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We have determined the crystal structure and the magnetic state of the CeFe$_9$Si$_4$ intermetallic compound. Our revised structural model (fully ordered tetragonal unit cell, I4/mcm) agrees with the previous literature report, except for some minor quantitative differences. Magnetically, the CeFe$_9$Si$_4$ undergoes a ferromagnetic transition at the temperature TC ≈ 94 K. Ferromagnetism in the combined Ce−Fe spin system is a result of interplay between the localized magnetism of the Ce sublattice and the Fe band (itinerant) magnetism. Ferromagnetic ordering obeys the rather general rule that the exchange spin coupling between atoms possessing more than half-full d shells with atoms possessing less than half-full d shells is antiferromagnetic (where the Ce atoms are considered as light d elements). Since in rare-earth metals from the light half of the lanthanide series, the magnetic moment is directed opposite to the spin, this results in ferromagnetism. The magnetoresistance and the magnetic specific heat show an additional temperature-dependent feature (a shoulder) deep inside the ferromagnetic phase that is considered to originate from the influence of the magnetization on the electronic band structure via the magnetoelastic coupling, which alters the Fe band magnetism below T$_C$. The ferromagnetic phase of CeFe$_9$Si$_4$ is magnetically soft.

The effect of Ni/Cu-coating residuals on the magnetic properties and microstructures of samarium–cobalt (SmCo5) magnets was studied. SmCo5 magnets with 0.0, 0.5, 1.0, 2.0, 3.0 and 4.0 wt.% of added Ni/Cu (85 wt.% Ni/15 wt.% Cu) were prepared using a conventional sintering route. The magnetic properties of the magnets were found to be consistent up to 2 wt.% Ni/Cu. Any further increase in the Ni/Cu content resulted in a significant reduction in the magnetic properties, to lower than values that would be commercially acceptable. SEM/EDS studies showed that two major phases, i.e., the SmCo5 matrix phase and Sm2O3 were present in all the sintered SmCo5 magnets. The presence of Sm2Co7 as a minor phase fraction was detected in the sintered SmCo5 magnets containing up to 2 wt.% Ni/Cu. A 2 wt.% Ni/Cu addition to magnets resulted in the presence of two new phases with compositions close to SmCo and Sm2Co17 in addition to SmCo5 and Sm2O3 as major phases in the SEM-observed microstructure. These newly formed phases are present in small fractions and are presumably homogenously distributed at the grain boundaries of the magnets. As they are known to act as nucleation sites for reverse magnetic domains, they effectively reduce the intrinsic grain boundary magnetic strength, leading to a drop in the coercivity. We concluded that the sintered SmCo5 magnets could be recycled with up to 2 wt.% Ni/Cu as a residual from the coating under our sintering and heat treatment conditions.

B has been proposed to extend persistent luminescence from minutes to > 10 h in Eu, Dy, and B co-doped Sr4Al14O25 (S4A7EDB) by facilitating the incorporation of Eu2+ and Dy3+ into adjacent Sr sub-lattice sites and enabling energy transfer between them. To evaluate additional influences of B on the kinetics of microstructural evolution and dopant distribution that support afterglow in S4A7EDB, the effect of heating rates to 1300 °C is compared for spark-plasma sintering and conventional sintering, with and without the addition of B2O3. Analysis of the microstructure and elemental distribution, by a combination of imaging, WDS, and CL in the SEM, XRD, dilatometry, and STEM-EELS, reveals that when the diffusivity of Eu and Dy is increased, Eu and Dy segregate to the intergranular phase. The partitioning of Eu and Dy concentrations to below their solubility limit in the grains appears to be essential to material structure enabling longer afterglow.

A green and facile electrochemical method for Nd–Fe–B PM recycling was developed. The proposed procedure enables a selective REE recovery and a simultaneous Fe metal deposition in only two processing steps, with the total re-use of the electrolyte. The proposed procedure thus avoids the formation of solid Fe-based waste and wastewater discharge.

