Enormous improvement of the coercivity of Ga and Cu co-doping Nd-Fe-B sintered magnet by post-sinter annealing

Huang, Qiu‐An; Jiang, Qingzheng; Shi, Yao; Wei, Xing; Li, Zhixiang; Shi, Dawei; Xu, Deqin; Zhong, Zhenchen

doi:10.1016/j.jallcom.2021.162418

Cited by 15 publications

(5 citation statements)

References 44 publications

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“…The grain boundary phases are several nanometers in width and distributed between a magnetically hard phase of Nd 2 Fe 14 B, and the exchange coupling between the magnetically hard phases must not lead to a decrease in coercivity [40,41]. The appropriate composition of Cu, Ga, Al and Zr is beneficial to improving the wettability and modifying the microstructure of the grain boundary [6], and the defect concentration and the area of the defect region can be reduced at the grain boundary. Provided that the small defect regions are well exchange-coupled with the perfect regions, the nucleation of reversed domains cannot occur independently in the defect regions at the grain boundary [42,43], and so the coercivity does not decrease significantly.…”

Section: Resultsmentioning

confidence: 99%

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Macroscopic phenomenon of exchange coupling and microscopic effect on magnetization reversal in sintered Nd–Fe–B magnets

Wang,

Li,

et al. 2024

J. Phys. D: Appl. Phys.

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The permanent magnets of Nd13.5Fe79.18M1.52B5.8 and Nd13.5Fe79.76M0.94B5.8 were prepared, respectively, via strip casting, jet milling and sintering followed by annealing, and adding the non-ferromagnetic elements M (Al, Cu, Ga and Zr) could not only modify the microstructure, but also regulate the exchange coupling effect in the sintered magnets. From the macroscopic view the recoil loops bear spring behavior in Nd13.5Fe79.76M0.94B5.8, indicating that the energy barrier could be overcome by the intergranular exchange coupling. From the microcosmic view, the exchange coupling could increase the domain wall size by suppressing the nucleation of reversed domain, and so the activation volume increases in thermal activation. In Nd13.5Fe79.76M0.94B5.8 the exchange coupling effect is stronger, and both the coercivty of 15.0 kOe and the remanence of 14.3 kGs are a little higher than those of Nd13.5Fe79.18M1.52B5.8 magnets in which the content of non-ferromagnetic elements is a little higher and the exchange coupling effect is weaker. So the exchange coupling must not decrease the coercivity owing to the exchange coupling suppressing the nucleation of reversed domain, though the microstructure is inhomogeneous in the sintered magnets of Nd13.5Fe79.76M0.94B5.8. Reducing the defects size and decreasing the defects concentration should be the practical way to improve the coercivity in Nd-Fe-B permanent magnets.

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Section: Resultsmentioning

confidence: 99%

“…In order to enhance the coercivity, it is * Author to whom any correspondence should be addressed. necessary to add non-ferromagnetic elements to the sintered magnets [6]. The non-ferromagnetic elements, i.e.…”

Section: Introductionmentioning

confidence: 99%

Macroscopic phenomenon of exchange coupling and microscopic effect on magnetization reversal in sintered Nd–Fe–B magnets

Wang,

Li,

et al. 2024

J. Phys. D: Appl. Phys.

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“…Currently, widely used high-performance permanent magnets are made from rare-earth transition metal intermetallic compounds such as Nd-Fe-B, [1,2] Sm-Co, [3][4][5][6][7] and Sm-Fe-N. [8] The macroscopic magnetic properties are not only dominated by the materials parameters of the main ferromagnetic component of the magnet but also highly dependent on the microstructure and the microscopic magnetization processes of the magnets. [9][10][11] Therefore, performance of permanent magnets can be supplemented and enhanced by microstructure modifications and manipulations, such as elemental substitution, [12] and grain boundary diffusion. [13] Noticeably, a great idea with real potential to significantly raise the record energy product is the oriented exchange-spring hardsoft nanocomposite magnet.…”

