Atomic Mechanisms of Plastic Deformation in Calcium Aluminosilicate Glasses

Abstract

Silicate glass has been used by mankind for thousands of years; however in the 19th century, glass transformed from a material used for its beauty and ability to hold liquids to an engineered material enabling technological advances of the modern era. Silicate glasses have enabled modern technologies such as electronic displays, optical telecommunications, and advanced optical systems. But the fracture of silicate glass components is often the lead cause of failure in glass-containing devices which prevents their use in a wider range of applications. In order to engineer glasses with superior mechanical durability, it is imperative to know the origins of fracture and the behaviors that influence it. Plastic deformation in glass has been observed to occur prior to fracture, and it has been shown to control the origin of flaws (which influences crack formation) and the evolution of stress (which influences crack propagation) under a mechanical contact. Plastic deformation behavior can be classified into two main categories: macroscopic behavior and morphology and atomic deformation mechanisms. Since the vast majority of work to understand plastic deformation has centered on macroscopic behavior, knowledge of atomic mechanisms of plastic deformation remains extremely limited. The aim of the work presented in this dissertation was to investigate atomic mechanisms of plastic deformation in silicate glasses by leveraging the combined advantages of experimental and computation strategies to observe atomic level structural changes due to plastic deformation while circumventing the downfalls of both techniques. Specifically, Raman spectra of indentations are analyzed to infer atomic mechanisms of deformation from the limited number structural changes observable using Raman spectroscopy. Structural analysis of simulated glass structures exposes every conceivable structural change with deformation while it is limited by the accuracy of physics used to create the structures. The unique combination of these two techniques confirms the presence of experimentally observable structural changes and explains their broader structural implications to create a comprehensive understanding of atomic mechanisms of plastic deformation. These mechanisms form the foundation for further study of atomic mechanisms of plastic deformation which contribute to the broader understanding of plastic deformation, a critical step in the pursuit of fracture and scratch resistant glasses.