【作者】 钟博；

【导师】 温广武；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2011， 博士

【摘要】 作为C微纳米材料的类似物,BN微纳米材料具有低密度、耐高温、抗氧化、生物相容性好等一系列优点,在紫外激光器件、生物传感器、复合材料增强体、储氢材料等诸多领域具有广阔的应用前景。但是与C微纳米材料相比,BN微纳米材料的制备却面临着许多困难,如对反应条件要求苛刻,产物的产量低、纯度差等。主要的原因在于适合于制备BN微纳米材料的先驱体材料极其有限,因此找到合适的BN先驱体是解决上述问题的关键。氨硼烷（BH₃NH₃）是一种只含有B,N和H元素的固体物质,虽然早在1955年即被首次合成,人们对这种物质的高温分解行为以及能否用它来制备BN微纳米材料的认识还非常有限。本文较为系统地研究了氨硼烷的热分解过程,并且以氨硼烷为先驱体,采用化学气相反应法,在气氛压力反应炉中成功制备出了多种BN微纳米材料。证明了氨硼烷是一种优秀的制备BN微纳米材料的先驱体。本文所取得的主要研究成果概括如下。通过第一原理计算研究了氨硼烷的电子结构和成键特征。计算表明,B原子和N原子分别与H原子形成共价键,而B原子和N原子之间由配位键连接;电子从N原子转移到B原子导致了BH₃NH₃单元之间的氢键相互作用和偶极相互作用,BH₃NH₃单元之间的相互作用能为15.1kJ/mol,这是维持氨硼烷结构稳定性的根本原因。TG-DSC-MS分析表明,在1000°C以前,氨硼烷有50%以上的质量损失,损失的这部分氨硼烷转变为硼烷、硼吖嗪以及氨气等多种含有B元素和N元素的气体,而氨硼烷分解所剩余的固体物质为BN纳米晶片,对其进行阴极荧光分析表明,BN纳米晶片的发射谱带处于200-400nm的紫外区,可作为紫外发光材料使用。以氨硼烷作为BN先驱体成功制备了BN纳米管。详细地表征了纳米管的结构、磁学性能以及光学性能;系统地研究了催化剂、反应温度、气压等工艺条件对氮化硼纳米管生长的影响;阐述了纳米管的生长机制。BN纳米管的形貌分为两种,一种为竹节状,另一种为圆柱状。铁粉、氧化铁、四氧化三铁和二茂铁等含铁物质在适当的工艺条件下都可以作为BN纳米管的催化剂,二茂铁的催化效果最佳;在适当的工艺条件下,BN纳米管转变为BN晶须。根据热力学理论并结合VLS生长机制,建立了BN纳米管及BN晶须的生长模型,从理论上对BN纳米管的形貌随工艺条件的变化规律给予了合理的解释。理论分析表明,催化剂粒子太小或太大均不利于BN层片的析出。对BN纳米管磁学性能的研究表明,氮化硼纳米管对其包覆的磁性纳米粒子能起到有效的保护作用。光致发光光谱和阴极荧光光谱的研究表明,BN纳米管以及BN晶须均为发光性能优异的紫外发光材料。以氨硼烷为原料,在石墨纸衬底上制备了碗状和鸟巢状BN微米空心球。对BN微米空心球的结构进行了详细表征,研究了反应温度、气压、气氛等工艺参数对BN微米空心球的结构的影响,提出了生长模型,研究了BN微米空心球的阴极荧光性能。结果表明,BN微米空心球的平均直径为3.4μm,壁厚约为200nm,随着温度的升高,碗状BN微米空心球逐渐转变为鸟巢状。气压对BN微米空心球的影响不显著。碗状BN微米空心球表现出特别的拉曼散射性质,本文在共振拉曼的理论框架下给予了解释。BN微米空心球的阴极荧光发射谱带在200-400nm的紫外区域,表明它们可作为紫外发光器件的候选材料。以氨硼烷和SiC/SiO₂纳米电缆为原料,制备了SiC/SiO₂/BN纳米电缆。对纳米电缆的结构进行了详细表征,探讨了其光致发光性能,研究了反应气氛浓度对SiC/SiO₂/BN纳米电缆结构的影响,阐述了纳米电缆的生长机制。研究结果表明,纳米电缆的直径约为100nm,SiO₂和BN层的厚度分别为10nm和5nm。SiC/SiO₂/BN纳米电缆的光致发光谱与原始SiC/SiO₂纳米电缆的基本相同,但488.5nm处的发射峰发生了一定程度的蓝移。当通过提高氨硼烷用量来提高反应气氛浓度时,原始的SiC/SiO₂纳米电缆转变为BN纳米管,这表明在高温条件下,SiC和SiO₂能被氢气所分解。以氨硼烷和Sialon纳米带为原料,制备了多晶BN纳米带,对其结构进行了详细表征,并讨论了其生长机制。更多还原

