【作者】 顾福博；

【导师】 郭广生；

【作者基本信息】 北京化工大学 ， 应用化学， 2008， 博士

【摘要】 随着高科技的发展与实际应用的需要,具有特殊结构和功能的纳米材料的设计、制备以及相关技术路线和规律的研究日益显示其重要性。近年来,人们采用不同的合成路线成功的制备了具有各种形貌的纳米材料,不断完善了纳米材料的结构、物性分析检测手段,并对纳米材料的生长机制做了初步的解释,为纳米材料的可控制备及应用研究奠定了一定的理论和技术基础。与此同时,人们也对纳米材料的控制合成、生成理论的探索提出了更高的要求。本论文主要以上述需求为出发点,选取乳液体系中纳米材料的制备为研究对象,通过稀土无机盐等新型纳米材料及纳米结构的控制合成来探讨乳液体系中材料的基本生成规律,具体研究内容如下:1、利用常温微乳液法,仿照生物矿化过程,运用化学的基本理论、方法分析生物矿化过程中的科学问题,深化人们对生物体内矿化过程的认识。通过系列稀土碳酸盐及磷酸盐纳米材料的制备,系统的研究稀土碳酸盐及磷酸盐纳米材料及纳米结构的成核、生长及组装过程,并对其形貌演变规律进行探讨。分析由不同稀土离子与表面活性剂分子的相互作用而引起的表面活性剂构相的改变对产物结构的影响;研究反应过程中的界面效应,结合现有晶体理论,探索乳液体系中纳米材料的基本生成规律。研究发现:由于不同稀土离子和表面活性剂分子作用效果的差异,导致了稀土碳酸盐纳米材料形貌的演变:从纳米线、纳米带转变为“Z”字形结构,进而变成双扇形,最后形成介晶结构以及凝胶产物;而较强的界面作用导致了稀土磷酸盐纳米材料形貌的单一性,即均为超细纤维状结构。另外,溶液的过饱和度等因素也会对产物的晶化过程产生重要影响。2、利用常温乳液法反应条件温和、可控参数多的优点,制备具有不同结构的新型稀土功能纳米材料。稀土掺杂磷酸镧荧光纳米纤维的研究结果表明:常温乳液法制备的纳米纤维直径较小（约为5nm）,并具有较窄的尺寸分布。由于铕离子的掺杂导致了纳米纤维的晶格缺陷,从而引起了纳米纤维荧光性质与块体材料的不同;而铈、铽离子掺杂的纳米纤维具有较高的量子产率。此外,我们还通过对乳液法制备的碳酸铈产物的功能化,制备了具有不同形貌的介孔氧化铈纳米材料。研究结果表明:该材料具有较大的比表面积和孔容。另外,由于组成不同形貌氧化铈纳米材料的晶粒尺寸不同,导致了紫外光谱中吸收带的蓝移。采用不同的分析技术对材料介孔结构的形成过程进行了研究,结果表明:可能是由于具有与生物矿化产物相似的组成及结构特征,前驱物中有机成分的存在导致了介孔结构的形成。同时,我们还制备出具有较好分散性LaCoO₃纳米粒子,探讨了实验参数对纳米粒子组成及结构的影响,进而对LaCoO₃纳米粒子的光催化活性进行了研究。3、在实现常温乳液体系中各种纳米材料可控制备及对其生成规律的认识相对完善的基础之上,将微乳液法和水热法有机结合,利用微乳液法可调工艺参数多,产物尺寸、形貌均匀可控等优点和水热条件下溶质传输更为有效、反应速度快的特点,制备具有不同结构和功能的新型纳米材料和纳米结构。研究两种方法产生的协同效应,探讨高温乳液法制备纳米材料的生成规律。在高温乳液体系中,通过原位组装过程制备了氧化亚铜纳米片阵列和氧化铈纳米薄膜,并对其生成机理进行了研究。合成出具有椭球形结构的碳酸氧铈纳米材料,并将其作为载体,研究了其在柴油氧化脱硫中的催化性能,得到了较好的效果。通过改变表面活性剂的种类,制备了具有团簇形貌的氧化铈纳米结构,电镜分析结果表明特殊的团簇结构导致其Raman光谱散射峰的变化。此外,我们还利用高温乳液法制备了系列具有不同组成的中空结构材料。实验结果表明:该法是一种有效的合成纳米中空球壳材料的新方法。更多还原

