The Measurement of Soret and Thermodiffusion Coefficients in Binary and Ternary Liquid Mixtures

Abstract

This review provides an overview of the major, currently used techniques for investigating the Soret effect and measuring thermodiffusion and Soret coefficients, and in most cases also isothermal Fickian diffusion coefficients, in liquid mixtures. The methods are introduced with a focus on binary mixtures. The optical methods comprise optical beam deflection (OBD), optical digital interferometry (ODI) both on the ground and under microgravity conditions in the SODI-IVIDIL experiment for the study of the influence of vibrations onboard the International Space Station, which are all based on Soret cells. The transient holographic grating technique of thermal diffusion-forced Rayleigh scattering (TDFRS) employs light not only for detection of the concentration changes but also for optical volume heating. Thermogravitational columns (TGC) utilize the coupling between convection and thermodiffusion to create concentration changes inside a vertical column with a horizontal temperature gradient. While samples are analyzed after extraction from the column in a classical setup, the recently developed transparent microcolumn allows for interferometric in situ monitoring of the concentration field. The most recent technique relies on the measurement of giant non-equilibrium fluctuations (NEFs) by small-angle light scattering techniques. Research on ternary mixtures, both on the ground and in microgravity, has gained momentum in the context of the DCMIX microgravity project of ESA. Most techniques employed for binaries can be extended to ternaries by introducing a second detection color or by analyzing both refractive index and density of extracted TGC samples. The accuracy is limited by the unavoidable inversion of the so-called contrast factor matrix.

Speleothem-Inspired Copper/Nickel Interfaces for Enhanced Liquid–Vapor Transport by Marangoni and Soret Effects

“…As a result, the Soret effect reduces the wall superheat by accumulating the component with the higher partial pressure near the surface. This ensures a continuous liquid supply to the nucleation sites, preventing dry-out and maintaining the efficient replenishment of the liquid phase. ,, It is suggested that varying the magnetic field strength could be a viable method to fine-tune the nickel alignment morphology and optimize performance further. Further investigations are warranted to explore and fine-tune the alignment morphologies of the Cu/Ni surfaces.…”

“…Additionally, the Soret and Marangoni effects arising from the surface tension and concentration gradients within the binary mixture also contribute to the improved boiling performance. The Soret effect, or thermal diffusion, causes a separation of the mixture components in response to a temperature gradient. , The Marangoni effect, on the other hand, induces fluid motion along the interface due to a surface tension gradient. This effect can cause the vapor bubbles in the binary mixture to shift toward the high-temperature area, further promoting liquid replenishment at the nucleation sites and preventing dry-out. , The impact of the Soret and Marangoni effects on heat transfer characteristics has been well-documented for plain surfaces.…”

Isothermal and non-isothermal transport properties of diluted fullerene binary and ternary aromatic solvent mixtures

“…Further setup specifications and details of the fitting procedure can be found elsewhere. 42 As can be deduced from eqn (4), OBD requires optical properties of the sample, such as the thermal (qn/qT) p,c and solutal contrast factors (qn/qc) p,T . The former quantifies the variation of the refractive index as a function of temperature and is determined using a classical Michelson interferometer.…”