Structure and phase diagram of an adhesive colloidal dispersion under high pressure: A small angle neutron scattering, diffusing wave spectroscopy, and light scatttering study
| Autor: | Minne Paul Lettinga, Johan Buitenhuis, M. Ratajczyk, R. Vavrin, Joachim Kohlbrecher, Guido Meier, Agnieszka Wilk |
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| Jazyk: | angličtina |
| Rok vydání: | 2009 |
| Předmět: |
Spinodal
Diffusing-wave spectroscopy Materials science Condensed matter physics Analytical chemistry General Physics and Astronomy Percolation threshold Small-angle neutron scattering light scattering Light scattering Condensed Matter::Soft Condensed Matter percolation neutron diffraction Dynamic light scattering colloids Phase (matter) Percolation ddc:540 Physical and Theoretical Chemistry adhesives phase separation silicon compounds phase diagrams high-pressure effects |
| Zdroj: | The journal of chemical physics 130, 154903 (2009). doi:10.1063/1.3103245 |
| DOI: | 10.1063/1.3103245 |
| Popis: | We have applied small angle neutron scattering (SANS), diffusing wave spectroscopy (DWS), and dynamic light scattering (DLS) to investigate the phase diagram of a sterically stabilized colloidal system consisting of octadecyl grafted silica particles dispersed in toluene. This system is known to exhibit gas-liquid phase separation and percolation, depending on temperature T, pressure P, and concentration phi. We have determined by DLS the pressure dependence of the coexistence temperature and the spinodal temperature to be dP/dT=77 bar/K. The gel line or percolation limit was measured by DWS under high pressure using the condition that the system became nonergodic when crossing it and we determined the coexistence line at higher volume fractions from the DWS limit of turbid samples. From SANS measurements we determined the stickiness parameter tau(B)(P,T,phi) of the Baxter model, characterizing a polydisperse adhesive hard sphere, using a global fit routine on all curves in the homogenous regime at various temperatures, pressures, and concentrations. The phase coexistence and percolation line as predicted from tau(B)(P,T,phi) correspond with the determinations by DWS and were used to construct an experimental phase diagram for a polydisperse sticky hard sphere model system. A comparison with theory shows good agreement especially concerning the predictions for the percolation threshold. From the analysis of the forward scattering we find a critical scaling law for the susceptibility corresponding to mean field behavior. This finding is also supported by the critical scaling properties of the collective diffusion. |
| Databáze: | OpenAIRE |
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