New Exchange-Coupled Manganese-Based Magnetic Materials - NEXMAG

NEXMAG project has managed to cover successfully scientific research and technological development in the field of rare earth-free permanent magnets. In addition to scientific highlights achieved on the MnAl system, a patent focused on a functional prototype has been filled, and the world-leading manufacturer of metal powders –Höganäs AB (Sweden)– has established an on-going industrial collaboration for implementation and up-scaling of some of NEXMAG’s results.

Permanent magnets (PMs) are a crucial element in several high-tech markets such as energy and transport sectors, medical technologies and a broad range of electronic products. In addition, PMs play a very important role in efforts focused on an increased use of low carbon technologies to ensure a high living standard. However, most of nowadays-technological PMs contain critical raw materials (rare-earths) as fundamental constituents and EU does not own the natural resources, which might result in a future bottleneck to the supply-chain.

NEXMAG (http://www.nexmag.net) has focused on the development of PM properties in Mn-based alloys: MnAl and MnBi. MnAl is an interesting PM candidate based on excellent theoretically predicted PM properties, low-density, low-cost and abundance of Mn and Al, together with good mechanical properties. MnBi offers excellent PM properties at high temperatures mainly intended for specific low-volume applications demanding high-magnetic performance under those conditions.

Highlights of the project can be summarized as follows:

• Development of PM properties in gas-atomized MnAl particles by nanostructuration with unprecedented short milling times by application of an “ultrafast-milling” method: 30 – 270 s (vs 20-30 h typically reported).
• Tuning microstructure and phase transformation by ultrafast-milling and cryomilling followed by a single-annealing step makes possible to go from a multiphase phase to a ferromagnetic single-phase MnAl system, with customized PM properties. This has been proven on bulk alloy, gas-atomized particles and melt-spun ribbons.
• Establishment of the correlation between morphological, microstructural and magnetic properties, which allows the development of high-coercive (above 5 kOe) isotropic nanocrystalline MnAl powder.
• Development of particulate and continuous MnBi thin films with a coercivity of 29 kOe at 500 K, counting among the largest reported ones for the MnBi system.
• Production of MnAl/metal nanocomposites with enhanced magnetization by matching complimentary properties of dissimilar materials.
• First reported results on the fabrication of MnAl/polymer composites for 3D-printing of novel permanent magnets.

These achievements have led to results of relevance from both scientific and technological points of view:

Dissemination:

• Invitation by the EU Commission to share its stand at the EuroScience Open Forum (ESOF)-2016 held in Manchester. A prototype using MnAl material was presented to the assistants.
• Presence in the media reporting the first time fabrication by IMDEA of an extruded continuous magnetic filament (12 m long) of MnAl for 3D-printing technologies:

https://www.azom.com/news.aspx?newsID=49377

https://www.nanowerk.com/news2/gadget/newsid=50681.php

Patent (Ref. EP16382224):

“System to obtain three-dimensional information from the magnetic field generated by an external permanent magnet source with applications in: detection of structural instabilities in civil engineering, advanced security ID cards and biomedical applications”.

Impact on EU industrial leadership:

• The results obtained in NEXMAG have led to an industrial project with the company Höganäs AB (Sweden). This projects focuses on the up-scaled production of a new generation of rare earth-free permanent magnet material.
• The advances done in the field of 3D-printing of metal/polymer composites have extended the research to an industrial collaboration with the company RAMEM S.A. (Spain).

Relevant publications:

1. Rial, P. Švec, E.M. Palmero, J. Camarero, P. Švec Sr. and A. Bollero, “Severe tuning of permanent magnet properties in gas-atomized MnAl powder by controlled nanostructuring and phase transformation”, Acta Mater. 157, 42 (2018).
2. M. Palmero, J. Rial, J. de Vicente, J. Camarero, B. Skårman, H. Vidarsson, P.-O. Larsson and A. Bollero, “Development of permanent magnet MnAlC/polymer composites and flexible filament for bonding and 3D-printing technologies”, Sci. Technol. Adv. Mater., 19 (1), 465 (2018).
3. Janotová, P. Švec Sr., P. Švec, I. Matʼko, D. Janičkovič, B. Kunca, J. Marcin and I. Škorvánek, “Formation of magnetic phases in rapidly quenched Mn-Based systems”, J. Alloys Compd. 749, 128 (2018).
4. E. Céspedes, M. Villanueva, C. Navío, F. J. Mompeán, M. García-Hernández, A. Inchausti, P. Pedraz, M. R. Osorio, J. Camarero and A. Bollero, “High coercive LTP-MnBi for high temperature applications: from isolated particles to film-like structures”, J. Alloys Compd. 729, 1156 (2017).

Project Details