本文選題：氧化鐵 + 納米環(huán)　； 參考：《寧波大學(xué)》2015年碩士論文

【摘要】：氧化鐵納米材料吸引越來越多的研究目光,主要是由于其在廣泛且重要的應(yīng)用。納米氧化鐵的各種性能與氧化鐵納米結(jié)構(gòu)的形貌有著重要的聯(lián)系。本論文中,選取了兩種重要的α-Fe2O3納米結(jié)構(gòu)作為研究對象。通過水熱法合成了不同壁厚的α-Fe2O3單晶納米環(huán)及納米管,并利用綜合物性測量系統(tǒng)對樣品的磁學(xué)性能進(jìn)行了研究。同時也對α-Fe2O3納米環(huán)在高性能鋰離子電池負(fù)極材料上的應(yīng)用作了系統(tǒng)的研究。本文的主要研究成果如下:(1)我們通過水熱法合成了單晶α-Fe2O3納米環(huán)和納米管。通過高分辨透射電子顯微鏡和選區(qū)電子衍射發(fā)現(xiàn)納米環(huán)和納米管的軸向方向平行于晶體c軸。磁性測量結(jié)果表明,單晶納米環(huán)在210K處存在一個一級Morin相變,而單晶納米管中沒有觀測這種相變。目前的實(shí)驗(yàn)結(jié)果表明,Morin相變對納米結(jié)構(gòu)的形狀有很強(qiáng)烈地依賴性。Morin相變對納米結(jié)構(gòu)形狀的依賴性可以通過垂直和平行于晶體的c軸的正與負(fù)的表面各向異性常數(shù)來解釋。(2)我們測量了α-Fe2O3不同納米結(jié)構(gòu)的從室溫到980K之間的磁學(xué)性能。首先在高真空(9.5×10-6 Torr)下通過920K之前的磁學(xué)性能的測量來確定不同納米結(jié)構(gòu)的熱穩(wěn)定性。實(shí)驗(yàn)結(jié)果發(fā)現(xiàn),高溫高真空下存在一個α-Fe2O3向Fe3O4的相變過程,而且這個轉(zhuǎn)變過程受納米結(jié)構(gòu)形狀的強(qiáng)烈影響。實(shí)驗(yàn)數(shù)據(jù)表明,這種相變主要發(fā)生在晶體(001)表面。由于納米環(huán)和納米管結(jié)構(gòu)的高的熱穩(wěn)定性,我們可以準(zhǔn)確的測量到它們的Néel溫度。納米環(huán)與納米管的Néel溫度隨納米環(huán)與管的壁厚的減小而下降,符合Néel溫度的二維有限尺寸效應(yīng)。(3)我們通過一種簡單的兩步法成功制備了α-Fe2O3@C納米環(huán)。與純α-Fe2O3電極材料相比,α-Fe2O3@C納米環(huán)表現(xiàn)出更高的容量以及更好的充放電倍率性能。更重要的是,α-Fe2O3@C納米環(huán)具有更好的循環(huán)性能(在1000 m Ag-1的電流下循環(huán)充放電160次后仍保有815 m Ahg-1的容量)。由于α-Fe2O3@C納米環(huán)的獨(dú)特結(jié)構(gòu)及優(yōu)異的電化學(xué)性能,α-Fe2O3@C納米環(huán)可以作為高性能鋰離子電池極有前途的一種負(fù)極材料。同時,也可以以這種環(huán)狀結(jié)構(gòu)作為前驅(qū)體合成其它高性能的Fe2O3基鋰離子電池負(fù)極材料。
[Abstract]:Iron oxide nanomaterials attract more and more attention, mainly due to their wide and important applications. The properties of nanometer iron oxide are closely related to the morphology of iron oxide nanostructure. In this thesis, two important 偽-Fe _ 2O _ 3 nanostructures are selected as the research object. 偽 -Fe _ 2O _ 3 nanocrystalline rings and nanotubes with different wall thickness were synthesized by hydrothermal method. The magnetic properties of the samples were studied by a comprehensive physical property measurement system. At the same time, the application of 偽 -Fe _ 2O _ 3 nanocyclic in the anode material of high performance lithium ion battery has been systematically studied. The main results of this paper are as follows: (1) single crystal 偽 -Fe _ 2O _ 3 nanorings and nanotubes have been synthesized by hydrothermal method. By means of high resolution transmission electron microscopy and selected area electron diffraction, the axial direction of nanospheres and nanotubes was found to be parallel to the c axis of the crystal. The magnetic measurements show that there is a first-order Morin phase transition at 210K in the monocrystalline nanocrystalline ring, but no such phase transition is observed in the single crystal nanotubes. The present experimental results show that the Morin phase transition is strongly dependent on the shape of the nanostructure. The dependence of the Morin phase transition on the shape of the nanostructure can be obtained through the positive and negative surface anisotropy constants of perpendicular and c-axis parallel to the crystal. We have measured the magnetic properties of 偽 -Fe _ 2O _ 3 nanostructures from room temperature to 980K. Firstly, the thermal stability of different nanostructures was determined by measuring the magnetic properties before 920K at a high vacuum of 9.5 脳 10 ~ (-6) Torr. The experimental results show that there exists a phase transition process from 偽 -Fe _ 2O _ 3 to Fe3O4 at high temperature and high vacuum, and this transition process is strongly influenced by the shape of nanostructures. The experimental data show that the phase transition mainly occurs on the crystal surface. Due to the high thermal stability of nanorings and nanotubes, their N 茅 el temperatures can be accurately measured. The N 茅 el temperature of nanorings and nanotubes decreases with the decrease of the wall thickness of nanometers and nanotubes. The two-dimensional finite size effect of N 茅 el temperature is conformed to the N 茅 el temperature.) We have successfully prepared 偽 -Fe _ 2O _ 3C nanospheres by a simple two-step method. Compared with pure 偽 -Fe _ 2O _ 3 electrode material, 偽 -Fe _ 2O _ 3 @ C nanorings exhibit higher capacity and better charge-discharge performance. More importantly, 偽 -Fe _ 2O _ 3C nanospheres have better cycling performance (the capacity of 815m Ahg-1 is retained after 1000 m Ag-1 current recharge and discharge 160m). Because of the unique structure and excellent electrochemical performance of 偽 -Fe _ 2O _ 3 @ C nanospings, 偽 -Fe _ 2O _ 3 @ C nanorods can be used as a promising anode material for high performance lithium ion batteries. At the same time, the ring structure can also be used as precursor to synthesize other high performance Fe2O3 based lithium ion battery anode materials.
【學(xué)位授予單位】：寧波大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB383.1;O614.811

【共引文獻(xiàn)】

相關(guān)博士學(xué)位論文 前3條

1 劉瑞江;磁性氧化鐵基納米結(jié)構(gòu)的構(gòu)筑及其應(yīng)用研究[D];江蘇大學(xué);2013年

2 田苗;低維材料若干熱力學(xué)參數(shù)的尺寸和界面效應(yīng)[D];吉林大學(xué);2015年

3 何學(xué)敏;3d過渡金屬及其氧化物納米顆粒的磁性[D];南京大學(xué);2015年

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本文編號：1885706