Study in the Dispersion of Carbon Nanotubes
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Study in the Dispersion of Carbon Nanotubes Matthew Bratcher1, Bonnie Gersten1, Helen Ji2, Jimmy Mays2 1 U. S. Army Research Laboratory, AMSRL-WM-M, Rodman Materials Research Building, Aberdeen Proving Ground, MD 21001 2 Department of Chemistry, 901 South 14th Street, University of Alabama, Birmingham, AL 35294
ABSTRACT In the past, the dispersion of carbon nanotubes (CNTs) in both liquids and solids has been difficult due to the high surface interactions between the tubes. Dispersion of polymer CNT composites is important for such benefits as structural reinforcement of composites, the percolation threshold of CNT based conducting materials, and the thermal properties with the exploitation of the high surface area of CNTs. Here we discuss two approaches towards addressing dispersion of multiwalled nanotubes (MWNTs). One approach is the use of surfactant chemicals selected on the basis that they interact with CNT chemical groups. The second approach is the functionalization through covalent bonding of the CNTs with various polymers including polyethylenimine (PEI), and poly(methyl methacrylate) (PMMA). The two approaches were evaluated to determine whether covalent functionalization was more beneficial than the use of surfactants. Characterization of the dispersion was performed using various microscopy techniques.
BACKGROUND The discovery of carbon nanotubes (CNTs) in 1991 by Ijima1 has spurred a tremendous amount of carbon-based nanotechnology research throughout the world. CNTs were synthesized under similar conditions to fullerenes such as arc discharge of graphite and chemical vapor deposition methods, however it was soon found that in addition to a carbon-based fuel, a metallic catalyst was required for an effective synthesis. The search for an ideal synthetic approach is still underway, but many advances have been made since the initial discovery. The desire to synthesize CNTs was undoubtedly motivated by their unique properties. The pairing of a high Young’s modulus with high electrical conductivity certainly attracted much attention as well as chemical resilience of CNTs and the thermal conductivity, which rivals that of diamond. The structure and properties of CNTs make them ideal candidates for many applications in both the military and commercial sectors. Here are some of the applications that address some key issues for the soldier of the future. 1) Power sources. The soldier of the future is envisioned to have a power system that is lightweight and very efficient. CNTs can be utilized in this system as a component of a battery. The low density of the CNTs (1.3 g/cc) makes the CNTs ideal candidates for lightweight battery materials. 2) Electromagnetic (EM) shielding. Not only do electronics require shielding, but the soldiers themselves will also need to be shielded from their “on-board” systems. The Z9.29.1
conductive properties of CNTs make them a new alternative for EM shielding. 3) Ballistic protection. CNTs are expected to have an impact in the area of textile fibers used for ballistic protecti
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