Ce-Based Permanent Magnet Valence Control
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Solution Overview
Problem
Rare earth permanent magnets with high magnetic anisotropy and corrosion resistance are needed, as existing Ce-T-B based magnets lack sufficient magnetic properties and are prone to corrosion due to hydrogen content.
Innovation Solution
A rare earth permanent magnet with a composition that includes main phase grains having a specific ratio of trivalent to tetravalent Ce atoms, utilizing crystal structures like Nd2Fe14B, TbCu7, and ThMn12, and incorporating elements like Co and interstitial elements to achieve high magnetic anisotropy and coercivity while maintaining corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Ce-T-B based permanent magnets are used to replace rare earth elements, then resource abundance and cost are improved, but magnetic properties and corrosion resistance deteriorate
Solution Approach 1:
The invention changes the oxidation state parameter of Ce from the conventional tetravalent state to a mixed valence state (combination of trivalent and tetravalent Ce). This parameter change fundamentally alters the magnetic properties and corrosion resistance of the Ce-T-B magnet, enabling it to achieve both high magnetic performance and good corrosion resistance simultaneously
Solution Approach 2:
The invention creates a composite magnetic material system where Ce exists in multiple oxidation states (trivalent and tetravalent) within the same crystal structure. This composite approach at the atomic level allows the material to combine the advantages of different Ce valence states, achieving both high coercivity and corrosion resistance
2Strength
If hydrogen is added to Ce-T-B magnets to promote volume expansion, then coercivity is improved, but corrosion resistance deteriorates
Solution Approach 1:
The invention changes the chemical composition parameter by introducing a specific ratio of trivalent Ce (C3) to achieve high coercivity without hydrogen, thereby eliminating the corrosion problem associated with hydrogen-containing magnets while maintaining the volume expansion effect needed for high coercivity
3Quantity of substance
If Fe concentration in the main phase is increased, then saturation magnetic flux density is improved, but magnetic anisotropy deteriorates
Solution Approach 1:
The invention changes the oxidation state parameter of Ce to a mixed valence state, which fundamentally alters the magnetic anisotropy characteristics. This allows the material to maintain high magnetic anisotropy even with high Fe concentration, as the mixed valence state of Ce provides the necessary anisotropy that pure Fe concentration cannot achieve
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 magnet achieves high coercivity and magnetic anisotropy while maintaining corrosion resistance by stabilizing the trivalent Ce state within the specified composition range, enhancing its magnetic properties without compromising durability.
Implementation Method 1
Rare earth magnets composed mainly of intermetallic compounds of rare earth elements with transition metal elements such as Fe and Co have a high magnetocrystalline anisotropy
Implementation Method 2
Rare earth permanent magnets containing a tetragonal R2T14B compound as the main phase are known to exhibit excellent magnetic properties
Data Source
AI summary
To provide a permanent magnet which uses Ce of an abundant resource and has a great magnetic anisotropy in rare earth permanent magnets. To obtain a permanent magnet having a high magnetic anisotropy due to the trivalent Ce state by setting the abundance ratio C3/(C3+C4) in the main phase grains to be 0.1≤C3/(C3+C4)≤0.5 where C3 denotes the number of trivalent Ce atoms and C4 denotes the number of tetravalent Ce atoms.