Rare-Earth Magnet Grain Boundary Diffusion
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Solution Overview
Problem
Existing methods for preparing rare-earth permanent magnets face challenges in efficiently diffusing heavy rare-earth elements into grain boundaries, which limits the improvement of magnetic characteristics and increases manufacturing costs due to excessive consumption of these expensive elements.
Innovation Solution
A method involving the diffusion of a light rare-earth element into the grain boundary of an R-T-B-based sintered magnet, followed by the diffusion of a heavy rare-earth element under reduced atmosphere conditions, to enhance the magnetic characteristics while minimizing the consumption of heavy rare-earth elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a heavy rare-earth element is directly diffused into the grain boundary of a conventional rare-earth permanent magnet, then the coercive force is improved, but the consumption of heavy rare-earth element increases considerably and manufacturing cost increases
Solution Approach 1:
A light rare-earth element is introduced as an intermediary substance that facilitates the diffusion of heavy rare-earth elements into the grain boundary. The light rare-earth element forms a diffusion pathway or intermediate phase that enables more efficient transport and incorporation of the heavy rare-earth element, thereby reducing the overall consumption of expensive heavy rare-earth materials while achieving the desired coercive force enhancement.
Solution Approach 2:
The light rare-earth element is diffused into the grain boundary first as a preliminary step before introducing the heavy rare-earth element. This preliminary diffusion prepares the grain boundary structure, creates favorable conditions for subsequent heavy rare-earth element incorporation, and ensures more efficient utilization of the heavy rare-earth element when it is introduced.
2Strength
If the grain size is reduced to improve coercive force, then the magnetic characteristic is improved, but the degree of oxidation increases and manufacturing cost increases
Solution Approach 1:
Instead of uniformly reducing the entire magnet structure to smaller grain sizes, the invention applies local modifications at the grain boundary regions through selective diffusion of rare-earth elements. This localized approach enhances coercive force at the critical grain boundary interfaces without requiring comprehensive grain size reduction throughout the entire material, thereby minimizing oxidation exposure and associated manufacturing costs.
3Strength
If a heavy rare-earth element is diffused into the grain boundary to improve magnetic characteristic, then the coercive force increases, but the diffusion process is insufficient and magnetic characteristic improvement is limited
Solution Approach 1:
The light rare-earth element serves as a diffusion mediator that enhances the penetration and distribution of heavy rare-earth elements into the grain boundary. This intermediary mechanism overcomes diffusion barriers and achieves more uniform and thorough incorporation of the heavy rare-earth element, thereby achieving the desired magnetic characteristic improvement that was not attainable through direct diffusion alone.
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 method effectively improves the coercive force and residual magnetic flux density of rare-earth permanent magnets, reducing manufacturing costs by optimizing the content of heavy rare-earth elements in the grain boundary.
Implementation Method 1
a light rare-earth element may be diffused into a grain boundary
Implementation Method 2
a heavy rare-earth element may be diffused into the grain-boundary under reduced atmosphere conditions
Data Source
AI summary
Disclosed is a method for preparing a rare-earth permanent magnet. The method includes: preparing an R-T-B-based sintered magnet; applying a first mixture including a light rare-earth element onto the surface of the R-T-B-based sintered magnet and diffusing the first mixture under a vacuum atmosphere to prepare a light rare-earth permanent magnet having the light rare-earth element diffused into a grain boundary; and applying a second mixture including a heavy rare-earth element onto the surface of the light rare-earth permanent magnet and diffusing the second mixture into the grain-boundary under a vacuum atmosphere to prepare a rare-earth permanent magnet.