R-T-B Sintered Magnet Grain-Boundary Diffusion for Stable Coercivity
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Solution Overview
Problem
Existing methods for improving the coercivity (HcJ) of sintered R-T-B based magnets face challenges in achieving uniform distribution of heavy rare-earth elements, leading to fluctuating HcJ values and wastage of scarce resources due to non-uniform coating techniques.
Innovation Solution
A method involving a particle size-adjusted Pr—Ga alloy powder is applied to the surface of sintered R-T-B based magnets using an adhesive agent, allowing the powder to adhere uniformly and diffuse into the magnet, with controlled Ga content to enhance coercivity without excessive rare-earth element usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy rare-earth element RH is used to improve HcJ, then coercivity is improved, but remanence Br decreases and resource scarcity problems arise
Solution Approach 1:
The patent applies local quality by concentrating heavy rare-earth elements specifically at the grain boundaries of the magnet rather than uniformly distributing them throughout. This localized approach at critical interfaces maximizes the coercivity enhancement while minimizing the total amount of scarce heavy rare-earth materials required, thereby preserving remanence properties.
Solution Approach 2:
The patent employs parameter changes by controlling the particle size of heavy rare-earth element powders within a specific range (0.1-10 μm) and adjusting heat treatment parameters (temperature 400-900°C, time 0.1-48 hours). These parameter optimizations enable effective diffusion and distribution of heavy rare-earth elements at grain boundaries, achieving high coercivity with reduced material consumption.
2Reliability
If powder coating methods are used to apply heavy rare-earth elements, then HcJ improvement is achieved, but uniform distribution is difficult and HcJ fluctuates
Solution Approach 1:
The patent utilizes mechanical vibration during the coating process to enhance the uniformity of powder distribution on the magnet surface. The vibration facilitates even spreading of heavy rare-earth element particles and improves penetration into surface irregularities, resulting in more homogeneous elemental distribution and reduced HcJ fluctuation after heat treatment.
Solution Approach 2:
The patent introduces an intermediary binder material that facilitates uniform adhesion of heavy rare-earth element powder to the magnet surface. This binder acts as a mediator that ensures consistent coating thickness and distribution, which then uniformly diffuses into the magnet during heat treatment, achieving precise and stable HcJ improvement.
3Area of stationary object
If immersion or spray coating techniques are used, then entire surface coverage is achieved, but non-uniform coating thickness occurs due to gravity and surface tension
Solution Approach 1:
The patent applies mechanical vibration during the coating process to counteract the effects of gravity and surface tension that cause non-uniform thickness. The vibration energy promotes uniform powder distribution and consistent adhesion across the entire magnet surface, achieving both complete coverage and uniform thickness without the drawbacks of conventional immersion or spray methods.
4Reliability
If more heavy rare-earth element powder is applied to improve HcJ, then coercivity increases, but resource waste increases
Solution Approach 1:
The patent implements local quality by targeting heavy rare-earth element application specifically to grain boundary regions where they are most effective for coercivity enhancement. This localized approach ensures that scarce heavy rare-earth materials are concentrated where they provide maximum benefit, minimizing waste while achieving the desired HcJ improvement.
Solution Approach 2:
The patent replaces conventional mechanical coating methods with a combination of powder deposition and controlled heat treatment. This substitution enables precise control over element distribution and diffusion, ensuring that heavy rare-earth elements are efficiently utilized and incorporated into the magnet structure, reducing material waste while maintaining high coercivity.
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 uniform application and significant improvement in coercivity (HcJ) while minimizing the use of heavy rare-earth elements, ensuring efficient production and high magnetic performance.
Implementation Method 1
a heat treatment step of heating the sintered R-T-B based magnet work 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 work
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 work; 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 work having the adhesive agent applied thereto
Data Source
AI summary
An application step of applying an adhesive agent to an application area of a surface of a sintered R-T-B based magnet work, an adhesion step of allowing a particle size-adjusted powder that is composed of a powder of an alloy or a compound of a Pr—Ga alloy which is at least one of Dy and Tb to the application area of the surface of the sintered R-T-B based magnet work, and a diffusing step of heating it at a temperature which is equal to or lower than a sintering temperature of the sintered R-T-B based magnet work to allow the Pr—Ga alloy contained in the particle size-adjusted powder to diffuse from the surface into the interior of the sintered R-T-B based magnet work are included. The particle size of the particle size-adjusted powder is set so that, when powder particles composing the particle size-adjusted powder are placed on the entire surface of the sintered R-T-B based magnet work to form a particle layer which is not less than one layer and not more than three layers, the amount of Ga contained in the particle size-adjusted powder is in a range from 0.10 to 1.0% with respect to the sintered R-T-B based magnet work by mass ratio.