Abstract
The discovery of carbon nanotubes (CNTs) has sparked great interest in the scientific world because of their remarkable electrical and physical properties. Only a thorough understanding of these properties, however, will allow CNTs to be commercially viable. Essentially, CNTs are graphite-like surfaces of sp2 hybridized carbon atoms in the form of tubes. CNTs could range from single-walled carbon nanotubes (SWNTs), consisting of one cylindrical graphite sheet to multi-walled nanotubes (MWNTs) that have concentric sheets. Nanotubes can be synthesized using a number of techniques such as electric arc–discharge, laser ablation and catalytic chemical vapor deposition (CCVD). In this project the CCVD technique was used for the synthesis of CNTs because of it simplicity and availability. The source of carbon was not the conventional hydrocarbon gas, but was camphor, a botanical hydrocarbon that is a solid at room–temperature. Ferrocene was the catalyst, not only because it has been used before in the synthesis of nanotubes, but it appears to be one of the best catalysts during the CCVD synthesis of nanotubes. The presence of nitrogen gas is known to assist in the synthesis of CNTs that have a bamboo–like structure; hence the effect of carrier gases such as nitrogen, argon/hydrogen and argon on the quality of nanotubes synthesized was investigated. Initially, the optimal experimental method for the synthesis of CNTs was determined by varying the reaction path length, temperature, mixing the catalyst and carbon source together or keeping them separate and varying
the %m/m of the catalyst to carbon source. It was found that either an increase in the reaction temperature or an increased path length resulted in an increase in the mass of product obtained, whereas mixing the catalyst and carbon source together as opposed to them being separated only caused a slight variation in the mass of product synthesized. The mass of product synthesized also increased as the catalyst concentration increased.
The remainder of the project was aimed at investigating the role of different gases: nitrogen, argon and hydrogen (in argon) in the CCVD synthesis of CNTs. The resulting materials were characterized using transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and laser Raman analysis. The results indicated that this method could be tailored to synthesize either carbon spheres or carbon nanotubes of specific diameters and quality.
Finally, in an attempt to synthesize aligned carbon nanotubes, catalyst supports {characterized using Brunauer-Emmett-Teller analysis (BET)} namely; silica, alumina and magnesium oxide were used. Although this was not successful for the synthesis of aligned CNTs under the conditions used, alumina showed the most promise.
Mr. S. Durbach
Dr. R. W. Krause