Effect of NH3 environmental gas on the growth of aligned carbon nanotube in catalystically pyrolizing C2H2
| Autor: | Jin-Koog Shin, Young-Joon Baik, Minjae Jung, Kwang-Ryeol Lee, Kwang Yong Eun, Sung-Tae Kim |
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| Rok vydání: | 2001 |
| Předmět: |
Nanotube
Materials science Passivation Metals and Alloys chemistry.chemical_element Nanotechnology Surfaces and Interfaces Carbon nanotube Decomposition Nitrogen Surfaces Coatings and Films Electronic Optical and Magnetic Materials Catalysis law.invention chemistry Chemical engineering law Materials Chemistry Cobalt Carbon |
| Zdroj: | Thin Solid Films. :150-155 |
| ISSN: | 0040-6090 |
| DOI: | 10.1016/s0040-6090(01)01442-0 |
| Popis: | It has been well known that vertically aligned carbon nanotubes (CNTs) can be grown by thermal CVD in NH 3 environment. However, the mechanism of the vertically aligned CNT growth is yet to be clarified. In the present work, we investigated the effect of NH 3 gas on the CNT growth in the viewpoint of catalyst passivation. The particles of Ni or Co of diameter ranging from 17 to 58 nm were used as the catalyst. CNTs were deposited at 950°C using C 2 H 2 in various environments of NH 3 , H 2 , or their mixtures. In H 2 environment, significant catalyst passivation was observed at the C 2 H 2 concentration of 2.4 vol.% due to the excessive supply of carbon. However, vertically aligned CNTs were deposited in NH 3 environment even when the C 2 H 2 concentration was 16.7 vol.%. From the composition analysis of the catalyst surface, we could show that activated nitrogen atoms were generated by the decomposition of NH 3 . Two possible roles of the nitrogen were suggested based on the bamboo growth model. The nitrogen atoms enhance the formation of graphitic layer and/or improve the separation kinetics of the graphitic layer from the catalyst. The growth behaviors without the pre-treatment for 1 h in NH 3 environment showed that the role of the nitrogen appeared in different ways depending on the catalyst materials. In the case of Co catalyst, where vertically aligned CNT growth was observed without the pre-treatment, enhanced formation of the graphitic layer might be the significant role of the nitrogen. However, when using Ni catalyst, the pre-treatment in NH 3 environment was required for the CNT growth, which implies that both the formation and the separation of the graphitic layer were essential. |
| Databáze: | OpenAIRE |
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