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.
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Growth of Pb(Mg1/3Nb2/3)O3–33PbTiO3 thin films by pulsed-laser deposition directly on non-conductive SrTiO3 substrates for d33-mode energy harvesters (EHs) was studied, as they offer a higher ...figure-of-merit than d31-mode EHs. It was found that a high defect density, present in the film grown at 0.13 mbar, is manifested in the form of splitting of the (00l) peaks in X-ray diffraction, which was avoided by raising the process pressure to 0.27 mbar. Nevertheless, both films grow in a combined 2D and 3D manner, and form out-of-phase boundaries (OPBs) with a PbO rock-salt structure between the as-grown islands. It was found that the overall composition of the sample with optimized structural and functional properties was Pb1.07Mg0.19Nb0.44Ti0.32O3, which is close to stoichiometric. The surplus of Pb is compensated by the formation of OPBs and Mg deficit maintains macroscopic electroneutrality. In-plane and out-of-plane relative permittivities of 1900 and 980, respectively, imply macroscopic out-of-plane polarization.
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Titanium dioxide (TiO2) nanotubes obtained by the anodic oxidation of titanium metal foils can be used for the photocatalytic degradation of organic pollutants. The aim of our study was to determine ...the influence of the titanium foil’s surface treatment on the final morphology of the TiO2 nanotubes and their photocatalytic activity. In our experiments, we used two different titanium foils that were electropolished or untreated prior to the anodic oxidation. The morphologies of the starting titanium foils and the resulting TiO2 nanotube layers were investigated and the photocatalytic activities measured by the decomposition of caffeine under UV irradiation. Our results showed that electropolishing of the starting foils produced a more uniform and smoother TiO2 nanotubes surface. In contrast, the TiO2 nanotube surfaces from untreated titanium foils mimic the initial surface roughness of the titanium foil. A comparison of the photocatalytic properties of the TiO2 nanotube layers obtained from the untreated and electropolished titanium foils showed that electropolishing does not necessarily improve the photocatalytic properties of the resulting TiO2 nanotube layer. It was found that the determining factors influencing the photocatalytic activity are the chemical impurities (Ti-nitride) on the surface of the titanium foils and the surface roughness of the TiO2 nanotube layer. The highest photocatalytic activity was achieved with the anodized untreated foil with the minimal presence of Ti-nitride and a relatively high roughness of the TiO2 nanotubes.
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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.
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Anisotropic sintered magnets based on the Nd2Fe14B phase doped with Tb were prepared using a grain-boundary diffusion process (GBDP) in order to enhance their coercivity. A FEGSEM microstructural ...analysis revealed that these GBDP magnets had a core-shell structure, where thin, Tb-rich, (NdTb)2Fe14B shells are formed on the original matrix Nd2Fe14B grains after diffusion of the Tb. This shell thickness varies from a few tens of nanometres in the middle of the magnet up to a few micrometers near the edge. The exact chemical composition of these shells was determined using EDS and WDS electron-probe microanalyses, which were modified and optimized for submicrometer scale analyses. When analyzing the common Nd–Lα, Tb–Lα and Fe–Kα lines a mutual multiple overlap in the EDS spectra is present and, as a result, an accurate quantitative analysis was only feasible when using WDS. Using this technique we were able to achieve a lateral analytical resolution of 0.4μm. A further improvement in resolution, down to 0.15μm, was realized with a dedicated set-up using low-voltage EDS, analyzing the “atypical” low-energy Nd–Mα, Tb–Mα and Fe–Lα lines. Quantitative analyses confirmed that the reaction phase (NdxTb1−x)2Fe14B is formed after the diffusion of Tb with the equilibrium concentration of Tb being equal to x≈0.5, i.e., with the atomic ratio of Nd/Tb equal to 1/1. We also found that a relatively sharp Tb concentration gradient from the shell to the core occurs within a length of ≈0.5μm, while the Fe concentration remains unchanged. In terms of magnetic properties, the Tb-doping significantly increased coercivity by ≈30% while the remanence remained at the same value as in the undoped Nd–Fe–B.
► Nd–Fe–B sintered magnets were doped with Tb using grain-boundary diffusion process. ► A tiny core-shell reaction phase was formed around the Nd2Fe14B matrix grains. ► EDS and WDS analyses confirmed (Nd0.5Tb0.5)2Fe14B equilibrium shell composition. ► Coercivity of Tb-doped Nd–Fe–B increases by 30% without a drop in remanence.
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This study focused on the crystal and electronic structures of a newly discovered phase in the Al-Cr-Sc system. The latter two species do not mix in a binary alloy, but can be alloyed with aluminium ...in the vicinity of the Al2−xCrxSc composition, where 0.3 < x < 0.5. After preparation of the pure constituents via arc melting, high-temperature annealing at 990 °C for 240 h was required to achieve full mixing of the elements. A detailed characterisation of the crystal structure, alloy microstructure and stability was obtained using single-crystal X-ray diffraction (SCXRD) and powder X-ray diffraction (PXRD), in addition to transmission electron microscopy (TEM), especially in high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) mode, scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDXS) and differential scanning calorimetry (DSC) measurements. The crystal structure was refined to a hexagonal unit cell of the MgZn2 type, space group no. 194, P63/mmc, which belongs to the Laves phases family. Special attention was paid to the occupancy of the crystallographic sites that were filled by both Cr and Al atoms. First-principles calculations based on the density functional theory (DFT) were performed to investigate the electronic structure of this ternary phase. The total density of states (DOS) exhibited a pronounced sp character, where a shallow pseudo-gap was visible 0.5 eV below the Fermi energy that brought a small but definite contribution to the thermodynamic stability of the compound.
