R-T-B Sintered Magnet Grain Boundary Passivity
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Solution Overview
Problem
R-T-B based sintered magnets exhibit low corrosion resistance due to hydrogen generation at the grain boundary, leading to degradation and a decrease in magnetic properties, despite their excellent magnetic properties.
Innovation Solution
Incorporating an R—N—O—C concentrated part with specific atomic ratios of Y, N, and O at the grain boundary of R2T14B crystal grains, forming a passivity that prevents hydrogen storage and enhances corrosion resistance without compromising magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If R-T-B based sintered magnets are used for excellent magnetic properties, then magnetic performance is improved, but corrosion resistance deteriorates due to hydrogen generation at grain boundaries
Solution Approach 1:
The invention applies local quality by creating a specialized grain boundary phase with specific composition (R-N-O-C concentrated part with Y, N, O, and C) that differs from the main R2T14B crystal grains. This localized modification at the grain boundary provides corrosion protection without affecting the magnetic properties of the main phase, resolving the contradiction between magnetic performance and corrosion resistance
Solution Approach 2:
The invention uses composite materials by forming a multi-phase structure consisting of the main R2T14B crystal grains and a composite grain boundary phase containing R-N-O-C concentrated part. This composite structure combines the high magnetic properties of the R2T14B phase with the corrosion resistance of the grain boundary phase, achieving both excellent magnetic performance and corrosion protection
2Object-affected harmful factors
If grain boundary composition is modified to improve corrosion resistance, then hydrogen storage is prevented, but magnetic properties may decrease
Solution Approach 1:
The invention confines the compositional modification to the grain boundary region only, creating an R-N-O-C concentrated part with specific elements (Y, N, O, C) at the grain boundary while maintaining the bulk R2T14B crystal grain composition unchanged. This localized approach prevents hydrogen storage at grain boundaries without affecting the magnetic properties of the main phase
Solution Approach 2:
The invention applies parameter changes by precisely controlling the atomic ratios of elements in the grain boundary phase (Y atom ratio: 0.65-1.00, O atom ratio: 0.00-0.20, N atom ratio: 0.03-0.15). These parameter optimizations enable the grain boundary phase to provide corrosion protection while maintaining overall magnetic performance
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 R—N—O—C concentrated part effectively improves corrosion resistance while maintaining the magnetic properties of R-T-B based sintered magnets, ensuring their reliability in harsh environments.
Implementation Method 1
Y and N on the surface of the concentrated part are united, and a passivity is formed. It is thus conceivable that hydrogen storage into the grain boundary is prevented further than before and corrosion resistance can be improved further than before.
Data Source
AI summary
An R-T-B based sintered magnet includes R2T14B crystal grains. A grain boundary formed by the two or more adjacent R2T14B crystal grains includes an R—N—O—C concentrated part having higher concentrations of “R”, N, O, and C than those in the R2T14B crystal grains. “R” of the R—N—O—C concentrated part includes Y. A ratio of Y atom to “R” atom in the R—N—O—C concentrated part is 0.65 or more and 1.00 or less. A ratio of O atom to “R” atom in the R—N—O—C concentrated part is more than 0 and 0.20 or less. A ratio of N atom to “R” atom in the R—N—O—C concentrated part is 0.03 or more and 0.15 or less.