Complex vitrification and physical aging in glasses
Date: 2023/11/02 - 2023/11/02
Academic Seminar: Complex vitrification and physical aging in glasses
Speaker: Daniele Cangialosi, Tenured Scientist at the Material Physics Center, San Sebastián, Spain
Time: 10:00 a.m., November 2, 2023 (Beijing Time)
Location: Room 454, JI Long Bin Building
Conventional description of vitrification, taking place at the glass transition temperature Tg, and the subsequent evolution of the glass towards equilibrium, known as physical aging or structural relaxation, relies on the exclusive role of the main relaxation exhibiting super-Arrhenius temperature dependence. In the present talk, I will show that, exploring a wide range of observation time scales and temperatures, the relaxation is unable to catch the whole phenomenology of vitrification and physical aging. Specifically, cooling rate dependent Tg in a wide range for glasses of different nature exhibits milder temperature dependence than the relaxation time. Furthermore, when physical aging is carried considerably below Tg, approach to equilibrium exhibits increasing stretching with decreasing temperature. Further temperature decrease results in a splitting with different step-decays to equilibrium. These results underline that, apart from the relaxation, non-equilibrium glass kinetics is triggered by fast mildly activated mechanisms of equilibration. Their persistence at temperatures way below Tg, can be used to convey glasses to low energy states, in particular those relevant to gain insights on the existence of the ideal glass.
Daniele Cangialosi obtained his PhD in 2001 at the University of Palermo, Italy. From 2001 and 2004 he was in The Netherlands, Technical University of Delft, for a 3 year postdoctoral fellowship. Before obtaining his current position, he was a postdoctoral fellow at the Donostia International Physics Center (DIPC) and at the Material Physics Center in San Sebastián, Spain. Since 2009, he is a Tenured Scientist at the Material Physics Center (Joint Center of the UPV/EHU and CSIC). His specialization is in dielectric spectroscopy and calorimetric techniques. The focus of his recent research activity is the problem of the glass transition in the bulk and under nanoscale confinement. He devoted special attention to the nonequilibrium dynamics, that is, the recovery of equilibrium in the so-called physical aging regime. Nowadays Daniele Cangialosi is widely recognized in the polymer physics community in these topics, as testified by the numerous chapters and reviews on the topic and invitations to congresses such as the American Physical Society (APS) March Meeting (3 invitations), the American Chemical Society (ACS), the DPG (German Society of Physics) Conference and the Laehnwitzseimnar on Calorimetry at Rostock (3 invitations). Cangialosi has published more than 90 articles, of which 3 reviews, in scientific journal as Science Advances, Nature Communications, Progress in Polymer Science, Advances Materials and Physical Review Letters; and 9 book chapters.