Glass flow under high pressure

• Applicant: Linfeng Ding, Ph.D.
• Subject Area: Metallurgical, Thermal and Thermomechanical Treatment of Materials ; Glass, Ceramics and Derived Composites
• Term: from 2019 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 424980973

Supercooled liquids and glasses show intriguing universal behavior whose origins often remain poorly understood. The temperature dependence of glass flow (rheology) has been intensively studied; however, pressure also changes the properties and the behavior of glass, even at room temperature, a phenomenon that is not yet well understood. Moreover, the flow of silicate melts/glasses under pressure is a key parameter to understand the birth of our earth since geological silicate melts are continuously melted and solidified over millions of years. The research on the glass flow under high pressure is important both for the industrial applications and geological processes.The applicant received a three-year training within the network of European Union - Horizon 2020 - Marie Curie grant concerning the rheology and deformation of glass under extreme conditions. The previous work achieved significant impact on the understanding of necessary features in models describing the visco-elastic behavior of industrial silicate glasses at high pressure (comments from SCHOTT in the attachments). However, much work is still needed for a better understanding of the pressure dependence of glass flow.In this proposal, the applicant will extend the previous work and address the following question: (1) To what extent does the two-internal-parameter relaxation model (developed by the applicant and Dr. Kunisch) apply to other types of glasses? Can we derive a universal pressure dependence of glass transition and relaxation behavior for glass by applying the two-internal-parameter relaxation model? Or does a new model need to be derived to account for higher-order effects? (2) Since both thermal and pressure history will influence the glass flow behavior, what are the fundamental irreversible thermodynamics of glasses for various thermal/pressure histories? How well does the fictive pressure description capture the pressure history dependence of glass properties? (3) The MYEGA model (developed by the host) of viscosity has been tested on many types of glass-forming liquids with excellent accuracy, even at low temperature. Is it possible to extend the MYEGA model to fit the experimental pressure-viscosity results? Can we apply the extended MYEGA model to other types of glass-forming liquids? The preliminary viscosity-pressure results showed that the SCHOTT N-BK7 glass is depolymerized. Is it in agreement with the data from geoscience community?(4) What is the impact of glass composition on pressure dependence of viscosity? Is there an equivalent of "fragility" concerning pressure? To answer those questions, a specific research plan is proposed with three working packages. The results from the proposed work can be applied in the glass industry and this work will lead us to a better understanding of the flow behavior of the glass-forming liquids.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor John Mauro, Ph.D.