Enhancement of coercivity in Al and Cu added Nd-Fe-B sintered magnets by high feld annealing

Akiya, Takahiro; Katô, Hiroaki; Sagawa, M.; Koyama, K.

doi:10.1088/1757-8981/1/1/012034

Cited by 14 publications

(12 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is noted that the (BH) max of LTP Experiment [15] MnBi dramatically increased from 1. Figure 4, the semi-theoretical (BH) max of LTP MnBi (10.9 MGOe) was found to be higher than that of Nd-Fe-B (2 MGOe) at 500 K [3]. This result suggests that LTP MnBi is a good permanent magnet for high temperature applications.…”

Section: Temperature Dependence Of Saturation Magnetization and Maximmentioning

confidence: 88%

“…In this way, it could be possible to increase the c/a ratio, thereby increasing M s . We previously reported that the ternary and quaternary systems of MnBi-Co and MnBi-Co-Fe show increased M s values of 730 emu/cm 3 and 810 emu/cm 3 , respectively, as compared to 714 emu/cm 3 for LTP MnBi [21].…”

Section: Electron Density Maps and C/a Ratio Dependence Of Magnetic Mmentioning

confidence: 94%

“…Therefore, Equation (4) was used below 250 K, and Equation (5) was used above 250 K to estimate (BH) max (T). Figure 4 shows the semi-theoretical (BH) max (T) and experimental (BH) max [8,9,13,20] for LTP MnBi, including experimental (BH) max (T) for Nd-Fe-B [3]. It is noted that the (BH) max of LTP Experiment [15] MnBi dramatically increased from 1.…”

Section: Temperature Dependence Of Saturation Magnetization and Maximmentioning

confidence: 99%

“…The magnetic moment at this ratio is 3.63 μ B /f.u., which is in good agreement with the above calculated moment. This work Powder [8] Powder with wax [9] Bonded [15] Sintered [9] Sintered [20] Directionally solidified [7] Nd-Fe-B [3] In order to explore any possibility of increasing the magnetic moment, we calculated the electron density and, thereby, find interstitial sites available for the doping element. Figure 6 shows the three-(3D) and two-dimensional (2D) electron density maps for (110), (100) and (001) planes.…”

Section: Electron Density Maps and C/a Ratio Dependence Of Magnetic Mmentioning

confidence: 99%

“…Although the Nd-Fe-B magnets exhibit desirable magnetic flux density (B), intrinsic coercivity (H ci and (BH) max ), a large negative temperature coefficient of H ci , a low Curie temperature (T c ) of 523 K [3] and limited supply are the critical drawbacks that need to be addressed. Motors for electric vehicles (EV) must reliably operate at temperatures up to 473 K. Therefore, the usage of Nd-Fe-B magnets is limited to a lower temperature than 473 K, due to their negative temperature coefficient of H ci and low Curie temperature.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Electronic Structure and Maximum Energy Product of MnBi

Park

Hong

Lee

et al. 2014

Metals

View full text Add to dashboard Cite

Abstract:We have performed first-principles calculations to obtain magnetic moment, magnetocrystalline anisotropy energy (MAE), i.e., the magnetic crystalline anisotropy constant (K), and the Curie temperature (T c ) of low temperature phase (LTP) MnBi and also estimated the maximum energy product (BH) max at elevated temperatures. The full-potential linearized augmented plane wave (FPLAPW) method, based on density functional theory (DFT) within the local spin density approximation (LSDA), was used to calculate the electronic structure of LPM MnBi. The respectively. The (BH) max at the elevated temperatures was estimated by combining experimental coercivity (H ci ) and the temperature dependence of magnetization (M s (T)). The (BH) max is 17.7 MGOe at 300 K, which is in good agreement with the experimental result for directionally-solidified LTP MnBi (17 MGOe). In addition, a study of electron density maps and the lattice constant c/a ratio dependence of the magnetic moment suggested that doping of a third element into interstitial sites of LTP MnBi can increase the M s . OPEN ACCESSMetals 2014, 4 456

show abstract

Section: Temperature Dependence Of Saturation Magnetization and Maximmentioning

confidence: 88%

Section: Electron Density Maps and C/a Ratio Dependence Of Magnetic Mmentioning

confidence: 94%

Section: Temperature Dependence Of Saturation Magnetization and Maximmentioning

confidence: 99%

Section: Electron Density Maps and C/a Ratio Dependence Of Magnetic Mmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Electronic Structure and Maximum Energy Product of MnBi

