Hou Shuhn-Shyurng, Chen Kuan-Ming, Yang Zong-Yun, Lin Ta-Hui
Department of Mechanical Engineering, Kun Shan University, Tainan 71070, Taiwan.
Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan 70101, Taiwan.
Materials (Basel). 2015 Jul 29;8(8):4805-4816. doi: 10.3390/ma8084805.
Acoustically modulated methane jet diffusion flames were used to enhance carbon nanostructure synthesis. A catalytic nickel substrate was employed to collect the deposit materials at sampling position = 10 mm above the burner exit. The fabrication of carbon nano-onions (CNOs) and carbon nanotubes (CNTs) was significantly enhanced by acoustic excitation at frequencies near the natural flickering frequency (ƒ = 20 Hz) and near the acoustically resonant frequency (ƒ = 90 Hz), respectively. At these characteristic frequencies, flow mixing was markedly enhanced by acoustic excitation, and a flame structure with a bright slender core flame was generated, which provided a favorable flame environment for the growth of carbon nanomaterials. The production rate of CNOs was high at 20 Hz (near the natural flickering frequency), at which the gas temperature was about 680 °C. Additionally, a quantity of CNTs was obtained at 70-95 Hz, near the acoustically resonant frequency, at which the gas temperature was between 665 and 830 °C. However, no carbon nanomaterials were synthesized at other frequencies. The enhanced synthesis of CNOs and CNTs is attributed to the strong mixing of the fuel and oxidizer due to the acoustic excitation at resonant frequencies.
采用声学调制的甲烷射流扩散火焰来增强碳纳米结构的合成。使用催化镍基底在燃烧器出口上方10毫米的采样位置收集沉积材料。分别在接近自然闪烁频率（ƒ = 20 Hz）和接近声学共振频率（ƒ = 90 Hz）的频率下，通过声激发显著增强了碳纳米洋葱（CNOs）和碳纳米管（CNTs）的制备。在这些特征频率下，声激发显著增强了流动混合，并产生了具有明亮细长核心火焰的火焰结构，这为碳纳米材料的生长提供了有利的火焰环境。在20 Hz（接近自然闪烁频率）时CNOs的生产率很高，此时气体温度约为680°C。此外，在接近声学共振频率的70 - 95 Hz时获得了一定量的CNTs，此时气体温度在665至830°C之间。然而，在其他频率下未合成碳纳米材料。CNOs和CNTs合成的增强归因于共振频率下声激发导致的燃料与氧化剂的强烈混合。
