Carbon nanotubes and its application

Abstract: The discovery of carbon nanotubes is another major area of ​​Research clusters, the paper discusses the structure of carbon nanotubes, properties, activation methods, review of this new type of nanometer-sized carbon materials in electrochemical devices, hydrogen storage , field emission devices, carbon nanotube field-effect transistor, catalyst support, the field of carbon nanotube modified electrode Application and look forward to the involvement of carbon nanotubes on the global physical, chemical and materials industry and other disciplines brought prospects.

Keywords:: Application of structural properties of carbon nanotubes
1, the discovery of carbon nanotubes
In 1991, scientists Iijima at NEC of Japan Preparation of C60, the first time by high resolution cathode scarring tunneling electron microscope (HRTEM) found a diameter 515nm, diameter of 213nm, only by two coaxial cylindrical graphite composite from the carbon structure. Further analysis shows that the tube entirely from carbon atoms, and as a hexagonal surface by a single layer of graphite on its axis in one direction, curl 360 ° seamless hollow tubes formed . the distance between adjacent tubes is about 0.34nm, and the graphite layers of carbon atoms in the distance between 0.335nm similar, so this structure are generally known as carbon nanotubes, which follows after the discovery of carbon C60 Also with allotrope, is another major area of ​​the carbon cluster Research [1].

2, the structure of carbon nanotubes
Carbon nanotubes (CNT and Ming Baji tube, is a special structure (the radial size of nanometer, micrometer axial size of the tubes are sealed at both ends essentially one-dimensional quantum materials. It is single or multi-layer graphite sheet around the central axis at a certain angle of winding spiral made of seamless, hollow "microtubules", each by a sp2 hybridized carbon atom through three carbon atoms with the surrounding bond after the complete posed by the cylindrical surface of hexagonal form. According to the different formation conditions, existence of multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) in two forms. MWNTs generally to the dozens of layers of Coaxial winding graphite layer composition, layer spacing of about 0.34nm, the typical diameter and length were 2-30nm0.1-50μm.SWNTs by a single coaxial winding graphite structure, the side from the carbon atoms hexagonal array composed of pentagons of carbon atoms at both ends capped. diameter generally from 10-20nm, lengths up to tens of microns general, and even up to 20cm [2].

3, the activation of carbon nanotubes
Generally believed that the introduction of some of the carbon nanotube surface active groups in power, after activation in order to have good electrochemical response. Activation methods are generally divided into two categories: ① in the electrodes made of activated carbon nanotubes before, including plasma oxidation using air or gas or acid (mainly concentrated HNO3) oxidation. to deal with concentrated HNO3 method of carbon nanotubes: the carbon nanotube immersed in concentrated nitric acid after 10 hours, 100 ℃ concentrated nitric acid reflux 5 - 6 hours. and then the suspension by centrifugal separation, drying, open tube of powder of carbon nanotubes nitration. take 1mg spread to 3ml of NN-dimethylformamide (DMF, the ultrasonic dispersion for 15 minutes aside. ② made electrode, electrochemical methods activated carbon electrode is about a certain solution (eg phosphate buffer) in a certain range of potential scan cycles. After activation since, according to the different media used, the surface of carbon nanotubes can be introduced in the oxygen, sulfur or groups, generally include hydroxyl, carbonyl, carboxyl, phenolic and quinone compounds, the electrical activity of groups can be catalytic or other material to promote the electron transfer reactions.

4 Properties of Carbon Nanotubes
4.1 The singular nature of the conductivity of carbon nanotubes is closely related to its structure. As the structure of carbon nanotubes with the same structure as graphite layers, and therefore have a very good electrical properties. Theory to predict the electrical conductivity depends on its diameter and the tube The spiral angle of the wall. When the diameter of CNTs is larger than 6mm, the conductivity decreased, when the diameter is less than 6mm time, CNTs can be seen as a good electrical conductivity properties of one-dimensional quantum wires.

4.2 In addition to excellent mechanical properties of the conductive properties of exotic addition to the extraordinary mechanical properties of carbon nanotubes as well. Theoretical calculations show that carbon nanotubes should have high strength and great tenacity. As the distance between atoms of carbon nanotubes short, small diameter of single carbon nanotubes, making the structure of the defect is not easy there, the Young's modulus of single carbon nanotubes is estimated up to 5 too Pa, the strength of steel is about 100 times the density steel but only 1 / 6. Therefore, the carbon nanotubes are considered the ultimate form of strengthening phase, it is estimated that carbon nanotubes in the composite will be very broad Application prospects. reposted elsewhere in the Research Papers Download http://www . hi138.com
4.3 good thermal properties with a very large one-dimensional aspect ratio control, so a lot of heat is transmitted along the length, through the appropriate orientation, such tubes can be synthesized with high anisotropy materials. Although the tube axis parallel to the direction of high heat exchange performance, but in the vertical direction of the heat exchange performance is low. nanotube lateral dimension than most from room temperature to 150 ℃ dielectric wavelength vibrations character large an order of magnitude, which makes the dispersion of nanotubes in the scattered phonon the formation of the interface is effective, while reducing the thermal conductivity. appropriate carbon nanotubes can be obtained very high order anisotropic thermal conductivity material.

