氧濃度對使用混合燃料反置擴散火焰合成奈米碳結構之影響

Influence of Oxygen Concentration on Synthesis of Carbon Nano-Structures in Inverse Jet Diffusion Flames of Mixed Fuels

陳文章(Wen-Chang Chen)

指導教授 ： 侯順雄

崑山科技大學/工程學院/機械工程研究所/碩士(2008年)

摘要

本研究之目的在於利用反置擴散火焰，探討燃料濃度、氧氣濃度、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結構之成長機制及其結構的影響。研究中擴散火焰可提供燃燒合成所需的熱源和碳源，而以鎳網格當作沉積基板則提供合成所需的金屬觸媒。合成的奈米碳結構，以掃描式電子顯微鏡(SEM)、穿透式電子顯微鏡TEM和拉曼光譜觀察分析不同實驗條件下所生成之奈米碳結構的形態和微結構。結果發現基板上沉積之奈米碳結構以奈米碳管與奈米碳球為主。以奈米碳管生成情況而言，氧氣濃度從21%提高至40%時，生成範圍會變寬且數量會變多。若以奈米碳管與奈米碳球共生來看，其大部分都生成於氧氣濃度30%、35%及40%合成區主要在火焰面附近，且高氧氣濃度時的生成範圍及數量都大於低氧氣濃度。再以奈米碳球來看，其大部分都生成於30%、35%及40%，且會發生在火焰面內側(氧氣側)，其原因為火焰面裡面有充足的碳源和合適的氧氣濃度和溫度，由以上結果可得知，氧氣濃度對於合成奈米碳結構有重要的影響。欲大量生成奈米碳結構需有適當的火焰參數(碳源、熱源(溫度)及氧氣濃度)和金屬觸媒催化。

關鍵字

火焰合成 ； 奈米碳結構 ； 反置擴散火焰 ； 氧氣濃度 ； 奈米碳管 ； 奈米碳球

並列摘要

The influence of volumetric oxygen concentration on the formation and growth of carbon nano-structures including carbon nanotubes (CNTs) and carbon nanocapsules in inverse co-flowing diffusion flames was experimentally studied. We employed a sampling Ni grid as the catalytic metal substrate for the carbon nano-structures growth. The sampling time of the substrate inside the flame was kept at 120 sec. The SEM and TEM images showed that carbon nano-structures deposited on the substrates were only CNTs for a lower oxygen concentration 25%. However, for higher oxygen concentrations30%, 35%, and 40%, besides curved CNTs, carbon nanocapsules were also synthesized. Note that both the growth range and yield of carbon nano-structures were increased with increasing oxygen concentration. Additionally, the sampling positions on or near the yellow flame front had a greater carbon nano-structures harvest than those far from the flame front.

並列關鍵字

Flame Synthesis ； Carbon Nano-Structures ； Inverse Diffusion Flame ； Carbon Nanotubes ； Carbon Nanocapsule ； oxygen concentration

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