Ordered Martensitic Iron Nitride Magnet Process

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Solution Overview

Problem

Current methods fail to achieve 100% transformation to single-phase α″-Fe16N2, a material with outstanding magnetic properties, due to nitrogen availability limitations in traditional diffusion techniques, especially when processing bulk powders or thin films.

Innovation Solution

A process involving fabricating an iron alloy powder, nitriding it in a fluidized bed reactor, transforming the nitride powder through high energy ball milling and annealing to achieve an ordered martensitic iron nitride powder without rare earth elements, expanding nitrogen solubility beyond equilibrium concentrations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If traditional diffusion techniques are used to process bulk powders or thin films, then the processing is simpler and more conventional, but nitrogen availability is limited by equilibrium thermodynamics preventing 100% transformation to single-phase α″-Fe16N2

Engineering Contradiction:

Improvetransformation to single-phase α″-Fe16N2VSAvoidnitrogen availability

Core Design Contradiction:

Manufacturing precisionVSQuantity of substance

Solution Approach 1:

The patent applies parameter changes by modifying the chemical potential of nitrogen through the use of a magnesium nitride layer and ammonia atmosphere. This shifts the nitrogen chemical potential above the equilibrium limit, enabling supersaturated nitrogen incorporation into the iron nitride phase and achieving 100% transformation to single-phase α″-Fe16N2 that cannot be obtained through conventional diffusion processes.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses magnesium nitride (Mg3N2) as an intermediary substance that serves as a nitrogen reservoir. The magnesium nitride layer decomposes to provide nitrogen to the iron powder, effectively mediating the nitrogen transfer process and overcoming the equilibrium thermodynamic limitations of direct diffusion methods.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If sputtering or evaporation in nitrogen-supersaturated environment is used, then 100% transformation to single-phase α″-Fe16N2 is achieved, but the process complexity and equipment requirements increase significantly

Engineering Contradiction:

Improvetransformation to single-phase α″-Fe16N2VSAvoidprocessing equipment complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent employs a disposable magnesium nitride layer that is applied to the iron powder surface and then consumed during the nitriding process. This sacrificial nitrogen source provides supersaturated nitrogen without requiring complex sputtering or evaporation equipment, achieving the desired phase transformation through a simpler, more cost-effective method.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent replaces the mechanical/physical processes of sputtering and evaporation with a chemical process involving magnesium nitride decomposition and ammonia atmosphere treatment. This substitution eliminates the need for complex vacuum equipment and ion bombardment systems while achieving the same nitrogen supersaturation effect.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Strength

If rare earth elements are used to create strong permanent magnets, then magnetic performance is improved, but cost increases and supply becomes limited

Engineering Contradiction:

Improvemagnetic performanceVSAvoidrare earth element availability

Core Design Contradiction:

StrengthVSQuantity of substance

Solution Approach 1:

The patent extracts and eliminates rare earth elements from the magnet composition by developing an iron-based nitride system (α″-Fe16N2) that achieves comparable magnetic performance. Through controlled nitriding processes using magnesium nitride and ammonia, the patent creates high-performance magnets without dependence on scarce rare earth materials like neodymium or samarium.

Inventive Principle:

Principle #2Taking out (Extraction)

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

This process enables the production of high-performance, low-density ordered martensitic iron nitride powder suitable for permanent magnet applications, overcoming the limitations of traditional techniques and eliminating the need for rare earth elements.

Implementation Method 1

nitriding the iron alloy powder by contacting the material with a nitrogen source in a fluidized bed reactor to produce a nitride iron powder

Methodology Applied

Scientific EffectNitriding: Nitriding

Implementation Method 2

annealing the disordered martensitic phase to an ordered martensitic phase

Methodology Applied

Scientific EffectAnnealing: Annealing

Data Source

PatentUS9997285B2Transformation enabled nitride magnets absent rare earths and a process of making the same

Publication Date: 2018.06.12 CASE WESTERN RESERVE UNIV

AI summary

A process for producing an ordered martensitic iron nitride powder that is suitable for use as a permanent magnetic material is provided. The process includes fabricating an iron alloy powder having a desired composition and uniformity; nitriding the iron alloy powder by contacting the material with a nitrogen source in a fluidized bed reactor to produce a nitride iron powder; transforming the nitride iron powder to a disordered martensitic phase; annealing the disordered martensitic phase to an ordered martensitic phase; and separating the ordered martensitic phase from the iron nitride powder to yield an ordered martensitic iron nitride powder.