【作者】 孔凡志；

【导师】 张孝彬；

【作者基本信息】 浙江大学 ， 材料物理与化学， 2003， 博士

【摘要】 一维纳米材料，是指在径向上尺寸小于100nm，长度方向上的尺寸远大于径向，长径比可以从十几到上千上万的一类材料，在材料科学中属低维材料(low-dimensional materials)范畴。从形态和结构上看，一维纳米材料可以根据其空心或实心，以及形貌不同，可分为三类：纳米管(nanotubes)、纳米棒(nanorods)或纳米线(nanowires)、纳米带(nanobelts)；而从其用途出发，又可区分为一维纳米结构材料与一维纳米功能材料两大类(有不少纳米材料可同时兼有这两项性能)。鉴于一维纳米材料的独特形貌、量子效应及其优异性能，它已经成为一个非常前沿和具竞争性的研究领域。本论文主要涉及一维纳米功能材料的研究。 本文首先介绍和回顾了国内外在纳米碳管的结构、储氢性能和氧化物等一维纳米材料，特别是二氧化锗、β-氧化镓和氧化锌制备及表征等方面的研究和发展情况。尽管对于纳米碳管的储氢性能，目前学术界存在很大的争议，所报道的实验和理论计算结果存在较大的差异，但这更体现了它是一个非常具有挑战性的研究领域，有必要继续深入研究探索。而功能氧化物一维纳米材料所具有优异的性能，特别是电学和光学性能方面，其制备方法、性能及潜在的应用性已经成为一个国际上的研究热点。 采用XRD和Raman光谱，在650-850℃温度范围内，研究了催化裂解乙炔法制备的多壁纳米碳管的石墨化程度变化规律，结果表明纳米碳管的石墨化程度随生长温度的提高而提高。这种现象与不同温度下碳原子在催化剂表面的迁移和析出速率密切相关，也即与不同温度下催化剂的活性有关。在较低温度时，由于催化剂的活性较低，导致石墨面在生长过程中引入的缺陷较多；另一方面，碳原子在催化剂颗粒内迁移速率较低，使得多余的游离态碳原子(或原子团)可能在纳米碳管表面以非晶形式沉积，或者包覆催化剂使其“中毒”失去催化活性，或者直接形成非晶的碳纳米颗粒。在较高温度时，随着催化剂活性的提高以及碳原子在催化剂颗粒表面的迁移速率的增加，可提供更多的碳原子用于纳米碳管的有序生长，减少了缺陷的引入。反应温度高时，纳米碳管结晶性好的另一原因是，纳米碳管壁上的碳原子活性提高，可自行调节其位置的动能增加，可局部迁移并浙江大学博士学位论文形成能量较低的有序排列位置，从而减少了缺陷的生成。 研究了预处理对于多壁纳米碳管储氢性能的影响。在氮气中进行退火处理纳米碳管的储氢性能高于在空气中退火的纳米碳管，主要原因是在空气中退火时，纳米碳管的表面引入了大量的氧官能团，而氧官能团能够占据纳米碳管的缺陷位，减少了氢的可吸附位置，阻碍氢进入纳米碳管，从而降低了纳米碳管的储氢能力。在KNO3溶液中进行液相搀杂的纳米碳管，其储氢能力明显提高，并且随掺杂浓度增加而提高。室温下纳米碳管吸附的氢气不能完全脱附，说明纳米碳管的吸氢方式包括物理吸附和化学吸附，其中化学吸附比较难于释放。实验中使用了高纯氢气(纯度为99.9999%)，排除了氢气纯度不高、含有水汽等造成的误差。 优化了多壁纳米碳管化学镀镍的参数。经过纯化、敏化处理的多壁纳米碳管己具有较好的催化表面，采用合适的化学镀液，可以得到连续致密的镀覆层。根据对相同镀液和参数、不同时间获得的产物的表征，发现金属镍首先以纳米颗粒的形式在纳米碳管表面的催化中心沉积，继而形成连续及紧密结合的镀层。纳米碳管的曲率对于化学镀的影响不大，关键在于预处理过程中形成催化中心的分布J清况。分布均匀、致密的催化中心对于得到光滑连续的镀层较为有利。 采用氧化物辅助一纳米碳管诱导反应制备出了二氧化锗纳米线，并在产物中首次发现分枝牙状生长的二氧化锗纳米线。通过对比实验推断，在初始生长过程中，纳米碳管起到了模板作用，可诱导二氧化锗沿一维方向生长;此后，通过反应不断生成二氧化锗并沉积到已生成的纳米线上，在径向和轴向上继续生长。对反应产物的观察表明，纳米碳管对纳米线的尺寸并没有起到限制作用。对二氧化锗纳米线进行了系列倾选区电子衍射研究，构造出了其相应的倒空间，确定其结构为六方。 应用碳热还原反应，成功地制备了氧化嫁纳米线、纳米带和纳米片。纳米碳管在反应中充当碳源，而没有起到限制效应。反应物中未加入催化剂，氧化稼纳米产物的端部也没有发现任何催化剂颗粒，说明氧化嫁纳米产物遵循VS生长机理。利用选区电子衍射，对单根纳米线进行系列倾测试，构造出了其相应的倒空间，结合x射线衍射，确定其晶体结构为单斜;表征了之字形貌短纳米棒的孪晶结构，首次发现孪晶并非完美的镜面对称，其主要原因归于氧化稼材料的单斜结构。对不同形貌氧化嫁纳米结构的室温光致发光实验证明它们是很强的蓝光发纳米碳管和氧化物一维功能纳米材料的制备与表征射材料，发射峰中心位于487nm。 PEG是一种长链分子，对于氧化锌的一维生长可以起到诱导作用。从实验中得到的结果分析推断，氧化锌晶体的形核主要发生在PEG长链上，然后作为生长单元的四面体进行有序堆积，呈辐射状向外生长。在不同浓度更多还原

