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Electromagnetic wave absorbing composite equivalent parameters of microwave

Author: LiuTao
Tutor: DengLongJiang
School: University of Electronic Science and Technology
Course: Electronic information materials and components
Keywords: Maxwell-Garnett mixing equation Effective permeability Nanocrystalline CST MICROWAVE STUDIO
CLC: TM25
Type: Master's thesis
Year: 2010
Downloads: 148
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Abstract

With the development of radar technology, the traditional absorbing material has been unable to meet the real needs of nanocrystalline soft magnetic materials with high saturation magnetization and low coercivity and nano-specific effects, making it a new generation of High-frequency magnetic materials. According to the magnetic limit relationship, flaking particles help to improve microwave permeability, expansion absorption band. Based on the above considerations, the subject was prepared by wet milling process flaky FeSiAl nanocrystalline alloys, in-depth study preparation process (ball speed, ball feed ratio, milling time, etc.) on the morphology and nanocrystalline alloy static and dynamic magnetic properties effects, thereby to determine the optimal process conditions. Radar absorbing material is usually caused by the base absorbent body (adhesive) to form a complex. Absorbing materials and composite performance of the merits of effective permeability and permittivity are closely related. Calculate the equivalent magnetic absorbing electromagnetic parameters of composite academic research has been one of major basic issues, the core content includes mixing equation and mechanism of resonance and expression. To solve these difficulties, we can quickly and accurately designed with the expected electromagnetic properties of the material. Previous studies found that the same are arranged in a matrix of tabular ferromagnetic particles in favor of improved absorbing properties. In order to conduct in-depth research, the authors used commercial software CST Microwave Studio modeling and simulation studies consistently ranked tabular ferromagnetic particles in the matrix orientation and spatial distribution on the impact of effective permeability and the two factors into account Maxwell-Garnett mixing formula, make the appropriate improvements. Different models calculated equivalent permeability theoretical values more consistent with the simulation results. Further, when the flaky particles in the orientation of the matrix is not unique, the authors used a semi empirical successfully predicted theoretical formula of the composite effective permeability. Nanocrystalline particles in the gigahertz frequency band is the main mechanism of natural resonant magnetic resonance and exchange resonance. Thus, Landau-Lifshitz-Gilbert equations can be used to calculate the intrinsic permeability. This paper focuses on different morphologies (spherical, flake, fibrous) of nanocrystalline particles randomly oriented in the matrix and consistent orientation of resonant expression. Taking into account percolation and dipole - dipole interaction between particles equivalent electromagnetic parameters influence on the Maxwell-Garnett equation for further improvement. Calculated under the conditions of two orientations flaky nanocrystalline composite effective permeability good agreement with the experimental values. This means that the static magnetic parameters directly from the different orientations of departure to calculate the equivalent composite microwave parameters as possible, for the magnetic properties of absorbing materials designed to lay a theoretical foundation.

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