Nd-Fe-B Magnet Coercivity via Grain Boundary Diffusion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Sintered Nd—Fe—B permanent magnets face challenges in maintaining coercivity under high temperature and high speed conditions, with traditional methods involving heavy rare earth elements leading to decreased remanence and inefficient utilization, along with environmental pollution and inconsistent magnetic properties due to the use of organic solvents.
Innovation Solution
A method involving the deposition of a heavy rare earth powder on sintered Nd—Fe—B magnet blocks using an organic adhesive layer under an inert gas environment, followed by diffusion and aging in a vacuum or inert gas environment, which controls the particle size and content of the rare earth elements to enhance coercivity while minimizing the use of organic solvents and impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heavy rare earth elements (Dy or Tb) are introduced into the main phase crystal grains to increase coercivity, then coercivity is improved, but remanence decreases
Solution Approach 1:
The patent applies local quality by introducing heavy rare earth elements only into the grain boundary phase rather than the main phase crystal grains. This localized approach allows the heavy rare earth elements to enhance coercivity through the grain boundary diffusion mechanism while preserving the magnetic properties of the main phase, thereby avoiding the reduction in remanence that would occur with bulk incorporation.
Solution Approach 2:
The grain boundary phase serves as an intermediary medium that facilitates the beneficial effects of heavy rare earth elements without directly incorporating them into the main phase. The heavy rare earth elements diffuse through this intermediate grain boundary phase, which mediates the interaction between the main phase grains and enables coercivity enhancement while maintaining remanence.
2Ease of manufacture
If traditional diffusion methods with organic solvents are used to apply heavy rare earth powder, then the powder can be applied to the magnet surface, but environmental pollution increases and magnetic properties become inconsistent
Solution Approach 1:
The patent extracts and eliminates the organic solvent component from the traditional slurry application process. By using a dry powder application method where heavy rare earth powder is directly applied to the magnet surface without organic solvent binding, the method removes the source of environmental pollution while maintaining effective powder adhesion and diffusion.
Solution Approach 2:
The patent replaces the reusable but polluting organic solvent system with a disposable-free dry powder approach. The heavy rare earth powder is applied directly and diffused without requiring solvent encapsulation, eliminating the need for solvent disposal and reducing environmental impact.
3Ease of manufacture
If traditional diffusion methods with organic solvents are used, then powder can be applied to the magnet surface, but the ratio of heavy rare earth elements changes over time resulting in excessive variation in magnetic properties
Solution Approach 1:
The patent extracts the organic solvent from the application process, eliminating the mechanism that causes composition changes over time. By applying heavy rare earth powder directly without solvent encapsulation, the method ensures stable and consistent powder composition during application and diffusion, leading to uniform magnetic properties across batches.
4Strength
If heavy rare earth elements are introduced into the main phase crystal grains, then coercivity increases, but the utilization rate of heavy rare earth elements decreases
Solution Approach 1:
The patent applies local quality by concentrating heavy rare earth elements specifically in the grain boundary phase rather than distributing them throughout the main phase crystal grains. This localized concentration achieves effective coercivity enhancement with lower overall heavy rare earth content, thereby improving the utilization rate and reducing material loss.
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 increases coercivity while maintaining remanence and reducing environmental impact by precise control of heavy rare earth content and minimizing solvent usage, resulting in consistent magnetic properties and improved production quality.
Implementation Method 1
the powder is diffused into the sintered Nd—Fe—B magnet block under a vacuum environment or an inert gas environment to produce a diffused magnet block
Implementation Method 2
depositing an organic adhesive layer on one of the block surfaces of the sintered Nd—Fe—B magnet block
Implementation Method 3
the diffused magnet block is aged under the vacuum environment or the inert gas environment
Data Source
AI summary
A method of increasing coercivity of a sintered Nd—Fe—B permanent magnet includes a first step of providing a sintered Nd—Fe—B magnet block having a pair of block surfaces extending perpendicular to a magnetization direction. The method then proceeds with depositing an organic adhesive layer on one of the block surfaces. Next, the method proceeds with depositing a powder containing at least one heavy rare earth element on the organic adhesive layer. After depositing the powder, the sintered Nd—Fe—B magnet block is pressed to adhere the powder to the organic adhesive layer. Then, the method follows with a step of removing excess powder from the sintered Nd—Fe—B magnet block to form a uniform film. Then, the powder is diffused into the sintered Nd—Fe—B magnet is diffused into the sintered Nd—Fe—B magnet block to produce a diffused magnet block. Next, the method proceeds with aging the diffused magnet block.