Browsing by Author "Dong, Minzhao"

Now showing 1 - 1 of 1
  • Thumbnail Image
    ItemOpen Access
    Acoustic Destabilization of Asphaltene Laden Interfaces: A Micromechanical Investigation
    (2023-03-08) Khalesi Moghaddam, Razie; Natale, Giovanniantonio; Yarranton, Harvey W; Dong, Minzhao; Benneker, Anne; Kantzas, Apostolos; Zeng, Hangbo
    Fluid-fluid interfaces are important in both natural and industrial settings, and their mechanical characteristics play a crucial role in the systems’ stability. To assess the local rheology of fluid-fluid interfaces, the Brownian motion of probe particles at the interface was analyzed. Using this method, the micromechanical characteristics of the interface and map of interfacial heterogeneity were calculated from the local microrheological measurements. The potential of the proposed methodology was illustrated by examining the stabilizing mechanisms of asphaltene-laden interfaces. Asphaltenes are the heaviest components of crude oils that adsorb on water/oil interfaces to form viscoelastic films. Local rheological measurements were used to characterize the viscoelastic behavior of asphaltene-laden water/oil interfaces prepared from fractionated asphaltenes. It was found that the interfacially active fraction of asphaltenes formed more rigid films at the interface more quickly and led to more stable emulsions than the partially active fraction. The ultrasonic treatment impact on the film properties and emulsion stability was also investigated. Asphaltene-coated silica particles in water were treated with an ultrasonic field, and the thickness of the coating on the particle was calculated using interaction force profiles measured by optical tweezers. The coating thickness decreased with increasing the ultrasound irradiation duration. The ultrasonic treatment led to demulsification in asphaltene-stabilized water-in-oil emulsions, suggesting that the disruption of the asphaltene coating observed in the force measurement experiments may play a role in the demulsification process. To strengthen the link between emulsion stability and ultrasound perturbation, the microrheology apparatus was adapted to generate an in-situ ultrasound field with adjustable voltages and frequencies. Asphaltene-laden water-toluene flat interfaces were treated with ultrasonic fields over a range of voltages and frequencies. The application of different ultrasonic fields revealed different microrheology regimes, and in the regime where interfacial cavitation occurred, a significant disruption of the asphaltene interfacial film was detected. Emulsion stability was found to decrease significantly in this regime. Overall, this thesis demonstrated that interfacial microrheology is an important technique to explore the local mechanical properties of interfaces between fluids, and in particular, asphaltene-laden interfaces. Additionally, it was shown under what conditions ultrasonic perturbation could induce coalescence in asphaltene-stabilized emulsions.