Effect of DyF3 and TbF3 additions on the coercivity enhancement in grain boundary diffusion processed Nd-Fe-B permanent magnets

Pratomo, Sri Bimo; Oktadinata, Herry; Pawawoi,

doi:10.1063/1.5038301

Cited by 10 publications

(4 citation statements)

References 13 publications

(46 reference statements)

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“…But there is an effective limit of DyF 3 doping to ≤ 2 wt.%, which not only gives the best magnetic properties, but it is also pivotal to REE criticality and conservation [1,2]. The controlled post-SPS thermal treatment in recycled HDDR system is very efficient for shorter durations and lower temperatures in developing higher coercivity and the core-shell structure, as compared to conventionally sintered magnets treated at elevated temperatures [21,22,23] or prolonged periods [33], due to ultrafine microstructure. For shorter periods, the formation of smaller RZ is important as only Dy forms core-shell structure by Nd substitution to Nd-O-F phase.…”

Section: Discussionmentioning

confidence: 99%

“…Several researchers have utilized rare earth fluorides (RE-F 3 ) as dopant or surface diffusion agents, to increase the coercivity in sintered magnets; with the coercivities reaching up to 2790 kA/m (35 kOe) [21,22,23,24,25,26,27,28,29,30,31,32] and in rapidly consolidated melt-spun ribbons, where coercivities reached up to 1990 kA/m [33,34]. On the contrary, no such research has been made on the HDDR Nd-Fe-B powders, which is a relatively cheap hydrogen reprocessing alternative for the EOL magnetic products [6].…”

Section: Introductionmentioning

confidence: 99%

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Coercivity Increase of the Recycled HDDR Nd-Fe-B Powders Doped with DyF3 and Processed via Spark Plasma Sintering & the Effect of Thermal Treatments

et al. 2019

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The magnetic properties of the recycled hydrogenation disproportionation desorption recombination (HDDR) Nd-Fe-B powder, doped with a low weight fraction of DyF3 nanoparticles, were investigated. Spark plasma sintering (SPS) was used to consolidate the recycled Nd-Fe-B powder blends containing 1, 2, and 5 wt.% of DyF3 grounded powder. Different post-SPS sintering thermal treatment conditions (600, 750, and 900 °C), for a varying amount of time, were studied in view of optimizing the magnetic properties and developing characteristic core-shell microstructure in the HDDR powder. As received, recycled HDDR powder has coercivity (HCi) of 830 kA/m, and as optimally as SPS magnets reach 1160 kA/m, after the thermal treatment. With only 1–2 wt.% blended DyF3, the HCi peaked to 1407 kA/m with the thermal treatment at 750 °C for 1 h. The obtained HCi values of the blend magnet is ~69.5% higher than the starting recycled HDDR powder and 17.5% higher than the SPS processed magnet annealed at 750 °C for 1 h. Prolonging the thermal treatment time to 6 h and temperature conditions above 900 °C was detrimental to the magnetic properties. About ~2 wt.% DyF3 dopant was suitable to develop a uniform core-shell microstructure in the HDDR Nd-Fe-B powder. The Nd-rich phase in the HDDR powder has a slightly different and fluorine rich composition i.e., Nd-O-F2 than in the one reported in sintered magnets (Nd-O-F). The composition of reaction zone-phases after the thermal treatment and Dy diffusion was DyF4, which is more abundant in 5 wt.% doped samples. Further doping above 2 wt.% DyF3 is ineffective in augmenting the coercivity of the recycled HDDR powder, due to the decomposition of the shell structure and formation of non-ferromagnetic rare earth-based complex intermetallic compounds. The DyF3 doping is a very effective single step route in a controlled coercivity improvement of the recycled HDDR Nd-Fe-B powder from the end of life magnetic products.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Coercivity Increase of the Recycled HDDR Nd-Fe-B Powders Doped with DyF3 and Processed via Spark Plasma Sintering & the Effect of Thermal Treatments

et al. 2019

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“…Unsur Dy dapat lebih cepat terdifusi ke matriks Nd-Fe-B dan menggantikan fasa kaya Nd. Penelitian Pratomo et al menunjukkan bahwa fasa kaya Nd semakin menghilang pada struktur mikro setelah proses difusi batas butir (Pratomo, Oktadinata, and Pawawoi 2017).…”

