Abstract:

Flame synthesis of carbon nanotubes (CNTs) and related composites possesses the merits of continuous operation with low-cost, which shows great potential for practical application. However, the physical and chemical environments of flame are complex. Therefore, the as-obtained product exhibits unmanageable structure and composition. In this work, the basic configuration of premixed flame and diffusion is firstly presented. On this basis, the features of flame synthesis in terms of fuel type, catalyst and characteristics of CNTs are summarized. Secondly, the general growth mechanism of CNTs in flame environment is introduced. Furthermore, specific growth models of CNTs in flame environment, including tip growth mode, base growth mode, interacting particle model and reasonable growth mode for branch, welded, and spiral structures are discussed. Finally, practical application of flame synthesized CNTs based composites in areas of energy storage, catalyst and so forth, are summarized. However, the drawbacks, such as poor controllability of flame process and complex product composition are still existed, which is unfavorable for performance regulation. In future, continuous optimization of flame process is needed. Adopting hybrid preparation process or constructing segmental burner configuration will play a positive role in improving process controllability and finally realizing the refinement regulation of product.

Key words: catalyst, nanomaterials, flame synthesis, preparation, carbon nanotubes

摘要：

火焰法制备CNTs及其复合材料具有可连续操作、成本低廉等优势，是一种极具应用潜力的制备技术。然而，火焰环境的复杂性造成产品结构和组成难以精确控制，在实际应用时不利于产品性能的调控和提升。本文首先介绍了火焰法的基本构型（扩散火焰和预混合火焰），并结合燃料、催化剂和制备CNTs的结构说明了不同火焰法工艺的特点。随后简要说明了火焰环境中CNTs生长的一般过程，即吸附-扩散-沉积过程，结合这一基本过程介绍了顶部/底部生长机理、颗粒接触生长机理和异形（螺旋状、竹节状、空心/实心结构、分支结构等）CNTs的生长机理。在全面总结火焰法制备CNTs基复合材料在储能、催化、光热转化等领域应用的基础上，指出现有火焰法制备工艺存在可控性差、产品组成复杂等问题，在实际应用时不利于相关性能的调控。在未来研究中，持续改进和优化火焰法工艺，如采用混合式制备工艺或构建分段式燃烧器构型，对于提高工艺过程可控性并实现产品组成和结构的调控具有积极作用。

关键词: 催化, 纳米材料, 火焰法, 制备, 碳纳米管