(KOBE) INTL. SYMP. ON SCIENCE OF INNOVATIVE AND SUSTAINABLE ALLOYS AND MAGNETS

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.

Many therapeutic fields use implantable medical devices. This usually involves replacing a whole organ or a defective part of an organ by a biocompatible substitute. Knee prostheses, hip prostheses, dental prostheses and breast prostheses are among the best-known implantable medical devices. These biomedical materials are intended to be in long-term contact with biological materials. Cells contained in these biological materials detect and react to their environment. This mechano-transduction process greatly influences the physiological processes involved in development, health and disease. The mechanical function of cells impacts, among other things, the processes of healing, differentiation of stem cells, and cancer metastases [1]-[4]. The impact of the contact forces developed between the implant and the biological tissue on changes in the behavior of the tissue has not yet received much attention from the scientific community. This is mainly because the mechanical constitutive equation of biological tissues is not available due to their complex microstructure. We believe that biological tissues can be considered as micromorphic media. It is actually the most achieved phenomenological top-down approach. The effectiveness of this modelling is investigated by considering the examples of an implant/bone system and a stent/artery system. The presented study is completely numerical and supported by clinical observations.

In this presentation, the current trends and the latest developments in the field of the permanent magnets will be reviewed. Two powerful factors shape the current developments of the rare-earth magnets, the rapidly growing demand for high-energy-density magnets operating at 150 – 200 °C and the echo of the 2010-11 rare earths supply crisis. The incentive for increasing the operating temperature of the Nd-Fe-B magnets using smaller amounts of heavy rare earths has resulted in the development of localized alloying techniques, in which Dy or Tb are delivered to the exact locations in the magnet through grain-boundary infiltration. Moreover, the same infiltration approach as well as a more refined micro-alloying now allows for sintered and die-upset Nd-Fe-B magnets exhibiting a coercivity as high as 20 kOe without any use of the heavy rare earths. To address the sustainability challenge, researchers and manufacturers are also partially replacing even the light rare earths, Nd and Pr, with the more abundant Ce and La. The Sm-Co magnets had their maximum energy product recently increased to 35 MGOe, primarily through a greater Fe substitution for Co. The ThMn12-type compounds, notable for their naturally low rare earth content see a renewed interest. Although 1:12 alloys with excellent fundamental properties – rivaling those of the Nd2Fe14B compound – have been synthesized and processed by different approaches ranging from sintering followed by infiltration to mechanochemistry, there has not yet been a breakthrough in preparation of practical 1:12 magnet. Such breakthrough apparently happened this year for the most developed rare-earth-free permanent magnet material (not counting the prohibitively expensive FePt). Magnetic-field annealing of a properly alloyed MnBi alloy, after it has been subjected to melt spinning and warm compaction, produced magnets exhibiting a maximum energy product of 11-12 MGOe, which is 40% greater than those obtained via the traditional powder metallurgy and which must be sufficient to replace the lower grades of the rare earth magnets.

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.

Nanoporous gold (NPG) can be produced by dealloying [1], a process in which the less noble elements in an alloy are chemically or electrochemically dissolved into an electrolyte, leaving on the surface the noble element to form ligaments and pores with size of tens or hundreds of nanometers. The dealloying process can be performed from a crystalline or an amorphous precursor [2, 3] with a consequent change in the dealloying mechanism. This way, when amorphous precursors are used, ligaments result to be highly rough with nanometric holes that enable excellent optical and electrochemical properties. Nanoporous gold is produced in a large variety of morphologies and it can be modified by electrodeposition of Au nanoparticles on the ligament surface in order to enhance electrochemical or SERS (Surface Enhanced Raman Spectroscopy) activity.
In this work, the production of nanoporous gold via dealloying of Au-based amorphous precursors is outlined and compared with nanoporous gold produced from Fe-Au system, an innovative precursor that can allow a sensitive reduction in NPG production costs. For this purpose, Au-based amorphous alloys and Fe-Au crystalline alloys were chemically dealloyied in a solution of 2, 5, 10 and 14.4 M HNO₃ plus 0.5 M HF for different times. The surface morphology of de-alloyed samples was observed by scanning electron microscopy.
SERS measurements were performed on NPG samples synthesised following different routes in order to determine the morphology leading to the higher SERS activity. Bipyridine and melamine were used as probe molecules achieving detection limit down to 10-14 M. The enhancement of SERS effect on nanoporous gold is attributed to the localized enhanced electromagnetic fields around nanopores and to the electromagnetic coupling between ligaments. Ligaments constituted by several nanocrystals with random orientation and separated by grain boundaries leads to further enhancement of the SERS effect.

