燃烧法合成碳纳米管的实验方案设计

碳纳米管是一种新型的碳材料,其合成方法多种多样。燃烧法是一种新兴的合成方法,燃烧过程提供用于碳纳米管生长的高温环境,同时也提供足够的烃原料。目前,用于合成碳纳米管的原料包括气体燃料和液体燃料,火焰类型主要有层流扩散火焰、逆流扩散火焰和预混火焰等。影响炭纳米管火焰合成的因素主要有气体成分,温度,催化剂,燃氧比和采样条件。我们采用甲烷扩散火焰用于实验研究炭纳米管的合成条件。实验系统包括扩散火焰喷嘴,混和段,质量流量计,取样探针和基板,气源。内径5 mm的喷嘴与内径100 mm的钢筒同轴。实验测得在气量为0．20 SLM时火焰高度为 3．5 cm。涂覆有催化剂的基板水平朝下置于火焰中采样,并将采集的样品进行电镜分析。本文还对燃烧法合成碳纳米管的机理进行了分析。

EXPERIMENTAL RESEARCH ON SYNTHESIS OF CARBON NANOTUBES

Carbon nanotubes (CNTs) could be synthesized in many procedures. Flame synthesis is a novel method, which can provide high temperature and adequate hydrocarbons environment for CNTs growth. Either gaseous or liquid fuel may be used to the synthesis process. The flame synthesis procedure involves laminar diffusion flame, counter flow flame and premix flame. CNTs synthesis in flames is restricted by fuel gas content, temperature, catalyst, equilibrium rate and sampling position. In this paper a methane diffusion flame experiment system is introduced to synthesize CNTs, involving diffusion flame nozzle, mixture section, mass meter, sampling probe and alloy substrate as well as high pressure fuel gas. Methane flows through a 5 mm-diameter nozzle which is concentric with a 100 mm steel cylinder. The experimental study shows that a 35 mm visible high diffusion flame is formed above the nozzle with flow rate 0.20 SLM. The nickel nitrite or ferrocene solution is coated on the substrate and probe to form a catalyst membrane. Then the substrate is inserted into the flame with catalyst upon the flame horizontally which then are characterized by SEM and TEM. The mechanisms of carbon nanotubes by flame synthesis are also introduced to explain the formation of carbon nanotubes.