Sehnem A L, Figueiredo Neto A M, Aquino R, Campos A F C, Tourinho F A, Depeyrot J
Instituto de Física, Universidade de São Paulo, São Paulo, Brazil.
Faculdade UnB-Planaltina, Universidade de Brasília, Brasília, Distrito Federal, Brazil.
Phys Rev E Stat Nonlin Soft Matter Phys. 2015 Oct;92(4):042311. doi: 10.1103/PhysRevE.92.042311. Epub 2015 Oct 19.
The temperature dependence of the Soret coefficient S(T)(T) in electrostatically charged magnetic colloids is investigated. Two different ferrofluids, with different particles' mean dimensions, are studied. In both cases we obtain a thermophilic behavior of the Soret effect. The temperature dependence of the Soret coefficient is described assuming that the nanoparticles migrate along the ionic thermoelectric field created by the thermal gradient. A model based on the contributions from the thermoelectrophoresis and variation of the double-layer energy, without fitting parameters, is used to describe the experimental results of the colloid with the bigger particles. To do so, independent measurements of the ζ potential, mass diffusion coefficient, and Seebeck coefficient are performed. The agreement of the theory and the experimental results is rather good. In the case of the ferrofluid with smaller particles, it is not possible to get experimentally reliable values of the ζ potential and the model described is used to evaluate this parameter and its temperature dependence.
研究了静电充电磁性胶体中索雷特系数S(T)对温度的依赖性。研究了两种具有不同颗粒平均尺寸的不同铁磁流体。在这两种情况下，我们都得到了索雷特效应的嗜热行为。假设纳米颗粒沿着由热梯度产生的离子热电场迁移，描述了索雷特系数对温度的依赖性。一个基于热泳贡献和双层能量变化且无拟合参数的模型被用于描述较大颗粒胶体的实验结果。为此，对ζ电位、质量扩散系数和塞贝克系数进行了独立测量。理论与实验结果吻合得相当好。对于颗粒较小的铁磁流体，无法通过实验获得可靠的ζ电位值，因此使用所描述的模型来评估该参数及其对温度的依赖性。
