Rare-Earth Magnet Grain Boundary Diffusion for High Coercivity
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Solution Overview
Problem
The use of heavy rare earth elements like Dy and Tb to increase coercivity in Nd2Fe14B magnets leads to increased manufacturing costs and reduces residual magnetic flux density, necessitating a more cost-effective method to enhance coercivity while maintaining magnetic flux density.
Innovation Solution
A method involving the application of grain boundary diffusion using a combination of heavy and light rare earth element hydrides, such as Dy, Tb, and Nd hydrides, to form a diffusion layer in the crystal grain boundaries of Nd2Fe14B magnets, reducing the amount of heavy rare earth usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy rare earth elements (Dy, Tb) are added to increase coercivity, then coercivity is improved, but manufacturing cost increases and residual magnetic flux density decreases
Solution Approach 1:
The patent applies local quality by concentrating heavy rare earth elements specifically at the crystal grain boundaries through diffusion treatment, rather than uniformly distributing them throughout the magnet. This localized enrichment at boundaries (where reverse magnetic domains nucleate) maximizes coercivity enhancement while minimizing the overall amount of heavy rare earth needed, thereby preserving bulk magnetic flux density.
Solution Approach 2:
The patent uses light rare earth elements (Nd, Pr) as intermediaries that form a diffusion layer at the grain boundaries, facilitating the controlled distribution of heavy rare earth elements. This intermediary mechanism allows heavy rare earth to be effectively positioned where needed without requiring large quantities, thus maintaining residual magnetic flux density while achieving high coercivity.
2Reliability
If heavy rare earth elements (Dy, Tb) are added to increase coercivity, then coercivity is improved, but manufacturing cost increases
Solution Approach 1:
By localizing heavy rare earth elements at grain boundaries through diffusion treatment, the patent minimizes the total quantity of expensive heavy rare earth materials required. This localized approach achieves the necessary coercivity enhancement with significantly reduced material costs compared to uniform distribution methods.
Solution Approach 2:
The patent creates a composite structure combining light rare earth elements (abundant, low-cost) as the matrix with heavy rare earth elements (scarce, high-cost) concentrated at grain boundaries. This composite approach leverages the cost-effectiveness of light rare earth while utilizing heavy rare earth only where necessary for performance, optimizing the cost-performance ratio.
3Reliability
If Nd is substituted with Dy or Tb in Nd2Fe14B compound, then anisotropic magnetic field and coercivity increase, but saturation magnetic polarization decreases
Solution Approach 1:
The patent applies local quality by restricting heavy rare earth substitution to the crystal grain boundary regions through diffusion treatment, rather than substituting throughout the entire crystal structure. This localized substitution enhances coercivity at boundaries (where magnetic domain reversal initiates) while preserving the saturation magnetic polarization of the bulk Nd2Fe14B compound.
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 lowers manufacturing costs by minimizing heavy rare earth element usage while maintaining or improving coercivity and residual magnetic flux density.
Implementation Method 1
performing grain boundary diffusion by heat-treating the sintered body, wherein the grain boundary diffusion material includes a heavy rare earth element (HREE) hydride and a light rare earth element (LREE) hydride
Data Source
AI summary
An embodiment discloses a method of manufacturing a rare-earth magnet, the method including: preparing a magnetic sintered body including RE, Fe, and B as compositional components (RE is selected from one or two or more selected from rare earth elements); applying a solution containing a grain boundary diffusion material to the sintered body; and performing grain boundary diffusion by heat-treating the sintered body, wherein the grain boundary diffusion material includes a heavy rare earth element (HREE) hydride and a light rare earth element (LREE) hydride.