NdFeB Magnet Coercive Force via DyTb Fluoride Vapor Diffusion
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Solution Overview
Problem
Nd—Fe—B sintered magnets face issues with high temperature demagnetization and fabrication defects leading to reduced magnetic properties, and the use of Dy and/or Tb to enhance coercive force is costly and inefficient due to expensive raw materials and low supply stability.
Innovation Solution
A method involving the evaporation of fluoride materials containing Dy and/or Tb, which are diffused into the grain boundary phase of Nd—Fe—B sintered magnets using vacuum vapor processing, allowing for improved coercive force and magnetic properties while reducing manufacturing costs through the use of low-cost intermediate products and optimizing diffusion velocity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Dy and/or Tb are added to improve coercive force, then magnetic properties are improved, but manufacturing cost increases due to expensive raw materials
Solution Approach 1:
The patent changes the chemical form of Dy/Tb from metal to fluoride compound, which enables lower temperature processing and more efficient diffusion into the grain boundary phase, thereby reducing the total amount of Dy/Tb needed while maintaining coercive force improvement
Solution Approach 2:
The patent replaces conventional mechanical mixing or surface coating methods with vacuum vapor deposition, allowing precise control of Dy/Tb fluoride distribution and diffusion depth, which improves manufacturing efficiency and reduces material waste
2Strength
If Dy and/or Tb are added to enhance grain magnetic anisotropy, then coercive force is improved, but maximum energy product is reduced due to ferrimagnetism structure
Solution Approach 1:
The patent applies Dy/Tb fluoride specifically to the grain boundary phase rather than uniformly throughout the magnet, creating local magnetic anisotropy enhancement at grain boundaries while preserving the ferromagnetic structure and high energy product of the principal phase
Solution Approach 2:
The patent uses fluoride compounds as intermediaries that facilitate controlled diffusion of Dy/Tb into the grain boundary phase, enabling precise spatial distribution that optimizes coercive force without adversely affecting the maximum energy product
3Strength
If film thickness of Dy and/or Tb is increased to improve coercive force, then magnetic properties are improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent replaces multi-step film formation processes with vacuum vapor deposition, which achieves uniform and controlled distribution of Dy/Tb fluoride in a single step, simplifying the manufacturing process while ensuring optimal diffusion characteristics
4Adaptability or versatility
If sintered magnet is fabricated into predetermined shape, then product requirements are met, but defects and strains occur leading to deterioration of magnetic properties
Solution Approach 1:
The patent applies Dy/Tb fluoride to the sintered magnet surface before final shaping operations, so that the grain boundary phase is pre-strengthened against the strains and defects that will occur during subsequent fabrication processes, thereby maintaining magnetic properties
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
The method achieves a permanent magnet with significantly higher coercive force and magnetic properties at lower costs and improved productivity, maintaining high magnetic performance even when the magnets are cut into thin pieces without deteriorating their properties.
Implementation Method 1
evaporating an evaporating material comprising a fluoride containing at least one of Dy and Tb
Implementation Method 2
diffusing metal atoms of at least one of Dy and Tb of the adhered evaporating material into grain boundary phase of the sintered magnet
Data Source
AI summary
By causing at least one of Dy and Tb to be adhered to the surface of an iron-boron-rare earth based sintered magnet of a predetermined shape, and is then to be diffused into grain boundary phase, a permanent magnet can be manufactured at high workability and low cost. An iron-boron-rare earth based sintered magnet is disposed in a processing chamber and is heated to a predetermined temperature. Also, an evaporating material made up of a fluoride containing at least one of Dy and Tb disposed in the same or another processing chamber is evaporated, and the evaporated evaporating material is caused to be adhered to the surface of the sintered magnet. The Dy and/or Tb metal atoms of the adhered evaporating material are diffused into the grain particle phase of the sintered magnet before a thin film made of the evaporated material is formed on the surface of the sintered magnet.