共查询到19条相似文献,搜索用时 140 毫秒
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研究了纳米二氧化钛包覆高岭土和钇掺杂钛酸钡两种电流变液的微波反射行为.实验发现,在垂直于微波传播方向电场作用下,两种电流变液微波反射系数均随电场强度的增大而增大;钇掺杂钛酸钡电流变液微波反射系数变化幅度比二氧化钛包覆高岭土电流变液宽,并且电场调节的能力随浓度的增加有减弱的趋势.对钇掺杂钛酸钡电流变液存在一个临界浓度,低于这个浓度,电场的调控能力随电场强度的增加而增大,高于这个浓度,电场的调控能力随电场的增加先增大后减小.另外,二氧化钛包覆高岭土电流变液反射回波相位随电场强度的增大出现最大值后逐渐减小趋于平
关键词:
电流变液
微波反射
相位 相似文献
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一、电-流变效应简介早在40年代,美国物理学家Wills.Winslow发现,把某些材料粉末分散在矿物油中制成悬浮液,当施加电场时,其表观粘度及剪切应力随电场的变化而变化。由于在电场作用下该流体呈现非牛顿流体的特点,故称电-流变效应(ER)。电-流变效应的意义在于,可以把这种流体做为一种传动介质,应用于离合器、减 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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Basic considerations in flowing electrorheological fluids 总被引:1,自引:0,他引:1
James E. Stangroom 《Journal of statistical physics》1991,64(5-6):1059-1072
The physical and chemical properties of electrorheological (ER) fluids are reviewed, and an outline theory of their mode of action is proposed. Rheologically, the Bingham plastic model gives an acceptable representation of ER fluids flowing in a field and it has recently been shown that the plastic viscosity may be field-dependent in some circumstances, as well as the yield stress. The variation of the former with field is strongly influenced by the specific chemical nature of the ER fluid, while the field dependence of the latter has a similar form in all the ER fluids investigated. However, interpretation of observations is complicated by concentration of solid in the working gap and interplay between local electrical conductivity and shear rate. 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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The yield stress of our newly developed electrorheological (ER)
fluids consisting of dielectric nano-particles suspended in silicone oil
reaches hundreds of kPa, which is orders of magnitude higher than that of
conventional ones. We found that the polar molecules adsorbed on the
particles play a decisive role in such new ER fluids. To explain this polar
molecule dominated ER (PM-ER) effect a model is proposed based on the
interaction of polar molecule-charge between the particles, where the local
electric field is significantly enhanced and results in the polar molecules
aligning in the direction of the electric field. The model can well explain
the giant ER effect and a near-linear dependence of the yield stress on the
electric field. The main effective factors for achieving high-performance
PM-ER fluids are discussed. The PM-ER fluids with the yield stress higher
than one MPa can be expected. 相似文献
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物理化学性能稳定的二甲基硅油常作为电流变液分散相, 当与纳米量级的介电颗粒混合组成电流变悬浮液时, 在非密闭环境下极易挥发, 时间足够长时, 可完全挥发. 本文通过实验研究了纳米二氧化钛颗粒对二氧化钛和硅油组成的悬浮液中硅油挥发增强现象, 分析表明, 纳米颗粒在电流变悬浮液的硅油气-液界面上形成纳米尺度的凸型曲面, 使液面上蒸气压大大提高, 导致挥发增强. 本文还对颗粒浓度, 环境温度和硅油黏度等对硅油挥发增强效应的影响进行了系统的研究和分析. 相似文献
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Shear tests of an electrorheological fluid with pre-applied electric field and compression along the fleld direction are carried out. The results show that pre-compressions can increase the shear yield stress up to ten times. Under the same external electric field strength, a higher compressive strain corresponds to a larger shear yield stress enhancement but with slight current density decrease, which shows that the particle interaction potentials are not increased by compressions but the compression-induced chain aggregation dominates the shear yield stress improvement. This pre-compression technique might be useful for developing high performance flexible ER or magnetorheological couplings. 相似文献
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Electrorheological (ER) fluids are a class of materials whose rheological properties are controllable by the application of an electric field. A dielectric electrorheological (DER) fluid is the simplest type of ER fluid, in which the material components follow a linear electrostatic response. We review and discuss the progress of the studies on physics of this type of material. A first-principles theory of DER fluids, along with relevant experimental verifications, are presented in some detail. In particular, the properties presented include static equilibrium structure, shear modulus, static yield stress and its variation with applied electric field frequency, and structure-induced dielectric nonlinearity. 相似文献
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Based on conduction model and cubic particle model, the relationship between current density and shear yield stress of electrorheological (ER) fluids was calculated and compared with some reported experimental results. The conductivity of the insulating oils is found to have been changed by the mixed particles. Several ways to decrease insulating liquid conductivity and increase the conductivity ratio of ER fluids have been proposed to prepare ER fluids with high shear yield stresses but low current densities. 相似文献
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Based on conduction model and cubic particle model, the relationship between current density and shear yield stress of electrorheological (ER) fluids was calculated and compared with some reported experimental results. The conductivity of the insulating oils is found to have been changed by the mixed particles. Several ways to decrease insulating liquid conductivity and increase the conductivity ratio of ER fluids have been proposed to prepare ER fluids with high shear yield stresses but low current densities. 相似文献