Horizontally aligned carbon nanotube arrays: growth mechanism, controlled synthesis, characterization, properties and applications

Abstract

Carbon nanotubes (CNTs) have attracted worldwide research interest in the past two decades owing to their extraordinary properties and wide applications in numerous fields. Among various types of CNTs, the horizontally aligned CNT (HACNT) arrays, which consist of CNTs grown on flat substrates and parallel with each other with large intertube distances and lengths up to centimeters, show many advantages due to their perfect structures and extraordinary mechanical, thermal and electrical properties. HACNTs show great potential as building blocks for transparent displays, nano electronics, quantum lines, field emission transistors, superstrong tethers, aeronautics and astronics materials, and even space elevators. During the past years, great progress has been achieved in HACNT research. In this review, we systematically review the growth mechanism, structure control, morphology control, characterization, manipulation, properties, and applications of HACNTs. Finally, we present a summary and outlook for the future development of HACNTs. We hope these advances will shed light on the future study of HACNTs.

Single-step growth of graphene and graphene-based nanostructures by plasma-enhanced chemical vapor deposition

“…HACNTs usually follow the freegrowth model and so exhibit weak inter-tube interactions, 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 The synthesis environment of HACNTs is similar to that for VACNTs except the gas flow inside the growing chamber is strong enough to guide the CNT growth direction parallel to the substrate. In addition, a temperature difference between the gas flow and the substrate must be created to produce a thermal buoyancy vertical to the sample [221]. The buoyancy in the laminar gas flow will lift the CNTs from the substrate and the catalyst nanoparticles at the tip ends of the floating CNTs can continue to catalyse the CNT growth.…”

Carbon nanotube array as a van der Waals two-dimensional hyperbolic material

“…In fact, this effect is equivalent to piercing an armchair nanotube by a strong magnetic field along the CNT axis [32]. Our calculations show that the band gap in an optimally-spaced (9,9) tube is E g = 40 meV which corresponds to an effective magnetic field of 65 T. This gap opening should be accompanied by strong interband dipole transitions in the narrow range of photon energies near the band gap [17,32,33]. The dispersion remains strongly anisotropic with a very heavy effective mass in the X-direction near the conduction band minimum, and displays hyperbolic behavior near k y = 2π/3 and either k x = 0 or k x = π/b.…”

“…The main band structure parameters of the (15, 0) CNT array are summarized in Table IV. For comparison, we present in Fig. 6 the results of the ab-initio energy spectrum calculations for an optimallyspaced array of armchair (9,9) nanotubes, which have a diameter, D ≈ 23.07 a.u., very close to that of the (15, 0) CNTs considered above. Notably, the optimal separation between the (9, 9) armchair CNTs, d = 6 a.u., is the same as between (15, 0) nanotubes in their optimally-spaced array.…”

“…The electronic band structure of an array of(9,9) carbon nanotubes separated by d = 6 a.u. : (a) along the tube axis for kx = 0.2; (b) in the direction normal to the tube axis for ky = 0.33.…”

Aligned High Density Semi‐Conductive Ultra‐Small Single‐Walled Carbon Nanotubes

“…using the Langmuir‐Blodgett method. 63 However, the vertically aligned arrays show higher thermal conductivity and offer advantages for practical applications . Thus the present study represents a big step ahead not only the preparation of aligned densely packed SWCNTs, but also in their production in a form appropriate for practically uses.…”