Fe-Co Alloy Powder for High-Frequency Antennas
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Solution Overview
Problem
Conventional Fe-Co alloy powders with high Co content fail to sufficiently enhance the real part of complex relative permeability (µ') while increasing saturation magnetization (σs), leading to high magnetic loss tangent (tan δ) in high-frequency applications such as antennas.
Innovation Solution
A Fe-Co alloy powder with a mean particle size of 100 nm or less, a coercive force of 52.0 to 78.0 kA/m, and saturation magnetization of 160 Am²/kg or higher, characterized by a specific Co/Fe molar ratio and axial ratio, is produced using a method involving controlled Co addition during precipitation and subsequent reduction and stabilization processes to achieve high µ' and low tan δ.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the Co content in Fe-Co alloy powder is increased to increase saturation magnetization, then saturation magnetization increases, but the real part of complex relative permeability does not sufficiently increase and magnetic loss increases
Solution Approach 1:
The patent changes multiple parameters simultaneously: particle size (reducing to 100 nm or less), coercive force (controlling at 52.0 to 78.0 kA/m), and Co/Fe molar ratio (optimizing at 0.15 to 0.50). These parameter changes resolve the contradiction by creating a specific material state where high saturation magnetization coexists with low magnetic loss and high real part of complex relative permeability
Solution Approach 2:
The patent creates a composite structure with an Fe-Co alloy core and an oxide protection layer. This composite material approach allows the core to provide high saturation magnetization while the oxide layer protects against oxidation and contributes to controlling the overall magnetic properties, achieving low magnetic loss
2Loss of energy
If the particle size of Fe-Co alloy powder is reduced to increase real part of complex relative permeability, then real part increases, but manufacturing precision and control of magnetic properties become more difficult
Solution Approach 1:
The patent performs preliminary action by forming an oxide protection layer on the particle surface during the precipitation process itself, before the reduction step. This preliminary oxidation controls the particle size and surface properties, making subsequent reduction and magnetic property control more precise and reproducible
Solution Approach 2:
The oxide protection layer acts as an intermediary between the Fe-Co alloy core and the external environment. It protects the core from oxidation while allowing controlled interaction with magnetic fields, enabling precise control of magnetic properties even at small particle sizes
3Loss of energy
If the axial ratio of particles is increased to reduce magnetic loss tangent, then magnetic loss tangent decreases, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent controls the axial ratio within a specific range (1.05 to 1.30) through parameter optimization during precipitation. By controlling the Co/Fe molar ratio and precipitation conditions, the desired axial ratio is achieved automatically, reducing manufacturing complexity while maintaining low magnetic loss tangent
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 resulting Fe-Co alloy powder significantly enhances saturation magnetization and controls coercive force, resulting in improved high-frequency characteristics, reduced magnetic loss, and enhanced performance in antennas and other high-frequency devices.
Implementation Method 1
a Fe-Co alloy powder which is advantageous in enhancement of the real part μ' of a complex relative permeability and reduction of a loss tangent tan δ (μ)
Implementation Method 2
For increasing μ', it is effective to increase the saturation magnetization σs of the metal magnetic powder. Generally in Fe-Co alloy powder, there is a tendency of increasing σs with increase of the Co content.
Implementation Method 3
heating a dried product of the precursor to 250 to 650°C in a reducing gas atmosphere to obtain a metal powder having a Fe-Co alloy phase
Implementation Method 4
forming an oxide protection layer on a surface layer portion of a particle of the metal powder after reduction
Data Source
Figure 1~2
AI summary
[Problem] To provide a Fe-Co alloy powder suitable for an antenna, the powder having a high saturation magnetization σs and a controlled coercive force Hc, and providing an extremely large µ' and a sufficiently small tan δ (µ). [Means for Resolution] When introducing an oxidizing agent into an aqueous solution containing Fe ions and Co ions to generate crystal nuclei and cause precipitation and growth of a precursor having Fe and Co as components, Co in an amount corresponding to 40% or more of the total amount of Co used for the precipitation reaction is added to the aqueous solution at a time after the start of the crystal nuclei generation and before the end of the precipitation reaction to obtain the precursor, and then a dried product of the precursor is reduced to obtain a Fe-Co alloy powder. This Fe-Co alloy powder has a mean particle size of 100 nm or less, a coercive force Hc of 52.0 to 78.0 kA/m, and a saturation magnetization σs of 160 Am2/kg or higher.