Properties improvement and structural optimization of sintered NdFeB magnets by non-rare earth compound grain boundary diffusion

Zhou, Qing; Liu, Zhongwu; Zhong, Xichun; Zhang, Kouchi

doi:10.1016/j.matdes.2015.07.067

Cited by 70 publications

(14 citation statements)

References 22 publications

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“…The magnetic saturation, Ms, which is calculated by subtracting the non-saturating slope (SFO is ferrimagnetic), is 380 emu/cm 3 . The remnant magnetization, Mr, is 310 emu/cm 3…”

Section: Resultsmentioning

confidence: 99%

“…Permanent magnets (PMs) are used in a wide variety of applications ranging from power sources to switches and actuators [1,2]. Today, high-performance sintered magnets [3] are playing an increasingly important role in electric motors and generators [4] since PM based designs are usually more efficient than traditional electro-magnet based designs because they do not require external power to generate the requisite magnetic field. In addition, PM based energy generating systems are typically more compact and require less maintenance, and therefore offer lower operational costs than traditional motors and generators.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic and thermal transport properties of SrFe12O19 permanent magnets with anisotropic grain structure

et al. 2017

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Nanostructured permanent magnets are gaining increasing interest and importance for applications such as generators and motors. Thermal management is a key concern since performance of permanent magnets decreases with temperature. We investigated the magnetic and thermal transport properties of rare-earth free nanostructured SrFe12O19 magnets produced by the current activated pressure assisted densification. The synthesized magnets have aligned grains such that their magnetic easy axis is perpendicular to their largest surface area to maximize their magnetic performance. The SrFe12O19 magnets have fine grain sizes in the cross-plane direction and substantially larger grain sizes in the in-plane direction. It was found that this microstructure results in approximately a factor of two higher thermal conductivity in the in-plane direction, providing an opportunity for effective cooling. The phonons are the dominant heat carriers in this type of permanent magnets near room temperature. Temperature and direction dependent thermal conductivity measurements indicate that both Umklapp and grain boundary scattering are important in the in-plane direction, where the characteristic grain size is relatively large, while grain boundary scattering dominates the cross-plane thermal transport. The investigated nano/microstructural design strategy should translate well to other material systems and thus have important implications for thermal management of nanostructured permanent magnets.

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“…The magnetic saturation, Ms, which is calculated by subtracting the non-saturating slope (SFO is ferrimagnetic), is 380 emu/cm 3 . The remnant magnetization, Mr, is 310 emu/cm 3…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Magnetic and thermal transport properties of SrFe12O19 permanent magnets with anisotropic grain structure

et al. 2017

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“…So Tb-rich shells distribute clearly among GBs and then reduce the magnetic coupling of Nd 2 Fe 14 B grains and impede effectively the propagation of reversed domain walls through the magnetic phase grains. The better separation and decoupling of hard magnetic grains contribute to the enhancement of coercivity of Nd-Fe-B magnets [22][23][24]. The Cu and Tb enrichment in the grain boundaries shows that the grain boundary diffusion has been promoted with the help of Cu.…”

Section: Resultsmentioning

confidence: 99%

Microstructure evolution and coercivity enhancment of sintered Nd–Fe–B magnets by grain boundary diffusion with Cu aided TbF₃

Gao

Wei

et al. 2019

Mater. Res. Express

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Compared with the TbF 3 grain boundary diffusion (GBD) magnet, in this study, Cu aided TbF 3 GBD was applied to Nd-Fe-B magnets to further improve the coercivity. It is found that the coercivity increased sharply from 17.42 kOe to 25.43 kOe when the diffusion source is the mix powders of Cu and TbF 3 , higher than 21.25 kOe with single TbF 3 as the diffusion source. The wettability of the grain boundary phases were improved owing to the accumulation of Cu in grain boundary. The grains were uniformly enveloped by grain boundary phase with the help of Cu addition. The microstructure analysis indicated that the diffusion depth of Tb increased significantly due to the modified grain boundaries which offered better tunnels for the diffusion of Tb.

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“…To get rid of the dependence of HRE, in 2010, a diffusion alloy of Nd-Cu without any HRE element was demonstrated effective for coercivity enhancement, which started the research and development (R&D) of the second generation of sources based on light rare earth (LRE) elements [10]. Subsequently, in 2015, a cost-effective diffusion source of MgO was proposed [11]. It gave an idea that the non-rare earth (non-RE) compound or alloy can be used to modify the grain boundary (GB) phase as the next generation of diffusion source.…”

Section: Introductionmentioning

confidence: 99%

Grain Boundary Diffusion Sources and Their Coating Methods for Nd-Fe-B Permanent Magnets

Cao

et al. 2021

Metals

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Nd-Fe-B magnets containing no heavy rare earth (HRE) elements exhibit insufficient coercivity to withstand the demagnetization field at elevated temperatures. The grain boundary diffusion (GBD) process provides the best route to fabricate high-coercive Nd-Fe-B magnets with low consumption of expensive HRE resources. Here we give a special review on the grain boundary diffusion sources and their coating methods. Up to now, various types of grain boundary sources have been developed, starting from the earliest Tb or Dy metal. The HRE-M eutectic alloys were firstly proposed for reducing the cost of the diffusion source. After that, the diffusion sources based on light rare earth and even non rare earth elements have also been proposed, leading to new understanding of GBD. Now, the diffusion sources including inorganic compounds, metals, and alloys have been employed in the industry. At the same time, to coat the diffusion source on the magnets before diffusion treatment, various methods have been developed. Different from the previous review articles for GBD, this review gives an introduction of typical types of diffusion sources and their fabrication approaches. The effects of diffusion source on the microstructure and magnetic properties are summarized briefly. In particular, the principles and applicability of different coating approaches were discussed in detail. It is believed that this review can provide a technical guidance for the industry for designing the diffusion process and products meeting specific requirements.

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Properties improvement and structural optimization of sintered NdFeB magnets by non-rare earth compound grain boundary diffusion

Cited by 70 publications

References 22 publications

Magnetic and thermal transport properties of SrFe12O19 permanent magnets with anisotropic grain structure

Magnetic and thermal transport properties of SrFe12O19 permanent magnets with anisotropic grain structure

Microstructure evolution and coercivity enhancment of sintered Nd–Fe–B magnets by grain boundary diffusion with Cu aided TbF₃

Grain Boundary Diffusion Sources and Their Coating Methods for Nd-Fe-B Permanent Magnets

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Properties improvement and structural optimization of sintered NdFeB magnets by non-rare earth compound grain boundary diffusion

Cited by 70 publications

References 22 publications

Magnetic and thermal transport properties of SrFe12O19 permanent magnets with anisotropic grain structure

Magnetic and thermal transport properties of SrFe12O19 permanent magnets with anisotropic grain structure

Microstructure evolution and coercivity enhancment of sintered Nd–Fe–B magnets by grain boundary diffusion with Cu aided TbF3

Grain Boundary Diffusion Sources and Their Coating Methods for Nd-Fe-B Permanent Magnets

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Microstructure evolution and coercivity enhancment of sintered Nd–Fe–B magnets by grain boundary diffusion with Cu aided TbF₃