R-T-B Magnet Coercivity via Surface RH Diffusion
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Solution Overview
Problem
Existing methods for improving the intrinsic coercivity (HcJ) of sintered R-T-B based magnets at high temperatures face challenges due to non-uniform distribution of heavy rare-earth elements, leading to inefficient use and waste of scarce resources.
Innovation Solution
A method involving the application of a particle size-adjusted powder containing a heavy rare-earth element, adhered to the magnet surface with an adhesive agent, followed by a diffusion heat treatment to ensure uniform distribution and efficient diffusion into the magnet, optimizing the mass ratio of the heavy rare-earth element within a range of 0.6 to 1.5% by mass ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy rare-earth element RH is profusely added to increase HcJ, then intrinsic coercivity HcJ increases, but remanence Br decreases and resource consumption increases
Solution Approach 1:
The invention applies local quality by concentrating heavy rare-earth element RH at the surface region of the magnet through selective surface treatment, rather than uniformly distributing it throughout the bulk material. This localized enrichment at the surface provides the necessary coercivity enhancement while minimizing overall RH content, thereby preserving remanence Br and reducing resource consumption.
Solution Approach 2:
The invention transitions from bulk modification to surface modification by applying RH-containing compounds as coatings on the magnet surface. This dimensional shift from three-dimensional bulk doping to two-dimensional surface treatment allows coercivity improvement with minimal RH addition, effectively decoupling HcJ enhancement from Br degradation.
2Reliability
If heavy rare-earth element RH is added to improve HcJ, then intrinsic coercivity increases, but resource availability decreases due to RH being rare natural resources
Solution Approach 1:
By localizing RH enrichment to the surface region where it most effectively influences magnetic domain wall pinning, the invention achieves maximum coercivity improvement per unit of RH consumed. This localized approach dramatically reduces overall RH consumption compared to bulk doping strategies.
Solution Approach 2:
The invention applies partial action by using only the minimum necessary amount of RH (0.1-5 mass%) concentrated at the surface, rather than requiring profuse addition throughout the bulk material. This partial enrichment at critical locations provides sufficient coercivity enhancement while conserving rare resources.
3Reliability
If conventional coating methods are used to apply RH compound on magnet surface, then heavy rare-earth element can be introduced, but uniform distribution is difficult to achieve leading to HcJ fluctuation
Solution Approach 1:
The invention introduces an intermediary carrier substance that uniformly distributes RH-containing compounds on the magnet surface. This intermediary medium ensures homogeneous RH distribution, eliminating the fluctuations in HcJ that result from non-uniform RH concentration in the surface region.
Solution Approach 2:
The invention achieves homogeneity by using a uniform coating process that distributes RH-containing compounds evenly across the entire magnet surface. This homogeneous distribution ensures consistent magnetic properties throughout the magnet, eliminating HcJ fluctuations caused by localized RH concentration variations.
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 allows for improved HcJ of sintered R-T-B based magnets while minimizing the use of heavy rare-earth elements, ensuring uniform application and reducing waste, thereby enhancing coercivity efficiently.
Implementation Method 1
a diffusing step of heating the sintered R-T-B based magnet having the particle size-adjusted powder adhering thereto at a temperature which is equal to or lower than a sintering temperature of the sintered R-T-B based magnet to allow the heavy rare-earth element RH contained in the particle size-adjusted powder to diffuse from the surface into the interior of the sintered R-T-B based magnet
Implementation Method 2
an application step of applying an adhesive agent to an application area of a surface of the sintered R-T-B based magnet; an adhesion step of allowing the particle size-adjusted powder to adhere to the application area of the surface of the sintered R-T-B based magnet having the adhesive agent applied thereto
Data Source
AI summary
A method for producing a sintered R-T-B based magnet includes applying an adhesive agent to an application area of the magnet, adhering a particle size-adjusted powder of a heavy rare-earth element RH which is at least one of Dy and Tb to the application area, and heating at a temperature which is equal to or lower than a sintering temperature of the magnet to allow the element RH in the particle size-adjusted powder to diffuse from the surface into the interior of the magnet. The particle size of the particle size-adjusted powder is set so that, when powder particles are placed on the entire surface of the magnet to form a single particle layer, the amount of element RH in the particle size-adjusted powder is in a range from 0.6 to 1.5% with respect to the magnet by mass ratio.