08-01-2013, 02:35 PM
Carbon Nanotube
[attachment=46695]
What is a Carbon Nanotube?
A Carbon Nanotube is a tube-shaped material, made of carbon, having a diameter measuring on the nanometer scale. A nanometer is one-billionth of a meter, or about one ten-thousandth of the thickness of a human hair. The graphite layer appears somewhat like a rolled-up chicken wire with a continuous unbroken hexagonal mesh and carbon molecules at the apexes of the hexagons.
Carbon Nanotubes have many structures, differing in length, thickness, and in the type of helicity and number of layers. Although they are formed from essentially the same graphite sheet, their electrical characteristics differ depending on these variations, acting either as metals or as semiconductors.
As a group, Carbon Nanotubes typically have diameters ranging from <1 nm up to 50 nm. Their lengths are typically several microns, but recent advancements have made the nanotubes much longer, and measured in centimeters.
Carbon Nanotubes can be categorized by their structures:
• Single-wall Nanotubes (SWNT)
Single-wall nanotubes (SWNT) are tubes of graphite that are normally capped at the ends. They have a single cylindrical wall. The structure of a SWNT can be visualized as a layer of graphite, a single atom thick, called graphene, which is rolled into a seamless cylinder.
Most SWNT typically have a diameter of close to 1 nm. The tube length, however, can be many thousands of times longer.
SWNT are more pliable yet harder to make than MWNT. They can be twisted, flattened, and bent into small circles or around sharp bends without breaking.
SWNT have unique electronic and mechanical properties which can be used in numerous applications, such as field-emission displays, nanocomposite materials, nanosensors, and logic elements. These materials are on the leading-edge of electronic fabrication, and are expected to play a major role in the next generation of miniaturized electronics.
• Multi-wall Nanotubes (MWNT)
Multi-wall nanotubes can appear either in the form of a coaxial assembly of SWNT similar to a coaxial cable, or as a single sheet of graphite rolled into the shape of a scroll.
The diameters of MWNT are typically in the range of 5 nm to 50 nm. The interlayer distance in MWNT is close to the distance between graphene layers in graphite.
MWNT are easier to produce in high volume quantities than SWNT. However, the structure of MWNT is less well understood because of its greater complexity and variety. Regions of structural imperfection may diminish its desirable material properties.
The challenge in producing SWNT on a large scale as compared to MWNT is reflected in the prices of SWNT, which currently remain higher than MWNT.
What are the Properties of a Carbon Nanotube?
The intrinsic mechanical and transport properties of Carbon Nanotubes make them the ultimate carbon fibers. The following tables (Table 1 and Table 2) compare these properties to other engineering materials.
Overall, Carbon Nanotubes show a unique combination of stiffness, strength, and tenacity compared to other fiber materials which usually lack one or more of these properties. Thermal and electrical conductivity are also very high, and comparable to other conductive materials.
10 Uses for Carbon Nanotubes
Tubular is back. This time it's about the carbon (not the wave). Stronger than steel and lighter than a feather, carbon nanotubes have the potential to revolutionize just about everything.
The world's strongest known substance is graphene, a one-atom-thick sheet of carbon atoms arranged hexagonally. When layers of it are piled one on top of another, the result is ordinary pencil graphite that shears apart like a tiny stack of paper. But take a graphene layer and roll it into a tube and it forms a fiber theoretically 100 times stronger than steel and six times lighter: a carbon nanotube.
Not surprisingly, carbon nanotubes (CNTs) have garnered much attention for their strength, which comes from the double bonds that hold their carbon atoms together. Each tube has the potential to be over one million times longer than its diameter (50 thousand times slimmer than a human hair), and inspire visions of a super-strong, super-light-weight material that could enable researchers to engineer the structures and fabrics of the future.
Yet strength is only part of their appeal.
"Most of the interest has been in applications to electronic materials," said Michael Arnold, assistant professor in the Materials Science and Engineering department at the University of Wisconsin-Madison. Arnold's research focuses largely on the production and sorting of CNTs. According to him, CNTs have many appealing electric properties. Depending on their atomic arrangement, they can be either semiconductors or conductors of electricity. Semiconductors are crucial in electronics for making transistors, tiny switches of electric current that convert electric signals to digital data.
