【作者】 吴孟强；

【导师】 陈艾；

【作者基本信息】 电子科技大学 ， 材料物理与化学， 2002， 博士

【摘要】 外加电场导致固液分散体系的结构与流变性质的变化称为电流变效应。电流变体是由粒径为微米或亚微米级的易极化粒子分散于低介电系数的液体绝缘介质中形成的复合悬浮体。电流变体在外加电场作用下能在毫秒级时间内发生明显的、可逆的流变响应，从而被认为是“有可能使诸多工业部门发生变革的一种智能材料”，它是材料科学和液态物理等领域的一大研究热点和学科前沿。本论文在研究双相复合悬浮液电流变效应机理，及场致微结构变化特征的基础上，首次对电流变体流变光学特性进行了较深入的理论分析，并对电流变体的光学调控特性进行测试，从而首次提出并设计了光学特性动态可调的电流变体灵巧窗（electrorheological fluids-based smart window，ERFSW）智能结构，为电流变体应用研究提出了一条新思路，开拓了电流变体在灵巧窗智能结构等方面的应用。本文所得到的一些有益和有创新意义的结果可归结如下： 1．在简要评述现有电流变效应模型及机理的基础上，按非均匀介质对双相复合悬浮液的电流变效应进行理论分析，研究了电流变效应频率诱导特性；基于复合系统渗透压的计算，采用统计热力学唯象理论，讨论了电流变效应的相分离特征，获得了与实验吻合的临界参数；首次将定向渗流模型应用于电流变体临界体积浓度的分析，得出一个描述电流变流体特征而不随外加电场变化的临界体积百分数为0.37。最后提出了作为进行电流变体专家系统设计基础的变量方程的研究设想。 2．实验研究了不同方式电场诱导电流变体微结构变化特征。通过光学显微观察，对金属及SiO₂电介质微粒的电流变体中悬浮微粒的电致成链结构进行分析，采用分形理论讨论了电流变体场致相分离结构特征，并表征了体系分形维数，得出了电场诱导电流变体聚集体的分形维数为1.78，从而证实了场致受限扩散凝聚（EDLA）生长方式对电流变效应的适应性。同时得出，分形维数（D_f）与外加电场性质无关，但随微粒的体积百分数增加而趋近于DLA生长模式的特征值1.8。 3．在场致纤维理论基础上，考察短距离排斥力和流体动力学阻力，建立了基本模型，并对电流变效应进行二维计算机仿真分析；以库仑定律为理论基础，对电流变效应进行了三维计算机仿真分析；详细讨论了电流变体结构参数及外加电场对电流变体场致成链状况的影响。采用有序参数量化了电流变体微粒电场诱导成链的结构特征。仿真结果表明，电流变体的电致成链过程可分为三个阶 中文摘要 段，即快速生长阶段，缓慢生长阶段和稳定阶段；在成链过程中，小尺寸的微 粒链和大尺寸的微粒链分别是流体的结构和其稳定性的重要决定因素。4．复合悬浮体的场致相分离特征赋予了电流变体的流变光学特性。本论文首次 较深入地分析了电流变流体光散射特性并用于制作衍射光栅及三维光学晶体 材料的可能性；在分析电流变体双折射及双色性的基础上，着重分析了场致 微结构变化对光透射特性的影响，首次提出将电流变体用于制作电控透光灵； 巧窗的结论，并设计出其模型。5．在评述即流体测试技术的基础上，针对其双折射、旋光及光透射特性，建’ 立廉价、可靠的电流变体光学特性的测试技术和系统，使获得的数据有较好 的重复性及与相关文献的可比性。 6．选择、设计并制备了一系列悬浮微粒，配制了多种电流变体，实验测试了电流变体的双折射、旋光特性，重点考察了透光可调特性，获得了从红外到可见光区域透射率频谱。研究ER i体材料组成、外加电场及添加剂对其光学特性的影响，得到一系列有实用价值的实验结果。其中，首次采用基于钛酸四丁酯的凝胶一水热法制备了长径比为 4：l的椭球状锐钛矿型 TIOZ微粒。外加直流电场E＝300V／mm前后，Sic。系ER流体ATGjJ31．66％；Tio。系ER流体太阳自透过率变化值OTG 为 37．84％；Tio。包覆石墨系 ER流体凸TG为 44．48％；纺锤形＊。系 ER流体的 ATG为 45．24“氮代 Tio。系 ER流体的 ATG可达 52．0儿此结果高于普通ECSW对光的调控水平（约 40％），在国内外未见报道。更多还原

【Abstract】 The change of structure and rheologic properties in a dispersing system of solid-liquid under an external electric field is called as electrorheological (ER) effect. Electrorheological fluids( ER fluids) is a composite suspension of polarizable solid particles with a radium of u m dispersed in an unpolarizable continuous medium. ER fluids, as a kind of smart material, possibly be revolutionary in several areas of industry and technology due to their attractive features of rapid(within ms order),reversible and dramatic changes in rheologic properties upon applied electric field of kilo-voltage per millimeter order. In this dissertation, on the basis of researches on the mechanisms of electrorheological effect and the change in microstructure of composite dispersion under the applied electric field. The theoretical analysis to rheo-optic characteristics of an electrorheological fluid under an electric field is first conducted systematically. The light-controlling properties of an electrorheological fluid is evaluated and an intelligent structure of electrorheological fluids-based smart windows (ERFSW) is proposed and designed at the first time. And thus give an developing application of electrorheological fluids in smart windows. Some helpful and new results were obtained as follows.1 .Upon brief reviewing current mathematical and physical models and mechanisms for electrorheological effect, the theoretical analysis of the dielectric relaxation of electrorheological fluids and the frequency-inducing characteristics for electrorheological effect are conducted. Based on statistical thermodynamic analysis and osmotic pressure calculating of an electrorheological fluid complex system, phenomenological theory is adopted to evaluated phase reparation characteristics. Thus critical factors corresponding to experimental results are introduced. For the first time, the oriented percolation model is applied to analyzed the critical particle concentration of 0.37 and which is characterized an electrorheological fluid and independent to the external electric field. At Last, expert system design configuration is proposed on variable function.2.The characteristics of microstructure variation induced by different space electric fields are investigated experimentally. Electrorheological fluids based on metal and silica particles dispersed in silicone oil respectively are observed by means of an optic microscope. The fractal theory is adopted to characterize phase separation ofelectrorheological fluids and the fractal dimension (Df) of an electrorheological fluid of 10% particles in silicone oil is determined as 1.78. Thus it is testified that particle chains developing process is due to electric field induced diffusion limited aggregation (EDLA) and the fractal dimension is independent to the strength of electric field but the fractal dimension of particle aggregates of Electrorhelogical fluid is up to 1.8 as characterized by diffusion limited aggregation (DLA) with the increase of particle volume concentration.3.On the basis of induced fibrillation theory, a mathematical model is developed to conduct a computer two-dimensional simulation under the consideration of short range repel and hydrokinetic obstruction. Another three-dimensional simulation model is based on the Coulomb law An ordering parameter is used to characterize the formation of particle chains. The results indicated that in the course of particles chains formation, low or high dimensions of the particle chains are decisive factors of the structure and the stability of an electrorheological fluid, respectively.4. The rheo-optic characteristics of composite suspension are due to its phase separation induced by an electric field. Light-scattering properties are in-depth analyzed and it is supposed that using an electrorheological fluid to constitute a network in an application to three-dimensional photonic crystal scattering gratings. The electric field induced birefringence and dichroism are accessed and dependence of change in mi更多还原