4.4 excellent hydrogen storage properties of the hollow structure of carbon nanotubes, and compared with graphite (0.335nm) slightly larger than the interlayer spacing (0.343nm), is a more excellent hydrogen storage properties, scientists have also become the focus of .1997, AC Dillon on single-walled carbon nanotubes (SWNT) made a study of hydrogen storage properties, SWNT at 0 ℃, the hydrogen storage capacity has reached 5%. DeLuchi that: a fuel motorcycle driving 500km, consume about 31kg of hydrogen, to to project the existing tank, you need to save weight and volume of hydrogen energy density of 65% and 62kg/m3. The results of these two people has greatly increased the prospects for carbon storage of hope.

5 Application of Carbon Nanotubes
Since carbon nanotubes have excellent electrical and mechanical properties, is considered the ideal add-phase composite materials. Nanotubes as a strengthening phase and conductive phase, in the field of nano-composite materials have great potential for Application.

5.1 Electrochemical carbon nanotube devices with very high specific surface area, conductivity and good mechanical properties, is an ideal material for the required field of electrochemistry. Nanotube capacitors have a very good discharge performance, the time in milliseconds the energy stored within the entire release, this superior performance in hybrid electric vehicles began to experiment with. As in the instantaneous release of large current, as the car accelerated to provide instant energy, while wind power can also be used for voltage and small-scale solar power system stability energy storage power generation system. lithium-ion battery is one of the areas of carbon nanotube applications. nanotube lithium-ion battery capacity, discharge speed, charge and discharge capacity of 1000mA.h / g, significantly higher than that of graphite (372mA.h / g and the ball millstone Toner (708mA.h / g.

5.2 Hydrogen Storage Carbon storage is a great development potential areas of application at room temperature, atmospheric pressure, about 2 / 3 of the hydrogen is released from the carbon nanotubes, and can be used repeatedly. Carbon storage Hydrogen fuel cell materials for hydrogen storage system, the development of electric cars is significant, can replace existing high-pressure hydrogen tank, electric vehicles to improve safety.

5.3 The field emission device academic and industry Research on carbon nanotube electronic devices focused on the presence of emission control (electron gun, the main field emission flat panel displays can be applied (FED, fluorescent lamps, gas discharge tube and microwave generator. Nanotube flat panel displays is the most attractive potential applications and commercial value of one of the areas.

5.4 Carbon nanotube field-effect transistor field-effect transistors confirmed the successful development of a strong successor to carbon nanotubes as the feasibility of silicon. Especially the present, scientists can no longer by reducing the size of silicon chips to improve speed case, the role of nanotubes will be more prominent.

5.5 catalyst support [3] carbon nanotubes as small size, large surface area, the surface of the key state and different grains, the surface atoms as a result of failure to increase the surface active sites is an ideal catalyst support material.

5.6 Carbon nanotube modified electrode active center of biological molecules can promote the electron transfer can increase the relative activity of enzyme molecules. Compared with other carbon electrodes, carbon electrodes due to their unique electronic properties and surface microstructure , can greatly enhance the electron transfer rate, showing excellent electrochemical performance. CAI Chen-Xin et al [4] reported that the HRP in carbon nanotubes (CNT) modified GC electrode surface of the fixed and direct electrochemistry. Yin Feng et al [5] the multi-walled carbon nanotubes and polyacrylamide layer self-assembly of glucose biosensor was prepared, and its high sensitivity, anti-interference ability. reposted elsewhere in the Research Papers Download http://www.hi138.com
Because carbon nanotubes have a special interaction between biological materials, it has been applied to carbon nanotubes to chemical and biological analysis, many scholars at home and abroad on the carbon nanotubes have been in the field of bio-sensor applications a large number of theoretical and practical Research, and has made a breakthrough, it shows that carbon nanotubes as electrode materials of new applications.

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[5] Yin Feng, Zhao Zixia, Wu Baoyan. Multi-walled carbon nanotubes and polypropylene based layer self-assembly of glucose amine biosensors [J]. Analytics .2007.35 (7) .1021-1024. Links http://www.hi138.com Research Papers Download