蓝宝石红外窗口用碳纳米管薄膜的制备及其性能调控研究

发布时间：2018-01-04 04:25

  本文关键词：蓝宝石红外窗口用碳纳米管薄膜的制备及其性能调控研究　出处：《哈尔滨工业大学》2015年硕士论文　论文类型：学位论文

  更多相关文章： 碳纳米管薄膜 化学气相沉积法 镍催化剂 钨铁催化剂 光电性能

【摘要】：蓝宝石红外窗口的电磁屏蔽防护,有着重要的理论研究和实际应用价值。碳纳米管薄膜尤其是单一手性单壁碳纳米管薄膜,具有良好的红外透过率和较好的理论导电性能,在红外窗口电磁屏蔽领域有着较好的应用前景。本论文基于碳纳米管气-液-固(VLS)和气-固-固(VSS)两种生长原理,分别以金属Ni和W-Fe合金为催化剂,在蓝宝石基底和镀有SiO_2层的蓝宝石基底上,采用化学气相沉积法(CVD)制备了一系列碳纳米管薄膜。主要采用扫描电子显微术(SEM)、拉曼光谱和透射电子显微术(TEM)表征和分析碳纳米管薄膜的生长形貌及结晶质量;采用红外光谱法测试薄膜的红外透过率;采用霍尔效应法测试其导电性能以评估其电磁屏蔽性能。以金属Ni为催化剂,CVD制备碳纳米管薄膜的实验表明,使用Ni催化剂制备碳纳米管薄膜时,Ni催化剂溅射时间不能太长,否者退火后Ni颗粒会发生重叠,不利于碳纳米管薄膜的生长。CVD法制备碳纳米管时,反应温度升高能够提高Ni催化剂活性,使碳纳米管薄膜质量变好,但是过高的温度也会让催化剂中毒失效;实验通入CH_4/H_2的流量随着H_2比例的增加,碳纳米管薄膜的质量慢慢变好,但是过量的H_2会降低反应速率使碳纳米管密度下降;Ar流量对反应的影响效果不大,当Ar流量过大时,碳纳米管团聚会变得严重;碳纳米管薄膜的厚度随反应时间延长而增加,但生长30min后碳纳米管开始停滞生长。此外,还通过对比蓝宝石镀制SiO_2层前后碳纳米管薄膜光电性能变化,研究了SiO_2层的作用,分析了SiO_2层提高碳纳米管光电性能的原因。制备新型W-Fe合金,并以其为催化剂制备碳纳米管薄膜的实验结果表明:W48Fe28Ox在高温H_2环境下退火才能形成W-Fe催化剂;W-Fe催化剂具有非常高的熔点,反应温度要达到850℃以上W-Fe催化剂才具有活性;高温下CH_4容易裂解,CH_4流量不能太大,H_2流量可适当增加来改善碳纳米管薄膜质量。比较以SiO_2为过渡层使用Ni催化剂和直接基于蓝宝石以W-Fe为催化剂制备的碳纳米管,采用拉曼散射光谱和TEM分析表明,W-Fe催化剂制备的碳纳米管直径比Ni催化剂制备的碳纳米管要小且无定形碳杂质少。因而使用W-Fe催化剂制备碳纳米管薄膜质量更好,将具有更高红外透过率和导电性能,在红外窗口电磁屏蔽领域具有更好的应用前景。
[Abstract]:The electromagnetic shielding of sapphire infrared window has important theoretical research and practical application value. Carbon nanotube thin film, especially single chiral single-walled carbon nanotube film. It has good infrared transmittance and good theoretical conductivity. This thesis is based on the two growth principles of carbon nanotube gas-liquid-solid VLS and gas-solid-solid VSS. Metal Ni and W-Fe alloys were used as catalysts on sapphire substrate and sapphire substrate coated with SiO_2 layer respectively. A series of carbon nanotube films were prepared by chemical vapor deposition (CVD), mainly by scanning electron microscopy (SEM). Raman spectroscopy and transmission electron microscopy (TEM) were used to characterize and analyze the morphology and crystallization quality of carbon nanotube films. Infrared transmittance was measured by infrared spectroscopy. Hall effect method was used to test its electrical conductivity to evaluate its electromagnetic shielding performance. The experimental results of carbon nanotube films prepared by CVD using Ni as catalyst show that when Ni catalysts are used to prepare carbon nanotubes films. The sputtering time of Ni catalyst can not be too long, and the Ni particles will overlap after annealing, which is not conducive to the growth of carbon nanotube thin films. The increase of reaction temperature can improve the activity of Ni catalyst and improve the quality of carbon nanotube film, but too high temperature will also make the catalyst toxic. The mass of carbon nanotube films gradually improved with the increase of the ratio of H _ 2 to CH_4/H_2, but excessive H _ (2) decreased the reaction rate and decreased the density of carbon nanotubes. The effect of ar flux on the reaction is not obvious. When ar flow is too large, the CNTs congregation becomes serious. The thickness of carbon nanotube films increased with the increase of reaction time, but the growth of carbon nanotubes began to stagnate after 30 minutes of growth. The role of SiO_2 layer was studied by comparing the photoelectric properties of carbon nanotube films before and after sapphire SiO_2 coating. The reasons for improving the photoelectric properties of carbon nanotubes by SiO_2 layer were analyzed and a new W-Fe alloy was prepared. The experimental results show that the W-Fe catalyst can be formed only by annealing at high temperature under the condition of H _ (2) _ (2) at 1: W _ (48) Fe _ (28) O _ (x). The W-Fe catalyst has a very high melting point, and the reaction temperature is more than 850 鈩，

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