【作者】 李芸玲；

【导师】 赵敬哲； 王子忱；

【作者基本信息】 吉林大学 ， 物理化学， 2010， 博士

【摘要】 首先,在小分子多元醇(丙三醇、乙二醇等)协同下,在室温水相开放体系中以绿色还原剂水合肼合成出2-5?m Co微球,探讨了多元醇中羟基对球形结构形成的作用机理;采用相似的路径,在低温水相的开放体系中,以NaH2PO2作为还原剂快速合成出了大小在600nm左右、尺寸均一、由纳米片组装而成的球形Co纳米结构,改变了此类还原过程必须引入络合剂的状况,为Co纳米结构合成提供了新的方法。通过对实验条件的考察,择优出反应的最佳条件,提出反应的可能进程,并研究了样品的磁学性能。其次,在室温水相开放体系中合成了分支结构的Co微粉。研究了多元醇聚合物分子对产物形貌与结构的影响,发现对于PEG分子链长的调变可实现对产物形貌的有效控制。通过研究反应机理,我们认为这种变化是Co的磁性及PEG分子的结构导向共同作用的结果。在水合肼还原制备Co纳米粒子的过程中,适量络合剂柠檬酸的加入是确保还原反应进行完全的关键。在研究中,我们创新性地发现极少量Cu离子的参与能够大幅度提高还原反应的速率,省去柠檬酸的加入,运用此种方法,我们在低温水相中合成了100nm的六方金属Co纳米片,初步研究了Cu催化的可能机理。最后,我们对Co3O4纳米粉体的水相开放体系制备和性能进行了研究。采用简单的液相沉淀法合成了在水相和醇相能够稳定分散数月的Co3O4纳米方。此结构的纳米Co3O4经电化学研究发现,其参与构成电极材料显著降低了吸氧电位、提高了电催化活性。同时,我们利用不同种类的沉淀剂在相似的温和环境下合成出了不同形貌的Co3O4纳米粉体:如球形、片状及棒状结构等,并对系列产品进行了光学性能研究。更多还原

【Abstract】 Metallic Co and its oxide Co3O4 are important magnetic materials, which have broad application prospects. The development on their simple and mild preparation and morphology-controlled strategy are important topics, which are worthy of study for theoretical research and application. In this paper, metal Co and its oxide nanomaterials were prepared via a green synthesis method in an open system and these nanomaterials possess a series of characteristic parameters and would have many potential applications. We also did in-depth mechanism study of each reaction system. The main research results and innovations of the thesis are given in the following parts.First, Co microspheres of 2-5?m have been synthesized in aqueous-phase at room temperature with hydrazine hydrate as green reductive agent together with small molecule polyol (glycerin or glycol). The mechanism for the formation of microspheres was discussed. Through other synthesis route, uniformed Co microspheres of 600nm assembled by nanoplatelets were also synthesized by employing NaH2PO2 as reducing agent in a low-temperature aqueous system. We proposed the possible reaction process.Secondly, branched Co powders have been synthesized in aqueous at room temperature. We studied the effects of surfactant on the morphology and structure of samples and found that chain length of PEG as surfactant drastically influenced the morphologies of the produced cobalt crystals. Based on the investigation of reaction mechanism, we believe that the reasons for these variations may be caused by the interaction between magnetic properties of Co and direction of PEG. Appropriate citric acid was the key factor to complete the reduction of Co in which hydrazine hydrate was employed as reductive agent to prepare metal Co. In the course of the study, we innovatively found that participation of a small amount of Cu in the reaction system can not only substitute for citric acid to make reaction perform completely but also speed up the reaction. We have synthesized hexagonal Co nanoplates of 100nm in aqueous with help of Cu ions. The possible mechanism on Cu as catalyst was studied preliminarily.Finally, the preparation of Co3O4 powders in aqueous-phase and property evolution has been studied. Co3O4 nanocubes have been synthesized by aqueous precipitation method at low temperature, which can be stable suspension in aqueous or ethanol medium for several months. The as-prepared Co3O4 nanocubes extend improved electrocatalytic activities and decreased oxygen evolution potential in electrochemical reactions. Meanwhile, Co3O4 samples with different morphologies have been synthesized with different types of precipitator under a similar mild condition.In conclusion,different size of Co and Co3O4 nanomaterials with several dimensions are obtained by aqueous synthesis method. Our work gives an improved progress on the mild solution synthesis of Co nanomaterials.The synthesized methods used here are simple and the obtained Co and Co3O4 nanomaterials can be potential applied in magnetic devices, electrochemistry and catalysis.更多还原