Paper Number
GG21 

Session
Out of Equilibrium Systems: Gels and Glasses

Title
Mechanical spectroscopy of alumino-silicate hydrogels during gelation

Presentation Date and Time
October 22, 2019 (Tuesday) 1:55

Track / Room
Track 7 / Room 306C

Authors (Click on name to view author profile)

1. Keshavarz, Bavand (MIT, Mechanical Engineering)
2. Poulesquen, Arnaud (CEA, France)
3. Gomes-Rodriguez, Donatien (CEA, France)
4. Champenois, Jean-Baptiste (CEA, France)
5. Geri, Michela (MIT, Mechanical Engineering)
6. Owens, Crystal E. (Massachusetts Institute of Technology)
7. Divoux, Thibaut (MIT,CNRS)
8. McKinley, Gareth H. (Massachusetts Institute of Technology, Department of Mechanical Engineering)

Author and Affiliation Lines (in printed abstract book)
Bavand Keshavarz¹, Arnaud Poulesquen², Donatien Gomes-Rodriguez², Jean-Baptiste Champenois², Michela Geri¹, Crystal E. Owens¹, Thibaut Divoux¹, and Gareth H. McKinley^1
1Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA; ²CEA, France, Bagnols-sur-Cèze, France

Speaker / Presenter 
Keshavarz, Bavand

Text of Abstract
Alumino-silicate hydrogels are widely used in different industrial applications. These gels are simply made from a class of alumino-silicate materials known as zeolite precursors. Mixing two solutions of sodium aluminate and an alkali-silicate together initiates a series of condensation and bond-breaking reactions leading to a relatively rapid process of gel formation. The rheological behavior of the mature gels that form after gelation show interesting power law signatures in the linear viscoelastic regime over a wide range of timescales and frequencies. However, due to the rapidly mutating nature of these gels in the vicinity of the gelation point, little is known about the temporal evolution of the mechanical properties during the gelation/curing process. We use the Optimally Windowed Chirp (OWCh) technique [1] to obtain the time- and frequency-resolved response from the material every three seconds. This novel method enables us to reduce the mutation number of the system substantially and obtain fast and precise measurements. Parallel to mechanical spectroscopy we also study the structural evolution of these gels using time-resolved SAXS/WAXS measurements. Using these methods we can explore the mechanical/structural evolution of the gel over a wide range of time and length scales. These results enable us to understand connections between the structure and power-law rheology observed in the mature gel and more importantly provide an accurate spatio-temporal record of the timescales and elasticity of the evolving network. Reference: [1] Geri, M.; Keshavarz, B.; Divoux, T.; Clasen, C.; Curtis, D. J.; McKinley, G. H. Phys. Rev. X 2018, 8 (4), 41042.