Carbon Nanotubes (CNT)
Carbon nanotubes(CNTs) are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1, significantly larger than for any other material. These cylindrical carbon molecules have unusual properties, which are valuable for nanotechnology, electronics, optics and other fields of materials science and technology. In particular, owing to their extraordinary thermal conductivity and mechanical and electrical properties, carbon nanotubes find applications as additives to various structural materials. For instance, in (primarily carbon fiber) "baseball bats, car parts" and even "golf clubs”, where nanotubes form only a tiny portion of the material(s).
Nanotubes are members of the fullerene structural family, which also includes the spherical buckyballs, and the ends of a nanotube may be capped with a hemisphere of the buckyball structure. Their name is derived from their long, hollow structure with the walls formed by one-atom-thick sheets of carbon, called graphene. These sheets are rolled at specific and discrete ("chiral”) angles, and the combination of the rolling angle and radius decides the nanotube properties; for example, whether the individual nanotube shell is a metal or semiconductor. Nanotubes are categorized as single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs). Individual nanotubes naturally align themselves into "ropes" held together by van der Waals forces, more specifically, pi-stacking.
Applied quantum chemistry, specifically, orbital hybridization best describes chemical bonding in nanotubes. The chemical bonding of nanotubes is composed entirely of sp2 bonds, similar to those of graphite. These bonds, which are stronger than the sp3 bonds found in alkanes, provide nanotubules with their unique strength.
Recent Journal Articles
Development of novel synthetic method of carbon nanotubes from electrospun polystyrene fibers by using microwave heating
(2653–2658)Polymers for Advanced Technologies 22 #12 (2011)
Ohta et al ofShinshu University, China, synthesized metal-capsulated carbon nanotubes (CNTs) using a combined technology of electrospinning-metallization and microwave heating. These techniques greatly shorten the time for the synthesis of the CNTs in comparison with the conventional methods. The resulting CNTs were multi-walled and found to be about 25–100 nm in diameters. The products prepared by heating at 600 and 900°C exhibited less-developed and strongly curved CNTs, whereas the products prepared by heating at 700 and 800°C relatively well-developed long CNTs. (RDC 11/25/2011)
Review Articles
Polymer nanocomposites based on functionalized carbon nanotubes
(837-867) Progress in Polymer Science 35 #7 (2010)
”Since CNTs usually form stabilized bundles due to Van der Waals interactions, are extremely difficult to disperse and align in a polymer matrix.” “There are several methods for the dispersion of nanotubes in the polymer matrix such as solution mixing, melt mixing, electrospinning, in-situ polymerization and chemical functionalization of the carbon nanotubes” (RDC 11/12/2010)