A simultaneous increase in the thermal and electrical transport in carbon nanotube yarns induced by inter-tube metallic welding

Vertically aligned arrays of multiwall carbon nanotubes (MWCNT) were decorated with gold (Au) nanoparticles of different diameter and areal densities and spun into yarns. The melting point of Au nanoparticles determined by differential scanning calorimetry was approximately 260 °C, well below the oxidation temperature of carbon. A continuous yarn was formed while pulling out a bundle of CNTs from the metalized CNT array. Relatively low temperature (300 °C) thermal processing of the metalized yarn resulted in a 30% improvement in thermal conductivity, 40% increase in electrical conductivity and a 4× increase in elastic modulus. Cross-sections of the yarn were examined with transmission electron microscopy to characterize the physical nature of the metal–nanotube interface. The deposition procedure described to decorate the nanotube yarns is easily scalable to larger CNT arrays or other configurations for commercial applications, such as medical implants, lightweight conductors, smart uniforms for the soldiers, and conformal electronics in aerospace industry.