Porous Iron-Nitride Magnet Processing for High Fe16N2 Phase
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The development of bulk iron-nitride materials with a polycrystalline microstructure that can replace rare-earth-based permanent magnets is hindered by the difficulty in achieving high energy product and coercivity without using rare-earth elements, and existing methods for producing bulk iron-nitride materials are inefficient and environmentally impactful.
Innovation Solution
A method involving the production of bulk iron-nitride materials with a polycrystalline microstructure, including a Fe16N2 phase, through processes such as melting, fast belt casting, annealing, and nitriding, which control grain size and composition to achieve high coercivity and saturation magnetization, and incorporate non-magnetic elements at grain boundaries to enhance magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high temperature nitriding is used to form α′′-Fe16N2, then the Fe16N2 phase can be obtained, but the Fe16N2 phase ratio remains less than 50% and the process is energy-intensive
Solution Approach 1:
The patent changes the temperature parameter from conventional high temperature (above 590°C) to low temperature (below 200°C) nitriding process. This parameter change enables direct formation of α′′-Fe16N2 phase with phase ratio exceeding 50%, eliminating the need for high temperature processing while achieving superior phase composition.
Solution Approach 2:
The patent uses inexpensive iron-based materials (such as iron powder, iron foil, or iron scraps) as raw materials instead of expensive rare-earth elements. The low temperature nitriding process converts these cheap materials directly into high-value α′′-Fe16N2 permanent magnets, achieving both cost reduction and high phase ratio.
2Manufacturing precision
If low temperature nitriding is used to directly prepare α′′-Fe16N2, then single phase α′′-Fe16N2 can be obtained, but only nanoparticles can be used as raw material
Solution Approach 1:
The patent changes the particle size parameter from nanoscale to macroscopic scale. By combining low temperature nitriding with novel processing techniques, the patent enables direct formation of α′′-Fe16N2 from bulk iron materials (powder, foil, or scraps) without requiring nanoparticle precursors, thus achieving both phase purity and raw material versatility.
Solution Approach 2:
The patent segments the nitriding process into controlled stages that enable thorough nitrogen diffusion into bulk iron materials. This segmentation allows the process to work with various forms of iron (powder, foil, scraps) by adapting treatment time and atmosphere parameters, achieving complete phase transformation to α′′-Fe16N2.
3Ease of manufacture
If conventional thermomechanical processing is applied to bulk iron materials, then intermediate or final products can be produced, but the necessary processing for bulk iron-nitride materials has not been established
Solution Approach 1:
The patent applies preliminary low temperature nitriding treatment to bulk iron materials before final forming operations. This preliminary action creates a nitrided surface layer or transforms the bulk phase structure, enabling subsequent thermomechanical processing to produce bulk iron-nitride permanent magnets with controlled microstructure and desired geometry.
Solution Approach 2:
The patent creates composite microstructures by combining nitrided iron phases with controlled grain boundaries and secondary phases. The low temperature nitriding process produces a composite-like microstructure with α′′-Fe16N2 phase distributed throughout the bulk material, enabling both ease of manufacture and microstructure control.
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 results in bulk iron-nitride materials with high energy product, coercivity, and saturation magnetization, reducing the need for rare-earth elements and minimizing environmental impact, while also controlling grain size and composition to optimize magnetic properties.
Implementation Method 1
nitriding is applied to Fe. The Fe-nitriding is usually carried out at a high temperature above 590° C. with ammonia and hydrogen gas to form γ-FeN
Implementation Method 2
The Fe-nitriding is usually carried out at a high temperature above 590° C. with ammonia and hydrogen gas to form γ-FeN
Implementation Method 3
annealing the bulk iron-containing material at an austenite transformation temperature and subsequently cooling the bulk iron-containing material
Implementation Method 4
fast belt casting the molten iron source to obtain a cast iron source
Implementation Method 5
annealing the bulk iron-containing material at an austenite transformation temperature
Data Source
AI summary
In general, the disclosure is directed to bulk iron-nitride materials having a polycrystalline microstructure having pores including a plurality of crystallographic grains surrounded by grain boundaries, where at least one crystallographic grain includes an iron-nitride phase including any of a body centered cubic (bcc) structure, a body centered tetragonal (bct), and a martensite structure. The disclosure further describes techniques producing a bulk iron-nitride material having a polycrystalline microstructure, including: melting an iron source to obtain a molten iron source; fast belt casting the molten iron source to obtain a cast iron source; cooling and shaping the cast iron source to obtain a bulk iron-containing material having a body-centered cubic (bcc) structure; annealing the bulk iron-containing material at an austenite transformation temperature and subsequently cooling the bulk iron-containing material; and nitriding the bulk iron-containing material to obtain the bulk iron-nitride material.