ORALS

SESSION: SISAMThuAM-R3 A: Magnetic materials today	Kobe International Symposium on Science of Innovative and Sustainable Alloys and Magnets (5th Intl. Symp. on Science of Intelligent and Sustainable Advanced Materials (SISAM))
Thu Oct, 24 2019 / Room: Dr. Christian Bernard
Session Chairs: Jean-Marie Dubois; Session Monitor: TBA

11:20: [SISAMThuAM01] Plenary
Magnetic Materials in the Current Global Environmental Issues
Jean-marie Dubois¹ ; Spomenka Kobe² ; ¹Institut Jean Lamour, Nancy, France; ²Josef Stefan Institute, Ljubljana, Slovenia;
Paper Id: 471 [Abstract]

Critical magnetic materials in the current global environmental issues have been one of the main research fields of Prof. Spomenka Kobe, who is being honored with the current symposium for her distinguished work and her lifetime achievements. These magnets, based on Nd-Fe-B alloys, are dominating the field already 36 years and their vital importance is nowadays mainly in e-mobility and e-energy power supply. Professor Kobe is the pioneer of modern magnetic materials in Slovenia. Over her career, she has achieved a number of breakthroughs in the area of these sustainable materials. The last to date is the reduction by a factor of at least 15 times less amount of heavy rare earth (HRE) needed to maintain high coercivity in engineered magnets with the largest possible magnetization, such as the ones used in wind generators or car engines. Nd-Fe-B magnets are at the forefront of sustainability. Due to the constant presence of possibly repeated restrictions on raw materials from the leading supplier, it is of vital importance to search for the ways how to avoid the next feasible crisis. In August 2019, the Chinese government cut the resource tax on companies mining heavy rare earths to 20 percent from 27 percent, as part of its efforts to support the vital sector and maintain the country’s dominance. Millions of end of life (EoL) devices, especially the wind generators, are a great source of raw materials. The new frontiers in Europe are now focused on the recycling of magnetic materials from tens of thousands of those magnets. By using the latest technologies developed in Europe, we can use short-loop circular economy routes to re-integrate the metals into new products for the European market1. The basic and applied research of the Magnetic Group (Department for Nanostructured Materials, Jožef Stefan Institute) in the field of Nd-Fe-B magnets, as well as possible alternatives, will also be briefly introduced and later on presented by the members of the group.

References:
SUSMAGPRO European Project Horizon 2020 programme of the European Commission (Coordinated by Prof. Carlo Burkhardt)

SESSION: SISAMThuPM2-R3 C: Processing	Kobe International Symposium on Science of Innovative and Sustainable Alloys and Magnets (5th Intl. Symp. on Science of Intelligent and Sustainable Advanced Materials (SISAM))
Thu Oct, 24 2019 / Room: Dr. Christian Bernard
Session Chairs: Carlo Burkhardt; Session Monitor: TBA

17:10: [SISAMThuPM212]
Effective Eectrochemical and Physical Reprocessing of Nd-Fe-B and Sm-Co Permanent Magnets, Approaching the Zero Waste Economy
Kristina Zuzek Rozman¹ ; Xuan Xu¹ ; Awais Ikram¹ ; Farhan Mehmood¹ ; Richard Sheridan² ; Allan Walton² ; Muhammad Awais² ; Anas Eldosoukey³ ; Spomenka Kobe⁴ ; Saso Sturm⁵ ; ¹Jozef Stefan Institute, Ljubljana, Slovenia; ²University of Birmingham, Birmingham, United Kingdom; ³Magneti LJubljana, d.d., Ljubljana, Slovenia; ⁴Josef Stefan Institute, Ljubljana, Slovenia; ⁵Head of Department for Nanostructured Materials, Ljubljana, Slovenia;
Paper Id: 189 [Abstract]

