NdFeB Grain Boundary Additive Deposition for Uniform Coercivity
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Solution Overview
Problem
Conventional methods for incorporating heavy rare earth elements into the grain boundaries of rare-earth magnets, such as grain boundary diffusion, result in localized concentrations at the surface, leading to inefficiencies and losses due to surface roughness and the need for post-processing removal of surface layers.
Innovation Solution
A method involving a jet mill system where inert gas is used to refine NdFeB particles, and these particles are impacted against a target material, transferring a portion of the target material onto the refined particles. This process ensures uniform distribution of additive domains within the magnet's grain boundaries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If grain boundary diffusion is used to incorporate heavy rare earth elements into the grain boundaries, then coercivity is improved, but the elements become localized predominantly at and near the surfaces of the magnets
Solution Approach 1:
The patent replaces the thermal diffusion process with a mechanical attrition process using a jet mill. Coarse NdFeB particles are milled and subjected to mechanical forces that cause heavy rare earth element particles to embed uniformly throughout the grain boundaries during the milling process, rather than diffusing thermally to the surface. This mechanical approach achieves uniform distribution while maintaining coercivity enhancement.
Solution Approach 2:
The patent changes the process parameters from high-temperature thermal diffusion to room-temperature or low-temperature mechanical milling. By changing the temperature parameter and the mechanism type, the heavy rare earth elements are distributed uniformly throughout the bulk material rather than concentrating at the surface, resolving the contradiction between coercivity enhancement and uniform distribution.
2Reliability
If grain boundary diffusion is used to incorporate heavy rare earth elements, then coercivity increases, but surface roughness increases requiring removal of surface layers
Solution Approach 1:
The patent replaces thermal diffusion with mechanical jet milling that inherently produces a smooth surface finish. The attrition process in the jet mill simultaneously refines particles and creates uniform surface conditions, eliminating the surface roughness problem associated with thermal diffusion while still achieving coercivity enhancement through uniform bulk distribution of heavy rare earth elements.
Solution Approach 2:
The patent extracts the harmful surface roughness effect by using a process that does not create it. Instead of applying heavy rare earth elements to the surface and then removing rough surface layers, the jet milling process incorporates elements uniformly throughout the bulk, eliminating the need for post-processing surface removal and simplifying manufacturing.
3Reliability
If heavy rare earth elements are applied to the surface by printing or sputtering, then coercivity is enhanced, but a significant portion of the applied elements is lost during surface layer removal
Solution Approach 1:
The patent replaces surface application methods (printing, sputtering) with mechanical jet milling that incorporates heavy rare earth elements uniformly throughout the bulk material. This eliminates the need for subsequent surface layer removal, preventing loss of the expensive heavy rare earth elements while still achieving coercivity enhancement through uniform distribution.
Solution Approach 2:
The patent performs the element incorporation action during the particle formation and refinement process itself, rather than as a subsequent surface treatment. By embedding heavy rare earth elements uniformly throughout the bulk during jet milling, the process prevents the need for later surface removal operations that would cause 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
The method achieves a uniform distribution of additive domains throughout the magnet volume, enhancing coercivity and reducing the need for post-processing steps, while minimizing the use of heavy rare earth elements.
Implementation Method 1
introducing inert gas into a chamber of a jet mill and forming an inert gas stream, introducing a plurality of coarse neodymium-iron-boron (NdFeB) particles into the chamber, agitating the plurality of coarse NdFeB particles with the inert gas stream
Implementation Method 2
impacting the plurality of coarse NdFeB particles with each other producing a plurality of refined NdFeB particles
Implementation Method 3
impacting the plurality of refined NdFeB particles against a target including a target material and transferring a portion of the target material onto a surface of the refined NdFeB particles
Data Source
AI summary
A method of incorporating additive domains in a rare earth magnet, a system for incorporating additive domains in a rare earth magnet, and a traction motor including a rare earth magnet. Inert gas and a plurality of coarse neodymium-iron-boron (NdFeB) particles are introduced into the chamber of a jet mill. The plurality of coarse NdFeB particles impact each other producing a plurality of refined NdFeB particles. The plurality of refined NdFeB particles also impact a target including a target material and transfer a portion of the target material onto a surface of the refined NdFeB particles. The plurality of refined NdFeB particles including the target material are separated from the plurality of coarse NdFeB particles and collected to form a rare earth magnet.