Graphene sheets nanotubes made from

Nanotubes of carbon are made from graphene-like sheets roUed into a tube. Carbon nanotubes are considered to be the strongest and stifFest materials yet discovered in terms of tensile strength and elastic modulus, respectively. This strength results from the covalent sp bonds formed between the individual carbon atoms. 

Then there are the nanombes, some with closed ends, as well as nanorods (Qian et al., 2003 Yudasaka et al., 2003). These are made up of rolled graphene sheets, with five-membered rings to accommodate the strains involved. The internal diameters of these nanombes range from =0.7 nm into the mesopore range >2.0 nm for multi-walled nanotubes (Figure 2.42(a)). 

Since 1976, studies on the thermal treatment of hydrocarbons (CVD) allowed researchers to isolate and observe long fibers and filaments (hollow fibers), carbon of several micrometers in length, but with very small diameter. However, this discovery made jointly by French and Japanese researchers [26] had a limited impact because the crystalline structure of these objects was inaccessible. In the early 90s, another Japanese team from NEC Labs proposed the helical structure of carbon nanocylinders (Fig. 5. If), which was quickly confirmed by several teams around the world [1]. In 1993, tubes with almost no thickness (formed from a single sheet of graphene) were synthesized, isolated and analyzed [27]. These were named single-wall carbon nanotubes (SWNT) because of their nanometer diameter. 

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