| With the development of nanotechnology, nanomaterials have become the basis of multidisciplinary research. They play an increasingly important role in chemistry, physics, energy, biomedicine, and many other fields. Because of the unique structure and excellent chemical and physical properties, carbon nanotubes have been continuously attracting increasing interest in the scientific community in the past two decades. Intuitively, carbon nanotubes are hollow nano-tubes, their diameters are in0.4-100nm. According to the graphite layers, carbon nanotubes are divided into two kinds of single-walled and multi-walled. Carbon nanotubes have excellent mechanical, electrical and optical properties and thermal stability. Carbon nanotubes are mainly studied as a variety of nano-scale devices, but the complexity and controllability of the structure severely limit their large-scale application, so more and more attention is turned to carbon nanotubes macroscopic bulk materials in recent years. However, because of random distribution,the carbon nanotube bulk material properties are much lower than the single carbon nanotube. How to fabricate aligned carbon nanotube bulk materials has become more urgent.Chemical vapor deposition synthesis of high-quality aligned carbon nanotube array was studied in this dissertation. And then we further fabricated aligned carbon nanotube fibers on this basis. We focused on two aspects research of the aligned carbon nanotubes in energy field. Firstly, we etched carbon nanotube arrays by using DC glow plasma technology to synthesize end-functionalized carbon nanotube arrays, to improve the comprehensive performance of their application in supercapacitors. Secondly, the novel dye-sensitized solar cells based on carbon nanotube fibers as working electrode have high photoelectric conversion efficiency. The main content was detailed in the following.Firstly, long aligned carbon nanotube array by chemical vapor deposition synthesis without water-assisted was firstly fabricated in this thesis. By optimizing growth temperature, time, controlling the carbon source, carrier gas, reducing gas ratios and flow rates, improving the catalyst preparation process, we prepared high-quality aligned carbon nanotube array. In the case of the total flow rate remaining unchanged, by adjusting the ratio of reducing gas of hydrogen and carbon source of ethylene, we prepared super-long aligned carbon nanotube arrays (up to4mm in height). This method has good universality, and the growth process is simple and controllable for high preparation efficiency.Secondly, spinnability of carbon nanotube arrays was systematically studied. The majority of reported carbon nanotube arrays were not spinnable. The height of spinnable array was often less than0.9mm in the reported literature. On the other hand, the physical properties of carbon nanotube array and fiber are closely related to height of the array. Higher qulity of aligned carbon nanotubes array material, better the performance. In this thesis, the deposition rate and thickness of catalyst, the proportion of various gases, the reaction temperature and time can impact spinnability of the carbon nanotube arrays, and we summed up a series of universal law, gained best synthesis parameters of spinnable carbon nanotube arrays. With spinnable array as initial material, aligned carbon nanotube fibers were continuously fabricated by dry spinning. We mainly study the excellent mechanical and electrical properties of carbon nanotube fibers, tensile strength was up to1GPa, and conductivity was up to102-103S/cm at room temperature.And then, aligned carbon nanotube arrays were studied in the application of energy storage. DC glow discharge plasma was used to etch the end cap of carbon nanotube array. Without destroying the overall shape of carbon nanotube arrays, we can open carbon nanotube ends by using plasma etching. Comparison of oxygen, argon, oxygen-argon mixture plasma etching efficiency, which showed that oxygen-argon mixture plasma etching was best. Carbon nanotube arrays were etched as electrode materials to build a super-capacitor, and we found that capacity of the capacitor was greatly improved. Finally, aligned carbon nanotube fibers were studied in the application of the photoelectric conversion. With excellent mechanical and electrical properties and high specific surface area, aligned carbon nanotube fibers were used as the working electrode to build a novel dye-sensitized solar cell. The typical build process included three parts: adsorption of N719dye molecules through the solution process to form the carbon nanotube composite fiber; carbon nanotube composite fiber was closely adhered to the fluorine-doped indium tin oxide conductive glass, and platinum was used as counter electrode of the cell; and finally they were packaged after injection of electrolyte. Photoelectric conversion efficiency of the novel fiber solar cells was up to1.69%, and it has very good stability. |
