"Conceptually, single-wall carbon nanotubes (SWCNTs) can be considered
to be formed by the rolling of a single layer of graphite (called a
graphene layer) into a seamless cylinder. A multiwall carbon nanotube
(MWCNT) can similarly be considered to be a coaxial assembly of
cylinders of SWCNTs, like a Russian doll, one within another; the
separation between tubes is about equal to that between the layers in
natural graphite. Hence, nanotubes are one-dimensional objects with a
well-defined direction along the nanotube axis that is analogous to the
in-plane directions of graphite."
—M. S. Dresselhaus, Department of Physics and the Department of
Electrical Engineering and Computer Science, Massachusetts Institute of
A one dimensional fullerene (a convex
cage of atoms with only hexagonal and/or pentagonal faces) with a
cylindrical shape. Carbon nanotubes discovered in 1991 by Sumio Iijima
resemble rolled up graphite, although they can not really be made that
way. Depending on the direction that the tubes appear to have been
rolled (quantified by the 'chiral vector'), they are known to act as
conductors or semiconductors. Nanotubes are a proving to be useful as
molecular components for nanotechnology. [Encyclopedia Nanotech]
Strictly speaking, any tube with nanoscale dimensions, but generally
used to refer to carbon nanotubes, which are sheets of graphite rolled
up to make a tube. A commonly mentioned non-carbon variety is made of
boron nitride, another is silicon. These noncarbon nanotubes are most
often referred to as nanowires.
The dimensions are variable (down to 0.4 nm in diameter) and you can
also get nanotubes within nanotubes, leading to a distinction between
multi-walled and single-walled nanotubes. Apart from remarkable tensile
strength, nanotubes exhibit varying electrical properties (depending on
the way the graphite structure spirals around the tube, and other
factors, such as doping), and can be superconducting, insulating,
semiconducting or conducting (metallic). [CMP]
Nanotubes can be either electrically conductive or semiconductive,
depending on their helicity, leading to nanoscale wires and electrical
components. These one-dimensional fibers exhibit electrical
conductivity as high as copper, thermal conductivity as high as
diamond, strength 100 times greater than steel at one sixth the weight,
and high strain to failure. NASA JSC - Carbon Nanotubes
A nanotube's chiral angle--the angle between the axis of its hexagonal
pattern and the axis of the tube--determines whether the tube is
metallic or semiconducting. Nanotubes Under Stress
A graphene sheet can be rolled more than one way, producing different
types of carbon nanotubes. The three main types are armchair, zig-zag,
and chiral. Examples
Carbon nanotubes possess many unique properties which make them ideal
AFM probes. Their high aspect ratio provides faithful imaging of deep
trenches, while good resolution is retained due to their
nanometer-scale diameter. These geometrical factors also lead to
reduced tip-sample adhesion, which allows gentler imaging. Nanotubes
elastically buckle rather than break when deformed, which results in
highly robust probes. They are electrically conductive, which allows
their use in STM and EFM (electric force microscopy), and they can be
modified at their ends with specific chemical or biological groups for
high resolution functional imaging. Professor Charles M. Lieber Group
CNT exhibits extraordinary mechanical properties: the Young's modulus
is over 1 Tera Pascal. It is stiff as diamond. The estimated tensile
strength is 200 Giga Pascal. These properties are ideal for reinforced
composites, nanoelectromechanical systems (NEMS).
Center for Nanotechnology |
Carbon Nanotube Transistors exploit the fact that nm- scale
nanotubes (NT) are ready-made molecular wires and can be rendered into
a conducting, semiconducting, or insulating state, which make them
valuable for future nanocomputer design. ... Carbon nanotubes are quite
popular now for their prospective electrical, thermal, and even
Physics News 590, May 21, 2002
Many potential applications have been proposed for carbon nanotubes,
including conductive and high-strength composites; energy storage and
energy conversion devices; sensors; field emission displays and
radiation sources; hydrogen storage media; and nanometer-sized
semiconductor devices, probes, and interconnects. Some of these
applications are now realized in products. Others are demonstrated in
early to advanced devices, and one, hydrogen storage, is clouded by
controversy. Nanotube cost, polydispersity in nanotube type, and
limitations in processing and assembly methods are important barriers
for some applications of single-walled nanotubes.
Carbon Nanotubes—the Route Toward Applications Ray H. Baughman, Anvar A. Zakhidov, Walt A. de Heer
AKA: Multi-wall Carbon Nanotubes (MWNTs), Single-wall Carbon Nanotubes (SWCNs),
(5, 5) armchair nanotube, (9, 0) zigzag nanotube, and (10, 5) chiral nanotube. Also, single-wall carbon nanotube field-effect transistors (CNFETs). See Nanotubes, Nanocones, and Nanosheets: an applet that lets you control in 3D the components and form elements.
[Steffen Weber, PhD.
See his VRML gallery of Fullerenes]. Also carbon nanowalls.
carbon nanotube with metal-semiconductor junction
structure of a multi-walled nanotube
Click image to enlarge
Copyright Alain Rochefort
Engineering Physics Department,
Nanostructure Group, Center for Research on Computation and its Applications (CERCA).
"It is the roundest and most symmetrical large molecule known
to man. Buckministerfullerine continues to astonish with one amazing
property after another. Named after American architect R. Buckminister
Fuller who designed a geodesic dome with the same fundamental symmetry,
C60 is the third major form of pure carbon; graphite and diamond are
the other two." Bucky Balls - Andy Gion.
AKA: C60 molecules & buckminsterfullerene. Molecules made up of 60
carbon atoms arranged in a series of interlocking hexagons and
pentagons, forming a structure that looks similar to a soccer ball
[Steffen Weber, PhD.].
C60 is actually a "truncated icosahedron", consisting of 12 pentagons
and 20 hexagons. It was discovered in 1985 by Professor Sir Harry
Kroto, and two Rice University professors, chemists Dr. Richard E.
Smalley and Dr. Robert F. Curl Jr., [for which they were jointly
awarded the 1996 Nobel Lauriate for chemistry] and is the only molecule
composed of a single element to form a hollow spheroid [which gives the
potential for filling it, and using it for novel drug-delivery systems.
See Structure of a New Family of Buckyballs Created].
"The buckyball, being the roundest of round molecules, is also quite
resistant to high speed collisions. In fact, the buckyball can
withstand slamming into a stainless steel plate at 15,000 mph, merely
bouncing back, unharmed. When compressed to 70 percent of its original
size, the buckyball
becomes more than twice as hard as its cousin, diamond." The Buckyball
- Rodrigo de Almeida Siqueira.
AKA: Endohedral fullerenes, carbon cages.
Click to enlarge
Kreylos, Center for Image Processing and Integrated Computing (CIPIC), University of California, Davis.
Click to enlarge
C. Wagner, Dept. of Biological Sciences, University of Delaware.
Click to enlarge
. See Materials by Computational Design and Atomistic Simulations
This figure presents a visualization of a nanohydraulic piston. The
model consists of a Carbon nanotube (blue), Helium atoms (green), and a
"Buckyball" molecule. It is used to explore the stability of the