The equilibrium phase diagram does not reflect the real structure of Fe-Ga alloys neither in the as cast state nor after annealing followed by air-cooling or furnace-cooling. Functional properties of the Fe-Ga alloys are extremely sensitive to particular details of the phase transition from the metastable (as-cast, as-quenched) state with A2 or D0₃ structures with positive magnetostriction to the equilibrium state with L1₂ structure and negative magnetostriction. They are also sensitive to short range ordering of the A2 metastable phase including the formation of local martensite-like structures.
In the present study, we have investigated the time-dependence and temperature-dependence of the transition of as-cast metastable Fe-(9-33at.%)Ga ‘Galfenol’ alloys to the equilibrium state along with corresponding changes in their functional properties and anelastic effects that accompany these transitions. To characterize such a time-temperature-transition diagram we used both long-time isochronal annealing (up to 300 hrs) and instant heating treatments with different temperature protocols. In-situ neutron diffraction at instant heating-cooling and isochronal annealing, XRD, DSC, VSM, SEM-EBSD, Mössbauer and mechanical spectroscopy techniques were used to study first and second order phase transitions, structure, and functional properties of Galfenols.

Novel processing technologies for metals such as 3D printing require the application of high heating and cooling rates and ideally the use of isotropic materials. The glass-forming alloys are good candidates for such applications. We directly determine the thermodynamic fragility index of two metallic glasses (Mg₆₅Cu₂₅Gd₁₀ and Au₄₉Cu_26.9Si_16.3Ag_5.5Pd_2.3) from fictive temperature shifts induced by a variation of the quenching rate using fast differential scanning calorimetry (FDSC). Recent chip calorimeters are able to achieve the cooling rates necessary to perform such an evaluation. For the Mg₆₅Cu₂₅Gd₁₀ and Au₄₉Cu_26.9Si_16.3Ag_5.5Pd_2.3 metallic glasses studied, we find very good agreement of the kinetic fragility index with literature data obtained by conventional calorimetry and rheology. We also applied ultra-fast chip calorimetry in combination with time-resolved micro-diffraction directly recorded with fast pixel array detectors. This way we can investigate the structural modifications of bulk metallic glasses (BMGs), in-situ, on ultra-fast temperature changes. Combining the very high time resolution of structural and calorimetric data acquisition, we investigated the mechanisms and the kinetics of the metastable phase transformations of this group of materials at ultra-high rates of temperature change. The understanding of the kinetic transition paths of- to date still unknown- metastable material states is the foundation for the development of tailored thermomechanical treatment routes towards novel applications of BMGs.

Cu-Ni alloys have gained interest as bulk and nanoparticles (NPs) primarily due to their catalytic and magnetic properties. Different modeling methods employed before for computations of chemical-order were limited to Cu-Ni NPs consisting of few hundred atoms. The present study uses the highly efficient statistical-mechanical free-energy concentration expansion method (FCEM [1]), combined with coordination-dependent bond-energy variations (CBEV [2]), and the coarse-grained layer (CGLM [3]) models for the case of CuNi truncated-octahedrons (TO). This quite efficient semi-analytical methodology enables the exploration of chemical-order configurations and transitions between them in much larger particle sizes and over broad ranges of composition and temperature. Furthermore, in spite of free-atom electronic-relaxation contributions to transition-metal cohesive-energies, numerous studies have misused the latter instead of using genuine bond-energies in modeling NP properties [4].Using the corresponding modified cohesive-energies, and depending strongly on size and composition, the following findings regarding chemical-order configurations are obtained: due to the CBEV, asymmetric Janus-like configuration (JA) is expected to be the most stable for all compositions only for the 201, 586 and 1029-atom TO sizes. At elevated temperatures, they transform into quasi-mixed configurations (QM). For larger TOs, core-shell (CS) configurations start to stabilize in narrow ranges of elevated temperatures and intermediate compositions, and become progressively stable at increasingly wider ranges. Three types of transitions are revealed: JA-CS, CS-QM, and JA-QM, yielding the first comprehensive Cu-Ni nanophase-separation diagrams. The use of unmodified cohesive energies leads to significantly altered transition temperatures, demonstrating the importance of the commonly ignored modification. Preliminary results for Cu-Ni-Pd TOs reveal a considerable impact of Pd alloying on the chemical-order diagrams, particularly the suppression of JA in favor of CS configurations.

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.
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.
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.
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.
This work received financial support from the European Commission through the project AMPHIBIAN (H2020-NMBP-2016-720853).

Establishing a 3D electrically percolating network in an insulating ceramic matrix is key to numerous engineering and functional applications. Using hydrophobic carbon nanofillers like graphene or carbon nanotubes is tempting, but still results in suboptimal performance due to processing challenges including colloidal instabilities in aqueous media.
Here, we demonstrate an alternative, sustainable way by a small addition of cellulose nanofibers (CNF), which render highly homogeneous aqueous ceramic dispersions due to the increased hydrophilicity character and facilitates green machining of the consolidated green bodies. During sintering the natural CNF`s [1] can be in situ transformed into graphene-like sheets connected to a 3D network enhancing both the transport and the mechanical properties of sintered Al2O3 and yttria-stabilised ZrO2 (YSZ) ceramic matrices [2] [3]. The advantage presented here is the colloidal processing in water of CNF hydrogels with ceramic powder suspensions, which guarantees uniform and homogeneous properties from the bulk scale down to the nanoscale. The network architecture of the few-layered graphene (FLG) sheets also permits the decoupling of electrical and thermal conductivities, which represents a major obstacle in attaining efficient thermoelectric materials. The microstructure of the resulting materials was characterised by electron microscopy and spectroscopy (STEM/EELS), while the electrical and dielectrical properties were analysed by impedance spectroscopy. The materials showed high electrical conductivity at only 2 % initial CNF content, while the FLG-YSZ nanocomposites exhibited mixed ionic-electronic conduction at a��1% CNF, which is interesting for electrode materials in solid-oxide fuel cells.
Besides the transport properties, the incorporated CNF improve the (green) mechanical properties and also enable the use of technologically important machining methods for electro-conductive ceramics. We envisage that our results can advance the processing science and technology to provide the improved hierarchical graphene composite materials needed for advanced applications in fields like energy and telecommunications.

