Composite Yarns of Multi-walled Carbon Nanotubes with Metallic Electrical Conductivity

Unique macrostructures known as spun carbon-nanotube fibers (CNT yarns) can be manufactured from vertically aligned forests of multi-walled carbon nanotubes (MWCNTs). These yarns behave as semiconductors with room-temperature conductivities of about 5x102 S cm-1. Their potential use as, for example, microelectrodes in medical implants, wires in microelectronics, or lightweight conductors in the aviation industry has hitherto been hampered by their insufficient electrical conductivity. In this Full Paper, the synthesis of metal–CNT composite yarns, which combine the unique properties of CNT yarns and nano-crystalline metals to obtain a new class of materials with enhanced electrical conductivity, is presented. The synthesis is achieved using a new technique, self-fuelled electro deposition (SFED), which combines a metal reducing agent and an external circuit for transfer of electrons to the CNT surface, where the deposition of metal nano-particles takes place. In particular, the Cu–CNT and Au–CNT composite yarns prepared by this method have metal-like electrical conductivities (2–3 x 105 S cm-1) and are mechanically robust against stringent tape tests. However, the tensile strengths of the composite yarns are 30–50 % smaller than that of the unmodified CNT yarn. The SFED technique described here can also be used as a convenient means for the deposition of metal nano-particles on solid electrode supports, such as conducting glass or carbon black, for catalytic applications. Keywords: Carbon nanotubes, electrical conductivity, nano-composites, nano-crystalline materials, self-fuelled electro deposition. 1