The collapse of communism in the Soviet Union and Eastern Europe was supposed to bring about the "end of history" with capitalism and liberal democracy achieving decisive victories. Europe would now ...integrate and reconcile with its past. However, the aftershocks of the financial crisis of 2008-the rise in right-wing populism, austerity politics, and mass migration-have shown that the ideological divisions which haunted Europe in the twentieth century still remain. It is within this context that Post-Communist Malaise revives discourses of political modernism and revisits debates from Marxism and seventies film theory. Analyzing work of Theo Angelopoulos, Vera Chytilová, Srdjan Dragojevic, Jean-Luc Godard, Miklós Jancsó, Emir Kusturica, Dušan Makavejev, Cristi Puiu, Jan Švankmajer, Andrei Tarkovsky, and Béla Tarr, the book focuses on how select cinemas from Eastern Europe and the Balkans critique the neoliberal integration of Europe whose failures fuel the rise of nationalism and right-wing politics. By politicizing art cinema from the regions, Post-Communist Malaise asks fundamental questions about film, aesthetics, and ideology. It argues for the utopian potential of the materiality of cinematic time to imagine a new political and cultural organization for Europe.
The collapse of communism in the Soviet Union and Eastern Europe was supposed to bring about the “end of history” with capitalism and liberal democracy achieving decisive victories. Europe would now ...integrate and reconcile with its past. However, the aftershocks of the financial crisis of 2008—the rise in right-wing populism, austerity politics, and mass migration—have shown that the ideological divisions which haunted Europe in the twentieth century still remain. It is within this context that Post-Communist Malaise revives discourses of political modernism and revisits debates from Marxism and seventies film theory. Analyzing work of Theo Angelopoulos, Vera Chytilová, Srdjan Dragojevic, Jean-Luc Godard, Miklós Jancsó, Emir Kusturica, Dušan Makavejev, Cristi Puiu, Jan Švankmajer, Andrei Tarkovsky, and Béla Tarr, the book focuses on how select cinemas from Eastern Europe and the Balkans critique the neoliberal integration of Europe whose failures fuel the rise of nationalism and right-wing politics. By politicizing art cinema from the regions, Post-Communist Malaise asks fundamental questions about film, aesthetics, and ideology. It argues for the utopian potential of the materiality of cinematic time to imagine a new political and cultural organization for Europe.
•Pulse electrodeposition with ton=2s and toff=10s results in formation of homogenous nanowires.•2.5µm long nanowires with composition of Fe55+5Pd45+5 were deposited.•As deposited nanowires have fcc ...crystal structure and are magnetically soft.•Thermal annealing induces the development of the L10 phase which resulted in the HC=122kA/m.
Fe–Pd nanowires were synthesised in anodic alumina templates by applying both potentiostatic and pulsed electrodeposition regimes. When using potentiostatic deposition, only fragmented nanowires were obtained; however, the use of pulse deposition was shown to be effective for producing solid nanowires. In order to achieve this, different on-times for the deposition and off-times between the pulses in an electrolyte with a constant concentration of Fe(III) and Pd(II) ions at pH 9 were employed. Homogeneous nanowires with the composition Fe55±5Pd45±5, lengths of 2.5μm and diameters of 200nm were synthesised under the following pulsed conditions Eon=−1.4V, ton=2s and Eoff=−0.1V, toff=10s for 5000 cycles. The as-deposited nanowires had a fcc crystal structure and were magnetically soft (HC≈5kA/m) with the easy axis of magnetization perpendicular to the long axes of the nanowires, mainly due to the dipolar coupling within the template. In order to promote the ordering into the L10 phase, annealing in the temperature range 400–700°C for 1–9h in Ar+7% H2 was performed. The highest coercivity of 122kA/m was achieved by annealing at 600°C for 5h.
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•Riverbed biofilms were examined in situ during colonization and over four seasons.•The impact of pollution with PET fibres was investigated.•PET inhibited biofilm activity and affected ...community-level metabolic profiles.•Utilization of synthetic polymers was higher in sediments with more PET fibres.
Worldwide, the production of plastics is increasing, and plastic pollution in aquatic environments is a major global concern. Under natural conditions, plastic weathers to smaller pieces called microplastics (MP), which come in various shapes, with fibers often being the most common in freshwater sediments. The hyporheic zone, an ecotone between surface and groundwater, is important for the transport and fate of all MP particles. The main metabolic pathways in rivers take place in the hyporheic zone and are driven by a diverse microbial community. The objective of this study was to investigate in situ whether the presence of PET fibers in riverbed sediments affects patterns of colonization and the seasonal dynamics of microbial metabolic activities in the hyporheic zone. The effects of the presence of PET on microbial metabolism were evaluated in situ over a month (colonization study) and over a year (seasonal study) by measuring total protein content (TPC), and microbial respiration as respiratory electron transport system activity (ETSA) and by community-level physiological profiling (CLPP). Additionally, PET fibers were examined under a scanning electron microscope (SEM), and isotopic analysis (δ13C) of PET was performed after one year of exposure to field conditions. The findings demonstrated that during colonization and biofilm formation, and also over the seasons, the date had a large and significant impact on biofilm growth and activity, while PET presence slightly suppressed microbial biomass (TPC) and respiratory activity (ETSA). Overall microbial activity was repressed in the presence of PET fibers but there was a higher capacity for the utilization of complex synthetic polymer substrates (i.e., Tween 40) which have previously been linked to polluted environments. SEM micrographs showed diverse microbial communities adhering to PET fibers but little surface deterioration. Similarly, isotopic analysis suggested little deterioration of PET fibers after one year of in situ conditions. The study indicated that PET fibers present in riverbed sediments could have impacts on the metabolic functioning in rivers and thus affect their self-cleaning ability.
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