Magnetic Dust Core with MxFe2-xSiO4 Grain Boundary Layer
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Solution Overview
Problem
Existing dust cores with ferrite insulating layers suffer from low specific resistance after heat treatment, as the insulating layer can alter to low-resistance Fe3O4 and FeO due to Fe diffusion from soft magnetic particles, leading to inadequate reduction of eddy-current and hysteresis losses.
Innovation Solution
A dust core with a novel insulating layer comprising MxFe2-xSiO4 at grain boundaries, where M represents one or more divalent metal elements, is formed by coating soft magnetic particles with a silicone resin and spinel-type ferrite, which maintains high specific resistance even after heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferrite insulating layers are used at grain boundaries of soft magnetic particles, then magnetic properties are improved, but specific resistance deteriorates after heat treatment due to transformation into low-resistance Fe3O4 and FeO
Solution Approach 1:
The patent changes the chemical composition parameters of the insulating layer by introducing silicon oxide (SiO2) to form a new compound MxFe2-xSiO4. This compositional modification prevents the transformation into low-resistance Fe3O4 and FeO during heat treatment, thereby maintaining high specific resistance while preserving magnetic properties.
Solution Approach 2:
The patent creates a composite insulating layer combining traditional ferrite (Mg-containing oxide-coated soft magnetic particles) with silicon oxide. This composite structure MxFe2-xSiO4 integrates the magnetic properties of ferrite with the high resistance characteristics of silicon oxide, achieving both magnetic performance and electrical insulation stability after heat treatment.
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 effectively reduces eddy-current and hysteresis losses, ensuring stable high specific resistance and reliable iron loss reduction in dust cores, even under high-temperature conditions.
Implementation Method 1
the insulating layer of ferrite may alter to low-resistance Fe3O4 and/or FeO due to Fe that diffuses from the soft magnetic particles
Implementation Method 2
dust core of high specific resistance that has a novel insulating layer different from conventional ones at the grain boundaries of soft magnetic particles
Implementation Method 3
When dust cores are subjected to heat treatment (annealing) for removal of strain to reduce the hysteresis loss
Implementation Method 4
The grain boundary layer has a compound layer comprising MxFe2-xSiO4 (0≤x≤1, M: one or more types of metal elements that serve as divalent cations)
Data Source
AI summary
A dust core that can significantly reduce the iron loss is provided. The dust core of the present invention includes soft magnetic particles comprising pure iron or an iron alloy and a grain boundary layer existing between adjacent soft magnetic particles. The grain boundary layer has a compound layer comprising MxFe2-xSiO4 (0≤x≤1, M: one or more types of metal elements that serve as divalent cations). Such a dust core is obtained by annealing a compact. The compact is obtained by compression-molding a powder for magnetic cores. In the powder for magnetic cores, coating layers that coat the surfaces of soft magnetic particles are each composed of a composite phase in which spinel-type ferrite represented by MyFe3-yO4 (0≤y≤1, M: one or more types of metal elements that serve as divalent cations) is dispersed on a surface of a silicone resin or inside the silicone resin. The dust core after annealing exhibits a high specific resistance due to the grain boundary layer having the compound layer and can reduce both the eddy-current loss and the hysteresis loss.