【Abstract】 With the development of high-tech and the requirement of practical application,the design and preparation of functional nanomaterials with novel structures and the invention of diverse synthesis methods are becoming more and more important.Recently,various synthesis routes have been extensively used to prepare different nanomaterials,and the corresponding characterization technologies for structure and property have been improved.Moreover,the growth mechanism of nanomaterials has been proposed preliminarily.To some extent,the theoretic and technical bases have been found to the practical application.At the same time,the more controllable method and the detailed explanation of growth mechanism are needed urgently.Regarding the requirements mentioned above,the synthesis of novel nanomaterials was investigated,and the fundamental growth mechanism was explored through the controllable synthesis of different nanomaterials and nanostructures in emulsion system. The main works of this paper were as followed: 1、Microemulsion method,a biomimetic mineralization route,was used to investigate the scientific issues from biomineralization process,so these issues could be solved by the basic theories and the analytic technologies in chemistry.As a result,the biomineralization mechanism could be understood more clearly.A series of rare earth carbonate and phosphate nanostructures were synthesized and the influences of experimental conditions on the growth of the products were investigated.Combined with the classical crystal theory and the interface effect between crystal and surfactant,the growth mechanism of nanomaterials in microemulsion system was proposed.With the increase in the atomic number and the decrease in the ionic radii of rare earth elements,the morphologies of the corresponding carbonates changed from simple one-dimensional structures to complex fan-like superstructures,and then to ellipse-like mesocrystals. The morphology evolvement indicated a change of the interactions between rare earth ion and the template molecule as well as possible conformational effects on the long chain template molecules.The intensive interaction of the interface between crystal and surfactant led to the similar morphologies of rear earth phosphates.In addition,the crystallization process could also be influenced by the degree of supersaturation.2、Taking advantage of the merits of microemulsion method（including mild reaction conditions and more control parameters）,different nanostructured materials of rare earth compounds were synthesized.The lanthanide-doped nanofibers had a mean diameter of 5 nm and a narrow size distribution.The dopant of europium resulted in the distortion of the crystal lattice,which led the fluorescence properties of the ultrafine LaPO₄:Eu nanofibers were different from that of the large diameter ones. The quantum yield of terbium-doped nanofibers was relative high.In addition,different mesoporous ceria nanostructures were successfully synthesized by the microemulsion method.The experiment measurements showed that both the SBET and the Vp of the ceria nanobelts were higher than those of the nanowires.Because of the size effect,the blue-shifting of the absorption band was observed in UV-Vis spectra.The formation mechanism of cefia mesoporous structure was also proposed.Maybe,the precursors had the similar composition and structure characters with the biomineralization products.The organic surfactant molecule,existing in the precursor,resulted in the formation of mesoporous structure.In addition, LaCoO₃ nanoparticles were synthesized and the relationship between experimental condition and structure was studied.Using sunlight as irradiator,the photocatalytic activity of LaCoO₃ was investigated.3、Based on the controllable synthesis of different nanomaterials and the relative perfect crystallization mechanism of the usual emulsion method, high temperature emulsion system was used for the preparation of novel nanomaterials and nanostructures.Maybe,the high temperature emulsion system has the merits both from usual emulsion and hydrothermal method, including more control parameters,narrow size distribution of the products, quick crystallization rate and so on.Moreover,the synergy effect of the two methods maybe appears.Cu₂O nanoplate array and CeO₂ nanofilm were in-situ synthesized and the formation mechanism was investigated in the high temperature emulsion system.Under the similar condition, ellipsoid-like CEO（CO₃）₂ nanomaterials were prepared.Using CEO（CO₃）₂ as support,a quite good catalysis was realized in the desulfur of diesel. Through the change of different surfactants,nanoclusters of CeO₂ were prepared,and the relationship between the Raman scatter property and the special structure was investigated.In addition,a new general method was invented for the preparation of hollow microsphere,and a series of different microspheres were synthesized.更多还原