R-T-B Rare Earth Magnet Core-Shell Carbon Distribution for Coercivity
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Solution Overview
Problem
R-T-B-based rare earth magnets containing light rare earth elements face a reduction in residual magnetization and coercive force when carbon is added to enhance coercive force, as seen in existing technologies, leading to a compromise in performance.
Innovation Solution
The R-T-B-based rare earth magnet incorporates a main phase with an R2T14B-type crystal structure, a core-shell structure formed by diffusing a modifier containing neodymium, praseodymium, gadolinium, terbium, dysprosium, and holmium, with a higher carbon content in the grain boundary phase than in the main phase, and a controlled carbon content in the modifier to enhance coercive force while maintaining residual magnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If carbon is added in a relatively large amount to enhance coercive force, then coercive force is improved, but residual magnetization is reduced
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the shell portion has higher carbon content than the core portion. This localized carbon distribution enhances coercive force at the grain boundaries (where it is most needed) while minimizing carbon's negative impact on residual magnetization in the core. The shell portion acts as a carbon-rich interface layer that provides magnetic separation without excessively reducing overall residual magnetization.
Solution Approach 2:
The patent changes the carbon content parameter from a uniform distribution to a gradient distribution, with carbon content increasing from the core to the shell portion. Specifically, the carbon content in the shell portion is controlled at 0.05-5.0 at% while the core has lower carbon content. This parameter change allows optimization of coercive force enhancement while suppressing excessive reduction in residual magnetization.
2Quantity of substance
If part of Nd is substituted with light rare earth elements, then cost is reduced, but residual magnetization and coercive force are reduced
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the shell portion contains higher carbon content and potentially different rare earth element composition. This localized composition optimization allows light rare earth elements to be used in the core (reducing cost) while the shell provides the necessary coercive force enhancement through carbon enrichment and selective rare earth element distribution.
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 an enhancement of coercive force while minimizing the reduction in residual magnetization, achieving a better balance in magnetic properties for R-T-B-based rare earth magnets containing light rare earth elements.
Implementation Method 1
allowing a modifier to diffuse and penetrate into a rare earth magnet precursor
Data Source
AI summary
The R-T-B-based rare earth magnet 100 of the present disclosure includes a main phase 10 having an R2T14B-type crystal structure and a grain boundary phase 20. The average grain size of the main phase 10 is from 1.0 to 10,0 μm. The main phase 10 has a core portion 12 and a shell portion 14. The total content ratio of cerium, lanthanum, yttrium and scandium is higher in the core portion 12 than in the shell portion 14. The total content ratio of neodymium, praseodymium, gadolinium, terbium, dysprosium and holmium is higher in the shell portion 14 than in the core portion 12. The R-T-B-based rare earth magnet 100 contains from 0.05 to 0.50 at % of carbon. The content ratio of the carbon is higher in the grain boundary phase 20 than in the main phase 10.