Enhanced thermal conductivity carbon nanotube (CNT) fibers

Thermal management is critical to improving the performance efficiency and operational lifetime of electronic devices. In their current form, motor systems consume approximately 68% of electricity in the U.S. manufacturing sector. In order to obtain lightweight motors and generators with improved efficiency and performance, a highly electrically and thermally conductive, yet lightweight winding material needs to be developed. This project seeks to develop enhanced thermal conductivity carbon nanotube fibers for use as lightweight motor windings and for thermal management in battery and electronics applications. Carbon nanotubes combine high strength, and electrical and thermal conductivity with low density, making them ideal for applications where durability and light weight are high priorities. To this end, this project proposes to use a conductor made from wet-spun carbon nanotube fibers as a replacement for the heavy and mechanically weak metallic motor winding materials. The technical approach combines theoretical modeling and experimental fabrication of enhanced thermal conductivity carbon nanotube fibers. Phase I aims to develop carbon nanotube fibers with thermal conductivity exceeding 720 W/m-K at room temperature, a 15% enhancement in thermal conductivity over current state-of-the-art doped carbon nanotube conductors. To achieve this, carbon nanotube fibers will be produced from carbon nanotubes with varying aspect ratio and graphitic character. The theoretical and experimental results will guide which carbon nanotube material is most suitable for production of enhanced thermal conductivity fibers. Several different carbon nanotube fiber processing conditions will be tested to ensure that fibers with optimal carbon nanotube alignment and packing are produced with the best available carbon nanotubes. These fibers will be fabricated, doped with iodine to further enhance thermal conductivity, and tested to provide a direct comparison to previously reported state-of-the-art doped carbon nanotube fibers. Commercial Applications and Other Benefits: The successful development of carbon nanotube conductors will be of high value to applications that require flexible and durable connectors between heat sources and heat sinks, and for use as electrically conductive wires for applications in which heat generated by electric currents needs to be quickly dispersed, including motor windings. Carbon nanotube windings could allow motors to operate at higher frequencies while minimizing potential issues related to winding material heating. This factor will greatly improve motor efficiency and reduce motor weight. Lightweight motors will be critical for the development of electrically powered aircraft and carbon nanotube winding materials will be immensely valuable for motors in all electric aviation. In addition, due to their superior corrosion resistance, carbon nanotube windings can enable the operation of electric motors and generators in harsher and more demanding environments, particularly subterranean and subsea applications. Carbon nanotube-based motors will last longer and operate more efficiently in these conditions, reducing climate impact through energy savings during operation and saving the material that would be needed for replacement parts.