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Synthesis of Carbon Nanotubes

Alfa Chemistry
Posted on: 21 Nov 17
Synthesis of Carbon Nanotubes

Carbon nanotubes, also known as buckytubes, have many unusual mechanical, electrical and chemical properties. In recent years, with the extensive researches on carbon nanotubes and nanomaterials, its broad application prospect has also been continuously demonstrated.

 

Since it has been discovered in 1991, carbon nanotube has attracted attention from over the world due to its unique structure and extraordinary properties. Its super mechanical properties, excellent field emission properties, high hydrogen storage performance has made its a hot spot in the field of nanomaterial. So that it is very important to research the cost-effective and simple synthesis method of carbon nanotubes.

 

According to some researches, the synthesis of carbon nanotubes mainly includes arc process, laser ablation (evaporation), catalytic cracking method or catalytic chemical vapor deposition(CCVD) technique, as well as directional control growth method based on a variety of synthetic techniques, and so on.

 

1  Arc Process

It refers to electric discharge phenomena of gas. The gas space between the two electrodes become conductive under certain conditions, which transfer the electrical energy into light and heat energy. This process is usually under inert gas protection. Graphite produces an arc and discharge under the action of heavy current. The anode is consumed while the cathode is forming a deposit. Sediments are often accompanied by carbon particles, graphite fragments, amorphous carbon and various fullerenes and other impurities. By changing the experimental parameters and improving the experimental device, the yield and tructure of carbon nanotubes can be improved. Such as in 1999, M. Ishigami and other graphite anode discharge with the short copper rod (as the cathode) in the reaction chamber containing liquid nitrogen. Zha0 can produce a lot of thin and long carbon nanotubes by changing the anode, and inert gas atmosphere (He/CH4) and other experimental parameters. The shortcoming of arc process is that there are many by-products in the preparation process. Besides, it is difficult to realize continuous industrial production and the production cost is very high.

 

2  Laser Ablation (Evaporation)

Laser evaporation method is to place a metal catalyst/graphite mixed carbon target in the middle of a quartz tube in a furnace. When the furnace temperature rose to 1473K, inert gas should be injected in immediately , while a laser beam focused on the graphite target, then the carbon target transfer to gaseous carbon. Gaseous carbon and catalyst particles enter into the low temperature zone with the gas flow, carbon nanotubes can be generated in the presence of catalyst. In 1996, A. Thess obtained high quality single-walled carbon nanotubes at 1473 K by changing the experimental conditions to irradiating a carbon target containing Ni/Co(as the catalyst) with a double-pulse laser of 5ns. T. Guo studied the relationship between the type of catalyst and the yield of single-walled carbon nanotubes. And it was found that the yields of carbon nanotubes vary greatly with the types of different catalysts. Compared with the arc process, the laser evaporation method has the advantages of being capable of mass production and high yield. However, the high price of laser equipment limits its production scale.

3  Catalytic cracking method or catalytic chemical vapor deposition(CCVD) technique

Chemical vapor deposition (CVD) is the process of free carbon atoms decomposed from carbon source gas deposited on the catalyst (transition metals:Fe, Co, Ni, etc.)) to form carbon nanotubes at the temperature of 700-1200. C. The growth of carbon nanotubes is affected by the carbon source, the composition of the catalyst, the growth temperature and the like. In 1993, Yacaman first reported the successful synthesis of multi-walled carbon nanotubes by chemical vapor deposition using Fe as catalyst and acetylene as carbon reduction. The CVD method has the advantages of easy control of experimental conditions, high-yield and low-cost, and is the most promising method for synthesizing a large amount of carbon nanotubes. By controlling the mode of the catalyst, the carbon nanotubes of oriented arrays can be obtained.

For more information:
www.alfa-chemistry.com

Editor's Details

Tylor Keller
Alfa Chemistry
www.alfa-chemistry.com
support@alfa-chemistry.com

Last updated on: 21/11/2017

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