A sustainable solution for the global construction industry can be partial substitution of Ordinary Portland Cement (OPC) by use of supplementary cementitious materials (SCMs) sourced from industrial end-of-life (EOL) products that contain calcareous, siliceous and aluminous materials. Candidate EOL materials include fly ash (FA), silica fume (SF), natural pozzolanic materials like sugarcane bagasse ash (SBA), palm oil fuel ash (POFA), rice husk ash (RHA), mine tailings, marble dust, construction and demolition debris (CDD). Studies have revealed these materials to be cementitious and/or pozzolanic in nature. Their use as SCMs would decrease the amount of cement used in the production of concrete, decreasing carbon emissions associated with cement production. In addition to cement substitution, EOL products as SCMs have also served as coarse and also fine aggregates in the production of eco-friendly concretes.

In this work, we present a newly developed, economically efficient method for processing rare-earth Nd-Fe-B magnets based on spark plasma sintering. It makes us possible to retain the technologically essential properties of the produced magnet by consuming about 30% of the energy as compared to the conventional SPS process. A magnet with anisotropic microstructure was fabricated from MQU F commercial ribbons by low energy consumption (0.37 MJ) during the deformation process and compared to the conventionally prepared hot-deformed magnet, which consumed 3-times more energy (1.2 MJ). Both magnets were post-annealed at 650 °C for 120 min in a vacuum. After the postannealing process, the low-energy processing (LEP) hot-deformed magnet showed a coercivity of 1327 kAm-1, and remanent magnetization of 1.27 T. In comparison, the highenergy processing (HEP) hot-deformed magnet had a coercivity of 1337 kAm-1 and a remanent magnetization of 1.31 T. Complete microstructural characterization and detailed statistical analyses revealed a better texture orientation for the HEP hot-deformed magnet processed by high energy consumption, which is the main reason for the difference in remanent magnetization between the two hot-deformed magnets. The results show that, although the LEP hot-deformed magnet was processed by three times lower energy consumption than in a typical hot-deformation process, the maximum energy product is only 8 % lower than the maximum energy product of a HEP hot-deformed magnet.

A new ternary phase with a composition Al1+xV2Sn2–x (x = 0.19) has been found during investigation of the Al–V–Sn ternary system. Single-crystal X-ray diffraction measurements reveal that this ternary phase crystallizes with an orthorhombic structure with a = 5.5931(1) A, b = 18.8017(5) A, and c = 6.7005(2) A (space group Cmce). This compound is thus isostructural to the GaV2Sn2 structure type, showing a layered structure composed of vanadium cluster bands formed with pentagonal faces intercalated by Sn atom layers. High-resolution transmission electron microscopy measurements confirm the orthorhombic structure. Regarding lattice perfection, no dislocation could be identified within the probed Al1.19V2Sn1.81 single-crystal lamella. Ab initio calculations reveal a reduction of the density of states at the Fermi level, which could be attributed to both a Hume–Rothery effect combined with strong spd hybridization.

Ceramic pigments emitting long afterglow have enormous potential for emerging lighting applications that consume zero energy from the power grid. One of the most efficient compounds is strontium aluminate, when co-doped with 2 rare-earth elements — an optically active emitter, such as Eu2+, and an auxiliary ion, such as Dy3+— and B. To date, spectrophotometric methods are commonly used to determine the material structure supporting long afterglow, yielding indirect evidence of energy transfer between the rare-earth co-dopants. Here, atomic resolution HAADF-STEM imaging is used to resolve columns of Sr sub-lattice sites in the (012)-projection of a Sr4Al14O25:Eu,Dy single crystal. Through quantitative STEM image simulations, heavy rare earth dopants are shown to incorporate substitutionally into Sr sites, causing an enhancement in image contrast over that of neighboring atomic columns by 125%. DFT structural simulations demonstrate that Eu2+ and Dy3+ would incorporate into adjacent Sr lattice sites along the [012], enabling energy transfer between them that we see as afterglow. With the help of atomic resolution HAADF-STEM imaging, we also provide direct experimental evidence of clustering of ionic point defects induced by B doping, leading to extremely long (>14 h) afterglow in strontium aluminate phosphors.

