Iron Core Material with Nitrogen-Deficient Fe-N Crystal Structure
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Solution Overview
Problem
Current iron nitride α″-Fe16N2 magnetic materials fail to achieve high saturation magnetic flux density Bs comparable to theoretically calculated values, necessitating a method to enhance Bs while maintaining low iron loss Pi for applications like rotating electric machines.
Innovation Solution
Introducing nitrogen defects into the body-centered tetragonal (bct) crystal structure of α″-Fe16N2, altering the molar ratio of iron to nitrogen beyond 8, which increases the magnetic moment and saturation magnetic flux density by optimizing the crystal structure and chemical composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If iron nitride α″-Fe16N2 is used to achieve high saturation magnetic flux density, then Bs increases compared to pure iron, but the actual Bs is lower than theoretically calculated values and cannot reach expected performance levels
Solution Approach 1:
The patent changes the chemical composition parameter by adjusting the Fe:N molar ratio to exceed 8 (higher iron content than conventional Fe16N2), and modifies the crystal structure parameters through controlled nitrogen deficiency. This parameter optimization enables achieving saturation magnetic flux density exceeding 2.4 T, resolving the contradiction between theoretical and actual performance
Solution Approach 2:
The patent introduces localized nitrogen defects specifically at the 2a sites in the bct crystal structure, creating regions with optimized magnetic properties. This localized modification allows certain crystal regions to contribute more effectively to saturation magnetization while maintaining overall structural stability
2Strength
If iron-cobalt-based alloy is used to achieve high saturation magnetic flux density, then Bs reaches 2.3 T, but manufacturing cost increases due to expensive cobalt material
Solution Approach 1:
The patent replaces expensive cobalt with abundant iron and nitrogen materials. By using cheap iron-based materials with optimized composition (Fe:N molar ratio > 8) and controlled nitrogen deficiency, the invention achieves Bs > 2.4 T at significantly lower material cost than iron-cobalt alloys
Solution Approach 2:
The patent creates a composite-like structure within the bct crystal phase by combining iron-rich regions with controlled nitrogen deficiency. This internal composition optimization achieves high magnetic performance without requiring expensive alloying elements
3Strength
If nitrogen content is increased to form α″-Fe16N2 structure, then saturation magnetic flux density improves, but thermal stability decreases making crystal growth difficult
Solution Approach 1:
The patent applies partial nitrogen incorporation rather than full stoichiometric Fe16N2 composition. By intentionally creating nitrogen deficiency (Fe:N molar ratio > 8), the material achieves optimal balance between magnetic performance and thermal stability, avoiding the excessive nitrogen content that causes poor thermal stability
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 approach results in a higher saturation magnetic flux density and improved magnetic characteristics, enhancing the performance of iron cores and rotating electric machines while maintaining cost-effectiveness.
Implementation Method 1
α″-Fe16N2 is an iron-based martensite having a body-centered tetragonal (bct) structure, and has a crystal structure where N penetrates into α-Fe such that the lattice spacing is expanded in a c-axis direction
Implementation Method 2
a rotating electric machine including an iron core where soft magnetic steel sheets are stacked
Data Source
AI summary
A magnetic material includes body-centered tetragonal (bct) crystal including iron and nitrogen, in which a molar ratio of iron to nitrogen in the crystal exceeds 8. An iron core includes soft magnetic steel sheets stacked together, in which a part or the entirety of the soft magnetic steel sheets is formed of the magnetic material which includes body-centered tetragonal (bct) crystal including iron and nitrogen and has a molar ratio of iron to nitrogen in the crystal exceeds 8. A rotating electric machine includes an iron core including soft magnetic steel sheets stacked together, in which a part or the entirety of the soft magnetic steel sheets is formed of the magnetic material which includes body-centered tetragonal (bct) crystal including iron and nitrogen and has a molar ratio of iron to nitrogen in the crystal exceeds 8.