Growth mechanism and kinetics of vertically aligned carbon nanotube arrays

Abstract

Carbon nanotubes (CNTs) exhibit excellent mechanical, electrical, thermal, and chemical properties and show promising application potentials in numerous fields. Among different types of CNTs, vertically aligned CNT arrays (VACNTs) exhibit more superiors due to their good alignment, controllable structures and morphologies, and easy mass‐production, and so forth. During the past years, extensive efforts were put into the controlled synthesis of VACNTs with desired structures and morphologies. Among these efforts, it should be noted that, it is of significant importance to improve the array lengths of VACNTs, especially for the fabrication of VACNTs‐based fibers, transparent flexible films, and other functional materials, and so forth. However, it still remains a big challenge to synthesize VACNTs with length over centimeters. In this review, we summarize the growth mechanism, kinetics, growth factors of VACNTs, and the strategies for how to improve their array lengths. Finally, we also propose our outlook on the future development of VACNTs.

Conducting Interface for Efficient Growth of Vertically Aligned Carbon Nanotubes: Towards Nano-Engineered Carbon Composite

“…Part of many reasons for the distortion of the above-mentioned catalyst properties could be the subsurface diffusion within the support layer. The activity and lifespan of CNT catalysts can also be impacted via the Ostwald ripening effect (i.e., regrouping of nanosize catalyst particles giving rise to larger ones) due to the morphology/structure of the used template [8,32,33]. Thus, the former discoveries underline the importance of the choice of catalyst and substrate, with-/-out interface layers, for the growth of VACNT.…”

“…Although beneficial for the homogeneous deposition of catalyst nanoparticles/growth of mm scale VACNT, most of the DBL used to date (such as Al 2 O 3 , SiO 2 , or MgO) [33,35,57,58] are generally insulators that limit the conducting contact between the VACNT and the substrate [59][60][61]. Unlike insulating DBL materials, semi-/-conducting DBLs show higher activity with the catalyst layer, such as interdiffusion and alloy formation that further affects the dewetting of the catalyst layer into a dense network of nanoparticles [62].…”

Quartz Nonadherent and Clean Exfoliation of the Heteroatom-Doped Bulk Carbon Nanotubes Array

“…Among them, FCCVD method provides a simpler and more cost-effective approach for mass production of CNTs array, for which FCCVD method enables the continuous growth of CNTs array directly from the gas phase onto a substrate by introducing the catalyst precursor and carbon source simultaneously. 14,17 The commonly selected substrates 1,18,19 for CNTs array growth in CVD method mainly are quartz, silicon wafers, and metal-based substrates, etc. However, the critical step in utilizing CNTs array for extensive applications is to achieve complete exfoliation from the substrate and keep the vertical structure unchanged.…”

“…However, CNTs are known to have extremely high stiffness and axial strength owing to the carbon−carbon sp 2 bonding. 31,32 The interaction between the CNTs array and quartz substrate is the driving force for the self-orientation of CNTs longitudinal direction into an aligned array structure, 19 which also leads to closely contact with the quartz surface with strong van der Waals (vdW) forces. Because of this, the original structures of the CNTs array and quartz substrate tend to be destroyed or contaminated during the exfoliation procedures.…”

“…The commonly selected substrates ,, for CNTs array growth in CVD method mainly are quartz, silicon wafers, and metal-based substrates, etc. However, the critical step in utilizing CNTs array for extensive applications is to achieve complete exfoliation from the substrate and keep the vertical structure unchanged.…”