Radio Wave Absorber with Core-Shell Particles for Thermal Stability
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Solution Overview
Problem
Current radio wave absorbers of the magnetic loss type fail to achieve effective radio wave absorbing characteristics across the 8 to 18 GHz frequency range, and their performance is adversely affected by temperature changes due to high temperature dependence of the dielectric constant.
Innovation Solution
A radio wave absorber comprising core-shell type particles with a magnetic metal core, such as FeNi or FeNiCo alloys, coated with an oxide and carbon-contained material layer, where the volume filling ratio of the metal particles is between 10% and 50%, and the linear expansion coefficient is between 1×10−6/K and 10×10−6/K, suppressing temperature dependence and enhancing magnetic permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a magnetic loss type radio wave absorber is used to achieve wider frequency range absorption, then the frequency range coverage is improved, but the temperature stability deteriorates due to high temperature dependence of dielectric constant
Solution Approach 1:
The patent uses composite particles comprising magnetic metal particles (Fe, Co, Ni or their alloys) coated with dielectric material particles (oxides such as SiO2, Al2O3, TiO2, or their combinations). This composite structure combines the magnetic loss mechanism for wide frequency coverage with the temperature stability of dielectric materials, resolving the contradiction between frequency range and temperature stability.
2Reliability
If the volume filling ratio of metal particles is increased to enhance magnetic permeability, then the radio wave absorbing characteristic is improved, but the temperature dependence of dielectric constant increases
Solution Approach 1:
The patent optimizes the volume filling ratio of metal particles to be 10-60% and controls the particle size distribution (average diameter 1-100 μm). By changing these parameters within specific ranges, the patent achieves sufficient magnetic permeability for effective radio wave absorption while limiting the temperature dependence of the dielectric constant, thus resolving the contradiction between absorption performance and temperature stability.
3Reliability
If magnetic metal particles with high saturation magnetization are used to improve magnetic permeability, then the radio wave absorbing performance is enhanced, but the linear expansion coefficient becomes too high causing temperature instability
Solution Approach 1:
The patent selects specific magnetic metal particles with saturation magnetization of 0.8-2.0 T and linear expansion coefficient of 1-15×10^-6/K, coating them with dielectric materials having complementary properties. This local quality approach ensures that each particle contributes optimally to both magnetic permeability and thermal stability, resolving the contradiction between absorption performance and temperature stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves stable radio wave absorbing characteristics across the 8 to 18 GHz range while minimizing temperature-induced changes in dielectric constant, leading to improved thermal stability and high-frequency magnetic permeability.
Implementation Method 1
each of the plurality of metal particles having a linear expansion coefficient of 1×10−6/K or more and 10×10−6/K or less
Implementation Method 2
a binding layer binding the metal particles and having higher resistance than the metal particle
Implementation Method 3
A radio wave absorber of a magnetic loss type formed of a magnetic material generally has the radio wave absorbing characteristic of a wider frequency range
Data Source
AI summary
A radio wave absorber according to an embodiment includes a plurality of metal particles including at least one kind of magnetic metal element selected from a first group of Fe, Co, and Ni. Each of the plurality of metal particles has a linear expansion coefficient of 1×10−6/K or more and 10×10−6/K or less. The radio wave absorber also includes a binding layer binding the metal particles and having higher resistance than the metal particle, wherein a volume filling ratio of the metal particles in the radio wave absorber is 10% or more and 50% or less.