纳米铁氧体及其复合材料的制备和性能研究

发布时间：2018-09-10 13:02

【摘要】：纳米技术作为当代社会的一种前沿技术已经受到了越来越多人的关注,得到了飞速发展。随着纳米技术的发展,越来越多的纳米材料涌现出来。尖晶石铁氧体因其具有独特的电、磁特性,粒径特征,使材料表现出了优异的性能,受到了广大学者的关注。尖晶石铁氧体纳米材料结合了铁氧体的电磁特性和纳米材料的独特优势,导致了更加优化的性能。材料的化学组成,形貌以及粒径的大小均对尖晶石铁氧体的物理和化学性能有很大的影响。因此,纳米铁氧体及其复合物的设计合成,针对其微观结构与性能之间关系的深入探讨,具有重要意义。本文主要采用溶剂热法对ZnFe_2O_4和NiFe_2O_4两种铁氧体进行了合成,并分别研究了其在电化学和微波吸收领域的应用。主要研究内容如下:1.多孔ZnFe_2O_4纳米球的制备及其作为锂离子电池负极材料的电化学性能研究。我们采用溶剂热法辅助热处理的方法成功的合成了粒径为200 nm左右的多孔ZnFe_2O_4纳米球。并用X射线衍射仪和X光电子能谱(XPS)对其化学组成进行了分析,通过扫描电镜(SEM)和透射电镜(TEM)确定了材料形貌和微观结构等特征,用N2吸附证明了其介孔特征以及比表面积和孔径等信息。通过此方法合成得到的多孔ZnFe_2O_4纳米球作为锂离子电池负极材料,展现出了优异的电化学性能。多孔的特征有利于电解液浸润,同时缓解充放电过程中的体积改变,使结构更加稳定,从而增加了循环性能。较小的颗粒尺寸,缩短了锂离子的传输路径,促进了离子传输,从而增加了倍率性能。2.NiFe_2O_4微米棒及其复合物的合成和微波吸收性能研究。我们采用溶剂热及热处理过程制备得到了NiFe_2O_4微米棒,进一步采用原位化学氧化聚合法合成了NiFe_2O_4@PPy复合物。对其组成进行了X射线粉末测试(XRD);用拉曼光谱证明了PPy的存在;微观形貌以及结构进行了扫描电镜测试(SEM)和透射电镜测试(TEM);用振动样品磁强计(VSM)进行了相关的磁性表征。我们对两种材料进行了微波吸收性能测试,结果表明NiFe_2O_4@PPy复合物在涂层厚度为2.5 mm时最大反射损失值达到-28.06 dB,比单一的NiFe_2O_4微米棒的微波吸收性能(涂层厚度为3 mm时最大反射损失值为-7.82 dB)有很大提升。NiFe_2O_4@PPy复合物微波吸收性能的改善主要是因为介电材料PPy的引入增加了介电性能,使材料获得了更优的阻抗匹配,同时复合材料中存在的多重界面以及相关的界面极化和弛豫过程,增加了对电磁波的衰减和损耗。
[Abstract]:As a frontier technology in contemporary society, nanotechnology has been paid more and more attention and developed rapidly. With the development of nanotechnology, more and more nanomaterials emerge. Spinel ferrite has attracted much attention because of its unique electrical, magnetic and particle size characteristics. Spinel ferrite nanomaterials combine the electromagnetic properties of ferrites with the unique advantages of nanomaterials, resulting in better performance. The chemical composition, morphology and size of the spinel ferrite have great influence on the physical and chemical properties of the spinel ferrite. Therefore, it is of great significance to study the relationship between microstructure and properties of nano-ferrite and its complexes. In this paper, ZnFe_2O_4 and NiFe_2O_4 ferrites were synthesized by solvothermal method, and their applications in electrochemical and microwave absorption were studied. The main research contents are as follows: 1. Preparation of porous ZnFe_2O_4 nanospheres and their electrochemical properties as anode materials for lithium ion batteries. The porous ZnFe_2O_4 nanospheres with a diameter of about 200 nm were successfully synthesized by solvothermal assisted heat treatment. The chemical composition was analyzed by X-ray diffractometer and X-ray photoelectron spectroscopy (XPS). The morphology and microstructure of the materials were determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mesoporous characteristics, specific surface area and pore size were proved by N2 adsorption. The porous ZnFe_2O_4 nanospheres synthesized by this method were used as anode materials for lithium ion batteries and showed excellent electrochemical properties. The porous characteristics are favorable to the electrolyte infiltration, and at the same time to ease the volume change during charge and discharge, and make the structure more stable, thus increasing the circulation performance. The smaller particle size shortens the transport path of lithium ion and accelerates the ion transport thus increasing the ratio performance. 2. The synthesis and microwave absorption properties of NiFe2O4 microrods and their complexes. NiFe_2O_4 micron rods were prepared by solvothermal and heat treatment. Furthermore, NiFe_2O_4@PPy complexes were synthesized by in situ chemical oxidation polymerization. The existence of PPy was proved by Raman spectroscopy, the morphology and structure of PPy were characterized by scanning electron microscopy (SEM) (SEM) and transmission electron microscopy (TEM);) by vibrating sample magnetometer (VSM). We tested the microwave absorption properties of two kinds of materials, The results show that when the coating thickness is 2.5 mm, the maximum reflectance loss value of NiFe_2O_4@PPy composite is -28.06 dB, which is much higher than that of a single NiFe_2O_4 micron rod (when the coating thickness is 3 mm, the maximum reflectance loss value is -7.82 dB). The improvement of microwave absorption is mainly due to the introduction of dielectric material PPy to increase the dielectric properties. At the same time, the multiple interfaces in the composites and the related interfacial polarization and relaxation processes increase the attenuation and loss of electromagnetic waves.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33

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