Core-Shell Rare Earth-Iron-Nitrogen Powder for Heat-Stable Bonded Magnets
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Solution Overview
Problem
Conventional rare earth-iron-nitrogen-based magnetic powders exhibit low heat resistance and magnetic properties deteriorate under high temperatures, limiting their use in applications requiring high thermal stability.
Innovation Solution
A rare earth-iron-nitrogen-based magnetic powder with a core-shell structure is developed, where the core has a Th 2 Zn 17 -, Th 2 Ni 17 -, or TbCu 7 -type crystal structure and is coated with a shell layer richer in rare earth elements, containing a phosphoric acid-derived compound, which enhances heat resistance and magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rare earth-iron-nitrogen-based magnetic powder is used to form bonded magnets, then high magnetic properties are achieved, but heat resistance is low and magnetic properties deteriorate at high temperatures
Solution Approach 1:
The patent creates a core-shell structured magnetic powder where the core contains rare earth-iron-nitrogen-based magnetic particles providing high magnetic properties, while the shell contains phosphoric acid-derived compounds providing heat resistance. This composite structure allows the magnetic powder to maintain both high magnetic properties and heat resistance simultaneously, resolving the contradiction between magnetic performance and thermal stability.
Solution Approach 2:
The patent applies different functional properties to different parts of the magnetic powder: the core region is optimized for magnetic properties with rare earth-iron-nitrogen-based compounds, while the shell region is optimized for heat resistance with phosphoric acid-derived compounds. This local differentiation allows each region to perform its specific function, enabling the overall material to achieve both high magnetic properties and heat resistance.
2Temperature
If iron is partially replaced by manganese to improve heat resistance and oxidation resistance, then thermal stability is enhanced, but magnetic properties may deteriorate
Solution Approach 1:
Instead of relying solely on manganese substitution to achieve heat resistance, the patent extracts the heat resistance function into a separate shell component made of phosphoric acid-derived compounds. This allows the core to maintain its iron-rich composition for optimal magnetic properties while the shell provides the necessary thermal stability, avoiding the need to compromise magnetic properties through iron replacement.
3Temperature
If an oxidation-resistant coating is formed on the surface of particles, then heat resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent combines the coating formation process with the existing magnetic powder production process. The phosphoric acid-derived compound coating is formed on the magnetic particles during the manufacturing process itself, rather than requiring a separate post-processing coating step. This integration reduces manufacturing complexity while still providing the necessary heat resistance.
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 magnetic powder maintains high coercive force and remanent magnetization even at elevated temperatures, making it suitable for forming bonded magnets in various applications.
Implementation Method 1
the magnetic powder with low heat resistance will provide low magnetic properties due to heating in the mixing and molding steps... Proposed solutions to these problems involve a technique for improving the heat resistance of the rare earth-iron-nitrogen-based magnetic powder, such as forming a rare earth-iron-nitrogen-based magnetic powder with iron (Fe) partially replaced by another element, reducing the content of fine powder, or forming an oxidation-resistant coating on the surface of the particles
Implementation Method 2
The magnetic powder maintains high coercive force and remanent magnetization even at elevated temperatures
Implementation Method 3
The reduction-diffusion method includes allowing a raw material including a rare earth oxide to undergo reduction and reaction with a metal such as iron to form magnetic particles
Implementation Method 4
The reduction-diffusion method includes allowing a raw material including a rare earth oxide to undergo reduction and reaction with a metal such as iron to form magnetic particles
Data Source
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AI summary
This invention pertains to: a rare earth-iron-nitrogen-based magnetic powder having excellent heat resistance and magnetic properties, and a method for producing the same; and a compound which is for a bonded magnet and contains a rare earth-iron-nitrogen-based magnetic powder, and a bonded magnet. A rare earth-iron-nitrogen-based magnetic powder according to this invention contains, as main constituent components, a rare-earth element (R), iron (Fe), and nitrogen (N). Moreover, this magnetic powder has an average particle size of 1.0-10.0 um, and contains 22.0-30.0 mass% of a rare-earth element (R) and 2.5-4.0 mass% of nitrogen (N). Further, this magnetic powder includes: a core part having any one crystal structure among a Th2Zn17 type, a Th2Ni17 type, and a TbCu7 type; and a shell layer provided on the surface of the core part and having a thickness of 1-30 nm. The shell layer contains a rare-earth element (R) and iron (Fe) so that the R/Fe atomic ratio is 0.3-5.0, and further contains 0-10 at% (exclusive of 0) of nitrogen (N). Furthermore, this magnetic powder contains compound particles composed of a rare-earth element (R) and phosphorus (P).