查看更多>>摘要：Double manganite PrBaMn2O6 with ordered alternate stacking of PrMnO3/BaMnO3 layers attracts a special interest due to presence of two magnetic phase transitions close to room temperature; that makes it perspective magnetocaloric and magnetoresistive material. Besides the magnetic phase transition, the structural transition accompanied with the elongation of the a-axis and the contraction of the c-axis was experimentally detected. The origin of structural phase transition is studied by X-ray powder diffraction, X-ray photoelectron spectroscopy (XPS), IR absorption spectroscopy, magnetometry and dynamical mean-field theory (DMFT) for electronic structure calculations. It is found that the structural phase transition is caused by splitting of eg-doublet states due to the tendency towards orbital ordering at the metal-insulator phase transition.
查看更多>>摘要：Cu1.8S (digenite), a copper sulfide with natural Cu deficiencies, possesses excellent conductivity, low-cost, as well as environmentally friendly features. It has thus recently attracted heightened attention. However, the thermoelectric performance of pristine Cu1.8S is poor, and the related mechanical properties have not been deeply investigated, which hinders this material from becoming a candidate for commercial applications. This work proposes an effective approach to synergistically improve the comprehensive performance of polycrystalline Cu1.8S-based bulk materials for use in practical applications. Cu1.8S-xRu (x = 0.005, 0.01, 0.02) bulk composites were successfully fabricated by combining mechanical alloying and spark plasma sintering technology. Benefiting from the overall optimized power factor and thermal conductivity by the regulated carrier concentration and enhanced phonon scattering effect from the incorporation of multiscale lattice defects, a peak figure of merit of 1.0 at 773 K was achieved in the Cu1.8S-1% Ru bulk specimen. In addition, the introduction of ruthenium could enhance the thermal stability of Cu1.8S materials by suppress the Cu ions motion. A conversion efficiency of 1.0% at a temperature difference of 480 K was obtained for the single-leg TE module. Finally, the excellent average Vickers hardness of 1.22 GPa for the Cu1.8S-1%Ru bulk composite was higher than that of other state-of-art TE materials. Compositing with ruthenium might be an approach worth promoting to synergistically improve the thermoelectric and mechanical performance of other materials.
查看更多>>摘要：Post-deposition heat treatments of chemically deposited SnS-orthorhombic thin films at 450 °C in a controlled ambient greatly influence their structural, morphological, compositional, optical and electrical properties. Heating of the film with a tin chloride layer (90 nm in thickness) produced by thermal evaporation led to an increased crystalline grain diameter (23 nm) in the film, with characteristics suitable for solar cell application: a bandgap (Eg) of 1.2 eV (indirect), p-type electrical conductivity of 10–3 Ω–1 cm–1, hole concentration of 1015 cm–3 and hole mobility of 2.4 cm2/(V s). However, heating the SnS film in a controlled S-vapour ambient converted it to Sn2S3 with a crystalline grain diameter of 24 nm, Eg of 1.2 eV (direct), n-type electrical conductivity of 3.4 × 10–3 Ω–1 cm–1, and an electron concentration of 1016 cm–3. Optical absorption spectra of these materials suggest a photo-generated current density (JL) of 32 mA/cm2 under air mass 1.5 Global (1000 W/m2) solar radiation for either material for a thickness of 600 nm, which is attractive for solar cells.
查看更多>>摘要：Silicon-based materials are considered the most promising anode materials for lithium-ion batteries (LIBs). However, due to the huge volume effect of Si powder during charging and discharging, the pulverization and peeling of silicon nanoparticles results in a certain amount of active material loss, which significantly affects the stability and coulombic efficiency of the battery. In this paper, a simple suspension mixing-freeze drying process was used to prepare a Si@Ti3C2Tx composite with a fluffy and porous structure, in which Si nanoparticles (SiNPs) are wrapped in a 3D conductive network of wrinkled and curled Ti3C2Tx nanosheets. Thus, both Si nanoparticle agglomeration and restacking of Ti3C2Tx nanosheets are inhibited, electrolyte penetration and charge transfer are facilitated, and Si nanoparticle volume expansion is effectively buffered. When used as an LIB anode, after 500 cycles and at a density of 1 A g?1, a high specific capacity of 1729 mAh g?1 and coulombic efficiency of ≥ 98.5% were achieved for Si@Ti3C2Tx, showing excellent electrochemical performance.
