Permanent Magnet Coating Sintering Process
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Solution Overview
Problem
Existing methods for producing permanent magnets face challenges such as crystal growth during sintering, pyrophoricity, corrosion, and high production costs, leading to reduced magnetic performance and temperature resistance.
Innovation Solution
A process involving coating magnetic material particles with a diamagnetic or paramagnetic material, sintering the coating at a temperature below the magnetic material's sintering point to prevent magnetic material sintering, and magnetizing in an external field, resulting in small particle sizes and improved corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If sintering is performed at high temperature to bond magnetic particles, then mechanical strength and bonding are improved, but crystal growth occurs leading to increased particle size and reduced magnetic performance
Solution Approach 1:
A binder phase is introduced as an intermediary material between magnetic particles during sintering. This binder phase melts at a lower temperature than the magnetic particles, enabling particle bonding through liquid-phase sintering at temperatures below the magnetic material's sintering point, thus preventing crystal growth while achieving mechanical bonding.
Solution Approach 2:
The sintering temperature parameter is changed from high temperature (above magnetic material sintering point) to low temperature (below magnetic material sintering point but above binder melting point). This parameter change enables bonding without causing unwanted crystal growth in the magnetic particles.
2Manufacturing precision
If magnetic material is processed in powder form to achieve small particle size, then magnetic performance is improved, but pyrophoricity increases requiring protective measures
Solution Approach 1:
The binder phase serves as a protective intermediary that coats and isolates the reactive magnetic powder particles from oxygen and moisture during processing. This eliminates pyrophoricity concerns while maintaining the fine particle size necessary for high magnetic performance.
Solution Approach 2:
The final magnet is formed as a composite material combining magnetic particles with a binder phase. This composite structure maintains the advantages of fine magnetic particles while the binder provides protective functionality, eliminating the need for separate protective coatings.
3Temperature
If additional substances are introduced by diffusion to increase temperature resistance, then temperature stability is improved, but production cost and process time increase
Solution Approach 1:
The binder phase acts as a thermal barrier and stabilizing intermediary between magnetic particles, providing temperature resistance without requiring time-consuming diffusion processes. The binder protects the magnetic structure from thermal degradation during service.
4Strength
If magnetic material is sintered at high temperature to achieve bonding, then mechanical compression is improved, but corrosion resistance decreases
Solution Approach 1:
The binder phase serves as a protective intermediary that coats magnetic particles and provides corrosion resistance. This protective layer prevents direct exposure of the magnetic material to corrosive environments while maintaining mechanical integrity through the bonding function.
Solution Approach 2:
The composite structure of magnetic particles embedded in a protective binder matrix provides both mechanical strength and corrosion resistance. The binder phase acts as a barrier against corrosion while the magnetic particles provide the functional 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 process maintains small magnetic particle sizes, enhances coercive field strength, temperature resistance, and corrosion resistance, while reducing production costs and eliminating the need for protective measures against pyrophoricity.
Implementation Method 1
sintering of the coating material at a temperature that is lower than a suitable temperature for sintering (and melting) of the magnetic material
Implementation Method 2
magnetizing the magnetic material in an external magnetic field
Data Source
AI summary
A method for producing a permanent magnet, comprising the step: (a) providing a powder of a magnetic material, (b) coating the powder particles with a coating of a diamagnetic or paramagnetic coating material, (c) compressing the coated particles to form a pressed part, (d) heat treatment to sinter the coating material at a temperature less than a temperature suitable for sintering the magnetic material, while the coating material transfers to a matrix of a diamagnetic or paramagnetic material, which embeds the particles of the magnetic material, and (e) magnetizing the magnetizable material in an external magnetic field, wherein the steps (c), (d) and (e) are carried out in any order successively or at the same time in any desired combination. The nanostructured permanent magnet that can be produced by mean of said method comprises cores of a permanently magnetic material having a mean particle diameter of no more than 1 μm and a matrix of a diamagnetic or paramagnetic material in which the cores are embedded.