查看更多>>摘要：Herein, the sandwich-like Fe3O4@FeS2@C@MoS2 composite was prepared via coating MoS2 shell on the surface of core/shell Fe3O4@C composite. During the coating process, Fe3O4 was partly sulfurized to FeS2, whose energy band was well-matched with that of MoS2 for a Z-scheme heterojunction. The residual Fe3O4 ensured the rapid separation of heterojunction by magnet. In photo-Fenton reaction, 81.5% of tetracycline was degraded within 40 min, which was higher than the sum of degradation efficiency of Fenton reaction and photocatalytic reaction. 93.6% of the degradation efficiency in the 1st cycle was still maintained after 5 cycles. In mechanism study, the sources of ?OH, ?O2-, 1O2 and h+ were carefully traced, and the contributions of these radicals followed the order: ?OHsurf>?O2->1O2>h+>?OHfree. An inner electric field was built at the interface by analyzing the energy band and work functions, which driven the charge carriers transfer followed a Z-scheme path. The findings in this manuscript were beneficial for designing catalysts with high photo-Fenton activity.
查看更多>>摘要：High-performance and inexpensive multifunctional electrocatalysts, which can drive different electrocatalytic reactions in the same electrolyte, are vital for energy conversion and storage applications. A novel laser-based synthesis method for the preparation of multifunctional Ni–CuO nanocomposites, which can be utilized in methanol oxidation reaction (MOR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER), is described herein. The growth dynamics of CuO in presence of Ni nanoparticles, as well as the corresponding effects on the electrocatalytic activity, are investigated. The prepared electrocatalyst exhibits trifunctional catalytic activity. The controlled change of the CuO morphology into homogenous nanospheres with more electrochemically accessible Cu sites results in excellent MOR activity with a high current density of 10.21 mA cm?2 at the vertex potential. Moreover, the electrocatalyst displays high oxygen and hydrogen turnover capability with outstanding operational durability in OER and HER. It is demonstrated that Ni–CuO can potentially be used as a bifunctional water splitting electrocatalyst in alkaline conditions. Importantly, this work provides a viable methodology, which can be employed for the development of efficient and stable multifunctional electrocatalysts by pulsed laser ablation.
查看更多>>摘要：In this study, an alloy conforming to the composition Ni50Ti48V2 (at. %)was cast in a vacuum induction melting furnace, and hot deformation tests were performed on the samples using a GLEEBLE 3800 thermomechanical simulator over a range of strain rates (0.01 s?1, 0.1 s?1, 1 s?1, 10 s?1) and temperatures (1073 K, 1173 K, 1273 K, 1373 K). Deformation processing maps, which are a combination of instability map and efficiency map, were derived based on dynamic materials model. The mechanisms of deformation were interpreted based on stress-strain plots, kinetic analysis, process maps and microstructure. Material constants along with activation energy, which was found out to be 205.58 kJ/mol., were calculated. Since strain also plays a major role in this analysis, a Strain-Compensated Arrhenius-Type (SCAT) model was developed. A comparison between strain-compensated Arrhenius type and artificial neural network models (ANNM) was made through the use of relative error, adjusted R2 values and root mean square errors between the predicted and experimental stress values. All three parameters unanimously indicated the use of ANNM for predicting the stresses developed in the material during hot deformation process. Finally, the flow stress required for the onset of dynamic recrystallization (DRX) was calculated using work hardening theory and correlated with the power dissipation efficiency generated from processing maps. Results show that Ni50Ti48V2 exhibits the highest power dissipation efficiency of 43.50% when deformed at 1173 K and 0.01 s?1. The least critical stress of 58.014 MPa was also captured under the same working conditions. Results are elaborately discussed in the paper.
查看更多>>摘要：In the present study, dense and crack-free Hastelloy X (HX) thin cylindrical struts with diameters ranging from 0.25 mm to 2 mm were fabricated through laser powder bed fusion (LPBF). Their crystallographic texture was found to transition from a<110> || building direction (BD) fiber texture in the 2 mm strut, to a single crystal in the 0.25 mm strut with<110> || BD. The size of the cellular sub-grain microstructure increased as the strut diameter decreased and was linked with an inverse trend in microhardness, which was the highest in the 2 mm strut due to a smaller cell size. Lower hardness measurements in the regions close to the strut edges was also related to larger cell size observed in these regions. From tensile testing, elongation to fracture values were measured in the range of 35–50%. Deformation twinning and lattice rotation after testing were observed. Differences in strength from between different struts of different diameter are also discussed. Finally, fractography analysis further confirmed the ductile fracture behavior.
查看更多>>摘要：The study on inhibiting the release of ammonia from Mg(BH4)2·2NH3 has attracted the attention of many researchers. In this paper, a facile method was used to introduce HCS (hydriding combustion synthesis) processed Mg95Ni5 into the Mg(BH4)2·2NH3 system, which successfully suppressed the release of ammonia completely. The composite shows the best hydrogen desorption kinetics when Mg(BH4)2·2NH3 and Mg95Ni5 hydride were mixed in a mass ratio of 2:1. The initial dehydrogenation temperature of the composite is as low as 75 °C, which is 70 °C lower than that of Mg(BH4)2·2NH3. In the thermal desorption test, when the temperature rises to 500 °C, the amount of hydrogen released is 11.66 wt%, reaching 98.4% of the total amount of hydrogen released. The excellent performance of inhibiting ammonia and releasing hydrogen is attributed to the dual regulation effects of MgH2 and nickel. Magnesium hydride can effectively inhibit ammonia release, and the high dispersibility of nickel improves the kinetic performance of MgH2 in the system. This study further confirms the ammonia suppression effect of MgH2 on Mg(BH4)2·2NH3 and provides ideas for improving the kinetic performance of the composite system.
