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Journal of Alloys and Compounds
Elsevier Science S.A.
Journal of Alloys and Compounds

Elsevier Science S.A.

0925-8388

Journal of Alloys and Compounds/Journal Journal of Alloys and CompoundsSCIISTPEI
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    Honeycomb-like Ni-Mo-S on Ni foam as superior bifunctional electrocatalyst for hydrogen evolution and urea oxidation

    Wang F.Zhang K.Zha Q.Ni Y....
    10页
    查看更多>>摘要:It is still a challenge to prepare highly-efficient electrocatalysts through a facile and controllable technology for hydrogen production. Herein, a simple electrochemical deposition method was designed for the preparation of honeycomb-like nickel-molybdenum-sulfur amorphous microstructures on the nickel foam (labeled as NiMoS/NF), which exhibited excellent electrocatalytic activity for hydrogen evolution reaction (HER) and urea oxidation reaction (UOR). The as-deposited NiMoS/NF electrode merely required overpotential of 37 mV to reach the current density of 10 mA cm?2 for HER in 1.0 M KOH solution, and presented ultralong durability above 310 h at 10 mA cm?2. In a mixed solution of 1.0 M KOH and 0.5 M urea, simultaneously, 1.015 V of overpotential was needed to generate the current density of 100 mA cm?2 for UOR. In a two-electrode cell with the electrolyte of 1.0 M KOH and 0.5 M urea, a voltage of 1.377 V was demanded to deliver the current density of 10 mA cm?2. The present work shows that the electrodeposition technology is a simple and feasible approach to construct robust and highly-active electrocatalysts for H2 production.

    Anchoring of red perovskite nanocrystals on YAG:Ce phosphor for high color rendering index WLEDs

    Tang Y.He X.Zhang Y.Yuan H....
    8页
    查看更多>>摘要:Widespread application of YAG:Ce-based white light-emitting diodes (WLEDs) is being challenged for their poor color rendering index (CRI) and high correlated color temperature (CCT) due to the lack of red emission. Organic-inorganic hybrid perovskite nanocrystals (MAPbX3 PNCs, X = Cl, Br, I or mixture of them), presenting high photoluminescence quantum yield, tunable emission color and simple fabrication process have been recognized as promising red-emitting component for warm WLEDs. However, additional protection process for PNCs always needed due to their poor stability, which complicates the fabrication procedures of WLEDs. Besides, nano-sized PNCs and micron YAG:Ce powder display different sinking behavior in silicone, which also hard to ensure the uniform distribution of the two components and subsequently stable optical characteristics of the device. Herein, a one-pot anchoring strategy is implemented to realize the enhanced thermal and photo-stabilities of in-situ generated red-emitting MAPbBr0.5I2.5 PNCs and simultaneously strong interaction between the PNCs and YAG:Ce to form PNCs@A-YAG composite, which greatly simplifies the processes, and also avoids the uneven distribution of phosphor and PNCs in silicone. Furthermore, the WLED, fabricated by PNCs@A-YAG and a commercial blue chip, exhibits high CRI of 92, low CCT of 4755 K, and super high saturated red color R9 of 95, which are of vital importance in achieving warm white light for indoor lighting applications. This work could promote the practical application of perovskite nanocrystals in the field of high color rendering index WLEDs.

    Solution–processed Cu2O/ZnO/TiO2/Pt nanowire photocathode for efficient photoelectrochemical water splitting

    Chen Y.-C.Yeh H.-Y.Hsu Y.-K.Popescu R....
    11页
    查看更多>>摘要:State–of–the–art Cu2O photocathodes are mostly fabricated by means of electrodeposition and have been reported to be flooded with the copper vacancies (VCu), into which the photoexcited electrons are rapidly trapped and thereby hardly injected into the electrolyte for photoelectrochemical water splitting. To address this issue, an alternative approach consisting of simple wet chemistry combined with post–thermal treatment is employed in the present contribution to grow the Cu2O nanowires (NWs) on the Cu foil, which provides the Cu ions to fill VCu. An important result of the depletion of VCu is the space charge layer extending deep into the Cu2O NWs, wherein the photoexcited charge carriers are rectified by the surface band bending for efficient separation. The charge separation is further reinforced by using ZnO to first extract the photogenerated electrons from Cu2O, TiO2 to further glean the electrons from ZnO, and the Pt co–catalyst to facilitate their injection into the electrolyte. These materials are deposited sequentially on the Cu2O NWs by means of chemical bath deposition, which is put forward in the present contribution as a cost–effective and readily scalable alternative to the conventional atomic layer deposition technique. The synergistic effect leads to a photocurrent density of the Cu2O/ZnO/TiO2/Pt NWs of ?8.2 mA cm?2, well outperforming that of the pristine Cu2O NWs by more than 2.5–fold and, moreover, being comparable to that of the electrodeposited counterparts reported in the literature.