Highly ordered, Ni(OH)2 Ni-nanowire-based receptor elements were electrochemically fabricated and tested for formaldehyde (HCHO) detection by monitoring their oxidation ability in alkaline media. In order to normalize the electrochemical output currents, the Ni nanowires' electrochemically active surface area was assessed using an oxalate-based method after the template was released. The electrochemical transformation of the Ni-nanowire surfaces to a Ni(OH)2/NiOOH redox couple was performed in 0.5-mol L−1 KOH using cyclic voltammetry at 200 mV s−1. The transformation was monitored for two cases: without KOH modification and with KOH-modified Ni nanowires. It was shown that the non-modified Ni nanowires possess a poor electrochemical response to HCHO oxidation, mainly due to the formation of a NiO surface layer. On the other hand, the modified Ni nanowires donated an electron to the HCHO oxidation reaction, resulting in high output-current densities, attributed to the thin Ni(OH)2/NiOOH layer, its amorphous state (TEM/SAED) and its small work function, due to electron doping from under the layered Ni. The modified Ni-nanowire-based electrodes had high sensitivity, reproducibility, selectivity and a low detection limit (0.8 μmol L−1). The developed HCHO Ni-nanowire-based electrodes’ characteristics surpass other Ni-based nanostructured electrodes and have limits of detection comparable to those achieved with noble metals.

The investigation of the nucleation and dissolution of gold nanoparticles on a glassy carbon substrate with Scanning Electrochemical Cell Microscopy (SECCM) combined with in-situ electrochemical TEM (EC-TEM) revealed the subtle influence of the local properties of the substrate on the electrochemical processes. Conducting hundreds of locally-resolved voltammograms at the micro-scale resulted in the observation of a diversity of responses for nucleation, allowing to address experimentally the statistical nature of the nucleation and growth process. Moreover, during the electrochemical dissolution of previously electrodeposited nanoparticles (NPs), the confinement conditions of the SECCM-cell allowed the resolution of a multitude of events characterized as current spikes. Such current events are not observable in the macro-scale since the electrochemical response over the large electrode area is the convolution of the activity all over the electrode surface. The EC-TEM experiments demonstrated that such current spikes were generated by the dissolution of individual NPs distributed over a time range. Combining SECCM and EC-TEM unmasked information previously not seen from the electrochemical nucleation, growth, and dissolution of supported metal nanoparticles [1]. This approach could accelerate the discovery of novel functional electrode materials by facilitating the rational design of protocols for electrodeposition of nanostructured materials and the evaluation of their stability under electrochemical conditions. The possibility to consider the heterogeneous nature of the supports and the differences within nanomaterial ensembles opens the opportunity to consider the diversity of electrochemical parameters as descriptors to understand and describe the relationships between activity, stability, and structure. [1] M. Bernal, D. Torres, S. Semsari, M. Čeh, K. Žužek Rožman, S. Šturm, J. Ustarroz, Diversity matters: Influence of surface heterogeneities in the electrochemical nucleation and dissolution of Au nanoparticles, under revision

The (110) and (320) surfaces of the single-phase FeCrMnNiCo solid solution have been studied on two adjacent millimeter size grains using surface science and transmission electron microscopy (TEM) techniques. The structural and chemical evolutions of the high entropy alloy (HEA) surfaces have been determined for various sputtering conditions, annealing temperatures and durations. Up to 873 K, angle-resolved X-ray photoelectron spectroscopy measurements indicate a clear Mn and Ni surface co-segregation. We propose that the surface segregation of Mn is driven by its low surface energy. The attractive interaction between Mn and Ni promotes Ni segregation which accompanied the Mn diffusion to the surface. Regarding the structures investigated by low energy electron diffraction and scanning tunneling microscopy, the (320) surface presents a terraced morphology with an ordered structure consistent with a ( 1 × 1 ) termination. On the contrary, the (110) surface reveals an important degree of structural disorder and local reconstructions. Its highly anisotropic morphology resembles rows propagating along the [001] direction. Above 873 K, Mn desorption occurs while the Ni content keeps increasing linearly with the temperature. TEM analysis show no evidence for HEA decomposition into metallic or intermetallic phases even after repeated annealing and sputtering cycles. The above results set the upper temperature limit above which the surface stoichiometry departs from the quinary HEA concept. It also defines the temperature range for the use of FeCrMnNiCo based coating under high vacuum conditions and for aerospace applications.

