Glasses, Optical Materials, and their Functional Applications: Current Issues in Science & Technology: Structure, Dynamics and Surface Reactivity of Glass Materials
Sponsored by: ACerS Glass & Optical Materials Division
Program Organizers: Jincheng Du, University of North Texas; S. K. Sundaram, Alfred University
Monday 8:00 AM
November 2, 2020
Room: Virtual Meeting Room 15
Location: MS&T Virtual
Session Chair: Jincheng Du, University of North Texas; Alastair Cormack, University of North Texas; Liping Huang, RPI
8:00 AM Invited
Surface Reactivity of Multi-component Glasses: Alastair Cormack1; 1Alfred University
The reactivity - or otherwise - of glasses depends largely, if not exclusively, on their surface structures. More specifically, it is the atomic level details which determine the interaction of environmental species, such as water, with the surfaces. These atomic level structural species are hard to determine in details from experimental studies, particularly in multi-component systems.In this presentation, we will discuss the structural moieties which have been found to occur on the surface in some multi-component silicate glasses from molecular dynamics computer simulations. Water molecules interacting with the glass surface create hydroxyl species, such as Si-OH or Al-OH, whose stability has been investigated as a function of time. The results suggest that local structural chemistry plays a key role in both the formation and stability of hydroxylated species.
8:30 AM
Melt-Quenching vs. Sol-gel vs. Vapor Deposition vs. Irradiation: Influence of the Synthesis Method on the Structure of SiO2: Zhe Wang1; Mathieu Bauchy1; 1University of California, Los Angeles
Glasses can be produced via several routes, e.g., melt-quenching, sol-gel, irradiation, or vapor deposition. However, it remains unclear to what extent the structure, thermodynamical stability, and properties of glasses depend on the method of synthesis. Here, based on reactive molecular dynamics simulations of glassy silica samples, we investigate the network topology and thermodynamics of glasses prepared by melt-quenching, sol-gel, irradiation, and vapor deposition. We show that, depending on the synthesis route, silica glasses can exhibit an allowable or forbidden structure, that is, which is accessible or not by melt-quenching. These results pave the way toward the development of new “forbidden” glasses with exotic structure and properties.
8:50 AM
Photo-elastic Confirmation of Fast Surface Relaxation of Silica Glasses in the Presence of Water: Bronson Hausmann1; Emily Aaldenberg1; Minoru Tomozawa1; 1Rensselaer Polytechnic Institute
Fast surface stress relaxation has been found to occur in oxide glasses at temperatures far below the glass transition in the presence of water. The observed relaxation has been suggested previously to explain various unresolved phenomena related to the mechanical strength of glass. Until now, residual stress has only been indirectly demonstrated through mechanical analysis or IR peak shift. In the present work, residual stress profiles were calculated using common photo-elastic techniques. Optical retardance profiles were measured in silica glass fibers following heat treatments under bending. Silica glass rods were also analyzed following relaxation under a constant angle of twist. Such retardance profiles were obtained along the width of the glass samples for various stress-treated times and temperatures in air. The stress profiles were found to agree with an error function relaxation profile, supporting the theory of a mechanism controlled by water diffusion.
9:10 AM
Enhanced Optical Nonlinearity in Bismuth Borosilicate Glass Dispersed with Eu2O3 Stabilized Gold Nanoparticles: Shivani Singla1; Venu Gopal Achanta2; Om Prakash Pandey1; Gopi Sharma3; 1Thapar Institute of Engineering & Technology; 2Tata Institute of Fundamental Research, Mumbai; 3Kanya Maha Vidyalaya, Jalandhar
The biggest challenge faced while incorporating metallic-nanoparticles inside a glass is to control their size, shape, and stability. A new approach to overcome this difficulty is presented here that consists of co-doping of Eu2O3 along with as-prepared gold nanoparticles (GNPs) to prepare GNPs dispersed bismuth borosilicate glass. Eu2O3 forms a covering around GNPs that prevents their loss due to evaporation and coagulation while preparing the glass. The surface plasmon resonance peak position related to GNPs is reported around 585nm. Intensity dependent nonlinear behavior of the glass is evidenced by open and closed aperture Z-scan technique from 1.9-14.38GW/cm fluence range. From open aperture Z-scan data, a switch between saturable absorption to two-photon absorption is observed with the increase in input fluence. The nonlinear refractive index of 4.7×10-18m/W is obtained for GNPs doped samples at a non-resonant wavelength of 800nm. Prepared glass sample is thermally stable and highly suitable for fiber drawing.
9:30 AM Invited
Elucidating Defect Behaviors and Lithium Ion Diffusion Mechanisms in Solid State Electrolytes from Atomistic Computer Simulations: Jincheng Du1; 1University of North Texas
The key of developing solid state electrolytes for energy storage and other applications is to improve the ionic conductivity, which is usually sluggish due to slow ion mobility in solids. I present our recent studies using atomistic simulations to elucidate the conduction mechanisms, particularly the effects of defects and composition on ion diffusion in LAGP, a NASCON-structured lithium solid-state electrolyte. Both static and dynamic simulations are used to study ion diffusion as a function of composition Li1+xAlxGe2-x(PO4)3(0.1≤ x≤0.8), where Al3+ ion gradually introduced to replace Ge4+ while Li+ ion added to balance the charge. Defect formation and association energetics and diffusion energy barriers from dynamics simulations are combined with structural characterizations around the defect sites. Tracking ion mobility at atomic scale is used to monitor ion diffusion pathways. The information is used to develop into diffusion mechanisms and strategy to design better solid-state electrolytes.
10:00 AM
Relative Roles of O and Si in Crack Nucleation and Propagation Mechanisms in Amorphous Silica: Zubaer Hossain1; 1University of Delaware
The mechanical behavior of glass has been the subject of active research for many decades. Yet the underlying mechanisms that govern crack nucleation and propagation in glass remains less understood. In this talk, we will present an atomistic scale understanding of the role of Si and O atoms in governing the crack nucleation and propagation criteria in amorphous silica. Our results suggest that both crack nucleation and propagation are governed by chainlike nanoscale virial stress-fibers formed by an intricate mixture of Si and O atoms. Additionally, the virial stress fields in the domain are highly heterogeneous and species-dependent -- and the O and Si atoms play fundamentally distinct roles throughout the deformation process. With increased loading, heterogeneity in virial stress for the Si atoms goes up, whereas for the O atoms it goes down.