This paper describes the European Space Agency (ESA) experiments devoted to study thermodiffusion of fluid mixtures in microgravity environment, where sedimentation and convection do not affect the mass flow induced by the Soret effect. First, the experiments performed on binary mixtures in the IVIDIL and GRADFLEX experiments are described. Then, further experiments on ternary mixtures and complex fluids performed in DCMIX and planned to be performed in the context of the NEUF-DIX project are presented. Finally, multi-component mixtures studied in the SCCO project are detailed.

No abstract

Thermodiffusion, which leads to a component separation in a mixture due to the thermal gradient, still does not have an unambiguous microscopic picture. Therefore, experimental studies, especially in convection free environment, are important. As part of the 4th campaign on the DCMIX project, thermodiffusion experiments on three compositions of the toluene-methanol-cyclohexane ternary mixture, on a mixture of fullerene-tetrahydronaphthalene-toluene and on a mixture of polystyrene-toluene-cyclohexane have been performed in microgravity conditions on board the International Space Station. A binary mixture of polystyrene-toluene has been filled into the companion cell for the campaign. The Selectable Optical Diagnostics Instrument (SODI), wich is a two-wavelength Mach-Zehnder interferometer for the ternary mixtures, plus a monochromatic Mach-Zehnder interferometer for the binary mixture, has been used in order to obtain the temperature and the concentration fields in the cells. Precisely, it is a 5-steps phase-shifting interferometry technique which is implemented with SODI, producing by means of laser illumination a set of 5 phase-shifted images of between them as function of the time. A total of 58 runs of various durations and at different mean temperatures have been conducted. Here, we evaluate the contrast of the interferograms, the quality in the phase stepping, the stability of the thermal regulation of the experiments and the level of environmental disturbances on board the space station during the campaign.

In the frame of the Diffusion Coefficient Measurements in ternary mIXtures 4 (DCMIX4) project the thermodiffusion experiments were conducted on the International Space Station (ISS) in the Selectable Optical Diagnostics Instrument (SODI) which is on orbit since 2009. We describe the results of the preliminary analysis of images downloaded during the execution of DCMIX4 in order to check the quality of the running experiments and, if needed, adjust the experiment parameters for the following runs. The quick analysis of raw data showed that they are meaningful and will allow to obtain the transport coefficients of examined ternary and binary mixtures.

No abstract

No abstract

No abstract

We have measured isothermal and non-isothermal mass transport properties of fullerene C 60 in two different organic solvents, tetralin and toluene, and compared these measurements with the respective properties of the binary mixture of the pure solvents. In addition, a set of thermophysical and optical properties of the mixtures needed for extraction of the transport properties was measured and parameterized. Five different instruments used in this work for assessing the transport properties were extensively tested and benchmarked previously and have shown reliable and accurate results. The use of the instruments allowed us to provide the diffusion, thermodiffusion, and Soret coefficients at 298.15 K and normal pressure with an accuracy better than 5%. The hydrodynamic radii calculated from the diffusion coefficients agree with literature values for the fullerene radius, which proves the absence of fullerene aggregation in the studied mixtures. While the values of diffusion coefficients are within the range typical for molecular mixtures, the Soret coefficients are an order of magnitude higher and fall into the gap between ordinary molecular mixtures (S T < 10 −2 K −1 ) and colloids/nanofluids (S T > 10 −1 K −1 ).