Page 474 - Carrahers_Polymer_Chemistry,_Eighth_Edition

Inorganic Polymers 437

Filters—CNTs have been used to filter carbon dioxide from power plant emissions and so may be a

future air pollution filter material. They have also been used to filter water removing the salt content

by allowing water to pass through but capturing the chloride ions.
Catalyst Supports—CNTs have a very high surface area. Each carbon atom is exposed to the inte-
rior and exterior surface. Because of the chemist’s ability to connect almost any moiety to their
surface, a number of CNTs have been shown to act as outstanding catalyst supports when catalysts
have been attached to them. Because of their high strength, they perform well to the rigors of being
a catalysts support. Their ability to conduct electricity and heat suggests additional ways CNTs can
be used to assist catalytic behavior.
Superconductors—CNTs offer unique electronic properties due to quantum confi nement.

According to quantum confinement, electrons can only move along the nanotube axis. Metallic
CNTs are found to be high-temperature superconductors.
Fibers and Fabrics—Textiles spun from CNTs have been made into clothing such as slacks. Along
with offering outstanding liquid shedding clothing made from them, the clothing possess outstanding
wear resistance. Penetration-resistant body and vehicle armor can be made from composites contain-

ing CNTs fibers. They are also being studied for use in transmission line cables. Addition of nano-
tubes to concrete increases its tensile strength and stops crack propagation. Addition to polyethylene

increases its elastic modulus. (For more fiber applications please see “Composites” below.)
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Energy Storage—CNTs have a very high surface area (about 10 m /g), good electrical conductiv-
ity and can be made very linear (straight). They have been used to make lithium batteries with the
highest reversible capacity of any carbon material and employed to make supercapacitor electrodes.
CNTs are used in a variety of fuel cell applications where durability is important.
Biomedical Applications—CNTs allow cells to grown on and over them without adherence to the
nanotubes and without toxic reaction. Potential applications range from their use within coatings
and composites to be used within the body, for prosthetics, and in the construction of vascular stents
and neuron growth and regulation.
Heat Conductivity—Their outstanding anisotropic thermal conductivity allows them to be used
when heat must be moved from one location to another.

Composites—CNTs, because of their fiber nature on a molecular level makes them outstanding

fibers for composites where strength, electrical and thermal conductivity, stiffness, and toughness
are needed. Because CNTs contribute to high values of all of these properties, composites can be
constructed where outstanding behavior in any one of these areas is needed. Sports wear such as
lighter and stronger golf club shafts, bike parts, baseball bats, and tennis rackets have been produced
from nanotubes-containing composites. Electronic motor brushes have been made from nanotubes
composites that are better lubricated, cooler running, stronger, less brittle, and more accurately
moldable in comparison to the traditional carbon black brushes.

Coatings—Because of their good strength, thermal and electrical conductivity, and slipperiness,
CNTs offers potential interesting coatings applications. Thus, a building coated with a CNT-
containing material that has great durability will remain free from dust, dirt, and organic growth,
and can be used to capture energy via heat and electrical conductivity.
Films—Films have been formed from CNTs that are high strength, conductive, and transparent.
They are being investigated for use in liquid crystal diodes (LCDs), photovoltaic devices, fl exible
displays (foldable TV screens), and touch screens and are intended to replace indium tin oxide (ITO)
in many applications.
Nanomotors—Multiwalled nanotubes exhibit an interesting telescoping behavior where they can
slide within the outer tube with essentially no friction allowing the creation of almost frictionless

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