Porosity control of CNT aerogel and its conversion to CNT fiber in floating catalyst chemical vapour deposition

Carbon nanotube aerogel (CNT aerogel), a self-assembled 3D structure of long CNTs, has gained attraction as the exotic properties of individual CNTs can be potentially translated into the macro dimension through this structure. The present work reports how S/Fe ratio in the feedstock controls the density and pore-structure of the self-assembled CNT aerogel in floating catalyst chemical vapor deposition (FC-CVD). The density of the aerogel increases with the decrease in the S/Fe ratio. Small-angle scattering (SAS) and scanning electron microscopy (SEM) suggest the decrease in porosity and increase in bundle dimensions with the decrease in S/Fe ratio. Raman spectroscopy and transmission electron microscopy (TEM) depict that the CNTs are multi-walled in nature at the processing conditions employed, and the crystallinity improves with an increase in the S/Fe ratio. Early re-nucleation and increase in nucleation density of catalysts with a higher S/Fe ratio have been proposed to produce CNT aerogel with lesser density. The formed aerogels were converted into CNT fibers and a maximum electrical conductivity of 1.02 +/- 0.19 M Sm-1 and tensile strength of 308.56 +/- 24.6 MPa were obtained with S/Fe ratio of 0.2.