摘要

在本研究中，我們針對三種可能改變CeO2空心球（H-CeO2）鐵磁性強度的因素進行探討。 H-CeO2採用噴霧熱解法製備。首先， H-CeO2與不同濃度的硝酸溶液進行混合，經不同反應時間，使中空球的表面狀態形成不同程度的改變。根據SEM圖像，顆粒會被酸性溶液破壞。粒度分佈變寬。當HNO3的濃度為2.14 M並且反應為15分鐘時，磁飽和度增加至0.01emu / g，此數值是未經表面處理的中空球的十倍。
第二部分，我們利用抽氣過濾的方式H-CeO2中大於800 nm的部分進行收集。結果發現大於800nm的球體其飽和磁化強度較原始樣品高，其值為0.004 emu / g。但是，若將中空球先以HNO3進行表面處理，則尺寸效應則相反，較大顆粒的中空球其飽和磁化強度降低至0.0008 emu / g。
在最後一部分，我們將三種類型的H-CeO2進行壓碎以探討形狀效應，第一種為原始的H-CeO2，第二種為尺寸大於800nm的大尺寸中空球，第三種則先以HNO3進行表面處理。結果指出，將原始樣品及大尺寸中空球的中空形狀破壞後，其飽和磁化強度上升。但是，若中空球事先經過處理，則形狀效應會受到影響。

ABSTRACT

In this study, three possible factors which may change the strength of ferromagnetism of CeO2 hollow spheres (H-CeO2) were investigated. H-CeO2 was prepared by spray pyrolysis method. In the first, surface effect was discussed. H-CeO2 reacted with nitric acid solution at different concentration and for different time to change the surface state of spheres. According to the SEM image, the particles got damaged and destroyed by acid solution. The particle size distribution became wider. As the concentration of HNO3 was 2.14M and the reaction was 15 mins, the magnetic saturation was increased to 0.01 emu/g, which was ten times greater than the as-prepared spheres.
In the second part, with the application of filtration process, H-CeO2 was divided into two parts: original ones and the ones larger than 800 nm. It is found that the magnetic saturation was higher of large spheres. The value of large H-CeO2 was 0.004 emu/g. However, in HNO3 treated H-CeO2, the effect of size was different. The magnetic saturation of the large ones was decreased to 0.0008 emu/g.
In the last part, H-CeO2 was crushed to change the shape. The crush treatment was done on three types of samples: as-prepared H-CeO2, large H-CeO2, and the HNO3 treated H-CeO2. It is demonstrated that after crush treatment, the magnetic saturation was increased for the former two. But it was decreased for the HNO3 treated ones.

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