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Paper Information

Journal:   JOURNAL OF SCIENCES (ISLAMIC AZAD UNIVERSITY)   SUMMER 2010 , Volume 20 , Number 76 (CHEMISTRY ISSUE); Page(s) 1 To 8.
 
Paper: 

PURIFICATION OF CARBON NANOTUBES GROWN ON FE/NI BIMETALLIC CATALYST SUPPORTED ON MGO BY THERMAL CHEMICAL VAPOR DEPOSITION

 
 
Author(s):  MIRERSHADI S.*, MORTAZAVI S.Z., REYHANI A., MONIRI N., NOVINROOZ A.J.
 
* PHYSICS DEPARTMENT, KARAJ BRANCH, ISLAMIC AZAD UNIVERSITY, KARAJ, IRAN
 
Abstract: 

Introduction: since the discovery of carbon nanotubes they have attracted an enormous amount of interest because of their unique physical properties and many potential applications. For many carbon nanotubes applications, purified nanotube material is often desired.
Aim: the CNTs as produced by the various synthesis techniques contain impurities such as graphite, amorphous carbon, fullerenes and metal catalyst particles. These impurities have to be separated from the carbon nanotubes before they can be used for more applications. Purification techniques have been devised in order to improve the quality and yield of carbon nanotubes. The principal aim in this research was the effect of air oxidation and acid treatment on purification of multi- walled carbon nanotubes.
Materials and methods: Carbon nanotubes (CNTs) were grown on Fe/Ni bimetallic catalysts based on MgO by thermal CVD deposition technique. The purification of carbon nanotubes is carried out under oxidation and acid treatment with hydrochloric acid solution. Various analytical techniques such as: scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and Raman spectroscopy techniques were employed to investigate the morphology, graphitization and quality of the carbon nanotubes.
Results: the scanning electron microscopy (SEM) images of the pristine CNTs (without any purification treatment) show that pristine CNTs contain many impurities and it is hard to trace nanotubes, the effect of air oxidation and acid treatment in dissolution of catalyst is quite visible. The X-ray diffraction analysis showed that the peaks of MgO and Fe/Ni catalyst were disappeared after purification. Also, the peak at 2
q=26.5owas attributed to the graphite structure indicating the purification at the samples was complete. Raman spectroscopy technique was employed to investigate the quality of the carbon nanotubes. Intensity of the G-band to Intensity of the D-band (IG/ID), are used to estimate the quality of CNTs. The IG/ID ratio for the purified MWCNTs increased to 1.7 and indicates that some of the carbon impurities or defective structures of MWCNTs have been removed from the pristine sample. The TGA result show that CNTs yield of raw, oxidized and purified CNTs are about 28.6, 22.2, 92.6 % respectively.
Conclusion: it is concluded that weight ratio of CNTs after air oxidation and hydrocholoric acid treatment were reached to 92.6 %.

 
Keyword(s): CARBON NANOTUBE, PURIFICATION, HYDROCHLORIC ACID, THERMAL CVD, BIMETALLIC CATALYSTS
 
References: 
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