Mapping aggregate transformations in dispersions with automated particle image analysis

• We propose ‘Size-Shape maps’ on size and shape distributions of CNT aggregates in dispersions made by particle image analysis. • Structural transformations of CNT aggregates can be traced from aligned CNT forests to mesh-like, isotropic structures by mapping. • Porous yet robust CNT films with high electrical conductivity and high specific surface area were demonstrated, elucidating correlations between the CNT aggregate structures in dispersions and the film properties. Carbon nanotube (CNT) aggregates in dispersions are widely utilized to produce the composites, fibers, and thick films, however, the relationship between the CNT aggregate morphology and the intrinsic CNT properties remains unclear. To elucidate this point, the morphology of thousands of CNT aggregates was characterized by particle image analysis from which we generated a map of aggregate size and shape distributions to describe and interpret the changing structures. Based on size and shape distributions, we classified the aggregate structures from aligned CNT forest into four groups: (1) macroclusters, (2) filaments, (3) mesh, and (4) fine particles. In this way, we demonstrated porous yet robust CNT films with high electrical conductivity and high specific surface area, elucidating correlations between the CNT aggregate structures in dispersions and the film properties. The CNT aggregate structures in different dispersion states were visualized using sizes and shapes for each of CNT aggregates. The structural transformations from as-grown aligned CNTs to mesh-like, isotropic aggregate structures could be accurately tracked. These findings can assist CNT users in identifying the most suitable CNT aggregate structures for their targeted applications.