Coercivity Increase of the Recycled HDDR Nd-Fe-B Powders Doped with DyF<sub>3</sub> and Processed via Spark Plasma Sintering & the Effect of Thermal Treatments
The magnetic properties of the recycled hydrogenation disproportionation desorption recombination (HDDR) Nd-Fe-B powder, doped with a low weight fraction of DyF<sub>3</sub> nanoparticles, were investigated. Spark plasma sintering (SPS) was used to consolidate the recycled Nd-Fe-B powder...
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doaj-42bb66ee9f934e09934dacab359cb3222020-11-25T00:48:17ZengMDPI AGMaterials1996-19442019-05-01129149810.3390/ma12091498ma12091498Coercivity Increase of the Recycled HDDR Nd-Fe-B Powders Doped with DyF<sub>3</sub> and Processed via Spark Plasma Sintering & the Effect of Thermal TreatmentsAwais Ikram0M. Farhan Mehmood1Zoran Samardžija2Richard Stuart Sheridan3Muhammad Awais4Allan Walton5Saso Sturm6Spomenka Kobe7Kristina Žužek Rožman8Department for Nanostructured Materials, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, SloveniaDepartment for Nanostructured Materials, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, SloveniaDepartment for Nanostructured Materials, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, SloveniaSchool of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT, UKSchool of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT, UKSchool of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT, UKDepartment for Nanostructured Materials, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, SloveniaDepartment for Nanostructured Materials, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, SloveniaDepartment for Nanostructured Materials, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, SloveniaThe magnetic properties of the recycled hydrogenation disproportionation desorption recombination (HDDR) Nd-Fe-B powder, doped with a low weight fraction of DyF<sub>3</sub> 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 DyF<sub>3</sub> 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 (H<sub>Ci</sub>) of 830 kA/m, and as optimally as SPS magnets reach 1160 kA/m, after the thermal treatment. With only 1−2 wt.% blended DyF<sub>3</sub>, the H<sub>Ci</sub> peaked to 1407 kA/m with the thermal treatment at 750 °C for 1 h. The obtained H<sub>Ci</sub> 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.% DyF<sub>3</sub> 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-F<sub>2</sub> 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 DyF<sub>4</sub>, which is more abundant in 5 wt.% doped samples. Further doping above 2 wt.% DyF<sub>3</sub> 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 DyF<sub>3</sub> 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.https://www.mdpi.com/1996-1944/12/9/1498rare earth permanent magnetsHDDR Nd<sub>2</sub>Fe<sub>14</sub>Brecyclingspark plasma sinteringcoercivitydoping DyF<sub>3</sub> |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Awais Ikram M. Farhan Mehmood Zoran Samardžija Richard Stuart Sheridan Muhammad Awais Allan Walton Saso Sturm Spomenka Kobe Kristina Žužek Rožman |
spellingShingle |
Awais Ikram M. Farhan Mehmood Zoran Samardžija Richard Stuart Sheridan Muhammad Awais Allan Walton Saso Sturm Spomenka Kobe Kristina Žužek Rožman Coercivity Increase of the Recycled HDDR Nd-Fe-B Powders Doped with DyF<sub>3</sub> and Processed via Spark Plasma Sintering & the Effect of Thermal Treatments Materials rare earth permanent magnets HDDR Nd<sub>2</sub>Fe<sub>14</sub>B recycling spark plasma sintering coercivity doping DyF<sub>3</sub> |
author_facet |
Awais Ikram M. Farhan Mehmood Zoran Samardžija Richard Stuart Sheridan Muhammad Awais Allan Walton Saso Sturm Spomenka Kobe Kristina Žužek Rožman |
author_sort |
Awais Ikram |
title |
Coercivity Increase of the Recycled HDDR Nd-Fe-B Powders Doped with DyF<sub>3</sub> and Processed via Spark Plasma Sintering & the Effect of Thermal Treatments |
title_short |
Coercivity Increase of the Recycled HDDR Nd-Fe-B Powders Doped with DyF<sub>3</sub> and Processed via Spark Plasma Sintering & the Effect of Thermal Treatments |
title_full |
Coercivity Increase of the Recycled HDDR Nd-Fe-B Powders Doped with DyF<sub>3</sub> and Processed via Spark Plasma Sintering & the Effect of Thermal Treatments |
title_fullStr |
Coercivity Increase of the Recycled HDDR Nd-Fe-B Powders Doped with DyF<sub>3</sub> and Processed via Spark Plasma Sintering & the Effect of Thermal Treatments |
title_full_unstemmed |
Coercivity Increase of the Recycled HDDR Nd-Fe-B Powders Doped with DyF<sub>3</sub> and Processed via Spark Plasma Sintering & the Effect of Thermal Treatments |
title_sort |
coercivity increase of the recycled hddr nd-fe-b powders doped with dyf<sub>3</sub> and processed via spark plasma sintering & the effect of thermal treatments |
publisher |
MDPI AG |
series |
Materials |
issn |
1996-1944 |
publishDate |
2019-05-01 |
description |
The magnetic properties of the recycled hydrogenation disproportionation desorption recombination (HDDR) Nd-Fe-B powder, doped with a low weight fraction of DyF<sub>3</sub> 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 DyF<sub>3</sub> 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 (H<sub>Ci</sub>) of 830 kA/m, and as optimally as SPS magnets reach 1160 kA/m, after the thermal treatment. With only 1−2 wt.% blended DyF<sub>3</sub>, the H<sub>Ci</sub> peaked to 1407 kA/m with the thermal treatment at 750 °C for 1 h. The obtained H<sub>Ci</sub> 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.% DyF<sub>3</sub> 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-F<sub>2</sub> 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 DyF<sub>4</sub>, which is more abundant in 5 wt.% doped samples. Further doping above 2 wt.% DyF<sub>3</sub> 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 DyF<sub>3</sub> 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. |
topic |
rare earth permanent magnets HDDR Nd<sub>2</sub>Fe<sub>14</sub>B recycling spark plasma sintering coercivity doping DyF<sub>3</sub> |
url |
https://www.mdpi.com/1996-1944/12/9/1498 |
work_keys_str_mv |
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