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.

Here is presented an overview on the usage and application of rare-earths, and also of the rare-earth market. This overview will focus on recent trends.
The low price of rare-earths have discouraged some mining projects, such as that of Brazilian company CBMM which decided to keep focusing on niobium production. Serra Verde, a Brazilian mining company, however, promised to start production in the next decade of heavy rare-earths as dysprosium.
The Mountain Pass Californian mine returned to produce rare-earths, and now has an annual production of similar size as the Australian mine Lynas. Both Lynas and Mountain Pass focus on light rare-earths. Mountain Pass sends the rare-earth concentrate for further processing in China. Myanmar also had significant production of rare-earths last year, with an amount near that of Lynas and Mountain Pass. The Neodymium oxide prices have decreased 10% since the beginning of 2019.

Both Neodymium and Praseodymium are seen as essential for electric cars. Each electric car uses ~1 -1.5 kg of NdPr-Fe-B type magnets [1]. Giant wind turbines, constructed without gearbox, which avoids maintenance problems, need tons of NdPr-Fe-B magnets.
The Europium price is low at the present time, and has been below the Holmium price. Both Gadolinium and Holmium have been used as alloying elements in rare-earth magnets.
Terbium is in high demand, which is attributed to the application of Tb in Terbium-diffused magnets. Dysprosium also is seen as necessary to increase the temperature of operation of the magnets.
Cerium and Lanthanum are in large oversupply. Application of Cerium as red pigment (Ce₂S₃) has been proposed. Use of cerium base red pigments would avoid use of cadmium or molybdenum-chromium.
Recycling of fluorescent lightbulbs for recovering Europium and Terbium is possible, but the low price of Europium is a problem for economic feasibility. Now, LED lightbulbs, which use much less are-earths than fluorescent lightbulbs, are dominating the market.
Recycling of Magnets is possible, since there is standardization of commercial magnets. An enormous amount of energy is spent in the magnet production. If only the rare-earth oxide, such as neodymium oxide, is recovered, the energy used in the process is lost. The re-use of magnets is the best option for rare-earth magnet recycling.

The structure of glasses is generally taken to be isoconfigurational, although it is well-known that the details of structure arrangement strongly depend on the temperature-time history experienced while establishing the glassy state.
Recent studies of glass-forming metallic systems have revealed intriguing complexity, e.g. unusual shifts in radial distribution functions with temperature change or upon mechanical loading in the elastic or plastic regime. Nearest neighbour distances and medium-range order structural arrangements appear to change, e.g. shorten upon heating or become larger with decreasing temperature. Concomitantly, temperature changes as well as static or dynamic mechanical loading within the nominally elastic regime can trigger significant changes in glass properties, which are directly correlated with local non-reversible configurational changes due to non-affine elastic or anelastic displacements. All these findings strongly suggest that the characteristics of the atomic structure decisively determine the properties of the glass and of nanostructured materials derived from glass-forming systems.
Recent findings and developments along this line will be summarized. Results from high-energy synchrotron x-ray radiation investigations at different temperatures and after mechanical loading will be related to the atomic structure of the material. It will also be related to its dependence on temperature, mechanical load as well as intrinsic heterogeneities and length-scale modulation to elucidate the correlation between atomic arrangement and mechanical or magnetic properties.

Several models for predicting the effect of grain size on the coercive field are presented and discussed.
For small grain size, near the mono domain grain size, a law Hc ~ 1 / D0.5 has been observed [1]. Here, Hc is the coercive field and D is the grain size. For sintered NdFeB and Strontium ferrites, the Hc ~ 1 / D0.5 law has been experimentally confirmed.
For very large grain size, however, a case of soft magnetic materials as electric steels, a Hc ~ 1 / D is observed [2].
The origin of these different behaviors is discussed [3].
We also discuss how to evaluate the effect of grain size on the coercive field by means of a nucleation model.

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.

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.