Currently, less than 1% of the rare-earth elements (REEs) that reach the end of their useful lives are recycled. This is a very small percentage, especially if we consider that the recycling of end-of-life (EoL) (Dy, Nd)-Fe-B magnets is an important strategy for reducing the environmental dangers associated with rare-earth mining, and overcoming the well-documented supply risks associated with the REEs. We report on possibilities of direct electrochemical recycling and electrochemical reprocessing of Nd-Fe(B)-based magnets. Previous attempts to deposit alloys of rare earths from solutions at mild temperatures have met little success. Excitingly, in this investigation, we were able to electrodeposit Nd-Fe from the 1-ethyl-3-methylimidizolium dicyanamide ([EMIM][DCA]) ionic liquid. We observed that Nd(III) cannot be reduced independently, although it can be co-deposited inductively as substrate with the addition of Fe(II), proven by electron-energy-loss spectroscopy. Further, we propose a new concept of recycling the sintered (Dy, Nd)-Fe-B magnets by directly recovering the (Dy, Nd)₂Fe₁₄B matrix phase. Via an electrochemical etching method, we are able to recover pure individual(Dy, Nd)₂Fe₁₄B grains that can be re-used for new types of magnet production. In terms of energy consumption, the proposed electrochemical recycling route is comparable to the established direct re-use methods. These direct methods are considered as the most economical and ecological ways for recycling the sintered (Dy, Nd)-Fe-B magnets. In the frame of physical reprocessing, we have successfully synthesised new magnets out of hydrogen-recycled stocks with contemporary sintering technique of pulsed electric current sintering. The SmCo₅ magnets for recycling were first decrepitated by hydrogen gas to produce the powder. The sample sintered at 900°C showed the best internal coercivity (jHc) of higher than 1500 kA/m with high remanence (Br) value of 0.47 T. The optimal SPS conditions yielded fully dense Nd-Fe-B magnets with the coercivity Hc = 1060 kA/m, which was boosted to 1160 kA/m after the post-SPS thermal treatment. The Br and Hc were tackled further, and increased applied pressures of 100-150 MPa resulted in Br = 1.01 T. Via the addition of DyF₃, 17.5% higher coercivity than the optimally SPS-ed magnet was obtained due to Dy substituting the Nd in the matrix Nd₂Fe₁₄B phase. We showed that with a fine tune of the SPS and post annealing, together with variations in Br and Hc, it is possible to revitalize the recycled Nd-Fe-B and Sm-Co magnets.

SESSION: SISAMThuPM3-R3 C: Processing cont.	Kobe International Symposium on Science of Innovative and Sustainable Alloys and Magnets (5th Intl. Symp. on Science of Intelligent and Sustainable Advanced Materials (SISAM))
Thu Oct, 24 2019 / Room: Dr. Christian Bernard
Session Chairs: Allan Walton; Session Monitor: TBA

18:15: [SISAMThuPM314]
A Success Story for more than 30 years: From Basic Research to the Industrial Innovation of Magnet Materials at Jožef Stefan Institute, Slovenia
Benjamin Podmiljsak¹ ; Kristina Zuzek Rozman¹ ; Saso Sturm² ; Spomenka Kobe³ ; ¹Jozef Stefan Institute, Ljubljana, Slovenia; ²Head of Department for Nanostructured Materials, Ljubljana, Slovenia; ³Josef Stefan Institute, Ljubljana, Slovenia;
Paper Id: 356 [Abstract]

At the Jožef Stefan Institute, a leading Slovenian research organisation in the field of natural sciences and technology, has conducted a systematic and consistent research of permanent magnets, tracing way back to the 1980s. In the last twenty years, this initiative has concentrated within the Department for Nanostructured Materials, within a research group specialised on magnetism, magnetic materials, and magnetic characterisation. The fact that a world-wide recognised research group on magnetic materials is present in a relatively small country of Slovenia is in many ways associated with an exceptionally high concentration of companies focused on the production and implementation of various types of permanent magnets. The research collaboration has always been motivated by the ongoing strategy of industry-driven basic research close to industrial innovation. It is therefore not surprising that during the rare earth crises approximately ten years ago, where Europe’s magnet industrial sector was nearly collapsing, all of the related Slovenian companies not only survived, but also strengthened their positon in the European region and worldwide. In this presentation, we will uncover historical backgrounds and current research strategies which led to the ongoing miracle of the magnet industry in Slovenia which will be shown through the prism of various success stories from basic-research driven industrial innovation, to the high impact implementation of the circular economy and problem-solving approaches during the production of different magnet types. These research strategies include, but are not restricted to, development of high-end corrosion protection for magnetic powder, failure analysis during the magnet production and the development of novel magnetic materials for state-of-the-art magnetic traction sensors for the robotic industry.

