R-T-B-C Sintered Magnet Grain Boundary Insulation
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Solution Overview
Problem
Rare earth magnets, particularly Nd-Fe-B sintered magnets, experience significant heat generation due to eddy currents in varying magnetic fields, leading to efficiency deterioration and magnetic property degradation, which existing countermeasures fail to adequately address without increasing costs or compromising magnetic properties.
Innovation Solution
The development of R-T-B-C rare earth sintered magnets, where R is a rare earth element like Ce, Pr, Nd, or Dy, T is iron or a transition metal, and C is carbon, with a sintered structure incorporating an R-rich sintering aid alloy, R-O 1-x -F 1+2x or R-F y powder, and a primary phase magnet matrix alloy, pulverized and compacted in a magnetic field, then sintered and heat-treated, to achieve high coercive force, resistivity, and temperature coefficient of resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rare earth magnets are used in motors, then motor efficiency and size are improved, but heat generation due to eddy current increases
Solution Approach 1:
An insulating phase is introduced as an intermediary substance within the magnet structure. This insulating phase acts as a mediator that blocks eddy current paths while maintaining the magnetic properties of the rare earth magnet, thereby reducing heat generation without sacrificing motor efficiency
Solution Approach 2:
The magnet is designed as a composite material system combining magnetic phases (for high efficiency) with insulating phases (for eddy current suppression). This composite structure allows simultaneous achievement of high motor efficiency and low heat generation by leveraging the complementary properties of different materials
2Loss of energy
If the resistivity of a magnet is increased by adding an insulating phase, then eddy current loss is reduced, but densification becomes difficult and magnetic properties deteriorate
Solution Approach 1:
The sintering parameters (temperature, time, atmosphere) are optimized and adjusted to achieve proper densification of the composite magnet containing insulating phases. By changing these processing parameters, the patent overcomes the densification difficulty caused by insulating phase addition while maintaining low eddy current loss
3Reliability
If heavy rare earth elements substitute for Nd-Fe-B to enhance coercive force, then magnet stability is improved, but manufacturing cost increases
Solution Approach 1:
Instead of uniformly substituting heavy rare earth elements throughout the magnet, the insulating phase is selectively positioned at grain boundaries and specific locations. This local modification approach achieves the desired magnetic stability improvement without the high cost of bulk heavy rare earth substitution
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 approach results in a low-loss sintered magnet with high resistivity and controlled eddy current generation, maintaining magnetic properties while reducing manufacturing costs and heat generation, suitable for applications in motors and electronic equipment.
Implementation Method 1
a problem arises when rare earth magnets are used in motors. Since a varying magnetic field is applied across the magnet, eddy current is created by electromagnetic induction. By the Joule heat due to eddy current flow, the permanent magnet generates heat.
Implementation Method 2
mixing an R-T-B-C magnet matrix alloy with an R-rich R-T-B-C sintering aid alloy, followed by pulverization, compaction and sintering
Implementation Method 3
compact the mixture in a magnetic field
Data Source
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AI summary
An R-T-B-C rare earth sintered magnet (R = Ce, Pr, Nd, Tb, or Dy; T = Fe) is obtained by mixing an R-T-B-C magnet matrix alloy with an R fluoride and an R-rich R-T-B-C sintering aid alloy, followed by pulverization, compaction and sintering. The sintered structure consists of an R2T14B type crystal primary phase and a grain boundary phase. The grain boundary phase consists essentially of 40-98 vol% of R-O1-x-F1+2x and/or R-Fy, 1-50 vol% of R-O, R-O-C or R-C compound phase, 0.05-10 vol% of R-T phase, 0.05-20 vol% of B-rich phase or M-B2 phase (M = Ti, V, Cr, Zr, Nb, Mo, Hf, Ta or W), and the balance of an R-rich phase.