Transitions of Aggregation States for Concentrated Carbon Nanotube Dispersion

Because of the lack of appropriate techniques for the measurement of concentrated dispersions, dispersion states of carbon nanotube (CNT) dispersions have been evaluated for dilute dispersions by assuming the dispersion state being unchanged by dilution. In this paper, it is clarified that this assumption does not hold true at a high concentration region by a direct measurement of size distribution and anisotropy for CNT dispersions in a wide concentration region. CNT dispersions showed a dispersion-state transition as a form of rotation restriction at a certain concentration. In addition to this, CNT dispersions whose solutes have a large specific surface area showed another dispersion-state transition at a certain concentration as a form of aggregation growth. To prove these dispersion-state transitions from another point of view, the difference in sheet resistance of conducting layers made from different CNT dispersions coated on a glass substrate was investigated. It was confirmed that their sheet resistance also showed a clear difference. This difference can be explained from the viewpoint of dispersion-state transitions induced by the drying process

Mechanically Durable and Highly Conductive Elastomeric Composites from Long Single-Walled Carbon Nanotubes Mimicking the Chain Structure of Polymers

By using long single-walled carbon nanotubes (SWNTs) as a filler possessing the highest aspect ratio and small diameter, we mimicked the chain structure of polymers in the matrix and realized a highly conductive elastomeric composite (30 S/cm) with an excellent mechanical durability (4500 strain cycles until failure), far superior to any other reported conductive elastomers. This exceptional mechanical durability was explained by the ability of long and traversing SWNTs to deform in concert with the elastomer with minimum stress concentration at their interfaces. The conductivity was sufficient to operate many active electronics components, and thus this material would be useful for practical stretchable electronic devices

Classification of Commercialized Carbon Nanotubes into Three General Categories as a Guide for Applications

We propose a general guideline for the application of commercialized carbon nanotubes (CNTs) by making correlations between the structures and properties for various single-walled, double-walled, and multiwalled CNTs. On the basis of these correlations, three general categories emerged: (1) low crystallinity and low specific surface area (SSA; large-diameter multiwalled CNTs); (2) low crystallinity and high SSA (large-diameter single- and double-walled CNTs); (3) high crystallinity and moderate SSA (small-diameter single-walled CNTs). This categorization would accelerate the industrialization of CNTs by easily identifying the suitable CNTs for a given application

Green, Scalable, Binderless Fabrication of a Single-Walled Carbon Nanotube Nonwoven Fabric Based on an Ancient Japanese Paper Process

We propose a fabrication method for carbon nanotube (CNT) nonwoven fabrics based on an ancient Japanese papermaking process where paper is made from natural plant fibers. In our method, CNT nonwoven fabrics are made by a scalable process of filtering binder-free, aqueous suspensions of CNTs. The aqueous suspension of these entangled single-walled carbon nanotube (SWNT) aggregates enabled smooth filtration through a cellulose filter with large pores (8 μm). The “wet SWNT cakes,” which were composed solely of SWNT and water and obtained after filtration, were press-dried to fabricate an SWNT nonwoven fabric. This environmentally friendly process employs water and the raw CNT material alone. Moreover, the scalability of this process was demonstrated by manufacturing a large area (A3, 30 × 42 cm; thickness: 40–150 μm), self-supporting SWNT nonwoven fabric with a density of 0.4 g/cm³, a basis weight of 0.2 g/m² , a porosity of 63%, and a specific surface area of 740 m²/g. This SWNT nonwoven fabric is anticipated to find application as functional particle-supported sheets, electrode materials, and filters