Samarium-Iron-Nitrogen Alloy Powder Coercivity Control
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Solution Overview
Problem
Samarium-iron-nitrogen alloy powders with high coercivity are difficult to produce, especially those with an average particle diameter less than 1 μm, as their coercivity sharply decreases when the diameter becomes less than or equal to 1 μm, limiting their application in high-heat-resistant motors.
Innovation Solution
A method involving a reduction-diffusion process on a samarium-iron alloy precursor powder, followed by nitriding, washing with a solvent to remove calcium, and dehydrogenation in a non-oxidizing atmosphere to control lattice expansion and reduce hydrogen content, resulting in a samarium-iron-nitrogen alloy powder with improved coercivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the average particle diameter of samarium-iron-nitrogen alloy powder is reduced to increase coercivity, then coercivity improves up to a point, but when the diameter becomes less than or equal to 1 μm, coercivity sharply decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the hydrogen content and oxygen content of the alloy powder, as well as the lattice constant c/a ratio. By adjusting these parameters within specific ranges, the patent achieves high coercivity (20.3 kOe or higher) while maintaining an average particle diameter of 1.0 μm or less, overcoming the limitation where coercivity sharply decreases at this particle size threshold.
2Temperature
If dysprosium is added to neodymium-iron-boron magnets to improve heat resistance, then heat resistance improves, but the supply of dysprosium is limited due to low production and limited production areas
Solution Approach 1:
The patent replaces the scarce and expensive dysprosium element with a samarium-iron-nitrogen alloy system that achieves comparable or superior heat resistance without requiring rare earth elements like dysprosium. This substitution uses more readily available materials to achieve the same functional goal of high-temperature performance.
3Strength
If the lattice constant c/a ratio of samarium-iron-nitrogen alloy is increased to improve coercivity, then coercivity improves, but the hydrogen content and oxygen content must be strictly controlled to maintain lattice structure
Solution Approach 1:
The patent establishes specific parameter ranges for hydrogen content (0.03-0.15 mass%), oxygen content (0.005-0.05 mass%), and lattice constant c/a ratio (1.445-1.455) that work together to achieve high coercivity. By defining these interrelated parameters, the patent provides a controllable manufacturing framework that balances the need for precise composition control with the goal of achieving superior magnetic properties.
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 produces samarium-iron-nitrogen alloy powders with coercivity exceeding 20 kOe, suitable for high-heat-resistant applications, by controlling the hydrogen and oxygen content and lattice expansion, thereby enhancing their magnetic properties.
Implementation Method 1
reduction-diffusion of hydrogen-reduced samarium-iron oxide particles produced by a coprecipitation method or the like to samarium-iron alloy particles
Implementation Method 2
nitriding the samarium-iron alloy particles
Data Source
AI summary
A samarium-iron-nitrogen alloy powder according to one embodiment of the present invention is characterized in that a value obtained by dividing the hydrogen content of the samarium-iron-nitrogen alloy powder by the BET specific surface area of the samarium-iron-nitrogen alloy powder is less than or equal to 400 ppm/(m2/g), and a value obtained by dividing the oxygen content of the samarium-iron-nitrogen alloy powder by the BET specific surface area of the samarium-iron-nitrogen alloy powder is less than or equal to 11,000 ppm/(m2/g).