Both tips of MWCNT usually have closed and the ends are capped by dome-shaped half-fullerene molecules (pentagonal defects), and axial size differs from 1 μm up to a few centimeter. ĭepending on the number of layers, the inner diameter of MWCNTs diverges from 0.4 nm up to a few nanometers and outer diameter varies characteristically from 2 nm up to 20 to 30 nm. The real-space analysis of multiwall nanotube images has shown a range of interlayer spacing (0.34 to 0.39 nm). A few to a few tens of concentric cylinders with the regular periodic interlayer spacing locate around ordinary central hollow and made MWCNTs. The sp 2 hybridization of carbon builds a layered construction with weak out-of-plane bonding of the van der Waals form and strong in-plane bounds. Nanotubes with single well are described as single-wall carbon nanotubes (SWCNTs) and were first reported in 1993, while the ones with more than one well are multiwall carbon nanotubes (MWCNTs) and were first discovered in 1991 by Iijima (Figure 1).įull size image Carbon nanotubes: structure and propertiesĬarbon can bond in different ways to construct structures with completely different properties. It can divide into a single well or multiple wells. Carbon nanotube is theoretically distinct as a cylinder fabricated of rolled up grapheme sheet. In graphene, carbon atoms are densely organized in a regular sp 2-bonded atomic-scale honeycomb (hexagonal) pattern, and this pattern is a basic structure for other sp 2 carbon bonded materials (allotropes) such as fullerenes and carbon nanotubes. Most of the physical properties of carbon nanotubes derive from graphene. Discoveries of very constant nanometer size sp 2 carbon bonded materials such as graphene, fullerenes, and carbon nanotubes have encouraged to make inquiries in this field. It can hybridize in sp, sp 2, or sp 3 forms. Carbon is the chemical element with atomic number 6 and has six electrons which occupy 1 s 2, 2 s 2, and 2p 2 atomic orbital.
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