Coercivity increase of the recycled HDDR Nd-Fe-B powders doped with DyF3 and processed via Spark Plasma Sintering & the effect of thermal treatments

Awais Ikram; Muhammad Farhan Mehmood; Zoran Samardžija; Richard Sheridan; Muhammad Awais; Allan Walton; Saso Sturm; Spomenka Kobe; Kristina Zuzek Rozman

doi:10.3390/ma12091498

Coercivity increase of the recycled HDDR Nd-Fe-B powders doped with DyF3 and processed via Spark Plasma Sintering & the effect of thermal treatments

Awais Ikram, Muhammad Farhan Mehmood, Zoran Samardžija, Richard Sheridan, Muhammad Awais, Allan Walton, Saso Sturm, Spomenka Kobe, Kristina Zuzek Rozman

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Abstract

The magnetic properties of the recycled 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 OC) 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-ed 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 OC for 1 hour. The obtained HCi values of the blend magnet is 41% higher than the starting recycled HDDR powder and 17.5% higher than the SPS-ed processed magnet annealed at 750 OC for 1 hour. Prolonging the thermal treatment time to 6 hours and temperature conditions above 900 OC 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.

Original language	English
Article number	1497
Journal	Materials
Volume	12
Issue number	9
DOIs	https://doi.org/10.3390/ma12091498
Publication status	Published - 8 May 2019

Keywords

Coercivity
Doping DyF3
HDDR Nd2Fe14B
Rare Earth Permanent Magnets
Recycling
Spark Plasma Sintering

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10.3390/ma12091498

Ikram_et_al_Coercivity_increase_of_the_recycled_Materials_2019
Checked for eligibility: 20/05/2019 Ikram, A.; Mehmood, M.F.; Samardžija, Z.; Sheridan, R.S.; Awais, M.; Walton, A.; Sturm, S.; Kobe, S.; Žužek Rožman, K. Coercivity Increase of the Recycled HDDR Nd-Fe-B Powders Doped with DyF3 and Processed via Spark Plasma Sintering & the Effect of Thermal Treatments. Materials 2019, 12, 1498. https://doi.org/10.3390/ma12091498
Final published version, 6.41 MBLicence: Creative Commons: Attribution (CC BY)

https://www.mdpi.com/1996-1944/12/9/1498

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@article{b9699f4b54f447d38ade842876875882,

title = "Coercivity increase of the recycled HDDR Nd-Fe-B powders doped with DyF3 and processed via Spark Plasma Sintering & the effect of thermal treatments",

abstract = "The magnetic properties of the recycled 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 OC) 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-ed 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 OC for 1 hour. The obtained HCi values of the blend magnet is 41% higher than the starting recycled HDDR powder and 17.5% higher than the SPS-ed processed magnet annealed at 750 OC for 1 hour. Prolonging the thermal treatment time to 6 hours and temperature conditions above 900 OC 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.",

keywords = "Coercivity, Doping DyF3, HDDR Nd2Fe14B, Rare Earth Permanent Magnets, Recycling, Spark Plasma Sintering",

author = "Awais Ikram and Mehmood, {Muhammad Farhan} and Zoran Samard{\v z}ija and Richard Sheridan and Muhammad Awais and Allan Walton and Saso Sturm and Spomenka Kobe and Rozman, {Kristina Zuzek}",

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AU - Ikram, Awais

AU - Mehmood, Muhammad Farhan

AU - Samardžija, Zoran

AU - Sheridan, Richard

AU - Awais, Muhammad

AU - Walton, Allan

AU - Sturm, Saso

AU - Kobe, Spomenka

AU - Rozman, Kristina Zuzek

PY - 2019/5/8

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N2 - The magnetic properties of the recycled 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 OC) 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-ed 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 OC for 1 hour. The obtained HCi values of the blend magnet is 41% higher than the starting recycled HDDR powder and 17.5% higher than the SPS-ed processed magnet annealed at 750 OC for 1 hour. Prolonging the thermal treatment time to 6 hours and temperature conditions above 900 OC 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.

AB - The magnetic properties of the recycled 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 OC) 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-ed 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 OC for 1 hour. The obtained HCi values of the blend magnet is 41% higher than the starting recycled HDDR powder and 17.5% higher than the SPS-ed processed magnet annealed at 750 OC for 1 hour. Prolonging the thermal treatment time to 6 hours and temperature conditions above 900 OC 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.

KW - Coercivity

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KW - HDDR Nd2Fe14B

KW - Rare Earth Permanent Magnets

KW - Recycling

KW - Spark Plasma Sintering

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U2 - 10.3390/ma12091498

DO - 10.3390/ma12091498

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SN - 1996-1944

VL - 12

JO - Materials

JF - Materials

IS - 9

M1 - 1497

ER -

Coercivity increase of the recycled HDDR Nd-Fe-B powders doped with DyF3 and processed via Spark Plasma Sintering & the effect of thermal treatments

Abstract

Keywords

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