RUI: Field-Induced Phase Transitions in Monodisperse Ferrofluid Emulsions

[3321201] Liu本研究的目的是通过实验来探讨单分散铁磁流体（水包油）乳状液中富相的行为。外部施加的磁场在每个液滴中产生较大的磁矩，导致悬浮液从类流体相转变为更有序的相。不同的阶段可以由分离的链、有序的列或复杂的迷宫模式组成。将研究形成的结构的演变及其对各种关键参数的依赖。这些场诱导结构极大地改变了流体的粘度，使该系统成为磁流变流体的理想模型。因此，这些结果有望导致对这些系统迷人的相行为的新见解，并为制造具有基本新特性的技术上重要的材料提供指导。我们的建议是通过实验来探索浸入水中的小油滴悬浮液的相行为。每个油滴的大小都是均匀的，包含了数千个微小的漂浮磁铁。外部施加的磁场使微小的磁铁重新定向，这样每个液滴就像一个大磁铁。这使得液滴排列成链，使得悬浮液发生相变。这些由磁场引起的新相极大地改变了流体的粘度，将液体转变为固体，这可能会导致汽车或机器人关节控制主动控制减震器和离合器的发展。本研究旨在研究这些系统的场致结构变化，并为制造具有全新性能的重要技术材料提供指导。* * *

9321201 Liu The proposal is to explore experimentally the rich phase behavior exhibited in a confined colloidal suspension, a monodisperse ferrofluid (oil-in-water) emulsion. An externally applied magnetic field induces a large magnetic moment in each droplet, leading to a transition of the suspension from a fluid-like phase to a more ordered phase. The various phases can consist of separated chains, ordered columns, or a complex labyrinthine pattern. The evolution of the structure that forms, and its dependence on various key parameters will be investigated. These field induced structures dramatically modify the viscosity of the fluid, making this system an ideal model for a magnetorheological fluid. Thus the results are expected to lead to new insight into the fascinating phase behavior of these systems and provide guidelines for making technologically important materials with fundamentally new properties. %%% The proposal is to experimentally explore the phase behavior of a suspension of small droplets of oil immersed in water. Each oil droplet is uniform in size and contains thousands of tiny floating magnets. An externally applied magnetic field reorients the tiny magnets so that each droplet acts like a big magnet. This causes the droplets to line up into chains such that the suspension undergoes a phase transition. These field-induced new phases modify the viscosity of the fluid dramatically, turning the liquid into a solid which may lead to the development of actively controlled shock absorbers and clutches for cars or robotic joint controls. This research is to study the field-induced structural change of these systems and to provide guidelines for making technologically important materials with fundamentally new properties. ***