Sintered Magnet Fluoride Coating for Grain Boundary Dy/Tb Control
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Solution Overview
Problem
The challenge is to enhance the coercive force of sintered magnets while minimizing the decrease in magnetic flux density, which is typically compromised by the addition of heavy rare earth elements like Dy or Tb, and to reduce manufacturing costs associated with these elements.
Innovation Solution
A method involving the preparation of a mixed powder by coating fluorides on the surface of magnetic powder, adding heavy rare earth hydrides, and heating, where the fluorides include organic or inorganic fluorides, forming a fluoride film at the grain boundary to prevent the heavy rare earth elements from penetrating the primary phase, thereby maintaining magnetic flux density and increasing coercive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If heavy rare earth elements (Dy or Tb) are added to increase coercive force, then coercive force is improved, but residual flux density is lowered
Solution Approach 1:
The patent applies local quality by concentrating heavy rare earth elements specifically at grain boundaries rather than uniformly distributing them throughout the magnet. This localized placement allows the heavy rare earth elements to exert their maximum effect on coercive force at the critical grain boundary regions while minimizing their impact on the overall magnetic flux density of the bulk material.
Solution Approach 2:
The patent uses grain boundaries as intermediaries to mediate between the heavy rare earth elements and the primary magnetic phase. By positioning heavy rare earth elements at grain boundaries, they act as a buffer zone that enhances coercive force without directly replacing neodymium in the Nd2Fe14B phase, thereby preserving saturation magnetic polarization and residual flux density.
2Force
If heavy rare earth elements are added to increase coercive force, then coercive force is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies partial action by using a small, controlled amount of heavy rare earth elements specifically at grain boundaries rather than throughout the entire magnet. This partial placement achieves the necessary coercive force enhancement with minimal heavy rare earth content, significantly reducing material costs compared to uniform distribution approaches.
Solution Approach 2:
The patent changes the spatial distribution parameter of heavy rare earth elements from uniform concentration to localized concentration at grain boundaries. This parameter change allows achieving the same or better coercive force with lower overall heavy rare earth content, thereby reducing manufacturing costs.
3Force
If neodymium is replaced with Dy or Tb to increase coercive force, then magnetic anisotropy is increased, but saturation magnetic polarization is reduced
Solution Approach 1:
The patent applies local quality by restricting heavy rare earth element substitution to grain boundary regions only, while maintaining the original Nd2Fe14B composition in the primary magnetic phase. This localized substitution preserves the high saturation magnetic polarization of the primary phase while achieving enhanced coercive force through grain boundary engineering.
Solution Approach 2:
The patent segments the magnet structure into distinct regions: the primary Nd2Fe14B phase maintaining high saturation magnetic polarization, and the grain boundary regions containing heavy rare earth elements that provide enhanced coercive force. This segmentation allows each region to optimize its function without compromising the other.
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
This approach effectively increases the coercive force of the sintered magnet while minimizing the decrease in magnetic flux density and reduces the need for expensive heavy rare earth elements, resulting in a high-density, high-performance R—Fe—B-based sintered magnet with improved corrosion resistance and reduced heat generation.
Implementation Method 1
forming a fluoride film at the grain boundary to prevent the heavy rare earth elements from penetrating the primary phase
Implementation Method 2
heating the mixed powder
Data Source
AI summary
A method for preparing a sintered magnet is provided according to one embodiment of the present disclosure. The method includes preparing a mixed powder by coating fluorides on a surface of magnetic powder, adding heavy rare earth hydrides to the mixed powder, and heating the mixed powder, wherein the magnetic powder includes rare earth element-iron-boron-based powder, and the fluorides include at least one of an organic fluoride or an inorganic fluoride.