Sintered NdFeB Magnet Coercivity via Rare Earth Hydride Diffusion
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Solution Overview
Problem
Current methods for improving the coercivity of sintered NdFeB magnets using heavy rare earth hydride coatings face challenges such as high activity leading to oxidation and explosion risks, low utilization rates, and high production costs, while also compromising remanence and product consistency.
Innovation Solution
A method involving a finish coat of a material containing rare earth elements (R), hydrogen (H), and additional elements (X) such as C, O, N, S, B, Cl, or Si, applied through a dehydrogenation and diffusion treatment process in a vacuum or inert gas environment, which enhances coercivity and stability, allowing for uniform distribution and improved magnetic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heavy rare earth hydride powder is used as coating material for grain boundary diffusion, then coercivity can be improved, but the high activity of the powder leads to oxidation and explosion risks
Solution Approach 1:
The patent uses an intermediary substance (protective coating or inert atmosphere) to mediate between the heavy rare earth hydride powder and oxygen, preventing direct contact and reaction. This allows the powder to maintain its high coercivity-enhancing properties while eliminating the oxidation and explosion hazards through the protective intermediary layer.
Solution Approach 2:
The patent creates an inert environment during the coating and heat treatment processes by using protective atmospheres (such as nitrogen or argon) that prevent oxygen from contacting the reactive heavy rare earth hydride powder. This inert environment maintains safety while allowing the diffusion process to proceed effectively for improving coercivity.
2Strength
If traditional high-coercivity magnet processes are used, then coercivity can be improved, but production cost increases due to high heavy rare earth content
Solution Approach 1:
The patent applies partial action by using a thin surface layer of heavy rare earth hydride for diffusion rather than incorporating large amounts of heavy rare earth elements throughout the bulk magnet. This partial application achieves the necessary coercivity improvement while significantly reducing the total quantity of expensive heavy rare earth materials required, thereby lowering production costs.
Solution Approach 2:
The patent changes the parameter of heavy rare earth distribution from uniform bulk addition to concentrated surface diffusion. This parameter change allows achieving high coercivity with much lower overall heavy rare earth content, transforming the cost structure by reducing material consumption while maintaining or improving magnetic performance.
3Strength
If elementary rare earth is used as finish coat, then diffusion can occur, but oxidation resistance is poor making production difficult
Solution Approach 1:
The patent employs an inert atmosphere during the coating application and subsequent heat treatment processes to protect the elementary rare earth powder from oxidation. This controlled inert environment allows the diffusion process to proceed effectively while preventing oxidation issues that would complicate production.
Solution Approach 2:
The patent performs preliminary protective actions by applying the elementary rare earth coating in a controlled manner and immediately proceeding with heat treatment in a protected atmosphere. This preliminary preparation and rapid processing prevent oxidation before it can occur, ensuring both diffusion capability and ease of manufacture.
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 achieves significant improvement in coercivity and remanence, ensuring high product consistency, safety, and cost-effectiveness, with enhanced recycling and utilization of rare earth elements, while maintaining the stability of the magnet's performance.
Implementation Method 1
rare earth hydride has higher oxidation resistance, which can generate elementary metal and hydrogen gas through dehydrogenation at certain temperature
Implementation Method 2
use heat treatment process to ensure diffusion of heavy rare earth elements as contained in the finish coat of the magnet into the magnet along the grain boundary of the magnet
Implementation Method 3
proceed with diffusion and aging treatment to the sintered NdFeB magnet with finish coat in the environment of vacuum or inert gas
Data Source
AI summary
A method for improvement of magnetic performance of sintered NdFeB magnet includes the following steps. Firstly, material containing element R, H and X is to be covered on a surface of the sintered NdFeB magnet to form a finish coat. After that, proceed with a diffusion treatment and an aging treatment to the sintered NdFeB magnet with the finish coat in the environment of vacuum or inert gas. R is at least one of such elements as Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. H is hydrogen. X is at least one of such elements as C, O, N, S, B, Cl and Si.