Resolving Hierarchical Structures in Carbon Nanotube Networks Using Small- and Ultrasmall-Angle Neutron Scattering

Abstract

Resolving hierarchical structures in carbon nanotube (CNT) composites is crucial for their processing and performance optimization. We report here that self-consistent analyses of small- and ultrasmall-angle neutron scattering (SANS and USANS, respectively) patterns can be used to extract both the size and morphology of the hierarchical structures in carbon nanotube networks. In particular, this study investigates the correlation of structure and electrical conductivity of CNT-PEDOT:PSS (poly­(3,4-ethylene­dioxythiophene):poly­(styrene­sulfonate)) composite films where distinguishable dispersion states of nanotubes in the PEDOT:PSS matrix were achieved by varying the CNT concentration, duration of sonication, and addition of ethylene glycol (EG) to the predeposition solutions. It was concluded that five hierarchical levels of structure, spanning a few nanometers to tens of micrometers, exist in all samples. The results suggest a strong variation in the structure of the nanocomposites at larger length scales and, to a lesser extent, at smaller length scales with the variation in processing. Electrical conductivity of samples was largely affected by the morphological changes at larger scales. The EG addition affected the electrical conductivity by both increasing the matrix conductivity and improving CNT dispersion. The presented analysis is also useful for the characterization of structures in pure CNT and low CNT composite samples.

A review of the interfacial characteristics of polymer nanocomposites containing carbon nanotubes

“…42 Microscopy and scattering techniques can provide a quantitative description of the morphology of polymer nanocomposite materials, and they are complementary for structural characterization. [43][44][45][46] Transmission electron microscopy and scanning electron microscopy techniques can be used to characterize the microstructural features of nanocomposite materials, such as the dispersion state of carbon nanotubes in polymer matrices and the magnitude of the interfacial adhesion between them. 47 Other important factors such as the alignment of carbon nanotubes in the polymer matrix, as well as other common analyses involving distribution and quantication of the dimension of carbon nanotubes can also be explored by using these electron microscopy methods.…”

Toward Scalable Manufacturing of Carbon Nanotube Coated Conductors

“…The denser and more uniform coatings formed over the length of the copper wire (Figure ) are attributed to the elimination of interfibril voids upon die drawing. Neutron or X-ray scattering can reveal the internal structure of the CNT coatings; , however, such detailed study of the hierarchical CNT structures was outside the scope of this study.…”

Studies of Fractal Microstructure in Nanocarbon Polymer Composites

“…The optimal version is a uniform dispersion of nanoparticles, but experimental studies suggest an inhomogeneous distribution of nanocarbon reinforcement. Data from small-angle X-ray (SAXS) and neutron scattering [29,30] in epoxy-carbon composites as well as direct observations of the microstructure on sample cuts using scanning electron microscopy (SEM) [26][27][28] show that the carbon reinforcement is distributed throughout the composite volume in the form of fractal nanoparticle aggregates.…”