纳米尺度下流体的流变及尺度效应

RHEOLOGICAL PROPERTIES AND DIMENSION EFFECTS OF FLUID AT NANOMETER SCALE

应用表面力仪研究了流体在纳米尺度下的流变及尺度效应。试验发现，体相状态时表现为典型牛顿流体的16 烷，在纳米膜厚状态下，出现了等效粘度随切应变速率的增大而减小的剪切稀化现象，并且等效粘度依赖于振动剪切的频率。随着膜厚从宏观量级进入到纳米量级，流体的特性具有了显著的膜厚相关性，其表现为等效粘度明显增大，流体出现了弹性特征，摩擦力表现出复杂的非牛顿特性。其他流体也表现出类似的特性，这些流变特性的改变，说明纳米尺度下流体具有与体相状态完全不同的特性。

By Surface force apparatus (SFA) technique, the rheological properties and dimension effects are studied. The experiments show hexadecane, which is typical Newtonian fluid in bulk state, exhibits the characteristics of shear thinning and the dependence of viscosity on frequency. In the transition from macro to micro-lubrication, the fluid shows nonlinear friction and elastic phenomena. These characteristics differ from those in the bulk and depend apparently on the film thickness. The fluid confined in molecularly thin films undergo a great change in its rheology.