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Nanocomposite exchange coupled magnets are most likely the next-generation magnets because of their potentially high energy products. However, their corrosion resistance is a serious concern. The electrochemical behaviour of the nanocomposite magnets is largely unknown. In this study, we investigated the corrosion behaviours of α-Fe/Nd 2 Fe 14 B type nanocomposite magnets in a 3.5 wt% NaCl solution at room temperature using an electrochemical technique. Our results demonstrate that microstructure coarsening can improve the corrosion performance of the magnets, but it greatly degrades the magnetic properties. To enhance the corrosion resistance without scarifying the magnetic performance of the magnets, an amorphous phase with good corrosion resistance is introduced to the grain boundary of α-Fe/Nd 2 Fe 14 B type nanocomposite magnets by controlled melt-spinning process or adding Nb element. The nanocomposite magnets with an interfacial amorphous phase exhibit a lower corrosion current density (22.7 μA/cm 2 ) and higher maximum energy product (23 MGOe) than the magnets without an interfacial amorphous phase. These results indicate that the interfacial modification is beneficial to the improvement of both corrosion resistance and magnetic properties. [ABSTRACT FROM AUTHOR]

In the present work, the Nd 9 Fe 85 B 6−x P x (x = 0–0.3) magnets were prepared via melt rapid quenching method. The P addition greatly improved the microstructure and magnetic properties. The study shows that the P addition increased the nucleation resistance of α-Fe, and hindered the precipitation of the α-Fe phase. The distribution of P in the Nd 9 Fe 85 B 5.9 P 0.1 permanent alloys was characterized by the three-dimensional atom probe (3DAP) technique. Experimental results demonstrated that the P element is mainly concentrated at the grain boundary, inhibiting the growth of soft and hard magnetic crystals. The maximum energy product (BH) max of 20.0 MGOe and coercivity H ci of 6.34 kOe were obtained with the P content at x = 0.1, these values were larger than those of Nd 9 Fe 85 B 6 alloys, with (BH) max = 17.7 MGOe and H ci = 5.61 kOe. The improvements of magnetic properties originate from the enhanced domain-wall-pinning strength and exchange coupling between the soft and hard phases. The 3DAP results demonstrate that the P element mainly concentrates at the grain boundary, which can inhibit the growth of soft and hard magnetic crystals. The improvements of magnetic properties originate from the enhanced domain wall pinning strength and exchange coupling between the soft and hard phases. [Display omitted] • Adding P element is an effective way to improve the magnetic properties. • P mainly concentrates at the grain boundary inhibiting the growth of nanocrystals. • P can enhance both the domain wall pinning and exchange coupling of the magnets. [ABSTRACT FROM AUTHOR]

In this study, the phase evolution, microstructure and magnetic properties of bulk α-Fe/Nd 2 Fe 14 B nanocomposite magnets prepared by a combination of severe plastic deformation (SPD) and thermal annealing have been investigated. Experimental results demonstrate that SPD affects the phase evolution of (Nd,Pr)-Fe-Co-Nb-B alloy upon annealing significantly. The formation of metastable intermediate phases, such as Nd 2 Fe 23 B 3 and Fe 3 B, in the alloy has been effectively inhibited as the strain ε is increased to ε = 6.1, yielding a high volume fraction of α-Fe phase ( V c ∼ 37%) in the bulk α-Fe/Nd 2 Fe 14 B magnets. The grain size of α-Fe and Nd 2 Fe 14 B phases in the magnets decreases with increasing strain. A smaller grain size d = 13.3 nm for α-Fe and 26.5 nm for Nd 2 Fe 14 B is achieved at ε = 6.1, and the magnets show the magnetic properties, ( BH ) max = 14.9 MGOe and H c = 6.4 kOe, larger than those in the α-Fe/Nd 2 Fe 14 B magnets made by directly annealing amorphous ribbons, ( BH ) max = 10.3 MGOe and H c = 4.6 kOe. The enhanced coercivity in the SPD magnets results from an increase in domain-wall-pinning strength. [ABSTRACT FROM AUTHOR]