    The annealing induced formation of epsilon martensite in CoCrNi medium-entropy alloy after severe plastic deformation

    Deng H.W.Du W.Y.Liu Z.Y.Zhang T....
    5页
    查看更多>>摘要:This study reports the formation of the ε-martensite phase induced by post-deformation annealing (PDA) after severe plastic deformation in the equiatomic CoCrNi medium-entropy alloy. This ε-martensite phase was identified by analyzing the microstructure and the magnetic properties. It was found that after three passes of equal-channel angular pressing (ECAP), annealing at 500 °C or 600 °C induces a clear ε-martensite phase without recrystallization, while upon increasing the annealing temperature to above the recrystallization temperature, i.e., 700 °C or 800 °C, the ε-martensite phase gradually disappears. In addition, the hardness and creep behavior during PDA were investigated via nanoindentation. A different creep behavior before and after recrystallization was observed. The possible formation mechanism of this martensitic transformation is discussed.

    Structure and magnetic properties of Ga doped Nd13.65Fe74.15B5.6Co6.6 ribbons

    Gu F.Wang S.Zhang C.Yu X....
    8页
    查看更多>>摘要:The addition of low melting point Ga changed the crystallization process and microstructure of the Nd13.65Fe74.15B5.6Co6.6 ribbons. The Ga addition improves the glass-forming ability of the ribbons, and the ribbons melt-spun at 25 m/s are composed of Nd2(Fe, M)14B phases with different Nd contents and Nd-rich amorphous grain-boundary phase. Nd2(Fe, M)14B grains have a gradient size of 50–300 nm, also, the large-sized grains are slightly rich in Fe-Co, and the small-sized ones are rich in Nd. Compared to the Ga-free alloy, 0.6 at% Ga addition narrows the grain boundary width to 5.5 ± 4.5 nm, promotes the enrichment of Ga atoms at grain boundaries and form Nd(Fe, Co)1.62Ga0.04 composition, improved the intergranular exchange coupling and magnetic properties of the ribbons most significantly, increasing the coercivity and remanence by 52.6% and 36.6% respectively. Besides, the microstructure models changed by Ga addition are established, and the corresponding solidification processes and magnetic mechanisms are discussed.

    Revealing the crystallization kinetics and phase transitions in Mg65Zn30Ca5 metallic glass by nanocalorimetry

    Zhang L.Xiao H.Li S.Zhao B....
    11页
    查看更多>>摘要:As a potential candidate for biomedical applications, Mg65Zn30Ca5 (at%) metallic glass has attracted considerable attention. To guide the development of MgZnCa alloys with improved mechanical and biomedical properties, it is necessary to understand the phase transitions of this metallic glass. In this study, controlling phase transitions in Mg65Zn30Ca5 metallic glass is realized by nanocalorimetry. The underlying thermodynamic and kinetic features at heating rates ranging from 102 to 105 K s?1 are therefore revealed. Upon rapid heating, an intermediate amorphous phase is detected. This metastable phase facilitates the formation of the Mg7Zn3 crystalline phase with a remarkably reduced reaction temperature and activation energy. With the combination of nanocalorimetry and structural characterization, the continuous heating transformation (CHT) diagram for Mg65Zn30Ca5 metallic glass is plotted, and crystallization trajectories under various heating conditions are distinguished. Meanwhile, the crystallization kinetics covering seven orders of magnitude is estimated, giving the growth rate of the MgZn crystalline phase in the undercooled liquid with temperatures ranging from Tg to Tm. Accordingly, the maximum crystal growth rate and corresponding temperature are estimated at umax= 0.49 m s?1 and Tu,max= 563 K, respectively. With the decrease in undercooling, the transition from kinetics-controlled crystallization to thermodynamics-controlled crystallization is illustrated, causing divergence of the estimated growth rate from the experimental results.

    Facile fabrication of MXene supported nickel-cobalt selenide ternary composite via one-step hydrothermal for high-performance asymmetric supercapacitors

    Liu Y.Gong J.Wang J.Hu C....
    8页
    查看更多>>摘要:Bimetallic transition metal selenides have high theoretical capacitance for energy storage, which are considered as a hopeful supercapacitor electrode material. Herein, a MXene-induced strategy was used to synthesize NiCo2Se4/MXene composite via a one-step hydrothermal process. The conductive MXene sheets could boost the electrochemical activity of NiCo2Se4 nanoparticles while provide additional capacitance. The charge storage performance is improved by the synergy between the NiCo2Se4 and MXene, as a result, the NiCo2Se4/MXene composite electrode achieved a better performance capacitance of 953.8 F g?1 at 1 A g?1, which is higher than the NiCo2Se4 electrode. An asymmetric supercapacitor (ASC) device has been made up of NiCo2Se4/MXene and acetylene carbon, exhibits outstanding energy storage capacity and cycle stability. These electrochemical results indicate the NiCo2Se4/MXene composite could be a promising electrode material for practical energy reserve applications.

