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Nanotubes

Go to:  What is a nanotube?  Nanotubes @ Nano-C

What Is A Nanotube?

Single- and multi-walled carbon nanotubes.

Carbon nanotubes (CNTs) may have been observed as early as the 1950s as filamentary carbon structures, or fibers. In 1991, Sumio Iijima, a researcher at the NEC Laboratory in Japan, observed that these fibers were hollow. The diameter of a nanotube is on the order of one nanometer, many times smaller than the width of a human hair, but up to several microns long. CNTs come in two principal forms, single-walled carbon nanotubes (SWCNT) and multi-walled (MWCNT), as pictured here. Although not a hollow tube, carbon nanofibers (CNF) represent a third type of tubular structure.

Conceptually, the structure of a SWCNT is a one-atom-thick layer of graphite, called graphene, wrapped into a seamless cylinder with either open or closed ends. As their name implies, MWCNTs consist of multiple concentric layers of graphene that form a tube shape.

By themselves, CNTs can be conducting or semi-conducting, and are uniquely strong. The many applications for CNTs are based on their unique structure, although some can use either MWCNTs or SWCNTs. MWCNTs are used today in conducting polymers; for example, in electrostatic spray operations. Due to their unique features, SWCNT are required for some key electronic applications such as memory, semiconductor components and transparent conducting films for touch screens, displays, solar cells and other devices.

Nanotubes @ Nano-C

Combustion-based production and sales of single-walled carbon nanotubes (SWCNT) represents the second of two major axes of Nano-C's activities. Currently we offer 2 SWCNT products:

• As-Produced (≥ 70% SWCNT)
• Purified (≥ 95% SWCNT)

       Nanotubes

In contrast to fullerenes and their derivatives, which are well defined chemical compounds containing a given number of atoms, nanotubes made under different conditions afforded by a given process usually produce a range of diameters, lengths and physical properties. For this reason, the development of specific applications depends on the characteristics of the nanotube production process, i.e., the optimization of their functionality is closely linked to the adjustment of conditions in the nanotube manufacturing process. Nano-C’s as-produced and purified SWCNT are available as dispersions or inks, as further discussed below.

We characterize our SWCNTs by means of:

• RAMAN spectroscopy suitable for the quick and reliable screening of the presence of SWCNT


• Transmission electron microscopy (TEM) allowing for the assessment of detailed structures


• Scanning electron microscopy (SEM) providing overviews of sample structures while less sensitive to sample preparation and homogeneity than TEM


• Thermogravimetric analysis (TGA) giving information about relative abundance of catalyst particles, nanotubes and other carbonaceous structures


• Elemental analysis assessing the contribution of the catalyst particles and hydrocarbons to the total sample mass


• Absorption spectroscopy (UV-vis/NIR)allowing for the assessment of the abundance of SWCNT relative to other carbonaceous material that may be present and key performance attributes such as their electronic integrity

We determine the length distribution of our SWCNT by means of SEM and by atomic force microscopy (AFM).

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