Park

Hong

Lee

et al. 2014

Metals

View full text Add to dashboard Cite

show abstract

Four-step eco-friendly energy efficient recycling of contaminated Nd2Fe14B sludge and coercivity enhancement by reducing oxygen content

Haider

Kim

Kang

2021

Sci Rep

View full text Add to dashboard Cite

Complete recycling of Nd2Fe14B sludge by chemical methods has gained significance in recent years, however, it is not easy to recycle highly contaminant sludge and obtain product with good magnetic properties. Herein we report a simple four-step process to recycle the Nd2Fe14B sludge containing ~ 10% of contaminants. Sludge was leached in H2SO4 and selectively co-precipitated in two steps. In the first co-precipitation, Al3+ and Cu2+ were removed at pH 6. Thereafter, in the second co-precipitation Fe2+ and RE3+ sulfates were converted to the Fe and RE hydroxides. By annealing at 800 °C RE and Fe hydroxides precipitates were converted to the oxides and residual carbon was oxidized to CO2. After the addition of boric acid, Fe and RE oxides were reduced and diffused to the (Nd-RE)2Fe14B by calciothermic reduction diffusion. Removal of CaO by washing with D.I. water in glove box reduced the oxygen content (~ 0.7%), improved crystallinity and enhanced the magnetic properties significantly. Coercivity increased more than three times (from 242.71 to 800.55 kA/m) and Mr value was also enhanced up to more than 20% (from 0.481 to 0.605 T). In this green process Na2SO4 and Ca(OH)2 were produced as by-product those are non-hazardous and were removed conveniently.

show abstract

Determination of Dy substitution site in Nd2−xDyxFe14B by HAADF-STEM and illustration of magnetic anisotropy of “g” and “f” sites, before and after substitution

Haider

Kang

Hong

et al. 2021

Sci Rep

View full text Add to dashboard Cite

Nd2Fe14B and Nd2−xDyxFe14B (x = 0.25, 0.50) particles were prepared by the modified co-precipitation followed by reduction–diffusion process. Bright field scanning transmission electron microscope (BF-STEM) image revealed the formation of Nd–Fe–B trigonal prisms in [− 101] viewing zone axis, confirming the formation of Nd2Fe14B/Nd2−xDyxFe14B. Accurate site for the Dy substitution in Nd2Fe14B crystal structure was determined as “f” site by using high-angle annular dark field scanning transmission electron microscope (HAADF-STEM). It was found that all the “g” sites are occupied by the Nd, meanwhile Dy occupied only the “f” site. Anti-ferromagnetic coupling at “f” site decreased the magnetic moment values for Nd1.75Dy0.25Fe14B (23.48 μB) and Nd1.5Dy0.5Fe14B (21.03 μB) as compared to Nd2Fe14B (25.50 μB). Reduction of magnetic moment increased the squareness ratio, coercivity and energy product. Analysis of magnetic anisotropy at constant magnetic field confirmed that “f” site substitution did not change the patterns of the anisotropy. Furthermore, magnetic moment of Nd2Fe14B, Nd2−xDyxFe14B, Nd (“f” site), Nd (“g” site) and Dy (“f” site) was recorded for all angles between 0° and 180°.

show abstract

Enhancement of coercivity in Al and Cu added Nd-Fe-B sintered magnets by high feld annealing

Cited by 14 publications

References 15 publications

Electronic Structure and Maximum Energy Product of MnBi

Electronic Structure and Maximum Energy Product of MnBi

Four-step eco-friendly energy efficient recycling of contaminated Nd2Fe14B sludge and coercivity enhancement by reducing oxygen content

Determination of Dy substitution site in Nd2−xDyxFe14B by HAADF-STEM and illustration of magnetic anisotropy of “g” and “f” sites, before and after substitution

Contact Info

Product

Resources

About