Issue 4, Previous Article Next Article. From the journal: Nanoscale. Function-driven engineering of 1D carbon nanotubes and 0D carbon dots: mechanism, properties and applications. You have access to this article. Please wait while we load your content Something went wrong. Try again? Cited by. Back to tab navigation Download options Please wait Article type: Review Article.
DOI: Function-driven engineering of 1D carbon nanotubes and 0D carbon dots: mechanism, properties and applications Q. Xu, W. Li, L. Ding, W. Yang, H. Xiao and W.
Search articles by author Quan Xu. Weijun Li. Lan Ding. Wenjing Yang.
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Carbon Nanotubes: Properties and Applications
Share Give access Share full text access. Share full text access. Please review our Terms and Conditions of Use and check box below to share full-text version of article. Volume 46 , Issue 19 May 4, Pages They vary by purity, length, and functionality. There has been considerable practical interest in the conductivity of CNTs.
Carbon nanotubes: properties, synthesis, purification, and medical applications
CNTs with particular combinations of N and M structural parameters indicating how much the nanotube is twisted can be highly conducting, and hence can be said to be metallic. Their conductivity has been shown to be a function of their chirality degree of twist , as well as their diameter. CNTs can be either metallic or semi-conducting in their electrical behavior. Conductivity in MWNTs is quite complex.
Furthermore, interwall reactions within MWNTs have been found to redistribute the current over individual tubes non-uniformly. However, there is no change in current across different parts of metallic single-walled CNTs. However, the behavior of ropes of semi-conducting SWNTs is different, in that the transport current changes abruptly at various positions on the CNTs. This means that SWNT ropes are the most conductive carbon fibers known. It has been reported that individual SWNTs contain defects.
Fortuitously, these defects allow the SWNTs to act as transistors. Likewise, joining CNTs together may form transistor-like devices. A nanotube with a natural junction where a straight metallic section is joined to a chiral semiconducting section behaves as a rectifying diode — that is, a half-transistor in a single molecule. It has also recently been reported that SWNTs can route electrical signals at high speeds up to 10 GHz when used as interconnects on semi-conducting devices.
The carbon atoms of a single graphene sheet of graphite form a planar honeycomb lattice, in which each atom is connected via a strong chemical bond to three neighboring atoms. Because of these strong bonds, the basal-plane elastic modulus of graphite is one of the largest of any known material. For this reason, CNTs are expected to be the ultimate high-strength fibers.
SWNTs are stiffer than steel, and are very resistant to damage from physical forces. Pressing on the tip of a nanotube will cause it to bend, but without damage to the tip.
When the force is removed, the tip returns to its original state. This property makes CNTs very useful as probe tips for very high-resolution scanning probe microscopy. Quantifying these effects has been rather difficult, and an exact numerical value has not been agreed upon. Using an atomic force microscope AFM , the unanchored ends of a freestanding nanotube can be pushed out of their equilibrium position and the force required to push the nanotube can be measured.
Other values significantly higher than that have also been reported.
The differences probably arise through different experimental measurement techniques. They have calculated a value of 1. Instead, they argue that the modulus of the MWNTs correlates to the amount of disorder in the nanotube walls. Not surprisingly, when MWNTs break, the outermost layers break first. New research from the University of Pennsylvania indicates that CNTs may be the best heat-conducting material man has ever known.
Research suggests that these exotic strands, already heralded for their unparalleled strength and unique ability to adopt the electrical properties of either semiconductors or perfect metals, may someday also find applications as miniature heat conduits in a host of devices and materials.
The strong in-plane graphitic C-C bonds make them exceptionally strong and stiff against axial strains. The almost zero in-plane thermal expansion but large inter-plane expansion of SWNTs implies strong in-plane coupling and high flexibility against nonaxial strains.
Many applications of CNTs, such as in nanoscale molecular electronics, sensing and actuating devices, or as reinforcing additive fibers in functional composite materials, have been proposed. Reports of several recent experiments on the preparation and mechanical characterization of CNT-polymer composites have also appeared. These measurements suggest modest enhancements in strength characteristics of CNT-embedded matrixes as compared to bare polymer matrixes. Preliminary experiments and simulation studies on the thermal properties of CNTs show very high thermal conductivity. It is expected, therefore, that nanotube reinforcements in polymeric materials may also significantly improve the thermal and thermo-mechanical properties of the composites.
Field emission results from the tunneling of electrons from a metal tip into vacuum, under application of a strong electric field. The small diameter and high aspect ratio of CNTs is very favorable for field emission. Even for moderate voltages, a strong electric field develops at the free end of supported CNTs because of their sharpness. He also immediately realized that these field emitters must be superior to conventional electron sources and might find their way into all kind of applications, most importantly flat-panel displays.
It is remarkable that after only five years Samsung actually realized a very bright color display, which will be shortly commercialized using this technology. This luminescence is induced by the electron field emission, since it is not detected without applied potential. This light emission occurs in the visible part of the spectrum, and can sometimes be seen with the naked eye. CNTs represent a very small, high aspect ratio conductive additive for plastics of all types. Their high aspect ratio means that a lower loading concentration of CNTs is needed compared to other conductive additives to achieve the same electrical conductivity.
CNTs have proven to be an excellent additive to impart electrical conductivity in plastics. Their high aspect ratio about imparts electrical conductivity at lower loadings, compared to conventional additive materials such as carbon black, chopped carbon fiber, or stainless steel fiber. Their unique composition, geometry, and properties enable numerous potential carbon nanotubes applications.
CARBON NANOTUBES: PROPERTIES AND APPLICATIONS (Technical Report) | ehomyqev.gq
Getting costs down to commercially viable levels has proven challenging but increasing scale is happening. The special nature of carbon combines with the molecular perfection of single-wall CNTs to endow them with exceptional material properties, such as very high electrical and thermal conductivity, strength, stiffness, and toughness. No other element in the periodic table bonds to itself in an extended network with the strength of the carbon-carbon bond.
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