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    Please use this identifier to cite or link to this item: http://ir.lib.ksu.edu.tw/handle/987654321/6458


    Title: 火焰合成奈米碳管的研究
    Flame Synthesis of Carbon Nanotubes
    Authors: 侯順雄
    Keywords: 火焰合成
    奈米碳管
    反置擴散火焰
    Flame Synthesis
    Carbon Nanotubes
    Inverse Diffusion Flame
    Date: 2006-07-31
    Issue Date: 2009-12-30 14:23:14 (UTC+8)
    Abstract: 本研究利用反置同軸噴流擴散火焰,探討不同燃料濃度、沉積方式、沉積位置以及金屬觸媒催化方式等參數對燃燒合成奈米碳管之成長機制及其結構的影響。研究中選擇適當的參數,以鎳網當作沉積基板和金屬催化物來合成奈米碳管,並以穿透式電子顯微鏡(TEM和HR-TEM)及掃描式電子顯微鏡(SEM)觀察不同實驗條件下所生成奈米碳管的形態及結構。發現在黃焰生成之臨界燃料濃度(高和低沉積位置)下,垂直沉積之方式可使碳原子滯留在基板上的時間及數量增多,故合成奈米碳管的數量與長度優於水平沉積。然而在高燃料濃度且高沉積位置時,垂直沉積之方式會使得滯留之碳原子數量過多,易集結成碳顆粒,奈米碳管生成量銳減,故此時水平沉積效果較佳。比較同一沉積基板上奈米碳管生成之數量,發現在遠離火焰端不易觀察到奈米碳管,而基板上靠近火焰端則是奈米碳管生成最多的地方。利用HR-TEM觀察其管壁發現其為多壁奈米碳管(MWNTs),且所生成之奈米碳管有直管(Straight- Tubular)及類竹(Bamboo-Like)兩類。所合成之奈米碳管的頂端、底部及轉折處均有粒狀物,推測其係為氧化鎳。在鎳格網上沾附硝酸鎳溶液,其合成奈米碳管的數量較純鎳格網多且範圍更廣、長度更長,代表在不同金屬觸媒催化方式中,沾附硝酸鎳溶液的鎳格網,有助於火焰合成奈米碳管。
    This experimental study is aimed at investigating the formation and growth of carbon nanotubes by using inverse co-flowing diffusion flames. The flame appearance and flame stability under the influences of oxidizer and fuel concentrations and inner/outer velocity ratios were firstly studied. The results showed that raising the concentration of oxygen or fuel increased the flame intensity, and in turn decreased the critical fuel concentrations for the occurrence of yellow flame. However, with increasing the velocity of oxygen/nitrogen mixture, the sooty zone became narrower, leading to the increase of the critical fuel concentration where yellow flame took place. Thereafter, we employed a sampling grid (Ni) used for transmission electron microscopy as the catalytic metal substrate for the nanotube growth. Synthesis of canbon nanotubes was successfully found from laminar co-flowing oxygen-enriched ethylene diffusion flames. The horizontal sampling approach (with the grid plane normal to the burner axis) to collect deposited materials, carbon nanotubes grew much more and longer than the horizontal sampling approach (with the grid plane parallel to the burner axis) at the critical concentration where yellow flame occured. However, at the fuel concentration higher than the critical concentration where yellow flame took place, there were higher radical concentrations as the grid was placed at a higher position. Therefore, at this condition using the horizontal sampling approach to collect deposited materials was superior to the vertical sampling approach. Furthermore, for the same sampling approach, the position near the flame front had a greater carbon nanotube harvest than that far from the flame front. Straight and bamboo-like carbon nanotubes were observed in the HR-TEM images. We assumed that the particles in the carbon nanotubes are nickel oxide. It is evidenced that carbon nanotubes are produced by the heat source and carbon source in the inverse diffusion flame with the metal catalyst (Ni).
    Appears in Collections:[機械工程系所] 研究計畫

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