Carbon Nanotube Films – in situ CNT growth kinetics: maximizing yield of growth-active precursor within a CVD reactor

Vertically aligned carbon nanotube (VACNT) films with a high degree of structural purity, uniformity and alignment exhibit great potential as functional nanomaterials, with applications ranging from sensors, energy storage, and desalination. However, to take full advantage of such functional materials, it is paramount to improve aspects of synthesis, such as growth dynamics, structural uniformity, and chirality. This requires the development of insight and experience in what determines nanotube growth dynamics in order to improve and control VACNT film manufacture. The aim of this project is to maximize the growth rate of these films, within a wider research program envisioned by the PI to bring down the associated production costs. | The intention of this initial startup project is to fully characterize a standard thermal CVD methodology with emphasis on the effects of gas-phase chemistry upstream of the substrate from which such nanotubes grow. We will explore various factors that will influence growth rate such as gas-flow turbulence, residence time, precursor/hydrogen loadings to the reactor, and furnace temperature. A standard horizontal tube furnace will be used to investigate growth of VACNTs, which results from passing ethylene/hydrogen/argon gas mixture through a heated quartz tube at ca. 800 C. The gases then catalytically decompose at the nano-sized iron particles which sit on top of a flat substrate surface inside the reactor to form the CNTs. | From this work, we aim to exploit the insight developed from characterizing such a thermal CVD system using standard ethylene precursor, in a way that serves as a best in-house reference for all of our successive experiments. The goal is to maximize the growth rates of VACNT films, in which a novel precursor butane has shown great promise to yield faster rates of growth. The limit, for VACNTs, is currently 1110 um/min using standard ethylene. Through potential doubling of the growth rate using butane, this work forms the seed of much interesting and useful graduate-based research embodied in a wider program envisioned by the PI at KFUPM.