【作者】 周玉雪；

【导师】 俞书宏；

【作者基本信息】 中国科学技术大学 ， 材料物理与化学， 2009， 博士

【摘要】 本论文发展了在温和条件下液相化学合成钨酸盐功能性纳米材料的方法并对含有磁性过渡金属离子Mn²⁺、Fe²⁺的钨酸盐化合物的磁学性能进行了分析和研究,发现具有纳微结构尺寸的MnWO₄和FeWO₄新型自组装等级结构具有与块材钨酸盐不同的磁学性质,这将为我们探索和研究钨酸盐磁性材料在磁性纳米器件方面的应用提供了前提。并且,我们还首次发现了FeWO₄等级结构微晶的光催化性能,这将为开发环保、耐酸耐碱的光催化复合材料提供一条有效的途径。此外,我们还对含有过渡金属Co离子的Co₉S₈化合物的磁学性能、用作锂电池负极材料的充放电性能、在氧气电还原反应中作为催化剂的电催化性能进行了分析和研究。主要结果归纳如下:1、在温和水热条件下,我们利用阳离子表面活性剂十六烷基三甲基溴化铵（CTAB）为添加剂辅助制备了由MnWO₄纳米棒有序自组装而成的新颖海胆状等级结构的MnWO₄微球。通过对不同反应时间产物的形貌分析,发现CTAB在诱导海胆状MnWO₄微球的生长和自组装上起到了一个“软模板”的作用,同时合适的溶液pH值和反应温度也是海胆状微球结构形成所必不可少的条件。海胆状MnWO₄微球的磁学性能测试表明它们在低温下具有较弱的铁磁性排列,而较短MnWO₄纳米棒在低温下表现出反铁磁性。2、通过简单的溶剂热合成路线成功制备出具有高度等级结构的六方片状FeWO₄微晶结构,研究发现乙二醇在这种特殊结构的形成和自组装过程起到了重要的“包覆剂”作用,并且足量的NaAc也是FeWO₄等级结构形成的必要条件。首次对这种FeWO₄等级结构微晶的光催化性能进行了研究,发现FeWO₄微晶结构在紫外和可见光（模拟太阳光）光照条件下对降解罗丹明染料有着较高的光催化活性。此外,我们还对FeWO₄微晶的磁学性质进行了测试,磁性测试结果表明FeWO₄六方片状微晶在低温条件下存在弱铁磁有序,这将为探索和研究具有磁学和光催化复合性能的FeWO₄纳米材料提供一条有效的途径。3.通过简单的溶剂热合成路线我们成功制备出具有高度等级结构的Co₉S₈空心微球结构,不同反应时间阶段产物的形貌分析表明Co₉S₈空心微球结构的形成过程遵循奥斯特-瓦尔德熟化机理,并且合适的三乙烯四胺有机溶剂和水的体积比值也是空心微球结构形成的必要条件。我们首次对于Co₉S₈等级结构空心微球作为锂电池负极材料的充放电性能以及在氧气电还原反应中作为催化剂的电催化性能进行了研究,发现Co₉S₈空心微球结构作为锂电池负极材料时在充放电循环初期具有较高的放电容量,并且Co₉S₈的旋转圆盘电极（RDE）测试表明它的可逆电势与理论模拟计算值较为接近,验证了Co₉S₈可逆电势值与理论计算值的一致性。此外,我们还对Co₉S₈空心微球结构的磁学性能进行了研究,研究表明样品磁学特性主要是顺磁特性的,并且还存在反铁磁特性。更多还原

【Abstract】 In this dissertation,soft solution-based routes were developed to synthesize functional metal tungstate nanomaterials which contain magnetic ions such as Mn²⁺ and Fe²⁺ and their magnetic properties were studied.It was found that the magnetic properties of such hierarchically assembled MnWO₄ and FeWO₄ architectures were different from their corresponding bulk materials,which may give us the chance to realize the application of such sample on magnetic nano device.The photocatalytic property of hierarchically assembled FeWO₄ microcrystals have been firstly studied, therefore it is an effective method to develop a novel environment friendly material which is anti-acid and anti-alkali.In addition,the discharge ability of Co₉S₈ hollow microspheres as Li battery cathode materials and their magnetic property as well as their catalytic property in electrocatalysis of Oxygen Reduction Reaction（ORR） were also studied.The main results can be summarized as follows.1.Three dimensional（3D） urchin-like MnWO₄ microspheres assembled by nanorods have been fabricated by a cationic surfactant cetyltrimethyl ammonium bromide（CTAB） assisted hydrothermal method.The results indicated that CTAB played an important role as a soft template in directing growth and self-assembly of urchin-like MnWO₄ microspheres.In addition,suitable pH values and reaction temperature are also essential for the formation of urchin-like microspheres.Magnetic measurement indicates that urchin-like MnWO₄ microspheres show a weak ferromagnetic ordering at low temperature due to spin-canting and surface spins of microspheres,while much shorter MnWO₄ nanorods show antiferromagnetism at low temperature.2.Highly hierarchical plate-like FeWO₄ microcrystals have been synthesized by a simple solvothermal route,where ethylene glycol（EG） plays an important role as a capping agent in directing growth and self-assemble of such unique structures.In addition,a certain amount of NaAc was necessary for the formation of such unique FeWO₄ microstructures.The photocatalytic property of as-synthesized hierarchical FeWO₄ microcrystals has been firstly studied,which shows excellent photocatalytic activity for degradation of rhodamine-B（RhB） under UV and visible light irradiation （modeling sunlight）.Moreover,magnetic measurement indicates that hexangular FeWO₄ plate-like microcrystals show a small ferromagnetic ordering at low temperature due to spin-canting of antiferromagnetic materials and surface spins of FeWO₄ nanoparticles.3.Highly hierarchical hollow Co₉S₈ microspheres have been synthesized by a simple solvothermal route,the morphology characterization of products obtained by different reaction time shows that the formation process of such hollow architecture was according to Ostwald Ripening mechanism,and appropriate volume ratio of triethylenetetramine（TETA） and H₂O is necessary to precipitation of hollow Co₉S₈ microspheres.Firstly,the discharge ability of such sample as Li batteries cathode materials and their catalytic property in electrocatalysis of Oxygen Reduction Reaction（ORR） was studied and analyzed,it was found that the discharge capacity of hollow Co₉S₈ microspheres at the initial discharge stage of Li battery cathode materials is higher than nanosized Co₉S₈ particles,then the RDE measurement shows that the reversible potential of Co₉S₈ hollow microspheres is approaching to the calculated value by theory simulation which validated the accordance between experiment and theory of reversible eversible potential of Co₉S₈ sulfide.In addition, the magnetic properties of Co₉S₈ hollow microspheres were also studied and it shows that the main magnetic properties of sample is paramagnetic and the sample also contains anti-ferromagnetic properties.更多还原