【作者】 杨玉英；

【导师】 胡中爱；

【作者基本信息】 西北师范大学 ， 物理化学， 2005， 硕士

【摘要】 纳米粒子以其独特的光、声、电、磁、热、催化、力学、化学活性等性质及巨大的潜在价值,成为材料科学的热点研究领域之一。LaMnO_3.15是一种典型的钙钛矿氧化物,它在高温条件下仍然具有良好的热稳定性,广泛用作碳水化合物的加氢、一氧化碳和氨的氧化、燃烧等过程的催化剂;ZnO是一种重要的半导体材料,在光电转换、光催化剂、化学传感器和发光材料等领域有广泛的应用前景;Co₃O₄和NiO都是很好的电极材料。本文首次采用接枝羧基淀粉吸附金属粒子获得非晶前驱物,再进行热分解的方法制备获得了LaMnO_3.15、ZnO、Co₃O₄、NiO等氧化物纳米颗粒,并通过IR、DTA-TG、XRD、TEM等多种实验手段对产品进行了表征。 本论文主要有以下四部分组成: 1 接枝羧基淀粉的制备 详细介绍了淀粉接枝共聚的几种方法及反应机理,讨论了接枝共聚的工艺条件对接枝率的影响。以硝酸铈铵为引发剂,丙烯腈为单体获得了接枝羧基淀粉。红外光谱结果表明:在淀粉骨架上引入-CN基团,并经过水解、皂化、酸化最终将-CN水解为-COOH。 2 LaMnO_3.15钙钛矿复合氧化物的制备与催化性能 LaMnO₃是一种典型的钙钛矿氧化物,它在高温条件下仍然具有良好的热稳定性,特别是它存在稳定的不寻常阳离子氧化态结构以及对氧表现出高传输性质,导致其氧含量不符合化合物计量关系。正是由于这种特性,使得LaMnO_3+δ成为氧化反应中广泛应用的催化剂。本文采用一种新方法——接枝羧基淀粉（ISC）前驱物（ISC-M）热解法,制备了LaMnO_3.15纳米颗粒。对ISC和ISC-M的红外光谱（IR）进行了对比和讨论;利用差热、热重（DTA-TG）研究了前驱物的分解过程;通过X射线衍射（XRD）数据分析了LaMnO_3.15纳米颗粒的晶相;借助透射电镜（TEM）观察了粒子的形状和尺寸分布。结果表明:采用该方法获得的纳米LaMnO_3.15粒子晶粒细小、粒度分布均匀、分散性好、无团聚、粒子的平均粒径<20nm;需要强调指出的是,利用该方法合成LaMnO_3.15纳米粒子时,晶相转化温度远远低于传统方法,在600℃时就可以获得较好的晶相结构。对纳米LaMn_3.15复合氧化物在常温下的液固相催化活性进行了初步研究,结果表明,LaMnO_3.15对于肉桂醛氧化制肉桂酸具有良好的催化活性。 3 氧化锌纳米粒子的制备及其光催化活性 氧化锌是具有六方结构的重要功能材料,室温下能带带隙为3.3eV,激子束缚能高更多还原

【Abstract】 Because of its many particular properties in optics 、 electricity、 magnetism、heat、 catalysis 、 mechanics、 chemical activity etc, and its great potential high technology applied prospects, nanoparticle has become one of the quite hot problems in material research fields, it gains much attention of the scientists from all the world. Various methods have been used for the preparation of nanoparticles, however some intriguing questions remain unanswered even now. It is still a challenging research area to prepare novel functional nanostructured materials with interesting and useful properties, so it is even important to explore new methods for synthesis of nanomaterials with controllable size and shape and to understand the mechanism and rule of the growth process of nanomaterials for further application. In this work, we developed an easy, inexpensive method to synthesize a fine and homogeneous metal oxide nanoparticles.This thesis consists of four sections as follows:First, some methods for synthesis of grafted starch were introduced in this paper, and the reaction mechanism was also described. The influence of initiator concentration, monomer concentration, reaction temperature, and reaction time on grafting parameters of starch graft copolymers was discussed. Finally, by using Ce⁴⁺ as initiator we investigated graft emulsion copolymerization of acrylonitrile onto starch. The structure of the grafted starch was investigated with FTIR.Perovskite type complex oxide LaMnCh are promising ceramic materials used as electrode materials in solid-oxide fuel cell or as the catalysts. But they usually possess low specific surface areas, generally<10m² ? g-1, so the potential application of these materials as catalysts are limited. In order to increase the specific surface areas, the best way is to prepare nanometer-scale powders. A new method was used to prepare well-separated and spherical LaMnO3 nanosized particles. The overall process involves three steps: preparation of insoluble carboxyl-containing grafted starch copolymer （ISC）; formation of presursor （ISC-M）; decomposition of ISC-M, and phase transition of LaMnO₃ nano-particles. Infrared spectra for ISC and ISC-M were discussed. The decomposition of the precursor was studied by DTA-TG. The crystalline phase was characterized by XRD. The size distribution and shape of particles were observed by TEM. The average particle size is less than 20 nm. Furthermore, this processcould be carried out at low temperature （about 600 ℃） and further investigation showed that LaMnO3.15 exhibited evidently catalytic activity for oxidation of cinnamaldehyde at moderate temperatures.Zinc oxide （ZnO） is a versatile semiconductor material with hexagonal wurtzite structure and has a band gap of 3.3 eV and a large excition binding energy of 60 meV at room temperature. It has attracted much attention like GaN due to the application of UV emission. In the past, the structure and optical properties of ZnO film has been investigated extensively. In this dissertation, insoluble carboxyl-containing grafted starch copolymer （ISC） was used to prepare ZnO nanoparticles. The crystal type, morphology and particle size, the distribution of particle size and purity of product was characterized by XRD、 FTIR、 DTA-TG、 TEM. The results showed that spherical, well-separated nanoparticles with the narrow distribution could be obtained by this method.Insoluble carboxyl-containing grafted starch copolymer （ISC） was used to prepare NiO、 CO₃O₄ nanoparticles. Their crystal type, morphology and particle size, the distribution of particle size and purity of product was characterized by XRD、 FTIR、 DTA-TG、 TEM.更多还原