Molecular Dynamics simulations of Amorphous Phase Separated glasses



ToughGlasses is a fundamental research project motivated by the need to improve and assess glasses mechanical durability over the long term. Glasses are integral parts our daily lives (buildings, cars, dishes…) along with being integral parts of heat resistant technologies, protection panels (smart phones, plasma screens…), low-carbon energies (protection for solar panels) and satellites in outer space to name a few. These systems and others undergo a variety of damage (consumer use, sand storms, external irradiations, high temperatures…) which can lead to premature failure and/or alterations of the physical and mechanical properties. Frequently, post-mortem failure studies reveal material flaws, which were propagating via Stress Corrosion Cracking (SCC). A recent question arriving in the field has been: Can the Amorphous Phase Separation (APS) of 𝑆𝑖𝑂2−𝐵2𝑂3−𝑁𝑎2𝑂 (SBN) glasses provide the necessary structure to enhanced SCC behavior? This thesis project aims is to fill this gap and to unravel the structural secrets behind enhanced SCC behavior.

The Ph.D. candidate will use Molecular Dynamics simulations to study the physical, mechanical and fracture properties of APS glasses. The primary objective of this study will be to use MD simulations to characterize the structure and failure properties of APS glasses and link these to experimental SCC studies. Hence, providing information on how the intrinsic structure of the glasses plays a role on the fracture properties of APS glasses. This method of comparing and contrasting MD simulations and stress corrosion cracking experiments has been used several time within our group to reach novel understandings of the process zone size versus the crack front velocity in pure silica (SiO2) and several SBN samples. Repeating this study for SBN APS glasses compositions will aid in the understanding of how the physical structure of glasses alters the mechanical properties.

In parallel, a second thesis student will conducting experimental studies (e.g. examining physical, mechanical and fracture properties) on the same materials. Both thesis students will work together in comparing and contrasting experimental and simulation results. Thus, researchers and developers will have a better idea of how small scale structural changes scale up to devise failures.

Logistically, the candidate will be advised by C. L. Rountree at CEA, SPEC. Simulations will be carried out on local HPC computers and eventually on large-scale HPC computers. The development of methods to form APS glasses will be part of the doctoral candidate’s tasks. Results concerning the structural formation of APS glasses will be compared and contrasted with thermodynamic results gathered from CALPHAD methods. In conclusion, the theme of this project is a comprehension of the source of the changes in the macroscopic property, and in particular how to control the stress corrosion cracking properties by varying the structure of glasses through Amorphous Phase Separation.


Some Relevant Publications

 “SiO2-Na2O-B2O3 density: A comparison of experiments, simulations, and theory.”  - M. Barlet, A. Kerrache, J-M Delaye, and C. L. Rountree Journal of Non-Crystalline Solids. 382, 32, (2013)

 "Hardness and Toughness of Sodium Borosilicate Glasses via Vicker's indentations” - M. Barlet, J-M. Delaye, T. Charpentier, M. Gennisson, D. Bonamy, T. Rouxel, C.L. Rountree Journal of Non-Crystalline Solids. 417–418:66-69 (June 2015).

 “Role of evaporation rate on the particle organization and crack patterns obtained by drying a colloidal layer” K. Piroird, V. Lazarus, G. Gauthier, A. Lesaine, D. Bonamy and C. L. Rountree  Europhysics Letters, 113:38002 (February 2016).

 “From network depolymerization to stress corrosion cracking in sodium-borosilicate glasses: Effect of the chemical composition.” M. Barlet, J.-M. Delaye, B. Boizot, D. Bonamy, R. Caraballo, S. Peuget and C. L. Rountree Journal of Non-Crystalline Solids. 450:174-184 (15 October 2016).


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