ABSTRACT
On the nano-to microscale, theoretical calculations and experimental measurements indicate that single-walled carbon nanotubes (SWNTs) have electrical conductivity and current-carrying capacity similar to copper,1,2 thermal conductivity higher than diamond,3,4 and mechanical strength higher than any naturally occurring or manmade material.5,6 Although precise numbers are hard to pinpoint because of the limited accuracy of theoretical calculations and experiments on small bundles of nanotubes (NTs), Baughman et al. cite ballistic conductance in metallic SWNTs, a theoretical thermal conductivity of 2000 W/m K, an elastic modulus of 640 GPa, and a tensile strength of 37 GPa.7 Some microelectronic and materials characterization applications (e.g., an atomic force microscopy tip) may be able to utilize the properties of individual and small groups of SWNTs. However, many important applications require low-cost synthesis of SWNTs and manufacturing methods that preserve some or all of the nanoscale properties in a macroscopic object.8,9 Whereas at least one solution to the economic mass production of SWNTs is now available through the HiPco process10 and potentially by other scalable routes,11,12 technologies for processing SWNTs into macroscopic materials are at a much earlier stage. Some of the most promising ones for manufacturing SWNT fibers are reviewed here.
