| Summary: | 碩士 === 國立臺灣大學 === 化學研究所 === 91 === Carbon nanotubes (CNTs) have attracted much interest since the discovery in 1991 due to their scientific importance and potential applications. The structure and properties of CNTs have been intensively studied theoretically and experimentally, and several methods have been developed for mass production of CNTs. However, the growth mechanism of CNTs has not been fully understood yet. In this study, nickel nanoparticles were used as the catalyst. Multiwall nanotubes (MWNTs) were synthesized from acetylene by Ni-assisted thermal chemical vapor deposition (CVD), and the growth behavior was investigated.
A detailed systematic study on the growth morphology of Ni nanoparticles and CNTs on silica was undertaken. It showed that (1) the size of the nanoparticles may be carefully controlled by adjusting experimental parameters, such as the thickness of the deposited Ni film and the reaction temperature, (2) there was a strong correlation between the catalyst particle size and the CNTs diameter, and (3) the growth mechanism in the temperature regime below 950K may be different from the one in the high temperature.
The interface properties between Ni nanoparticles and the silica surface as well as the surface reaction of acetylene on the silica and Ni naoparticles/silica surfaces have been studied using temperature- programmed desorption (TPD), secondary ion mass spectroscopy (SIMS), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES). Studies using (methods) revealed that metallic Ni nanoparticles were stable on the silica surface in the temperature range below 850K. SSIMS and XPS results showed that at -150oC, C2H2 adsorbed on the Ni nanoparticle surface, partly forming chemisorbed C2H and H surface species. As the surface temperature was increased, both C2H2 and C2H decomposed to form carbidic carbon. After annealing the substrate to 600oC, most carbon atoms on the surface were transformed to yield graphite layers.
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