Investigation of defectiveness of multiwalled carbon nanotubes produced with Fe–Co catalysts of different composition

Abstract

We have performed a study of CVD multiwalled carbon nanotubes (MWCNTs) produced with Fe–Co catalysts with a variable ratio of active metals. The Raman data were considered in combination with the temperature dependence of MWCNT conductivity. The data analysis is based on the point that the value of I2D/ID ratio correlates with the graphene fragment size. The fragments are considered as building blocks of MWCNTs. We showed that MWCNT defectiveness depends on the ratio of bimetallic active components in the Fe–Co catalyst. Thus, the ratio of I2D/ID increases and the D-mode intensity decreases while the Fe content in the catalyst increases. This also points to the reduction of defect number in the bigger graphene fragments. These results correlate with the data on conductivity temperature dependence. Namely, the increase of Fe content in the active component of the Fe–Co catalyst results in the increase of charge carrier concentration, which, in turn, indicates a decrease in MWCNT defectiveness.