Reference : Dynamics of viscoelastic colloidal suspensions
Dissertations and theses : Doctoral thesis
Physical, chemical, mathematical & earth Sciences : Physics
Physics and Materials Science
Dynamics of viscoelastic colloidal suspensions
Dannert, Rick mailto [University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit >]
University of Luxembourg, ​​Luxembourg
Docteur en Physique
Sanctuary, Roland mailto
Michels, Andreas mailto
Wagner, Christian mailto
Baller, Jörg mailto
Winter, Henning mailto
[en] colloidal suspensions ; rheology ; structure-property relationships
[en] The influence of different types of nanoparticles on the dynamics of glass forming matrices has been studied by small oscillatory shear rheology. Experimental measurements reveal that besides the glass transition process of the matrix an additional relaxation process occurs in presence of nanoparticles. The latter is identified as the macroscopic signature of the microscopic temporal fluctuations of the intrinsic stress and is called Brownian relaxation. Besides the fact that Brownian relaxation has so far not been observed in colloidal suspensions with a matrix exhibiting viscoelastic behaviour in the frequency range of the experimental probe, the study reveals another important feature to be highlighted: the evolution of the Brownian relaxation times depends non-monotonously on the filler concentration. This finding challenges the use of the classical Peclet-time as a characteristic timescale for Brownian relaxation. Literature defines the Peclet-time as the specific time needed by a particle to cover –via self-diffusion- a distance comparable to its own size. As a main result it will be shown that after replacing the particle size which is relevant for the Peclet time by the mean interparticle distance depending on the filler content the non-monotonic evolution of the relaxation times can be fully described. Moreover, the introduction of the new characteristic length scale allows to include data from literature into the phenomenological description.
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