Growth of carbon nanofibers by catalytic chemical vapor deposition using Al-Ni-Cu composite catalysts
碩士 === 大同大學 === 材料工程研究所 === 93 === We synthesized carbon nanofibers(CNFs) by catalytic chemical vapor deposition(CVD) using an Al-Ni-Cu composite catalyst. Two different mixture gases (CH4/H2 and CH4/N2) were introduced as the reactants. The deposition processes were carried out at temperatures in t...
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| Format: | Others |
| Language: | en_US |
| Published: |
2005
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| Online Access: | http://ndltd.ncl.edu.tw/handle/35556905165687158230 |
| Summary: | 碩士 === 大同大學 === 材料工程研究所 === 93 === We synthesized carbon nanofibers(CNFs) by catalytic chemical vapor deposition(CVD) using an Al-Ni-Cu composite catalyst. Two different mixture gases (CH4/H2 and CH4/N2) were introduced as the reactants. The deposition processes were carried out at temperatures in the range of 650℃-750℃ with a 50℃ interval. We found that 700℃ is the most suitable synthetic temperature to produce high yield and thinner CNFs with Al-Ni-Cu catalysts. HRTEM showed that the as-grown CNFs have a bamboo-like structure.
A 3M HCl acid solution was used to remove the catalysts from the as-grown CNFs. TGA results showed that this process could remove 30wt% catalysts from 0.5g CNFs(700℃, CH4/H2). SEM images showed CNFs lost the catalysts from the tips and leave cavity at the tip position.
Heat treatments were also performed on CNFs which were produced using both CH4/H2 and CH4/N2 atmospheres at 700℃. At the annealing temperature of 2400℃, the loop structure was observed in HRTEM for CNFs produced by a CH4/H2 mixture gas. With the heat treatments, the Raman spectrums of CNFs showed clearly 2D band that have a stronger intensity in comparison with the G band. No obvious loop structure has been seen on the surface of CNFs which were produced by a CH4/N2 atmosphere and were heat-treated at 2400℃. And the intensity of 2D band is also weaker than that of G band. Metal particles were evaporated after a 2400℃ heat treatment. XRD data showed that the composite catalyst transformed into AlNi3 and AlNi phases during 1600℃-2000℃.
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