多重电磁耗散机制纳米复合材料的原位制备及其电磁性能研究

发布时间：2018-04-14 04:14

本文选题：纳米复合材料 + 原位制备　；参考：《河南大学》2015年硕士论文

【摘要】：吸波材料对电磁波的能量耗散,主要来自于材料的介电损耗和磁损耗以及二者匹配。介电损耗主要是指通过介质的电子极化,离子极化或界面极化效应来吸收、衰减电磁波；磁损耗则主要是通过磁滞损耗、畴壁共振、涡流损耗和后效损耗等磁化机制来实现对电磁波的吸收和衰减。随着吸波材料应用领域的不断拓展,对吸波材料的要求也越来越苛刻。开发吸收频带宽、厚度薄、吸收能力强、质量轻的电磁波吸收材料已经引起世界各国的关注。纳米吸波材料作为一类新型的电磁吸波材料,不仅具有较好的电磁波吸收性能,且兼具质量轻,厚度薄,频带宽等优势,成为目前电磁领域的研究热点。然而,由于纳米材料尺寸小,表面能高,容易团聚,因此,如何很好的实现纳米材料的分散性能是其应用研究需要解决的关键性问题。此外,理想的电磁波吸收材料希望能同时具有高的磁损耗因子(tanδM=μr"/μr')以及高的介电损耗因子(tanδE=εr"/εr')。单一组元的吸波剂,难以满足高效吸波性能的要求,因此,如何同步提高这两组参数对于制备高性能电磁波吸收材料至关重要。本论文工作采用简单的原位复合方法,将具有不同电磁耗散机制的纳米材料进行原位复合,制备得到系列纳米复合吸波材料。希望在有效提高纳米材料的分散性能的同时赋予材料更多的损耗机制及其它的性能可调控性,从而实现对材料的优化设计。利用透射电子显微镜(TEM)、场发射扫描电子显微镜(FESEM)、X射线衍射仪(XRD)、共焦显微拉曼激光光谱仪等仪器对得到的纳米复合材料进行了形貌、结构的表征,探讨了样品组成、形貌、结构及微观缺陷等对其磁性和电磁性能的影响,在此基础上,实现对其性能的调控,得到具有理想综合性能的电磁吸波材料。主要研究内容和结果如下：1.在液相系统中,Ni/ITO纳米复合材料的制备是通过简便的原位还原法以氯化镍作为镍源,水合肼作为还原剂以及用NaOH调节溶液的pH来完成的。在所制备的纳米复合材料中,ITO纳米粒子不仅仅作为隔离介质防止磁性纳米粒子的团聚,而且还赋予掺混纳米复合材料利于电磁波吸收的额外界面极化机制。结果表明,与纯相Ni或ITO纳米颗粒相比,Ni/ITO纳米复合材料表现出明显增强的吸波性能。这是因为非磁性的ITO纳米粒子有助于Ni纳米粒子在所制备的Ni/ITO纳米复合材料中实现均匀分散,从而有利于获得合适的电磁阻抗匹配并促进额外的界面极化机制来增强微波吸收。本研究有望在制备具有可调控组成和电磁性能的先进吸波复合材料方面开辟新的途径。2.在本研究中,潜在的轻质微波吸收体Ni/C纳米复合材料是通过简便的方法在流动的氨气气氛中煅烧硝酸镍-聚丙烯酰胺的混合物而制备。并对所制备Ni/C纳米复合材料的电磁特性与其组成和微观结构之间的联系进行考察。研究结果表明,所制备的Ni/C纳米复合材料具有岛屿状结构并由多孔碳基质和尺寸约为几百纳米的镍纳米颗粒组成且Ni/C纳米复合材料表现出优异的电磁性能。Ni/C纳米复合材料电磁性能对温度具有高度的依赖性,且在600。C时制备得到的Ni/C纳米复合材料具有理想的吸波性能。在较小的吸波厚度2.3-7.0 mm范围内,其RL-20 dB(对电磁波的吸收高达99%)的频段范围可达到13.5 GHz。这归功于复合材料中特殊的介孔结构和理想的电磁阻抗匹配以及Ni纳米颗粒在碳基质中的均匀分散。即,Ni/C纳米复合材料中碳基质的存在利于诱导产生多重介电极化从而提高Ni/C纳米复合材料的电磁损耗性能,而且碳的存在在提高复合材料热稳定性,化学稳定性和介电性能的同时还可以保留金属Ni的本征磁性。3.TiN/C纳米复合材料的制备是以钛酸纳米管(H2Ti2O4(OH)2, NTA)和聚丙烯酰胺(PAM)为原料通过简便的一步法完成的。在本节中,氮化钛-碳(TiN/C)纳米复合材料被作为研究本征磁性和电磁性行为与结构缺陷之间关系的具体实例。结果表明,温度对于纳米复合材料的结构组成和性质具有重要影响。此外,TiN/C纳米复合材料不仅表现出明显的静态磁性而且具有显著的动态磁导率,相关于其在8-12 GHz的磁异常和介电共振。然而在TiN/C纳米复合材料弱的静态磁性和动态磁性之间并无直接联系。这意味着尽管所制备纳米材料的电磁性能和结构缺陷之间有一些内在关系,但是静态和动态磁性的起源并不相同。此项工作在揭示纳米结构中静态和动态磁性的起源与结构缺陷和微波电磁特性之间的内在关系方面迈出了重要的一步,为设计缺陷机制的高效电磁波吸收体打开了新的大门。4.在上述工作基础上,采用简单的原位复合方式,以硝酸镍、钛酸纳米管(NTA)和聚丙烯酰胺(PAM)为原材料,固定NTA和PAM的比例不变,逐渐增加硝酸镍的含量,以三者混合物为前驱体在氨气气氛中900℃高温煅烧,一步实现具有不同吸波机制的氮化钛、镍和碳三元纳米复合材料的制备,得到一系列不同比例的Ni/TiN/C纳米复合材料,并对其进行结构性能研究。结果表明,还原过程中得到的镍纳米粒子可以均匀的分散于复合材料中,与空白TiN/C复合材料相比,当硝酸镍的添加比例合适时,Ni/TiN/C复合材料具有明显增强的介电损耗和磁损耗,从而具有理想的吸波性能。以样品S3为例,其RL值在4.5GHz处高达-28.4dB, RL-10的频宽达到7.4 GHz。这归因于多组分复合材料的多重吸波机制,多重界面极化效应以及介电损耗与磁损耗之间较好的阻抗匹配。此外,碳的引入赋予材料较好的热稳定性和较低的密度,从而赋予其更好的环境适应性,使得该复合材料在磁性,吸波及电磁屏蔽等领域均具有很好的应用前景。总之,本研究采用简单的原位复合方法,成功实现一系列具有多重损耗机制的纳米复合吸波材料的制备。通过将具有不同吸波机制的组分进行原位复合,赋予材料更多的电磁波耗散机制,实现了对材料吸波性能的调控；各组分间良好的分散赋予它们更多与电磁波交互作用的机会,从而使其表现出更加高效的吸波性能：不同组分间很好的相容性及界面效应,赋予材料额外的界面极化机制可以进一步提高材料的电磁波吸收能力。该论文通过研究复合材料的组成、结构、微观缺陷等与其电磁性能之间的关系,不仅得到具有优异综合性能的电磁吸波材料,同时也为研究纳米材料独特的电磁波耗散机制提供了更多的研究思路和一定的理论和实验依据。
[Abstract]:Suction wave energy dissipation materials on the electromagnetic wave, mainly from the material of dielectric loss and magnetic loss and dielectric loss. Two, mainly refers to the electronic polarization medium, ion polarization or interfacial polarization effect absorption, attenuation of electromagnetic wave; magnetic loss is mainly through the hysteresis loss, domain wall resonance. The eddy current loss and residual loss such as magnetization mechanism to realize the electromagnetic wave absorption and attenuation. With the expanding application of absorbing wave material, the absorbing material requirements are increasingly demanding. The development of wide absorption band, thin thickness, light weight and strong ability to absorb electromagnetic wave absorbing material has attracted the attention of the world nano absorbing materials. As a new type of electromagnetic wave absorbing materials, not only has good electromagnetic wave absorption performance, with light weight, thin thickness, wide band advantage, become the hotspot research in electromagnetic field. However, because of the nano materials of small size, high surface energy, easy to agglomerate, therefore, realize the dispersion of nano materials and how good is the key problem in the application of research to solve. In addition, the ideal electromagnetic wave absorbing