Inner-diameter enlargement of multi-walled carbon nanotubes by adding HBO_3 in catalyst

摘要

Multi-walled carbon nanotubes (MWCNTs) with large inner diameter were synthesized by the catalytic chemical vapor deposition method using HBO_3 as the accessorial catalyst in reaction precursors. A ratio D_(in)/D_(out) is defined as an index to evaluate the hollow degree of MWCNTs, where D_(in) and D_(out) are the inner and outer diameter of one CNT, respectively. When no HBO_3 was added in the reaction mixtures, the MWCNTs are straight with thick wall. The average D_(in)/D_(out) value is only 0.08 ±0.02. The X-ray diffraction (XRD) result shows the relatively low crystallinity. When HBO_3 was added in the reaction precursors, the MWCNTs have large inner cavity and the average D_(in)/D_(out) value reaches 0.57 ± 0.10. The crystallinity was also improved remarkably. These results indicate that HBO3 in the catalyst system has great influence on the growth of MWCNTs.