rheo-echo-XPCS to study the dynamic of the yielding transition in colloidal glasses

The yielding transition in glassy colloidal suspensions is a solid-to-fluid transition induced by shear. This transition has been studied with rheology yet its dynamics is not well characterized. Here, using rheo-echo-XPCS, we aim to perform series of oscillatory strain experiments at constant strain amplitude in stationary conditions and construct stroboscopically, every oscillatory period, the intermediate scattering function (ISF) using XPCS. The analysis of the echo-ISF yield the dynamics of the colloidal dispersion as a function of the strain amplitude and the wave vector q. We expect to better understand the mechanisms at play as we increase the strain amplitude and reach the yield strain γy. In particular, is there an α and β brelaxation that accelerate as we approach gy. Can the measured echo-ISF(q,γy,t) be mapped on the ISF function of supercooled colloids driven by the volume fraction Φ, ISF(q,Φ,dt). We will test hard sphere and fumed silica colloidal glasses.