碳纳米管场发射技术及电真空器件研究

发布时间：2019-03-31 14:00

【摘要】：碳纳米管（CNT）场发射电真空器件应用的技术关键是研制稳定长寿命的阴极（电子源）。目前制备CNT阴极比较常用的有两种方法，即表面沉积催化金属纳米膜的化学气相沉积（CVD）原位法和使用固化材料将CNT附着在表面的间接法。受制备技术的限制，上述两种方法都有一些由表面结合特征引发的固有缺陷,导致在不同热环境下长期工作，过渡金属（固化材料）与基底间的结合处发生错位，致使CNT薄膜脱落，影响寿命和真空性能。因此，CNT层与基底的结合性能是制约催化膜法和间接法CNT阴极应用的中心问题。本文采用热化学气相沉积法（CVD）在金属基底上直接制备碳纳米管阴极，然后将其制作成简洁的真空计。主要内容有：（1）采用CVD法按照以下生长条件：生长温度为750℃、流量比C2H2：Ar=15:200、生长时间为10min、生长压力为10Torr，，在含过度催化金属的哈氏合金片、镍片、不锈钢片和哈氏合金网材质的金属基底上直接沉积碳纳米管。此工艺既免去在基底沉积催化金属纳米膜的繁琐工艺、又实现碳管与基底的强附着；（2）应用扫描电子显微镜（SEM）和高分辨透射电子显微镜（HRTEM）对碳纳米管阴极进行了形貌结构分析表征，发现哈氏合金片上的碳纳米管分布均匀、密度适中，制备的碳纳米管为多壁碳纳米管（MWNTs），管径约为15nm，且管内含多金属（镍、铁、铬等）纳米颗粒（直径约为6nm）；（3）采用二极式场发射结构对不同金属基底的碳纳米管阴极进行场发射表征，发现哈氏合金片最优（开启电场为3.15V/um，阈值电场为5.94V/um，场增强因子为1900，以4.2mA/cm2发射20h没有衰减）；采用三极式场发射结构对哈氏合金片和哈氏合金网基底的碳纳米管阴极进行测试，发现哈氏合金片的透过率明显优于哈氏合金网的透过率，可达0.61，接近物理透过率0.77；（4）研制了基于气体吸附原理的二极式场发射结构的电真空器件—MWNTs场发射真空计，该真空计在10-8-10-4Pa的空气环境氛围下具有较高的灵敏度；（5）与兰州空间技术物理研究所合作，试制了基于IE514电离真空计的CNT场发射电离真空计，该真空计在压力为10-6-3.0×10-4pa时显示出了良好的线性。
[Abstract]:The key technology for the application of carbon nanotubes (CNT) field emission vacuum devices is to develop a stable and long-life cathode (electron source). At present, there are two commonly used methods to prepare CNT cathode, that is, chemical vapor deposition (CVD) method for surface deposition of catalytic metal nano-films, and indirect method for adhesion of CNT to the surface by means of solidifying materials. Because of the limitation of the preparation technology, both methods have some inherent defects caused by the surface bonding characteristics, which lead to the dislocation of the junction between transition metal (solidified material) and substrate under different thermal conditions for a long time. CNT thin films fall off, affecting the life and vacuum properties. Therefore, the binding performance of CNT layer to substrate is a central problem which restricts the application of catalytic membrane and indirect CNT cathodes. Carbon nanotubes (CNTs) cathodes were prepared directly on metal substrates by thermal chemical vapor deposition (CVD), and then made into simple vacuum gauges. The main contents are as follows: (1) according to the following growth conditions by CVD method: the growth temperature is 750C, the flow rate ratio is C2H2AAR 15 渭 200, the growth time is 10 min, the growth pressure is 10 Torr, and the growth conditions are as follows: 1. Carbon nanotubes (CNTs) are deposited directly on metal substrates made of stainless steel sheet and Harley alloy mesh. This process not only eliminates the cumbersome process of depositing catalytic metal nanomembrane on the substrate, but also realizes the strong adhesion between the carbon tube and the substrate. (2) the morphology and structure of CNTs cathode were characterized by scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM). The prepared carbon nanotubes are multi-walled carbon nanotubes (MWNTs),) with a diameter of about 15 nm, and polymetallic (nickel, iron, chromium, etc.) nanoparticles (about 6nm in diameter) in the tubes. (3) the field emission of carbon nanotube cathodes with different metal substrates was characterized by the bipolar field emission structure. It was found that the optimal field emission was 3.15V 路V ~ (- 1) and 5.94 V ~ (?) 路m ~ (- 1), respectively. The field enhancement factor is 1900, and there is no attenuation in 4.2mA/cm2 emission for 20 h. Using the tripolar field emission structure, the carbon nanotube cathodes of the alloy sheet and the alloy mesh substrate were tested. It is found that the transmittance of the alloy sheet is obviously better than that of the alloy mesh, which is up to 0.61, and the transmission rate of the alloy plate is higher than that of the alloy mesh. Near physical transmittance of 0.77; (4) an electrovacuum device-MWNTs field emission vacuum gauge based on the principle of gas adsorption is developed. The vacuum gauge has high sensitivity in the air environment of 10-8-10-4Pa. (5) in cooperation with Lanzhou Institute of Space Technology Physics, a CNT field emission ionization vacuum gauge based on IE514 ionization vacuum gauge has been developed. The vacuum gauge shows good linearity when the pressure is 10-3.0 脳 10-4pa.
【学位授予单位】：温州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB383.1;TB77

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