查看更多>>摘要：Complex metal hydrides have recently gained interest as solid electrolytes for all-solid-state batteries due to their light weight, easy deformability, and fast ion mobility at elevated temperatures. However, increasing their low conductivity at room temperature is a prerequisite for application. In this review, two strategies to enhance room temperature conductivity in complex metal hydrides, nanostructuring and nanocomposite formation, are highlighted. First, the recent achievements in nanostructured complex metal hydride-based ion conductors and complex metal hydride/metal oxide nanocomposite ion conductors are summarized, and the trends and challenges in their preparation are discussed. Then, the reported all-solid-state batteries based on complex metal hydride nanocomposite electrolytes are highlighted. Finally, future research directions and perspectives are proposed, both for the preparation of improved metal hydride ion conductors, as well as metal hydride-based all-solid-state batteries.
查看更多>>摘要：FeCoB/Ru/FeCoB trilayers with a uniaxial magnetic anisotropy were deposited on (011)-cut lead magnesium niobate-lead titanate (PMN-PT) single crystal ferroelectric substrates using a compositional gradient sputtering (CGS) method. Ultrahigh optical mode resonance frequencies from 11.76 to 18.96 GHz at zero magnetic field were achieved due to the strong interlayer exchange coupling between FeCoB films through Ru spacer. In this study, two orthogonal magnetic anisotropic fields (one is CGS induced anisotropy field HKCGS and the other is the piezoelectric stress-induced anisotropy field HKME) were set to realize electric-field (E-field) controlled switch of magnetic moment configuration through their competition. As a result, the optical mode resonance intensity can make reversible 90° rotation under applied E-field, while the advantages of ultrahigh frequency optical mode resonance in trilayers are still maintained because the interlayer exchange coupling is not destroyed by magnetoelectric coupling. The ultrahigh resonance frequency and E-field tunable and reversible FMR rotation in these trilayers provide a potential route to guide microwave flow in multifunctional microwave and spintronic devices.
查看更多>>摘要：A cost-affordable and ultrahigh-strength metastable β titanium alloy with a composition of Ti-6Al-1Mo-1Fe-6.9Cr has been designed by high-throughput diffusion couple technique. The alloy was heat treated along different regimes to investigate the effects of heat treatments on phase transformation, microstructure evolution, and tensile properties. The results showed that the aging strength of the alloy after solution treatment at 840 °C was higher than that at 800 °C due to the more αs precipitation during aging, while solution treatment at 840 °C and aging caused slight decrease of tensile ductility because of the lower αp-phase fraction during solution treatment. Moreover, the formation TiCr2 Laves phase at aging temperatures above 540 °C resulted in remarkable reduction of tensile ductility. Owing to the multiple-hierarchy α precipitations dispersed into the β matrix, two excellent strength-ductility combinations were successfully obtained for the alloys after solution treatment at 800 °C/840 °C and aging at 470 °C with the ultimate tensile strength and tensile elongation values of 1395 MPa/16.0% and 1614 MPa/9.7%, respectively.
查看更多>>摘要：Interstitial alloying has been proved to be a promising option to improve the mechanical properties in various commercial alloys. Herein, we systematically investigate the microstructure evolution and mechanical property change of CoCrFeMnNi high-entropy alloys (HEAs) with varied nitrogen contents as an interstitial alloying element. To equilibrate the thermal history, all the alloys are heat-treated as follows: homogenization (1100 ℃ for 20 h), cold-rolling (reduction ratio of 60%), and subsequent annealing (900 ℃ for 3 min). In N1 alloy (CoCrFeMnNi HEA with 1 at% of nitrogen doping), we could observe fully recrystallized grains with a small amount of Cr2N precipitates. As the nitrogen contents increased to 3 at% (N3 alloy), the recrystallization was significantly retarded by the formation of 3 different types of Cr2N precipitates, leading to having ~60% of non-recrystallized grains. Furthermore, the various precipitates let the alloy have a heterogeneous complex microstructure. With increasing nitrogen contents, the yield strength and ultimate tensile strength can be improved without significant reduction of ductility, which exceeds those of Cantor HEA by nearly a factor of two. The effect of each strengthening mechanism on the improved strength in heterogeneous complex microstructure is systematically discussed. These results are expected to provide a novel guideline on how to effectively control key properties of HEAs by interstitial alloying through tailoring of heterogeneous microstructure as well as the inherent complexity of HEAs.
查看更多>>摘要：The effects of Bi modification and ultrasonic treatment (UST) on the microstructure and mechanical properties of AlMg5Si2Mn alloy were investigated. Compared to the alloy without any treatment, the eutectic Mg2Si phases are refined effectively by Bi addition, and its morphology is changed from the mazelike thick lamellars for the base alloy to thin coralline fibers for the containing Bi alloy. The modification of eutectic Mg2Si phase is attributed to the Bi segregation and composition supercooling in front of the growing Mg2Si phase. UST can assist modification of Bi on the eutectic Mg2Si phase and change the morphology of the primary α-Al phase in the AlMg5Si2Mn alloy from coarse dendrites to small near-spherical equiaxed crystals, meanwhile, which can also promote the homogenization of the treated melt and uniform distribution of Bi atoms or clusters in the melt. Moreover, the yield strength, ultimate tensile strength and elongation of the alloy modified by 0.3% Bi addition combined with UST at 660 °C are obviously enhanced, and the fracture modes of the alloys are changed from brittleness to toughness.
NSTL
Elsevier