An infinite nanotube that is of the zigzag (or armchair) type consists entirely of closed zigzag (or armchair) paths, connected to each other. If the tube is instead encircled by a closed armchair path, it is said to be of the armchair type, or an armchair nanotube. One says that the tube is of the zigzag type or configuration, or simply is a zigzag nanotube. On some carbon nanotubes, there is a closed zigzag path that goes around the tube. It is also conventional to define an armchair path as one that makes two left turns of 60 degrees followed by two right turns every four steps. In the study of nanotubes, one defines a zigzag path on a graphene-like lattice as a path that turns 60 degrees, alternating left and right, after stepping through each bond. Since the length of the carbon-carbon bonds is fairly fixed, there are constraints on the diameter of the cylinder and the arrangement of the atoms on it. The structure of an ideal (infinitely long) single-walled carbon nanotube is that of a regular hexagonal lattice drawn on an infinite cylindrical surface, whose vertices are the positions of the carbon atoms. The basis vectors u and v of the relevant sub-lattice, the (n,m) pairs that define non-isomorphic carbon nanotube structures (red dots), and the pairs that define the enantiomers of the chiral ones (blue dots) These discoveries triggered research that succeeded in greatly increasing the efficiency of the catalytic production technique, and led to an explosion of work to characterize and find applications for SWCNTs. at IBM independently discovered in 1993 that co-vaporizing carbon and transition metals such as iron and cobalt could specifically catalyze SWCNT formation.
Iijima and Ichihashi at NEC and Bethune et al. These properties are expected to be valuable in many areas of technology, such as electronics, optics, composite materials (replacing or complementing carbon fibers), nanotechnology, and other applications of materials science.Ī path to synthesizing carbon nanotubes was lacking until the 1990s.
In addition, they can be chemically modified. Some carbon nanotube structures exhibit high electrical conductivity while others are semiconductors. Multi-wall carbon nanotubes are also sometimes used to refer to double- and triple-walled carbon nanotubes.Ĭarbon nanotubes can exhibit remarkable properties, such as exceptional tensile strength and thermal conductivity because of their nanostructure and strength of the bonds between carbon atoms. Multi-walled carbon nanotubes ( MWCNTs) consist of nested single-wall carbon nanotubes in a nested, tube-in-tube structure. They can be idealized as cutouts from a two-dimensional graphene sheet rolled up to form a hollow cylinder. Single-walled carbon nanotubes ( SWCNTs) have diameters around 0.5–2.0 nanometers, about 100,000 times smaller than the width of a human hair. They are one of the allotropes of carbon. A carbon nanotube ( CNT) is a tube made of carbon with a diameter in the nanometer range ( nanoscale).
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