中文摘要
磁性流變液體（Magnetorheological Fluid 簡稱MR）在工業界之應用相當廣泛，尤其在機械、化工和光電工業上為最。其和傳統塑流液體之主要區分，在於外加一個磁場時，其流體的流變特性會隨著外加磁場強度大小及頻率而有顯著和快速的變化。
由理論及實驗得知，MR流體之流變率及黏度對外加磁場變化之效應均有規則可循，因為磁性流體中具有懸浮之納米級微磁粒子，在磁場作用下，會因磁場強度及顆粒極性等因素而產生聚集變化。當流體內部鐵磁納米粒子間之作用力和流體本身的流體動力相互競爭時，會影響其外在的流變率及黏阻係數等流變特性，形成可控的智慧型流體。
我們利用共沉法製備磁性超微粒子，並以油酸為界面活性劑，使其分散於煤油中，製成磁性流體。其間，調整製程參數以了解其在不同條件下，磁性超微粒子與界面活性劑間之作用方式，並探討其與磁性流體穩定性之關係。

ABSTRACT
The application of the magnetorheological fluid （MR）is very board, especially in the chemical, optical, and mechanical industry. In contrast to the traditional viscoplastic fluid, the flow characteristic of the MRF could be changed when applying an external magnetic field. The hydrodynamic mechanism altered when the strength of the applying field decreased or increased.
From the theoretical and experimental result, the shear rate and the viscosity of the MRF will follow a certain pattern or rule as the strength of the field changed. It could be explained as the magnetic property of the MRF changed due to the magnetic suspension particles added into the dispersed carrier fluid re-structured. The inter-particle force between these suspension ferro-particles will interact with the hydrodynamic force and compete with each other.
The co-precipitation method has been used to prepare the ultrafine particles, which are further dispersed in the kerosene with the surfactant oleic acid. Several process variables have been tried for testing the interaction between the ultrafine particles, and surfactants, and their effects on the stability of magnetic fluid have been also discussed.

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