【作者】 刘勇；

【导师】 朱正吼； 孙晓刚；

【作者基本信息】 南昌大学 ， 材料学， 2006， 硕士

【摘要】 本文首先采用管式反应炉以二茂铁作为催化剂先驱体、二甲苯作为碳源、以Ar／H₂为载气、以石英板或石英片作为基底制备了定向碳纳米管薄膜。通过向反应室引入适量的水蒸气，选择性的除去非晶碳，延长催化剂的寿命，获得了厚达2mm的大面积定向碳纳米管薄膜。其次研究了向反应室引入氨气对定向碳纳米管薄膜的影响。采用扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X射线衍射仪（XRD）以及高分辨扫描电子显微镜（HRSEM）和高分辨透射电子显微镜（HRTEM）对碳纳米管进行了表征。最后研究了碳纳米管、稀土掺杂碳纳米管、定向碳纳米管薄膜的吸波性能。研究结果表明：当向反应室引入水蒸气合成毫米级长度的碳纳米管时，生长温度宜控制在850℃左右；在载气总流量为2000ml／min（Ⅰ路Ar／H₂1600／200ml／min、Ⅱ路Ar 200ml／min，其中第Ⅱ路Ar携带水蒸气）、生长温度为850℃、生长时间60min等相同条件下，随着二茂铁浓度的增加，碳纳米管的直径减小，碳纳米管的长度先增加后减小，在二茂铁浓度为0.06g／ml时，碳纳米管长度有最大值1.1mm；水的引入量（由第Ⅱ路Ar的流量决定）是影响催化剂的寿命的关键因素。在生长温度为850℃、二茂铁浓度为0.04g／ml、Ⅱ Ar为400ml／min等生长条件下，得到了长达1.75mm的定向碳纳米管；随着生长时间的延长，定向碳纳米管薄膜的厚度增加，平均生长速率先增加后降低，当生长时间为120min时，可以得到厚约2mm的定向碳纳米管薄膜；将氨气引入反应室导致定向碳纳米管薄膜形成疏密相间排列，引入氨气的量增加，定向碳纳米管薄膜的厚度降低；当CNTs／EP比为5／100，在7.91GHz处，有最大吸收值13.89，合格带宽为3.19GHz，稀土掺杂碳纳米管在8.40—16.08GHz范围内，吸收大于10dB，合格带宽7.68GHz，定向碳纳米管也具有一定的吸波性能，在13.75—18GHz频率范围内，吸收大于10dB，频宽4.25GHz。更多还原

【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更多还原