多孔陶瓷的导电相担载与电磁性能研究

发布时间：2018-08-26 07:33

【摘要】：多孔陶瓷在航空、军事、能源、化工、冶金、环保等许多领域具有重要意义。在多孔陶瓷中担载导电、磁性等功能体,可赋予其新的功能特性,对于探索负介电常数、负磁导率具有重大理论意义,在军用大功率微波管衰减体等结构功能一体化材料领域具有重要应用背景。本文以耐高温、耐老化、化学稳定性优异的氧化铝陶瓷和亚铁磁性的钇铁石榴石陶瓷为载体,利用浸渍法在多孔陶瓷中担载导电相,制备了含导电相的陶瓷基复合材料。通过改变基体类别、导电相种类、组分和微观形貌对负介电常数和负磁导率进行调控。利用XRD、SEM、VSM、HP4991阻抗分析仪对复合材料进行测试分析,结合逾渗现象、等效电路、自由电子模型等理论研究了影响复合材料电磁行为的因素,在特定的频段实现了负介电常数和负磁导率。以多孔氧化铝陶瓷为基体成功制备了Co/Al2O3、C/Al2O3复合材料。在CO/Al2O3复合材料中,随着钴含量的增加,三维金属钴网络逐渐形成并均匀分布在氧化铝陶瓷的孔壁上,在逾渗阈值附近复合材料的电磁性能发生突变。高于逾渗阂值的样品,由于等效电感的出现导致负介电。而负磁导率的产生是由于金属钴网络的涡流共振以及磁共振引起。用化学方法处理CO/Al2O3复合材料,可以使原来颗粒状钴变为低维片状结构,钴网络的破坏使负介电现象消失,说明三维钴网络的形成对负介电和负磁导率是至关重要的；在C/Al2O3复合材料中,蔗糖碳化后在多孔氧化铝孔壁上形成一层碳的膜状结构,随着碳含量的增加膜连续性增强且变厚,从而在高频电磁场下导电通路增多。当碳含量为14 wt%时,由于等离子体共振介电常数全部为负值,磁导率表现出抗磁性。以多孔钇铁石榴石陶瓷为基体成功制备了Co/YIG、C/YIG复合材料。在CoA/YIG中,随着钴含量的增加,钴由颗粒状逐渐连接为三维网络状均匀分布在YIG孔壁上。钴含量为35 wt%时,CoA/YIG复合材料在575 M-1G频段内出现双负性质。其负介电出现机理与Co/Al2O3类似,而负磁导率是由于基体的畴壁共振、磁旋共振等以及三维导电网络的涡流共振引起的；对于C/YIG复合材料,碳化后YIG孔壁上的碳主要有颗粒状和不规则片层状两种形貌。随着碳含量的增加,复合材料导电性增强,负介电出现并且表现出抗磁性。
[Abstract]:Porous ceramics are of great significance in aviation, military, energy, chemical, metallurgical, environmental protection and many other fields. It is of great theoretical significance to study the negative permittivity and permeability of porous ceramics by adding new functional properties such as conductive, magnetic and other functional materials to porous ceramics. It has an important application background in the field of structural and functional integrated materials such as high power microwave tube attenuators. In this paper, ceramic matrix composites containing conductive phase were prepared by impregnation method on the carrier of alumina ceramics with high temperature, aging resistance and chemical stability and yttrium iron garnet ceramics with ferromagnetic properties. The negative permittivity and permeability are regulated by changing the type of matrix, the type of conductive phase, the composition and the microscopic morphology. The XRD,SEM,VSM,HP4991 impedance analyzer was used to test and analyze the composite materials. The factors influencing the electromagnetic behavior of the composites were studied by combining the percolation phenomenon, equivalent circuit and free electron model. Negative permittivity and negative permeability are realized in specific frequency band. Co/Al2O3,C/Al2O3 composites were successfully prepared by using porous alumina ceramics as substrate. In CO/Al2O3 composites, with the increase of cobalt content, the three-dimensional metallic cobalt network is gradually formed and uniformly distributed on the pore wall of alumina ceramics, and the electromagnetic properties of the composites have a sudden change near the percolation threshold. When the percolation threshold is higher than the percolation threshold, the negative dielectric is caused by the appearance of equivalent inductance. The negative permeability is caused by eddy current resonance of cobalt metal network and magnetic resonance. The chemical treatment of CO/Al2O3 composites can make the original granular cobalt become low-dimensional flake structure, and the destruction of cobalt network can make the negative dielectric phenomenon disappear, which indicates that the formation of three-dimensional cobalt network is very important to negative dielectric and negative permeability. In C/Al2O3 composites, a layer of carbon film structure was formed on the porous alumina pore wall after sucrose carbonization. With the increase of carbon content, the continuity and thickness of the film became stronger and thicker, resulting in the increase of conductive pathways in high frequency electromagnetic field. When the carbon content is 14 wt%, the permeability is diamagnetic because the plasmon resonance permittivity is negative. Co/YIG,C/YIG composites were successfully prepared from porous yttrium iron garnet ceramics. In CoA/YIG, with the increase of cobalt content, cobalt is gradually connected from granular to three-dimensional network to distribute uniformly on the wall of YIG pore. When the cobalt content is 35 wt%, the CoA / YIG composite exhibits double negative properties in the 575M-1G band. The negative permittivity is similar to that of Co/Al2O3, and the negative permeability is caused by domain wall resonance of matrix, magnetic spin resonance and eddy current resonance of three-dimensional conductive network. After carbonization, there are two kinds of carbon on the wall of YIG pore: granular and irregular lamellar. With the increase of carbon content, the conductivity of composites increases, negative dielectric appears and shows diamagnetism.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ174.1

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