Advances in the science and technology of carbon nanotubes and their composites: a review Erik T. Thostensona, Zhifeng Renb, Tsu-Wei Choua,*
Department of Mechanical Engineering and Center for Composite Materials, University of Delaware, Newark, DE 19716, USA b Department of Physics, Boston College, Chestnut Hill, MA 02167, USA Received 1 May 2001; received in revised form 19 June 2001; accepted 21 June 2001
Abstract Since their ﬁrst observation nearly a decade ago by Iijima (Iijima S. Helical microtubules of graphitic carbon Nature. 1991; 354:56–8), carbon nanotubes have been the focus of considerable research. Numerous investigators have since reported remarkable physical and mechanical properties for this new form of carbon. From unique electronic properties and a thermal conductivity higher than diamond to mechanical properties where the stiﬀness, strength and resilience exceeds any current material, carbon nanotubes oﬀer tremendous opportunities for the development of fundamentally new material systems. In particular, the exceptional mechanical properties of carbon nanotubes, combined with their low density, oﬀer scope for the development of nanotubereinforced composite materials. The potential for nanocomposites reinforced with carbon tubes having extraordinary speciﬁc stiﬀness and strength represent tremendous opportunity for application in the 21st century. This paper provides a concise review of recent advances in carbon nanotubes and their composites. We examine the research work reported in the literature on the structure and processing of carbon nanotubes, as well as characterization and property modeling of carbon nanotubes and their composites. # 2001 Elsevier Science Ltd. All rights reserved.
1. Introduction In the mid 1980s, Smalley and co-workers at Rice University developed the chemistry of fullerenes . Fullerenes are geometric cage-like structures of carbon atoms that are composed of hexagonal and pentagonal faces. The ﬁrst closed, convex structure formed was the C60 molecule. Named after the architect known for designing geodesic domes, R. Buckminster Fuller, buckminsterfullerene is a closed cage of 60 carbon atoms where each side of a pentagon is the adjacent side of a hexagon similar to a soccer ball (the C60 molecule is often referred to as a bucky ball) . A few years later, their discovery led to the synthesis of carbon nanotubes. Nanotubes are long, slender fullerenes where the walls of the tubes are hexagonal carbon (graphite structure) and often capped at each end. These cage-like forms of carbon have been shown to exhibit exceptional material properties that are a * Corresponding author. Tel.: +1-302-831-2421; fax: +1-302-8313619. E-mail address: firstname.lastname@example.org (T.-W. Chou).
consequence of their symmetric structure. Many researchers have reported mechanical properties of carbon nanotubes that exceed those of any previously existing materials. Although there are varying reports in the literature on the exact properties of carbon nanotubes, theoretical and experimental results have shown extremely high elastic modulus, greater than 1 TPa (the elastic modulus of diamond is 1.2 TPa) and reported strengths 10–100 times higher than the strongest steel at a fraction of the weight. Indeed, if the reported mechanical properties are accurate, carbon nanotubes may result in an entire new class of advanced materials. To unlock the potential of carbon nanotubes for application in polymer nanocomposites, one must fully understand the elastic and fracture properties of carbon nanotubes as well as the interactions at the nanotube/ matrix interface. Although this requirement is no different from that for conventional ﬁber-reinforced composites , the scale of the reinforcement phase diameter has changed from micrometers (e.g. glass and carbon ﬁbers) to nanometers. In addition to the exceptional...