Increasing carbon nanotube forest density

Abstract

The outstanding mechanical, electrical, thermal, and morphological properties of individual carbon nanotubes (CNTs) open up exciting potential applications in a wide range of fields. One such application is replacing the standard activated carbon electrode in electrochemical double layer (EDLC) ultracapacitors with vertically aligned CNT forests (VACNTs). The specific capacitance of an EDLC scales with the specific surface area of the electrodes, thus this research seeks to increase the areal density of VACNTs, as areal density also scales with surface area. VACNT synthesis requires the preparation of a substrate with (typically iron) catalyst nanoparticles (NPs), which become nucleation sites for CNTs. This research was primarily focused on tuning the catalyst/substrate interfacial interactions in order to promote higher NP areal densities. A variety of density-enhancing procedures demonstrated in the literature were combined with a novel method of simultaneous deposition and NP formation in a series of experiments designed to increase CNT density. With these methods, CNT densities of 5x10¹¹ were achieved, approximately 5 times higher than the standard method for VACNT synthesis.