Ibrahim Muhammad Hilmi, Hamzah Norikhwan, Mohd Yusop Mohd Zamri, Septiani Ni Luh Wulan, Mohd Yasin Mohd Fairus
Department of Thermo-Fluids, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Malaysia.
High Speed Reacting Flow Laboratory (HiREF), Universiti Teknologi Malaysia, 81310 Johor Bahru, Malaysia.
Beilstein J Nanotechnol. 2023 Jun 21;14:741-750. doi: 10.3762/bjnano.14.61. eCollection 2023.
The growth of carbon nanotubes (CNTs) in a flame requires conditions that are difficult to achieve in a highly heterogeneous environment. Therefore, the analysis of the properties of the reaction zone within the flame is critical for the optimal growth of CNTs. In the present study, a comprehensive comparison between the CNT synthesis using a methane diffusion flame and a premixed flame is conducted regarding the morphology and crystallinity of the as-grown nanotubes. The premixed burner configuration created a flame that is stabilized through axisymmetric stagnation flow through sintered metal with one-dimensional geometry, different from a conventional co-flow flame. The significant difference in temperature distribution between the two flames causes a difference in the characteristics of the growth products. In the diffusion flame, the growth is limited to specific regions at certain height-above-burner (HAB) values with a temperature range of 750 to 950 °C at varying radial locations. The identified growth regions at different HAB values showed similar temperature distributions that yield CNTs of similar characteristics. Interestingly, the growth of CNTs in the premixed flame is dictated by only the HAB because the temperature distribution is relatively uniform along the radial directions but significantly different in the vertical direction. 17.3% variation in temperature in the axial direction successfully led to 44% and 66% variation in CNT diameter and crystallinity, respectively. The morphology control capability demonstrated in the present study is important for CNT functionalization for energy storage, nanosensor, and nanocomposite applications, where diameter and crystallinity are influential properties that govern the overall performance of the components.
碳纳米管（CNT）在火焰中的生长需要在高度非均相的环境中难以实现的条件。因此，分析火焰内反应区的性质对于碳纳米管的最佳生长至关重要。在本研究中，针对生长的纳米管的形态和结晶度，对使用甲烷扩散火焰和预混火焰合成碳纳米管进行了全面比较。预混燃烧器配置产生了一种火焰，该火焰通过具有一维几何形状的烧结金属的轴对称滞止流来稳定，这与传统的并流火焰不同。两种火焰之间温度分布的显著差异导致了生长产物特性的差异。在扩散火焰中，生长限于燃烧器上方特定高度（HAB）值处的特定区域，在不同径向位置的温度范围为750至950°C。在不同HAB值下确定的生长区域显示出相似的温度分布，产生具有相似特性的碳纳米管。有趣的是，预混火焰中碳纳米管的生长仅由HAB决定，因为温度分布在径向方向上相对均匀，但在垂直方向上有显著差异。轴向温度17.3%的变化分别成功导致碳纳米管直径和结晶度44%和66%的变化。本研究中展示的形态控制能力对于用于能量存储、纳米传感器和纳米复合材料应用的碳纳米管功能化很重要，在这些应用中，直径和结晶度是影响组件整体性能的重要特性。
