In Situ Mechanochemical Modulation of Carbon Nanotube Forest Growth

Nicholas T. Dee, Mostafa Bedewy, Abhinav Rao, Justin Beroz, Byeongdu Lee, Eric R. Meshot, Cécile A.C. Chazot, Piran R. Kidambi, Hangbo Zhao, Thomas Serbowicz, Kendall Teichert, Prashant K. Purohit, A. John Hart*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Ordered synthesis of one-dimensional nanostructures, such as carbon nanotubes (CNTs), involves competition between the growth kinetics of individual structures, their physical entanglement, and intermolecular forces that cause coupling of structures in close proximity. Specifically, CNT synthesis by chemical vapor deposition can directly produce films and fibers by providing CNT growth sites in close proximity such that the CNTs self-align into macroscopic assemblies. Because CNTs are mechanically coupled during these processes, the question arises as to whether or not mechanical forces intrinsic to the formation of CNT ensembles influence the growth kinetics and quality of CNTs, as can be expected from fundamental theories of mechanochemistry. Here, we study how mechanical forces influence CNT growth by applying controlled compression to CNT forests in situ; and relate the outcomes quantitatively to the CNT morphology and lengthening rate. We find that applied forces inhibit the self-organization of CNTs into a forest and accelerate the termination of collective growth. By correlating in situ kinetics measurements with spatial mapping of CNT orientation and density by X-ray scattering, we find that the average growth rate of individual CNTs is also mechanically modulated; specifically, a 100-fold increase in force causes a 4-fold decrease in average CNT lengthening rate. We attribute the slower growth kinetics to a stress-dependent increase of 0.02-0.16 eV in the effective activation energy for CNT growth. Via finite element modeling, we conclude that the force magnitudes that cause remodeling of the growing CNT network are less than the average strengths of adhesive contacts between CNTs. Last, we find that CNT growth rate and orientation can respond dynamically to changes in applied force, further demonstrating the mechanochemical nature of CNT growth and suggesting new approaches to control CNT quality and morphology in situ, with general application to other one-dimensional nanostructures.

Original languageEnglish (US)
Pages (from-to)407-418
Number of pages12
JournalChemistry of Materials
Volume31
Issue number2
DOIs
StatePublished - Jan 22 2019

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Materials Chemistry

Fingerprint

Dive into the research topics of 'In Situ Mechanochemical Modulation of Carbon Nanotube Forest Growth'. Together they form a unique fingerprint.

Cite this