Paper Number
SC12
Session
Suspensions, Colloids, and Granular Materials
Title
Irreversible aggregation in sheared non-Brownian suspensions of clathrate hydrates
Presentation Date and Time
October 11, 2021 (Monday) 4:35
Track / Room
Track 5 / Ballroom 6
Authors
- Geri, Michela (Massachusetts Institute of Technology)
- McKinley, Gareth H. (Massachusetts Institute of Technology, Mechanical Engineering)
Author and Affiliation Lines
Michela Geri and Gareth H. McKinley
Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA
Speaker / Presenter
Geri, Michela
Keywords
theoretical methods; suspensions
Text of Abstract
In colloidal suspensions, the aggregation of constituent particles is governed primarily by the contrasting role of thermal agitation and shear break-up. The equilibrium between these two processes determines the effective volume fraction of dispersed solids and hence the suspension material properties, such as its shear viscosity. For non-Brownian particles thermal agitation is not important, but it has been shown that irreversible aggregation is possible for large shear rates (above 100 1/s) even for relatively dilute solutions (volume fractions as low as 10%). In these systems agglomeration is completely controlled by the shear rate, proving that hydrodynamic forces are important to overcome the energy barrier preventing particle aggregation. In this talk, we show that a different process can also control the irreversible aggregation in systems where bonds between particles are physically permanent due to sintering. The suspensions investigated are made of synthetic clathrate hydrate particles dispersed in an oil phase, which are of great interest to the energy sector due to their enormous potential for transport and storage of gases such as methane, carbon dioxide and hydrogen. First, we introduce a novel method that allows us to reliably control hydrate formation starting from a dispersion of ice particles. By monitoring the evolution of the suspension viscosity over time, we can follow the phase-transformation from ice to hydrate over many different water/ice volume fractions and applied shear rates. Combining rheometry and microscopy, we show that the hydrate particles inevitably sinter over time, producing an exponentially divergent viscosity increase that can be accelerated or delayed only by the addition of surface-active agents, which can control or even fully suppress the sintering process. We propose an analytical model that captures all our experimental observations with a single unknown parameter representing the characteristic sintering time.