【Abstract】 One-dimensional nanomaterials have radius less than 100nm, length much larger than radial size and the aspect rario can reach tens even thousands. According to the structure and morphology of these materials, which are solid or hollow for example, one-dimensional nanomaterials can be divided into three different kinds, i.e. nanotubes, nanorods (or nanowires), nanobelts (or nanoribbons). Since their unique morphologies and excellent properties, one-dimensional nanomaterials have attracted great interests of researchers for decades.The research developments related to structure and hydrogen storage property of carbon nanotubes, and functional oxide one-dimensional nanomaterials, especially GeO2, B-Ga2O3 and ZnO were reviewed in this thesis. Until now, there aree still great disagreements in the hydrogen storage property of carbon nanotubes, and the reported experimental and theoretical results are too different to obtain a common conclusion. However, it is unfair for the time being to compare carbon nanotubes for hydrogen storage at the same level as metal hydrides or other established storage technologies, as not yet enough research has been carried out. On the other hand, functional oxide one-dimensional nanomaterials have become a new attractive research subject in the modern world, due to their excellent properties, specially, the novel electronic and optical properties.Using XRD and Raman spectrum, in the temperature range of 650-850℃, the rule of graphitization of multiwalled carbon nanotubes synthesized by catalytic decomposition of C2H2 was found: graphitization of multiwalled carbon nanotubes was improved with the increase of growth temperature. This phenomenon was closely related to the transportation and extraction rate of carbon atoms in the surface of catalysts at different temperatures. At lower growth temperature, the lower extracting rate of carbon atoms from catalyst particles due to the lower activity of the catalysts resulted in more defects formed in carbon nanotubes. Moreover, the lowertransportation rate of carbon atoms in catalyst particles also made lots of carbon atoms deposited on the surfaces of grown carbon nanotubes, or on carbon wrapped catalyst particles, even to form amorphous carbon layers. When the growth getting higher, the migration rate of carbon atoms was increased, more carbon atoms would pass through catalyst particles to contribute the growth of carbon nanotubes, which increased the growth rate and also resulted in less defects in carbon nanotubes. Another possible reason for this phenomenon is that with higher temperature, the mobility near defects of carbon atoms in grown carbon nanotubes would be also elevated, which gave carbon atoms higher mobility and have chance to readjus to decrease or eliminate some defects.A series of pretreatments and modifications including purification, annealing and doping were performed before hydrogen storage experiments carried out at room temperature under modest pressure (12MPa). The hydrogen source used is high purity of 99.9999%. For comparison, the annealing treatments were processed under ambient pressure in air and nitrogen atmosphere respectively. KNO3 solutions (0.1 mol/L and 1.0 mol/L) were used to dope carbon nanotubes. The results show that MWNTs annealed in nitrogen adsorbed more hydrogen than those annealed in air. FTIR spectra of the samples shows that the amount of oxygen functional groups linked to MWNTs after annealed in air was more than that treated in nitrogen. The former treatment may bring about more agglomeration of MWNTs, decrease the specific area and surface activity of MWNTs and eventually lead to lower capacity of hydrogen adsorption. The results also showed that with the same dopant, the capacity of hydrogen adsorption has great difference when the concentration of the doping solution changed. Hydrogen adsorption of MWNTs increased not only after doped in KNO3 solution but also with the increase of solution concentration in certain extent. After a typical adsorption/desorption cyc更多还原