SESSION: SISAMFriAM-R3 D: Sustainable resources	Kobe International Symposium on Science of Innovative and Sustainable Alloys and Magnets (5th Intl. Symp. on Science of Intelligent and Sustainable Advanced Materials (SISAM))
Fri Oct, 25 2019 / Room: Dr. Christian Bernard
Session Chairs: George Hadjipanayis; Session Monitor: TBA

11:20: [SISAMFriAM01] Keynote
Enabling a circular economy ecosystem for NdFeB magnets: Which measures are needed and what is really feasible?
Carlo Burkhardt¹ ; Spomenka Kobe² ; Benjamin Podmiljsak³ ; ¹Pforzheim University, Pforzheim, Germany; ²Josef Stefan Institute, Ljubljana, Slovenia; ³Jozef Stefan Institute, Ljubljana, Slovenia;
Paper Id: 124 [Abstract]

Magnets are one of the most crucial materials necessary for modern Europe, as they are integral to energy conversion across the renewable energy and electric mobility sectors [1]. Unfortunately, even though the alloying constituents of NdFeB magnets have been classified as EU Critical Raw Materials and 90% are produced outside of the EU, there is still no circular economy to reuse and capture value for these types of materials [2]. With the prediction that the need for RE magnets will double in the next 10 years [3,4], this problem becomes even more urgent. At present, the only way to recover end of life (EOL) magnets from waste streams of electric and electronic equipment is by shredding and recycling by chemicals and pyrometallurgical routes, which is expensive and energy intensive [5]. Another problem is that the quality of the recollected materials varies significantly, especially with respect to alloying constituents and state of corrosion and employed corrosion protection, with no classification system for recyclate grades of EOL NdFeB magnets. To enable a circular economy ecosystem for NdFeB magnets, a whole range of measures is necessary: a) the development of an eco-labelling system for newly produced RE permanent magnets to clearly identify different magnets types and qualities in order to categorise the EOL NdFeB magnets by technical pre-processing requirements, b) using the highly effective HPMS process (Hydrogen Processing of Magnetic Scrap) for re-processing extracted materials directly from NdFeB alloy, c) better treatments to eliminate pre-processing residue which contaminates the HPMS process, d) upgrading the magnetic properties of EOL NdFeB magnets by tailoring the microstructure, phase ratio and phase composition, and e) developing industrial up-scalability, including thorough life cycle assessments. The feasibility of the above proposed measures will be discussed and illustrated with actual results generated in the EU-funded projects Maxycle and SUSMAGPRO. These projects will have a great impact by overcoming existing low recycling rates due to poor collection, high leakages of collected materials into non-suitable channels, and inappropriate interface management between logistics, mechanical pre-processing, and metallurgical metals recovery.

References:
[1] European Commission. Critical Raw Materials. http://ec.europa.eu/growth/sectors/raw-materials/specific-interest/critical_en (retrieved May 29, 2019).
[2] Sprecher, B., Xiao, Y.,Walton, A., Speight, J.D., Harris, I.R., Kleijn, R., Visser, G., Kramer, G.J.; Life Cycle Inventory of the Production of Rare Earths and the Subsequent Production of Nd-Fe-B Rare Earth Permanent Magnets. Environmental Science and Technology (2014) 3951-3958.
[3] Constantinides, S.; Market Outlook for Ferrite, Rare Earth and other Permanent Magnets. International Forum on Magnetic Applications, Technologies & Materials. 21-22 January 2016, Jacksonville, USA
[4]International Energy Agency. Energy, Climate Change & Environment: 2016 Insights
[5] DOI: 10.1021/es404596q

