Ce substitution level in Nd-Fe-B magnets has been significantly increased via the binary main phase (BMP) approach, i.e. sintering the mixture of Ce-free and Ce-containing RE2Fe14B (RE, rare earth) ...powders. REFe2 phase that forms in the high Ce-containing Nd-Ce-Fe-B magnets has been considered to be harmful to magnetic performance due to its soft magnetism. In this work, we found that REFe2 phase with lower melting point than the 2:14:1 phase plays positive role on optimizing the microstructure and retaining magnetic performance of the Nd-Ce-Fe-B BMP magnets. The wettability of 2:14:1 phase can be improved by sintering above the melting point of REFe2 phase, which promotes densification of the magnet and the formation of continuous and smooth grain boundary (GB) phases. This contributes to the weakened short-range exchange coupling between adjacent grains, hence ensures superior magnetic performance of BMP magnets to the single main phase (SMP) ones with the same average composition. As a result, magnetic properties of Br = 12.4 kG, Hcj = 9.0 kOe and (BH)max = 36.7 MGOe can be obtained even when 45 wt % Ce substitutes for Nd in the BMP magnets.
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To improve the thermal stability of the Nd-Ce-Fe-B sintered magnets, Y was incorporated via the binary main phase (BMP) approach. At the same substitution level for Nd (9wt%), the absolute value of ...the coercivity temperature coefficient from 293 to 393K for the Nd-Ce-Y-Fe-B magnet is 16.2% lower than that for the Nd-Ce-Fe-B one. This is attributed to the weakened temperature dependence of the magnetocrystalline anisotropy field and the magnetization as Y preferably enters into the 2:14:1 phase. It suggests that Y and Ce co-substitution for Nd is appealing to prepare low-cost RE-Fe-B permanent magnets with improved thermal stability.
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Inferior intrinsic magnetic properties of (La/Ce)2Fe14B to Nd2Fe14B compound pose a big challenge for the Nd-La-Ce-Fe-B sintered magnets to provide an equivalent performance to the commercial Nd-Fe-B ...ones. To suppress the magnetic dilution, La/Ce distributions within 2:14:1 phase are intentionally tailored in the present work. At the same La-Ce substitution level of 12 wt%, the coercivity has been substantially increased to 1.36 T by constructing the coexisting Nd-rich shell @ La/Ce-rich core and La/Ce-rich shell @ Nd-rich core morphologies, compared to the La/Ce homogenously distributed magnet (0.76 T) and the one with singular Nd-rich core surrounded by La/Ce-rich shell (0.82 T). This is attributed to combined effects of magnetically hardening Nd-rich shell in suppressing the reversal domain nucleation, and continuous grain boundary layer in reducing the short-range exchange coupling between adjacent ferromagnetic grains. It may act as part of endeavors to promote the Nd-La-Ce-Fe-B sintered magnets for commercial application.
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•Nd-La-Ce-Fe-B BMP magnets with dual type core-shells exhibit a highest coercivity.•Magnetically hardening Nd-rich shell can strengthen the low-HA La/Ce-rich grains.•Thick GB layers in the BMP magnets also contribute to the coercivity increment.•La/Ce distribution is crucial to enhance the coercivity of Nd-La-Ce-Fe-B magnets.
Benzotriazole-loaded polydopamine/polyaniline (BTA@PDA/PANI) microcapsules are prepared vis the combination of a hard template method and in-situ polymerization. The PDA/PANI hollow microspheres are ...first prepared using SiO2 as a hard template and etching them with hydrofluoric acid. The BTA corrosion inhibitor is then loaded into the PDA/PANI hollow microspheres to obtain the BTA@PDA/PANI microcapsules. The mean particle size and shell thickness of the synthesized microcapsules are 8.3 and 2.1 µm, respectively. The load capacity of BTA is above 20 wt%. The corrosion resistance of epoxy coatings with different contents and types of microcapsules is compared by saline immersion and electrochemical impedance tests. A scratched coating with 1 wt% BTA@PDA/PANI microcapsules has the best anti-corrosion effect. The synergistic anticorrosion mechanism of BTA, PDA and PANI is revealed and confirmed.
