|Alternative Title||Synthesis and properties of Ni and Co3O4 nanoparticles with special structure|
|Place of Conferral||兰州|
|Keyword||特殊结构 磁性金属 溶剂热法 镍单质 四氧化三钴|
磁性金属或其氧化物纳米材料由于其特殊的磁性能和催化等性能而受到广泛关注，其中，具有特殊结构的磁性金属或其氧化物纳米材料由于具有更新奇的性能而被广泛应用于磁学、催化、生物医药分离等领域。本文用晶体成核和长大理论为指导，通过对实验条件的控制，得到具有特殊结构的磁性金属或其氧化物纳米材料，并阐述了产物的结构控制合成机理，比较了相似结构纳米材料的形成机理，不同结构纳米材料磁性的差异以及产物结构对其磁性的影响原理。 本文以溶剂热法为主要制备方法，通过控制试验参数如溶剂、反应物浓度以及反应温度、反应时间等，实现产物结构和尺寸的可控合成。以乙酰丙酮镍为镍源，油胺为溶剂，不添加任何还原剂和表面活性剂，制备出了尺寸约150 nm的飞镖状结构fcc相镍单质，在上述反应条件中添加十六烷基三甲基溴化铵，可以得到球状镍。比较两种不同结构的镍单质的磁性，飞镖状结构fcc镍的矫顽力和饱和磁化强度都高于球状fcc镍；以二甲基甲酰胺和去离子水为溶剂，两种无机镍盐为镍源合成了片状结构fcc相镍单质，发现提高反应温度和增加反应时间对产物结构有很大影响，产物从片状变为多面体结构。不同结构的产物中，片状结构的饱和磁化强度都小于其他结构的饱和磁化强度。以无水乙醇为溶剂，六水合氯化钴为钴源，添加油胺和油酸，在一定反应温度和时间下制备得中空结构前驱体相，再将前驱体煅烧得到最终产物Co3O4。钴源和油胺的量对产物结构有较大影响，产物结构由中空球壳结构变为不规则多面体，这些不同结构的产物中，前驱体为中空结构的产物的饱和磁化强度大于其他多面体结构的产物的值。以三辛基胺为溶剂，乙酰丙酮钴为钴源，添加表面活性剂油酸制备中空结构前驱体，进一步煅烧得Co3O4，随反应物的量的变化产物结构也会发生巨大改变，中空球壳结构产物消失，产物为不规则多面体结构。磁性测试结果表明煅烧产物表面有大量片状结构的产物的矫顽力远大于其他结构的煅烧产物。对具有少量中空结构的产物进行电化学测试，产物的可逆循环容量高于商用石墨烯的值。
Magnetic metal and their oxides nanomaterials are intensively concerned because of their special magnetic properties and catalytic properties and so on, among them, their counterparts with special structures have great potential in magnetics, catalysts, medical bioseparation and etc., because of their more novel properties. In this article, magnetic metal or their oxides nanomaterials with special structures were synthesized via crystal nucleation and growth theory and the control of experimental conditions. Subsequently, the mechanism of structures control of nanomaterials was clearly proposed, and the differences between the formation mechanisms of nanomaterials with similar structures were also illustrated. Furthermore, the magnetic difference among nanomaterials with distinct structures and the influential principal of different structures of nanomaterials to their magnetic properties were also clearly described.
Solvothermal method was used as the main synthesis approach to conduct the controllable synthesis of products with special structures and concern size by adjusting experimental parameters such as solvents, concentration of reactants, reaction temperature and reaction time. Shuriken-like fcc nickel nanoparticles with its size about 150 nm were synthesized successfully, with Ni(acac)2 as the nickel source, oleylamine as the solvent, and in the absence of any reductants and surfactants,
with the addition of hexadecyl trimethyl ammoniμm bromide, sphere-shape fcc nickel nanoparticles can be obtained. Compared two kinds of nickel nanoparticles with different structure, it can be acknowledged that the saturated magnetization and coercivity of shuriken-like fcc nickel is much larger than the sphere-shape fcc nickel. With dimethylformamide and de-ion water as solvent, two kinds of inorganic nickel salt, nickel acetate tetrahydrate and nickel chloride hexahydrate, as the nickel source, plate-like fcc Ni were synthesized. And the structure of products is significantly affected by the increasement of reaction temperature and extension of reaction time, the structure of products turned from plate to polyhedron. Among nickel particles with different structure, the saturated magnetization of plate-like nickel is a little smaller than other nickel products. As to the metal oxides, there are two methods to obtain them. One is that with ethanol as the solvent, cobalt chloride hexahydrate as the cobalt source, and concerned amount of oleylamine and oleic acid, hollow precursor could be synthesized firstly, then final Co3O4 compounds could be obtained via calcination. The amounts of cobalt source and oleylamine have great influence on the morphology of products, structure of the nanomaterials was converted into irregular polyhedron, compared the magnetic properties of different strutrues, finding that the saturated magnetization of cobalt oxide with presusor of hollow structure is larger than others with polyhedron structure. Another method is with tri-n-octylamine as solvent, Co(acac)2 as the cobalt source, and surfactant oleic acid to synthesize hollow precursor, then calcinate the precursor to obtain Co3O4. Besides, the structures of precusor were changed into irregular polyhedron with the change of amounts and ratio of reactants. The measurement of products’ magnetic properties indicated that the coercivity of products with plate-like structures on its surface is much larger than other products. The electrochemical discharge capacity of Co3O4 with little hollow structures is higher than commercial graphite.
|刘升青. 特殊结构Ni及Co3O4纳米材料的制备及性能研究[D]. 兰州. 兰州大学,2018.|
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