Structures along the boundaries in the magnetic fluid films under perpendicular magnetic fields

Autor: 黃濱洲
Rok vydání: 2003
Druh dokumentu: 學位論文 ; thesis
Popis: 91
The purpose of this research is to investigate the properties of ordered structure on the magnetic fluid, a type of nano-materials, and to evaluate the possibility to utilize such properties to the application photonic crystals. The magnetic nano-particles were synthesized by the co-precipitation method. By the aid of the surfactant, the magnetic nano-particles stably dispersed in the liquid due to the action of the surfactant. The sizes of the nano-particles in the magnetic fluid are around 100Å (1Å=10-10m). The formation and evolution of the ordered structure of magnetic columns in the magnetic fluid film under perpendicular magnetic fields at the given sweep rate dH/dt were observed by using a CCD camera. It was found that the structure of magnetic columns evolved to an ordered hexagonal pattern not only within the magnetic fluid film but also along the edge of the cell. Furthermore, the interactions between magnetic columns varied by changing (1) the sweep rate dH/dt, (2) magnetic field strength H, and (3) the width of the cell. When the sweep rate dH/dt was higher, the distance between magnetic columns becomes smaller. Also, when the field strength H was higher, the structural pattern would evolve from an ordered structure to a transition state in the present of the influence of the boundary condition, and finally back to another ordered state. Finally, when the cell became wider, the boundary effect is reduced. For the reasons mentioned above, the interactions between magnetic columns may be controlled by means of the sweep rate dH/dt, magnetic field strength and the width of the cell. In addition, the results also proves the possibilities of potential applications of using ordered structure of magnetic fluids as a vehicle in photonic crystals.
Databáze: Networked Digital Library of Theses & Dissertations
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