本文利用聲波振動甲烷-乙烯噴流擴散火焰燃燒合成奈米碳結構，並在催化型的鎳基質狀況下。其研究焦點在於探討聲波振動頻率和甲烷-乙烯混合比對合成奈米碳結構的影響。聲波振動會增強火焰與渦漩之間的交互作用，進而提升燃料和氧化物之混合，對熱環境和奈米碳結構生成會有重要的影響。
文中探討聲波振動頻率(f = 0~90 Hz)以及混合燃料 (甲烷-乙烯混合燃料，乙烯濃度ΩE =0~100%)對火焰結構與奈米材料生成之影響。實驗結果顯示，當乙烯濃度低於40%，f = 10 Hz時，或乙烯濃度為0%(即純甲烷)，f = 90 Hz 時，火焰熄滅，其主因是由於此時火焰強度較低，而若週遭空氣因聲波振動引入，會造成火焰熄滅。而無聲波振動(f = 0 Hz)時，在所有乙烯濃度下，火焰皆為單層結構，且幾乎無奈米碳材料生成；當振動頻率在10~90 Hz時，可觀察到雙層的火焰結構。
然而，在z = 10 mm且P = 10和15 W時，當聲波頻率接近其自然擺盪頻率(即為f = 20 Hz，0% ≤ ΩE ≤ 100%)，由於燃料與空氣混合的改善，使得有良好的碳合成。合成的產物為蔥狀形奈米碳結構，其形狀如數個葡萄串疊起來。在f = 70 Hz，且40% ≤ ΩE ≤ 100%、P = 10 W和60% ≤ ΩE ≤ 100%、P = 15 W時，高強度的蔥狀形奈米碳結構會生成。更進一步地，在f = 80 Hz，且ΩE = 0%、P = 10 W和0% ≤ ΩE ≤ 5%、P = 15 W時，奈米碳管會生成。在P = 15 W、f = 70 Hz且ΩE = 0%，蔥狀形奈米碳結構也包含鎳基質，而在其他的狀況下，幾乎沒有奈米碳結構生成。
合成奈米碳管的合適溫度範圍比合成蔥狀形奈米碳結構的要來得高 (CNTs : 580~630oC，CNOs :500~600oC)。藉由氣體成分分析可知，在低濃度的CH4和CO(低碳源)時，且溫度也低時，觀察不到奈米碳結構。要合成奈米碳管的範圍，CH4的濃度須高於50%。

Recently, flame synthesis of carbon nano-materials has been widely explored due to its advantages over other production methods that use expensive inputs, such as electricity as the heat source. In this study, methane-ethylene jet diffusion flames modulated by acoustic excitation in an atmospheric environment were used to synthesize carbon nanostructures on a catalytic nickel substrate.
Experiments were conducted to investigate the effects of acoustic excitation frequency (f = 0~90 Hz) and mixed fuel (ethylene concentration ΩE =0~100% in blends of methane-ethylene) on flame structure and nano-material formation. The results show that the flame could not be stabilized on the port for ethylene concentrations (ΩE) of less than 40% at f = 10 Hz, or for ΩE = 0% (i.e., pure methane) at f = 90 Hz, because the flame had a low intensity and was extinguished by the entrained air due to acoustic modulation. Without acoustic excitation f = 0 Hz, the flame comprised a single-layer structure for all values of ΩE and almost no carbon nano-materials were synthesized. But, when frequencies were in the range of 10~90 Hz, a double-layer flame structure was observed.
However, when acoustic excitation neared the natural flickering frequency (i.e., at f = 20 Hz for 0% ≤ ΩE ≤ 100%) at z = 10 mm when P = 10 and 15 W, good carbon synthesis occurred as a result of improved mixing of the fuel with the ambient air. The synthesized products were carbon nano-onions (CNOs) piled like bunches of grapes. High-density CNOs were produced at f = 70 Hz for 40% ≤ ΩE ≤ 100% and 60% ≤ ΩE ≤ 100% at 10 and 15 W, respectively. Further, carbon nano-tubes (CNTs) were synthesized at 80 Hz for ΩE = 0% and 0% ≤ ΩE ≤ 5% at 10 and 15 W, respectively. For P = 15 W at 70 Hz for ΩE = 0%, the CNTs also covered the Ni substrate. Other than these cases, almost no carbon nano-materials were formed.
The suitable temperature ranges for the synthesis of CNTs were slightly higher than for CNOs (580~630oC for CNTs, 500~600oC for CNOs). Gas composition analysis indicated that at low CH4 and CO concentration (low carbon source) and low temperature, no carbon nano-materials could be observed. In the synthesis region of CNTs, the concentration of CH4 was greater than 50%.

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