15 April 2010 Thermal fluctuation exponents for two near-critical point systems
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Abstract
In the supercritical phase, pure fluids have great potential for industrial applications and are increasingly used by industry as nonpolluting solvents of organic materials and media for high yield chemical reactions. The experimental data were recorded in microgravity for sulfur hexafluoride (SF6) and on Earth for density-matching binary mixture of methanol and partially deuterated cyclohexane (CC*-Me). We used small angle light scattering experiments to investigate fluctuations in SF6 near critical point and in density-matched binary mixture CC*-Me in the absence of convective flows. For binary mixture, we used three different filtering methods: bright filed (BF - no filter), phase contrast (PC - quarter wave plate at focal point) and dark field (DF - small opaque object at focal point). The power spectrum of scattered light contains information about local inhomogeneities encountered by light traveling through the sample cell unit (SCU). We found that the spatial correlations revealed by Fourier transforms follow power laws both for SF6 in microgravity and binary mixture on Earth. This is an indication of the universality of fluctuation mechanisms. Temporal correlations of fluctuations were investigated using the correlation time.
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Ana Oprisan, Brittany Bayley, Sorinel A. Oprisan, John J. Hegseth, Yves Garrabos, Carole Lecoutre, Daniel Beysens, "Thermal fluctuation exponents for two near-critical point systems", Proc. SPIE 7701, Visual Information Processing XIX, 77010W (15 April 2010); doi: 10.1117/12.850557; https://doi.org/10.1117/12.850557
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