以延伸X光吸收精細結構探討銅鎳合金原子結構與其相對含量之關聯性

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Title:	以延伸X光吸收精細結構探討銅鎳合金原子結構與其相對含量之關聯性
Other Titles:	Effect of relative concentration on the local structure in Cu-Ni alloys studied by extended X-ray absorption fine structure
Authors:	高嘉尹;Kao, Jia-Yin
Contributors:	淡江大學物理學系碩士班張經霖
Keywords:	銅鎳合金;熱電材料;EXAFS;Copper-nickel alloy
Date:	2016
Issue Date:	2017-08-24 23:38:15 (UTC+8)
Abstract:	我們以延伸X光吸收光譜精細結構 (EXAFS)對面心立方體Cu1-xNix (x=0.2、0.3、0.4、0.5) 合金進行原子結構分析。由於CuNi合金為無序的置換型固溶體，Cu原子和Ni原子在排列上會有互換情形，所以其原子結構較為複雜。從Cu K-edge EXAFS的傅立葉轉換強度觀察到，在距離2.51Å處有第一配位峰，此峰是Cu-Ni鍵結；也在Ni K-edge EXAFS的傅立葉轉換強度分布觀察到，在距離2.50Å處有第一配位峰，此峰為Ni-Cu鍵結。隨著Ni濃度上升，大致上其強度下降，半高寬變寬，鍵長變長。更進一步，我們做擬合曲線得到鍵長、配位數、Debye-Waller factor等數據進行討論，發現鍵長比為Cu-Cu鍵結大於Cu-Ni鍵結大於Ni-Ni鍵結，而且隨Ni濃度上升，Cu-Cu、Cu-Ni、Ni-Ni鍵長下降，而配位數隨著Ni濃度增加，Cu-Cu配位數會下降，Cu-Ni上升，Ni-Cu配位數會下降，Ni-Ni上升，與以Ni濃度比計算的配位數相差越來越大，推測是因為Cu原子有聚集情形產生。比較熱導率與Cu-Cu、Cu-Ni、Ni-Ni的Debye-Waller factor發現聲子熱導對熱導率影響不大。 We have performed extended X-ray absorption fine structure (EXAFS) measurements to investigate the variation of local atomic structures of a series of Cu1-xNix (x = 0.2、0.3、0.4、0.5) alloy. Since CuNi alloy disordered substitutional solid solution, the local structure is more complicated. According to the curve fitting of EXAFS , we observed a decrese of bond lengths including RCu-Cu, RCu-Ni, and RNi-Ni with the increase of the nickel concentration . Among them, RCu-Cu、RCu-Ni、RNi-Ni are about 2.55Å、2.53Å、2.50Å. With increasing concentration of nickel, Cu-Cu coordination number (called CNCu-Cu) decrease. However, CNCu-Ni and CNNi-Ni increase. We Compare the coordination number of nickel concentration ratio calculated (containing CNcCu-Cu, CNcCu-Ni, CNcNi-Ni) with CNCu-Cu, CNCu-Ni, and CNNi-Ni. The difference between CNcCu-Cu and CNCu-Cu increases as concentration of nickel increases. Nevertheless, the difference between CNcCu-Ni and CNCu-Ni decreases as concentration of nickel increases. For this result, Cu atoms have gathered. Comparison of thermal conductivity and Cu-Cu, Cu-Ni, Ni-Ni of the Debye-Waller factor found that the phonon thermal conductivity has a little influence of the thermal conductivity .
Appears in Collections:	[Graduate Institute & Department of Physics] Thesis

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