The majority of the iron oxide-based clinically approved contrast agents for magnetic resonance imaging (MRI) have been withdrawn from the market either due to safety concerns or lack of profits.[1] Therefore, there is a need for novel imaging agents with high safety margins and superior MRI properties. Several factors influence the relaxation of water molecules in the vicinity of the magnetic centres, such as NP's magnetization and surface coatings.[2], [3] The latter can affect the relaxation of water molecules in various forms, such as diffusion, retention, hydration, and hydrogen bonding.[3], [4] In the first part, it will be demonstrated how size and clustering influence nanoparticles’ magnetic properties and consequently relaxivity r2 values. In the second part, the focus will be on coating optimization with a description of all the parameters that influence r2 values and thus the performance of NPs as T2 MRI contrast agents. [2], [3] Proper surface coating endows NPs with good colloidal stability and protects them from undesired degradation or aggregation. The effect of different coating material and thickness on the r2 values will be discussed. Moreover, a surface that favors diffusion and retention of water molecules within the second sphere is preferred. Taking all these parameters into account, the case study made on different phospholipids as optimal coating material will be presented. In conclusion, the in vitro MRI measurements revealed that use of magneto liposomes as contrast agents leads to an improvement in the contrast and an easier distinction between the healthy and the cancerous tissues. This proves that the developed liposomes have a high potential to be used as MRI contrast agents, even at very low concentration.

Ever-growing population and consumption has put continuously increasing pressure on our planet's health including humans, ecosystems, and natural resources [1]. At the same time, efficiency in production and techno-economic performance are the drivers of today's economy. These unsustainable global trends push our industrial civilization toward crossing our planet's boundaries for a resilient climate, functional geochemical cycles, and healthy environments [2]. To ensure that future technologies move away from contributing to an unsustainable future, we need a radical paradigm shift. New designs and developments need to be fundamentally aligned with sustainability constraints. Considering such constraints comes with several key requirements. We need to determine the physical limits of ecosystems, human health, and environmental assets for resources extraction, environmental pollution and global exposure. We also need to understand the complexity of environmental pressure of the thousands of new chemicals, materials and products entering the global market every year along their entire life cycle. Finally, we need to benchmark all new designs against the physical limits of our planet. Physics, material science, and sustainability assessment are all crucial elements to meet these requirements. This will ultimately lead to sustainability-driven innovation in technology design and development of absolutely sustainable products and supply chains [3].

The magnetic properties of soft magnetic materials such as Fe-3wt%Si and Fe-6.5wt%Si studied here can be strongly improved by nanocrystallization if the grain size is smaller than the magnetic moment exchange length [1]. Recent top-down techniques like those of Severe Plastic Deformation (SPD), in particular of High Pressure Torsion (HPT), allow for the production of bulk nanocrystalline soft magnetic materials, as they are capable to reach grain and/or subgrain sizes well below 100-10 nm [2], thus underrunning the exchange length of magnetic moments. This fact should lead to a significant decrease of coercive force (Hc) and finally of the hysteresis losses (P/f with f as the frequency), being an inherent goal of soft magnetic materials research. HPT-induced changes of Hc and P/f were found to be in parallel; they could be related to the changes of two most important parameters such as the subgrain size (D), and the dislocation density (N). In both cases, only decreases of D or N led to decreases of Hc. At least the first result confirms that Hc is indeed dominated by exchange coupling within the magnetic domains, their size exceeding that of the subgrains. Since HPT can only achieve decreases of D and concomitant increases of N, thermal treatments were applied after HPT-processing, in order to decrease N while keeping D unchanged. A maximum decrease of Hc could only be reached when a strong increase of D or N during HPT-processing or during thermal treatment could be avoided. Other conditions are that neither the HPT-induced strain is too large nor the processing temperature applied is too low; otherwise nanostructures become resistant to the thermal treatment. Theories from literature [3] which predict a change of the Hc ~ D6law for large-angle misoriented grains, to a law with distinctly lower exponent Hc ~ D3 or D2 in the case of small-angle misoriented subgrains, were confirmed by the experiments [4].
Another example of successful application of SPD to functional nanomaterials is the improvement in functional properties of biodegradable binary and ternary Mg-Zn-Ca alloys achieved by High-Pressure Torsion (HPT)-processing and subsequent heat treatment. These procedures have been applied in order to strengthen the alloy and to limit the corrosion rate [5]. Two paths of HPT-processing fulfilled these conditions; these were (i) low temperature-low strain HPT, or (ii) high temperature-high strain HPT of the solid solution state, both followed by subsequent thermal treatment at 373 K [6]. While treatment (i) yielded strength increases till 250% mainly due to generation of HPT-induced defects including those of vacancies, treatment (ii) produced precipitates with strength increases of only 60% but much higher ductility [6]. In conclusion, SPD-processing achieved different nanostructures with individual extents of strength, ductility and corrosion resistance, thus meeting the specific requirements of different biodegradable implants and prostheses.