SESSION: SISAMFriAM-R3 D: Sustainable resources	Kobe International Symposium on Science of Innovative and Sustainable Alloys and Magnets (5th Intl. Symp. on Science of Intelligent and Sustainable Advanced Materials (SISAM))
Fri Oct, 25 2019 / Room: Dr. Christian Bernard
Session Chairs: George Hadjipanayis; Session Monitor: TBA

11:45: [SISAMFriAM02]
Transmission Electron Microscopy for efficient recycling of Nd-Fe-B permanent magnets
Saso Sturm¹ ; Awais Ikram² ; Xuan Xu² ; Spomenka Kobe³ ; Kristina Zuzek Rozman² ; Farhan Mehmood² ; ¹Head of Department for Nanostructured Materials, Ljubljana, Slovenia; ²Jozef Stefan Institute, Ljubljana, Slovenia; ³Josef Stefan Institute, Ljubljana, Slovenia;
Paper Id: 281 [Abstract]

The transition towards future green and e-mobility technologies, based on permanent magnets, is unavoidably linked to a stable supply of (heavy) rare earth elements. In the recent past, the transition towards green and e-mobility technologies has been hindered due to various geo-political and economic reasons. One promising way to address this problem is to develop strategies for various efficient magnet recycling and reprocessing routes that turn magnet waste into new functional magnets with little or negligible loss of overall magnetic performance [1]. The current recycling techniques, however, such as hydrogenation disproportionation desorption recombination (HDDR) processing, remelting, spark plasma sintering (SPS) and electrochemical deposition, inevitably perturb the desired microstructure. Detecting and understanding the underlying chemical and physical mechanisms is thus the key to optimize the overall magnetic performance of the recycled/reprocessed magnets. These mechanisms are typically associated with the structural/chemical properties of different crystal phases and defects, including dislocations, grains, and interphase boundaries. In recent years, state-of-the-art Transmission Electron Microscopy, which typically includes Scanning Transmission Electron Microscopy (STEM) with different spectroscopy techniques, such as Energy Dispersive X-ray Spectroscopy (EDXS) and Electron Energy-Loss Spectroscopy (EELS), has become an indispensable tool for characterization of rare earth-based permanent magnets. Transmission Electron Microscopy has become indispensable since it provides correlative structural and chemical information along with atomic-scale spatial resolution. In this presentation the above-described analytical techniques will be demonstrated against the most challenging research problems that were encountered during the development of two conceptually different recycling routes. In one approach, end-of-life Nd-Fe-B permanent magnets were first transformed in powder form by a HDDR process. The HDDR process was further used to fabricate initial dense reprocessed bulk magnet by spark plasma sintering (SPS) at different temperatures (ranging from 650⁰C to 850⁰C).Finally, a conventional heat treatment route at 750⁰C for 15 minutes was used on the bulk magnet that was fabricated. By applying advanced TEM, i.e. atomic-scale Z-contrast STEM, combined with EDXS and EELS, the resulting magnetic properties were critically assessed against various types of structural and compositional discontinuities down to the atomic-scale. We believe these discontinuities control the microstructure evolution during the SPS processing route. An alternative reprocessing route for Nd-Fe-based magnets that we have developed is based on electro-co-deposition of Nd and Fe from an ionic-liquid (1-ethyl-3-methylimidizolium dicyanamide) electrolyte. In order to reveal the deposition mechanism, the chemistry and phase composition of the deposit were investigated by means of analytical TEM. This showed that Nd(III) is reduced to Nd(0) during the electrodeposition process. Furthermore, we were able to confirm that the deposition of the Nd–Fe starts with the sole deposition of Fe, followed by the co-deposition of Nd–Fe. These new insights into the electrodeposition process represent an important step closer to efficient recycling of rare earths in metallic form at a mild temperature. This is a sustainable and economically viable route based on the green-chemistry approach, thus providing a genuine alternative to high-temperature molten-salt electrolysis.

References:
[1] This work was supported by the European Union's EU Framework Programme for Research and Innovation Horizon 2020 under Grant Agreement No 674973 (DEMETER).

