Study on Electric Properties of Particle/Fluid Suspension

悬浮在流体中的颗粒材料在外加电场和磁场的作用下有望改变流体的性质和结构。这种流体材料的几种性质已经在实验上和理论上进行了研究，电流变（ER）效应通常在颗粒/绝缘油分散体中观察到，其剪切应力可以随着施加的外部电场而急剧增加。过去，人们提出了许多机制来解释这种行为。基于电场作用下颗粒聚集结构的考虑，对其机理的认识不足，使得电流变液材料设计的基础难以建立。该项目采用悬浮在电绝缘硅油中的二氧化硅颗粒或铁电钛酸钡颗粒的ER流体。在交变电场的作用下，对样品的介电、电导率和产生的剪切应力进行了原位测量。所产生的剪切应力被发现密切依赖于悬浮液的介电常数。这一发现导致了一个新的相关方程的推导所产生的剪切应力，所产生的介电常数和外部电场强度。经验证，该方程可适用于各种各样的实验条件。

Materials of particles suspended in fluid are expected to change fluid properties and structures with an application of external electric and magnetic fields. Several properties of such fluid materials have been investigated experimentally and theoretically Electrorheological (ER) effects are typically observed in particle/insulating oil dispersions, whose shear stress can drastically increase with the external electric field applied. In the past, a number of mechanisms were proposed to explain such behavior. On the basis of the consideration of particle aggregation structures under the electric field, poor understanding of the mechanism makes it difficult to establish the grounding of material design of ER fluids. This project employed an ER fluid of silica particles or ferroelectric barium titanate particles suspended in electrically insulating silicone oil. In-situ measurements of dielectricity, electroconductivity and generated shear stress were performed under an application of alternative electric field. The generated shear stress was found to closely depend on the dielectric constant of the suspension. This finding has led to the derivation of a new correlation equation for the generated shear stress, the generated permittivity and the external electric field strength. It is verified that the equation can be applied for a wide variety of experimental conditions.