Open-Ended Aligned Carbon Nanotube Arrays Produced Using CO2-Assisted Floating-Ferrocene Chemical Vapor Deposition

The influence of CO2, in concentrations of up to 7600 ppm, on the preparation of aligned carbon nanotube (CNT) arrays from ethylene using floating-ferrocene chemical vapor deposition (CVD) at 750 degrees C was investigated. The CO2-assisted floating-ferrocene CVD method facilitates the well-controlled growth of aligned CNT arrays; the quality of the aligned CNT arrays was significantly improved in the presence of CO2 as demonstrated by improved alignment and crystallinity. Under the assistance of CO2, CNT arrays were linear and vertical. CNTs grown with CO2 were also higher than those grown in the absence of CO2, with the optimum CO2 concentration of 760 ppm producing a 50% enhancement in CNT height. Varying the concentration of CO2 also controlled the diameter and wall numbers of the aligned CNTs. CNTs synthesized in the presence of 7600 ppm CO2 had a diameter of 8.0 +/- 1.6 nm, and an average wall number of 4 +/- 1. In particular, both open-ended and triple-walled CNTs were clearly observed.