Section: Sumber: Dokumentasi Penelitianunclassified

PENINGKATAN KOERSIVITAS DAN REMANEN PADA MAGNET PERMANEN Nd-Fe-B DENGAN PROSES DIFUSI BATAS BUTIR

et al. 2019

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AbstrakSalah satu karakteristik magnet permanen tipe NdFeB adalah rentan terhadap kenaikan temperatur, seperti halnya yang terjadi pada aplikasi motor listrik. Penambahan unsur Dy pada tipe ini menjadi penting dalam usaha meningkatkan koersivitas dan temperatur curie. Akan tetapi, penambahan unsur Dy secara konvensional memerlukan biaya tinggi serta terjadinya penurunan nilai sifat remanen. Penelitian ini dilakukan dengan tujuan menambahkan unsur Dy untuk meningkatkan koersivitas magnet permanen dengan cara difusi batas butir dengan biaya yang lebih rendah dari pada cara konvensional dan tidak menurunkan sifat remanen secara signifikan. Penelitian ini dimulai dengan mengkarakterisasi dan mengamati struktur mikro awal dari magnet permanen tipe NdFeB dengan alat SEM-BSE dan VSM. Kemudian dilakukan proses difusi Dy dengan cara melapisi permukaan magnet dengan campuran DyF3-LiF dengan variasi perbandingan 0%-0% (tanpa lapisan); 44%-56% dan 100%-0%. Setelah itu, pada setiap variasi lapisan dilakukan perlakuan panas anil 750 o C dengan variasi waktu penahanan selama 2,5; 5; 7,5 dan 10 jam yang diikuti dengan post anil 550 o C selama 1 jam. Hasilnya, nilai koersivitas magnet meningkat dari 10,7 kOe menjadi 13,5 kOe pada sampel yang dianil pada variasi waktu penahanan 5 dan 7,5 jam. Sedangkan nilai remanen juga terjadi peningkatan dari 13,2 kG menjadi 14,7 kG pada sampel yang di anil dengan waktu penahanan selama 10 jam. Energi maksimum produk magnet pada sampel yang mengalami proses difusi (43,6 MGOe) lebih tinggi dari sampel yang tidak dilakukan difusi batas butir (43,1 MGOe).Kata kunci : difusi batas butir, dysprosium (Dy), koersivitas, magnet NdFeB, remanen AbstractOne of the characteristics of the NdFeB type permanent magnet was susceptible against the increase of temperature such as in electric motor applications. It is important to add Dy elements to increase coercivity and temperature curie. However, the addition of Dy elements conventionally requires high costs and reduces remanent significantly. The purpose of this study was to improve coercivity without a significant decrease in remanence by adding Dy elements with grain boundary diffusion. The microstructure of the NdFeB type permanent magnet was characterized and observed with SEM-BSE and VSM. Then, the surface of NdFeB type permanent magnet was coated with DyF3-LiF with variation ratio of 0%-0% (without coating); 44%-56% and 100%-0%. After that, each variation was annealed at 750 o C for holding time of 2.5; 5; 7.5 and 10 hours followed by post-annealing 550 o C for 1 hour. As a result, the magnetic coercivity increase from 10.7 kOe (initial magnet) to 13.5 kOe at variation of holding time of 5 and 7.5 hours. While the remanence also increased from 13.2 kG

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“…Lanthanides are important in modern technologies and industries because of their essential roles in permanent magnets, , lamp phosphors, − catalysts, , and rechargeable batteries as well as numerous other technologies . Lanthanide permanent magnets with high magnetic coercivities and excellent thermal properties represent the largest share of global rare earth element consumption at ∼30% of the total demand. , Nd 2 Fe 14 B, while exhibiting a thermal performance that is poorer than that of Sm x Co y magnets, is more economical than the former and thus the most common type of lanthanide-based magnet, and is widely used in electromechanical energy conversion devices. − Partially substituting Dy for Nd in Nd 2 Fe 14 B magnets increases the intrinsic room-temperature magnetic coercivity . In contrast to the increasing demand, perceived global supply shortages of these elements are a significant problem.…”

Section: Introductionmentioning

confidence: 99%

Syntheses and Characterization of Tetrazolate-Based Lanthanide Compounds and Selective Crystallization Separation of Neodymium and Dysprosium

et al. 2022

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Selective crystallization offers new opportunities for separating neodymium and dysprosium, which are considerably important in permanent magnets. Two water-soluble nitrogen-rich tetrazolate-based ligands, dtp2– (H2dtp = 2,3-di-1H-tetrazol-5-ylpyrazine) and H2ibt– [H3ibt = 4,5-bis(tetrazol-5-yl)imidazole], allow the separation of Nd3+ and Dy3+ through selective crystallization. The reactions of Ln3+ with the ligand Na2(dtp)·2H2O lead to two distinct phases, Na[Ln(dtp)(H2O)8](dtp)·H2O (Lndtp1; Ln = La–Pr) and [Ln(H2O)8](Hdtp)(dtp)·H2O (Lndtp2; Ln = Nd and Sm–Lu). Three different compound types, [Ln(H2ibt)2(H2O)6](H2ibt)·3(H2O) (Lnibt1; Ln = La or Ce), [Ln(H2ibt)(H2O)7](H2ibt)2·4(H2O) (Lnibt2; Ln = Pr or Nd), and [Ln(Hibt)(H2ibt)(H2O)4]·4+x(H2O) (Lnibt3; Ln = Sm–Lu), are obtained from reacting Ln3+ and Na(H2ibt)·3(H2O). Two different phases are observed for Nd(Lnibt2) and Dy(Lnibt3) in the system of H2ibt–, which leads to crystallization-based separation of Nd/Dy with a separation factor of 32 ± 0.7, 10 times higher than that of dtp2–, and a short separation time of 20 s (1 day for dtp2–). The higher performance of H2ibt– compared to that of dtp2– provides guidance for the rational design of water-soluble tetrazolate-derived ligands for selective crystallization.

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Effect of DyF3 and TbF3 additions on the coercivity enhancement in grain boundary diffusion processed Nd-Fe-B permanent magnets

Cited by 10 publications

References 13 publications

Coercivity Increase of the Recycled HDDR Nd-Fe-B Powders Doped with DyF3 and Processed via Spark Plasma Sintering & the Effect of Thermal Treatments

Coercivity Increase of the Recycled HDDR Nd-Fe-B Powders Doped with DyF3 and Processed via Spark Plasma Sintering & the Effect of Thermal Treatments

PENINGKATAN KOERSIVITAS DAN REMANEN PADA MAGNET PERMANEN Nd-Fe-B DENGAN PROSES DIFUSI BATAS BUTIR

Syntheses and Characterization of Tetrazolate-Based Lanthanide Compounds and Selective Crystallization Separation of Neodymium and Dysprosium

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