Page 44 - Carbon Nanotube Fibres and Yarns
P. 44
CHAPTER 3
Carbon nanotube fibers spun
directly from furnace
Guangfeng Hou, Mark J. Schulz
Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, OH,
United States
3.1 Introduction
There has been substantial progress in carbon nanotube (CNT) synthesis
and understanding of their fundamental structure and properties since the
explicit revelation of the seamless tubular structure of multi-walled carbon
nanotube (MWNT) synthesized using the arc discharge method by Iijima in
1991 [1]. However, CNTs have been synthesized in the 1970s and treated as
small carbon filaments [2, 3], and some early works even trace back to 1952
[4]. Nowadays, the advanced understanding of structure-property relation-
ships and successful large-scale production of CNTs have enabled numer-
ous engineering applications, primarily based on their application-oriented
characteristics such as high surface area, various capabilities of chemical
modification, and functional integration with other materials [5].
The CNTs can be synthesized using various methods, including arc
discharge, laser ablation, substrate chemical vapor deposition (CVD), and
floating catalyst synthesis. These methods all require a catalyst (usually a tran-
sition metal) and external energy input to catalytically decompose the car-
bon source and efficiently grow CNTs. The type of catalyst, carbon source,
and experimental conditions determine the CNT type, length, purity, and
yield. In the floating catalyst synthesis method, a feedstock is introduced
into a furnace reactor, which pyrolyzes at high temperature to continuously
synthesize carbon nanomaterials in the gas phase with the help of a catalyst.
Studies of the catalyst dynamics and CNT growth have shown that it is vital
to regulate the sulfur concentration [6–10], feedstock injection temperature
[6, 11], carrier gas flow rate [12, 13], and type of hydrocarbon [14, 15] in
order to control the CNT diameter, quality, and impurity. There are also in-
tensive studies on improving CNT fiber properties in recent years [16–20].
Carbon Nanotube Fibers and Yarns Copyright © 2020 Elsevier Ltd.
https://doi.org/10.1016/B978-0-08-102722-6.00003-1 All rights reserved. 37
