碳源对碳纳米管形态的影响

The effect of carbon source on the morphology of carbon nanotubes

以苯和甲苯为碳源,二茂铁为催化剂,含硫化合物为助催化剂,采用浮游催化裂解法制备了碳纳米管,并采用TEM对不同条件下所得碳纳米管进行了形态分析。结果发现,碳源中苯和甲苯的配比对碳纳米管的形态有着重要的影响。以纯苯为碳源时,产物主要为直线型碳纳米管,并存在极少量短的弯曲型碳纳米管。随着碳源中甲苯比例的增加,产物中折线型碳纳米管增加。以纯甲苯为碳源,产物中仍有少量直线型碳纳米管,而不完全是折线型碳纳米管;此外,产物中还发现了极少量分支型碳纳米管。根据所得结果讨论分析了甲苯的加入对碳纳米管形态的影响以及各种碳纳米管的形成机理,认为可能是由于甲苯在催化热解过程中产生的碳种不同于苯催化热解所产生的碳种,造成碳在催化剂颗粒各处浓度不同,从而在碳纳米管的不同部位引入五元环和七元环而形成各种形态的碳纳米管。

Carbon nanotubes were prepared by the floating catalyst method using benzene and toluene as the carbon source and ferrocene with a sulfurous compound as the catalyst. The nanotubes were characterized by TEM, which shows that the ratio between benzene and toluene in the carbon source has a significant influence on the morphologies of the carbon nanotubes. Straight nanotubes are predominant with small amount of curled nanotubes when pure benzene is used as carbon source and the amount of curled nanotubes increases with increasing amount of toluene in the carbon source. Branching carbon nanotubes are predominant with small amount of straight carbon nanotubes when pure toluene is used as the source. Based on these results, the effect of the increase of toluene on the morphologies of the carbon nanotubes is discussed and a growth mechanism of the nanotubes is proposed, which indicates that the seeding carbon from the catalytic pyrolysis of toluene is different from that of benzene, causing the differences of carbon concentration on the surface of the catalyst particles, and pentagon and heptagon carbon in the hexagonal lattice of the nanotubes. This leads to the formation of carbon nanotubes with different morphologies.