Synthesis, Mechanism And Property Of Carbon Nanotube Bundles

• Main Authors: Yi-Ying Wu, 吳宜穎
• Other Authors: Chien-Chong Chen
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/21186311454115934588

碩士 === 國立中正大學 === 化學工程研究所 === 101 === The goal of this thesis is to prepare CNT bundles using a CVD process, to propose a growth mechanism, and to measure the electrical and thermal properties. The Fe-Co/Al2O3 catalysts were prepared by the calcination of powders in air under different temperature, where powders were obtained from drying of the mixture of desired ratio of aluminum nitrate, iron nitrate and cobalt nitrates. Mixture of CNTs and CNT bundles was successfully synthesized by a thermal CVD process, where acetylene was the carbon source, ammonia was the reduction agent, argon was the ambient gas, and the heating temperature was ranged from 600 to 900 °C. As molar ratio (Al/Fe-Co) increased, all the CNT bundle’s index (yield, length, width, aspect ratio) first increased then decreased. The molar ratio to produce the best index was 4 (calcination and reaction temperature was 450 and 700 °C, respectively), producing a 592 % yield, 160.96 μm length, 6.65 μm width, and 24.2 aspect ratio. The morphology of this CNT bundle was 3D cylinder-like aligned CNTs. Inspiring from the observations that yield and width of CNT bundles were, respectively, highly correlated with number and size of the ‘plate-like’ alumina in catalyst, a growth mechanism of CNT bundles was proposed. Alumina plates were formed during calcination, and tiny catalytic particles (FeCo or other forms of Fe and Co compounds) were sitting on the plates. When the molar ratio was proper, catalytic particles were nicely arranged in a way resembled to the catalyst particles sputtered on the substrate. This resulted in a locally well-aligned CNT bundle was growth from the well-organized catalytic particles on alumina plate, similar to the growth of the CNT array. Therefore, the key to synthesize CNT bundle is the formation of alumina plates in catalyst. Since, further tuning of process parameters (calcination temperature raised from 450 to 600 °C, reaction temperature performed at 600, 800 and 900 °C), could not produce more alumina plates, yield and quality of CNT bundles could not exceed the result obtained at 450 °C calcination temperature and 700 °C reaction temperature. For the properties of CNT bundles, CNT bundles remained in tact after grinding and was separated into randomly placed CNTs when was ultrasonicated in solvent. The resistance of conductive thin film prepared from the CNT bundles was 164.523 ( Ω / □), comparable to the reported value in literature. From the TGA analyses, the decomposition temperature increased with the larger ratio of CNT bundles in products, exhibiting better thermal quality.