透明电流变液性能调控与机理研究

As low-power-consumed smart materials, electrorheological (ER) fluids are attracting considerable interest in the studies of new ER materials development, potential applications and theoretical models. However, to date there is no full and uniform understanding to the mechanisms of ER effect, which blocks the substantive development of ER properties. On the other hand, the previous researches on ER fluids mainly focus on their rheological properties, lacking the development of new physical properties. In this work, we are planning to fabricate an ER fluid with typical optical transparency by matching the refractive indexes of base oil and suspended particles. In this dielectric-matched ER fluid, we are interested in how the ER effect is generated and affected by the properties of the suspended particles, for example, the particle size, inner and outer chemical structures, especially the modification of polar and ionic molecules or groups. These factors also have effect on the transparency of the ER fluid, thus need to be adjusted properly by considering both sides, i.e., ER effect and transparency. The development of transparent ER fluid with controllable light transmittance and ER effect is expected to bring a new concept in the research of ER fluids and finally contribute to their application in more advanced devices.

电流变液作为一种低能耗的智能流体，它的开发、应用和理论研究吸引着越来越多的关注。然而，一直以来人们对电流变效应的机理仍没有充分和统一的认识，阻碍了电流变液性能的实质性突破。对电流变液的现有研究中另一方面的局限性在于大多只关注其流变学性能，导致对其它物理特性的开发和研究尚且缺乏。本课题选择用折射率匹配的方法制备具有光学透明特性的电流变液，并以此为研究对象，对分散于其中的固体颗粒的内部和表层的化学结构以及粒径进行调节，尤其是用极性分子或离子基团对颗粒表层进行修饰，改变其极化性能，从中探究影响透明电流变液（即介电匹配体系）透光率和电流变效应的主要因素和作用机理，实现对透明电流变液性能的双向调控。本课题的研究将为电流变液的研究植入新的概念，丰富其基础研究内容，并为其应用创造有利条件。

通过将分散相和连续相折射率匹配制备了透明的电流变液，主要选用二氧化硅、纤维素以及聚离子液体等作为分散相颗粒，对其进行化学修饰、改变粒径和形貌等，研究了条件改变对其电流变效应和透光率的影响。实验表明，随二氧化硅粒径减小，电流变液的透光率明显增加，用尿素分子对纳米二氧化硅进行修饰，其电流变效应明显提升，控制尿素含量，可使其透光率达到90%以上，且屈服应力在kPa级。介电性能研究也证实了尿素分子修饰可以提高电流变液的介电强度和弛豫时间，与其修饰后较高的电流变效应相对应。通过对原始棒状纤维素进行水解，其粒径和形貌都发生改变，但是由于纤维素的氢键作用较强，即便水解也难形成均匀纳米颗粒，所以其透光率也很难达到较理想的提升。在电流变效应方面，通过延长水解时间，或是碱溶胀条件下用硅烷偶联剂修饰，可以提高纤维素的屈服强度。综上研究，极性分子修饰可以提高二氧化硅或纤维素的电流变效应，但只有二氧化硅可以得到透光率较高的透明电流变液。