Carbon nanotube wires with continuous current rating exceeding 20 Amperes

Abstract

A process to fabricate carbon nanotube (CNT) wires with diameters greater than 1 cm and continuous current carrying capability exceeding 20 A is demonstrated. Wires larger than 5 mm are formed using a multi-step radial densification process that begins with a densified CNT wire core followed by successive wrapping of additional CNT material to increase the wire size. This process allows for a wide range of wire diameters to be fabricated, with and without potassium tetrabromoaurate (KAuBr4) chemical doping, and the resulting electrical and thermal properties to be characterized. Electrical measurements are performed with on/off current steps to obtain the maximum current before reaching a peak CNT wire temperature of 100 °C and before failure, yielding values of instantaneous currents in excess of 45 A for KAuBr4 doped CNT wires with a diameter of 6 mm achieved prior to failure. The peak temperature of the wires at failure (∼530 °C) is correlated with the primary decomposition peak observed in thermal gravimetric analysis of a wire sample confirming that oxidation is the primary failure mode of CNT wires operated in air. The in operando stability of doped CNT wires is confirmed by monitoring the resistance and temperature, which remain largely unaltered over 40 days and 1 day for wires with 1.5 mm and 11.2 mm diameters, respectively. The 100 °C continuous current rating, or ampacity, is measured for a range of doped CNT wire diameters and corresponding linear mass densities ρL. To describe the results, a new form of the fuse-law, where the critical current is defined as I∝ρL3/4, is developed and shows good agreement with the experimental data. Ultimately, CNT wires are shown to be stable electrical conductors, with failure current densities in excess of 50 A in the case of a convectively cooled 11.2 mm doped CNT wire, and amenable for use in applications that have long-term, high-current demands.

A Meta‐Analysis of Conductive and Strong Carbon Nanotube Materials

“…MWCNT fibers with large fiber diameters (100 µm to 6 mm) or poorer alignment show even lower ampacities of 10 6 A m −2 . [ 259,260 ] All together, these results suggest that improvements in density and alignment are more critical to ampacity than other factors such as doping.…”

High Ampacity Carbon Nanotube Materials

“…However, and even with these problems, there are some authors who claim to have developed high-ampacity power cables, made of closely packed and aligned carbon nanotubes [62], with values of ampacity close to 1 × 10 5 A/cm 2 . Other recent results have shown that by using a radial densification process, it is possible to obtain cables with a diameter up to 1 cm in size [63]. A densified core of CNTs is first produced, and then successive layers of CNTs are wrapped and densified on top.…”

Effects of Solution Properties on Iodine Monobromide Doping for Enhanced Bulk Carbon Nanotube Electrical Conductivity

“…Mechanical testing took place by increasing the strain by 0.5%/min until yarn failure. The high-current characteristics of both the as-received yarn and yarns treated with IBr were measured using an Arbin BT-2000 power supply by applying a constant current through two source/measure probes (separated by 25 mm of yarn), which was increased every 30 s by 10 mA until wire failure, similar to procedures previously used to test high-current characteristics of CNT wires and yarns. , …”