Superconducting magnetic levitation is passively stable without any electronic control except with attracting and repelling forces to suspend a vehicle pendant or standing upright. Due to this intrinsic stability, the levitation itself does not consume any energy. These are perfect conditions for a rail-bound system like Hyperloop. Individual transport with cabins for 4 to 5 passengers is requested call by call. They will levitate without noise over a track made of rare-earth permanent magnets, saving energy and travel time. A big step forward in this vision has been made in Dresden. The world’s largest research and test facility for transport systems using bulk high-temperature superconducting material in the levitation and guidance system, in combination with a permanent magnet track, was put into operation. A vehicle for 2 passengers, equipped with linear drive propulsion, noncontact energy supply, second braking system, and various test and measurement systems runs on an 80 m long oval driveway. In the presentation, the principle of superconducting levitation by flux pinning in bulk high-temperature superconductors will be described. Based on this, an overview of the SupraTrans II research facility and future directions of superconductivity-based magnetic levitation and bearing for automation technology, transportation, and medical treatment under enhanced gravity will be given. Also, the physics behind the "Back to the Future II " superconducting hoverboard, recently presented by Lexus, will be described.

Progress of microprocessors or logic integrated circuits has been conducted by the continuous miniaturization of Si MOSFETs. In the course of the miniaturization, the gate length and the gate oxide thickness have been reduced with the same ratio. Silicon dioxide (SiO₂) has been used as the gate insulator for many years. In order to decrease the equivalent gate oxide thickness (EOT) to less than 1 nm, high-dielectric material is necessary [1] and hafnium dioxide (HfO₂) [2] was chosen to replace SiO₂. For further decreasing of the EOT to sub-0.5 nm, lanthanum oxide (La₂O₃) is supposed to be one of the best candidates among many materials when considering the band-offset and dielectric constant values [3]. Then, La silicate is expected to be even better because La silicate has some good properties similar to SiO₂. In this paper, excellent MOSFET characteristics with 0.4 nm EOT gate oxide are demonstrated by introducing La silicate as the gate dielectrics.
After the n⁺ source and drain formation on the p-Si substrate, the La₂O₃ gate oxide film was deposited by an ultra-high vacuum evaporation method, followed by tungsten (W) and tantalum nitride (TaN) gate electrode film deposition by in situ RF sputtering under ultra-high vacuum conditions. After the gate electrode patterning, 3% forming gas annealing was performed for 30 minutes. After the annealing, a thin La silicate gate insulator was created with a smooth interface. The diffusion of oxygen into the gate oxide and the resulting increase of the EOT were almost completely suppressed by the combination of the stacked TaN and W gate electrode and the ambient forming gas during the annealing.
The minimum EOT value obtained by C-V measurement was 0.4 nm. Very low values for the interface state density for the La silicate MOS capacitor of less than 10¹¹cm^-2eV^-1 were observed during the forming gas annealing performed above 850^oC. The fixed charge density evaluated by the flat-band voltage was 1.0 X 10¹¹cm^-2. La silicate films are composed of good glass network structures as those of SiO₂ and have high viscosity at high temperatures. The movement of the atoms at a high temperature recovers the defects at the interfaces and in the films. This is the reason for the low interface state and fixed charge densities. Good I_d - V_d characteristics of a 0.4 nm EOT MOSFET were confirmed because of the excellent interfacial property. Due to the high band offset value between the conduction-bands of the Si channel and the La silicate gate insulator, the tunneling leakage current was almost completely suppressed down to EOT = 0.4 nm.

In addition to the intrinsic magnetic properties, the microstructure is of utmost importance for the performance of a permanent magnet. We show how to use machine learning methods in order obtain a deeper understanding of the influence of the granular structure on the coercive field of permanent magnets. Using machine learning, we can identify the weak spots in a magnet where magnetization reversal is initiated. Tailored improvement of the magnet's structure or the intrinsic magnetic properties at regions where the switching field was identified to be low can sufficiently improve the magnet.
Work supported by the European Union's Horizon 2020 NMBP23-2015 research No 686056.

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.

Magnetic shape memory Heuslers are an important class of ferroic materials for next-generation remote actuation and energy conversion (i.e. solid-state cooling and energy harvesting), arising from giant multifunctional effects (e.g. thermo/magneto-mechanical, magneto/elasto-caloric) that can be driven by external stimuli (i.e magnetic field, temperature, pressure and stress) [1]. Low-dimensional materials, mainly thin films, have recently attracted much interest for their great potential in applications (e.g. microactuators, solid-state microrefrigerators, microvalves) [2]. With respect to the bulk, they offer the further possibility of tuning properties by exploiting the epitaxial growth on suitable substrates and underlayers. Patterned films and 2D nanostructures are nowadays a vast and almost unexplored field.
This talk is focused on microstructure engineering of continuous and patterned NiMnGa thin films, and free standing nanodisks. By a thorough multiscale magnetic and structural study ,we will show that martensitic microstructure is sensitive to size confinement and can also be easily tuned by tuning growth parameters and performing suitable post-growth treatments (magnetic field, T, stress) [3, 4]. Microstructure engineering can be exploited for the optimization of the multifunctional properties. As an example, we demonstrate the possible actuation of free standing nanodisks by the combined application of temperature and magnetic fields, giving rise to areal strain (up to 5.5%) whose intensity and sign is ruled by a martensitic microstructure [5]. On the other hand, such "microstructure flexibility" makes magnetic shape memory materials a unique system, among magnetic materials, for the "magnetic flexibility"; magnetism can be easily manipulated at the different length-scales by taking advantage of martensitic microstructure and strong spin-lattice coupling.

