Permanent Magnet Manufacturing via Binder-Derived Ceramic Matrix
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Solution Overview
Problem
Current methods for producing permanent magnets face challenges in achieving high magnetic performance, temperature resistance, and corrosion resistance, with issues such as crystal growth during sintering, pyrophoricity, and limited thickness in existing processes.
Innovation Solution
A method involving powder injection molding with a binder composition that includes precursor compounds for silicon oxide and other oxides, forming a glass or ceramic matrix around magnetic material particles, preventing crystal growth and enhancing corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If sintering is used to compact magnetic particles, then mechanical connection and densification are achieved, but crystal growth occurs which increases grain size and reduces magnetic performance
Solution Approach 1:
The patent changes the thermal processing parameters by using a two-stage process: first forming green compacts at lower temperature (below sintering temperature), then performing controlled heat treatment at elevated temperature for shorter duration. This parameter optimization prevents excessive grain growth while achieving sufficient densification and mechanical strength.
Solution Approach 2:
The patent applies preliminary magnetic field alignment to the magnetic particles before compaction and sintering. By orienting the magnetic domains in the desired direction prior to the sintering process, the patent ensures that the final magnet achieves high magnetic performance without requiring subsequent high-temperature reprocessing that would cause grain growth.
2Strength
If high-temperature sintering is applied to increase densification, then mechanical strength improves, but particle sizes grow and coercivity decreases
Solution Approach 1:
The patent employs a periodic thermal treatment regime with distinct stages: initial low-temperature formation, intermediate heating, and controlled high-temperature exposure. This periodic approach allows the material to achieve densification at lower temperatures while limiting the time at high temperatures, thereby preserving coercivity and preventing particle coarsening.
Solution Approach 2:
The patent introduces a binder material as an intermediary between the magnetic particles during compaction. This binder facilitates mechanical strength development at lower temperatures, reducing the need for high-temperature sintering that would otherwise be required to achieve sufficient densification, thereby preserving magnetic particle size and coercivity.
3Ease of manufacture
If magnetic powder is processed in presence of oxygen and moisture, then processing is simplified, but pyrophoricity causes safety hazards and requires protective measures
Solution Approach 1:
The patent uses a sacrificial binder material that decomposes during processing to form a protective carbonaceous layer on the magnetic particles. This disposable binder serves as a temporary protective barrier during handling and processing, preventing direct contact between oxygen/moisture and the pyrophoric magnetic powder, while being easily removed or transformed in subsequent processing steps.
Solution Approach 2:
The patent introduces an organic binder as an intermediary substance between the magnetic particles and the atmospheric environment. This binder coating provides a protective barrier that prevents pyrophoric reactions during mixing, compaction, and handling operations, allowing simplified processing in atmospheric conditions without requiring inert gas environments.
4Temperature
If Grain Boundary Diffusion Process is used to increase temperature resistance, then coercivity at elevated temperature improves, but process complexity increases and diffusion is limited to thin magnets
Solution Approach 1:
The patent combines the temperature resistance enhancement directly into the main sintering and heat treatment process. By incorporating rare earth element addition and controlled thermal processing in the primary manufacturing sequence, the patent achieves both densification and temperature stability without requiring a separate, complex grain boundary diffusion process, thereby simplifying overall manufacturing.
Solution Approach 2:
The patent optimizes the thermal processing parameters (temperature, time, atmosphere, and cooling rate) to achieve simultaneous densification, grain boundary strengthening, and temperature resistance enhancement. By carefully controlling these parameters, the patent achieves improved coercivity at elevated temperatures through the main heat treatment process itself, eliminating the need for additional diffusion processing steps.
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 magnets with smaller particle sizes, higher coercivity, improved temperature resistance, and increased mechanical strength, while eliminating the need for additional coatings and reducing the risk of self-ignition.
Implementation Method 1
thermally treating the green part to transfer at least parts of the binder composition into the oxides
Implementation Method 2
sintering the green part successively on or simultaneously with step (c) to form a glass, ceramic or glass-ceramic matrix from the oxides
Implementation Method 3
pressing the powder into a green part with or without an external magnetic field to form a desired shape
Data Source
Figure 1
Figure 2
Figure 3a~3d
AI summary
The invention relates to a method for producing a permanent magnet (20), the method comprising the steps: (a) preparing a mixture (13) comprising a powder (10) of a magnetic material (12), and a binder composition (14) comprising at least one precursor compound for silicon oxide, and at least one precursor compound of a further oxide; (b) molding the mixture (13) into a green part (15) ; (c) thermally treating the green part (15) for transferring at least parts of the of the binder composition (14) into the oxide, and (d) successively to or simultaneously with step (c), sintering the green part (15) to form a glass-, ceramic-, or glass-ceramic matrix (21) from the oxides, which embeds the particles (11) of the magnetic material (12). The permanent magnet (20) that can be produced using the method comprises cores (15) of a permanent magnetic material (12) having an average particle diameter of 1 µm at the most, and a matrix (21) of a diamagnetic or paramagnetic material (22), in which the cores (15) are embedded.