BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Keynote 2 - Scattering and microscopy probes in colloidal systems under shear: Linking structure and dynamics with mechanical response DTSTART;VALUE=DATE-TIME:20181210T135000Z DTEND;VALUE=DATE-TIME:20181210T143000Z DTSTAMP;VALUE=DATE-TIME:20260523T152713Z UID:indico-contribution-85-499@lindico453.srv.lu.se DESCRIPTION:Speakers: George Petekidis (Materials science & Technology\, U niversity of Crete\, Greece)\nThe microscopic structure and dynamics in co lloidal systems at different length-scales\, from single to multiple parti cle level\, are probed under shear by a variety of scattering and direct i maging techniques. We present different studies of hard and soft particle glasses and attractive gels of spherical and rod-like colloids\, where we link the mechanical response with the underlying particle dynamics and str ucture.\nYielding of colloidal glasses under large amplitude oscillatory s hear was probed by simultaneous rheometry and light scattering with the LS -echo technique. We studied a range of colloidal systems with varying inte rparticle interactions from hard and soft sphere glasses to attractive gla sses and gels. LS-echo probes reversible and irreversible rearrangements t hat are linked with rheological yielding of the system.\nSecondly we discu ss the mechanisms responsible for a variety of shear induced structures in attractive colloidal gels and their relation to linear and nonlinear rheo logy. We use a combination of rheological experiments and rheo-confocal me asurements with computer simulations. In such thixotropic systems steady a nd oscillatory shear can be used as an external field to tune the structur e and mechanical properties of colloidal gels and drive them in metastable states\, not easily accessible at quiescent conditions.\nFinally\, we pre sent shear induced structural formations gels of attractive rod-like collo ids. More specifically we discuss the rheological response and flow induce d clustering of silica rods in a density matching solvent\, where electros tatic repulsions are screened via the addition of CsCl. A variety of simul taneous imaging techniques and rheometry reveals structural changes at dif ferent length-scales. Shear induced log-rolling clusters in the vorticity direction are formed driven by an interplay of hydrodynamic interactions\, confinement and a balance of shear and attractive forces. Structural form ation is discussed as a function of volume fraction\, shear rate\, gap siz e\, tool geometry as well as shear history.\n\nhttps://lindico453.srv.lu.s e/event/67/contributions/499/ LOCATION:Elite Hotel Ideon Tera URL:https://lindico453.srv.lu.se/event/67/contributions/499/ END:VEVENT BEGIN:VEVENT SUMMARY:Contr. Talk 2 - Orientation distributions of plate-like colloidal particles in complex flows – a synchrotron X-ray diffraction study DTSTART;VALUE=DATE-TIME:20181210T133000Z DTEND;VALUE=DATE-TIME:20181210T135000Z DTSTAMP;VALUE=DATE-TIME:20260523T152713Z UID:indico-contribution-85-498@lindico453.srv.lu.se DESCRIPTION:Speakers: Adrian Rennie ()\nSpatially resolved\, X-ray diffrac tion with synchrotron radiation permits detailed maps of the alignment of crystalline colloidal particles to be deduced and compared with fluid mech anics calculations of the flow. The angular distribution of diffracted int ensity from a given position in the pipe provides information about the or ientation distribution of the particles. Orientational alignment in a disp ersion of kaolinite particles has been investigated in several geometries. These include a uniform pipe\, at bends as well as a flow pattern that co mbines both shear and elongational stress\, namely flow at a jet created b y a 2 mm diameter nozzle inserted in a 6 mm diameter pipe [1\,2]. The alig nment is quantified and presented in terms of order parameters. The orient ation at different positions in a cylindrical pipe can be correlated with the Peclet number at different locations. The cone-shaped nozzle provides a jet of liquid giving a high degree of alignment of the particles that is uniform along lines across the conical section and constant in the small straight-sided region at the exit of the nozzle. The vortex motion that ar ises from the flow with a modest Reynolds number could be determined as we ll as the tendency for some particles to align with their large faces perp endicular to the overall flow direction at the flat surface of the nozzle outlet. Older studies will related to new challenges related to 3D-printin g polymer composites.