NdFeB Magnet Grain Boundary Diffusion via Alloy Coating
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Solution Overview
Problem
Current methods for improving coercive force and thermal demagnetization characteristics of rare earth permanent magnets, such as grain boundary diffusion, face challenges including high manufacturing costs, poor productivity, and limitations in diffusing dysprosium and terbium elements due to substitution reactions and oxide or fluoride suppression.
Innovation Solution
A method involving coating a NdFeB sintered magnet with a grain boundary diffusion material containing rare earth hydrate or fluoride and cobalt, followed by heat treatment to diffuse these elements into the grain boundary, optimizing the atomic percentages and melting points to enhance coercive force and thermal characteristics while omitting the need for oxide film removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grain boundary diffusion is used to improve coercive force, then magnetic characteristics are improved, but manufacturing costs increase and productivity decreases
Solution Approach 1:
The invention changes the chemical form of rare earth elements from oxide/fluoride to metal alloy powder form, and modifies the diffusion mechanism by adding aluminum element. This parameter change enables simple coating processes while achieving effective grain boundary diffusion, resolving the contradiction between improved coercive force and maintained productivity
Solution Approach 2:
The invention uses composite alloy powder containing rare earth elements (Dy, Tb) combined with aluminum and other metals as the coating material. This composite structure allows the rare earth elements to diffuse effectively into grain boundaries while the aluminum component facilitates the diffusion process, achieving both improved magnetic characteristics and manufacturing efficiency
2Ease of manufacture
If oxide or fluoride coating is applied for grain boundary diffusion, then coating process is simple, but element diffusion is suppressed due to substitution reactions
Solution Approach 1:
The invention changes the chemical state of rare earth elements from oxidized/fluorinated forms to metallic alloy powder form. This parameter change eliminates substitution reactions that suppress diffusion, allowing effective grain boundary diffusion while maintaining simple coating application processes
Solution Approach 2:
Aluminum element acts as an intermediary that facilitates the diffusion of rare earth elements into grain boundaries. The aluminum forms intermediate compounds during heat treatment that promote the release and diffusion of rare earth atoms, overcoming the suppression effect that would occur with oxide/fluoride coatings
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 coercive force and thermal demagnetization characteristics of rare earth permanent magnets, simplifies the production process, and reduces production costs by ensuring uniform diffusion and enhanced magnetic properties.
Implementation Method 1
heat-treating the same to diffuse the rare earth element into the grain boundary of a sintered magnet
Data Source
AI summary
Disclosed is a method of producing a rare earth permanent magnet including preparing a NdFeB sintered magnet, coating a surface of the NdFeB sintered magnet with a grain boundary diffusion material including R hydrate or R fluoride, and RaMb or M, to form a grain boundary diffusion coating layer, and diffusing the grain boundary diffusion material into a grain boundary of the NdFeB sintered magnet by heat treatment, wherein M is a metal having a melting point higher than a heat treatment temperature during the diffusion, R is a rare earth element, and a and b each represent atomic percentages which satisfy the following Equations (1) and (2):0.1<a<99.9 (1)a+b=100 (2).