Advances in Precise Structure Control and Assembly toward the Carbon Nanotube Industry

Abstract

Carbon nanotubes (CNTs) possess a unique tubular structure composed of highly graphitized atoms. Since their sp2 hybridized skeleton is discovered under the microscope, extensive attention is paid to their peculiar physics and extraordinary performances in mechanics, optics, and electricity. However, due to the challenges in controlled synthesis and mass production, there is a long bottleneck period in both the science and engineering of CNTs. In the recent decade, significant advances have emerged in ton‐scale production, 3D microprocessors, ultrastrong fibers, etc., which have pushed the renaissance of CNTs toward a new peak. This important progress benefits from the critical but commonly ignored breakthroughs in the precise structure control and assembly of CNTs. Herein, the morphological manipulation and technical routes toward the CNT industry will be focused on. First, the growth mechanism of defect‐free aligned CNTs will be discussed. Subsequently, nondestructive flow‐guided fabrication methods and their application paradigms are summarized. Then, attention will be turned to assembly‐based industrial production and applications of CNTs. Some research prospects toward the precise synthesis and CNT industry are proposed at last, in the hope of building a comprehensive understanding on the catalytic assembly toward defect‐free nanostructures and their high‐end applications.

Possible interplay of tangential and perpendicular modes in the growth of Fe-filled carbon nanotubes

“…Carbon nanotubes are tubular molecular-like hollow 1-D structures with an exceptional chemical stability, resulting from sp 2 -hybridized carbon atoms. [1][2][3][4][5] These materials have been considered important candidates for a large number of applications, including nanoelectronics, 1 multifunctional scaffolds for magnetization of cancer cells, 2 dual magnetic resonance (MR) and single photon emission computed tomography (SPECT) agents, 3 molecular hydrogen sensors, 4 nanoreactors 5 and others. Owing to the chemical and physical properties which allow a complete protection from the external environment, CNTs have been also proposed as suitable nano-containers for encapsulation and stabilization of specific materials of interest.…”

“…21 Together with these observations, the presence of an open-growth mechanism has been proposed by Iijima et al 22 In the processes subsequent to those involving catalystparticle nucleation, the formation of CNT-caps has been indicated as a critical step for the growth and elongation of CNTs. 1,23 This process involves 1) carbon diffusion on/ through the surface of the chosen catalyst and 2) the inclusion of carbon atoms at the catalyst/CNT interface. 1,23 Interestingly, two categories of contact modes have been recently identified at the interface between the catalyst and as-formed CNTs, namely 1) a tangential mode, where the diameter of the CNT is similar to that of the catalyst and 2) a perpendicular mode where the width of the CNT (inner cavity) is smaller than the diameter of the catalyst-particle.…”

“…1,23 This process involves 1) carbon diffusion on/ through the surface of the chosen catalyst and 2) the inclusion of carbon atoms at the catalyst/CNT interface. 1,23 Interestingly, two categories of contact modes have been recently identified at the interface between the catalyst and as-formed CNTs, namely 1) a tangential mode, where the diameter of the CNT is similar to that of the catalyst and 2) a perpendicular mode where the width of the CNT (inner cavity) is smaller than the diameter of the catalyst-particle. 24 The possible presence of intermediate tangential growth modes has been also suggested by Bichara et al 25,26 Partial catalyst-filling rates of CNT-capillaries have been generally reported in experiments involving the pyrolysis of ferrocene.…”

Heterostructure Interface Construction of Cobalt/Nickel Diselenides Hybridized with sp2–sp3 Bonded Carbon to Boost Internal/External Sodium and Potassium Storage Dynamics

“…23 Graphitized carbon in sp 2 state possesses higher charge carrier mobility and better electrical conductivity than that of sp 3 carbon. 24 Therefore, suitable collocation of amorphous carbon and graphitized carbon to construct sp 2 −sp 3 bonded carbon hybrid could integrate the merits of the two components, which will be conducive to meliorating the electrochemical performance of metal selenide heterostructures. In view of this, from the perspective of enhancing the ion/electron transport and internal/external energy storage dynamics of metal selenides, the construction of bimetallic selenide heterostructure hybridized with sp 2 −sp 3 bonded carbon should be a feasible approach to achieve satisfactory electrochemical properties, but the related studies are still scarce.…”

“…However, the carbonaceous materials in situ derived from MOFs (amorphous carbon in sp 3 state in the majority) generally possess highly distorted and curved crystal lattices with effective mechanics buffer capability but weak electrical conductivity, which will restrain the rapid electron transport in the electrochemical energy storage reactions . Graphitized carbon in sp 2 state possesses higher charge carrier mobility and better electrical conductivity than that of sp 3 carbon . Therefore, suitable collocation of amorphous carbon and graphitized carbon to construct sp 2 –sp 3 bonded carbon hybrid could integrate the merits of the two components, which will be conducive to meliorating the electrochemical performance of metal selenide heterostructures.…”