Highly Conductive Wire: Cu Carbon Nanotube Composite Ampacity and Metallic CNT Buckypaper Conductivity
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Highly Conductive Wire: Cu Carbon Nanotube Composite Ampacity and Metallic CNT Buckypaper Conductivity
Henry C. de Groh III NASA Glenn Research Center, Cleveland, OH 44135, U.S.A. ABSTRACT Carbon nanotube (CNT) composites are being explored to improve the conductivity and density of electrical wire used in aviation. Presented are the current carrying capacity of a CNTCu composite and Roman spectroscopy and electrical conductivity of Buckypaper (BP) made of normal and sorted 95% metallic CNT (m-CNT). The ampacity of the Cu-CNT composite was 3.8% lower than pure Cu. This is significant because it is not in agreement with high CNT ampacity claims. The average conductivity of the CNT in the sorted, 95% metallic BP was 2.5 times higher than the CNT in the un-sorted BP. This shows the importance of the intrinsic CNT conductivity as opposed to interfacial resistances and that the conductivity of the semiconductor CNT present in the un-sorted BP must be much lower than the conductivity of m-CNT. The high conductivity of the sorted BP provides proof that conductivity improvements in CNT composites can be made by the use of sorted, highly conductive m-CNT. INTRODUCTION NASA is currently developing hybrid electric power systems for aircraft such as those presented by Rolt and Whurr [1] and Welstead and Felder [2] to improve aviation efficiency and lower environmental impacts [3]. Improvements in wire electrical conductivity and density are believed required for advancement of hybrid electric power in aircraft. The goals of this work are to improve the conductivity and density of magnet and transmission wire. To make these improvements additions of CNT to matrix materials Cu or Al are being explored. The properties of CNT depend greatly on the CNT’s chirality [4]. It has been found that typical CNT supplies consist of 34% “metallic” (m-CNT) and 66% “semiconductor” (s-CNT). Processes are being developed to either sort or preferentially grow s-CNT or m-CNT, but at this time, unless proven otherwise, CNT supplies consist of a mix of s-CNT and m-CNT [4,5]. Presented is work on Roman spectroscopy and Buckypaper (BP) conductivity measurement techniques designed to characterize the electronic nature of CNT supplies (metallic or semiconductor) and ampacity measurements made on a CNT-Cu composite. EXPERIMENTAL PROCEDURES Current carrying capacity (ampacity) Two samples of 20 AWG Cu wire were compared to three of similar gauge TerraCopper Cu-1wt%CNT [6] composite wire (NanoRidge Materials Inc.) and two of 28 AWG CNT yarn (Nanocomp Technologies Inc.). The CNT yarn is expected to contain multi-wall carbon nanotubes (MWNT). Each specimen was 2.2 in. (5.59 cm) long. Average diameter was determined from 8 measurements with each taken at a different longitudinal, and azimuthal
Downloaded from https:/www.cambridge.org/core. Monash University, on 08 Jan 2017 at 20:59:06, subject to the Cambridge Core terms of use, available at https:/www.cambridge.org/core/terms. http://dx.doi.org/10.1557/adv.2016.653
location. Wire specimens were clamped to
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