【作者】 金英；

【导师】 张军；

【作者基本信息】 内蒙古大学 ， 无机化学， 2009， 硕士

【摘要】 三维有序大孔（3DOM）材料具有独特的结构和功能特性,其孔结构、孔壁材料及孔内化学环境可在一定范围内调变,可作为催化剂、光子晶体、功能载体、吸附材料和电极材料等,在催化、环境、化工和电子工业等领域具有十分广阔的应用前景。3DOM材料已成为近年来材料科学研究的热点之一,对3DOM材料研究目前主要集中在以下几个方面:（1）3DOM材料的新型制备方法的开发;（2）3DOM材料孔结构和孔径的调控;（3）不同材料体系的3DOM结构的构筑;（4）3DOM材料孔结构的表面功能化;（5）3DOM新型应用性能的研究等方面。这些研究均存在一定的难度,尤其是还相对比较缺乏有效、普适性的制备方法,造成3DOM材料的制备可控性较差、孔壁强度低及致密性差,这些缺点一定程度上阻碍了3DOM在其许多领域的进一步应用。本文基于3DOM材料较强的应用背景,立足解决3DOM材料走向实际应用所面临的问题,较为新颖地利用胶体晶体模板法制备了孔径可调变、孔壁致密性好、孔材料强度高、三维周期性优良且催化和光学性能优异的多种新型3DOM材料(Y₂O₃:Eu³⁺、Dy₂O₃、Fe₂O₃、TiO₂、CeO₂等),系统地研究了不同制备方法和反应条件对3DOM材料结构、孔径、有序度等特性的影响。同时,通过在3DOM CeO₂结构上负载纳米级Au催化剂,探索性地制备了负载型3DOM Au/CeO₂催化剂,重点研究了该类负载型3DOM催化剂对甲醛氧化反应的独特催化性能。此外,还尝试利用胶体晶体模板法制备了稀土氧化物3DOM荧光纳米材料,并研究了其光学特性。本文主要研究内容和结果具体如下:1.应用无皂乳液法和分散聚合法,合成了粒径为200-2000 nm的单分散、尺寸均匀的聚苯乙烯微球。采用自然沉降法,垂直沉积法和离心法等将单分散的聚苯乙烯微球组装成胶体晶体,以该胶体晶体为模板制备出部分稀土氧化物和过度金属系列(Y₂O₃:Eu³⁺、Dy₂O₃、Fe₂O₃、TiO₂、CeO₂等)3DOM材料。利用X射线粉末衍射、透射电子显微镜,扫描电子显微镜和红外光谱等手段对3DOM材料的相结构、孔结构、孔壁材料组成、三维周期排列等特性进行了系统研究。研究表明,利用本文制备方法可以获得孔径于80-1500 nm范围内可调、孔结构均匀且致密、孔材料强度较高的3DOM材料,这些材料是较好的功能载体、吸附剂和催化剂。2.采用鼓泡式沉积-沉淀法,以上述制备的3DOM CeO₂材料为载体,制备了系列孔径可调、Au负载量不同的新型3DOM Au/CeO₂纳米催化剂,研究了该3DOM Au/CeO₂纳米催化剂对甲醛氧化反应的催化性能,系统考察了催化剂孔结构及孔径大小、Au负载量、反应温度、预/后处理条件等制备因素对催化活性的影响,重点评价了催化剂的催化效率、稳定性及使用寿命,对催化机理进行了一定的探讨。研究结果表明,3DOMAu/CeO₂纳米催化剂的孔径大小、Au负载量、焙烧处理对催化剂的催化性能影响较大。孔径为80 nm、Au负载量为3 wt%、未经焙烧的3DOM/CeO₂纳米催化剂对甲醛催化氧化反应具有优异的催化性能,测试表明该催化剂在75℃下可使甲醛完全氧化,较文献报道的Au/CeO₂型催化剂使甲醛完全转化的温度低30℃。该3DOM Au/CeO₂纳米催化剂较传统无孔结构催化剂性能优异的原因为纳米金颗粒在孔结构的催化剂表面分布均匀、尺寸较小、分散度高、不易团聚,因而极大地提高了其催化性能;同时,催化剂的有序孔结构导致被催化物质可以与催化剂充分接触,提高了其催化性能。该类新型3DOM Au/CeO₂纳米催化剂对甲醛催化氧化反应的稳定性、催化效率和使用寿命较粉状Au/CeO₂催化剂更高,预计在室内空气净化、工业催化领域具有重要的应用价值。3.采用硝酸稀土和柠檬酸的络合物为前驱物溶液,通过上述提及的胶体晶体模板法制备了3DOM Y₂O₃:Eu³⁺纳米荧光粉材料。通过X射线粉末衍射、扫描电子显微镜、和荧光光谱分析等手段,着重研究了孔结构和热处理温度对3DOM Y₂O₃:Eu³⁺纳米荧光粉材料发光性能的影响。研究结果表明,掺杂剂对氧化钇基质的粒径、形貌无明显的影响,煅烧温度为800℃时,所得3DOM Y₂O₃:Eu³⁺纳米荧光粉材料孔结构、三维有序周期性较好且发光特性优良。更多还原

