Indian Journal of Engineering & Materials Sciences Vol. 27, December 2020, pp. 1112-1117 Synthesis of carbon nanotube fiber via direct spinning for conducting wires Pallvi Dariyal a,b , Abhishek Kumar Arya a,b , Bhanu Pratap Singh a,b *, Sanjay Ranganth Dhakate a,b * a CSIR-National Physical Laboratory, New Delhi 110 012, India b Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh 201002, India Received: 25 August 2020 The commercial conducting materials (Cu, Ag, Al etc.) have achieved their saturation due to their high density and Joule’s heating effect in terms of efficiency. In this outlook, carbon nanotubes (CNTs) are the most versatile, light weight and high electrically conducting material for advance generation. But it is difficult to weave them for commercialization. For the growth of 3-D CNT assemblies such as CNT fiber, CNT sheet, CNT rope and CNT ribbon, direct spinning is the most suitable technique because of its simplicity for continuous growth of CNT fiber. In the present work, different growth parameters were analysed for the growth of CNT fibers. The growth of CNT fibres has been carried out through direct spinning of as-synthesised CNT aerogel. CNT fibers were grown successfully via optimizing different processing parameters like temperature, pressure and argon to hydrogen ratio. The morphology of as-spun fibers was investigated via microscopic techniques such as optical microscopy, SEM and TEM. Moreover, the defects and metallicity of as-spun fibers have been analysed using Raman spectroscopy. The change in resistance with change in temperature was also measured for quality of as-made CNT fiber which shows metallic behavior as CNT fiber has positive temperature coefficient. Above 151K, conducting CNTs are dominating and below this temperature, semiconducting CNTs are showing their nature in R v/s T curve. Furthermore, the measured electrical conductivity of as-made fiber is 3.9×10³ S/m. These as-spun metallic fibers can outperform the currently used Cu wire. Hence, as-synthesized conductive CNT fibers have great potential as conducting wires. Keywords: Joule’s heating effect, CNT aerogel, 3D-CNT assemblies, Direct spinning, Temperature coefficient 1 Introduction Keeping an eye on the growing field of electrical engineering, light weight and highly electrically conducting materials are desirable for future electronics and nano-electronic devices for nano- sensors, different energy storage applications, automobile industries and aircraft manufacturers. The commercial conducting materials have achieved their saturation in terms of efficiency due to high density and efficacy. The carefully engineered conducting nano-structures may increase the device efficiency and reduce its size. Hence advanced lightweight and reliable alternatives to traditional conducting materials are being researched and implemented. The carbon nano-structures are suitable alternative of conventional conducting materials due to their high electrical conductivity (derived from graphite structure) and low density. Among them, carbon nanotubes (CNTs) are the most versatile material for advanced generation due to high electrical conductivity 1 , high flexibility and good environmental stability 2 . These nanotubes are long hollow conductors where delocalized electrons of sp 2 hybridized carbon are free to move along the axial direction 3 . Therefore, CNTs are also termed as ballistic conductors. Due to such fascinating electric properties such as high ampacity (>10 9 A cm -2 ), high conductivity (~10 5 S/m) and high EMI shielding effect, CNTs grab extensive attention among researchers since its discovery. Laser ablation, arc discharge and chemical vapor deposition (CVD) are well-established techniques to synthesize powdered CNTs 4, 5 , but CVD is the most common technique. But in powder form, it is difficult to take advantage of electrical properties of CNTs to make them usable in numerous applications such as transistors 6 , interconnectors, sensors 7 , flat panel displays. For having its advantage on industrial level, macrostructure of CNTs such as CNT fiber, CNT ribbon, CNT sheet form should be assembled 8, 9 . By aligning large number of CNTs, connected via weak van der Waals attraction, CNT fiber can be synthesized. These can be further used for power —————— *Corresponding authors (E-mail: bps@nplindia.org, dhakate@nplindia.org)