Morphological Characterization of Carbon Nanotubes and Their Agglomeration Behavior Revealed by Scanning Electron Microscopy

In this study, the microscopic morphology and agglomeration behavior of carbon nanotubes (CNTs) were systematically investigated using high-resolution scanning electron microscopy (SEM). The SEM analysis revealed that CNTs predominantly exist in the form of irregular, spherical or quasi-spherical macroscopic aggregates, composed of densely entangled, curved, and flexible nanotubes. These aggregates exhibit a porous nanonetwork structure, rather than solid dense blocks, due to the random stacking and bending of individual CNTs. In addition to the major agglomerates, partially dispersed nanotubes were clearly observed at the periphery and in the interstitial spaces between aggregates, forming sparse and loosely connected nanonetworks. These morphological characteristics highlight the intrinsically high surface energy of CNTs and the strong van der Waals forces that drive their aggregation—a phenomenon that presents a critical challenge for achieving uniform dispersion in practical applications. Poor dispersion can severely hinder the mechanical reinforcement, electrical conductivity, and accessible surface area of CNTs in host materials, limiting their effectiveness in various functional systems. The insights gained from this detailed morphological analysis provide direct empirical evidence for the hierarchical structure of CNT agglomerates and the existence of inter-aggregate networks. These findings lay a solid foundation for understanding the complex relationship between the microstructural organization of CNTs and their macroscopic behavior. Furthermore, the results offer valuable guidance for the rational design of advanced dispersion techniques and integration strategies, aiming to fully exploit the exceptional properties of CNTs in fields such as polymer nanocomposites, energy storage and conversion, biomedical engineering, and environmental applications.