We report the adsorption of Fe for several dosing conditions on Al(1 0 0) surface held at different temperatures. For 2 monolayer equivalent of Fe deposited on the substrate held at 593 K, we observe two rotational domains of a ( 5 × 5 )R26.6° structure by low energy electron diffraction and scanning tunneling microscopy. We identify this structure as the formation of the metastable Al9Fe2 intermetallic phase. The segregation energy and the structural stability of this intermetallic has been analysed using density functional theory based calculations. We propose that the formation of the Al9Fe2(0 0 1) metastable phase at the expense of other thermodynamically stable Al-Fe compounds, relies on a specific structural similarity between pure Al (0 0 1) planes of the intermetallic and Al(1 0 0) layers. These ‘common’ planes lead to the epitaxial relationship (1 0 0)Al [0 0 1]Al ∥ ( 0 0 1 ) Al 9 Fe 2 [ 1 3 ¯ 0 ] Al 9 Fe 2 . The Al9Fe2-Al matrix interface is sharp as revealed by transmission electron microscopy measurements.

Polyaniline (PANI) is a conducting polymer, widely used in gas-sensing applications. Due to its classification as a semiconductor, PANI is also used to detect reducing ammonia gas (NH3), which is a well-known and studied topic. However, easier, cheaper and more straightforward procedures for sensor fabrication are still the subject of much research. In the presented work, we describe a novel, more controllable, synthesis approach to creating NH3 PANI-based receptor elements. The PANI was electrochemically deposited via cyclic voltammetry (CV) on screen-printed electrodes (SPEs). The morphology, composition and surface of the deposited PANI layer on the Au electrode were characterised with electron microscopy, Fourier-transform infrared spectroscopy and profilometry. Prior to the gas-chamber measurement, the SPE was suitably modified by Au sputtering the individual connections between the three-electrode system, thus showing a feasible way of converting a conventional three-electrode electrochemical SPE system into a two-electrode NH3-gas detecting system. The feasibility of the gas measurements&rsquo, characterisation was improved using the gas analyser. The gas-sensing ability of the PANI-Au-SPE was studied in the range 32&ndash, 1100 ppb of NH3, and the sensor performed well in terms of repeatability, reproducibility and sensitivity.

Photothermal therapy has always been a very attractive anti-cancer strategy, drawing a lot of attention thanks to its excellent performance as a non-invasive and pretty safe technique. Lately, nanostructures have become the main characters of the play of cancer therapy due to their ability to absorb near-infrared radiation and efficient light-to-heat conversion. Here we present the synthesis of polyethylene glycol (PEG)-stabilized hybrid ultrasmall (80% cell viability decrease already after 10 min laser irradiation with a laser power P = 3W/cm2 that was proved to be harmless to the control cells. Moreover, a previous cell viability test had shown that the nanoparticles themselves were reasonably biocompatible: without irradiation cell viability remained high. Herein, we show that our hybrid AuAgNTrs exhibit very exciting potential as nanostructures for hyperthermia cancer therapy, mostly due to their easy synthesis protocol, excellent cell compatibility and promising photothermal features.

This study confirms that the stable icosahedral quasicrystal (iQc) phase Al65Cu20Fe15 (iQc–AlCuFe) can serve as a substrate for the nucleation of the metastable iQc–AlMnSi phase formed in rapidly solidified Al–Mn–Si alloys. The results reveal that a continuous, thin layer of the metastable iQc–AlMnSi phase can be formed on a stable iQc–AlCuFe particle. Electron backscatter diffraction patterns and selected-area electron diffraction patterns confirmed that epitaxy exists between the stable and the metastable iQc phases.

