•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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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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 <5 mA cm−2 based on the etching priority of phases: metallic Nd > 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.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The first one-step synthesis of dumbbell-like gold-iron oxide nanoparticles has been reported here. Surface functionalization with a biocompatible chitosan matrix allowed us to obtain a novel ...targetable diagnostic and therapeutic tool.
Using template-assisted electrodeposition in partially Au-covered polycarbonate templates, we have successfully deposited equiatomic Co-Pt nanotubes with an external radius R of 100nm, lengths L of ...800-2000nm and tube-wall thicknesses of 70nm. By applying different characterization methods - vibrating-sample magnetometry and combined atomic and magnetic force microscopy - we have shown that in as-deposited face-centred cubic Co-Pt nanotubes the magnetization in the remanent state can be described with a vortex-type of closure. Such curling of the magnetization distribution has its origin in the minimization of the demagnetizing field that arises from the surface or volume charges. The demagnetization of single-vortex-type nanotubes proceeds gradually and exhibits only a modest hysteresis. Such nanotubes with a single vortex-type of magnetization distribution possess the unique property of emitting no stray fields in the remanent state, despite their elongated shape, and therefore represent perfect candidates for magnetoresistive random-access-memory devices and for biomedical applications such as targeted drug delivery.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The preparation of ZnSn-substituted barium ferrite films by sputtering deposition was studied. The as-sputtered films were amorphous, and annealing at a minimum of 750
°C was required to crystallize ...the films, based on the X-ray diffraction analysis and the magnetic measurements. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopic microanalysis confirmed that the films were single phase with the composition BaZn
x
Sn
x
Fe
12−2
x
O
19,
x=0.2−0.3, and their thicknesses were 0.4–1.0
μm when annealed at 750–900
°C. Atomic and magnetic force microscopy studies showed no significant grain growth upon annealing and that the films consisted of single-domain grains forming interaction-cluster-type domains. The natural ferromagnetic resonance frequency was determined at around 4
GHz, together with substantial magnetic losses that make these films promising candidates for microwave absorbers.
► ZnSn-substituted barium ferrite films can be prepared with a sputtering-deposition followed by annealing at 750–900
°C. ► The ZnSn-substituted barium ferrite films consist from magnetically coupled single-domain grains. ► The ZnSn-substitution in barium ferrite films reduces the ferromagnetic resonance from 48 to 4
GHz. ► The ZnSn-substituted barium ferrite films show large magnetic losses at 7–15
GHz. ► The ZnSn-substituted barium ferrite films are suitable for microwave absorbers.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We have investigated the effect of the microstructure on the magnetic properties of Co-Pt nanowires (NWs) with diameters of 15, 50, and 80 nm. These Co-Pt NWs were fabricated by using polycarbonate ...membranes with different pore diameters via direct electrodeposition. A detailed transmission-electron-microscopy analysis revealed that the Co-Pt NWs transform from a polycrystalline to a single-crystalline-like structure along the growth direction of the NWs. The selected-area electron-diffraction investigation of the Co-Pt NWs with 50 nm diameters revealed a fcc-dominant crystal structure, while the 15 and 80 nm NWs were composed of an intermixture of fcc and hcp phases. This investigation allows us to understand the magnetic hysteresis loops of the Co-Pt NW arrays. Furthermore, the magnetic domains of the individual Co-Pt NWs were studied with magnetic force microscope (MFM), and the MFM contrasts for the 50 nm and 80 nm diameter NWs are interpreted as consisting of z-vortices.
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 Ni nanowires-based electrodes for formaldehyde (HCHO) detection were fabricated via a template-assisted electrodeposition. The as-deposited Ni nanowires (NWs) were characterized by scanning ...electron microscope (SEM). In order to form an active redox couple of Ni(OH)2/NiOOH on the surface of nanowires, the Ni NWs were electrochemically modified in 0.5 mol L−1 KOH using cyclic voltammetry. The presence of Ni(OH)2/NiOOH on the surface of Ni NWs was confirmed by transmission electron microscopy (TEM). Furthermore, the ability of modified Ni NWs-based electrode (i.e., receptor element) was investigated for HCHO electro-oxidation in alkaline media via cyclic voltammetry and amperometry. The fabricated Ni NWs-based electrode exhibited fast response (3s), good selectivity, a high sensitivity and low limit of detection 0.8 μmol L−1.
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