Role of Water in Super Growth of Single-Walled Carbon Nanotube Carpets

Abstract

The Ostwald ripening behavior of Fe catalyst films deposited on thin alumina supporting layers is demonstrated as a function of thermal annealing in H2 and H2/H2O. The addition of H2O in super growth of single-walled carbon nanotube carpets is observed to inhibit Ostwald ripening due to the ability of oxygen and hydroxyl species to reduce diffusion rates of catalyst atoms. This work shows the impact of typical carpet growth environments on catalyst film evolution and the role Ostwald ripening may play in the termination of carpet growth.

A comprehensive study of the influence of the stoichiometry on the physical properties of TiOx films prepared by ion beam deposition

“…8, samples d, e, f͒. 52,53 Indeed, the presence of large amounts of oxygen surrounding Ti atoms prevent particles interaction and thus coalescence of larger cluster.…”

Odako growth of dense arrays of single-walled carbon nanotubes attached to carbon surfaces

“…Directly following the deposition of the catalyst layer, an overlayer of alumina (Al 2 O 3 ) 5 nm thick was deposited onto the catalyst. Our recent studies focusing on imaging the morphology of thin catalyst Nano Res (2009) 2: 526 534 films emphasize that catalyst deposition results in the formation of Fe islands due to the balance of the catalyst-surface interfacial interaction relative to the intra-particle atomic interactions [19]. This means that the deposition of the alumina overlayer results in the formation of a continuous film of alumina that not only interacts with the deposited catalyst islands, but also with the carbon surface.…”

Data-driven understanding of collective carbon nanotube growth by in situ characterization and nanoscale metrology

“…42,44 Experimental studies have also shown that heating using a hot tungsten filament up to 2000°C produces atomic hydrogen that rapidly reduces the catalyst. 16,45 Other strong reducing agents such as ammonia (NH 3 ) 42 and hydrazine (N 2 H 4 ) 46 were also shown to cause the complete reduction of iron oxide. The reduction and phase change of Fe catalyst are therefore dependent on the annealing conditions, such as temperature, pressure, dwell time, and the gas environment.…”

“…9,16,18,36,[98][99][100] Studying the mechanochemical aspects of CNT growth, wherein the effects of mechanical forces on the catalytic process are analyzed both experimentally and numerically, is an area of current research and will enable better understating and control on the CNT growth process. A deeper understanding of all the competing deactivation mechanisms and identifying the dominant ones will open the door for approaches to overcome them.…”

“…[5][6][7][8] These variations arise from the dynamics of growth, which are dominated by time-varying kinetics of chemical decomposition, catalytic activation, catalyst poisoning/deactivation, and atomic diffusion. [9][10][11][12][13][14][15][16] Importantly, the non-uniform morphology of CNT forests influences their properties, such as in mechanical compression for example, which was shown to be affected by density gradients. 17 Hence, revealing the process-structure and structure-property relationships requires a comprehensive understanding of the atomic scale physicochemical processes underlying the bottom-up synthesis and selforganization of aligned CNTs.…”