Highly Oriented Direct-Spun Carbon Nanotube Textiles Aligned by In Situ Radio-Frequency Fields

Abstract

Carbon nanotubes (CNTs) individually exhibit exceptional physical properties, surpassing state-of-the-art bulk materials, but are used commercially primarily as additives rather than as a standalone macroscopic product. This limited use of bulk CNT materials results from the inability to harness the superb nanoscale properties of individual CNTs into macroscopic materials. CNT alignment within a textile has been proven as a critical contributor to narrow this gap. Here, we report the development of an altered direct CNT spinning method based on the floating catalyst chemical vapor deposition process, which directly interacts with the self-assembly of the CNT bundles in the gas phase. The setup is designed to apply an AC electric field to continuously align the CNTs in situ during the formation of CNT bundles and subsequent aerogel. A mesoscale CNT model developed to simulate the alignment process has shed light on the need to employ AC rather than DC fields based on a CNT stiffening effect (z-pinch) induced by a Lorentz force. The AC-aligned synthesis enables a means to control CNT bundle diameters, which broadened from 16 to 25 nm. The resulting bulk CNT textiles demonstrated an increase in the specific electrical and tensile properties (up to 90 and 460%, respectively) without modifying the quantity or quality of the CNTs, as verified by thermogravimetric analysis and Raman spectroscopy, respectively. The enhanced properties were correlated to the degree of CNT alignment within the textile as quantified by small-angle X-ray scattering and scanning electron microscopy image analysis. Clear alignment (orientational order parameter = 0.5) was achieved relative to the pristine material (orientational order parameter = 0.19) at applied field intensities in the range of 0.5–1 kV cm –1 at a frequency of 13.56 MHz.

Micro- and Macrostructures of Aligned Boron Nitride Nanotube Arrays

“…In addition to the use of VA-CNTs as BNNT scaffolds, we also demonstrate the synthesis of BN macrostructures using other carbon macrostructures as the scaffold. BN is deposited on randomly oriented CNT film (“buckypaper”, from Tortech, , Figure a), bare commercial microscale diameter carbon fibers (CF , Figure b) and “fuzzy” CF (Figure c) were all uniformly coated by BN. “Fuzzy” CF are CF grafted with carbon nanofibers with a diameter of ∼10 nm and a surface area 35 times higher than the bare CF (their synthesis is described in a prior work).…”

Inverse projection of axisymmetric orientation distributions

“…For instance, aligning cellulose fibres can substantially improve their stiffness, tensile strength and thermal stability [1,2]. Likewise, aligning carbon nanotube (CNT) fibres has been shown to greatly improve their mechanical properties as well as their electrical and thermal conductivity [3][4][5][6][7], which was recently confirmed by a large meta-analysis [8]. In biological systems, aligning collagen fibres also increases their stiffness [9,10] and is directly related to the mechanical strength of tendons [11,12] and bones [13].…”

Graphene Interlocking Carbon Nanotubes for High-Strength and High-Conductivity Fibers

“…Carbon nanotubes (CNTs), featuring an excellent combination of low density, superior flexibility, ultrahigh strength and modulus, and good thermal and electrical conductivities, have been well known as the ideal building block for the next-generation high-performance fibers. − Owing to these outstanding features, carbon nanotube fibers (CNTFs) could achieve plenty of engineering applications in bulletproof vests, lightweight wires, artificial muscles, energy systems, flexible electronics, etc. − Various techniques have been developed to produce CNTFs, such as spinning from the CNT liquid crystal dope, , spinning from the vertically aligned CNT arrays, and direct spinning from the CNT aerogels. − Generally, the direct spinning process offers a feasible way to realize the continuous and scalable production of CNTFs. However, so far, the properties of CNTFs, particularly their strength and electrical conductivity, are still not a circumstance to individual CNTs, ,, strongly hindering their niche applications.…”