Iron and copper are immiscible elements, but can be combined in the presence of a third element such as aluminium or cerium. We varied the additions of immiscible Fe and Cu (ratio y) in the stoichiometric Al20.5Ce41.5(FeyCu1 − y)38 alloys in order to trace their impact on the structure, microstructure, thermal properties and magnetism. By powder X-ray diffraction (PXRD), we found that Fe-rich alloys (0.87 ≤ y ≤ 1) do not completely hinder crystallisation and yield nanocrystalline precipitates. Cu-rich alloys completely vitrify for 0 ≤ y ≤ 0.74 and exhibit a characteristic broad hump in PXRD patterns. DSC shows that Cu-rich alloys exhibit a noticeably lower crystallisation temperature Tx of about 510 K, liquidus temperature Tl at approximately 900 K and a more pronounced drop Δ of the heat flux at the glass transition temperature Tg. These criteria indicate that Cu-rich alloys are better glass formers. Transmission electron microscopy (TEM) shows that the specimens with y = 0 and y = 0.34 are composed of an amorphous matrix with minor impurities of CeO2 nanocrystals, which can only be observed via transmission electron microscopy. However, these nanocrystals do not interfere with the formation of the glassy phase and are therefore inert. Magnetic measurements show that Fe-rich alloys possess higher magnetisation at maximum field (Mmax H), peaking at 3.3 and 3 emu/g for y = 1 and y = 0.87, respectively. From ferromagnetism in the latter two alloys, the behaviour turns to paramagnetism for 0 ≤ y ≤ 0.74. Cryogenic measurements on SQUID show that the sample with y = 0 displays two different temperature regions at 2–50 K and 100–300 K. The first one exhibits nearly pure paramagnetic behaviour with Θ = − 0.7, while the second one shows a highly negative Weiss constant of Θ = − 80.6.

We have produced an innovative, theranostic material based on FePt/SiO2/Au hybrid nanoparticles (NPs) for both, photo-thermal therapy and magnetic resonance imaging (MRI). Furthermore, a new synthesis approach, i.e., Au double seeding, for the preparation of Au nanoshells around the FePt/SiO2 cores, is proposed. The photo-thermal and the MRI response were first demonstrated on an aqueous suspension of hybrid FePt/SiO2/Au NPs. The cytotoxicity together with the internalization mechanism and the intracellular fate of the hybrid NPs were evaluated in vitro on a normal (NPU) and a half-differentiated cancerous cell line (RT4). The control samples as well as the normal cell line incubated with the NPs showed no significant temperature increase during the in vitro photo-thermal treatment (ΔT < 0.8 °C) and thus the cell viability remained high (∼90%). In contrast, due to the high NP uptake by the cancerous RT4 cell line, significant heating of the sample was observed (ΔT = 4 °C) and, consequently, after laser irradiation the cell viability dropped significantly to ∼60%. These results further confirm that the hybrid FePt/SiO2/Au NPs developed in the scope of this work were not only efficient but also highly selective photo-thermal agents. Furthermore, the improvement in the contrast and the easier distinction between the healthy and the cancerous tissues were clearly demonstrated with in vitro MRI experiments, proving that hybrid NPs have an excellent potential to be used as contrast agents.

A detailed magnetic study of separated Fe–Pt NPs and Fe–Pt clusters was performed to predict their optimal size and morphology for the maximum saturation magnetization, a factor that is known to influence the performance of a magnetic-resonance-imaging (MRI) contrast agent. Excellent stability and biocompatibility of the nanoparticle suspension was achieved using a novel coating based on hydrocaffeic acid (HCA), which was confirmed with a detailed Fourier-transform infrared spectroscopy (FTIR) study. An in vitro study on a human-bladder papillary urothelial neoplasm RT4 cell line confirmed that HCA-Fe–Pt nanoparticles showed no cytotoxicity, even at a very high concentration (550 μg Fe–Pt per mL), with no delayed cytotoxic effect being detected. This indicates that the HCA coating provides excellent biocompatibility of the nanoparticles, which is a prerequisite for the material to be used as a safe contrast agent for MRI. The cellular uptake and internalization mechanism were studied using ICP-MS and TEM analyses. Furthermore, it was shown that even a very low concentration of Fe–Pt nanoparticles (