【Abstract】 Three dimensionally ordered macroporous （3DOM） materials have attracted much research attention in recent years due to their special structural and functional properties. 3DOM materials can be utilized as photonic crystals, catalyst, supports, absorbents and electrodes etc., and show great prospective in applications of catalysis, environment, chemical engineering and electronic industries. Currently, 3DOM materials is becoming a hot research area in materials science, and the researches in this field are mainly focused on: （1） development of synthesis technology; （2） modulation of porous structure and pore size; （3） construction with various materials systems; （4） surface fictionalization; （5） exploration of novel functionality of 3DOM structures. However, all these research aspects are somehow difficult to be achieved. Applications of 3DOM materials in various areas still face challenges such as improving the pore wall compactness and mechanical stability, forming ordered structure in large scale, and finding simple synthesis route to decrease synthesis cost.In the present thesis, novel colloidal crystal template methods were developed to synthesize 3DOM materials with controllable pore sizes, improved pore wall compactness and mechanical stability, and well defined three dimensionally ordered porous periodicity. The effects of preparation methods and reaction conditions on the structure, pore size and porous periodicity of 3DOM structures were systematically studied. Furthermore, 3DOM Au/CeO₂ catalysts were synthesized by loading Au nanoparticles onto the 3DOM CeO₂ structure. The catalytic performance of the as-prepared 3DOM Au/CeO₂ catalysts on formaldehyde oxidation reaction was tested. Finally, the 3DOM rare earth phosphors were synthesized via the colloidal crystal template method, and the fluorescence properties were investigated.The main results of the thesis were summarized as below:1. Monodisperse polystyrene （PS） beads with diameters of 200-2000 nm were prepared by using dispersion polymerization and soap-free-emulsion polymerization technique. PS colloidal crystal template was assembled with the obtained monodisperse PS via natural sedimentation, vertical deposition technique and centrifugation method. By using the PS colloidal crystal as templates, 3DOM Dy₂O₃, Fe₂O₃, Y₂O₃:Eu³⁺and CeO₂ materials were fabricated. Transmission electron microscope （TEM）, scanning electron microscope （SEM） and infrared spectra （IR） were used to characterize the resulting 3DOM materials. The results showed that 3DOM materials with adjustable pore sizes in ranges of 80-1500nm were obtained by using this colloidal crystal template method. The obtained 3DOM materials showed three dimensionally ordered porous periodicity with high density. These materials are believed to be good candidates for catalytic support and catalyst uses.2. The 3DOM CeO₂ materials were used as catalytic supports to prepare a series of novel 3DOM Au/CeO₂ nanocatalysts with adjustable pore sizes and different Au loading amount via a deposition-precipitation by in-situ Au nanoparticles onto the 3DOM CeO₂ catalyst supports. The catalytic performance of the obtained 3DOM Au/CeO₂ nanocatalysts on formaldehyde oxidation reaction were investigated. The effects of the pore structure, size, Au loading amount, reaction temperature and pre- or post-treatment on the catalytic activity of the 3DOM nanocatalysts were systematically evaluated. Furthermore, the catalytic efficiency, stability and lifetime were mainly estimated, and the catalytic mechanism was discussed as well. The results indicated that the pore size, Au loading amount and annealing treatment had significantly influences on the catalytic performance of the nanocrystals on formaldehyde oxidation reaction. The nanocatalysts with 80 nm pore size, Au 3wt% loading amount and dying at 60℃showed the best efficiency on formaldehyde oxidation reaction. The formaldehyde oxidation tests revealed that the 3DOM Au/CeO₂ catalysts exhibit superior catalytic activity with 100% formaldehyde conversion at -75℃, 30℃lower than previously reported powder Au/CeO₂ catalysts. This is mainly due to the uniform macroporous structures leading to good distribution of catalytic species of Au nanoparticles with less aggregation. The novel 3DOM Au/CeO₂ nanocatalysts showing much stable, efficient and long catalytic activity may find applications in in-door air purification and industrial catalysis.3. By using the mixture of nitrates and citric acid as precursors, 3DOM Y₂O₃: Eu³⁺ phosphors were fabricated via the colloidal crystal template method. The obtained 3DOM Y₂O₃: Eu³⁺ phosphors were studied by means of XRD, SEM and fluorescence spectroscopy. The effects of the porous structure and heating treatment on the fluorescent properties were examined.更多还原