查看更多>>摘要：Quasi-static and dynamic compressive tests with a series loading rates were conducted on (Zr0.6336Cu0.1452Ni0.1012Al0.12)97Tm3 bulk amorphous alloy at cryogenic temperature. It is found that mechanical properties of the alloy such as yield strength and plasticity are obviously dependent on temperature and strain rate. The plastic strain of the specimens at 298 K and 77 K is 8.4% and 13.7% respectively under quasi-static load with strain rate of 1 × 10?4 s?1. Additionally, the dynamic mechanical properties of amorphous alloys at different strain rates were tested by split Hopkinson pressure bar(SHPB) to unveil the dynamic deformation behaviors at cryogenic temperature of 177 K and 77 K. Compared with the results of quasi-static compression, strain rate softening phenomenon can be observed under dynamic loading, but the compressive strength of specimens increases significantly with the decrease of temperature. Moreover, the specimens have no obvious plastic deformation under dynamic loading. Compared with room temperature, the improvement of quasi-static and dynamic compressive strength of the alloy at cryogenic temperature can be attributed to the strong interatomic binding force between the alloy elements.
查看更多>>摘要：High entropy alloys (HEAs) have exhibited excellent irradiation resistance regarding structure stability. However, limited knowledge has been available on the tendency of mechanical properties of HEAs with body-centered cubic structures after ion irradiation. In this study, the evolution of mechanical properties of the HfNbZrTi irradiated with 3 MeV C ions is studied based on micropillar compression tests. The yield strength increases almost linearly from 974 to 2068 MPa with increasing irradiation doses up to 0.98 dpa. The correlation between the mechanical and microstructural changes agrees well with the prediction of [Formula presented], indicating a similar strengthening mechanism with conventional alloys. Nonetheless, the irradiation strengthening effect in this alloy is less pronounced in the low dose regime, and the saturation is postponed, compared with the stainless steel and the 3d metal high entropy alloys with face-centered cubic structures, exhibiting promising irradiation resistance regarding mechanical properties.
查看更多>>摘要：The particle pollution caused by the stray light of the high-energy laser system irradiating the frame aluminum alloy is one of the most important reasons that hinder the stable operation of the system. Therefore, accurately revealing the mechanism of the interaction between the stray light and the aluminum alloy frame is an important and challenging task to ensure that inertial confinement fusion (ICF) system can generate clean and sustainable energy. In this paper, based on the secondary development of ABAQUS, a transient-stabilized thermal-mechanical direct coupling model is developed and experimentally investigated for the laser-material interaction in the high-energy nanosecond laser system with an energy density of 2 J/cm2. The mechanical damage, thermal ablation, and especially the temperature dependence of the thermal optical parameters of the aluminum alloy are considered in the modeling. Through comparative analysis, the results indicate that the effect of the variable optical properties must be considered in order to accurately reveal the mechanism of intense laser irradiation. On this basis, we found that the pulsed intense laser is absorbed by the aluminum alloy with a smaller absorption rate, after the aluminum alloy surface reaches the melting point and liquefies. This means more laser is reflected to the laser system, reducing the stability and reliability of the system. The whole process includes thermal expansion, thermal melting and potential mechanical damage, while no vaporization ablation occurs. The simulation conclusions are verified by the characterization of the experimental specimens, and it is verified that the diameter of the melting area is close to the full width at half maximum (FWHM) of the Gaussian laser source. This study provides a more accurate numerical model for precisely revealing the mechanism of high-energy nanosecond laser irradiation on metallic materials, and thus promoting the sustainable and reliable generation of clean energy from inertial confinement fusion.
