采用电弧放电法在氦气/乙炔混合气氛中,在不同压力下合成了碳纳米管.运用场发射扫描电镜、场发射透射电镜、X-射线衍射仪和拉曼光谱对碳纳米管的形貌进行了表征.采用可见发射光谱对碳纳米管的形成过程进行了原位诊断研究.场发射扫描电镜结果表明,在氦气/乙炔气氛中合成的碳纳米管的长度大于50微米,许多碳颗粒沉积在碳纳米管壁上.场发射透射电镜结果表明,在0.100MPa下合成的碳纳米管的壁厚明显大于0.035MPa下合成的碳纳米管的壁厚.可见发射光谱诊断结果表明,CH和C2物种可能作为碳纳米管形成的前驱体,其中,以H原子作为无定形炭的刻蚀物种.阳极消耗速率和产物在阴极的沉积速率随着反应器中压力的增加而增加.因此,可以通过加强阳极和乙炔的蒸发速率及CH和C2物种的沉积速率而增加碳纳米管的形成速率.
Carbon nanotubes (CNTs) were synthesized at different pressure in He/C2H2 gas mixture by arcdischarge. The morphologies of CNTs were characterized by field emission scanning electron microscope (FE- SEM), field emission scanning and transmission electron microscope (STEM), X -ray diffraction (XRD) and Raman spectroscopy. Optical emission spectroscopy (OES) was used in situ to investigate the formation process of CNTs. FE - SEM observation reveals that the length of CNTs synthesized in He/C2H2 gas mixture is more than 50 μm and some carbon particles deposit on the wall of CNTs. STEM characteriza-tion illustrates that the CNTs wall synthesized at 0. 100 Mpa is obviously bigger than that synthesized at O.035 Mpa. OES results show that CH and C2species might act as the formation precursors of CNTs with H atom acting as etching species of amorphous carbon. The consumption rate of anode and product deposit rate on cathode increase with increasing pressure in the reactor. Thus, it is possible to increase the deposit rate of CNTs at higher pressure in the arc reactor by enhancing the evaporation rate of anode from the anode and C2H2 as well as the deposit rate of CH and C2 species.
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