SESSION: SISAMFriPM2-R3 F: Metastability & sustainability	Kobe International Symposium on Science of Innovative and Sustainable Alloys and Magnets (5th Intl. Symp. on Science of Intelligent and Sustainable Advanced Materials (SISAM))
Fri Oct, 25 2019 / Room: Dr. Christian Bernard
Session Chairs: Michael J. Zehetbauer; Session Monitor: TBA

16:45: [SISAMFriPM211] Invited
Towards High Coercivities in Heavy Rare Earth Free Nd-Fe-B Ribbons
Marko Soderžnik¹ ; Matic Korent² ; Urska Ročnik³ ; Boris Saje⁴ ; Spomenka Kobe⁵ ; ¹Jožef Stefan Institute, Ljubljana, Slovenia; ²Jozzef Stefan Institute, LJUBLJANA, Slovenia; ³Department for Nanostructured Materials, Jožef Stefan Institute, Ljubljana, Slovenia; ⁴Kolektor Magnet Technology GmbH, Essen, Germany; ⁵Josef Stefan Institute, Ljubljana, Slovenia;
Paper Id: 367 [Abstract]

Reasonable magnetic performance to weight ratio makes polymer-bonded magnets indispensable in automotive applications [i]. The magnetic powders, used for bonded magnets are mainly produced by the gas atomization and melt-spinning [ii]. Several magnetic powders can be used for such purposes, namely ferrites, SmCo, Sm-Fe-N, Nd-Fe-B and/or combinations of all of them. Since the magnetic powder is blended with non-magnetic binder, the remanent magnetization is diluting as the volume percent of the binder is increasing. Therefore, they can be classified as medium-performance isotropic bonded magnets. The coercivity of the magnet, however, is not related to the magnetic powder/non-magnetic binder ratio but to the chemistry and microstructural features. Melt-spun ribbons of Nd-Fe-B material are composed of randomly oriented Nd₂Fe₁₄B grains within the size of single magnetic domain [iii]. Therefore, they have a huge potential for higher coercivity compared to sintered Nd-Fe-B magnets in which a typical grain size is measured in microns [iv]. There exist several ways to improve the coercivity of Nd-Fe-B magnets. One way is to decouple the Nd2Fe14B grains by infiltration of low eutectic Nd-based alloys which we propose within this study. Detailed microstructural analyses showed that non-ferromagnetic Nd₇₀Cu₃₀ was successfully infiltrated between the grains, which prevented the physical contact between the grains leading to weaker intergrain exchange coupling. The results of such a process show more than 20 % improvement in coercivity while the remanence is increased as expected due to the lower amount of the ferro-magnetic phase. Significant increase in coercivity compensates lower remanence, and the energy product is also increased. In comparison to the basic powder, the coercivity at 150 °C is significantly improved, which enables these magnets to be used at a higher temperature.

References:
[i] J. J. Croat, 8-Major applications for rapidly solidified NdFeB permanent magnets, Woodhead Publishing Series in Electronic and Optical Materials (2018) 325–361.\n[ii] G. Sarriegui, J. M. Martín, M. Ipatov, A. P. Zhukov, J. Gonzalez, Magnetic Properties of NdFeB Alloys Obtained by Gas Atomization Technique, IEEE Trans. Magn. 54 (2018) 2103105.\n[iii] J. D. Livingston, Magnetic domains in sintered Fe-Nd-B magnets, J. Appl. Phys. 57 (1985) 4137–4139.\n[iv] M. Soderžnik, M. Korent, K. Žagar Soderžnik, M. Katter, K. Üstüner, S. Kobe, Acta Mat. 115 (2016) 178–284.