查看更多>>摘要：The application of the high-entropy concept has generated many interesting results for both alloys and ceramics. However, there are very few reports on high entropy thermoelectric materials. In this work, a single phase high-entropy half-Heusler compound MFe1-xCoxSb with 6 equimolar elements (Ti, Zr, Hf, V, Nb and Ta) on the M site was successfully synthesized by a simple method of mechanical alloying, and the single phase was maintained after densification by spark plasma sintering. The multi-elements are homogenously distributed in the samples. The samples are stable and there is no phase separation after annealing at 1073 K in argon for 72 h, which could be attributed to their high configurational entropy. Due to the phonon scattering introduced by multi-elements, the lattice thermal conductivity is largely suppressed with a lowest value of ~ 1.8–1.5 Wm?1K?1 (300–923 K) for MCoSb. By adjusting the Fe/Co ratio, the samples can show both n-type and p-type semiconductor behavior. Maximum zT values of 0.3 and 0.25 are achieved for n-type MCoSb and p-type MFe0.6Co0.4Sb, respectively. The results suggest that the high-entropy concept is a promising strategy to extend the composition range and tune the thermoelectric properties for half-Heusler materials, which could potentially be applied in other thermoelectric materials.
查看更多>>摘要：Magnesium hydride (MgH2) with high gravimetric hydrogen storage capacity is considered as one of the most potential hydrogen storage materials; however, its development has been plagued by the high operating temperature and slow kinetics. In this study, we have design and synthesize a core-shell Ni/Fe3O4@MIL additive to aid the (de)hydrogenation of MgH2/Mg system via the co-catalytic effect of in-situ formed Mg2NiH4/Mg2Ni and Fe. The initial dehydrogenation temperature significantly reduces from 613 K to 517 K, and the MgH2-Ni/Fe3O4@MIL composite can reabsorb 4.17 wt% H2 within 3600 s under 3.0 MPa H2 at 373 K. Remarkably, the dehydrogenation activation energy of the composite decreases by 61.77 kJ/mol compared to the pure MgH2 (159.71 kJ/mol). Moreover, the composite also shows good cycling stability without distinct capacity decay after cycling twenty times. Studies show that during dehydrogenation and hydrogenation processes, the Mg2NiH4/Mg2Ni act as catalysts to induce hydrogen desorption/absorption of MgH2/Mg. Meanwhile, the unique core-shell structure of the Ni/Fe3O4@MIL not only provides reaction sites, but also prevents the agglomeration of nanoparticles and maintains stable catalytic activity. This study provides a new idea for designing stable transition metal heterogeneous catalytic system to improve hydrogen storage performance of MgH2.
查看更多>>摘要：Due to outstanding optical characteristics of phosphors, they have recently been applied to various fields, such as solid-state lighting, forensic science, and laser technology. Herein, a series of Mg2InSbO6:xEu3+ (x = 0.005–0.25) phosphors with pure red emission were prepared via high-temperature solid-state reaction. Under near-ultraviolet 395 nm excitation, photoluminescence spectra of Mg2InSbO6:Eu3+ (MISO:Eu3+) phosphors exhibited a bright red luminescence peak at 612 nm, which is attributed to 5D0→7F2 transition of Eu3+. The thermal quenching temperature of the optimum sample exceeded 480 K, which is much higher than the working temperature of light-emitting diode (423 K). The packaged white light-emitting diode (WLED) had CIE coordinates of (0.336, 0.340) with correlated color temperature of 5322 K and color rendering index value of 90. Furthermore, the latent fingerprints (LFPs) stained with MISO:Eu3+ phosphors were visualized with level 1–3 features, but their accuracy was relatively low. Therefore, oleic acid (OA) was utilized to form a hydrophobic coating on MISO:Eu3+ powders to improve fingerprint development, and the higher accuracy of level 1–3 features was achieved, especially level 3 features. The LFPs on smooth and rough surfaces stained with MISO:Eu3+@OA phosphors were easily collected at high contrast under 395 nm light. The obtained results prove that MISO:Eu3+ and MISO:Eu3+@OA can be considered as promising red phosphors for WLED and LFP identification and provide insight into the improvement of LFP development.
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Elsevier