Core-Shell Radiowave Absorber for 8-18 GHz Band
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Solution Overview
Problem
Magnetic-loss type radiowave absorbers with excellent characteristics in the 8 to 18 GHz band (X-band or Ku-band) have not been realized, as existing absorbers either have poor absorption characteristics or require excessive thickness for practical absorption.
Innovation Solution
A radiowave absorber comprising core-shell particles with a magnetic metal core and an oxide-carbon shell structure, where the core contains Fe, Co, and Ni, and the shell includes an oxide layer and a carbon-containing material, bound by a resin or inorganic material, with a volume filling rate between 10% and 55%, enhancing magnetic permeability and absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If magnetic-loss type radiowave absorbers are designed for wider band absorption, then absorption bandwidth is improved, but absorption characteristics in specific high-frequency bands (8-18 GHz) deteriorate
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core portion contains magnetic metal elements (Fe, Co, Ni) for magnetic loss, while the shell layer contains dielectric materials (oxides like SiO2, TiO2, Al2O3) for dielectric loss. This spatial differentiation allows each layer to contribute to absorption in its optimal frequency range, with the overall structure achieving excellent absorption characteristics specifically in the 8-18 GHz band while maintaining wider band coverage.
2Reliability
If absorber thickness is increased to improve absorption characteristics, then absorption performance is improved, but device compactness and practical applicability deteriorate
Solution Approach 1:
The patent employs composite materials by combining magnetic metal core particles with dielectric oxide shell materials to form core-shell structured composite particles. This composite structure enables simultaneous magnetic and dielectric loss mechanisms, achieving high absorption performance with reduced thickness. The synergistic effect of the composite structure allows the absorber to achieve excellent absorption characteristics in the 8-18 GHz band without requiring excessive thickness, thus maintaining compactness and practical applicability.
3Reliability
If magnetic metal content is increased to enhance magnetic permeability, then absorption capability is improved, but oxidation resistance and thermal stability deteriorate
Solution Approach 1:
The patent uses the shell layer as an intermediary protective barrier between the magnetic metal core and the external environment. The shell layer comprises oxide materials (SiO2, TiO2, Al2O3, ZnO, etc.) that provide oxidation resistance and thermal stability, preventing direct exposure of the magnetic metal core to oxygen and heat. This intermediary structure allows the magnetic core to maintain high magnetic permeability for enhanced absorption capability while the shell protects against oxidation and thermal degradation.
4Reliability
If particle aggregation is prevented to maintain performance, then absorption characteristics are improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts the problematic aggregation issue by designing a core-shell structure where the shell layer acts as a physical separator between core particles. The shell layer comprises oxide materials that prevent direct contact between magnetic metal cores, thereby preventing aggregation and maintaining dispersion. This structural extraction of the aggregation problem into the shell layer design allows for simpler manufacturing processes compared to requiring complex surface treatments or dispersant additions.
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 described radiowave absorber achieves high-frequency absorption characteristics with high loss in the 8-18 GHz band, maintaining thermal stability and oxidation resistance, while preventing aggregation and grain growth, thus providing effective radiowave absorption without excessive thickness.
Implementation Method 1
A radiowave absorber of a magnetic-loss type using a magnetic material normally has absorption characteristics for a wider band
Implementation Method 2
radiowave absorbers of a dielectric-loss type or a conduction-loss type
Implementation Method 3
a binding layer that binds the core-shell particles
Data Source
AI summary
A radiowave absorber of an embodiment includes: core-shell particles each including: a core portion that contains at least one magnetic metal element selected from a first group including Fe, Co, and Ni, and at least one metal element selected from a second group including Mg, Al, Si, Ca, Zr, Ti, Hf, Zn, Mn, rare-earth elements, Ba, and Sr; and a shell layer that coats at least part of the core portion, and includes an oxide layer containing at least one metal element selected from the second group and contained in the core portion; and a binding layer that binds the core-shell particles, and has a higher resistance than the resistance of the core-shell particles. The volume filling rate of the core-shell particles in the radiowave absorber is not lower than 10% and not higher than 55%.