SESSION: SISAMSatPM1-R3 H: Characterisation	Kobe International Symposium on Science of Innovative and Sustainable Alloys and Magnets (5th Intl. Symp. on Science of Intelligent and Sustainable Advanced Materials (SISAM))
Sat Oct, 26 2019 / Room: Dr. Christian Bernard
Session Chairs: A. Lindsay Greer; Session Monitor: TBA

14:00: [SISAMSatPM105]
Correlative Characterization from Atoms to Magnetic Fields in Tb-Doped Nd-Fe-B Magnets
Kristina Zagar Soderznik¹ ; Saso Sturm² ; Andras Kovacs³ ; Aleksei Savenko⁴ ; Marko Soderžnik⁵ ; Rafal Dunin Borkowski⁶ ; Joachim Mayer⁷ ; Spomenka Kobe⁸ ; ¹Jozef Stefan Institute, Ljubljana, Slovenia; ²Head of Department for Nanostructured Materials, Ljubljana, Slovenia; ³Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Juelich, Germany; ⁴Thermo Fisher Scientific, Erlangen, Germany; ⁵Jožef Stefan Institute, Ljubljana, Slovenia; ⁶Forschungszentrum Jülich, Jülich, Germany; ⁷Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Jülich, Germany; ⁸Josef Stefan Institute, Ljubljana, Slovenia;
Paper Id: 347 [Abstract]

High coercivity Nd-Fe-B permanent magnets play an important role in the rapidly-growing renewable energy sector. To retain the coercivity at high operating temperatures, heavy-rare-earth elements (HRE), such as Dy and Tb, are added using the grain-boundary diffusion (GBD) process. The addition of HRE results in a significant improvement of the coercivity due to the increase of the intrinsic resistance to demagnetization. [1] In the present study, we report on the correlation between magnetic properties and the distribution of Tb₄O₇ in the Nd₂Fe₁₄B magnet. The Nd₂Fe₁₄B magnet was coated with Tb₄O₇ powder and annealed. During the annealing process, Tb diffused along grain boundaries (GB) into the outer parts of Nd-Fe-B grains, thus forming core-shell grains with the Tb-rich shell and Nd-Fe-B core. Magnetometry measurements were performed to observe the Tb concentration gradient from the surface of the magnet into its central part. It was found that the coercivity gradually decreases towards the central part where it is still around 30% higher when compared with the untreated magnet. [2,3] Although magnetic measurements clearly indicate the presence of Tb, it is not clear what the actual amount of Tb is in central regions of magnets or how they are distributed in the microstructure and if it is possible to distinguish the magnetisation flux between soft magnetic shells and hard magnetic cores. For that purpose, we applied the Cs-corrected STEM: FEI Titan 80-200 equipped with SuperX electron dispersive X-ray (EDX) spectrometer and electron energy-loss (EEL) spectrometer and FEI Titan 80-300 equipped with electron biprism to perform electron holography. As a complementary method, atom probe tomography (APT) was used using 3D atom probe LEAP 4000x HR. In order to analyse the core-shell region, a lamella was prepared from the representative core-shell grains and the interface between the shell and the core was examined using EELS and APT. Detailed line-scans and spectrum image maps were performed at this interface. The estimated width of the transition area between the shell and the core was 20 nm. Further studies focused on the electron holography of core-shell grains. The magnetic fluxes were within the core and the shell was determined. The thickness and the composition of the shell were determined as a function of the specimen position within the magnet.

References:
[1] P. J. McGuiness, et al., JOM 67 (2015) 1306-1317.
[2] M. Soderžnik, et al., Intermetallics 23 (2012) 158-162.
[3] M.Soderznik, et al., Acta Materialia 115 (2016) 278-284

SESSION: SISAMSatPM1-R3 H: Characterisation	Kobe International Symposium on Science of Innovative and Sustainable Alloys and Magnets (5th Intl. Symp. on Science of Intelligent and Sustainable Advanced Materials (SISAM))
Sat Oct, 26 2019 / Room: Dr. Christian Bernard
Session Chairs: A. Lindsay Greer; Session Monitor: TBA

14:25: [SISAMSatPM106] Invited
Consolidation and Characterization of Ferrite-Based Hybrid Magnets: Towards Rare-Earth-Free Magnets for Energy Storage
Petra Jenus¹ ; Andraz Kocjan² ; Claudio Sangregorio³ ; Michele Petrecca⁴ ; César De Julian Fernandez⁵ ; Blaž Belec⁵ ; Spomenka Kobe⁶ ; ¹Jožef Stefan Institute, Ljubljana, Slovenia; ²Jozef Stefan Institute, Ljubljana, Slovenia; ³ICCOM-CNR, Sesto Fiorentino, Italy; ⁴Dept. of Chemistry, University of Florence and ICCOM - CNR and INSTM, Sesto Fiorentino, Italy; ⁵IMEM-CNR, Parma, Italy; ⁶Josef Stefan Institute, Ljubljana, Slovenia;
Paper Id: 97 [Abstract]

