Development and Commercialization of Vapor Grown Carbon Nanofibers: A Review
The lack of a low cost, high volume method to produce carbon nanotubes has greatly limited their commercialization. Carbon nanofibers have a similar structure and properties as nanotubes and are a commercially viable alternative to them. In recent years many of the difficulties of commercial nanofiber production have been overcome through innovations in their manufacturing process. It is now possible to produce carbon nanofibers of different grades, such as thinner and thicker walled ones, and low heat treated and high heat treated ones. Most significantly, commercial quantities can now be produced of carbon nanofibers that have been surface functionalized with carboxylic acid groups, making them suitable for further functionalization and new classes of applications, such as biomedical sensors and drug delivery. Despite their cost advantages and availability more widespread use of carbon nanofibers has been hampered by uncertainties in their molecular structure and a lack of physical property measurements. However, recent theoretical and experimental studies have addressed these deficiencies showing that these fibers have a cone-helix structure under the usual manufacturing conditions. Additionally, small amounts of a segmented carbon nanotube structure, commonly called a bamboo structure, are also present. When the conical nanofibers were heat treated they were found to transform to a stacked cone structure. Advances in surface functionalization have allowed a variety of groups to be incorporated on them, significantly enhancing their properties and potential applications. Finally, the recent development of a new method to measure the elastic properties and morphology of single nanofibers has clearly demonstrated the high strength of these fibers. These nanofibers now represent a well understood and well characterized graphitic carbon nanomaterial that can be manufactured at low cost in large quantities, and have the potential to bring widespread use of nanotechnology to a variety of fields.
J. A. Sekhar and J. P. Dismukes
A. Nadarajah et al., "Development and Commercialization of Vapor Grown Carbon Nanofibers: A Review", Key Engineering Materials, Vol. 380, pp. 193-206, 2008