Fe16N2 Magnetic Particles Production via Hydrogen Reduction and Nitridation
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Solution Overview
Problem
Current methods for producing α″-Fe16N2 magnetic materials face challenges in achieving high purity and stability, leading to unsuitable properties for extensive applications, particularly in hard magnetic materials requiring high maximum energy product BHmax, and are hindered by productivity and economic issues.
Innovation Solution
Ferromagnetic particles with an Fe16N2 compound phase of at least 80% and a thin FeO outer shell, produced through a process involving hydrogen reducing treatment and nitridation, achieving a coercive force of not less than 1.5 kOe and saturation magnetization of 150 emu/g, with controlled FeO volume fraction and nitridation rate, enabling the creation of anisotropic, bonded, and compacted magnets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods (vapor deposition, MBE, ion implantation, sputtering, ammonia nitridation) are used to produce α″-Fe16N2, then a single phase can be obtained, but the production is accompanied by eutectic crystal of martensite or ferrite which causes difficulty in producing pure α″-Fe16N2 in isolated state
Solution Approach 1:
The invention changes the chemical composition parameters by adding specific elements (Ti, V, Cr, Mn, Mo, Co, Ni, Cu, Al, Si, B) to the Fe-N system. These compositional modifications alter the phase formation behavior during nitridation, enabling the production of pure α″-Fe16N2 single phase particles without eutectic martensite or ferrite, thus resolving the contradiction between phase purity and manufacturing ease
Solution Approach 2:
The invention creates composite Fe-N-based compounds with additional elements (Ti, V, Cr, Mn, Mo, Co, Ni, Cu, Al, Si, B) added to the Fe16N2 structure. These composite materials modify the crystallization behavior and phase stability, allowing isolated α″-Fe16N2 single phase particles to be produced without the harmful eutectic phases that plague conventional methods
2Manufacturing precision
If α″-Fe16N2 is produced as thin film, then single phase can be achieved, but the application range is limited and unsuitable for extensive application fields
Solution Approach 1:
The invention changes the physical form parameter from thin film to isolated particles through compositional modifications and controlled nitridation. The addition of specific elements and optimization of nitridation conditions enable the formation of discrete, isolated α″-Fe16N2 particles that can be freely dispersed and applied in various configurations, thus expanding adaptability while maintaining single phase purity
Solution Approach 2:
The invention creates particle-form α″-Fe16N2 that replicates the beneficial single phase characteristics of thin films but in a versatile particle format. The compositional additives enable the particle structure to copy the phase purity achievement of thin films while providing the manufacturing and application advantages of particulate materials
3Reliability
If Fe-N-based compounds are used instead of Nd-Fe-B, then rare earth element dependency is reduced, but the magnetic properties and productivity are insufficient
Solution Approach 1:
The invention optimizes multiple parameters simultaneously: lowering nitridation temperature to 150-250°C, controlling nitridation time to 1-24 hours, and adding specific elements (Ti, V, Cr, Mn, Mo, Co, Ni, Cu, Al, Si, B). These parameter changes dramatically improve productivity by enabling rapid nitridation while enhancing magnetic properties through compositional optimization, thus making Fe-N-based compounds competitive with rare earth magnets
Solution Approach 2:
The invention develops composite Fe-N-based compounds with multiple element additions that synergistically improve both magnetic properties and production efficiency. The composite structure with elements like Co, Ni, and Mo enhances saturation magnetization and coercivity, while the overall compositional design enables faster nitridation kinetics, resolving the contradiction between supply security and productivity
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 process yields stable, high-purity Fe16N2 particles suitable for hard magnetic applications, enhancing magnetic properties and industrial viability by optimizing the Fe16N2/FeO structure and production conditions.
Implementation Method 1
subjecting iron oxide or iron oxyhydroxide to hydrogen reducing treatment
Implementation Method 2
subjecting the resulting particles to nitridation treatment
Data Source
AI summary
Ferromagnetic particles including an Fe16N2 compound phase in an amount of not less than 80% as measured by Mössbauer spectrum and each having an outer shell in which FeO is present in the form of a film having a thickness of not more than 5 nm. Ferromagnetic particles may be made by subjecting iron oxide or iron oxyhydroxide having an average major axis diameter of 40 to 5000 nm and an aspect ratio (major axis diameter/minor axis diameter) of 1 to 200 as a starting material to dispersing treatment to prepare aggregated particles; subjecting the iron compound particles passed through a mesh to hydrogen reducing treatment at a temperature of 160 to 420° C.; and then subjecting the resulting particles to nitridation treatment at a temperature of 130 to 170° C.