巨电流变液体与传统电流变液体流变行为研究

The shear yield strengths of conventional electrorheological fluids and giant electrorheological fluids have different dependences on the imposed electric field. The conventional electrorheological fluid has a square relationship while the giant electrorheological fluid has a linear relationship, which clearly shows that they have totally different rheological behaviors. However, there still lack systematical studies on the rheological behavior of those two kinds of electrorheological fluids. The inverted torsion rheometer can measure not only the mechanical linear response: linear viscoelasticity and resonant absorption spectra but also the Fourier rheological spectra, which is well able to characterize the nonlinear mechanical response. This project proposes to study the rheological behaviors of both conventional electrorheological fluids and giant electrorheological fluids in detail by the inverted torsion rheometer. Specifically, the researches include: 1) the shear viscoelasticity and shear wave absorption spectra and their evolution under an imposed electric field; 2) the nonlinear mechanical response represented by Fourier rheological spectra and its dependence on the shear amplitude, the imposed electric field. At the same time molecular dynamic simulation is also applied to shed light into the microstructures and their evolution under an electric field. Through these efforts it is hoped to have a better understanding on the characteristics of both conventional electrorheological fluids and giant electrorheologial fluids, and to propose their respective mechanism of electrorheological effects.

传统电流变液体的剪切强度和外电场强度是二次幂关系而巨电流变液体的剪切强度和外电场强度成线性关系，这表明：它们具有完全不同的流变行为；然而目前仍缺乏对二类电流变液体流变行为的系统研究。基于倒扭摆的流变仪不仅能测量软物质力学线性响应行为（线性粘弹特性、切变波共振吸收谱）而且能测量傅里叶变换流变谱（适于表征流变体中的非线性行为）；本项目提出应用基于倒扭摆的流变仪系统地研究传统电流变液与巨电流变液在电场下剪切流变行为的差别：1）剪切粘弹特性和切变波共振吸收谱及其在电场下的演化；2）傅里叶谱所表征的非线性流变行为及其对剪切振幅、外加电场强度等的依赖关系；同时结合分子动力学模拟研究揭示传统电流变液与巨电流变液在电场作用下微结构及其演化的差异，从而得到传统电流变液与巨电流变液各自的电流变特征，提出它们相应的电流变机理。

本项目成功制备了含水二氧化钛颗粒和碳掺杂二氧化钛颗粒，与硅油混合后得到优良的电流变液。其中前者为典型的极性分子型巨电流变液体系，为最简单的巨电流变液体系，并用极性分子取向成键模型成功解释了实验现象；后者屈服强度能达到巨电流变液的标准，即大于100kPa，但其漏电流、寿命、温度稳定性等数据说明这是种全新的体系，且具有实用价值。