【作者】 宋海胜；

【导师】 唐成春；

【作者基本信息】 华中师范大学 ， 凝聚态物理， 2007， 硕士

【摘要】 硼酸铝一维纳米材料由于其具有优异的力学性质，高温化学稳定性，低的热胀系数以及与传统增强材料碳化硅相比低廉得多的生产成本，成为物理、化学和材料等领域争相研究的热点材料。为了促进硼酸铝一维纳米材料的进一步应用，完善和开发硼酸铝纳米材料的实验室最优化合成方案，实现对难控制纳米材料的表面改性等是一个非常值得研究的前沿课题。本文根据当前硼酸铝一维纳米材料研究中存在的问题，主要做了以下几个方面的探讨。（1）系统地研究了硼酸铝纳米线的制备流程，通过溶胶——凝胶法制备的前驱体以及添加的铝粉量对产物形貌进行控制，摸索出了制备大尺度高纯硼酸铝纳米线的最优化合成方法。实验结果发现溶胶——凝胶法可以保持产物维度的一致性，而铝粉的添加可以降低产物的直径，增大长径比。我们的最优条件得到的硼酸铝纳米线，直径在20—60纳米，长度在1—2微米。（2）在蔗糖的辅助下，将商业用硝酸铝和硼酸在高温下反应，首次制备出了高长径比（100以上）硼酸铝纳米线阵列。通过对实验过程的细致分析发现蔗糖通过自身的缩聚和分解提供一种聚合物衬底以及粘稠性的模板从而在晶体的合成过程中起着至关重要的作用。根据蔗糖的功用，我们对产物可能的机理进行了合理的解释。补充材料一提供了我们获得本章中最优实验条件的系统实验和实验结果。补充材料二提供的是对蔗糖辅助生长纳米线束方法的延伸，利用此方法我们将其应用于硼酸镁（Mg₂B₂O₅）纳米线束的制备，产物结果显示这种方法对于硼酸镁纳米线束的制备也是可行的。（3）使用硼、氧化硼和微米级的氧化铝在没有任何衬底和模板的作用条件下，首次成功合成出硼酸铝纳米线阵列织构而成的多层纳米线网络。研究发现初始微米级的氧化铝粉末在实验过程中提供一种在位反应器，为纳米线的自取向生长提供一种特殊的生长环境；网状形貌的形成依赖于单质硼的加入；实验最后一步是淬火保持纳米线阵列组成的纳米网的形貌。进一步的实验探讨和验证了产物的形貌依赖因素和形成机理。（4）在实验组的前期工作以及作者在摸索快速大尺度合成BN-Al₁₈B₄O₃₃纳米电缆的合成程序基础上得到线索，首次探索出一个外延生长BN包覆纳米线的简捷方法。以硼酸铝(Al₁₈B₄O₃₃)纳米线网为例通过这个方法成功地用BN直接完全包覆硼酸铝(Al₁₈B₄O₃₃)纳米线网。BN-Al₁₈B₄O₃₃纳米电缆是由硼酸铝纳米线和氧化硼在NH₃气氛下于1200℃反应制得。高温热稳定的硼酸铝(Al₁₈B₄O₃₃)纳米线在实验过程中为外延包覆的氮化硼扮演着模板作用。XPS，HRTEM，XRD细致表征了包覆层的结晶度和厚度。BN包覆层的典型厚度为～5nm。我们也同时给出了BN包覆产物的可能生长机理。此种方法重要意义是不受被包覆材料的属性的苛刻限制（与Al₄B₂O₉等高温非稳释放B₂O₃相比），可以延伸为一种用BN包覆难控制纳米材料的方法，从而达到钝化纳米材料表面实现其表面改性的目的。更多还原

【Abstract】 Aluminum borate one-dimensional nanomaterials attract much attention in Phyiscs、Chemistry、Materials and so on due to their excellent mechanical properties, chemical inertness, high temperature stability, low thermal expansion coefficient, and much lower cost compared to the traditional strengthening materials-SiC nanowires. In order to expand the application fields of the aluminum borate nanomaterials and further enhance the mechanical properties, it is worthy of completing and investigating the optional conditions to fabricate aluminum borate nanowires, carrying out the surface modification of refractory nanomaterials, etc. According to the problems of the present research of aluminum borate one-dimensional nanomaterials, the work that I have mainly done is as following.（1） We have systematically investigated the preparing process of aluminum borate nanowires. In fact, we groped the optional conditions to synthesize large-scale high yield aluminum borate nanowires. According to the synthesis process, we pay much attention to the key effects: the preparaion of precursor from sol-gel method and the additive of aluminum powder. The products show that the precursor can control the dimension and the aluminum powder can decrease the diameter and increase the aspect ratio. Using the optional conditions, the diameter of our products is 20-60 nm and the length is 1-2 um long.（2） Under the assistance of sucrose, we firstly got the high aspect ratio （upper than 100） aluminum borate arrays using the reaction between aluminum nitrate and boric acid at high temperature. We have also detailedly analyzed the experimental process and discovered that the sucrose played a crucial role in the growth of the nanowire bundles by supporting as a polymeric substrate and a type of adhesive template. Due to the function of the sucrose playing in the reaction, we proposed a rational mechanism for our products. The supporting document One supplies the systematical experiments and the experimental results. The supporting document Two supplies the extendable application of our method to the preparation magnesium borate （Mg₂B₂O₅） nanowire bundles. The results also show that our extendability is feasible in the preparation of Mg₂B₂O₅ nanowire bundles.（3） Multilayer nanowire webs of aluminum borate (Al₁₈B₄O₃₃) have been firstly synthesized by a solid-state reaction between boron, boron oxide, and aluminum oxide at high temperature without using any template or substrate. Alumina particles on micron-scale provided an in-situ reaction container, supplying a special environment for the self-oriented growth of the aluminum borate nanowires; the addition of boron should be responsible for the generation of the web morphology; the orientation could be maintained by a quenching treatment at the last step. Further experiments were carried out to investigate the morphological dependence on the reactant compositions. The possible growth mechanism for the nanowebs was also proposed and comfirmed by our systematical experiments.（4） We catch our clues from the pre-work of our group and my grope about quick lagre-scale preparation of BN-Al₁₈B₄O₃₃ nanocables, a facile method was firstly proposed to coat nanowires with BN by an epitaxial growth process. We took aluminum borate (Al₁₈B₄O₃₃) nanowire webs for example, our method had directly and completely coated Al₁₈B₄O₃₃ nanowire webs with BN. The BN-Al₁₈B₄O₃₃ nanocable webs could be obtained by the reaction of Al₁₈B₄O₃₃ nanowire webs, B₂O₃ and ammonia at 1200℃. The high-temperature stable Al₁₈B₄O₃₃ nanowire webs played as a template for the epitaxial coating of BN. The coating was characterized by the means of X-ray photoelectron spectroscopy （XPS）, X-ray diffraction （XRD）, Infrared spectrum （IR） and High-resolution transmission electron microscopy （HRTEM）. The typical thickness of the BN shells is～5 nm. The growth mechanism of the present BN-coated aluminum borate (Al₁₈B₄O₃₃) nanostructures was also proposed. The importance of our method is that it is not limited by the cruel properties of the core nanowires （comparing with the high temperature unstable Al₄B₂O₉）, it has the large potential applications to extend it into a widely used method to uniformly coat refractory nanomaterials by BN, so as to modify the surface of the refractory nanomaterials.更多还原