Advanced Materials from Natural Materials: Synthesis of Aligned Carbon Nanotubes on Wollastonites

Abstract

The growth of carbon nanotubes (CNTs) on natural materials is a low-cost, environmentally benign, and materials-saving method for the large-scale production of CNTs. Directly building 3D CNT architectures on natural materials is a key issue for obtaining advanced materials with high added value. We report the fabrication of aligned CNT arrays on fibrous natural wollastonite. Strongly dispersed iron particles with small sizes were produced on a planar surface of soaked fibrous wollastonite by a reduction process. These particles then catalyzed the decomposition of ethylene, leading to the synchronous growth of CNTs to form leaf- and brush-like wollastonite/CNT hybrids. The as-obtained hybrids could be further transformed into porous SiO(2)/CNT hybrids by reaction with hydrochloric acid. Further treatment with hydrofluoric acid resulted in aligned CNT arrays, with purities as high as 98.7 %. The presented work is very promising for the fabrication of advanced materials with unique structures and properties that can be used as fillers, catalyst supports, or energy-absorbing materials.

Recent Progress on the Growth Mechanism of Carbon Nanotubes: A Review

“…High-quality aligned MWCNTs with a narrow diameter distribution were obtained on vermiculite and wollastonite. [158,243] Recently, the same group managed to grow SWCNTs with 90 % selectivity and a yield of 0.06 g SWCNT g catalyst À1 (similar to the yield obtained on Fe/MgO, see Section 3.4.5) using a 1 wt % Fe/sepiolite catalyst. [242] 6.…”

“…[251] An alternative approach, which still involves the use of natural minerals but which allows more control, consists in using a natural support and adding an active phase by, for example, ion exchange. [242][243] This route was especially explored by Wei's group. [158,[242][243] They used clays such as vermiculite, mica, and sepiolite, or silicates such as wollastonite as catalyst supports and added the Fe or FeMo active phase by ion exchange using iron nitrate and ammonium heptamolybdate as precursors.…”

“…[242][243] This route was especially explored by Wei's group. [158,[242][243] They used clays such as vermiculite, mica, and sepiolite, or silicates such as wollastonite as catalyst supports and added the Fe or FeMo active phase by ion exchange using iron nitrate and ammonium heptamolybdate as precursors. High-quality aligned MWCNTs with a narrow diameter distribution were obtained on vermiculite and wollastonite.…”

A review of the large-scale production of carbon nanotubes: The practice of nanoscale process engineering

“…These spheres also exhibit good flowability and can be transferred easily in the reactor. Radial growth on spheres is a good strategy for the mass production of aligned CNTs [35]. However, the spherical substrates used in our research had a size of about 0.6-1.2 mm, and are D particles, according to the Geldart particle classification.…”

“…One conventional method for patterning aligned CNTs is the pre-patterning of catalyst layers. Typical methods include lithography followed by e-beam evaporation of catalysts [44], selective wettability control followed by dip coating [45], and the soft contact [32]; (b) SEM image of a rough substrate with 10-m concave structures; and (c) CNT ropes synthesized on this substrate [33]; aligned CNTs grown on (d) ceramic spheres [34] and (e) fibers [35]; (f)-(g) CNT architectures grown using a pattern transfer method [36]. imprint method [46].…”