Dispersions and Aggregation of Carbon Nanotubes

Authored by: Jeffery R. Alston , Harsh Chaturvedi , Michael W. Forney , Natalie Herring , Jordan C. Poler

Handbook of Nanophysics

Print publication date:  September  2010
Online publication date:  September  2010

Print ISBN: 9781420075427
eBook ISBN: 9781420075434
Adobe ISBN:

10.1201/9781420075434-10

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Abstract

Nanostructured carbon has shown great utility in modifying and enhancing the physiochemical properties of composite materials (Lau et al., 2006). Specifically, single-walled carbon nanotubes (SWNTs) are unique in their ability to enhance the electrical and mechanical properties of materials. The science and technology of formulating stable dispersions of SWNTs in various media has been well reviewed in the literature. This chapter is intended to be an encapsulated tutorial on the formation, stability, and properties of carbon nanotube (CNT) dispersions. That said, the reader is advised to also access several well-cited reviews in this important area. Bundles of tubes aligned parallel with each other and interacting through extensive van der Waals (vdW) forces is the thermodynamically stable state of SWNTs. If we can provide enough energy to overcome this binding energy, it is possible to disperse the SWNTs as individual tubes into various solvents and polymeric matrices. Fu and Sun (2003) review some of the earlier work on forming SWNT dispersions in various solvents and for various surface modifications of the tubes. This is a good place to get started for those unfamiliar with this field. Regardless of the solvent one wants to disperse nanotubes into, one must use some form of mechanical mixing to separate the individual tubes from the stable bundle. Mechanically grinding nanotube solids into a dispersant is effective, but often damages the tubes too much (Chen et al., 2001a). In order to intentionally shorten and damage SWNTs, high-impact mixing techniques such as Ball–Milling are used (Pierard et al., 2004). When one’s intentions are to put as much nanostructured carbon into the matrix regardless of its final properties, these first two mechanical methods are straightforward to apply. Another mechanical method that has shown good utility in dispersing and separating SWNTs is high shear mixing. This technique forces the nanotube bundles through small pores or plates that pull individual tubes from the bundles through extrusion. The article by Hilding provides an excellent review of the mechanical mixing methods and also includes an introduction to the structure and properties of CNTs (Hilding et al., 2003).

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