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 µ₀H_ci, remanent magnetization σ and energy product (BH)_max were 0.87 T, 39.3 Am²/kg and 23.4 kJ/m³, respectively.[ii]

We review recent advances in the development of two types of rapidly quenched alloys that show promise as structural materials. In each case, the focus of interest is the dispersions of nanocrystals in the residual amorphous matrix that can be achieved by treating initially fully amorphous melt-spun ribbons.
The first alloy type is Al-based with compositions such as Al₉₀Y₁₀ (at.%) and Al₈₄Y_8.5Ni₄Co₂Pd₁Fe_0.5 [1,2]. Remarkably, when amorphous ribbons are cold-rolled, this induces partial crystallization to nanoscale fcc-Al (alpha-Al). By contrasting this crystallization with the apparently similar crystallization induced by annealing, progress has been made in understanding the mechanisms of hardening and softening. Polymorphic crystallization induced by cold-rolling avoids the formation of compound phases associated with brittleness, and is therefore promising for the development of high-solute Al-based alloys as structural materials.
The second alloy type is metal-metalloid, with a complex (high-entropy) mixture of metals and relatively low metalloid content. An example is the alloy series (Fe_0.25Co_0.25Ni_0.25Cr_0.125Mo_0.125)_86-89B_11-14 [3]. Initially amorphous alloys when annealed show complex crystallization sequences. Nanoscale (5-15 nm) particles of fcc and bcc phases are formed and show very high thermal stability (resistance to coarsening). It is of particular interest that ultrahigh hardness of 1500-1550 Hv can be achieved without the formation of any boride phases. The hardening and thermal stability are unusually high for such low boron content and encouraging for the development of ultrahard coatings.
Prospects for further alloy development are considered.

Nd₂Fe₁₄B hard magnets are a strategic material in determining the efficiency and size of both existing and future electrical and electronics devices. To meet the strict device requirements, these magnets are often doped with expensive heavy rare-earth elements like Dy, and Tb. In our research, we combined machine design and material development to produce the permanent magnets in the shape required to eliminate the dependency of those two chemical elements. At this conference we will present firstly that expensive Dy-rich, high coercivity magnet compositions may not be required throughout the full magnets within electrical machines, and the steps in experimental realization of such magnet geometry will be discussed. Second, we will show that the emerging technology named 3D metal printing by selective laser melting can be used produce hard magnets in various shapes. The magnetic properties of 3D printed magnet are superior to those prepared by other means, like injection molding and spark plasma sintering. It is demonstrated that the fast melting and solidification process provided by this fabrication method enables an internal microstructure not achievable by any other production means, resulting in an increase of magnetic performance. Finally, 3D printing brings to the magnet novel functionality. For example, a cooling channel extends its application range and, very importantly, reduces the magnetic dependence on Dy and Tb.

Powder metallurgy has been established in the past sixty years as an old technique, deriving its roots from ancient civilizations, to produce ferrous, copper and zinc products. It was only twenty years ago that it was demonstrated in our laboratory for the first time that it is possible to produce aluminum powder metallurgy parts by using a small addition of magnesium in pure aluminum. It has now become an industry of its own, producing millions of parts used in automotive applications. In this presentation, attempts to extend the powder metallurgy to magnesium metal and its alloys will be discussed. In the last decade, the machine design and its artificial intelligence led to the utilization of 3D metal printing or additive manufacturing. The emphasis has been shifted to the computer aspects of the process although there are still fundamental difficulties on sintering metals.

The demand for high-performance rare-earth-iron permanent magnets in various applications such as motors/sensors for automotive, electronic devices, or home appliances has increased in recent years. Sintered or hot-deformed Nd-Fe-B magnets [1, 2] are the most attractive choice because they have the highest (BH)max value among all the commercial magnetic materials. The addition of heavy rare earth elements (HREEs), such as Dy or Tb, is a common way to increase the coercivity of Nd-Fe-B magnets thus allowing the use of such magnets at high temperatures. The problem with the HREE addition, however, is the reduction of (BH)max. Another problem, which is even more serious, is the supply risk of HREEs due to geo-political and environmental issues. Accordingly, efforts to reduce HREE use have been undertaken all over the world. Fabrication processes utilizing grain boundary diffusion (GBD) have recently been developed to effectively reduce HREE usage by more than 50%. The ultimate goal, however, is the creation of HREE-free Nd-Fe-B magnets with high coercivities.
It is well known that decreasing the grain size increases coercivity. The hot-deformed magnet has a fine microstructure that is one order of magnitude finer than that of the conventional sintered magnet. Thus, hot-deformed Nd-Fe-B is a promising material to create high performance HREE-free magnets. The PLP (Press-less Process) proposed by one of the authors also realized a fine-grained sintered Nd-Fe-B magnet. This is because the atmosphere in the PLP process is inert throughout the processes and the resulting magnets contain a low level of oxygen inclusions [3]. By optimizing the fabrication processes and microstructures, high coercivities of about 1600 kA/m (20 kOe) have been obtained for HREE-free magnets made with the above two types of fine-grained magnets [3, 4].
Sm-Fe-N materials also have demonstrated excellent magnetic properties and corrosion resistance when used as bonded magnets [5]. It is important to expand the market for the Sm-Fe-N from the resource management point of view because Sm is one of the surplus rare-earth elements. Various studies to improve the magnetic properties are now being conducted by many research groups.
In this symposium, recent developments for the above R-Fe-X permanent magnets will be presented.

