Browsing by Author "Tseng, Chyuan-Yow"

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A High Efficiency Surface Modification Process for Multiwalled Carbon Nanotubes by Electron Cyclotron Resonance Plasma
(2008-11-27)
Tseng, Wen-Shou
;
Tseng, Chyuan-Yow
;
Chuang, Pi-Kai
;
Lo, An-Ya
;
Kuo, Cheng-Tzu
A novel process of surface modification for multiwalled carbon nanotubes (MWCNTs) by using electron cyclotron resonance plasma is proposed. The process uses a H(2)/O(2) gas mixture as etching gas and applies a bias voltage of -250 DCV to the process stage to extract and accelerate hydrogen and oxygen cations. The generated high density and high incident energy cations are employed to create defects on the surface of nanotubes through ion bombardment. The oxygen cations with high reduction potential are simultaneously applied, oxidizing the surface of the nanotubes so as to form functional groups on the side walls most effectively. Additionally, being far from the plasma sheath, the MWCNTs can be maintained at a lower temperature to prevent from being decomposed under the high energy plasma. The efficiency of this method was systematically analyzed using X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis. The experimental results have shown that the proposed method is a highly effective way to functionalize MWCNTs, resulting in the nanotubes with high concentration of oxygen-containing functional groups and minimal structural damage within very short process time.
Effects of Gas Composition on Highly Efficient Surface Modification of Multi-Walled Carbon Nanotubes by Cation Treatment
(2009-03-01)
Tseng, Wen-Shou
;
Tseng, Chyuan-Yow
;
Kuo, Cheng-Tzu
;
材料科學與工程學系
;
Department of Materials Science and Engineering
High incident energy hydrogen and/or oxygen cations are generated by electron cyclotron resonance system, and then used to highly efficiently modify multi-walled carbon nanotubes (MWCNTs). The effects of various H(2)/O(2) gas compositions on the modification process are studied. A systematic characterization method utilizing a combination of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, Raman spectroscopy, and thermogravimetric analysis (TGA) is used to evaluate the effects of various H(2)/O(2) gas compositions on MWCNT functionalization. The Raman results show that the I (D)/I (G) ratio is directly affected by H(2) concentration in gas mixture, and the treatment applying a H(2)/O(2) gas mixture with ratio of 40/10 (sccm/sccm) can yield the nanotubes with the highest I (D)/I (G) ratio (1.27). The XPS results suggest that the gas mixture with ratio of 25/25 (sccm/sccm) is most effective in introducing oxygen-containing functional groups and reducing amorphous carbon. The TGA suggests that the structural change of the treated nanotubes is marginal by this method with any gas condition.
Functionalizing Multi-Walled Carbon Nanotubes Using ECR Plasma and a Mild Nitric Acid Treatment
(2009-12-01)
Tseng, Wen-Shou
;
Tseng, Chyuan-Yow
;
Kuo, Cheng-Tzu
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In the present work, a two-step process combining electron cyclotron resonance (ECR) plasma and 0.25 M nitric acid treatments is utilized to functionalize multi-walled carbon nanotubes (MWCNTs). In the process, high density and high incident energy hydrogen and oxygen cations generated by using ECR plasma system are used to bombard the MWCNTs for 5 min to break C-C bonds, creating free radical defects on the nanotube surface; the treated nanotubes are subsequently sonicated in the mild acid for 2 h, forming functional groups at the defects. Several characterization techniques, including X-ray photoelectron spectroscopy, scanning electron microscopy, Raman spectroscopy, and thermogravimetric analysis, are utilized to systematically evaluate the effect of the method. The results show that the MWCNTs treated by the presented method can contain a high concentration of oxygen-containing functional groups on the nanotube surface with the added advantage of high thermal stability and minimal destructive effects to the material structure.