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Colloids at fluid interfaces :Structure, dynamics, and droplet stability

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Colloids at fluid interfaces :
其他題名:	Structure, dynamics, and droplet stability
作者:	Stancik, Edward Jay.
面頁冊數:	133 p.
附註:	Adviser: Gerald G. Fuller.
附註:	Source: Dissertation Abstracts International, Volume: 65-04, Section: B, page: 1986.
Contained By:	Dissertation Abstracts International65-04B.
標題:	Engineering, Chemical.
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3128480
ISBN:	0496757423

Colloids at fluid interfaces :Structure, dynamics, and droplet stability
Stancik, Edward Jay.

Colloids at fluid interfaces :Structure, dynamics, and droplet stability [electronic resource] - 133 p.

Adviser: Gerald G. Fuller.

Thesis (Ph.D.)--Stanford University, 2004.

For both naturally occurring and commercially developed emulsions, colloidal particles have proven to be effective stabilizers against droplet coalescence and the macroscopic phase separation that necessarily results. A dominant role in the stabilization mechanism is played by the Marangoni stresses that arise due to interfacial particle concentration gradients, which in turn develop through hydrodynamic coupling with the fluid draining from between approaching droplets. In an attempt to elucidate these processes, the effects of fundamental flows on the structure and dynamics of monodisperse spherical polystyrene particles adsorbed to the decane-water interface were investigated. A competition between the forces arising from particle interactions and those due to the applied flow field leads to two distinct regimes of particle behavior governed by interfacial concentration and flow rate. At low concentrations or high flow rates, hydrodynamic forces dominate the system and cause the particles to follow expected streamlines. For the contrasting conditions, interparticle forces gain importance and lead to collective flow behavior amongst the particles. Such behavior is exhibited by individual particles maintaining their lattice spacing relative to one another within larger domains that are forced to shift or rotate in the flow field.

ISBN: 0496757423Subjects--Topical Terms:

226989
Engineering, Chemical.

Colloids at fluid interfaces :Structure, dynamics, and droplet stability
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520 # $a For both naturally occurring and commercially developed emulsions, colloidal particles have proven to be effective stabilizers against droplet coalescence and the macroscopic phase separation that necessarily results. A dominant role in the stabilization mechanism is played by the Marangoni stresses that arise due to interfacial particle concentration gradients, which in turn develop through hydrodynamic coupling with the fluid draining from between approaching droplets. In an attempt to elucidate these processes, the effects of fundamental flows on the structure and dynamics of monodisperse spherical polystyrene particles adsorbed to the decane-water interface were investigated. A competition between the forces arising from particle interactions and those due to the applied flow field leads to two distinct regimes of particle behavior governed by interfacial concentration and flow rate. At low concentrations or high flow rates, hydrodynamic forces dominate the system and cause the particles to follow expected streamlines. For the contrasting conditions, interparticle forces gain importance and lead to collective flow behavior amongst the particles. Such behavior is exhibited by individual particles maintaining their lattice spacing relative to one another within larger domains that are forced to shift or rotate in the flow field.
520 # $a In a separate study, but again with the purpose of developing a better understanding of particle stabilization mechanisms, the dynamics of colloids adsorbed to both water and oil droplets were observed as these droplets were brought into contact with colloid-laden, planar, oil-water interfaces. These model systems, representing water-in-oil and oil-in-water emulsions respectively, revealed striking differences in the formation of ring and disk mesostructures by the particles as they serve to stabilize the approaching interfaces in the two geometries. Furthermore, under the proper wetting conditions, the particles were able to create adhesion between two separated bulk fluid phases by adopting a bridging geometry that afforded stability to the intervening thin film of fluid. Insights into this rich behavior lead not only to a better understanding of so-called Pickering emulsions, but also to a novel method for determining the three-phase contact angle at which particles reside at fluid interfaces.
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