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Shear viscosity relaxation of a critical binary liquid
1Drittes Physikalisches Institut, Georg-August-University Göttingen, Bürgerstrasse 42-44, 37073 Göttingen, Germany. behrends@physik3.gwdg.de
Summary
Diffusion coefficients for triethylamine-water critical mixtures were determined using light scattering and ultrasonic spectra. Both methods agree when accounting for frequency-dependent viscosity, revealing insights into critical phenomena.
Area of Science:
- Physical Chemistry
- Fluid Dynamics
- Materials Science
Background:
- Binary critical mixtures exhibit complex dynamics near the critical point.
- Understanding diffusion coefficients is crucial for characterizing fluid behavior.
Purpose of the Study:
- To report diffusion coefficients for the triethylamine-water binary critical mixture.
- To reconcile data from quasielastic light scattering and broadband ultrasonic spectra.
- To investigate the role of frequency-dependent viscosity in critical phenomena.
Main Methods:
- Quasielastic light scattering measurements.
- Broadband ultrasonic spectra analysis to determine relaxation rates and shear viscosity.
- High-frequency shear impedance spectrometry (20-130 MHz) to probe viscoelastic properties.
Main Results:
- Two series of diffusion coefficients were obtained and compared.
- Agreement between the two series was achieved by adjusting the Bhattacharjee-Ferrell scaling function or using frequency-dependent viscosity in the Kawasaki-Ferrell relation.
- Extrapolated viscosity from shear impedance measurements was lower than static shear viscosity.
Conclusions:
- The study provides consistent diffusion coefficient data for the triethylamine-water critical mixture.
- Viscoelastic properties and frequency-dependent viscosity play a significant role in accurately describing critical dynamics.
- The findings contribute to a deeper understanding of fluid behavior near critical points.