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Residual stresses and plasticity are well-known companions of all glassy materials. In the years, it was understood that macroscopic stress fields can be tuned to severely affect some physical properties of the material, like for example the strength in tempered glasses. Despite this, their nature at the microscopic length scale is still unclear: their behaviour is tightly linked to plasticity, i.e. local non-affine deformations that in glasses behave as stress sources coupled to the elasticity of the material. In this talk I will discuss recent X-Ray Photon Correlation Spectroscopy (XPCS) results exploring the interplay between plasticity, stress fields and the microscopic dynamics in very different systems i.e., colloidal and atomic glasses. In the colloidal system, I will show how the dynamics is dominated by residual stresses trapped-in during the preparation procedure, which give rise to a very rich phenomenology in the observed dynamical properties, as the presence of compressed relaxation functions, ballistic dynamics and dynamical heterogeneities [1]. In the second part of the talk, I will focus on oxide glasses illuminated with hard X-rays. I will show that the absorbed photons create point defects which behave as plastic regions, and their number is directly controlled by the delivered dose [2]. Following the atomic dynamics on different length-scales, I will show how the glass can behave both elastically and plastically, eventually reaching a state where the microscopic dynamical properties resemble that of a flowing system [2]. Finally, I will present a CNRS project aiming at pushing our understanding of plasticity at the microscopic length-scale. I will propose to leverage the properties of new thermo-sensitive colloidal glasses to investigate plastic activity for different level of glass equilibration (i.e., residual stresses) and external applied perturbations, combining cutting-edge experiments involving rheology, time- and space- resolved visible scattering and synchrotron-based X-ray photon correlation. [1] F. Dallari, A. Martinelli, et al., Sci. Adv. 6(12), eaaz2982 (2020). [2] A. Martinelli et al., Phys. Rev. X CR, 04LF31 (2023).

Pour plus d'informations, merci de contacter Merindol R.