Neodymium-Iron-Boron Magnet Coercive Force via Rare Earth Infiltration
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Solution Overview
Problem
Conventional methods for producing neodymium-iron-boron permanent magnets struggle to achieve high magnetic energy product and intrinsic coercive force while minimizing the use of rare earth elements, leading to increased costs and resource depletion due to the finite reserves of dysprosium and terbium.
Innovation Solution
A method involving coating a rare earth element-containing substance on the surface of neodymium-iron-boron magnets, followed by vacuum heat treatment to enhance infiltration homogeneity and efficiency, thereby improving coercive force without significantly reducing remanence, using specific vacuum conditions and quartz containers to facilitate the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional manufacture process is used to achieve high magnetic energy product and high intrinsic coercive force, then a large amount of rare earth elements Dy and Tb are needed, but the reserves of dysprosium and terbium are finite causing prices to rise and accelerated depletion of rare earth resources
Solution Approach 1:
The invention changes the chemical state of the rare earth coating material from solid to vapor phase through heat treatment, enabling controlled diffusion into the magnet. This parameter change (phase transition) allows rare earth infiltration without requiring large amounts of material, resolving the contradiction between achieving high coercive force and reducing rare earth consumption
Solution Approach 2:
The invention uses a vacuum environment as an intermediary medium to facilitate the diffusion process. The vacuum conditions enable controlled vapor-phase transport of rare earth elements from the coating layer into the magnet's crystal grain boundary phase, achieving efficient infiltration with minimal rare earth consumption
2Reliability
If oxide, fluoride and/or oxyfluoride of heavy rare earth is disposed on the surface for infiltration, then the rare earth is absorbed in the magnet body, but harmful substances such as O and F are introduced into the magnet and oxide-scales form on the surface requiring grinding that wastes magnet materials
Solution Approach 1:
The invention extracts only the beneficial rare earth elements from their compound forms (oxides, fluorides, oxyfluorides) by converting them to vapor phase through heat treatment. The rare earth atoms diffuse into the magnet while the harmful oxygen and fluorine remain in the vacuum environment or form volatile compounds, effectively separating the useful from the harmful components
Solution Approach 2:
The invention converts the potential harm of using rare earth compounds into a benefit by utilizing thermal decomposition and vaporization. The heat treatment process that could potentially create more oxides instead reduces the compounds to atomic vapor state, allowing clean diffusion of rare earth atoms without introducing additional oxygen or fluorine into the magnet structure
3Reliability
If Dy is evaporated in reduced pressure to diffuse in the crystal grain boundary phase, then magnetization intensity and coercive force are enhanced, but expensive equipment cost and low evaporation efficiency are incurred and the effect is inferior to oxide coating method
Solution Approach 1:
The invention changes the physical state and processing conditions by using solid-state diffusion of rare earth atoms from a coating layer rather than vapor-phase evaporation. This parameter change from evaporation to solid-state diffusion simplifies the equipment requirements and improves efficiency while achieving superior coercive force enhancement
Solution Approach 2:
The invention performs preliminary coating of the rare earth material on the magnet surface before the diffusion process. This preliminary action creates a reservoir of rare earth atoms that can diffuse into the magnet during heat treatment, eliminating the need for complex vapor generation equipment and improving overall process efficiency
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 method achieves significant improvement in coercive force while maintaining remanence, reducing the reliance on expensive rare earth elements and minimizing waste, thus lowering production costs and conserving resources.
Implementation Method 1
heat treating the powder-covered magnet body at a temperature below the sintering temperature in vacuum or in an inert gas, so that the other rare earth is absorbed in the magnet body
Implementation Method 2
in a reduced pressure, the treatment chamber is heated so that not only is the temperature of the sintered magnet raised to a given temperature but also Dy is evaporated
Implementation Method 3
in a reduced pressure, the treatment chamber is heated so that not only is the temperature of the sintered magnet raised to a given temperature but also Dy is evaporated to thereby attain supply of evaporated Dy atoms to the surface of the sintered magnet and adhesion therebetween
Data Source
AI summary
The present invention provides a method for preparing a permanent magnet material, the method comprising coating step and infiltrating step, wherein, coating a rare earth element-containing substance on the surface of a permanent magnet, the magnet having a thickness of 10 mm or less at least in one direction, then placing the magnet into a container, vacuuming to an atmospheric pressure of below 10 Pa, closing the passageway, and then heat treating the closed container. Using the method of the present invention enables the rare earth element to infiltrate homogeneously with a high permeability. In addition, the present invention may have a lower production cost, significantly increase coercive force of the permanent magnet material, but decrease the remanence very little.