约束型热等离子射流选择性制备单壁和套杯状多壁碳纳米管

Synthesis of singlewall and cupstacked carbon nanotubes by methane decomposition using constrained thermal plasma jet

以甲烷为碳源,Fe2O3为催化剂,常压下利用配有扰流器件(石墨碗)的约束型热等离子射流高温裂解甲烷,通过原位催化制得两类碳纳米管。运用SEM、TEM、TGA等对不同取样位置产物进行形貌和结构的表征。结果表明:在不同取样部位可获得不同形貌结构的碳纳米管。过滤管外壁处产物为单壁管,石墨碗内产物为套杯状多壁管。气体流动状态影响碳纳米管的形貌,经历层流的前驱物成为高度结晶单壁管,而经历湍流的前驱物则演变成套杯状多壁管。石墨碗腔内的局部高温可使多壁管不断增粗,有利于制备高纯度的碳纳米管。

Singlewall and cupstacked carbon nanotubes （CSCNTs） were synthesized by a constrained thermal plasma jet at atmospheric pressure using methane as carbon source and Fe2O3 as catalyst. The plasma jet flowed through a graphite cylinder directly into a graphite bowl where its flow was interrupted and carbon was deposited. Carbon was also deposited on a ceramic filter tube behind the bowl. Deposits at the two locations were characterized by scanning and transmission electron microscopy and differential thermal analysis. The carbon on the filter tube consisted of defectfree singlewalled CNTs （SWCNTs）, while that in the graphite bowl consisted of highpurity CSCNTs. Gas flow has a significant influence in the structure of the products. Highly crystalline SWCNTs were formed under laminar gas flow and the CSCNTs were produced under turbulent gas flow. Diameter and purity of the CSCNTs increases gradually toward the inner cavity of the graphite bowl due to a temperature increase.