material to also have high magnetic loss factor (tan delta M= / R "R') and high dielectric loss factor (tan delta epsilon / epsilon R' E= R"). The absorbing agent single component, it is difficult to meet the high absorbing performance requirements, therefore, how to improve the synchronization of two sets of parameters for the preparation of high performance electromagnetic wave absorbing materials is very important. The work on the use in situ composite method simple, nano materials with different electromagnetic dissipation mechanism of in situ composite, prepared a series of nano composite absorbing materials. Hope can effectively improve regulation in the nano material dispersion and giving more material loss mechanism and its performance And in order to achieve optimal design of materials. Using transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X ray diffraction (XRD), laser confocal Raman spectrometer instrument. The morphology of the nanocomposites obtained, structure characterization of the sample composition, morphology, influence the structure and micro defect on the magnetic and electromagnetic properties, on the basis of this, the regulation of its properties, has a good overall performance by electromagnetic wave absorbing materials. The main research contents and results are as follows: 1. in the liquid phase, Ni/ITO nano composite was prepared by in situ reduction method is simple with nickel chloride as nickel source, to complete the hydrazine hydrate as reducing agent and the solution is adjusted by NaOH pH. The as prepared nanocomposites, ITO nanoparticles not only as the isolation medium to prevent the magnetic nanoparticles group Together, but also gives mixing nano composite materials for electromagnetic wave absorption of the additional interface polarization mechanism. The results show that, compared with pure Ni or ITO nanoparticles, Ni/ITO nanocomposites exhibit markedly enhanced the absorbing performance. This is because the ITO nanoparticles can help non magnetic Ni nanoparticles in Ni/ITO nanocomposite the preparation of uniform dispersion, which is helpful for obtaining appropriate electromagnetic impedance matching and promote the interface polarization mechanism of additional enhanced microwave absorption. This study is expected in the preparation of advanced composite materials can control composition and magnetic properties of the new way of.2. in this study, lightweight microwave absorber Ni/C nano composite material is a mixture of calcined potential of nickel nitrate polyacrylamide in flowing ammonia atmosphere through simple method and preparation. And the preparation of Ni/C nano composite Inspect between electromagnetic properties and microstructure and composition of the material. The results of the study show that the prepared Ni/C nanocomposites with island shaped structure and is made of porous carbon matrix and the size is about hundreds of nanometer nickel nanoparticles and Ni/C nanocomposites exhibit electromagnetic performance of.Ni/C nano composite material with excellent is highly dependent on the temperature, and the wave absorbing properties in 600.C Ni/C nanocomposites are ideal. In smaller absorbing 2.3-7.0 thickness in the range of mm, the RL-20 dB (on the absorption of electromagnetic waves as high as 99%) the frequency range can reach 13.5 GHz. it is uniformly dispersed in the electromagnetic the impedance of special mesoporous structure and ideal composite material, and Ni nanoparticles in the carbon matrix. That is, the carbon matrix of Ni/C nano composite materials in existence to induce multiple dielectric In order to improve the polarization of electromagnetic loss properties of Ni/C nano composite material, and the presence of carbon in the composite improved thermal stability, chemical stability and dielectric properties but also can retain the intrinsic magnetic properties of.3.TiN/C metal Ni nano composite material is prepared with titanate nanotubes (H2Ti2O4 (OH) 2, (NTA) and polyacrylamide