nn6b07251_si_004.avi (37.32 MB)
Real-Time Imaging of Self-Organization and Mechanical Competition in Carbon Nanotube Forest Growth
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posted on 2016-11-23, 00:00 authored by Viswanath Balakrishnan, Mostafa Bedewy, Eric R. Meshot, Sebastian W. Pattinson, Erik S. Polsen, Fabrice Laye, Dmitri N. Zakharov, Eric A. Stach, A. John HartThe
properties of carbon nanotube (CNT) networks and analogous
materials comprising filamentary nanostructures are governed by the
intrinsic filament properties and their hierarchical organization
and interconnection. As a result, direct knowledge of the collective
dynamics of CNT synthesis and self-organization is essential to engineering
improved CNT materials for applications such as membranes and thermal
interfaces. Here, we use real-time environmental
transmission electron microscopy (E-TEM) to observe nucleation and
self-organization of CNTs into vertically aligned forests. Upon introduction
of the carbon source, we observe a large scatter in the onset of nucleation
of individual CNTs and the ensuing growth rates. Experiments performed
at different temperatures and catalyst particle densities show the
critical role of CNT density on the dynamics of self-organization;
low-density CNT nucleation results in the CNTs becoming pinned to
the substrate and forming random networks, whereas higher density
CNT nucleation results in self-organization of the CNTs into bundles
that are oriented perpendicular to the substrate. We also find that
mechanical coupling between growing CNTs alters their growth trajectory
and shape, causing significant deformations, buckling, and defects
in the CNT walls. Therefore, it appears that CNT–CNT coupling
not only is critical for self-organization but also directly influences
CNT quality and likely the resulting properties of the forest. Our
findings show that control of the time-distributed kinetics of CNT
nucleation and bundle formation are critical to manufacturing well-organized
CNT assemblies and that E-TEM can be a powerful tool to investigate
the mesoscale dynamics of CNT networks.
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CNT wallsgrowth ratesgrowth trajectoryfilamentary nanostructuresmesoscale dynamicscarbon nanotubeMechanical Competitioncatalyst particle densities showCNT synthesiscarbon sourceCNT networksReal-Time ImagingCNT nucleationtime-distributed kineticsCarbon Nanotube Forest GrowthCNT densityfilament propertiestransmission electron microscopyCNT materialsdensity CNT nucleation resultsinfluences CNT qualityE-TEMbundle formationCNT assembliesCNT nucleation resultsfindings show
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