Control of morphology and crystallinity of CNTs in flame synthesis with one-dimensional reaction zone

Muhammad Hilmi Ibrahim; Norikhwan Hamzah; Mohd Zamri Mohd Yusop; Ni Luh Wulan Septiani; Mohd Fairus Mohd Yasin

doi:10.3762/bjnano.14.61

Control of morphology and crystallinity of CNTs in flame synthesis with one-dimensional reaction zone

Beilstein J Nanotechnol. 2023 Jun 21:14:741-750. doi: 10.3762/bjnano.14.61. eCollection 2023.

Authors

Muhammad Hilmi Ibrahim^#^{1

2}, Norikhwan Hamzah^#^{1

2}, Mohd Zamri Mohd Yusop³, Ni Luh Wulan Septiani⁴, Mohd Fairus Mohd Yasin^{1

2}

Affiliations

¹ Department of Thermo-Fluids, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Malaysia.
² High Speed Reacting Flow Laboratory (HiREF), Universiti Teknologi Malaysia, 81310 Johor Bahru, Malaysia.
³ Advanced Membrane Technology Research Center, Universiti Teknologi Malaysia, 81310 Johor Bahru, Malaysia.
⁴ National Research and Innovation Agency, Indonesia.

^# Contributed equally.

Abstract

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.

Keywords: carbon nanotubes; crystallinity; flame synthesis; morphology; one-dimensional flame; synthesis control.

Grants and funding

This research was supported by the Ministry of Education (MOE) through the Fundamental Research Grant Scheme (FRGS/1/2020/TK0/UTM/02/54) with cost center number R.J130000.7851.5F377. The research is also funded by Universiti Teknologi Malaysia (UTM) through UTM Fundamental Research (UTMFR: PY/2019/01657) grant with cost center number Q.J130000.2551.21H10.