Liquid stone all seminars

Date: Monday, April 8, 2019 Time: 3:00-4:00 pm Place: 1-131

Romain Dupuis - Postdoctoral researcher (MIT)
E-mail: rdupuis@mit.edu / romaindupuis.com

Abstract: The formation of gels is a complex issue that has to be resolved to investigate manifold synthetic and natural materials (cement, geomaterials for radioactive waste sealing, minerals). Gels are amorphous phases that contain water. Therefore the gelation depends on pH of the initial solution, water to silicon ratio or ionic concentration. Simulations can provide detailed information on the structuration of gels and on their mechanical properties. We have recently developed a method to reproduce efficiently the formation of pure silica gels. The key features are in good agreement with experimental data. Being able to simulate the structural, mechanical and dynamical properties of gels have far-reaching consequences to improve the synthetization of materials and to lengthen their lifetime. We will present new results deriving from the simulation of pure silica gels, alkali-silica gels and calcium-silica gels. Using cost-efficient methods, we are now able to play at will with the chemical properties. In this work, we are interested in the interplay of structural properties and mechanical properties that can lead to the loss of durability of materials. For instance, we modified the water to silicon ratio to observe the restructuration of gels. We noted a passivation effect that protects dense gels from dissolving, due to the formation of silicate cages, which cancels out when pH is high. Knowing the gels structure will help us to go to larger scales simulations and investigate the interaction between gels, solutions and solids.