磁性纳米复合材料的原位制备及其电磁性能研究

发布时间：2018-06-12 11:00

本文选题：纳米材料 + 原位复合　；参考：《河南大学》2015年硕士论文

【摘要】：随着信息工程的迅猛发展,开发吸收频带宽、厚度薄、吸收能力强、质量轻的电磁吸收材料已经引起世界各国的关注。纳米材料,特别是磁性纳米金属材料,由于具有独特的光、电、磁等物理学性能,成为材料领域的研究重点。然而,一方面,磁性纳米金属由于本征磁性和大比表面积,容易引起团聚,从而难以实现其与电磁波的充分交互作用,体现不出很好的吸波性能;另一方面,单一的磁性金属材料环境稳定性差,且对电磁波的耗散能力有限,很难满足高性能电磁波吸收材料的要求。这些都大大限制了磁性纳米金属材料在吸波等领域的应用研究。鉴于此,本论文拟采用原位复合的方法,选择具有不同电磁波损耗机制的材料作为分散介质,在控制纳米磁性金属颗粒尺寸大小、保证良好分散及其稳定性的同时,赋予材料更多的电磁耗散机制,提高复合材料的吸波性能。通过系统研究材料组成、制备条件等因素对复合材料的结构、性能的影响,实现对材料性能的调控,制备具有理想性能的电磁吸波材料。具体研究内容和结果如下:1.以六水硝酸镍为镍源,蔗糖为碳源,将二者按照一定比例混合均匀,得到前驱体。然后,在氢氩混合气氛中,将前驱体高温碳化还原,一步得到Ni-C复合纳米材料。结果表明,复合纳米材料中,镍纳米颗粒均匀的分布在碳基体中,且随着镍比例的升高,镍纳米颗粒的尺寸增加。这是因为蔗糖在高温碳化过程中所形成的碳对Ni纳米颗粒的生长和团聚起到了很好的抑制和隔离作用。通过对产物的磁性和电磁性能研究,结果表明:前驱体比例对Ni的尺寸及复合材料的磁性和电磁性能具有很大的影响,通过优化前驱体比例,可以得到电磁吸波性能很好的碳镍复合材料。例如,样品N5,当吸波层厚度为4mm时,在4.16GHz处是最大反射损耗可达-39.98d B,反射损耗在2.28-6.56GH,8.32-10.88GHz范围内均小于-10d B,表明是一种它是一种理想的电磁吸波材料。2.鉴于碳和镍材料都具有较好的导电性能,不利于实现复合材料与空间的阻抗匹配特性,在上述工作基础上,通过在碳镍体系中引入透波材料Si O2,研究Si O2对复合材料磁性和电磁性能影响。作为一种绝缘的透波材料,Si O2的引入增加电磁波在复合材料内部的通过路径,有利于电磁波的进入复合材料内部,因此有利于保障吸波剂与电磁波之间充分的交互作用。研究结果表明,适当比例Si O2的加入可以起到进一步提高纳米镍颗粒的分散,调控Ni纳米颗粒尺寸的作用,但过量Si O2的引入会降低复合材料中有效吸波剂的比例而影响复合材料整体的吸波性能。在Si O2的含量为0.3ml的条件下(S-0.3),当复合材料吸波层厚度为5mm时,在14.16GH处最大RL值可达-32.3d B,显示其对入射电磁波的吸收可达99%以上,说明得到的复合材料具有优异的吸波性能。3.通过液相还原法制备Ni/Si O2复合物,将其作为前驱体于流动的NH3气氛中,利用氮化镍的热分解性能,通过调节氮化温度和氮化时间得到了一系列不同氮化程度的Ni3N/Si O2复合纳米材料以及不同比例的Ni-Ni3N/Si O2纳米复合材料,并对其进行了磁性和电磁性能的研究。结果表明,纯相Ni3N是一种典型的介电损耗材料,不具有静态铁磁性和动态磁损耗。此外,Ni3N的动态介电性能与其氮化程度具有很大关系,随着氮化程度完全,其介电性能也依次增强。考虑到Ni3N的热分解性,在一定温度下,将氮化镍进行部分分解,制备得到系列Ni-Ni3N/Si O2复合材料,结果表明,通过适当的优化,制备得到的Ni-Ni3N/Si O2复合材料表现出优于Ni/Si O2和Ni3N/Si O2的电磁性能。
[Abstract]:With the rapid development of information engineering, the development of electromagnetic absorbing materials with wide absorption band, thin thickness, strong absorbability and light mass has attracted the attention of all countries in the world. As a result of the intrinsic magnetic and large specific surface area, the sexual nano metal can easily cause reunion, thus it is difficult to realize its full interaction with the electromagnetic wave and can not show good absorbing property. On the other hand, the environment stability of the single magnetic metal material is poor, and the dissipation capacity of the electromagnetic wave is limited, it is difficult to meet the high performance electromagnetic wave absorbing material. The application of magnetic nano metal materials in absorbing wave and other fields is greatly restricted. In view of this, this paper uses in situ composite method to select materials with different electromagnetic wave loss mechanism as dispersion medium to control the size of nano magnetic metal particles and ensure good dispersion and stability. More electromagnetic dissipation mechanism is given to the material to improve the absorbing properties of composite materials. Through the systematic study of the composition of materials, the influence of preparation conditions on the structure and properties of the composites, the control of the properties of the materials and the preparation of the electromagnetic wave absorbing materials with ideal properties are made. The specific content and results are as follows: 1. with six nickel nitrate For the nickel source and sucrose as the carbon source, the precursor was obtained by mixing the two in a certain proportion. Then, the precursor was reduced by carbonization at high temperature in the mixture atmosphere of hydrogen and argon. The Ni-C composite nanomaterials were obtained one step. The results showed that the nickel nanoparticles