Rare Earth Sintered Magnet Coating for Stable Grain Boundary Diffusion
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Solution Overview
Problem
Existing methods for producing rare earth magnets through grain boundary diffusion face challenges such as difficulty in controlling coating variations, low diffusion efficiency, and process instability, particularly in achieving high productivity with improved magnetic properties.
Innovation Solution
The method involves depositing a coating of R-containing particles on a rare earth magnet body using a particle impingement phenomenon like aerosol deposition, which forces particles to impinge under differential pressure, resulting in a dense coating and improved magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sputtering method is used for grain boundary diffusion, then uniform coating and improved magnetic properties are achieved, but process complexity and manufacturing difficulty increase due to high vacuum requirements
Solution Approach 1:
The patent replaces the sputtering method (which requires high vacuum equipment and complex mechanical systems) with a spray drying method. The spray drying process uses a simple spray nozzle to deposit rare earth compound particles onto the magnet body surface, eliminating the need for vacuum equipment and complex mechanical mechanisms, thus reducing device complexity while achieving uniform coating.
Solution Approach 2:
The patent changes the deposition parameters from vacuum-based physical sputtering to atmospheric spray drying. By controlling spray conditions, particle size distribution, and drying parameters, the method achieves uniform coating without requiring high vacuum conditions, thereby simplifying the manufacturing process while maintaining coating quality.
2Ease of manufacture
If wet method with slurry is used for coating, then coating process is simple, but control of coating weight and thickness variations becomes difficult
Solution Approach 1:
The patent uses a spray drying method where a liquid slurry is sprayed and rapidly dried to form a coating. The liquid carrier evaporates completely, leaving only the rare earth compound particles on the magnet surface. This approach allows for easy process adjustment and good control over coating weight and thickness by controlling spray parameters, while the evaporated solvent is discarded, effectively using a disposable liquid carrier.
Solution Approach 2:
The patent implements control over coating weight and thickness by monitoring and adjusting spray parameters such as spray rate, drying temperature, and particle feed rate. This feedback control mechanism ensures consistent coating quality while maintaining the simplicity of the spray drying process, resolving the contradiction between ease of manufacture and manufacturing precision.
3Manufacturing precision
If pressure-sensitive adhesive is used to attach alloy powder, then powder distribution is uniform and effective, but process load and impurity introduction increase
Solution Approach 1:
The patent extracts and eliminates the pressure-sensitive adhesive step from the process. Instead of attaching alloy powder with adhesive and then heating, the method directly sprays rare earth compound particles that adhere to the magnet body surface through the spray drying process itself. This removes the unnecessary adhesive application step and reduces process load while maintaining uniform powder distribution.
Solution Approach 2:
The patent uses a liquid slurry as an intermediary carrier during the spray drying process. The slurry contains rare earth compound particles suspended in liquid, which is sprayed onto the magnet body and rapidly dried. The liquid acts as a temporary mediator that enables uniform particle distribution during deposition, then evaporates completely without leaving impurities, replacing the function of pressure-sensitive adhesive without its drawbacks.
4Manufacturing precision
If grain boundary diffusion efficiency is improved, then magnetic properties are enhanced, but process stability decreases
Solution Approach 1:
The patent optimizes multiple parameters of the spray drying process including particle size distribution, spray rate, drying temperature, and ambient conditions to achieve both high diffusion efficiency and process stability. By controlling these parameters within specific ranges, the method ensures consistent rare earth element diffusion into the magnet body while maintaining stable and repeatable process operation.
Solution Approach 2:
The patent uses dry rare earth compound particles as the diffusion source, which are sprayed and deposited onto the magnet body surface. This dry particle approach copies the beneficial effects of controlled particle deposition seen in other precision coating methods, achieving high diffusion efficiency through uniform particle distribution while maintaining process stability through the simplicity and controllability of the spray drying technique.
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 enables the production of rare earth sintered magnets with enhanced magnetic properties and high productivity, with the ability to recover unused particles and minimize process load, achieving consistent improvements in coercivity and productivity.
Implementation Method 1
depositing a coating of R-containing particles on a rare earth magnet body using a particle impingement phenomenon like aerosol deposition, which forces particles to impinge under differential pressure
Implementation Method 2
using a particle impingement phenomenon like aerosol deposition, which forces particles to impinge under differential pressure
Implementation Method 3
heat treating the magnet body for causing absorption and diffusion of R in the magnet body
Implementation Method 4
heat treating the magnet body for causing absorption and diffusion of R in the magnet body
Data Source
AI summary
A rare earth sintered magnet is produced by depositing a coating of rare earth-containing particles on the surface of a rare earth magnet body, and heat treating the magnet body for causing absorption and diffusion of rare earth element in the magnet body. The depositing step utilizes a particle impingement phenomenon.