Detecting Carbon Nanotube Orientation with Topological Data Analysis of Scanning Electron Micrographs

TL;DR

This paper introduces a novel topological data analysis method to quantify carbon nanotube orientation in SEM images, providing a rapid, robust, and accurate tool for assessing CNT alignment crucial for aerospace material development.

Contribution

The study develops a new TDA-based approach to detect CNT orientation from SEM images, validated against established techniques with high accuracy and robustness.

Findings

High correlation (R^2=0.975) with polarized Raman and X-ray scattering.

Method remains robust across different SEM settings.

Provides a quick, simple quantification of CNT alignment.

Abstract

As the aerospace industry becomes increasingly demanding for stronger lightweight materials, the ultra-strong carbon nanotube (CNT) composites with highly aligned CNT network structures could be the answer. In this work, a novel methodology applying topological data analysis (TDA) to the scanning electron microscope (SEM) images was developed to detect CNT orientation. The CNT bundle extensions in certain directions were summarized algebraically and expressed as visible barcodes. The barcodes were then calculated and converted into the total spread function $V(X,\theta)$, from which the alignment fraction and the preferred direction could be determined. For validation purposes, the random CNT sheets were mechanically stretched at various strain ratios ranging from $0-40\%$, and quantitative TDA analysis was conducted based on the SEM images taken at random positions. The results showed high consistency ($R^2=0.975$) compared to the Herman's orientation factors derived from the polarized Raman spectroscopy and wide-angle X-ray scattering analysis. Additionally, the TDA method presented great robustness with varying SEM acceleration voltages and magnifications, which might alter the scope in alignment detection. With potential applications in nanofiber systems, this study offers a rapid and simple way to quantify CNT alignment, which plays a crucial role in transferring the CNT properties into engineering products.