were evenly distributed in the carbon matrix in the composite nanomaterials, and with the increase of nickel ratio, nickel nanoparticles were increased. The size of the particles increases. This is because the carbon formed in the process of high temperature carbonization has played a very good inhibition and isolation effect on the growth and agglomeration of Ni nanoparticles. By studying the magnetic and electromagnetic properties of the products, the results show that the ratio of precursors has a great effect on the size of Ni and the magnetic and electromagnetic properties of the composites. Sound, by optimizing the ratio of the precursor, the carbon nickel composite material with good electromagnetic wave absorption can be obtained. For example, when the thickness of the absorbing layer is 4mm, the maximum reflection loss can reach -39.98d B at 4.16GHz, and the reflection loss is smaller than -10d B within the 2.28-6.56GH and 8.32-10.88GHz range, indicating that it is an ideal electromagnetic wave absorption. Material.2. has good conductivity in both carbon and nickel materials and is not conducive to the impedance matching characteristics of composite materials and space. On the basis of the above work, the effect of Si O2 on the magnetic and electromagnetic properties of composite materials is studied by introducing Si O2 into the carbon nickel system. The introduction of Si O2 is added as an insulating material. The passing path of electromagnetic wave in the composite is beneficial to the entry of electromagnetic wave into the composite material, so it is beneficial to ensure the full interaction between the absorbing agent and electromagnetic wave. The results show that the addition of Si O2 can further improve the dispersion of nanoscale nanoparticles and regulate the size of Ni nanoparticles. However, the introduction of excess Si O2 will reduce the ratio of effective absorbents in the composite and influence the absorption properties of the composite. When the content of Si O2 is 0.3ml (S-0.3), when the thickness of the composite absorbing layer is 5mm, the maximum RL can reach -32.3d B at 14.16GH, indicating that the absorption of the incident electromagnetic wave can reach more than 99%. The composite material has excellent wave absorption properties.3. by liquid phase reduction method to prepare Ni/Si O2 complex, which is used as precursor in the flow of NH3 atmosphere, using the thermal decomposition properties of nickel nitride, and by adjusting the nitriding temperature and nitriding time, a series of Ni3N/Si O2 composite nanomaterials with different nitriding degrees and different proportions are obtained. The magnetic and electromagnetic properties of Ni-Ni3N/Si O2 nanocomposites have been studied. The results show that the pure phase Ni3N is a typical dielectric loss material with no static ferromagnetism and dynamic magnetic loss. In addition, the dynamic dielectric properties of Ni3N are closely related to the degree of nitriding. With the complete nitriding degree, the dielectric properties are also In turn, taking into account the thermal decomposition of Ni3N, a series of Ni-Ni3N/Si O2 composites are prepared by partial decomposition of nickel nitride at a certain temperature. The results show that, by proper optimization, the prepared Ni-Ni3N/Si O2 composites exhibit better electromagnetic properties than Ni/Si O2 and Ni3N/ Si O2.
【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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