【作者】 杨光敏；

【导师】 郑伟涛；

【作者基本信息】 吉林大学 ， 材料物理与化学， 2010， 博士

【摘要】 随着纳米技术的飞速发展,纳米碳材料越来越受到人们的关注。由于碳原子具有良好的成键性能,碳元素组成的物质具有多种丰富的形貌和优良的性能。近年来,纳米金刚石、碳纳米管及其复合物、碳球等碳基材料受到了人们的广泛关注。碳纳米管以其高的长径比、良好的导电性、化学稳定性、热稳定性和力学性能而成为理想的场发射冷阴极材料之一。研究表明,将碳纳米管和其它材料复合后,将会获得场发射性能更加优异的材料。近几年来,碳纳米管复合物的研究已经成为碳纳米管应用研究的热点之一。在本文工作中,我们采用PECVD方法,通过对基片采用不同的预处理和选取不同的沉积参数,成功地合成了碳纳米管及碳纳米管/纳米金刚石复合物,并探讨了它们的生长机制和场发射性能;此外,我们还合成出树状碳纳米管和翅膀状碳纳米管,并探讨了不同形貌的碳纳米管生长机制及其场发射性能。由于碳纳米管具有独特的结构特点和稳定的化学性质,因此可以作为金属、无机材料、聚合物、以及生物分子的理想载体。金属铁、钴、镍等磁性纳米颗粒在空气中或酸性环境中是不稳定的,因此近年来人们一直在探索将硅、有机聚合物以及碳等作为纳米金属颗粒保护壳。然而,目前所面临的挑战是如何用一种简单的方法合成尺寸可控的碳包覆的金属纳米颗粒。在本文工作中,我们采用PECVD方法,合成出碳纳米管/碳包覆的铁纳米颗粒复合物,并研究了其磁学特性。在现代科学和技术中,空心碳球可以应用到很多行业中,如作为新型电极材料、气体储存材料、药物传输工具、催化剂的载体等。随着越来越多的科研工作者成功制备出空心碳球,其生长机制众说纷纭。在本文工作中,我们采用PECVD方法合成了非晶空心碳球,并探讨了其生长机制。更多还原

【Abstract】 With the rapid development of nanotechnology, much interest has been paid to the nano-carbon materials. As the carbon atoms can form several kinds of bonding, carbon materials have ample morphology and excellent properties. Recently, especially nanodiamond, carbon nanotube and their composite, carbon sphere have attracted much attention. To develop CNT-based field electron emission (FEE) devices, a lot of efforts have been implemented to synthesize the hybrid CNTs, in particular, hybrid CNTs and ND, with the enhancing FEE properties. The unique mechanical and electronic properties of CNTs and ND make both promising candidates for use as microelectronic devices. Because of the excellent FEE property of CNTs and ND, it can be speculated that the synergistic effect of CNTs and NCD will give rise to the materials with more improved FEE property that could be advantageously used as cold-cathode field emitter. So far, although the FEE properties of the tree-like CNTs have been investigated, its FEE peoperty needs to be improved. Furthermore, the FEE properties of the wing-like CNTs have not been reported. Therefore, the mechanism underlying the enhancement of FEE properties in the tree- and wing-like CNTs need to be explored.Due to their nanoscaled and steady structure characteristics and morphologies, as well as inert and resistance properties, CNTs have been considered as ideal supports for metal, inorganic materials, and coatings to biomolecules. Recent advances in attachment of metal nanoparticles to CNTs provide a way to obtain novel hybrid materials with useful properties for gas sensor, catalytic application, conducting and magnetic materials. As metallic nickel, iron, cobalt ferromagnetic nanoparticles are inherently instable in air and acid atmosphere, which limits their potential applications and scientific studies, a way to deposit a protective shell, such as silica, organic polymers, or carbon, has been recommended and been researched widely for many years. However, to obtain a simple method for preparing carbon encapsulated metallic nanoparticles with controllable size in a high yield is still a challenge.Hollow carbon spheres (HCSs) can be used to develop electrode, gas storage media, drug delivery devices, artificial cells, protectors for sensitive components and supports for catalysts, hollow sphere composites, or even used as templates for synthesis of other useful hollow spheres, which means that HCSs have many potential applications. Up to now, various methods have been used for synthezing HCSs, a lot of growth mechanism has been presented, but they are often in contradiction wih each other. In this thesis, we try to reveal the growth mechanism of Amorphous HCSs synthesized by PECVD.In Chapter 1, we give a brief introduction to the structures, properties, syntheses and applications of nanodiamond, carbon nanotube and its composite, carbon sphere, etc.In Chapter 2, we give a detailed description on the experiments for preparing and characterizing samples, as well as the working principles of PECVD and magnetron sputtering.In Chapter 3, Micro-Diamond, Nanodiamond, CNTs/Nanodiamond nanocomposite and CNTs have been synthesized via different nucleation pretreatment schemes and deposition conditions, and their growth mechanism and field emission properties have been investigated. We find that the pretreated substrate and the gas flow rate ratio of H2/CH4 are critical to the size, nucleation density and microstructure of the obtained sample. We also find that the CNTs/nanodiamond exhibits a more excellent FEE property than either CNTs or nanodiamond.In Chapter 4, both the tree- and wing-like CNTs have been synthesized, and we find that the branch diameters of the tree-like CNTs are controlled by changing the quantity of ferrocene contents and the density of graphitic sheet in the wing-like CNTs is controlled by the deposition time. The FEE properties for tree- and wing-like CNTs have been significantly enhanced compared to pristine CNTs. The diameters of the branches and branch alignment in CNTs are the main factors to influence the FEE properties of tree-like CNTs. In contrast, the density of graphitic-sheet in CNTs plays a key role in determining the FEE properties of wing-like CNTs.CNTs-carbon encapsulated Fe nanoparticles can be synthesized via a straightforward method. This nanocomposite exhibits a ferromagnetic behavior at room temperature. As Fe nanoparticles with a small size decorate on the MWCNT surface, Ms reduces, compared to bulk Fe (Ms = 222 emu/g). In contrast, compared to bulk Fe (Hc≈1 Oe), an enhancement in coercivity for carbon encapsulated Fe nanoparticles supported on CNTs (Hc = 60 Oe) is observed.In Chapter 5, we synthesize Amorphous HCS, with diameters ranging from 100-800 nm. A mechanism for the Amorphous HCS has been proposed. It is found that MgO and Ni nanoparticles together with hydrogen play important roles in the formation of the spheres.In conclusion, we have synthesized the CNTs-based nanocomposite, including CNTs/nanodiamond, tree-like CNTs and wing-like CNTs, and investigated their FEE property. The findings in this work provide a design principle for developing CNT-based nanomaterials with superior FEE properties and new insight into their potential applications as field emission devices. In addition, we have also synthesized CNTs-carbon encapsulated Fe nanoparticles and explored its magnetism property. We have also presented a growth mechanism for the growth of Amorphous HCSs, which is quite different from the existing mechanisms .更多还原