10-08-2012, 11:26 AM
Applications of Carbon Nanotubes
[attachment=30894]
Abstract.
Carbon nanotubes have attracted the fancy of many scientists worldwide.
The small dimensions, strength and the remarkable physical properties of
these structures make them a very unique material with a whole range of promising
applications. In this review we describe some of the important materials science
applications of carbon nanotubes. Specifically we discuss the electronic and
electrochemical applications of nanotubes, nanotubes as mechanical reinforcements
in high performance composites, nanotube-based field emitters, and their use as
nanoprobes in metrology and biological and chemical investigations, and as templates
for the creation of other nanostructures. Electronic properties and device
applications of nanotubes are treated elsewhere in the book. The challenges that
ensue in realizing some of these applications are also discussed from the point of
view of manufacturing, processing, and cost considerations.
Potential Application of CNTs
Field emission is an attractive source for electrons compared to thermionic
emission. It is a quantum effect. When subject to a sufficiently high electric
field, electrons near the Fermi level can overcome the energy barrier to
escape to the vacuum level. The basic physics of electron emission is well
developed. The emission current from a metal surface is determined by the
Fowler–Nordheim equation: I = aV 2 exp(−bφ3/2/βV) where I, V , φ, β, are
Applications of Carbon Nanotubes 395
the current, applied voltage, work function, and field enhancement factor,
respectively [26,27].
Cathode-Ray Lighting Elements
Cathode ray lighting elements with carbon nanotube materials as the field
emitters have been fabricated by Ise Electronic Co. in Japan [45]. As illustrated
in Fig. 5, these nanotube-based lighting elements have a triode-type
design. In the early models, cylindrical rods containing MWNTs, formed as a
deposit by the arc-discharge method, were cut into thin disks and were glued
to stainless steel plates by silver paste. In later models, nanotubes are now
screen-printed onto the metal plates. A phosphor screen is printed on the
inner surfaces of a glass plate. Different colors are obtained by using different
fluorescent materials.
Flat Panel Display
Prototype matrix-addressable diode flat panel displays have been fabricated
using carbon nanotubes as the electron emission source [46]. One demonstration
(demo) structure constructed at Northwestern University consists
of nanotube-epoxy stripes on the cathode glass plate and phosphor-coated
Indium-Tin-Oxide (ITO) stripes on the anode plate [46]. Pixels are formed
at the intersection of cathode and anode stripes, as illustrated in Fig. 6. At a
cathode-anode gap distance of 30μm, 230V is required to obtain the emission
current density necessary to drive the diode display (∼ 76 μmA/mm2). The
device is operated using the half-voltage off-pixel scheme. Pulses of ±150V
are switched among anode and cathode stripes, respectively to produce an
image.
[attachment=30894]
Abstract.
Carbon nanotubes have attracted the fancy of many scientists worldwide.
The small dimensions, strength and the remarkable physical properties of
these structures make them a very unique material with a whole range of promising
applications. In this review we describe some of the important materials science
applications of carbon nanotubes. Specifically we discuss the electronic and
electrochemical applications of nanotubes, nanotubes as mechanical reinforcements
in high performance composites, nanotube-based field emitters, and their use as
nanoprobes in metrology and biological and chemical investigations, and as templates
for the creation of other nanostructures. Electronic properties and device
applications of nanotubes are treated elsewhere in the book. The challenges that
ensue in realizing some of these applications are also discussed from the point of
view of manufacturing, processing, and cost considerations.
Potential Application of CNTs
Field emission is an attractive source for electrons compared to thermionic
emission. It is a quantum effect. When subject to a sufficiently high electric
field, electrons near the Fermi level can overcome the energy barrier to
escape to the vacuum level. The basic physics of electron emission is well
developed. The emission current from a metal surface is determined by the
Fowler–Nordheim equation: I = aV 2 exp(−bφ3/2/βV) where I, V , φ, β, are
Applications of Carbon Nanotubes 395
the current, applied voltage, work function, and field enhancement factor,
respectively [26,27].
Cathode-Ray Lighting Elements
Cathode ray lighting elements with carbon nanotube materials as the field
emitters have been fabricated by Ise Electronic Co. in Japan [45]. As illustrated
in Fig. 5, these nanotube-based lighting elements have a triode-type
design. In the early models, cylindrical rods containing MWNTs, formed as a
deposit by the arc-discharge method, were cut into thin disks and were glued
to stainless steel plates by silver paste. In later models, nanotubes are now
screen-printed onto the metal plates. A phosphor screen is printed on the
inner surfaces of a glass plate. Different colors are obtained by using different
fluorescent materials.
Flat Panel Display
Prototype matrix-addressable diode flat panel displays have been fabricated
using carbon nanotubes as the electron emission source [46]. One demonstration
(demo) structure constructed at Northwestern University consists
of nanotube-epoxy stripes on the cathode glass plate and phosphor-coated
Indium-Tin-Oxide (ITO) stripes on the anode plate [46]. Pixels are formed
at the intersection of cathode and anode stripes, as illustrated in Fig. 6. At a
cathode-anode gap distance of 30μm, 230V is required to obtain the emission
current density necessary to drive the diode display (∼ 76 μmA/mm2). The
device is operated using the half-voltage off-pixel scheme. Pulses of ±150V
are switched among anode and cathode stripes, respectively to produce an
image.