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Retaining chemical heterogeneity of 2:14:1 grains and forming continuous grain boundaries are two critical contributions to the strong magnetism in multi-main-phase (MMP) magnets. However, the ideal ...grain boundary microstructure is usually achieved at the expense of weakening the chemical heterogeneity, which poses a big challenge. Here we report a versatile strategy to balance the chemical heterogeneity and microstructure of MMP Nd-Ce-La-Fe-B magnets through tailoring liquid-phase-sintering. At optimum 1040 °C sintering, MMP magnet with 27 wt% Ce–La substitution level exhibits an equivalent weight-bearing capacity to 40MGOe commercial Nd-Fe-B, which is attributed to the joint contributions from retained chemical heterogeneity, essential densification, homogeneous grain size distribution and continuous intergranular phase network with ordered Ia3¯ structure. When shifting sintering temperature Ts towards the higher or lower range, the deteriorated magnetic properties are dominated by distinct restraints. With Ts above 1040 °C, the decreased coercivity is mainly restrained by the negative role of gradual chemical homogenization and abnormal grain growth, as verified by experimental and simulated results. However, with Ts below 1040 °C, the unsatisfactory magnetic performance mainly roots in insufficient densification and discontinuous grain boundary. These advances may deepen our understanding on designing high-performance MMP magnets with balanced contributions from modified microstructure and retained chemical heterogeneity.
For the first time, here we present that liquid-phase-sintering provides a versatile strategy to balance the microstructure and chemical heterogeneity for multi-main-phase (MMP) magnets. Optimal sintering of 1040 °C upon 27 wt% Ce–La substitution level yields an equivalent weight-bearing magnetic strength to the 40 MGOe starting magnet (a), which is attributed to on one hand, the modified microstructure (appreciable densification, homogeneous grain size distribution, continuous intergranular phase network with ordered Ia3¯ structure), and on the other hand, the retained chemical heterogeneity of 2:14:1 main phase grains (d). Comparably, low-temperature sintering leads to poor densification and discontinuous grain boundary that cannot decouple neighboring grains (b); high-temperature sintering results in abnormal grain growth and gradual chemical homogenization (c). Above findings provide a new recipe to design MMP Nd-Ce-La-Fe-B magnets with balanced competitive contributions from modified microstructure and retained chemical heterogeneity. Display omitted
•For CeLa-27 MMP magnet, optimum 1040 °C sintering yields an equivalent magnetic strength to 40 MGOe commercial Nd-Fe-B.•Essential densification, continuous GB layer and retained chemical heterogeneity lead to preferable magnetic properties.•Different dependences of chemical heterogeneity and microstructure on Ts lead to distinct mechanisms of magnetic property.•Tailoring sintering provides a versatile route to balance microstructure and chemical heterogeneity of MMP magnets.
To improve coercivity without sacrificing other magnetic performance of NdFeB sintered magnets, a low melting point Dy32.5Fe62Cu5.5 alloy was introduced as an intergranular additive. Magnetic ...properties and microstructure of the magnets with different Dy32.5Fe62Cu5.5 contents were studied. At the optimum addition of 3wt%, coercivity Hcj was enhanced from 12.7 to 15.2kOe, the maximum magnetic energy product (BH)max was simultaneously increased from 46.6 to 47.8MGOe, accompanied by a slight reduction in remanence Br. Further investigation on microstructure and grain boundary composition indicated that the enhanced Hcj and (BH)max could be attributed to the refined and uniform 2:14:1 phase grains, continuous grain boundaries and a (Nd,Dy)2Fe14B hardening shell surrounding the 2:14:1 phase grains.
•Low melting-point Dy32.5Fe62Cu5.5 alloy was introduced to NdFeB magnets.•The doped magnet exhibits enhanced coercivity and maximum energy product.•(Nd,Dy)2Fe14B shell was expected to form in the surface of Nd2Fe14B grains.•The continuous grain boundary layer formed between neighboring Nd2Fe14B grains.
