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  • 學位論文

以化學方法合成鐵鉑合金奈米微粒與磁性質之研究

Study on the synthesis of FePt nanoparticles and magnetic properties

指導教授 : 賴志煌

摘要


磁性奈米微粒近年來受到廣大的關注,在生醫方面,例如:藥物投遞(drug delivery)、核磁共振造影(MRI),或是在記錄媒體上,廣泛被應用。其中在記錄媒體方面,鐵鉑合金(FePt)最受矚目,因其具有高異向性,可解決超順磁所產生的問題。所謂超順磁現象,意旨當粒子尺寸趨近奈米尺寸時,磁矩易受到熱擾動的影響。 鐵鉑奈米微粒的合成目前遇到最大瓶頸在於,其尺寸不易增大。再者,當尺寸增大時,鐵和鉑的比例會受到尺寸的影響而形成鉑偏多的鐵鉑微粒。然而,鐵鉑合金的磁性質易受到成分的影響,當鐵和鉑的比例偏離一比一時,矯頑場(Hc)會有很明顯的下降。 論文主軸是以化學方法合成鐵鉑合金奈米微粒,藉由調變合成參數,例如:界面活性劑、加熱時間以及加熱溫度,來改變微粒尺寸以及成分。並探討這些合成參數對尺寸和成分的影響。再藉由後退火處理,使鐵鉑合金產生序化。我們採用鐵鉑合金微粒和食鹽混合來防止奈米微粒在高溫熱處理下產生聚集。從實驗結果可知,食鹽可作為阻絕層,有效止奈米微粒在高溫下的聚集。最後,將探討FePt和FePt3之間的交互耦合作用在磁性質上的特殊性。

並列摘要


The larger size of FePt nanoparticles is a big challenge in recent years. In my work, controlling size distribution and composition of FePt nanoparticles by thermodecomposition method is the main topic. As-synthesized FePt nanoparticles are chemically disordered and post-annealing is required to obtain chemically ordered FePt. Salt matrix-aid effect in annealing steps of as-synthesized FePt nanoparticles and the magnetic properties of annealed FePt alloy are studied. The exchange coupling phenomenon between FePt (FM) and FePt3 (AFM) nanoparticles was demonstrated and discussed in the final section.

參考文獻


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