Ferroelectrics are materials with a wide range of applications, an important one being non-volatile memories [1]. Efforts were made to obtain epitaxial films by pulsed laser deposition (PLD). There are still debates, however, regarding the intrinsic properties of ferroelectrics. Here we report new results regarding intrinsic properties of single crystal PbZr_0.2Ti_0.8O ₃ (PZT) layers manufactured on single crystal SrTiO₃ substrates with bottom and top SrRuO₃ electrodes, as well new functionalities in PZT-based multi-layers of the PZT-interlayer-PZT type. The main findings are:
- The dielectric constant in ultra-thin epitaxial PZT layers, of 20-25, is very low. This was evidenced by a new method of recording the voltage dependence of capacitance named "static" C-V characteristics and was explained in relation with the structural quality of the epitaxial films, showing that films with structural defects have a larger dielectric constant.
- The relation between hysteresis loops and the C-V characteristic is discussed. It is shown that a negative capacitance effect can be obtained during polarization switching at around P=0. This is a transitory effect and is explained by a sudden increase of the electrical conductivity when the charges involved in the compensation of the depolarization field change places from one electrode interface to the other.
- New functionalities were found in tri-layer structures such as the PZT-interlayer-PZT, with a semiconducting or insulating interlayer. These layers can consist of multiple polarization states that can be used in memory cells with multiple states or of multiple capacitance states that can be used as non-destructive readout methods for FeRAMs. It was also found that tri-layer structures can be used for logic operations but can also function as memcapacitors.

RE-Fe-B permanent magnets have been increasingly used for motor applications in automotive industry. Higher performance magnets are always in demand as they enable the motor to achieve high efficiency, high power density and smaller size. It is well known that rapid solidification technology has the advantage of producing nanoscale fine-grained RE-Fe-B material and therefore enabling higher magnetic performance. For past several years, melt-spun RE-Fe-B powders and their bonded magnets and fully-dense magnets have found more and more applications in the automotive industry.
In this presentation, we will review Magnequench’s latest R&D efforts in RE-Fe-B product development for automotive applications. These include isotropic melt-spun MQP and MQU powders, and anisotropic MQA powders. MQ1 bonded magnets made from MQP or MQA powders, and fully-dense MQ2 and MQ3 magnets made from MQU powders will also be discussed. An emphasis will be put on their processing-microstructure-performance relationships, especially microstructure uniformity and its importance on magnetic performance.

Bulk metallic glasses (BMGs) exhibit a unique temperature-dependent mechanical behavior, which enables the processing of polymers at temperatures higher than the critical BMG-specific glass transition temperature [1]. In this work, we report on the thermoplastic behavior of two Ni-free Ti-based bulk metallic glasses by utilizing the dramatic softening of the amorphous structure in the supercooled liquid region. Ti₄₀Zr₁₀Cu₃₄Pd₁₄M₂ (M = Ga, Sn) bulk glassy alloys were produced by copper mold casting. Ga and Sn micro-alloying (2 at.%) improve the glass-forming ability and mechanical properties of Ti₄₀Zr₁₀Cu₃₆Pd₁₄ alloy effectively [2, 3]. The cast rods were thermo-mechanically characterized to determine the most suitable processing temperature, time, and the load that has to be applied for thermoplastic net-shaping of the BMGs into anisotropically etched cavities of silicon chips. Periodic features with high surface smoothness and uniform height were created on the surface of the BMGs. The surface patterning with controllable roughness of Ti-based BMGs can be useful in biomedical studies by mediating material - cell interactions. Financial support through the EC (FP7 VitriMetTech-ITN) and ERC-Advanced Grant "INTELHIB" is gratefully acknowledged.

Quasiperiodic structures exhibit long-range order like normal crystals, but lack translational symmetry. Quasicrystals were first discovered as a new class of intermetallic compounds, now comprising hundreds of members in binary and ternary systems. They usually adopt either the icosahedral or the decagonal point group symmetry. Later, quasicrystals were also found in soft matter systems and more recently, in a two-dimensional perovskite oxide thin film grown on a periodic substrate. The discovery of quasicrystals has led to a paradigm shift in crystallography and has attracted a large interest in the material science community, motivated by unexpected physical properties that could be linked to quasiperiodicity. This remarkable class of materials has also challenged our understanding of metal surfaces. An atomic scale description of their surfaces is especially important, as it forms the basis for understanding and predicting phenomena such as gas adsorption, metal epitaxy, and friction. Here we will review some key results on the characteristics of their surface structure and their physo-chemical properties [1-4].