The slow charge transfer kinetics and water oxidation dynamics hinder the efficient photoelectrochemical (PEC) water splitting of BiVO 4. Here, Nd:BiVO 4 @NiCo-LDH photoanode was successfully prepared by introducing rare earth element Nd with a special 4 f energy level as a dopant and loading a bifunctional NiCo-LDH cocatalyst. The Nd:BiVO 4 @NiCo-LDH photoanode exhibits good PEC performance. The photocurrent density was 4.1 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE), which is about 5.1 times more than that of the unmodified BiVO 4 electrode, and the onset potential was negatively shifted by 399 mV. Various physical characterizations and photoelectrochemical tests indicate that the Nd:BiVO 4 @NiCo-LDH photoanode has higher charge transfer rate and lower charge recombination rate than that of BiVO 4. The NiCo-LDH catalyst serves as a bimetallic oxygen evolution reaction (OER) cocatalyst, where Co cation has hole extraction ability to reduce carrier recombination, and Ni addition increases the active site. The synergistic effect of the two significantly boosts the PEC water oxidation activity of the photoanode. This work has broad prospects for the construction of high-performance water oxidation systems in various photoanodes. [Display omitted] • Nd doping dramatically increases the carrier density and reduces the charge transfer resistance. • NiCo-LDH cocatalyst can inhibit electron-hole recombination and passivate the surface states. • The Nd:BiVO 4 @NiCo-LDH photoanode enhanced the water oxidation performance of BiVO 4. [ABSTRACT FROM AUTHOR]

Abstract Hexagonal M-type SrFe 12 O 19 (SrM) ferrites sintered at different temperatures (1200 °C, 1250 °C or 1300 °C) were obtained via a common ceramic method by using cubic and spindle-like α-Fe 2 O 3 as Fe sources, respectively, and the structural and magnetic properties of specimens were comparatively studied. It was found that the morphology and crystallization of ultimate powder specimens were greatly affected by the morphology of Fe sources. Generally, both the saturation magnetization and coercivity of specimens obtained by using cubic α-Fe 2 O 3 are markedly higher than those of specimens obtained by using spindle-like α-Fe 2 O 3 , except for the sharp coercivity reduction in the specimen obtained by using cubic α-Fe 2 O 3 and a sintering temperature of 1300 °C that can be ascribed to the parallel growth of (008) crystalline face in SrM ferrite. Graphical abstract Image 1 Highlights • Cubic and spindle-like α-Fe 2 O 3 were used as Fe sources to prepare SrFe 12 O 19 ferrites. • The morphology and crystallization of powder specimens were greatly affected by the Fe sources. • The M s and H c of specimens obtained by using cubic α-Fe 2 O 3 were higher. • A sharp reduction of H c results from the parallel growth of (008) crystalline face. [ABSTRACT FROM AUTHOR]

The off-stoichiometric La 1.2 Fe 11.6 Si 1.4 B 0.75 alloys with different solidification rate were prepared by the arc-melting and melt-spinning methods, and the microstructure, magnetic and magnetocaloric properties of the annealed samples were investigated. It is found that the extra La and refined microstructure (induced by rapid cooling technique) shortened the annealing time to 30 min at 1273 K. The B atoms partially dissolved in lattice interstice of 1:13 phase and brings about the lattice expansion, which improves the T C and enhances the MCE of the La 1.2 Fe 11.6 Si 1.4 B 0.75 alloy. The high cooling rate contributes to the depression of thermal and magnetic hysteresis. In the annealed La 1.2 Fe 11.6 Si 1.4 B 0.75 ribbon with wheel speed of 10 m/s, the mass fraction of 1:13 phase is 86.8 wt%, and a large maximum magnetic entropy change of 20.2 J·kg−1K−1 with small thermal and magnetic hysteresis can be obtained at 193 K under field change of 2 T. • The La 1.2 Fe 11.6 Si 1.4 B 0.75 alloys with different solidification rate were prepared. • Main La-rich phase in bulk and ribbon samples is La 5 Si 3 and LaFeSi, respectively. • Excessive content of La and refined microstructure shortened the annealing time. • Interstitial insertion of B improves the T C and magnetocaloric effect. • High cooling rate depresses the thermal and magnetic hysteresis. [ABSTRACT FROM AUTHOR]