【Abstract】 As analogues of carbon micro/nanomaterials, BN micro/nanomaterials have low density, high-temperature stablity, oxidation resistance, good biocompatibility and a series of other advantages, which promises broad applications as UV laser devices, biosensors, composite materials, reinforcements and hydrogen storage materials. But compared with the carbon counterparts, the preparation of BN micro/nanomaterials are facing many difficulties such as demanding reaction conditions, low product yield, and poor purity. The main reason is that BN precursors which are suitable for the preparation of BN micro/nanomaterials is extremely limited, so finding the right BN precursor is the key to solving these problems. Ammonia borane （AB, BH₃NH₃） is a solid-state material and only contains B, N and H elements. Although it has been first synthesized in 1955, knowledge concerning the pyrolysis behavior of this substance and whether they can be used to prepare BN micro/nanomaterials are very limited. The thermal decomposition of AB, and preparation of BN micro/nanomaterials from AB have been systematically studied. It is proved that AB is an promising precursor for BN micro/nanomaterials. The main results obtained in this paper are summarized below.First-principles calculations show that B atoms and N atoms form covalent bonds with H atoms, while the B atoms and N atoms are connected by coordination bonds; The transfer of electrons from the N atom to B atom is confirmed, which led to the hydrogen bond interactions and dipole-dipole interactions among BH₃NH₃ units, The interaction energy was calculated to be 15.1kJ/mol, which is important for the structural stability of AB. TG-DSC-MS analysis show that prior to 1000°C, AB almost loss 50% of the initial mass, the lost part are converted to boranes, borazine, ammonia and other N and/or B containing small molecules, The remaining part was transformed to BN nanoplates, the fluorescent analysis showed that the emission bands of the BN nanoplates is in the 200-400nm region.Using AB as a precursor, BN nanotubes （BNNTs） have been successfully fabricated. The structure, magnetic property and optical properties of the BNNTs, and the effect of the catalyst, reaction temperature, pressure and other processing conditions on the growth of the BNNTs were investigated. The morphologies of the BNNTs can be divided into two kinds, one is the bamboo shaped, the other is cylindrical shaped. Studies on the growth process shows that iron, iron oxide, and ferrocene can be used as a catalyst for the fabrication of BNNTs under appropriate conditions. The catalytic effect of ferrocene is the best. Under appropriate conditions, BNNTs can be transformed into BN whiskers.According to thermodynamic theory and the VLS growth mechanism, the growth model for both BNNTs and whiskers is established. The morphology variations of the BNNTs along with the process conditions could be reasonably explained. Theoretical analysis shows that whether the catalyst particles are too small or too large is not conducive to the precipitation of BN layers. The magnetic properties of the BNNTs which encapsulate magnetic nanoparticles are investigated. It is shown that boron nitride nanotubes can effectively protect the metal nanoparticles in them. PL and CL spectra show that the BNNTs and BN whiskers are ultraviolet light emitting materials with excellent performance.Using AB and graphite paper, we prepared bowl-shaped and nest-shaped BN hollow microspheres. The structure, and the effects of the reaction temperature, pressure, atmosphere and other parameters on the growth of the BN microspheres are investigated. The growth mechanism of the BN microspheres was revealed. the average diameter of the BN hollow spheres is 3.4μm, and the thicknesses were about 200nm. Upon increasing the reaction temperature, the bowl-shaped BN hollow spheres gradually changes into nest-shaped BN microspheres. The effect of pressure on the growth of BN hollow microspheres was not significant. The bowl-shaped BN hollow microspheres show special resonance Raman spectroscopy. The CL emission bands of the BN hollow microspheres are in the region of 200-400nm, indicating that they are promising candidate for UV light-emitting devices.AB can be employed to form BN coatings via CVD method by which SiC/SiO₂/BN three-layered nanocables were prepared from SiC/SiO₂ two-layered nanocables. SiC/SiO₂/BN three-layered nanocables The structure, photoluminescence properties and the effects of vapour concentration on structure of SiC/SiO₂/BN nanocables are investigated. A growth model was proposed. The nanocables are about 100nm in diameter, the thicknesses of the SiO₂ and BN layers were 10nm and 5nm, respectively. The photoluminescence spectra of the original SiC/SiO₂ nanocables and that of the SiC/SiO₂/BN nanocables are basically the same, with only the 488.5nm emission peak blue shifting. Upon increase the concentration of reaction vapours, the original SiC/SiO₂ nanocables are transformed into nanotubes due to the etching of SiC and SiO₂ by hydrogen.更多还原