NdFeB Magnetic Powder Production via Reduction-Diffusion
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Solution Overview
Problem
Current methods for producing NdFeB-based magnetic powders are costly and inefficient, with irregular particle shapes and limited refinement, leading to decreased coercive force and magnetic characteristics due to high-temperature sintering and complex processing steps.
Innovation Solution
A reduction-diffusion process using iron oxide as a raw material to produce ultrafine NdFeB magnetic powders with a regular shape, eliminating the need for high-priced micro iron powders and reducing production costs, while suppressing particle growth through a fluoride coating during sintering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional pulverizing methods (coarse pulverization and hydrogen decrepitation/jet mill) are used to produce NdFeB micro particles, then the magnetic powder can be obtained, but the particle shape becomes irregular and particle refinement is limited
Solution Approach 1:
The invention changes the fundamental production approach from mechanical pulverization to chemical reduction-diffusion. By controlling chemical reaction parameters (temperature, pressure, composition ratios of Fe, Nd2O3, and B), uniform submicrometer particles with regular shapes are obtained directly, eliminating the need for complex multistep pulverizing processes and achieving superior particle refinement.
Solution Approach 2:
The invention replaces the mechanical pulverizing system (coarse pulverization, hydrogen decrepitation, jet mill) with a chemical reduction-diffusion system. This substitution enables direct formation of uniform fine particles through controlled chemical reactions, avoiding the particle shape irregularity and refinement limitations inherent in mechanical methods.
2Reliability
If high-temperature sintering (1000-1200°C) is applied to produce NdFeB-based magnet, then the magnetic properties are achieved, but crystal growth of particles occurs causing decreased coercive force
Solution Approach 1:
The invention performs preliminary action by producing ultrafine uniform particles (1-10 μm) through reduction-diffusion before sintering. This preliminary particle formation with controlled size and regular shape creates a foundation that resists excessive crystal growth during subsequent high-temperature sintering, thereby maintaining high coercive force while achieving necessary magnetic properties.
Solution Approach 2:
The invention changes the particle size parameter to ultrafine range (1-10 μm) through reduction-diffusion, which fundamentally alters the sintering behavior. These ultrafine particles exhibit suppressed crystal growth kinetics during high-temperature sintering, allowing the material to achieve magnetic properties while retaining high coercive force that would be lost with conventional particle sizes.
3Manufacturing precision
If reduction-diffusion process using micro iron powder (carbonyl iron powder) is used to produce uniform NdFeB fine particles, then uniform particles are obtained, but production costs become high due to high-priced micro iron powder
Solution Approach 1:
The invention replaces expensive micro iron powder (carbonyl iron powder) with inexpensive raw materials (Fe, Nd2O3, and B in specific ratios). By using these cheap starting materials in the reduction-diffusion process, the invention achieves the same particle uniformity without the high material costs, making the process economically viable for mass production.
Solution Approach 2:
The invention changes the material composition parameters by using Fe, Nd2O3, and B in specific ratios instead of pre-formed micro iron powder. This parameter change in the starting materials maintains the effectiveness of the reduction-diffusion process for producing uniform particles while dramatically reducing material costs.
4Manufacturing precision
If complex processes (HDDR or hot deformation) are applied to suppress particle growth during sintering, then coercive force is secured to some extent, but the process becomes very complicated and particle migration still occurs causing decreased magnetic characteristics
Solution Approach 1:
The invention extracts and eliminates the complex intermediate processes (HDDR or hot deformation) from the production flow. By producing ultrafine uniform particles directly through reduction-diffusion, the invention removes the need for these complicated particle growth suppression steps, simplifying the overall process while maintaining high coercive force and avoiding particle migration issues.
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 process results in high coercive force characteristics and reduced production costs, with improved magnetic powder density and coercive force retention, overcoming the limitations of conventional methods by producing uniform, submicrometer-sized particles and minimizing crystal growth during sintering.
Implementation Method 1
producing an iron powder by a reduction reaction of iron oxide
Implementation Method 2
producing a magnetic powder by heating a molded body obtained by press molding a mixture including the iron powder, neodymium oxide, boron, and calcium
Implementation Method 3
a fluoride coated film is formed on a particle surface of the magnetic powder, whereby the crystal growth of the magnetic powder particles in a sintering process may be suppressed
Data Source
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AI summary
A method of producing a magnetic powder and a magnetic powder is provided. The method of producing a magnetic powder according to an exemplary embodiment of the present disclosure includes: producing an iron powder by a reduction reaction of iron oxide, producing a magnetic powder using a molded body obtained by press molding a mixture including the iron powder, a rare earth oxide, boron, and calcium at a pressure of 22 MPa or more, and coating a surface of the magnetic powder with ammonium fluoride.