References:
[1] J. Ledieu, V. Fournée, Comptes Rendus de l’Académie des Sciences, Physique, 15 (2014) 48-57.
[2] J. Ledieu, É. Gaudry, V. Fournée. Sci. Technol. Adv. Mater. 15 (2014) 034802.
[3] V. Fournée. “Surface properties and engineering of complex intermetallics”. Book series on Complex Metallic Alloys – Vol. III., E. Belin-Ferré Eds., World Scientific, Singapore, 2010, ISBN: 13-978-981-4304-76-4. pp. 183-229.
[4] V. Fournée, J. Ledieu, J.Y. Park. “Surface Science of Complex Metallic Alloys”. in “Complex Metallic Alloys: Fundamentals and Applications”, J.M. Dubois, E. Belin-Ferré Eds., Wiley, Berlin, 2011, ISBN: 978-3-527-32523-8. pp 155-207.

In recent years there has been significant price volatility for rare earth magnets based upon neodymium iron boron (NdFeB), which has stemmed from possible supply constraints from the main supplier (China). The Magnetic Materials Group (MMG) has been developing recycling strategies for these materials to mitigate at least some of the supply risk as well as investigating efficient methods of manufacture for fully dense NdFeB magnets. In this presentation Prof Walton will outline the problems encountered when recycling rare earth magnets from end of life products, including identification of magnet type, ease of extraction, problems for purification and complications for re-processing into new materials. He will then propose solutions to these problems including new sensor technologies for identifying magnets in waste, robotic disassembly of magnet containing products and hydrogen based technologies for extraction and reprocessing of sintered magnets.
In the second part of the presentation Prof Walton will outline a new method for producing fully dense NdFeB magnets called the Hydrogen Ductilisation Process (HyDP ref- 1,2,3). During HyDP solid cast NdFeB alloys can be converted into a ductile material at room temperature. This is achieved by converting the cast alloy into a disproportionated structure containing -Fe, NdH2 and Fe2B by processing in hydrogen at between 1-2 bar pressure and > 600^oC. The disproportionated material can be pressed at room temperature and on recombination this produces a small grained anisotropic NdFeB magnetic material. The HyDP process could be used to reduce the yield loss for producing thin magnets compared to conventional sintering processes, it may be possible to process in air which would reduce cost and it could be used to make complex geometries.

We live in a time of unprecedented global change, and face a very near future of climate chaos, mass migration, and sociopolitical upheaval. We now have only about eight years to radically improve the ecological conditions on the planet to avoid mass extinctions, and at most twenty years to master the emerging field of geotechnical or planetary, engineering. If civilization is going to exist for our grandchildren, we must become very good at planetary-scale engineering, and quickly. How do we move whole cities? How do we radically regenerate ocean and atmospheric health? What should future civilizations look like, and does humanity have the strength, courage, and ingenuity to rise to these challenges, or have we doomed life on the planet to extinction? What role might physics and the material sciences play, and what special responsibilities does the research community have? What decisions should the EU and its nations make now to ensure their future survival? Are we as scientists acting rationally, and what should we do next?

We live in a time of unprecedented global change, and face a very near future of climate chaos, mass migration, and sociopolitical upheaval. We now have only about eight years to radically improve the ecological conditions on the planet to avoid mass extinctions, and at most twenty years to master the emerging field of geotechnical or planetary, engineering. If civilization is going to exist for our grandchildren, we must become very good at planetary-scale engineering, and quickly. How do we move whole cities? How do we radically regenerate ocean and atmospheric health? What should future civilizations look like, and does humanity have the strength, courage, and ingenuity to rise to these challenges, or have we doomed life on the planet to extinction? What role might physics and the material sciences play, and what special responsibilities does the research community have? What decisions should the EU and its nations make now to ensure their future survival? Are we as scientists acting rationally, and what should we do next?

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.

Whether for therapeutic or aesthetic purposes, implantable medical devices have to be biocompatible and functional. Their implementation requires surgery that can be considered as a cumbersome procedure as it depends on the patient. Additionally, the osseointegration of these implantable devices has to be sustinable. Considering the example of dental implants, there are two types of implants: endosseous axial implants and supraosseous basal with lateral fixation implants on maxillofacial skeleton girders. These axial implants are manufactured by machines with standard diameters and lengths defined for all implant brands. It is the same for basal plate implants. The sustainability of these devices, in contact with living media, seems to be related to the mechanical and surface characteristics of implanted parts. The development of periodontal diseases like peri-implantites, caused by a bacterial grip, leads to the removal of the implant due to the long term destruction of the oxide layer and the bacterial corrosion of titanium. In order to understand the sustainability of dental implants, an experimental study was conducted on the determination of elastic and surface properties (roughness parameters) of various materials and for different surface conditions. The results show that the knowledge of these characteristics alone is insufficient to understand the sustainability of implanted devices. A biological improvement of the surface condition is necessary to avoid the loss of osseointegration by bacterial attack.

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.