Analyzing the quality of carbon nanotube dispersions in polymers using scanning electron microscopy

Abstract

The ability to examine conducting filler particles in an insulating polymer matrix by scanning electron microscopy (SEM) was investigated. The detection of selected secondary electrons is necessary to resolve sub-micron scale filler particles, but not every SEM detector seems to be able to monitor the small changes introduced by the conducting filler particles. The influence of SEM parameters and the challenge of image interpretation in view of the apparent lack of appropriate information in literature are discussed. In accordance with other experiments on light element samples, all monitored electrons seem to be emitted within approximately 50 nm of the sample depth and no information is accessible from deeper regions even by increasing the acceleration voltage.

A review and analysis of electrical percolation in carbon nanotube polymer composites

“…From electron microscopy it became evident that CNT embedded in a polymer matrix generally are curved or wavy rather than straight [25]. The effect of waviness on percolation has been addressed by a couple of authors using different theoretical approaches [26]-29].…”

Evolution of carbon nanotube dispersion in preparation of epoxy-based composites: From a masterbatch to a nanocomposite

“…Charge contrast SEM images shown in Figure 7a and 7b can provide better visualization of the nanotubes within the epoxy matrix. In this technique the inherent difference between the charging potential of the conductive CNTs and the dielectric matrix will give rise to a charging contrast [12,20,35]. Using a right detector (as explained in the experimental section), such a contrast will make it possible to gain some insights into the placement of the nanoparticles embedded in the matrix.…”

“…Depending on the physical state of the system, various direct or indirect methods for the assessment of the CNT dispersion in epoxy based composites have been reported in the literature. Scanning and transmission electron microscopy are widely used to directly visualize CNT dispersion in the solid state [12][13][14][15]. Optical microscopy is also commonly used to observe larger CNT agglomerates both in liquid dispersions and solid nanocomposite films [9,[16][17][18][19].…”

Processing and Properties of Carbon Nanotube PVC Composites

“…In contrast to processing in low viscous media, such as water, the remaining agglomerates cannot be separated from the polymeric mass. Usual processes for the splitting of the agglomerates are sonification as well as calendering [6][7][8][9][10][11][12][13]. The maintenance of the high aspect ratio of the MWCNT is the most important criterion for the selection of the agglomerates.…”