THE TRANSFORMATION OF GLASS OVER TIME

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Researchers from Sapienza University collaborating with the Rome National Research Council and the Italian Institute of Technology (IIT) have demonstrated the spontaneous transition of glass from one form to another. The research project examined this process, which is solely due to the passage of time, and provided the first experimental evidence to unravel the properties of this transformation.

“We observed the arrangement and the microscopic movement of particles in the two glasses,” explains Roberta Angelini, Researcher at the Institute for Chemical and Physical Processes (IPCF-CNF), “by working on a colloidal clay dispersion and using advanced X-ray spectroscopic techniques with synchrotron light, thanks to the facilities at the European Synchrotron Radiation Facility (ESRF) of Grenoble.”

A greater understanding of the transition and the nature of the interactions between the two types of glass were uncovered by comparing the results and the simulations conducted by Emanuela Zaccarelli, a researcher at the CNR Institute of Complex Systems. Ms. Zaccarelli’s work confirmed the existence - at the experimental level - of a spontaneous transition between the two types of glass that differ in their soft composition, a fact that had never been ascertained before.

The dispersion of clay passes from a glass characterized by discoid particles that are distributed in a disorderly fashion to another glass in which the platelets arrange themselves at a given distance from a point to form a structure that resembles a castle of cards.

“In nature, these transitions from one state of matter to another are generally due to an external factor, such as temperature,” points out Angelini. “The novelty, here, is that to observe the transition we had to simply wait for time to pass,” underlines Giancarlo Ruocco from the Sapienza Department of Physics.

These studies mark how engineered and innovative materials should not overlook soft matter, the study of which is slowly making its way into modern physics that has demonstrated how there are many more exotic phases of matter– such as gel – than the standard solid, liquid, and gas”.

The dispersions of colloid clays, such as Laponite, appear in liquid, gel, and glass form and are used in technology as well as in everyday life, as thickeners in paint, cosmetics and house-cleaning products.

“These model systems are particularly interesting not only to basic research, but also to the many technological applications that our group has been studying for years,” concludes Barbara Ruzicka, IPCF-CNR researcher and coauthor of the study.

“What this study has explained is that the long-term stability of materials with disordered arrangements like glass depends on how the particles interact and position themselves at the microscopic level. Their control thus allows us to interact with the variable properties of the material and exploit it in a number of areas, ranging from nanotechnology to the transportation of pharmaceuticals.”

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