\n\nhttps://lindico453.srv.lu.se/event/67/contributio ns/498/ LOCATION:Elite Hotel Ideon Tera URL:https://lindico453.srv.lu.se/event/67/contributions/498/ END:VEVENT BEGIN:VEVENT SUMMARY:Contr. Talk 1 - Sedimentation Induced Flow and Anomalous Dynamics in Field Driven Self-assembly of Magnetic Colloids Studied by XPCS DTSTART;VALUE=DATE-TIME:20181210T131000Z DTEND;VALUE=DATE-TIME:20181210T133000Z DTSTAMP;VALUE=DATE-TIME:20260523T152713Z UID:indico-contribution-85-497@lindico453.srv.lu.se DESCRIPTION:Speakers: Antara Pal (Division of Physical Chemistry\, Lund Un iversity)\nWe have studied the non-equilibrium dynamics of self-assembled magnetic peanut-shaped colloids in the presence of a magnetic field. The m icrometre‐sized particles align in a direction perpendicular to the appl ied external magnetic field\, and assemble into chains along the field dir ection. The anisotropic dynamics of these particles is investigated using multispeckle ultrasmall‐angle X‐ray photon correlation spectroscopy (U SA‐XPCS). Perpendicular to the applied field\, which is also the directi on of gravity\, a sedimentation induced flow develops. XPCS allows us to i nvestigate the resulting anisotropic dynamics\, and in particular to decou ple contributions from the sedimentation induced flow\, thermal diffusion of the assembled chains and individual particles\, and the internal collec tive dynamics of the assembled mesoscopic structures over a large range of length scales. Our experiments demonstrate the power of XPCS to investiga te complex dynamic processes that arise due to a combination of diffusive and flow-induced processes. Given the very small scattering volume probed in an XPCS experiments\, this opens up interesting possibilities for inves tigation spatially heterogeneous dynamics in highly turbid media that cann ot be probed with optical techniques.\n\nhttps://lindico453.srv.lu.se/even t/67/contributions/497/ LOCATION:Elite Hotel Ideon Tera URL:https://lindico453.srv.lu.se/event/67/contributions/497/ END:VEVENT BEGIN:VEVENT SUMMARY:Keynote 1 - X-ray imaging of flowing concentrated suspensions DTSTART;VALUE=DATE-TIME:20181210T123000Z DTEND;VALUE=DATE-TIME:20181210T131000Z DTSTAMP;VALUE=DATE-TIME:20260523T152713Z UID:indico-contribution-85-496@lindico453.srv.lu.se DESCRIPTION:Speakers: Guillaume Overlez (CNRS\, University of Bordeaux\, F rance)\nA key element to understand the rheological behavior of suspension s is their microstructure: the spatial distribution of particles depends o n flow history\, which has an impact on the suspension macroscopic propert ies. This appeals for the development of experimental tools allowing for t he 3D imaging of particles in viscosimetric flows. \nAt a macroscopic scal e\, concentrated suspensions often display concentration inhomogeneities\, due to shear-induced migration. These inhomogeneities can lead to the for mation of jammed regions\, which have a strong impact on the measured beha vior. It is crucial to describe this phenomenon near the jamming transitio n and in shear-thickening fluids. It is thus necessary to develop new tool s to get time- and spatially-resolved concentration fields in flowing susp ensions.\nIn this talk\, we present recent developments to tackle these is sues with the help of X-ray Imaging.\nWe first present a technique to imag e the microstructure of suspensions of non-Brownian particles in 3D\, usin g X-ray computed tomography and sub-voxel identification of particle cente rs. We illustrate its interest on a few examples. We show that one can get an isotropic microstructure after mixing. Under shear\, the microstructur e becomes anisotropic in the shear plane\, whereas it is isotropic in the 2 other planes. While for Newtonian suspensions the anisotropy is independ ent on the shear rate\, we show that for a yield-stress suspension it depe nds on it\; this implies a shear-dependent behavior of the suspension. Fin ally\, we evidence particle alignment along both solid surfaces and free i nterfaces.\nWe then present a technique to get time-resolved 2D concentrat ion fields in a rheometric flow\, thanks to 2D X-ray radiography. We illus trate its interest for shear-thickening fluids. We show that most suspensi ons display strong concentration inhomogeneities at the onset of Discontin uous Shear thickening (DST)\, which poses the question of the intrinsic (l ocal) behavior of DST suspensions and might lead to revisit the interpreta tion of this behavior.\n\nhttps://lindico453.srv.lu.se/event/67/contributi ons/496/ LOCATION:Elite Hotel Ideon Tera URL:https://lindico453.srv.lu.se/event/67/contributions/496/ END:VEVENT END:VCALENDAR