A series of flat-sheet asymmetric mixed matrix membranes (MMMs) have been fabricated with MOF-5, Cu3(BTC)2, and MIL-53(Al) as fillers and PI polymer as a matrix through the dry–wet phase inversion ...method. After the surface modification by coating a PAA solution (15% wt) on the top of the obtained membrane, a thin defect-free selective skin in the MMM is obtained. The permeance of various gases such as H2, He, CH4, N2, and CO2 and their gas pair selectivity have been investigated, respectively. The results show that Cu3(BTC)2/PI MMM possesses the best gas separation performance with H2 permeance of 0.44 GPU and H2/CH4 selectivity of 100. In addition, the mechanism of MOF fillers in MMMs has been further revealed by the interaction analysis between MOF fillers and PI chains.
The Ti
3
C
2
and g-C
3
N
4
NS were obtained first, and the CdS/Ti
3
C
2
/g-C
3
N
4
NS Z-scheme composites were prepared via a facile hydrothermal synthesis, and their photocatalytic properties were ...investigated. The g-C
3
N
4
NS with a high surface area displayed higher adsorption and degradation capacity. Compared with Ti
3
C
2
/g-C
3
N
4
NS and CdS, the visible light photocatalytic activity of CdS/Ti
3
C
2
/g-C
3
N
4
NS composites was improved. The as-synthesized CTN-4:1 composite exhibited outstanding photocatalytic performance for degradation of orange II, approximately 3.2 and 10.7 times higher than that of Ti
3
C
2
/g-C
3
N
4
NS and CdS, respectively. The fabrication of CdS/Ti
3
C
2
/g-C
3
N
4
NS Z-scheme heterostructure using Ti
3
C
2
as electron transfer medium improved the separation ability of the photoinduced e
−
-h
+
pairs, thereby leading to the improvement of visible light-driven photocatalytic activity. This finding provides new insights into the construction of high efficiency Z-scheme heterostructure photocatalyst.
Researchers have increasingly concentrated on loneliness in the workplace as a crucial factor influencing the mental health of employees and the viability of telework. In contrast, the current ...understanding of the strategies mitigating workplace loneliness and how leaders utilize their behaviors to impact followers' loneliness remains limited. Since servant leadership values the emotional needs of followers and displays a high level of empathy, this study investigated the direct and indirect effects of servant leadership on workplace loneliness. In this study, 267 employees (mean age = 31.5 years) from 28 provinces in China were recruited to participate in this survey. We proposed that servant leaders motivate their own empathic communication and other followers' empathic communication to reduce lonely followers' workplace loneliness. This research further examined the relationship between the leader's and colleagues' empathic communication, and the two jointly mediate the connection between servant leadership and followers' workplace loneliness. We constructed a serial mediation model to examine the relationships between servant leadership, leader's empathic communication, colleagues' empathic communication, and workplace loneliness. The results indicate that servant leadership creates a cycle of empathy and provides insights into building a culture of empathy to improve employee well-being.
To enhance coercivity and reduce the rare-earth consumption of Nd–Fe–B sintered magnets simultaneously, low melting point Dy69Ni31 (at%) powders are introduced into a slightly off-stoichiometric ...Nd2Fe14B (2:14:1 phase) (Pr, Nd)12.36FebalB6.09 (at%) starting magnet. Because of insufficient rare-earth element, the starting magnet possesses discontinuous intergranular grain boundaries (GBs) that cannot decouple the 2:14:1 phase grains well, hence leading to a low coercivity of only 9.53kOe. The Dy69Ni31 additive provides extra rare-earth that improves the liquid-phase sintering with the formation of continuous intergranular GBs, accompanied by the diffusion of Dy towards surface region of the 2:14:1 phase grains. A significant increment in coercivity of 6.25kOe is realized with a slight reduction in remanence by −3.0% per unit at% Dy. Satisfactory magnetic performance with (BH)max=47.49 MGOe, Br=13.92 kGs and Hcj=13.93kOe, is obtained in the magnet containing only 12.92 at% rare-earth elements, in which 0.68 at% Dy is included. It combines advantages of the modification of intergranular GBs and the formation of a magnetically hardening shell surrounding 2:14:1 phase grains, which can be a promising approach to fabricate low rare-earth and high performance Nd–Fe–B magnets for mass production.
•Dy–Ni powders are introduced into slightly off-stoichiometric 2:14:1 type magnets.•Both morphology and composition are restructured in intergranular regions.•Rapid increment of coercivity and slight reduction in remanence are obtained.•Total rare-earth consumption is reduced simultaneously.
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