Title: Measurement of the Dewetting, Nucleation, and Deactivation Kinetics of Carbon Nanotube Population Growth by Environmental Transmission Electron Microscopy

Abstract

Understanding the collective growth of carbon nanotube (CNT) populations is key to tailoring their properties for many applications. During the initial stages of CNT growth by chemical vapor deposition, catalyst nanoparticle formation by thin-film dewetting and the subsequent CNT nucleation processes dictate the CNT diameter distribution, areal density, and alignment. Here, in this study, we use in situ environmental transmission electron microscopy (E-TEM) to observe the catalyst annealing, growth, and deactivation stages for a population of CNTs grown from a thin-film catalyst. Complementary in situ electron diffraction and TEM imaging show that, during the annealing step in hydrogen, reduction of the iron oxide catalyst is concomitant with changes in the thin-film morphology; complete dewetting and the formation of a population of nanoparticles is only achieved upon the introduction of the carbon source, acetylene. The dewetting kinetics, i.e., the appearance of distinct nanoparticles, exhibits a sigmoidal (autocatalytic) curve with 95% of all nanoparticles appearing within 6 s. After nanoparticles form, they either nucleate CNTs or remain inactive, with incubation times measured to be as small as 3.5 s. Via E-TEM we also directly observe the crowding and self-alignment of CNTs after dewetting and nucleation. In addition, in situ electron energy lossmore » spectroscopy reveals that the collective rate of carbon accumulation decays exponentially. We conclude that the kinetics of catalyst formation and CNT nucleation must both be addressed in order to achieve uniform and high CNT density, and their transient behavior may be a primary cause of the well-known nonuniform density of CNT forests.« less

Authors:

Bedewy, Mostafa ^[1]; Viswanath, B. ^[2]; Meshot, Eric R. ^[3]; Zakharov, Dmitri N. ^[4]; Stach, Eric A. ^[4]; Hart, A. John ^[1]

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+ Show Author Affiliations

1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Univ. of Michigan, Ann Arbor, MI (United States)
2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Physical and Life Sciences Directorate
4. Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials

Publication Date:

Mon May 23 00:00:00 EDT 2016

Research Org.:

Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN); Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

1336127

Alternate Identifier(s):

OSTI ID: 1959600

Report Number(s):

BNL-112593-2016-JA; LLNL-JRNL-683473
Journal ID: ISSN 0897-4756

Grant/Contract Number:  

SC00112704; AC52-07NA27344; SC0004927

Resource Type:

Accepted Manuscript

Journal Name:

Chemistry of Materials

Additional Journal Information:

Journal Volume: 28; Journal Issue: 11; Journal ID: ISSN 0897-4756

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; carbon nanotubes; kinetics; catalysis; dewetting; electron microscopy; 77 NANOSCIENCE AND NANOTECHNOLOGY