Science Daily May 1, 2023
The direct connections between the macroscopic flow/deformation and microscopic structure or dynamics has not been determined. An international team of researchers (USA – University of Illinois, Argonne National Laboratory, South Korea, Canada) They probed the microstructural yielding dynamics of a concentrated colloidal system by performing creep/recovery tests with simultaneous collection of coherent scattering data via X-ray Photon Correlation Spectroscopy (XPCS). This combination of rheology and scattering allowed for time-resolved observations of the microstructural dynamics as yielding occurred, which could be linked back to the applied rheological deformation to form structure–property relations. Under sufficiently small, applied creep stresses, examination of the correlation in the flow direction revealed that the scattering response recorrelates with its preformed state, indicating nearly complete microstructural recovery, and the dynamics of the system under these conditions slowed considerably. Conversely, larger creep stresses increased the speed of the dynamics under both applied creep and recovery. The data showed a strong connection between the microstructural dynamics and the acquisition of unrecoverable strain. By comparing this relationship to that predicted from homogeneous, affine shearing, they found that the yielding transition in concentrated colloidal systems was highly heterogeneous on the microstructural level. Their work could help bring advances to various materials engineering challenges — ranging from the formulation of better 3D printing inks, wearable flexible electronics, sensors, the accurate printing, to helping control landslides and avalanches. etc… read more. TECHNICAL ARTICLEÂ