title: The Evolution of Carbon Nanotube Network Structure in Unidirectional Nanocomposites Resolved by Quantitative Electron Tomography.
abstract: Carbon nanotube (CNT) reinforced polymers are next-generation, high-performance, multifunctional materials with a wide array of promising applications. The successful introduction of such materials is hampered by the lack of a quantitative understanding of process-structure-property relationships. These relationships can be developed only through the detailed characterization of the nanoscale reinforcement morphology within the embedding medium. Here, we reveal the three-dimensional (3D) nanoscale morphology of high volume fraction (V(f)) aligned CNT/epoxy-matrix nanocomposites using energy-filtered electron tomography. We present an automated phase-identification method for fast, accurate, representative rendering of the CNT spatial arrangement in these low-contrast bimaterial systems. The resulting nanometer-scale visualizations provide quantitative information on the evolution of CNT morphology and dispersion state with increasing V(f), including network structure, CNT alignment, bundling and waviness. The CNTs are observed to exhibit a nonlinear increase in bundling and alignment and a decrease in waviness as a function of increasing V(f). Our findings explain previously observed discrepancies between the modeled and measured trends in bulk mechanical, electrical and thermal properties. The techniques we have developed for morphological quantitation are applicable to many low-contrast material systems.
authors.affiliation: †Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.|§Maryland Nanocenter, University of Maryland, College Park, Maryland 20740, United States.
authors.forename: Bharath
authors.initials: B
authors.lastname: Natarajan
authors.affiliation: ‡Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
authors.forename: Noa
authors.initials: N
authors.lastname: Lachman
authors.affiliation: †Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.
authors.forename: Thomas
authors.initials: T
authors.lastname: Lam
authors.affiliation: ∥Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
authors.forename: Douglas
authors.initials: D
authors.lastname: Jacobs
authors.affiliation: †Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.|§Maryland Nanocenter, University of Maryland, College Park, Maryland 20740, United States.
authors.forename: Christian
authors.initials: C
authors.lastname: Long
authors.affiliation: †Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.
authors.forename: Minhua
authors.initials: M
authors.lastname: Zhao
authors.affiliation: ‡Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
authors.forename: Brian L
authors.initials: BL
authors.lastname: Wardle
authors.affiliation: †Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.
authors.forename: Renu
authors.initials: R
authors.lastname: Sharma
authors.affiliation: †Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.
authors.forename: J Alexander
authors.initials: JA
authors.lastname: Liddle
keywords: carbon nanotubes; electron tomography; image analysis; nanocomposites; nanostructure