Novel recycling and reprocessing of permanent magnets

Project Information

OCARINA

Grant agreement ID: 101024046

DOI

10.3030/101024046

Project closed

EC signature date 18 March 2021

Start date 1 February 2022

End date 19 April 2024

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 150 040,32

EU contribution

€ 150 040,32

Coordinated by

INSTITUT JOZEF STEFAN
Slovenia

Periodic Reporting for period 1 - OCARINA (Novel recycling and reprocessing of permanent magnets)

Reporting period: 2022-02-01 to 2024-01-31

Summary of the context and overall objectives of the project

The rare-earth (RE) based Nd-Fe-B magnets make up the key components of electric motors and generators which operate at high energy efficiency standards. The RE elements like Neodymium (Nd), Praseodymium (Pr), Dysprosium (Dy), and Terbium (Tb) which are necessary constituents of these magnets are listed as critical raw materials. Since the End Of Life (EOL) Nd-Fe-B magnets consist of 31-32 wt.% of REs so their recycling becomes necessary to reduce the supply-chain risks of these critical elements. It can also lead to the reduction of environmental hazards from mining of REs. The current magnet recycling is energy-intensive and economically not viable.

The low-cost and eco-friendly magnet recycling technique developed in this MSCA project will enable the self-sufficiency of the RE magnet manufacturing industries in terms of supply-chain. It will boost the efficient use of resources and will reduce the cost of magnet manufacturing and the overall cost of electric motors and wind turbine generators. by moving to a clean, circular economy. This will encourage the society for widespread use of e-mobility powered by clean electric and wind power and will to the transition to a clean and circular economy.

The overall objective is to introduce a new recycling route for EOL magnets by producing individual grains of Nd2Fe14B phase from scrap magnets and re-engineering them from the inside out. This will also advance the theory of coercivity in Nd-Fe-B magnets and produce highly demagnetization-resistant grain boundaries with ideal interfaces between the Nd2Fe14B phase and the grain boundary.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

An economical and eco-friendly magnet recycling method was developed based on the extraction of hard magnetic Nd2Fe14B grains by selective leaching of Nd or rare-earth (RE) rich phase. At first electrochemical extraction of grains was carried out but yield of grain extraction and leaching rate of the RE-rich phase was low, so the magnet was pulverized by hydrogen decrepitation and grains were extracted by treating the powder with citric acid. For comparison, nitric acid was used to investigate selectivity towards the leaching of the RE-rich phase.
However, the nitric acid was found to have no selectivity for the Nd-rich phase, and exposure to nitric acid results in a structurally damaged Nd2Fe14B matrix phase as evidenced by the SEM (Fig. 1)


The yield obtained by this process was comparatively higher than the electrochemical process and the process time was 15 minutes which was further lowered to 5 minutes by ultrasonication. Results of the SEM (Fig. 1 and 2) microstructural investigation and ICP-MS compositional analysis (Fig. 3 and 4) and magnetic measurements (Fig. 5) of the leached Nd-Fe-B powders confirm that citric acid can indeed selectively leach away the RE-rich phase while preserving the Nd2Fe14B matrix phase concerning its magnetic moment/mass values. The work was published in MDPI Materials in 2023.

The extracted Nd2Fe14B grains were blended with Nd70Cu30 eutectic alloy and consolidated with spark plasma sintering (SPS). The low-eutectic alloy with the composition Nd70Cu30 was prepared through arc melting of stoichiometric amounts of the metal neodymium and copper, followed by melt spinning and milling. The Nd-Cu was added (0-30 wt.% )to study its impact on the microstructure and magnetic properties of magnets re-engineered via Spark Plasma Sintering (SPS). Notably, Nd-Cu prevented the decomposition of the Nd2Fe14B matrix phase due to Joule overheating at particle contacts during SPS. A theoretical density of 7.6 g/cm³ was achieved with a 10 wt.% Nd-Cu addition.

Discussions are being carried out with industrial parties like KOLEKTOR through Boris Saje and Magneti Ljubljana through Matej Zaplotnik to test this protocol and to make novel magnets from recovered grains

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Novel protocol to recycle EOL Nd-Fe-B magnets was developed in which the RE-rich phase was leached out in an optimized leaching time. The studies and research performed in this project could create new marketing opportunities in recycling techniques, and strengthen the competitiveness and growth of companies by reducing the risk of the supply chain of critical raw materials. The research activities in this project were aimed at finding eco-friendly and cost-effective solutions for magnet recycling to address environmental, industrial, and social needs.


The work carried out on this project contributes to the European Green Deal policy for the Net-Zero Age since it emphasizes the utilization of EOL magnetic scrap to make new magnets for wind turbines and electric vehicle applications. The current recycling methods and extraction of rare earths from mines pose a negative impact to the environment. The mining of rare earths and the current recycling methods are energy-intensive, and this also raises the cost of manufacturing new magnets. The low-cost recycling methods developed in this project can lead to meeting the target of phasing out fossil fuel-based vehicles and power generation by 2050. There can be a significant impact on policy-making regarding critical raw materials and legislation can be passed to direct the electric vehicle and magnet manufacturers to use rare-earth-based scrap as raw materials instead of throwing them in landfills.

The work carried out on this project contributes to sustainability within the critical raw materials act. Since rare earths have been listed as critical raw materials due to their scarcity and geopolitical supply risks, hence, building up low-cost infrastructure for magnet recycling is necessary. The recycling protocol developed in this project can help in developing such infrastructure which will tend to reduce the supply chain risks and magnet manufacturing costs to fulfill the rising demands of e-mobility and clean energy. The short loop recycling method of Nd-Fe-B magnets developed in this project will reduce dependence on the mining of rare earth minerals for raw materials reducing the carbon footprint. The recycling process developed in this project uses no harmful chemicals so it is more eco-friendly.

Variation in the composition of (a) TMs (Fe+Co) and (b) REs (Nd+Pr) with leaching time

BSE-SEM images of (a) HPMS and leached powders in, (b) 5, (c) 15 and (d) 45 min

(a) Magnetic hysteresis loops of powder samples, (b) the effect of leaching time on magnetization

(a) Magnetic hysteresis loops of powder samples, (b) the effect of leaching time on magnetization

BSE-SEM images of Nd-Fe-B Powder leached with (a)-(d) citric acid and (e) and (f) nitric acid