The magnetic properties of an Nd-Fe-B-type permanent magnet depend on the microstructure and the chemistry of the material. To compensate for unfavorable microstructural features, such as micron-sized grains of the hard-magnetic phase, the intrinsic coercivity is often enhanced by the addition of heavy-rare-earth elements, but these additions also reduce the magnetization. In some applications, like electro-mechanical devices, a high intrinsic coercivity is only required in certain regions of a magnet. In such cases, using magnets with locally tailored magnetic properties, i.e., multicomponent magnets, would enhance the magnet-containing device’s performance. Here, we propose a spark-plasma-sintering (SPS) approach to the manufacture of multicomponent Nd-Fe-B magnets. By exploiting the SPS-specific processing conditions, namely fast heating rates (100 °C/min) and low consolidation temperatures (≈670 °C), such magnets can be prepared directly from nanostructured melt-spun powders (the one-step SPS approach) or SPS-processed precursor magnets (the two-step SPS approach). Optimizing the SPS processing conditions prevents the grain coarsening related to the pre-existing microstructural inhomogeneities of the powders. The magnetic characterization reveals reliable performance over a wide range of operating temperatures. The high remanent magnetization of a heavy-rare-earth-free powder (Br = 0.82 T) and the high intrinsic coercivity of a powder containing 1.5 at. % Dy (Hci = 2075 kA/m) are preserved in a multicomponent magnet characterized by an abrupt change in magnetic properties close to the interface between the respective magnet parts.

The uniaxial strain of quasi-one-dimensional conductor whiskers of orthorhombic TaS3 at a strain higher than e c ~ 0.8% leads to a sharp increase in the coherence of the properties of a charge density wave (CDW), which manifests itself in its motion in fields higher than threshold field E t . During uniaxial elongation, TaS3 is shown to exhibit the following unusual properties even in weak fields: Peierls transition temperature T P depends nonmonotonically on e, one-dimensional fluctuations weaken near T P , and the coherence length of a charge density increases at T < T P . Investigations in fields higher than E t show that the ultracoherent properties of CDW exist in a wide temperature range and are retained when temperature increases up to T P . These properties of CDW make it possible to observe a sharp increase in E t near T P and an almost jumplike increase in E t at T < 90 K. The increase in E t at T P is explained by a decrease in the coherence volume of CDW because of a fluctuational suppression of the Peierls gap.

Processes taking place during hydrogen desorption from MgH2 thin films were investigated in as-prepared samples and samples modified by argon ion irradiation. Irradiation was used to produce well-defined defects with depth distribution. It was shown that the size, shape, and concentration of Mg nuclei formed during hydrogen desorption from MgH2 thin films depend on the characteristics and distribution of the induced defects. In as-prepared samples the shape of Mg nuclei is spherical, while in irradiated samples, it is highly irregular. Variations in sample colour were observed during hydrogen desorption and before the creation of Mg nuclei. DFT calculations showed that the observed variations in the optical properties of samples can be explained by changes in MgH2 electronic structure -the appearance of an H-vacancy band within the MgH2 energy gap. (C) 2016 Elsevier B.V. All rights reserved.

As the debate about TiO2 food additive safety is still open, the present study focuses on the extraction and characterisation of TiO2 (nano)particles added as a whitening agent to confectionary products, that is, chewing gum pellets. The aim was to (1) determine the colloidal properties of suspensions mutually containing TiO2 and all other chewing gum ingredients in biologically relevant media (preingestion conditions); (2) characterise the TiO2 (nano)particles extracted from the chewing gum coating (after ingestion); and (3) verify their potential photocatalysis. The particle size distribution, in agreement with the zeta potential results, indicated that a small but significant portion of the particle population retained mean dimensions close to the nanosize range, even in conditions of moderate stability, and in presence of all other ingredients. The dispersibility was enhanced by proteins (i.e., albumin), which acted as surfactants and reduced particle size. The particle extraction methods involved conventional techniques and no harmful chemicals. The presence of TiO2 particles embedded in the sugar-based coating was confirmed, including 17–30% fraction in the nanorange (2 layer surrounding the TiO2 particles.

