Likewise, joining CNTs together may form transistor-like devices. Fortuitously, these defects allow the SWNTs to act as transistors. It has been reported that individual SWNTs contain defects. The current density that was possible to achieve was 10 7 A/cm 2, however in theory the SWNT ropes should be able to sustain much higher stable current densities, as high as 10 13 A/cm 2. This means that SWNT ropes are the most conductive carbon fibers known. The resistivity of the SWNT ropes was in the order of 10 –4 ohm-cm at 27☌. The conductivity and resistivity of ropes of SWNTs has been measured by placing electrodes at different parts of the 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. However, there is no change in current across different parts of metallic single-walled CNTs. Furthermore, interwall reactions within MWNTs have been found to redistribute the current over individual tubes non-uniformly. Some types of “armchair”-structured CNTs appear to conduct better than other metallic CNTs. Carbon Nanotube ElectronicsĬonductivity in MWNTs is quite complex. CNTs can be either metallic or semi-conducting in their electrical behavior. Their conductivity has been shown to be a function of their chirality (degree of twist), as well as their diameter.
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. There has been considerable practical interest in the conductivity of CNTs. Single Walled Double Walled Carbon Nanotubes Molecular Structure Carbon Nanotubes PropertiesĪspect Ratio An Interior Representation Of A Carbon Nanotube Electrical Conductivity They vary by purity, length, and functionality. If you wish to buy carbon nanotubes, please use the drop down products menu or click the links above. The types of carbon nanotubes are typically referred to as Single Walled Carbon Nanotubes and Multi Walled Carbon Nanotubes.
#Applications of carbon nanotubes full#
Using the L and d values for this material (aspect ratio 1000 and diameter of 0.7 to 0.9 nm (6) ), the calculated hydrodynamic diameter is found to be between 97 and 125 nm depending on the chosen value for tube diameter. This range includes the DLS data obtained here. Thus, the measurement results are consistent with expectations.There are numerous carbon nanotubes properties and applications which take full advantage of CNTs aspect ratio, mechanical strength, electrical and thermal conductivity. Where D h is hydrodynamic diameter. The result is that the value of D h found by DLS in terms of tube length (L) and tube diameter (d) is given by the following equation. We can compare this to the Stokes-Einstein relationship used to determine particle size from the translational diffusion coefficient determined by DLS. It is possible to estimate the diffusion coefficient of a carbon nanotube. Nevertheless, due to its speed DLS is a good technique for characterizing the size of these nanotubes. For example, the nanotube under study has an aspect ratio close to 1000. Thus, the results from DLS do not clearly correspond to a single dimension (length or diameter) of the tube, but rather to a combined value. A number of techniques are necessary to obtain a complete picture of these complex materials.įigure 1: Illustration of a single wall carbon nanotube from a rolled up sheet of carbonĭynamic light scattering (DLS) has become the technique of choice for characterizing nanomaterials in suspension due to its speed and ability to readily characterize a statistically significant number of particles. The technique measures the fluctuations in the intensity of scattered light that arise due to particle motion. This is then converted to particle diffusion coeffient and finally to particle size.ĭynamic light scattering data is typically interpreted in terms of a sphere. That is, the results correspond to the diameter of a sphere that moves in the same way as the analyte particle. However, as the name suggests, nanotubes are long cylinders. SWCNT’s have been characterized by a number of techniques including fluorescence spectroscopy (1-3) and Raman scattering (4). These nanotubes consist of rolled up single sheets of carbon atoms and due to the high aspect ratio and nature of the C-C bonds have unique properties.
Single wall carbon nanotubes (SWCNT’s) have unique mechanical and electronic properties and therefore have attracted much interest.
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