NdFeB Magnet Surface Dysprosium Diffusion for Coercivity
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Solution Overview
Problem
Current methods for producing high coercivity neodymium-iron-boron (Nd—Fe—B) magnets, enhanced with dysprosium, face challenges due to the high cost of rare earth elements and performance losses during annealing processes, which affect magnetization and coercivity.
Innovation Solution
A bulk permanent magnet with a neodymium-iron-boron core having a coercivity-enhancing element only on its outer surface, where a pulse thermal process heats the surface to a higher temperature than the interior, inducing limited diffusion of the element, thereby enhancing coercivity without penetrating the core.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dysprosium is added in bulk to improve high temperature coercivity, then coercivity is enhanced, but magnetization is significantly reduced and production cost increases
Solution Approach 1:
The patent applies local quality by concentrating the coercivity-enhancing element (dysprosium) specifically at the grain boundaries and surface regions where it is most effective for coercivity enhancement, rather than distributing it uniformly throughout the bulk. This localized placement maintains high coercivity while preserving bulk magnetization properties.
Solution Approach 2:
The patent segments the distribution of dysprosium into distinct regions: grain boundary regions receive higher concentrations for coercivity enhancement, while the bulk magnetization regions maintain lower concentrations to preserve magnetic performance. This segmentation allows independent optimization of coercivity and magnetization.
2Reliability
If dysprosium is added in bulk to improve high temperature coercivity, then coercivity is enhanced, but production cost increases significantly
Solution Approach 1:
By localizing dysprosium to grain boundaries and surface regions rather than bulk addition, the patent reduces the total quantity of expensive rare earth elements required, thereby significantly lowering production costs while maintaining coercivity enhancement effectiveness.
Solution Approach 2:
The patent applies partial action by using only the minimum necessary amount of dysprosium concentrated at critical locations (grain boundaries and surfaces) rather than excessive bulk addition, achieving the required coercivity enhancement with reduced material cost.
3Stability of the object's composition
If the magnet is annealed at elevated temperatures for extended periods to ensure diffusion of Dy throughout the bulk, then diffusion is improved, but performance loss occurs due to extended exposure
Solution Approach 1:
The patent places dysprosium pre-positioned at grain boundaries and surface regions before the final magnetization step, so that the coercivity enhancement is already in place before any annealing processes. This preliminary placement eliminates the need for extended annealing to achieve bulk diffusion, thereby preserving magnetic performance.
Solution Approach 2:
The patent employs controlled, periodic thermal treatments rather than extended continuous annealing, allowing sufficient diffusion at grain boundaries without prolonged exposure that would cause performance degradation. The thermal process is applied in controlled intervals to achieve the desired diffusion without excessive heat exposure.
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 improves the energy product of Nd—Fe—B magnets by selectively increasing coercivity on the surface, reducing the need for bulk dysprosium and minimizing performance losses, resulting in a more cost-effective and efficient production method.
Implementation Method 1
subjecting the coated permanent magnet to a pulse thermal process that heats the outer surface to a substantially higher temperature than an interior portion of the neodymium-iron-boron core substrate
Implementation Method 2
the substantially higher temperature is of sufficient magnitude to induce diffusion of the coercivity-enhancing element below the outer surface
Data Source
AI summary
A bulk high performance permanent magnet comprising a neodymium-iron-boron core having an outer surface, and a coercivity-enhancing element residing on at least a portion of said outer surface, with an interior portion of said neodymium-iron-boron core not having said coercivity-enhancing element therein. Also described herein is a method for producing the high-coercivity bulk permanent magnet, the method comprising: (i) depositing a coercivity-enhancing element on at least a portion of an outer surface of a neodymium-iron-boron core substrate to form a coated permanent magnet; and (ii) subjecting the coated permanent magnet to a pulse thermal process that heats said outer surface to a substantially higher temperature than an interior portion of said neodymium-iron-boron core substrate, wherein said substantially higher temperature is at least 200° C. higher than said interior portion and is of sufficient magnitude to induce diffusion of said coercivity-enhancing element below said outer surface but outside of said interior portion.