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Quantifying alignment in carbon nanotube yarns and similar two-dimensional anisotropic systems

Published version
Peer-reviewed

Type

Article

Change log

Abstract

jats:titleAbstract</jats:title>jats:pThe uniaxial orientational order in a macromolecular system is usually specified using the Hermans factor which is equivalent to the second moment of the system's orientation distribution function (ODF) expanded in terms of Legendre polynomials. In this work, we show that for aligned materials that are two‐dimensional (2D) or have a measurable 2D intensity distribution, such as carbon nanotube (CNT) textiles, the Hermans factor is not appropriate. The ODF must be expanded in terms of Chebyshev polynomials and therefore, its second moment is a better measure of orientation in 2D. We also demonstrate that both orientation parameters (Hermans in three dimensional (3D) and Chebyshev in 2D) depend not only on the respective full‐width‐at‐half‐maximum of the peaks in the ODF but also on the shape of the fitted functions. Most importantly, we demonstrate a method to rapidly estimate the Chebyshev orientation parameter from a sample's 2D Fourier power spectrum, using an analysis program written in Python which is available for open access. As validation examples, we use digital photographs of dry spaghetti as well as scanning electron microscopy images of direct‐spun carbon nanotube fibers, proving the technique's applicability to a wide variety of fibers and images.</jats:p>

Description

Keywords

fibers, films, graphene and fullerenes, nanotubes, structure&#8208, property relationships

Journal Title

Journal of Applied Polymer Science

Conference Name

Journal ISSN

0021-8995
1097-4628

Volume Title

138

Publisher

Wiley
Sponsorship
Engineering and Physical Sciences Research Council (EP/M02086X/1)
Engineering and Physical Sciences Research Council (EP/M015211/1)