[attachment=46695]
What is a Carbon Nanotube?
A Carbon Nanotube is a tube-shaped material, made of carbon, having a diameter measuring on the nanometer scale. A nanometer is one-billionth of a meter, or about one ten-thousandth of the thickness of a human hair. The graphite layer appears somewhat like a rolled-up chicken wire with a continuous unbroken hexagonal mesh and carbon molecules at the apexes of the hexagons.
Carbon Nanotubes have many structures, differing in length, thickness, and in the type of helicity and number of layers. Although they are formed from essentially the same graphite sheet, their electrical characteristics differ depending on these variations, acting either as metals or as semiconductors.
As a group, Carbon Nanotubes typically have diameters ranging from <1 nm up to 50 nm. Their lengths are typically several microns, but recent advancements have made the nanotubes much longer, and measured in centimeters.
Carbon Nanotubes can be categorized by their structures:
• Single-wall Nanotubes (SWNT)
Single-wall nanotubes (SWNT) are tubes of graphite that are normally capped at the ends. They have a single cylindrical wall. The structure of a SWNT can be visualized as a layer of graphite, a single atom thick, called graphene, which is rolled into a seamless cylinder.
Most SWNT typically have a diameter of close to 1 nm. The tube length, however, can be many thousands of times longer.
SWNT are more pliable yet harder to make than MWNT. They can be twisted, flattened, and bent into small circles or around sharp bends without breaking.
SWNT have unique electronic and mechanical properties which can be used in numerous applications, such as field-emission displays, nanocomposite materials, nanosensors, and logic elements. These materials are on the leading-edge of electronic fabrication, and are expected to play a major role in the next generation of miniaturized electronics.
• Multi-wall Nanotubes (MWNT)
Multi-wall nanotubes can appear either in the form of a coaxial assembly of SWNT similar to a coaxial cable, or as a single sheet of graphite rolled into the shape of a scroll.
The diameters of MWNT are typically in the range of 5 nm to 50 nm. The interlayer distance in MWNT is close to the distance between graphene layers in graphite.
MWNT are easier to produce in high volume quantities than SWNT. However, the structure of MWNT is less well understood because of its greater complexity and variety. Regions of structural imperfection may diminish its desirable material properties.
The challenge in producing SWNT on a large scale as compared to MWNT is reflected in the prices of SWNT, which currently remain higher than MWNT.
What are the Properties of a Carbon Nanotube?
The intrinsic mechanical and transport properties of Carbon Nanotubes make them the ultimate carbon fibers. The following tables (Table 1 and Table 2) compare these properties to other engineering materials.
Overall, Carbon Nanotubes show a unique combination of stiffness, strength, and tenacity compared to other fiber materials which usually lack one or more of these properties. Thermal and electrical conductivity are also very high, and comparable to other conductive materials.
10 Uses for Carbon Nanotubes
Tubular is back. This time it's about the carbon (not the wave). Stronger than steel and lighter than a feather, carbon nanotubes have the potential to revolutionize just about everything.
The world's strongest known substance is graphene, a one-atom-thick sheet of carbon atoms arranged hexagonally. When layers of it are piled one on top of another, the result is ordinary pencil graphite that shears apart like a tiny stack of paper. But take a graphene layer and roll it into a tube and it forms a fiber theoretically 100 times stronger than steel and six times lighter: a carbon nanotube.
Not surprisingly, carbon nanotubes (CNTs) have garnered much attention for their strength, which comes from the double bonds that hold their carbon atoms together. Each tube has the potential to be over one million times longer than its diameter (50 thousand times slimmer than a human hair), and inspire visions of a super-strong, super-light-weight material that could enable researchers to engineer the structures and fabrics of the future.
Yet strength is only part of their appeal.
"Most of the interest has been in applications to electronic materials," said Michael Arnold, assistant professor in the Materials Science and Engineering department at the University of Wisconsin-Madison. Arnold's research focuses largely on the production and sorting of CNTs. According to him, CNTs have many appealing electric properties. Depending on their atomic arrangement, they can be either semiconductors or conductors of electricity. Semiconductors are crucial in electronics for making transistors, tiny switches of electric current that convert electric signals to digital data.