【摘要】：通過穩(wěn)恒電壓沉積法,在孔徑大小均勻、排列規(guī)整的氧化鋁模版(AAO)中制備出了La-Co合金納米管、納米線陣列。模版法制備納米材料具有易于控制其的長度、直徑、壁厚且成本低等優(yōu)點而被廣泛應用。利用X射線衍射儀(XRD)對制備好的樣品進行掃描檢測,從獲得的衍射圖譜中判定其晶體結構類型；掃描電子顯微鏡(SEM)、透射電子顯微鏡(TEM)是觀測樣品形貌特征、研究樣品幾何尺寸的主要手段,并且使用SEM自帶的能量彌散X射線譜儀(EDS)對納米管、納米線中化學元素及其含量進行定性、定量分析,而透射電鏡的選區(qū)電子衍射圖也將是分析樣品晶體結構的有效途經,最后利用振動樣品磁強計(VSM)對不同沉積條件下樣品磁性能的變化做了詳細的分析。結果顯示,由于納米管、納米線的晶粒隨機生長、無最優(yōu)取向而導致其顯示為非晶體結構。隨著沉積電壓絕對值的增大,其所含的Co元素都越來越少,對應的La含量比例則在升高,磁性能也越來越弱,磁各向異性也變得不再顯著,飽和磁場則是逐漸增大。對其磁性能進行研究,結果顯示易磁化軸方向垂直于納米管軸,而納米線其易磁化軸則是順著納米線軸。這是由于納米管、納米線具有不同的幾何結構致使決定易磁化軸方向的有效各向異性場不同而導致的,納米管中靜磁相互作用占據(jù)了主導地位,而納米線形狀各向異性與磁晶各向異性共同疊加占據(jù)了優(yōu)勢地位。在決定矯頑力大小的磁反轉模式中,納米管由平行軸線方向的卷曲反轉模式轉變?yōu)榇怪陛S線方向的橫向磁疇壁位移模式,而納米線的磁反轉模式則是單一的一致轉動。電沉積時外加方向垂直、平行于納米管軸、納米線軸的大小為1.5 T的外磁場。結果顯示外磁場對納米管的磁性能影響較為有限,這是由于非晶結構的納米管沒有很強的磁晶各向異性能而導致的。與納米管不同的是,納米線中有較多的、隨機排列的晶粒,在外磁場He的作用下晶粒的磁矩趨向于磁場方向,故而使得感應磁各向異性在平行于納米線軸方向有較大幅度的增加,平行方向的矯頑力也隨之大幅增加,有效各向異性變的更為明顯。垂直方向受限于有限的幾何直徑其感應磁各向異性能比較小,且方向垂直于納米線軸,它與靜磁相互作用相互疊加共同與形狀各向異性場競爭,進一步削弱了形狀各向異性場的優(yōu)勢,使得有效各向異性場進一步減小,矯頑力也相應變小。
[Abstract]:La-Co alloy nanotubes and nanowire arrays were prepared by steady voltage deposition method in (AAO) with uniform pore size and regular arrangement. The preparation of nanomaterials by template method has been widely used because of its advantages such as easy to control its length, diameter, wall thickness and low cost. X-ray diffractometer (XRD) was used to scan and detect the prepared samples, and the crystal structure types were determined from the obtained diffraction patterns. Scanning Electron microscope (SEM) (SEM), transmission electron microscope (TEM) is the main method to study the geometric size of the sample by observing the morphology of the sample, and using SEM's own energy dispersive X-ray spectrometer (EDS) to pair the nanotubes. The chemical elements and their contents in nanowires are qualitatively and quantitatively analyzed, and the selected electron diffraction patterns of transmission electron microscopy will also be an effective way to analyze the crystal structure of the samples. Finally, the variation of magnetic properties of samples under different deposition conditions is analyzed in detail by vibrating sample magnetometer (VSM). The results show that the nanowires exhibit amorphous structure due to their random growth and no optimal orientation. With the increase of the absolute value of deposition voltage, the content of Co elements decreases, the proportion of La content increases, the magnetic properties become weaker and weaker, the magnetic anisotropy becomes less significant, and the saturation magnetic field increases gradually. The results show that the magnetization axis is perpendicular to the nanotube axis, while the magnetization axis of the nanowires is along the nanowire axis. This is due to the difference in the effective anisotropy field which determines the direction of the magnetization axis due to the different geometric structure of nanotubes, in which the magnetostatic interaction dominates. The superposition of nanowire shape anisotropy and magnetocrystalline anisotropy is dominant. In the magnetic inversion mode, which determines the coercivity, the coiling inversion mode in parallel axis direction is changed into the transverse domain wall displacement mode in the vertical axis direction, while the magnetic inversion mode of the nanowire is a single uniform rotation mode. The external magnetic field of the nanowire is 1.5 T, parallel to the nanotube axis and perpendicular to the external direction during electrodeposition. The results show that the effect of external magnetic field on the magnetic properties of nanotubes is limited, which is due to the absence of strong magnetocrystalline anisotropy energy of amorphous nanotubes. Different from nanotubes, there are many randomly arranged grains in nanowires, and the magnetic moment of grain tends to the direction of magnetic field under the action of external magnetic field He. As a result, the induced magnetic anisotropy increases greatly in the direction parallel to the nanowires, and the coercivity in the parallel direction increases greatly, and the effective anisotropy becomes more obvious. The vertical direction is limited by the finite geometric diameter, and the inductive magnetic anisotropy energy is relatively small, and the direction is perpendicular to the nanowire, which superposes with the magnetostatic interaction and competes with the shape anisotropic field. The advantage of the shape anisotropic field is further weakened and the effective anisotropy field is further reduced and the coercivity is reduced accordingly.
【學位授予單位】：內蒙古大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TB383.1

【參考文獻】

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1 高鵬;楊中東;薛向欣;樊占國;;磁場影響下的電沉積[J];材料保護;2006年08期

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本文編號：2382928