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Title: In situ time-resolved measurements of carbon nanotube and nanohorn growth

Abstract

Growth mechanisms of carbon nanotubes are investigated and compared for both high- and low-temperature synthesis methods through experiments utilizing time-resolved, in situ imaging and spectros-copy. High-speed videography and pyrometry measured the timeframes for growth for single-wall car-bon nanotubes (SWNTs) and nanohorns (SWNHs) by laser vaporization (LV) at 1150 C, revealing that C can self-assemble at high temperatures preferentially into SWNH structures without catalyst assistance at rates comparable to catalyst-assisted SWNT growth by either laser vaporization or chemical vapor depo-sition (CVD). Laser interferometry and videography reveal the coordinated growth of vertically-aligned nanotube arrays (VANTAs) by CVD at 550-900 C.

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Center for Nanophase Materials Sciences
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE); USDOE Office of Science (SC)
OSTI Identifier:
1018568
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physica Status Solidi B; Journal Volume: 244; Journal Issue: 11
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CARBON; CATALYSTS; CHEMICAL VAPOR DEPOSITION; EVAPORATION; INTERFEROMETRY; LASERS; NANOTUBES; SPECTROSCOPY; SYNTHESIS; Single-wall carbon nanotubes; growth mechanisms; in situ diagnostics.

Citation Formats

Geohegan, David B, Puretzky, Alexander A, Styers-Barnett, David J, Hu, Hui, Zhao, Bin, Cui, Hongtao, Rouleau, Christopher M, Eres, Gyula, Jackson, Jeremy Joseph, Wood, Richard F, Pannala, Sreekanth, and Wells, Jack C. In situ time-resolved measurements of carbon nanotube and nanohorn growth. United States: N. p., 2007. Web. doi:10.1002/pssb.200776204.
Geohegan, David B, Puretzky, Alexander A, Styers-Barnett, David J, Hu, Hui, Zhao, Bin, Cui, Hongtao, Rouleau, Christopher M, Eres, Gyula, Jackson, Jeremy Joseph, Wood, Richard F, Pannala, Sreekanth, & Wells, Jack C. In situ time-resolved measurements of carbon nanotube and nanohorn growth. United States. doi:10.1002/pssb.200776204.
Geohegan, David B, Puretzky, Alexander A, Styers-Barnett, David J, Hu, Hui, Zhao, Bin, Cui, Hongtao, Rouleau, Christopher M, Eres, Gyula, Jackson, Jeremy Joseph, Wood, Richard F, Pannala, Sreekanth, and Wells, Jack C. Mon . "In situ time-resolved measurements of carbon nanotube and nanohorn growth". United States. doi:10.1002/pssb.200776204.
@article{osti_1018568,
title = {In situ time-resolved measurements of carbon nanotube and nanohorn growth},
author = {Geohegan, David B and Puretzky, Alexander A and Styers-Barnett, David J and Hu, Hui and Zhao, Bin and Cui, Hongtao and Rouleau, Christopher M and Eres, Gyula and Jackson, Jeremy Joseph and Wood, Richard F and Pannala, Sreekanth and Wells, Jack C},
abstractNote = {Growth mechanisms of carbon nanotubes are investigated and compared for both high- and low-temperature synthesis methods through experiments utilizing time-resolved, in situ imaging and spectros-copy. High-speed videography and pyrometry measured the timeframes for growth for single-wall car-bon nanotubes (SWNTs) and nanohorns (SWNHs) by laser vaporization (LV) at 1150 C, revealing that C can self-assemble at high temperatures preferentially into SWNH structures without catalyst assistance at rates comparable to catalyst-assisted SWNT growth by either laser vaporization or chemical vapor depo-sition (CVD). Laser interferometry and videography reveal the coordinated growth of vertically-aligned nanotube arrays (VANTAs) by CVD at 550-900 C.},
doi = {10.1002/pssb.200776204},
journal = {Physica Status Solidi B},
number = 11,
volume = 244,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Here, the 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.more » 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. As a result, 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.« less
  • No abstract prepared.
  • Abstract not provided.
  • Direct measurements of carbon nanotube growth kinetics are described based upon time-resolved reflectivity (TRR) of a HeNe laser beam from vertically aligned nanotube arrays (VANTAs) as they grow during chemical vapor deposition (CVD). Growth rates and terminal lengths were measured in situ for VANTAs growing during CVD between 535 C and 900 C on Si substrates with evaporated Al/Fe/Mo multi-layered catalysts and acetylene feedstock at different feedstock partial pressures. Methods of analysis of the TRR signals are presented to interpret catalyst particle formation and oxidation, as well as the porosity of the VANTAs. A rate-equation model is developed to describemore » the measured kinetics in terms of activation energies and rate constants for surface carbon formation and diffusion on the catalyst nanoparticle, nanotube growth, and catalyst over-coating. Taken together with the TRR data, this model enables basic understanding and optimization of growth conditions for any catalyst/feedstock combination. The model lends insight into the main processes responsible for the growth of VANTAs, the measured number of walls in the nanotubes at different temperatures, conditions for growth of single-wall carbon nanotube arrays, and likely catalyst poisoning mechanisms responsible for the sharp decline in growth rates observed at high temperatures.« less