    Large anomalous Hall effect in kagomé ferrimagnetic HoMn6Sn6 single crystal

    Chen C.Fang C.Ma S.Zhong Z....
    6页
    查看更多>>摘要:The anomalous Hall effect (AHE) in ferromagnetic materials has attracted tremendous interests for their physical properties and great application in spintronics devices. Here, we report a large AHE in kagomé ferrimagnetic HoMn6Sn6 single crystal. The large intrinsic contribution of the anomalous Hall conductivity σxy,intA was about 120 Ω?1cm?1, which was a considerable value compared to that in other materials with kagomé lattice. The anomalous Hall conductivity is significantly not affected by temperature, manifesting that large AHE is basically dominated by the intrinsic mechanism in connection with the Berry curvature. These results suggest that the HoMn6Sn6 alloy with Mn-based kagomé nets provides an excellent platform to comprehend the relationship between the magnetic structures and topological properties.

    Analysis of the effect of copper concentration on the structural, spectroscopic, and electrical properties of Cu:ZnO thin films

    V S G.K.M G M.
    11页
    查看更多>>摘要:A detailed report on the investigation of structural, spectroscopic, and electrical properties of copper doped zinc oxide (CZO) thin films on the glass substrate is presented here. The spray pyrolysis technique was employed to prepare optimized ZnO thin films and copper (Cu) was added as the dopant with different concentrations. Structural properties of all samples were studied by analyzing the x-ray diffractogram (XRD) that showed a crystallite size around 40 nm. Zinc oxide (ZnO) films deposited at various Cu concentrations possess hexagonal crystal structure with (002) preferential orientation. At high copper concentrations, impurity peaks corresponding to copper were observed. Scanning electron micrographs (SEM) revealed good connectivity between the grains, along with the dense and uniform texturing on the surface. Absorbance spectra showed a red shift in absorption edge. A second band gap was observed at higher copper concentrations corresponding to the copper oxide (CuO) phase. Raman analysis with spatial imaging, x-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) studies were carried out for all the samples, that showed the presence of copper secondary phase at high copper concentration. CZO films showed higher resistivity than pristine ZnO. However, resistivity decreased at a higher Cu level. Photosensitivity measurements showed a sensitivity of about 32.64 for 5 at% Cu doped ZnO films under white light. Photosensitivity of the material is attributed to the copper-related defect levels.

    Enhancing thermoelectric performance of K-doped polycrystalline SnSe through band engineering tuning and hydrogen reduction

    Xin N.Li Y.Tang G.Shen L....
    14页
    查看更多>>摘要:High-efficient and environment-friendly thermoelectric materials have attracted much attention. The single crystal tin selenide (SnSe) has a record high thermoelectric figure of merit (ZT) of 2.6 at ~800 K. Polycrystalline SnSe has better mechanical-strength but inferior ZT values than the single crystal, attribute to the paradoxically higher thermal conductivity (κ). In this work, we synthesized KxSn1?xSe (x = 0, 0.01, 0.02, 0.03 and 0.04) by doping K2CO3. A large number of point defects and dislocations generated with CO2 volatilization, which possibly reduces κ. Based on this process, the KxSn1?xSe powders were followed by the hydrogen reduction with 4% H2 ? 96% Ar atmosphere to reduce tin oxide and potassium oxide which have high κ. These strategies lead to an ultra-low κ 0.32 Wm?1K?1 in K0.03Sn0.97Se at 798 K. The effects of K doping on electronic transport performance of SnSe were studied by density functional theory calculation and experimental measurement. Doing K can narrow the band gap, increase hole concentration and enhance the electrical conductivity (σ) of SnSe. At 298 K, the σ of KxSn1?xSe increased by more than 2.5 times compared with the pristine SnSe. In high temperature region (623 K< T < 823 K), the σ is mainly affected by thermal excitation. High doping level of K (x = 0.03 and 0.04) suppresses the thermal excitation and limits the maximum of ZT. As the result, A high ZT of 1.06 is obtained at 798 K from K0.01Sn0.99Se perpendicular to the pressing direction, which is 103.8% larger than that of pristine SnSe. In addition, the hot-pressing polycrystalline KxSn1?xSe remains obvious lamellar morphology and show anisotropy. The σ and κ of KxSn1?xSe samples perpendicular to the pressure direction are much higher than those of the samples parallel to the pressure direction. This anisotropy decreases with the increasing K content.