Machrafi Hatim
Thermodynamique des Phénomènes Irréversibles, Institut de Physique, Université de Liège, Liège 4000, Belgium.
Nanoscale. 2020 Jul 23;12(28):15081-15101. doi: 10.1039/d0nr03130e.
The effective viscosity of nanoparticle dispersions has been investigated experimentally quite a lot and various behaviours have been observed. Many models have been proposed to predict the effective viscosity, but these are mainly empirical ones, correlations with a tuning parameter or based on fastidious molecular interactions simulations. In this work, we propose a new fully physics-based analytical expression for the effective viscosity implementing theories from extended thermodynamics, including nano-confinement effects, nanoparticle-fluid interactions, density effects, size effects and nanoparticle volume fraction. We validate this model against several different types of nanoparticle dispersions and emulsions and explain the different behaviours using the same model. It appears that the density ratio of the nanoparticles with respect to the fluid plays a crucial role affecting the viscosity. The nanoparticle-fluid interactions become increasingly important for smaller nanoparticle sizes. From these comparisons, we arrive at a general simplified expression for the effective viscosity of nanoparticle dispersions, where it is observed that there is a direct universal relation between the nanoparticles and fluid densities and the nanodispersion viscosities. The validity of such a relation has been explicitly demonstrated.
纳米颗粒分散体的有效粘度已经得到了大量的实验研究，并且观察到了各种行为。已经提出了许多模型来预测有效粘度，但这些主要是经验模型、带有调整参数的相关性模型或基于繁琐分子相互作用模拟的模型。在这项工作中，我们基于扩展热力学理论，提出了一种新的、完全基于物理的有效粘度解析表达式，该表达式考虑了纳米限域效应、纳米颗粒与流体的相互作用、密度效应、尺寸效应和纳米颗粒体积分数。我们针对几种不同类型的纳米颗粒分散体和乳液对该模型进行了验证，并使用同一模型解释了不同的行为。结果表明，纳米颗粒与流体的密度比在影响粘度方面起着关键作用。对于较小尺寸的纳米颗粒，纳米颗粒与流体的相互作用变得越来越重要。通过这些比较，我们得出了纳米颗粒分散体有效粘度的一般简化表达式，从中可以观察到纳米颗粒与流体密度和纳米分散体粘度之间存在直接的普遍关系。这种关系的有效性已经得到了明确证明。
