GOALI: Atomistic Understanding of Non-Newtonian Flow and Related Phenomena in Chalcogenide Glass-Forming Liquids

University Of California-Davis, Davis CA

Investigators

Abstract

NON-TECHNICAL DESCRIPTION: Chalcogenide glasses are an important class of materials that have found wide-ranging applications in the areas of photonics, telecommunication, optical memory storage, photovoltaics and environmental remote sensing. However, surprisingly, little is known regarding the flow response of the parent melts or liquids from which these glasses are derived, especially when these melts are subjected to large deformation rates during various industrial forming processes, including but not limited to molding, extrusion, embossing and fiber drawing. This project aims to investigate the mechanistic relationships between deformation rate and the flow behavior at the atomic scale in a variety of chalcogenide glasses and liquids for the first time, using a variety of cutting-edge characterization techniques. This fundamental understanding may enable the identification of chalcogenide glasses suitable for low-temperature polymer-forming processes, thereby permitting their widespread application in transformative technologies with strong societal impact. Scientifically, this work impacts materials science, physical chemistry and solid state physics. The interdisciplinary nature of this work transfers knowledge between fields and provides the students with unique opportunities for intellectual growth. The impact of this research in education and outreach is in three major areas: (1) participation by students, (2) active collaboration with industry, and (3) dissemination of knowledge, especially of glass science and technology, to the broader scientific community. The research activities provide the core of special topics courses that are offered to students in materials science, chemistry and other related fields; contribute to campus programs for women and minority students; and to recruiting promising students from underrepresented and economically disadvantaged groups. TECHNICAL DETAILS: The non-Newtonian flow response of a supercooled glass-forming liquid, when it is driven out of equilibrium via mechanical deformation, is intimately linked to its viability for various processing techniques and is of key significance in industry in controlling and optimizing the corresponding processing parameters. This GOALI project brings together investigators with complementary expertise and common interests from the University of California at Davis (Sen) and from Corning, Incorporated (Aitken) to address the connections between the atomistic and the macroscopic aspects of the non-Newtonian flow and related phenomena in chalcogenide glass-forming liquids in the systems Ge-As-Se and Ge-P-Se using a powerful combination of state-of-the-art rheometric measurements and structural and dynamical characterization with high-resolution nuclear magnetic resonance (NMR) and Raman spectroscopy, differential scanning calorimetry and small-angle X-ray scattering. Predictive atomistic models of structure-deformation-viscous flow relationships, built on the basis of the results obtained in this project, may ultimately enable the use of chalcogenide glasses in a wide range of low-temperature continuous forming processes, thereby making these materials viable for widespread applications in modern technologies ranging from photonics and telecommunication to remote sensing. The focus of this project, namely how and why, the dynamic and thermodynamic aspects of strain-induced rearrangements of the atomic structure control the shear thinning behavior and related phenomena in chalcogenide glass-forming liquids is in itself crosscutting materials research. The breadth, flexibility and interdisciplinary nature of this project prepares students with powerful experimental skills and research experience in both academic and industrial settings that may open up many opportunities for their future careers. This project also enriches the graduate education and training experience through numerous scientific dialogues and interactions between the collaborating scientists and participating students.