Millimeter-Thick Single-Walled Carbon Nanotube Forests: Hidden Role of Catalyst Support

Abstract

A parametric study of so-called "super growth" of single-walled carbon nanotubes (SWNTs) was done by using combinatorial libraries of iron/aluminum oxide catalysts.Millimeter-thick forests of nanotubes grew within 10 min, and those grown by using catalysts with a thin Fe layer (about 0.5 nm) were SWNTs. Although nanotube forests grew under a wide range of reaction conditions such as gas composition and temperature, the window for SWNT was narrow. Fe catalysts rapidly grew nanotubes only when supported on aluminum oxide. Aluminum oxide, which is a well-known catalyst in hydrocarbon reforming, plays an essential role in enhancing the nanotube growth rates.

Distinct termination morphologies for vertically aligned carbon nanotube forests

“…Millimeter tall forests of SWNTs and/or MWNTs (multi-walled carbon nanotubes) are now regularly synthesized [1,3,[5][6][7][8][9][10][11][12][13][14][15][16][17] and research has shifted focus from how nanotube growth is initiated to the increasingly important question of how nanotube growth terminates [15,18,19]. Several reports demonstrate that nanotube forests grow at an initially rapid rate which drops off either gradually [7,20,21] or suddenly [15,22,23].…”

Resonance R aman Spectroscopy

“…After the first success of VA-SWNT synthesis, different methods have been also reported by other groups in producing this kind of forest-like structures or thick VA-SWNT, like microwave plasma CVD [35], O 2 -assisted CVD [36], and etc [37,38,39,40], including water-assisted super-growth [41]. In the case of vertical growth of SWNTs, the alcohol pressures inside the growth chamber during SWNT synthesis were kept to be approximately 10 Torr (1.3 kPa) for our system, which yield an average diameter of as-grown SWNTs around 1.9-2.0 nm with several micrometers in length [42].…”

X-ray photoelectron spectroscopy study on Fe and Co catalysts during the first stages of ethanol chemical vapor deposition for single-walled carbon nanotube growth

“…[5][6][7][8][9][10] It has been claimed that Fe/Al 2 O 3 interfacial bonding restricts Fe surface mobility and hence allows for high density SWCNT forest growth. 5,6 In addition, it has been suggested 7,8 that Al 2 O 3 , which is a well known catalyst for hydrocarbon formation, 11 aids in decomposing the carbon precursor and therefore enhances SWCNT forest growth from the catalyst. This suggestion, however, has been rejected by Mattevi et al 6 In addition, the morphology of the substrate has been proven to play an important role in the behavior of the catalyst, 9,10 and therefore determines whether or not a SWCNT forest is grown.…”