Development of a prototype thermodynamic database for Nd-Fe-B permanent magnets

Abe, Taichi; Morishita, Masao; Chen, Ying; Saengdeejing, Arkapol; Hashimoto, Kiyoshi; Kobayashi, Yoshinao; Ohnuma, Ikuo; Koyama, Toshiyuki; Hirosawa, S.

doi:10.1080/14686996.2021.1936627

Cited by 13 publications

(3 citation statements)

References 104 publications

(164 reference statements)

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“…The structural properties of MOFs, such as porosity and pore tunability, as well as abundant H-bonding network or hydrophilic content, make them highly favorable for ideal proton conductors. − Since the presence of free [(CH 3 ) 2 NH 2 ] + cations in the pore channels plays an important role in the proton transfer process, the proton conductivity of JXUST-34 – 37 was investigated.…”

Section: Resultsmentioning

confidence: 99%

Highly Stable Rare Earth Metal–Organic Frameworks for Fluorescence Recognition of Folic Acid, Proton Conduction, and Magnetic Refrigeration

Wang,

Li,

Peng

et al. 2023

Inorg. Chem.

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Four new isostructural rare earth metal–organic frameworks (RE-MOFs) were synthesized and full characterized, namely, {[(CH)2NH2]3[RE2(BTDBA)2(HCOO)]·5H2O·2DMF} n (H4BTDBA = (4′,4′′′-(benzo[c][1,2,5]thiadiazole-4,7-diyl)bis([1,1′-biphenyl]-3,5-dicarboxylic acid); RE = Eu (JXUST-34), Gd (JXUST-35), Tb (JXUST-36), and Dy (JXUST-37)). The single-crystal structures analysis shows that JXUST-34–37 are chain-based three-dimensional structures. Importantly, JXUST-34 exhibits excellent water, organic solvents, and acid–base stability, which can be used as a fluorescence sensor for folic acid and Al3+ with detection limits of 0.02 mM and 0.05 μM, respectively. The presence of free [(CH)2NH2]+ cations in the channels can engage the proton carrier during proton conduction. JXUST-34–37 display good proton conductivity, and the conductivities vary with relative humidity and temperatures, among which JXUST-37 has the highest conductivity of 9.66 × 10–3 S·cm–1 at 60 °C and 98% RH. The magnetic studies show that the −ΔS m of JXUST-35 reaches 16.13 J kg–1 K–1 at 2 K and ΔH = 7 T. JXUST-34–37 show multifunctional properties of fluorescence sensing, high proton conductivity, and magnetic refrigeration, which provides a new clue for the development of fluorescent-responsive, magnetic-refrigerant, and proton-conductive RE-MOF materials.

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Section: Resultsmentioning

confidence: 99%

Highly Stable Rare Earth Metal–Organic Frameworks for Fluorescence Recognition of Folic Acid, Proton Conduction, and Magnetic Refrigeration

Wang,

Li,

Peng

et al. 2023

Inorg. Chem.

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“…The thermodynamics and phase equilibria of the Nd–Dy–Fe–B multicomponent system were first assessed by using the CALPHAD method. CALPHAD type thermodynamic databases were developed through a thermodynamic optimization process on the basis of all the available thermodynamic information for compounds and solution phases, and the critically assessed phase diagram data obtained from related studies [ 19 , 20 , 21 , 22 , 23 , 24 ]. In a thermodynamic database, the Gibbs energies of specific phases are described with different thermodynamic models.…”

Section: Resultsmentioning

confidence: 99%

Magnetic-Property Assessment on Dy–Nd–Fe–B Permanent Magnet by Thermodynamic Calculation and Micromagnetic Simulation

Dai

Wang

et al. 2022

Materials

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Heavy rare-earth (HRE) elements are important for the preparation of high-coercivity permanent magnets. A further understanding of the thermodynamic properties of HRE phases, and the magnetization reversal mechanism of magnets are still critical issues to obtain magnets that can achieve better performance. In this work, the Nd–Dy–Fe–B multicomponent system is investigated via the calculation of the phase diagram (CALPHAD) method and micromagnetic simulation. The phase composition of magnets with various ratios of Nd and Dy is assessed using critically optimized thermodynamic data. γ-Fe and Nd2Fe17 phases are suppressed when partial Nd is substituted with Dy (<9.3%), which, in turn, renders the formation of Nd2Fe14B phase favorable. The influence of the magnetic properties of grain boundaries (GBs) on magnetization reversal is detected by the micromagnetic simulations with the 3D polyhedral grains model. Coercivity was enhanced with both 3 nm nonmagnetic and the hard-magnetic GBs for the pinning effect besides the GBs. Moreover, the nucleation and propagation of reversed domains in core-shell grains are investigated, which suggests that the magnetic structure of grains can also influence the magnetization reversal of magnets. This study provides a theoretical route for a high-efficiency application of the Dy element, realizing a deterministic enhancement of the coercivity in Nd–Fe–B-based magnets.

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“…When the ambient temperature is below the melting point, the free Dy atoms will partially substitute Nd in the 2:14:1 phase within the Dy concentration range of 0-11.77%, and completely substitute Nd as the Dy concentration is above 11.77%. In this Nd 2 Fe 14 B-Dy interphase diffusion system, the quantities of Nd, Fe, B elements can be evaluated by the Dy concentration since the fixed chemical ratio of Nd, Fe, and B in Nd 2 Fe 14 B phase and thus the details of the free energy density of the 2:14:1 phase and liquid solution phase are described by thermodynamic sublattice-model with the following equation as [25]:…”

Section: Physical Modelmentioning

confidence: 99%

Grain boundary diffusion mechanism in Dy-diffused Nd–Fe–B sintered magnets

Dai,

Li,

Wang

et al. 2024

J. Phys. D: Appl. Phys.

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The grain boundary diffusion (GBD) is an effective method to enhance the thermal stability of the Nd-Fe-B based permanent magnets. For developing a high-performance magnet, it is critical to carry out a study on its mechanism, in order to reveal the distribution regulations of diffusion solutes and microstructural evolution. In the present work, the phase-field method is applied to investigate the thermodynamic feature and the heavy rare-earth Dy migration in a Dy-diffused Nd-Fe-B magnet during the GBD process. In the simulation process, the grain phase transformation and volume diffusion were taken into consideration and the effects of the diffusion mode, initial diffusion source concentration, grain size, and grain boundary width were explored in a set of magnet models with various grain sizes. An optimized fitting function was introduced to evaluate the solute distribution in grain boundaries and the effective diffusion coefficient. It is proven that the diffusion mode and the grain boundary width have significant impacts on the effective diffusion coefficient. The results provide a theoretical scheme concerning the quantitative evaluation of GBD efficiency based on the thermodynamic analysis.

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Development of a prototype thermodynamic database for Nd-Fe-B permanent magnets

Cited by 13 publications

References 104 publications

Highly Stable Rare Earth Metal–Organic Frameworks for Fluorescence Recognition of Folic Acid, Proton Conduction, and Magnetic Refrigeration

Highly Stable Rare Earth Metal–Organic Frameworks for Fluorescence Recognition of Folic Acid, Proton Conduction, and Magnetic Refrigeration

Magnetic-Property Assessment on Dy–Nd–Fe–B Permanent Magnet by Thermodynamic Calculation and Micromagnetic Simulation

Grain boundary diffusion mechanism in Dy-diffused Nd–Fe–B sintered magnets

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