PAM) by one step to finish as raw material. In this section, titanium nitride (TiN/C) - carbon nano composite material as concrete examples of the intrinsic relationship between magnetic and electromagnetic behavior and structural defects. The results show that the temperature has an important influence on the structure of nano composite material composition and properties. In addition, TiN/C nano composite material not only shows obvious but also has dynamic static magnetic permeability, phase on the 8-12 GHz in the magnetic and dielectric resonance. However, in the TiN/C nano composites with weak Between the static and dynamic magnetic magnetic is not directly linked. This means that although the system has some inherent relationship between electromagnetic properties and structural defects of nano scale materials, but the origin of the static and dynamic properties are not the same. This work is inherent in demonstrating the relation between static and dynamic magnetic nanostructures in origin and structure defects and microwave electromagnetic characteristics has taken an important step, high efficient electromagnetic wave absorber design defect mechanism opens new doors for.4. on the basis of the above work, the in situ composite is simple, with nickel nitrate, titanate nanotubes (NTA) and polyacrylamide (PAM) as raw materials, the same fixed NTA and the ratio of PAM gradually, increase the content of nickel nitrate, with a mixture of the three as the precursor in ammonia atmosphere at the temperature of 900 DEG C high temperature calcining step implementation with different absorbing mechanism of titanium nitride, nickel and carbon three yuan Process for preparing nano composite materials, nano Ni/TiN/C composite materials have a series of different scale, and study the performance of the structure. The results show that the reduction process of nickel nanoparticles can be uniformly dispersed in the composite materials, compared with TiN/C composite, added when the proportion of nickel nitrate when appropriate, Ni/TiN/C composite materials with the electric loss and magnetic loss significantly enhanced dielectric, which has the absorbing properties of the ideal. Taking the sample S3 for example, the RL value at 4.5GHz up to -28.4dB, bandwidth of RL-10 to 7.4 GHz. due to the multiple wave absorbing mechanism of multi-component composite materials, good impedance matching between multiple interface effect and the dielectric loss and magnetic loss. In addition, the thermal stability of materials gives better and lower carbon density, giving it a better adaptability to the environment, so that the composite materials in magnetic absorbing Has a good application prospect and electromagnetic shielding and other fields. In this study, in-situ composite method is simple, the successful implementation of a series of multiple loss mechanism of nano composite absorbing material was prepared. The absorbing mechanism with different components in situ composite, gives the mechanism of electromagnetic wave dissipation materials more and the realization of the absorbing properties of materials for regulation; the components of good dispersion to give them more opportunities and the electromagnetic wave interaction, which shows the absorbing properties of more efficient: compatibility and good interface effect between different components, giving the interfacial polarization mechanism can further improve the electromagnetic additional material wave absorption material. The composition, study of the composite structure, the relationship between the micro defects and their electromagnetic properties, not only by electric magnetic with excellent performance At the same time, the absorbing material provides more research ideas and certain theoretical and experimental basis for the study of the unique electromagnetic wave dissipation mechanism of nanomaterials.

【学位授予单位】：河南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;TB33

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