Section: Introductionmentioning

confidence: 99%

Micromagnetic study of magnetization reversal in inhomogeneous permanent magnets

et al. 2023

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The macroscopic magnetic properties of magnets strongly depend on the magnetization process and the microstructure of the magnets. Complex materials such as hard-soft exchange-coupled magnets or just real technical materials with impurities and inhomogeneities exhibit a complex magnetization behavior. Here we have investigated the effect of the size, volume fraction, and the surroundings of inhomogeneities on the magnetic properties of an inhomogeneous magnetic material via micromagnetic simulations. The underlying magnetization reversal and coercivity mechanisms were revealed. Three different demagnetization characterizations corresponding to the exchange coupling phase, semi-coupled phase, and decoupled phase are found, depending on the size of inhomogeneities. In addition, the increase in the size of inhomogeneities leads to a transition of the coercivity mechanism from nucleation to pinning. This work could be useful for optimizing the magnetic properties of both exchange-coupled nanomagnets and inhomogeneous single-phase magnets.

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“…The NdFeB permanent magnet easily loses excitation when the working environment of the motor is poor and the iron core loss is large [16,17]. In order to solve this problem, there are two research directions: doping of NdFeB with other rare Earth elements or metal oxides during the sintering and forming process [18][19][20][21]. Studies have shown that doping with Ho [18], co-doping with Al/Cu [19], or co-doping with Ga/Cu [20,21] during the sintering and formation of NdFeB PMs can effectively improve the microstructure of the PMs and further enhance their magnetic properties.…”

Section: Introductionmentioning

confidence: 99%

“…In order to solve this problem, there are two research directions: doping of NdFeB with other rare Earth elements or metal oxides during the sintering and forming process [18][19][20][21]. Studies have shown that doping with Ho [18], co-doping with Al/Cu [19], or co-doping with Ga/Cu [20,21] during the sintering and formation of NdFeB PMs can effectively improve the microstructure of the PMs and further enhance their magnetic properties. The magnetic properties of NdFeB materials can also be improved by optimising the NdFeB sintering manufacturing technology [22,23], then changing the bottleneck particle size of the permanent magnet material powder [24].…”

Section: Introductionmentioning

confidence: 99%

A Novel Design of Permanent Magnets for the Air Gap Magnetic Field of Hollow-Cup Motor

Sun

2023

Applied Sciences

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Spacecraft motors are often driven with trapezoidal phase currents to achieve higher output torque. For hollow cup motors (HCM) driven by trapezoidal wave currents, parallel magnetised permanent magnet (PM) motors produce an air gap magnetic field (AMF) waveform which is significantly different from the trapezoidal wave, causing the motor to generate noise or vibration. The existing control optimisation method or structure improvement design method is difficult to directly apply to HCM due to its large gas gap. In this paper, according to the fundamental theory of a constant magnetic field, the AMF of HCM is analysed using the equivalent surface current method (ESCM) and its mathematical model is established. The analytical expression of the AMF is solved, and the influencing parameters of the AMF are clarified. The structural design of the HCM with eccentric PMs sintered with high-performance NdFeB is further improved. On this basis, a prototype motor is designed. Simulation results show that the structure can effectively increase the width of the flat section of the AMF and make the AMF close to an ideal trapezoidal wave (ITW). Experiments verify the correctness of the method.

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Enormous improvement of the coercivity of Ga and Cu co-doping Nd-Fe-B sintered magnet by post-sinter annealing

Cited by 15 publications

References 44 publications

Macroscopic phenomenon of exchange coupling and microscopic effect on magnetization reversal in sintered Nd–Fe–B magnets

Macroscopic phenomenon of exchange coupling and microscopic effect on magnetization reversal in sintered Nd–Fe–B magnets

Micromagnetic study of magnetization reversal in inhomogeneous permanent magnets

A Novel Design of Permanent Magnets for the Air Gap Magnetic Field of Hollow-Cup Motor

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