3D Grain Boundary Diffusion in NdFeB Magnets for Higher Coercivity
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Solution Overview
Problem
Current methods for enhancing the intrinsic coercivity of neodymium-iron-boron magnets, such as adding heavy rare earth elements, increase costs and reduce remanence, while grain boundary diffusion primarily deposits heavy rare earth on the surface, failing to penetrate deeply into the magnet.
Innovation Solution
The method involves three-dimensional grain boundary diffusion, where heavy rare earth elements like Dy and Tb are diffused into the surface layer of macroscopic neodymium-iron-boron magnets, creating a diffusion region while maintaining a non-diffusion core, allowing for adjustable diffusion depths and increased coercive force without significantly reducing remanence or maximum magnetic energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If heavy rare earth elements (Dy/Tb) are added in the smelting stage to improve intrinsic coercivity, then coercivity increases, but cost increases significantly and remanence decreases
Solution Approach 1:
The patent applies local quality by concentrating heavy rare earth elements specifically at the grain boundary regions rather than uniformly distributing them throughout the magnet. This localized enrichment at grain boundaries achieves coercivity enhancement while minimizing the overall amount of heavy rare earth needed, thereby preserving remanence and reducing cost.
Solution Approach 2:
The patent uses grain boundary diffusion as an intermediary mechanism to transport heavy rare earth elements from the surface coating into the magnet's grain boundary regions. This diffusion process acts as a mediator that delivers the necessary elements to the critical grain boundary zones without requiring bulk addition to the smelting stage.
2Force
If grain boundary diffusion is used to improve intrinsic coercivity, then coercivity increases with minimal reduction in remanence, but the diffusion process only deposits heavy rare earth on the surface layer and rarely enters the inside of grains
Solution Approach 1:
The patent transitions from traditional two-dimensional surface coating to three-dimensional grain boundary diffusion by utilizing the grain boundary network that penetrates throughout the magnet's volume. This dimensional transformation allows heavy rare earth elements to reach interior regions through the interconnected grain boundary pathways, achieving uniform distribution throughout the magnet rather than just surface deposition.
Solution Approach 2:
The patent exploits the grain boundary structure as a porous or interconnected network that facilitates deep penetration of heavy rare earth elements. The grain boundaries act as diffusion channels that allow elements to traverse from the surface into the interior of the magnet, overcoming the limitation of surface-only deposition.
3Force
If a large amount of heavy rare earth is added to increase coercivity, then coercivity improves, but the volume fraction of matrix phase Nd2Fe14B decreases and remanence is significantly reduced
Solution Approach 1:
The patent applies local quality by concentrating heavy rare earth elements specifically at the grain boundary regions rather than uniformly distributing them throughout the magnet. This localized enrichment at grain boundaries achieves coercivity enhancement while minimizing the overall amount of heavy rare earth needed, thereby preserving remanence and reducing cost.
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 enhances the coercive force of neodymium-iron-boron magnets by 2-15 kOe, achieves ultra-high performance with remanence greater than 14.85 kGs and coercivity greater than 21 kOe, and reduces the amount of heavy rare earth needed, making the process more cost-effective and suitable for industrial application.
Implementation Method 1
the grain boundary diffusion process has been used to increase the intrinsic coercivity of sintered neodymium iron boron, with very little reduction in the remanence and magnetic energy product of the magnet
Data Source
AI summary
A neodymium-iron-boron magnet is provided. The neodymium-iron-boron magnet is subject to diffusion and permeation of a heavy rare earth element, the neodymium-iron-boron magnet includes a heavy-rare-earth diffusion region at a surface layer and a core non-diffusion region, and the neodymium-iron-boron magnet has the heavy-rare-earth diffusion region at regions, which have normal directions consistent with three axes of a three-dimensional Cartesian coordinate system, of the surface layer. The present application extends the principle of diffusion from microscopic grains to macroscopic magnets. Diffusion layers of different depths may be obtained by adjusting temperature and time of heat treatment. Through the magnetic hardening of the surface layer of the magnet, the coercive force of the magnet is increased, and the magnet remanence (Br) and the maximum magnetic energy level (BHmax) are very slightly reduced. The producing process is simple, and highly controllable.