【作者】 谭翠丽；

【导师】 于杰；

【作者基本信息】 哈尔滨工业大学 ， 材料科学与工程， 2008， 硕士

【摘要】 氧化镍(NiO)、二氧化钛(TiO2)和氧化锌(ZnO)是三种非常重要的金属氧化物。它们在化学、催化、传感器和电池等领域具有广泛的应用前景,因而成为人们研究的热点。目前,虽然人们已经采用多种方法制备出了这三种氧化物的微纳米材料,但是随着这些材料应用的推广和发展,要求其制备工艺得以简化,并降低制备成本。静电纺丝技术是制备纳米纤维的一种简单而高效的方法。迄今为止,已有100多种聚合物被纺成纳米纤维。随着静电纺丝技术的发展,近年来,有一些学者采用电纺纤维作为模板制备具有其它微纳米结构的金属氧化物材料,如纳米管、纳米颗粒等。电纺丝模板法是制备金属氧化物微纳米材料的工艺简单且成本低廉的方法,因此引起许多学者的关注。然而,至今没有看到有关电纺丝模板法制备金属氧化物微纳米材料的较为系统的研究工作。本研究很好地弥补了这一缺陷。本文较为系统而深入地研究了电纺纤维模板法制备的氧化镍、二氧化钛和氧化锌微纳米产品的形貌和工艺参数的密切依赖关系。在此基础上,制备出了三种具有特殊纳米结构的金属氧化物材料,即具有纳米沟槽的蜂窝、微纳米管、多孔微纳米纤维;并对其制备工艺进行了相应的优化,进而对其制备机理进行了必要的分析和探索。本研究采用扫描电子显微镜(SEM)和透射电镜(TEM)对各种产品的表面形貌和微观结构进行了较为细致的表征测试。此外,通过X射线衍射仪(XRD)、场发射扫描电镜能谱仪(EDX)和激光拉曼光谱仪(Raman)等对样品的物相结构和组成进行了表征。通过上述研究,本论文取得的主要成果如下:(1)本文制备得到了具有蜂窝结构的NiO和TiO2材料。这种蜂窝状材料中的蜂窝孔的大小为0.6~4μm。更有意思的是,在这种蜂窝结构之中存在大量的半圆形沟槽,其平均直径约为200nm。研究表明,蜂窝孔来源于乱层堆积的聚丙烯腈(PAN)模板纤维之间的空隙,而纳米沟槽则是由PAN纤维被完全脱除后留下的空穴产生的。研究还表明,NiO蜂窝是在烧结过程中形成的,而TiO2蜂窝是在烧结前形成的。(2)采用电纺PAN纤维模板,通过控制浸渍包覆工艺以及选择合适的焙烧工艺制备出了直径分别为200~380nm、180~250nm和1μm左右的NiO亚微米管、TiO2纳米管和ZnO微米管。研究发现,在浸渍包覆工艺中,沉淀剂的选择非常重要,在很大程度上决定了微纳米管的结构和表面形貌。研究表明,氨水是良好的沉淀剂。本研究首次制得了具有蜂窝孔状表面结构的NiO亚微米管,这种管状结构的形成明显依赖于沉淀过程。此外,焙烧过程中所用的升温速率是影响管状结构形成的一个重要工艺参数。一般来说,采用较小的升温速率对金属氧化物微纳米管的形成是有利的。(3)本研究还制备了具有多孔结构的NiO和ZnO微纳米纤维。其中,NiO纳米纤维的直径为130~210nm,其表面还存在直径约为30nm左右的孔洞;ZnO亚微米纤维的直径为400~750nm,其表面存在直径为50~100nm的孔洞。微纳米纤维结构的形成主要归因于在焙烧过程中,包覆于PAN模板纤维表面的无机氧化物壳层结构在快速升温过程,不能承受住压力的冲击而坍塌导致。本论文认为,降低浸渍溶质的浓度和提高升温速率,均有利于纤维结构的生成。纤维中的孔结构的生成则是PAN纤维在热处理过程中由于分解或氧化反应释放出气体分子造成的。更多还原

【Abstract】 Nickel oxide (NiO), titanium dioxide (TiO2) and zinc oxide (ZnO) are very common and important metal oxide materials. They are widely used in areas of chemistry, catalysis, battery cathodes, sensor, and optical materials et al. Different nanostructures of these three kinds of metal oxides have been preparated by many methods. Although great progress has been made, it is still urgent to fabricate metal oxides with special nanostructures in a sample and low-cost method for meeting various application requirements. Electrospinning technique is a simple and versatile method to prepare nanofibers. Up to now, about 100 polymers have been made into nanofibers by electrospinning technique. Some people had used electrospun fibers as templates to prepare micro- and nanomatrials with different structures in recent years, and this method has becoming a simple and low-cost method to prepare metal oxides micro- and nanomaterials. But there was no systematic study on preparing micro- and nanomaterials from electrospun fibers templates. The present work aims at establishing the systematic process and explores novel structural materials based on the electrospun fibrous templates. The main conclusions can be obtained as following:(1) NiO and TiO2 honeycomb-like materials with nanogrooves were successfully prepared. For these two materials, the diameters of the honeycomb holes changing from 0.6μm to 4μm. Apart from the honeycomb holes there also exist nanogrooves in the hole walls with the groove diameter about 200 nm. The honeycomb pores for NiO materials originates from the interspaces between the randomly stacked polyacrylonitrile (PAN) nanofibers and the nanogrooves were formed due to the presence of the PAN nanofiber templates. The honeycomb-like structure was formed during calcination process for NiO but before calcination for TiO2.(2) Nanoplatelets constructed porous NiO submicrotubes with the outer diameters of 200~380 nm, TiO2 nanotubes with the outer diameters of 180~250nm, and ZnO microntubes with the outer diameters of 1μm have been successfully produced by using electrospun PAN fibers as templates. During preparation ammonia was used as the precipitator, which plays key roles in the formation of the tubular structures. The nanoplatelets constructed porous NiO submicrotubes were prepared for the fist time. Heating rate is also important for prearing the tubular structure and low heating rates were generally required.(3) Porous NiO nanofibers with diameters of 130~210nm and ZnO submicronfibers with diameters of 400~750nm were synthesized. Formation of the submicro- and nanofibers is due to shrinkage and collapse of the shell layers coated on the surface of the PAN template fibers under high heating rates. The submicro- and nanofiber structure tends to form at low concentration of nickel or zinc nitrate solution and high heating rate. Releasing of gases originating from the core PAN fibers results in the formation of a large number of pores in the residual materials.更多还原