In the last years, much effort has again been devoted to the research of ferrite-based permanent magnets due to the so-called rare-earth crisis.[1],[2] In particular, a quest to enhance ferrites' BHmax, is still underway.[3] Large BHmax values are found in magnets combining substantial magnetisation at remanence (Mr) with high coercivity. Both parameters are influenced by materials properties, such as crystalline and shape anisotropy and particle' size.<br />Here, the influence of composition, particle size, sintering conditions, and exposure to the external magnetic field before compaction on microstructure and consequently, magnetic properties of strontium ferrite (SFO)-based hybrid composites will be presented. <br />Powders' mixtures consisted of commercial SFO powder consisting of micron-sized, isotropic particles, or hydrothermally (HT) synthesised SFO with hexagonally-shaped platelets with a diameter of 1 micron and thickness up to 90 nm, and a soft magnetic phase in various ratios. Powders were sintered with spark plasma sintering (SPS) furnace. Starting powders and hybrid magnets were examined by means of phase composition (XRD) and microstructure (TEM, SEM). Their magnetic properties were evaluated with vibrating sample magnetometer (VSM), permeameter and by single-point-detection (SPD) measurements. <br />Depending on the concentration and composition of the soft phase, the MR of the composite can be altered. Application of the external magnetic field before the consolidation induces the anisotropy in commercial, and HT synthesised SFO, leading to the increase in the Mr of hybrid magnets [4]. Moreover, sintering with SPS promotes the alignment of HT synthesised SFO particles in the direction of the applied pressure, which is also the direction of SFOs' easy axis. Thus the enhancement in MR is perceived leading to the Mr/Ms higher than 0.8. Besides, after SPS, almost no grain growth was observed, which is beneficial for exploiting advantages of nanosized-induced phenomena also in bulk sintered samples. <br />This work received financial support from the European Commission through the project AMPHIBIAN (H2020-NMBP-2016-720853).

References:
[1] J. M. D. Coey, Permanent magnets: Plugging the gap, Scr. Mater., vol. 67, no. 6, pp. 524-529, 2012.\n[2] M. Stingaciu, M. Topole, P. McGuiness, and M. Christensen, Magnetic properties of ball-milled SrFe12O19 particles consolidated by Spark-Plasma Sintering, Sci. Rep., vol. 5, p. 14112, 2015.\n[3] R. Skomski and J. M. D. Coey, Magnetic anisotropy: How much is enough for a permanent magnet? Scr. Mater., vol. 112, pp. 3-8, 2016.\n[4] P. Jenuš et al., Ferrite-Based Exchange-Coupled Hard-Soft Magnets Fabricated by Spark Plasma Sintering, J. Am. Ceram. Soc., vol. 8, no. 37805, p. n/a-n/a, 2016

SESSION: SISAMSatPM2-R3 H: Characterization cont.	Kobe International Symposium on Science of Innovative and Sustainable Alloys and Magnets (5th Intl. Symp. on Science of Intelligent and Sustainable Advanced Materials (SISAM))
Sat Oct, 26 2019 / Room: Dr. Christian Bernard
Session Chairs: Petra Jenus; Session Monitor: TBA

15:55: [SISAMSatPM209]
Amorphous Al-Ce-Cu-Fe alloys: Glass formation and properties
Luka Kelhar¹ ; Spomenka Kobe² ; Jean-marie Dubois³ ; ¹JSI - K7 Dpt, Ljubljana, Slovenia; ²Josef Stefan Institute, Ljubljana, Slovenia; ³JSI - K7 Dpt for Nanostructured Materials, Ljubljana, Slovenia;
Paper Id: 275 [Abstract]

