Flat Amorphous Soft Magnetic Powder for High-Permeability EMI Sheets
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Solution Overview
Problem
Existing amorphous soft magnetic alloy powders have small particle diameters, making it difficult to achieve high coverage and magnetic permeability in electromagnetic wave suppression sheets without increasing concentration, and high aspect ratios lead to decreased demagnetizing field coefficients.
Innovation Solution
Developing an amorphous alloy soft magnetic powder with a flat shape and a volume-based average particle diameter of 150 μm to 500 μm, and a coercive force of 398 A/m or less, manufactured using a method involving a molten metal supply and a swirling coolant flow to achieve high magnetic permeability and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the particle diameter of amorphous soft magnetic alloy powder is increased to improve coverage and magnetic permeability, then the coverage and magnetic permeability increase, but the particle becomes harder to rapidly solidify into an amorphous structure
Solution Approach 1:
The patent employs a high-speed rotating water flow method where molten metal is supplied to a high-speed rotating water flow, causing rapid cooling and solidification. The hydraulic action of the high-velocity water flow enables rapid heat extraction from the molten metal particles, facilitating amorphous structure formation even in larger particles (150-500 μm) that would otherwise be difficult to solidify rapidly.
Solution Approach 2:
The patent utilizes the phase transition from molten metal to solid amorphous structure through rapid cooling. By controlling the cooling rate through the high-speed water flow, the metal skips the crystalline phase and transitions directly to an amorphous solid state, achieving the desired particle morphology and magnetic properties.
2Shape
If the aspect ratio of particles is increased to reduce demagnetizing field coefficient, then magnetic permeability improves, but particle strength decreases and particles become more prone to breakage
Solution Approach 1:
The patent optimizes the aspect ratio parameter within a specific range (3-5) to balance magnetic performance and mechanical strength. By controlling the aspect ratio within this optimized range during the rapid solidification process, the particles achieve sufficient flatness to reduce demagnetizing field coefficients while maintaining adequate strength to prevent breakage during handling and processing.
3Volume of moving object
If the particle diameter is increased to improve coverage, then fewer particles are needed per unit area, but the coercive force tends to increase
Solution Approach 1:
The high-speed rotating water flow method provides extremely rapid and uniform cooling throughout the particle volume, even in larger particles. This uniform rapid cooling creates a homogeneous amorphous structure without internal stresses or crystalline regions that would increase coercive force, thereby maintaining low coercive force (398 A/m or less) despite the increased particle diameter.
Solution Approach 2:
The rapid solidification process ensures homogeneous amorphous structure formation throughout the particle volume. The uniform cooling rate achieved through the high-speed water flow prevents localized crystallization or stress concentration, resulting in particles with consistent magnetic properties and low coercive force across the entire particle population.
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 allows for the production of electromagnetic wave suppressors with high coverage and magnetic permeability without the need for high concentrations of the powder, while maintaining low coercive force and mechanical integrity.
Implementation Method 1
a coolant outflow portion that causes a coolant to flow out along an inner circumferential surface of the tubular body to form a swirling flow
Implementation Method 2
supplying a jet flow of a molten metal flow to the cooling water layer to cause the molten metal to be divided and rapidly solidified
Implementation Method 3
a volume-based average particle diameter of more than 150 μm and 500 μm or less measured by a laser diffraction and scattering particle size distribution analyzer
Implementation Method 4
a volume-based average particle diameter of more than 150 μm and 500 μm or less measured by a laser diffraction and scattering particle size distribution analyzer
Data Source
AI summary
An amorphous alloy soft magnetic powder contains a particle having a flat shape, has a volume-based average particle diameter of more than 150 μm and 500 μm or less measured by a laser diffraction and scattering particle size distribution analyzer, and has a coercive force of 398 A/m or less, i.e., 5.0 Oe or less. A proportion of particles having a particle diameter of more than 300 μm and 600 μm or less classified by sieving may be 15 mass % or more and 40 mass % or less.