How to train your gel? Training and overaging in colloidal gels using rheo-SAXS-XPCS measurements

Amorphous materials such as polymeric, colloidal or spin glasses are thermodynamically out of equilibrium materials. Such materials undergo aging, a microstructural evolution under quiescent conditions, wherein their free energy decreases with time [1]. Aging can be altered by training the material with a succession of small amplitude creeps and relaxations without breaking the material such that the material reaches deeper minimum in its free energy landscape than it would during quiescent aging. Overaging has been extensively studied in colloidal glasses and leads to a higher material elasticity and a slowdown of the relaxation time scales. Yet, overaging in colloidal gels is not fully documented (no dynamics measurements). Here, we aim to show that the training of colloidal gels leads to overaging using rheology coupled to SAXS and XPCS. We will vary the training protocol (to test for efficiency) and compare two gels: carbon black gels and ludox gels to go for universal trends.