Nd-Fe-B Magnet Coating Reduces Dysprosium Usage
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Solution Overview
Problem
The high cost and scarcity of dysprosium (Dy) and terbium (Tb) rare-earth elements, used to enhance the magnetic properties of Nd—Fe—B permanent magnets, pose a significant challenge in producing compact, lightweight, and powerful motors for hybrid and electric vehicles, as conventional methods require high concentrations of these elements for uniform distribution within the magnets.
Innovation Solution
A method involving coating Nd—Fe—B alloy powders with Dy or Tb to achieve a non-uniform distribution, reducing the bulk concentration while maintaining high magnetic properties, by using mechanical milling, physical vapor deposition, or solvent-based coating techniques, allowing for a significant reduction in the amount of Dy or Tb used, typically by 20-90% compared to conventional methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Dy or Tb are added uniformly throughout the magnet to improve magnetic properties, then the anisotropic field and intrinsic coercivity increase, but the saturation magnetization decreases and the cost increases significantly
Solution Approach 1:
The patent applies local quality by concentrating Dy or Tb at the grain boundary regions rather than uniform distribution throughout the magnet. This localized placement at interfaces provides the necessary coercivity enhancement while minimizing the total amount of rare-earth elements required, thus reducing both cost and saturation magnetization loss.
Solution Approach 2:
The patent segments the magnet structure into distinct regions: Nd2Fe14B grains and grain boundary regions. By adding Dy or Tb specifically to the grain boundary regions through controlled processing, the patent achieves effective magnetic property improvement while reducing overall rare-earth content compared to uniform distribution.
2Temperature
If Co is added to raise the Curie temperature, then the thermal stability improves, but the coercivity decreases due to nucleation sites for reverse domains
Solution Approach 1:
The patent applies local quality by placing Dy or Tb specifically at the grain boundary regions rather than uniformly throughout the magnet. This localized placement at interfaces provides the necessary coercivity enhancement while minimizing the total amount of rare-earth elements required, thus reducing both cost and saturation magnetization loss.
3Reliability
If heavy RE elements are added to improve magnetic properties, then the anisotropic field increases, but the saturation magnetization decreases
Solution Approach 1:
The patent applies local quality by concentrating Dy or Tb at the grain boundary regions rather than uniform distribution throughout the magnet. This localized placement at interfaces provides the necessary coercivity enhancement while minimizing the total amount of rare-earth elements required, thus reducing both cost and saturation magnetization 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 approach enables the production of magnets with similar magnetic properties using substantially less Dy or Tb, optimizing the distribution of these elements at the surface of the powder particles, thereby reducing material costs and conserving rare-earth resources.
Implementation Method 1
coating the first alloy powder with dysprosium, dysprosium alloy, terbium, or terbium alloy
Implementation Method 2
mechanical milling
Implementation Method 3
solvent-based coating techniques
Implementation Method 4
the first alloy powder has a surface concentration of dysprosium, terbium, or both in excess of a bulk concentration of dysprosium, terbium, or both
Implementation Method 5
The addition of Dy or Pb leads to the formation of quite different ternary intergranular phases based on Fe, Nd and Dy or Tb. These phases are located in the grain boundary region and at the surface of the Fe14Nd2B grains.
Data Source
AI summary
A method of making a permanent magnet is described. In one embodiment, the method includes providing a first alloy powder having a desired composition, the alloy powder containing neodymium, iron, and boron; coating the first alloy powder with dysprosium, dysprosium alloy, terbium, or terbium alloy so that the first alloy powder has a surface concentration of dysprosium, terbium, or both in excess of a bulk concentration of dysprosium, terbium, or both; and forming the permanent magnet from the coated alloy powder using a powder metallurgy process, the permanent magnet having a non-uniform distribution of dysprosium, terbium, or both therein. Permanent magnets are also described.