%0 Book Section %1 statphys23_0456 %A Fluerasu, A. %A Moussaid, A. %A Madsen, A. %A Schofield, A. %B Abstract Book of the XXIII IUPAP International Conference on Statistical Physics %C Genova, Italy %D 2007 %E Pietronero, Luciano %E Loreto, Vittorio %E Zapperi, Stefano %K aging correlation depletion dynamics gel photon slow spectroscopy statphys23 topic-7 transient x-ray %T Slow dynamics and aging in colloidal gels studied by XPCS %U http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=456 %X Aggregation and gelation are topics of fundamental interest in condensed matter physics that also have many direct industrial applications. Delayed sedimentation in transient gels is a non-equilibrium phenomenon encountered in a variety of soft matter systems, including colloidal suspensions with strong-enough short-ranged attractive interactions. Due to the interactions, the colloidal particles can aggregate at much lower concentrations (e.g. 20\%) than those leading to the formation of glasses in hard-sphere systems (~60\%), to form a space-filling structure often denoted a gel. However, this non-equilibrium structure slowly evolves, until the spatial connectivity is lost and the gel suddenly collapses. A common generic behavior of disordered soft-matter systems such as colloidal glasses and gels is the presence of several dynamical relaxation mechanisms. The fast(er) ones correspond to the confined motion of individual particles or aggregates in cages or clusters created by neighboring particles/aggregates. Because the clustering can lead to structural arrest, such systems are generally non-ergodic. It is through the slow relaxations, corresponding to structural re-arrangements equivalent to the $\alpha$ process in glasses that the system eventually can reach equilibrium and ergodicity may be restored. In this paper we study the slow, non-equilibrium dynamics during delayed sedimentation in a colloidal depletion gel by X-ray photon correlation spectroscopy (XPCS). The age-dependent intermediate scattering functions are calculated form the two-time autocorrelation functions of the scattered intensity and fitted with Kohlrausch-Williams-Watts (KWW) stretched exponential forms, $g_1(Q,t)=expłeft-łeft( \Gamma t\right)^\right +g_ınfty$. The relaxations change during the process from stretched ($\gamma<1$) to compressed ($\gamma>1$) exponential decays indicating a jamming transition towards full aging. A complex aging behavior follows this process and it is proposed that large scale network deformations trigger an un-jamming leading to the final collapse of the gel.

@incollection{statphys23_0456, abstract = {Aggregation and gelation are topics of fundamental interest in condensed matter physics that also have many direct industrial applications. Delayed sedimentation in transient gels is a non-equilibrium phenomenon encountered in a variety of soft matter systems, including colloidal suspensions with strong-enough short-ranged attractive interactions. Due to the interactions, the colloidal particles can aggregate at much lower concentrations (e.g. 20\%) than those leading to the formation of glasses in hard-sphere systems (~60\%), to form a space-filling structure often denoted a gel. However, this non-equilibrium structure slowly evolves, until the spatial connectivity is lost and the gel suddenly collapses. A common generic behavior of disordered soft-matter systems such as colloidal glasses and gels is the presence of several dynamical relaxation mechanisms. The fast(er) ones correspond to the confined motion of individual particles or aggregates in cages or clusters created by neighboring particles/aggregates. Because the clustering can lead to structural arrest, such systems are generally non-ergodic. It is through the slow relaxations, corresponding to structural re-arrangements equivalent to the $\alpha$ process in glasses that the system eventually can reach equilibrium and ergodicity may be restored. In this paper we study the slow, non-equilibrium dynamics during delayed sedimentation in a colloidal depletion gel by X-ray photon correlation spectroscopy (XPCS). The age-dependent intermediate scattering functions are calculated form the two-time autocorrelation functions of the scattered intensity and fitted with Kohlrausch-Williams-Watts (KWW) stretched exponential forms, $g_1(Q,t)=exp\left[-\left( \Gamma t\right)^\gamma \right] +g_\infty$. The relaxations change during the process from stretched ($\gamma<1$) to compressed ($\gamma>1$) exponential decays indicating a jamming transition towards full aging. A complex aging behavior follows this process and it is proposed that large scale network deformations trigger an un-jamming leading to the final collapse of the gel.}, added-at = {2007-06-20T10:16:09.000+0200}, address = {Genova, Italy}, author = {Fluerasu, A. and Moussaid, A. and Madsen, A. and Schofield, A.}, biburl = {https://www.bibsonomy.org/bibtex/2e8a3461ffc08232691049612ba5aa83d/statphys23}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Pietronero, Luciano and Loreto, Vittorio and Zapperi, Stefano}, interhash = {3b185f1840f0016741bce52e479f5640}, intrahash = {e8a3461ffc08232691049612ba5aa83d}, keywords = {aging correlation depletion dynamics gel photon slow spectroscopy statphys23 topic-7 transient x-ray}, month = {9-13 July}, timestamp = {2007-06-20T10:16:20.000+0200}, title = {Slow dynamics and aging in colloidal gels studied by XPCS}, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=456}, year = 2007 }