Gong Xiuqing, Wu Jinbo, Huang Xianxiang, Wen Weijia, Sheng Ping
Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
Nanotechnology. 2008 Apr 23;19(16):165602. doi: 10.1088/0957-4484/19/16/165602. Epub 2008 Mar 20.
We show that the chemical structures of silicone oils can have an important role in the giant electrorheological (GER) effect. The interaction between silicone oils and solid nanoparticles is found to significantly influence the ER effect. By increasing the kinematic viscosity of silicone oils, which is a function of siloxane chain length, sol-like, gel-like and clay-like appearances of the constituted ER fluids were observed. Different functional-group-terminated silicone oils were also employed as the dispersing media. Significant differences of yield stress were found. We systematically study the effect of siloxane chain lengths on the permeability of oils traveling through the porous spaces between the particles (using the Washburn method), oils adsorbed on the particles' surface (using FT-IR spectra), as well as their particle size distribution (using dynamic light scattering). Our results indicate the hydrogen bonds are instrumental in linking the silicone oil to GER solid particles, and long chain lengths can enhance the agglomeration of the GER nanoparticles to form large clusters. An optimal oil structure, with hydroxyl-terminated silicone oil and a suitable viscosity, was chosen which can create the highest yield stress of ∼300 kPa under a 5 kV mm(-1) DC electric field.
我们表明，硅油的化学结构在巨大电流变（GER）效应中可发挥重要作用。发现硅油与固体纳米颗粒之间的相互作用会显著影响电流变效应。通过增加硅油的运动粘度（其是硅氧烷链长度的函数），观察到所构成的电流变流体呈现溶胶状、凝胶状和黏土状外观。还使用了不同官能团封端的硅油作为分散介质。发现屈服应力存在显著差异。我们系统地研究了硅氧烷链长度对油通过颗粒间孔隙的渗透率（使用沃什伯恩方法）、吸附在颗粒表面的油（使用傅里叶变换红外光谱）以及它们的粒度分布（使用动态光散射）的影响。我们的结果表明，氢键有助于将硅油与GER固体颗粒连接起来，并且长链长度可增强GER纳米颗粒的团聚以形成大的聚集体。选择了具有羟基封端的硅油和合适粘度的最佳油结构，其在5 kV mm⁻¹直流电场下可产生高达约300 kPa的屈服应力。