A new ternary phase with a composition Al

The dependence of the magnetic properties on the particle size of recycled HDDR Nd–Fe–B powders was investigated, with the aim to assess the reprocessing potential of the end-of-life scrap magnets via spark plasma sintering (SPS). The as received recycled HDDR powder has coercivity (Hci) = 830 kA/m and particles in the range from 30 to 700 μm (average 220 μm). After burr milling, the average particle size is reduced to 120 μm and subsequently the Hci of fine (milled) powder was 595 kA/m. Spark plasma sintering was exploited to consolidate the nanograined HDDR powders and limit the abnormal grain coarsening. The optimal SPS-ing of coarse HDDR powder at 750 °C for 1 min produces fully dense magnets with Hci = 950 ± 100 kA/m which further increases to 1200 kA/m via thermal treatment at 750 °C for 15 min. The burr milled fine HDDR powder under similar SPS conditions and after thermal treatment results in Hci = 940 kA/m. The fine powder is further sieved down from 630 to less than 50 μm mesh size, to evaluate the possible reduction in Hci in relation to the particle size. The gain in oxygen content doubles for 200 μm). The XRD analysis for fractionated powder indicates an increase in Nd2O3 phase peaks in the finer ( 200 μm) to 460 kA/m in the fine sized particles ( 200 μm) is higher than 930 kA/m and it falls abruptly to just 70 kA/m for the fine sized particles ( 1000 kA/m only up to 100 μm sized fractions with >90% sintered density. The full densification (>99%) is observed only in the coarse fractions. The loss of coercivity and lack of sinterability in the fine sized particles (

Recycling of end‐of‐life Nd–Fe–B magnets is an important strategy for reducing the environmental dangers associated with rare‐earth mining and overcoming the supply risks associated with the rare‐earth elements. In this study, a novel concept for recycling of sintered Nd–Fe–B magnets by directly recovering the matrix Nd2Fe14B grains is presented. The procedure is based on the anodic etching of sintered Nd–Fe–B magnets in a nonaqueous dimethylformamide (DMF)/0.3 mol L−1 FeCl2 bath. Selective recovery of Nd2Fe14B grains was realized within the applied current density intergranular NdFe4B4 > matrix Nd2Fe14B. The total energy consumption of the proposed recycling route is estimated to be 2.99 kWh kg−1, which is comparable to the state‐of‐the‐art methods. However, the proposed recycling route is currently the only procedure that enables repeated recycling of sintered Nd–Fe–B magnets in a closed‐loop system., Here comes the grain again: Selective extraction of Nd2Fe14B grains from sintered Nd–Fe–B magnets has been achieved electrochemically by the preferential etching of their surrounding rare‐earth element‐rich grain boundaries. Recycling of sintered Nd–Fe–B magnets based on the Nd2Fe14B grain recovery represents a circular economy with low energy footprint.

The goal of this study was to justify the reprocessing of recycled HDDR Nd-Fe-B powders with spark plasma sintering (SPS) and to investigate the dependence of the final magnetic properties on SPS and thermal treatment. The initial recycled HDDR powder of the composition Nd13.4Dy0.6Fe78.6B6.1Nb0.4Al0.7 with 4760 ppm O2 content, coercivity (HCi) = 830 kA/m, and large particle size distribution

