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Study on Preparation of Aligned Carbon Nanotube and Radar Absorbing Properties of Carbon Nanotube

Author: LiuYong
Tutor: ZhuZhengHou；SunXiaoGang
School: Nanchang University
Course: Materials Science
Keywords: Carbon Nanotube Aligned Carbon Nanotube Chemical Vapor Deposition Radar Absorption Materials
CLC: TB383.1
Type: Master's thesis
Year: 2006
Downloads: 314
Quote: 1
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Abstract


Large area aligned carbon nanotube films were grown on quartz substrates by chemical vapor deposition process. Here we used ferrocene, xylene and Argon/hydrogen as the catalyst precursor , carbon source and carrier gas, and used alundum tube as reaction chamber . A controlled amount of water vapor or NH3 was introduced into the growth atmosphere .Water vapor could selectively remove amorphous carbon and preserve catalytic activity and lifetime. NH3 have an effect on carbon nanotube films. The morphology of CNTs was characterized by SEM、 TEM、 HRSEM, HRTEM. XRD was also used to evaluate the crystallinity of CNTs. According to the phenomenon and results of experiment, the growth mechanism were discussed. Respectively, We used CNTs, rare earth/CNTs and ANTs as electromagnetic absorbing materials to study their absorption properties. The results of experiment show that the befitting growth temperature was 850℃, when water vapor were introduced into the reaction chamber. At 2000ml/min of carrier gas（ I Ar/H21600/200ml/min、 II Ar200ml/min ）and growth temperature 850℃, nanotubes diameters reduced with increasing ferrocene concentration ,but the length of carbon nanotubes is seen to increase about 1.1mm at 0.06g/ml and then decrease thereafter. Balancing the relative levels of carbon source and water was crucial to maximize catalytic lifetime. When growth temperature 850 ℃, Ferrocene concentration 0.04g/ml, I Ar/H2l600/200ml/min, II Ar200ml/min and reaction time 60min, we obtained 1.75-mm-tall CNTs films. The thickness of carbon nanotube films increased with increasing the reaction time. But the rate of growth initially increased and then reduced as the reaction time was increased. We obtained 2-mm-tall CNTs films at reaction time 120min. When NH3 introduced into the reaction chamber, the carbon nanotube films formed variable-density. The thickness of carbon nanotubes decreased with increasing the flow rate. The absorption properties of CNTs with nanotube diameter 10-30nm were studied. When the ratio of carbon nanotubes and epoxy resin was 5 I 100 ,the maximum absorbing peak of the composite obtained was 13.89dB at 7.91GHz and had a bandwidth of 3.19GHz （ R < 8dB） with 3 mm

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