Abstract: Flame synthesis of carbon nanotubes is a novel, energy efficient and low cost method. The flame method can simultaneously provide the carbon source and heat source needed for the preparation of carbon nanotubes, and has the potential to prepare carbon nanotubes on a large scale, over the existing conventional methods. Tremendous progress has been achieved during the past 20 years on not only improving the yields of carbon nanotubes and move progressively towards their mass production, but also on gaining a profound fundamental understanding of the nucleation and the growth processes. However, controlling the synthesis of carbon nanotubes in the flame is still a huge challenge, due to the extremely complex environment. The purpose of the present review is not to list all the experiments reported in the literature, but rather to identify trends and provide a comprehensive summary on the role of selected parameters in the flame. In this work, the structure and properties of carbon nanotubes were introduced firstly, then the research progress of carbon nanotubes by diffusion and premixed flame, including co-flow diffusion flame, inverse diffusion flame, counter diffusion flame, single-face wall stagnation flame and double-face wall stagnation flame were summarized, and the vapor–liquid–solid, tip and base, hollow and solid growth mechanisms of carbon nanotubes were briefly described. The synthesis of carbon nanotubes based on a methane/air coaxial jet diffusion flame by our group was also introduced. Through SEM, XRD and TEM characterization, it was proved that metallic nickel played a catalytic role. The catalyst particles were coated inside the carbon nanotubes, and the flame synthesized carbon nanotubes were based on a vapor–liquid–solid growth mechanism. The diameter of carbon nanotubes was distributed between 50 nm and 90 nm with an average diameter of 65 nm. Finally, the research direction of the preparation of carbon nanotubes by flame method was prospected.

Key words: carbon nanotubes, research progress, preparation method, flame method

摘要： 火焰法是近20年来兴起的一种新颖、高能效、低成本的碳纳米管制备方法。火焰法能同时提供制备碳纳米管所需的碳源和热源，具有大规模制备碳纳米管的潜力。由于火焰中环境极其复杂，控制火焰中碳纳米管的合成仍是巨大的挑战。本工作介绍了碳纳米管的结构及其性能，综述了扩散火焰(同轴扩散火焰、反扩散火焰和对冲扩散火焰)和预混火焰(单面滞止火焰和双面滞止火焰)制备碳纳米管的研究进展，并对碳纳米管的vapor–liquid–solid、顶部和底部及空心和实心生长机理作了简要阐述，介绍了本课题组基于甲烷/空气同轴射流火焰制备碳纳米管的研究进展。分析表明，金属镍起催化作用，催化剂颗粒包覆在碳纳米管内部，火焰合成的碳纳米管基于vapor–liquid–solid生长机制，碳纳米管直径为50~90 nm，平均直径为65 nm。对火焰法制备碳纳米管的发展方向进行了展望。

关键词: 碳纳米管, 研究进展, 制备方法, 火焰法