以電子分佈探討5 nm銀顆粒之熱縮現象

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題名:	以電子分佈探討5 nm銀顆粒之熱縮現象
作者:	王冠儒;Wang, Kuan-Ju
貢獻者:	物理學系
關鍵詞:	奈米顆粒;負熱膨漲;電子分佈圖;nanoparticle;negative thermal expansion;charge distribution map
日期:	2020-07-06
上傳時間:	2020-09-02 15:46:06 (UTC+8)
出版者:	國立中央大學
摘要:	多數物質會隨著溫度上升產生熱膨脹，而物質的負熱膨脹現象即所謂熱縮現象卻也不罕見，但這現象多出自於非均向性結構，而均向性結構的熱縮也往往伴隨結構的改變，最廣為人知便是液態水在4°C以下的熱縮現象，而這熱縮現象也是由於水分子鍵角改變所致。在本實驗室2002年論文中亦曾發現4 nm金顆粒的熱縮現象[1]，並用量子尺度效應解釋，而在之後楊仲準教授亦在2006實驗中發現Ag奈米顆粒(NPs)的熱縮現象。在本論文中，將使用楊仲準教授所做變溫X光繞射數據做晶格常數以及電子分佈分析，首先我們在粒徑小至5 nm Ag NPs發現在10至60 K熱縮現象，並且在5 nm 與9 nm Ag NPs中皆發現異常熱膨脹。論文下半部分我計算電子分佈的變化以觀察熱縮現象發生時相應的變化，發現5 nm Ag NPs隨熱縮發生電子向外層轉移，並在轉變為熱膨脹後回到Ag離子內層的現象。 ;Most substances will thermally expand with increasing temperature, but the phenomenon of negative thermal expansion of substances, the so-called thermal contraction, is not uncommon. This phenomenon is mostly caused by anisotropic structures, and the thermal contraction of isotropic structures is often accompanied by structural change. The most widely known thermal contraction is the thermal contraction of liquid water below 4°C, which is also due to the change in the bond angle of water molecules. In the 2002 paper of this laboratory, the thermal contraction of 4 nm gold nanoparticles was also found [1], which was explained by the quantum scale effect. Later, the Professor Chun-Chuen Yang also discovered the thermal contraction of silver nanoparticles in the 2006 experiment. In this thesis, the temperature define X-ray diffraction data made by Professor Chun-Chuen Yang will be used for lattice constant and electron distribution analysis. First, we found that the thermal contraction at 10 to 60 K in Ag NPs with a particle size as small as 5 nm, and the abnormal thermal expansion in both 5 nm and 9 nm samples . In the second half of the thesis, I calculated the changes of the electron distribution to observe the corresponding changes when thermal contraction happened, and found that 5 nm Ag NPs transfer electrons to the outer layer when thermal contraction happened then returns to the inner layer of the Ag ion after thermal expansion.
顯示於類別:	[物理研究所] 博碩士論文

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