The magnetic properties of the recycled hydrogenation disproportionation desorption recombination (HDDR) Nd-Fe-B powder, doped with a low weight fraction of DyF3 nanoparticles, were investigated. Spark plasma sintering (SPS) was used to consolidate the recycled Nd-Fe-B powder blends containing 1, 2, and 5 wt.% of DyF3 grounded powder. Different post-SPS sintering thermal treatment conditions (600, 750, and 900 °C), for a varying amount of time, were studied in view of optimizing the magnetic properties and developing characteristic core-shell microstructure in the HDDR powder. As received, recycled HDDR powder has coercivity (HCi) of 830 kA/m, and as optimally as SPS magnets reach 1160 kA/m, after the thermal treatment. With only 1−2 wt.% blended DyF3, the HCi peaked to 1407 kA/m with the thermal treatment at 750 °C for 1 h. The obtained HCi values of the blend magnet is ~69.5% higher than the starting recycled HDDR powder and 17.5% higher than the SPS processed magnet annealed at 750 °C for 1 h. Prolonging the thermal treatment time to 6 h and temperature conditions above 900 °C was detrimental to the magnetic properties. About ~2 wt.% DyF3 dopant was suitable to develop a uniform core-shell microstructure in the HDDR Nd-Fe-B powder. The Nd-rich phase in the HDDR powder has a slightly different and fluorine rich composition i.e., Nd-O-F2 than in the one reported in sintered magnets (Nd-O-F). The composition of reaction zone-phases after the thermal treatment and Dy diffusion was DyF4, which is more abundant in 5 wt.% doped samples. Further doping above 2 wt.% DyF3 is ineffective in augmenting the coercivity of the recycled HDDR powder, due to the decomposition of the shell structure and formation of non-ferromagnetic rare earth-based complex intermetallic compounds. The DyF3 doping is a very effective single step route in a controlled coercivity improvement of the recycled HDDR Nd-Fe-B powder from the end of life magnetic products.

The bulk structure of the η -Al5Fe2 intermetallic compound consists in an ordered framework of pentagonal antiprims with composition Al2Fe inside which nearly continuous chains of fractionally occupied Al sites exist. At low temperature, ordering of these Al channel atoms can occur, leading to various superstructures. Although the Al5Fe2 intermetallic phase is of technological importance being present in protective coating for steel parts, a detailed surface investigation of this compound has not been reported yet. Here we describe the growth of a single crystal of the Al5Fe2 compound by the Czochralski method. Its bulk structure is identified as the low temperature polymorph η ″ . Density Functional Theory calculations were performed to determine its formation enthalpy and its electronic structure. A deep pseudogap is noticeable at the Fermi energy, and this compound is found to be magnetic. Two samples have been extracted, presenting a surface oriented either perpendicular to the channel’s direction ((0 0 1) surface) or parallel to them ((1 0 0) surface). The two surfaces have been investigated by X-ray photoemission spectroscopy, low-energy electron diffraction and scanning tunneling microscopy. Both surfaces exhibit some superstructures of various complexities, whose origin can be explained in the light of density functional theory calculations performed on model surfaces.

The main challenge with electrocatalysis is finding low-cost electrocatalysts that can work efficiently to oxidize the HCHO. Here, we propose a mechanism for the voltammetric formation of a highly active, structurally disordered β-Ni(OH)2/β-NiOOH redox pair on the surface of electrodeposited Ni thin films to achieve an extraordinary catalytic performance with respect to HCHO oxidation in alkaline media. We report electrochemical, XRD and FT-IR measurements on as-deposited and voltammetrically treated (i.e., KOH-modified) Ni thin films, and calculations based on the electrical charge to investigate the changes in the surface composition, crystal structure and related HCHO oxidation activity. We found that the KOH-modification process plays a crucial role in the formation of surface highly active, disordered β-Ni(OH)2/β-NiOOH. The KOH-modified Ni film with the largest amount of the structurally disordered β-Ni(OH)2/β-NiOOH resulted in improved catalytic performance, i.e., an onset overpotential reduced by 400 mV and a catalytic rate increased by 69 mV dec−1. The presented technique has a wide range of applications and provides advances with a novel design idea and a new synthesis strategy for the preparation of highly active, structurally disordered Ni(OH)2/NiOOH redox systems on the surface of Ni thin films and other Ni-based nanostructured electrocatalysts for HCHO oxidation.