Page 15 - Carbon Nanotube Fibres and Yarns

Introduction 7

the theoretical strength, as achieved by high-performance synthetic fibers
(Dyneema, Spectra, and Kevlar), the CNT fiber would achieve a specific
3
strength as high as 5.7 N/tex or 10.3 GPa for a fiber density of 1.8 g/cm .

1.4 Potential applications

Although CNT fibers and yarns produced in laboratories are still not as
strong as ultra-strong textile fibers, their multifunctional properties inspired
a generation of researchers devoted to the development of a wide range of
applications based on CNT fibers and yarns. The combination of strength,
flexibility, electrical conductivity, electrochemical reactivity, and porosity
makes CNT yarns excellent candidates for miniature sensors, actuators, and
energy storage devices required in smart textiles for health care, sports, mil-
itary, entertainment, and other aspects of modern digital life.

1.5 Organization of the book

The science and manufacturing technology around CNT fibers and yarns
are still evolving. This book is aimed at providing a snapshot of these de-
velopments to people in academia and research of CNT materials, as well
as product designers and processing engineers interested in the science
and technology for the production, further processing, and applications of
emerging high-performance textile materials.
Part 1 of the book deals with the production of CNT yarns and fibers,
including “pure” CNT fibers and CNT-reinforced nanocomposite fibers.
Chapter 2 discusses the probably most widely known two-step manufac-
turing method of CNT yarn. The first step is growing nanotubes, typically
multi-walled carbon nanotubes (MWNTs) on a substrate, known variously
as vertically aligned CNT arrays or CNT forests. In the second step, the
CNTs in the forest are drawn out in the form of a continuous web, which is
simultaneously densified into a yarn by twist insertion, liquid densification,
mechanical rubbing, or other methods.
CNT fibers can also be manufactured from gaseous feedstock directly
in one step, a process bearing similarities to the production of silk fibers
by spiders and silkworms, and to the reaction spinning of synthetic fibers.
This process is often referred to as the “direct spinning” method because
a fiber is pulled out from the high-temperature furnace directly, or re-
ferred to as the floating catalyst method in contrast with the deposition
of catalyst on a substrate in the two-step method discussed in Chapter 2.