The Al-Cu-Fe system is well known, for it contains a quasicrystal, the ultimate degree of lattice complexity in an ordered solid. Susbtitution of Ce for Al atoms cancels the formation of the quasicrystals, but favours amorphisation upon rapid solidification from the liquid state. We have accordingly studied the solubility range of Ce in this alloy when replacing Al atoms. We have varied the Cu/Fe ratio at constant Al,Ce concentration as well. We found evidence that the local order in the glass is predominantly icosahedral, which matches the evidence of a very low glass transition temperature in the vicinity of the eutectic concentration known in the binary Al-Ce system. This interesting result can be exploited to prepare bulk specimens by spark plasma sintering, a technique that we used to produce centime-wide specimens. The magnetic properties were studied in a wide composition range and will be reported in the talk.

SESSION: SISAMSatPM2-R3 H: Characterization cont.	Kobe International Symposium on Science of Innovative and Sustainable Alloys and Magnets (5th Intl. Symp. on Science of Intelligent and Sustainable Advanced Materials (SISAM))
Sat Oct, 26 2019 / Room: Dr. Christian Bernard
Session Chairs: Petra Jenus; Session Monitor: TBA

16:45: [SISAMSatPM211]
Metal-Bonded Magnets Based on YCo5-Type Nanocrystals
Marko Soderžnik¹ ; Matic Korent² ; Kristina Zagar Soderznik³ ; Jean-marie Dubois⁴ ; Pelin Tozman⁵ ; M. Venkatesan⁶ ; Michael Coey⁷ ; Spomenka Kobe⁸ ; ¹Jožef Stefan Institute, Ljubljana, Slovenia; ²Jozzef Stefan Institute, LJUBLJANA, Slovenia; ³Jozef Stefan Institute, Ljubljana, Slovenia; ⁴JSI - K7 Dpt for Nanostructured Materials, Ljubljana, Slovenia; ⁵NIMS, Tsukuba, Japan; ⁶School of Physics and CRANN, Trinity College, Dublin, Ireland; ⁷School of Physics, Dublin, Ireland; ⁸Josef Stefan Institute, Ljubljana, Slovenia;
Paper Id: 342 [Abstract]

Metal-bonded magnets based on YCo₅-type nanocrystals [i] were produced by hot-compaction using a spark plasma-sintering device. Zn and Zn/Al metallic binders with a melting temperature of ̴ 420°C were employed to fabricate dense cylindrical magnets. Two different pressures were used for compaction. The pressure of 400 MPa provided a metal-bonded magnet with Vickers hardness (HV10) of 460 ± 20 Vickers. The temperature coefficients for remanence (α) and coercivity (β) were derived from magnetization vs. magnetic field measurements in the temperature range of 20°C – 150°C. Temperature coefficients α and β for the Zn/Al-bonded magnet pressed with 400 MPa were -0.055 %/°C and -0.201 %/°C, respectively. The field emission gun scanning electron microscope revealed a ‘core-shell’-type microstructure. The pure YCo_4.8Fe_0.2 phase was detected in the core region whereas the shell was enriched with non-ferromagnetic Zn or Zn/Al phases. The high-resolution transmission electron microscope revealed the presence of clusters with ̴ 20 nm YCo_4.8Fe_0.2 grains. In the Zn/Al-bonded magnet, fabricated at 400 MPa, the coercivity <i>µ₀H_ci</i>, remanent magnetization σ and energy product (BH)_max were 0.87 T, 39.3 Am²/kg and 23.4 kJ/m³, respectively.[ii]

References:
[i] P. Tozman, M. Venkatesan, J. M. D. Coey, Optimization of the magnetic properties of nanostructured Y-Co-Fe alloys for permanent magnets, AIP Adv. 6 (2016) 056016.\n[ii] M. Soderžnik, M. Korent, K. Žagar Soderžnik, J.-M. Dubois, P. Tozman, M. Venkatesan, J. M. D. Coey, S. Kobe, Hot-compaction of YCo4.8Fe0.2 nanocrystals for metal-bonded magnets, J. Mag. and Magn. Mat. 460 (2018) 401-408.