (dust) in a plasma. We show that interactions in ER plasmas under weak ac fields are mathematically equivalent to those in conventional ER fluids. Microgravity experiments, as well as molecular dynamics simulations, show a phase transition from an isotropic to an anisotropic (string) plasma state as the electric field is increased. 相似文献
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Column size effects of DER fluids 总被引:1,自引:0,他引:1
The static yield stress of dielectric electrorheological (DER) fluids of infinite column state and chain state are calculated
from the first principle method. The results indicate that the column surface contributions to ER effects is very small and
both states will give correct results to the real DER fluids.
Received 29 January 2001 and Received in final form 30 April 2001 相似文献
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研究了金属板的上下表面附近各放置一层按周期排列的电介质小球的体系的光学性质.用多重散射法计算的结果显示金属上侧的周期性排列的电介质小球可诱发金属-电介质表面上的表面等离子激元.这些表面等离子激元的存在可通过非常尖锐的吸收峰反映出来.对于无限厚的金属板,这些吸收峰的峰值位置主要与电介质小球的周期有关,且与解析理论符合得相当好.在有限厚度的金属板中,金属板的两侧表面会产生对称和反对称的两种表面等离子激元,从而使原来在无限厚的金属表面上所出现的单一频率的表面等离子激元劈裂为双频率.由于对称和反对称的表面等离子激元模式在金属板的两侧表面均有相当强的电磁场,因而它们可导致强的电磁波穿透.通过在金属板的下侧加入玻璃球层可将表面等离子激元的电磁场引导出金属,并产生透射波.用多重散射法计算的结果证实,在此体系中由表面等离子激元所引起的透射可达到相当的强度. 对该体系中的物理机理进行了详细分析,从而能够通过调节该体系中的一些参数来控制表面等离子激元出现的频率,使强吸收峰或强透射峰出现在所希望的频率上.
关键词:
表面等离子激元
吸收谱
透射 相似文献