Lanthanide Salt Infiltration for NdFeB Magnet Temperature Resistance
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Solution Overview
Problem
Existing magnetic materials face challenges with high magnetic losses at high frequencies and limited temperature resistance, making them unsuitable for high-load electrical machines and high-temperature applications.
Innovation Solution
A method involving a magnetic powder mixture of iron, boron, and lanthanides, with a debinding step and infiltration of a second lanthanide and salt solution into an open-pored preform, followed by heat treatment to enhance magnetic properties and reduce electrical conductivity, resulting in a sintered, polymer-free magnetic material with improved temperature resistance and reduced eddy current losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metallic-magnetic component is used in plastic-bonded magnets, then good permanent magnetic properties are achieved, but temperature resistance deteriorates above 100°C
Solution Approach 1:
The patent uses a composite structure consisting of metallic-magnetic grains (e.g., NdFeB) embedded in a ceramic matrix (e.g., Nd-rich phase). This composite approach combines the high magnetic properties of metallic materials with the high-temperature stability of ceramic materials, enabling the magnet to maintain both strong permanent magnetic properties and temperature resistance above 100°C
Solution Approach 2:
The patent employs a porous ceramic matrix structure that accommodates the metallic-magnetic grains. The porous structure allows for thermal expansion compensation and maintains structural integrity at high temperatures while preserving the magnetic properties through the distributed metallic inclusions
2Manufacturing precision
If liquid phase sintering is used to produce metallic permanent magnets, then a fine microstructure is achieved, but the process becomes complex and difficult to regulate
Solution Approach 1:
The patent extracts and eliminates the complex liquid phase sintering process by using a simplified two-step method: (1) forming a green compact with binder, and (2) selective removal of the binder to create a porous structure. This extraction of the problematic liquid phase sintering step while maintaining the desired fine microstructure through controlled binder removal and subsequent infiltration
Solution Approach 2:
The patent introduces a binder as an intermediary material that facilitates the formation of a green compact with controlled microstructure. The binder acts as a temporary scaffold that is subsequently removed to create the desired porous structure, enabling fine microstructure control without requiring complex liquid phase sintering processes
3Loss of energy
If electrical conductance is reduced to lower eddy current losses, then high frequency performance is improved, but permanent magnetic properties deteriorate
Solution Approach 1:
The patent applies local quality by creating regions of different electrical conductance within the magnet structure. The metallic-magnetic grains maintain high conductivity for magnetic domain wall movement (preserving magnetic properties), while the ceramic matrix and grain boundary phases provide electrical isolation (reducing eddy current losses). This spatial differentiation of electrical properties allows simultaneous optimization of both magnetic performance and high-frequency characteristics
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 a magnetic material with exceptionally high permanent magnetic properties and temperature resistance exceeding 100°C, suitable for high-frequency applications with reduced ohmic eddy current losses, utilizing a microstructure with a second lanthanide and salt in the intermediate phase to enhance magnetic properties and conductivity.
Implementation Method 1
heat-treating the infiltrated preform at a temperature level which results in diffusion of the second lanthanide and the salt in an interface between grains of the magnetic powder
Implementation Method 2
The infiltration of liquid media, which is driven on the basis of capillary effects and capillary forces, preferably takes place
Implementation Method 3
removing the solvent and heat-treating the infiltrated preform
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a method for producing a magnetic material (2), comprising the following steps: - providing a mixture (4) of a magnetic powder (6) comprising iron, boron, and a first lanthanide (8), and a binder (10), - shaping the mixture (4) into a preform (12), - performing a debinding step (14) to remove the binder (10) to form an open-pore preform (16), - providing a second mixture (18) of a second lanthanide (20) and a salt (22) having an electrical conductivity of less than 10⁻¹ S/m, - dissolving this second mixture (18) in a solvent (24) to form a solution (26), - infiltration of the open-pore preform (16) with the solution (26), - removal of the solvent (24), and - heat treatment (28) of the infiltrated preform (30) at a temperature levelthat leads to a diffusion of the second lanthanide (20) and the salt (22) in a boundary region between grains (32) of the magnetic powder (6).