本文關鍵詞： 磁場輔助電弧放電法 單壁碳納米管 拉曼光譜　出處：《新疆大學》2015年碩士論文　論文類型：學位論文

【摘要】：根據手性和直徑的不同,單壁碳納米管可以是金屬性的或者是半導體性的,而且半導體性單壁碳納米管的帶隙與其直徑成反比關系,同時單壁碳納米管優(yōu)異的光學、電學及機械特性與其直徑或手性密切相關。但目前所制備的單壁碳納米管樣品中絕大多數是由不同直徑和手性的單壁碳納米管組成的,并且難以分離,不適于用來制作高性能微納米器件。因此獲得特定直徑和手性的單壁碳納米管已經成為單壁碳納米管制備方面急需解決的科學問題。本文以煤和石墨粉為碳源,研究了催化劑組成、外加磁場及強度、緩沖氣體壓強及組成對直流電弧放電法制備碳納米材料結構和組成的影響,具體研究內容如下:以新疆庫車煤炭為碳源,首先研究了不同催化劑(Ni、Ni-La2O3、Ni-Y2O3)的催化效率,確定了當以氦氣為緩沖氣體時,Ni-Y2O3作催化劑,產物中單壁碳納米管的純度最高。進一步研究了以Ni-Y2O3為催化劑,磁場輔助電弧放電制備單壁碳納米管實驗中磁場和緩沖氣體氦氣的壓強對單壁碳納米管直徑的協(xié)同影響,通過拉曼表征發(fā)現(xiàn),在相對較低的氦氣壓強下(35 kPa),施加外加磁場后可以明顯降低單壁碳納米管的直徑(不加磁場時最小直徑為1.36 nm,施加磁場后最小直徑可達1.20 nm),同時可以獲得單一的半導體性單壁碳納米管。在直流電弧放電實驗中,通過引入反應性氣體(氫氣)對單壁碳納米管成核與生長過程進行主動干預來調控單壁碳納米管直徑的分布。拉曼測試結果表明,增加氫氣在緩沖氣體中的含量能夠抑制小直徑單壁碳納米管的形成,而使單壁碳納米管直徑分布向更大直徑的方向移動。同時,引入少量(在緩沖氣體中所占體積分數不大于3%)氫氣在一定程度上可以提高產物中單壁碳納米管的純度。以石墨粉為碳源,研究了Ni-Y2O3催化劑、緩沖氣體組成及外加磁場對電弧放電產物結構的影響。通過拉曼光譜和場發(fā)射掃描電子顯微鏡表征發(fā)現(xiàn),氦氫緩沖氣體中氫氣的含量對磁場輔助電弧放電法制備的碳材料形貌結構影響較大,氫氣的存在會抑制石墨片層卷曲成單壁碳納米管,隨著氫氣含量的增加,單壁碳納米管的含量逐漸減少,而石墨烯片層的含量逐漸增加,但當氫氣的含量超過最佳值時,產物主要由比較大的石墨化多面體組成。高分辨透射電子顯微鏡及拉曼表征結果表明在氫氣含量占3%(體積分數)時所制備的石墨烯具有較少的層數,且缺陷較少。并進一步研究了磁場強度對石墨烯產率的影響,研究發(fā)現(xiàn)當磁場強度在42-51G之間時可以制備出較高含量的石墨烯。
[Abstract]:Depending on the chirality and diameter, single walled carbon nanotubes can be gold or semiconductive, and the band gap of semiconductor single walled carbon nanotubes is inversely proportional to their diameter. At the same time, single-walled carbon nanotubes have excellent optics. Electrical and mechanical properties are closely related to their diameters or chiral properties. However, most of the single walled carbon nanotubes (SWNTs) made up of different diameters and chiral properties are difficult to separate. It is not suitable to be used to fabricate high performance micro-nanodevices. Therefore, obtaining single-walled carbon nanotubes with specific diameter and chirality has become a scientific problem in the preparation of single-walled carbon nanotubes. In this paper, coal and graphitic powder are used as carbon sources. The effects of catalyst composition, applied magnetic field and intensity, buffer gas pressure and composition on the structure and composition of carbon nanocomposites prepared by DC arc discharge were studied. The main contents are as follows: Kuqa coal was used as carbon source in Xinjiang. Firstly, the catalytic efficiency of different catalysts Ni Ni La 2O 3 O 3 Ni Y 2O 3 was studied, and Ni-Y 2O 3 was used as catalyst when helium was used as buffer gas. The purity of single-walled carbon nanotubes was the highest among the products. Ni-Y2O3 was used as catalyst. The cooperative effect of magnetic field and helium pressure on the diameter of single-walled carbon nanotubes (SWNTs) prepared by magnetic-assisted arc discharge was investigated by Raman spectroscopy. At a relatively low helium pressure of 35 KPA, the diameter of single-walled carbon nanotubes can be significantly reduced by applying an applied magnetic field (the minimum diameter is 1.36 nm without magnetic field added). The minimum diameter can reach 1.20 nm after the application of magnetic field, and a single semiconductor single-walled carbon nanotube can be obtained at the same time. The diameter distribution of single-walled carbon nanotubes was regulated by introducing reactive gas (hydrogen) into the nucleation and growth process of single-walled carbon nanotubes. Increasing the hydrogen content in the buffer gas can inhibit the formation of small diameter single-walled carbon nanotubes and make the diameter distribution of single-walled carbon nanotubes move towards the direction of larger diameter. The purity of single-walled carbon nanotubes in the product can be improved to a certain extent by introducing a small amount of hydrogen (the volume fraction in buffer gas is no more than 3). The Ni-Y2O3 catalyst was studied using graphite powder as carbon source. Effects of buffer gas composition and applied magnetic field on the structure of arc discharge products were investigated by Raman spectroscopy and field emission scanning electron microscopy. The content of hydrogen in helium hydrogen buffer gas has a great influence on the morphology and structure of carbon materials prepared by magnetic field assisted arc discharge method. The existence of hydrogen will inhibit the graphite lamellar curling into single-walled carbon nanotubes, with the increase of hydrogen content. The content of single-walled carbon nanotubes decreases gradually, while the content of graphene layer increases gradually, but when the hydrogen content exceeds the optimal value. The products were mainly composed of larger graphitized polyhedrons. The results of high resolution transmission electron microscopy (TEM) and Raman spectroscopy showed that the graphene prepared at the hydrogen content of 3 / 3 (volume fraction) had a small number of layers. The effect of magnetic field intensity on the yield of graphene was further studied. It was found that a higher content of graphene could be prepared when the magnetic field intensity was between 42 and 51G.
【學位授予單位】：新疆大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ127.11;TB383.1

【共引文獻】

相關博士學位論文 前1條

1 張帆;電弧放電法制備新型碳—鐵納米復合材料以及碳-氮納米材料[D];天津大學;2013年

相關碩士學位論文 前1條

1 吳霞;新疆煤基碳納米管的制備及表征[D];新疆大學;2013年

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本文編號：1482381