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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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    Hot deformation behaviors of AZ91 magnesium alloy: Constitutive equation, ANN-based prediction, processing map and microstructure evolution

    Misra R.D.K.Wang D.Zhu Q.Wei Z....
    17页
    查看更多>>摘要:? 2022 Elsevier B.V.The hot deformation behavior in an AZ91 magnesium alloy was studied using Arrhenius model and Back-Propagation Artificial Neural Network (BP-ANN) approaches. The hot compression tests of AZ91 alloy were performed on the MMS-300 simulator at deformation temperatures and strain rates in the range of 473–623 K and 0.001 s?1- 1 s?1, respectively. The results indicated that the BP-ANN model has higher accuracy than Arrhenius model and the correlation coefficient is as high as 0.99341. The processing map is divided into three parts: machinable area (A), instability area I (INS I) (B) and instability area II (INS II) (C). The instability mode of areas B and C gradually changes from cracks to holes with the increase of temperature or the decrease of strain rate. The stable hot-deformation conditions with peak efficiency of power dissipation were concentrated in the range of 523 K, 0.01 s?1, 573 K, 0.01 s?1, 623 K, 0.001–1 s?1, respectively. With the increase of temperature, the deformation mechanism changed from twinning to dynamic recrystallization (DRX), which is discontinuous dynamic recrystallization (DDRX). Due to DRX,< 0001 > // CD texture intensity increased with the increase of temperature, and then decreased.

    Significantly improved hydrogen storage properties of Mg90Al10 catalyzed by TiF3

    Yang L.Li S.Chen J.Liu J....
    8页
    查看更多>>摘要:? 2022 Elsevier B.V.Magnesium hydride (MgH2) is one of the most promising materials for solid state hydrogen storage, but overly stable thermodynamics and sluggish kinetics of hydrogenation and dehydrogenation hinders its application. In this study, Mg90Al10 was prepared by hydriding combustion synthesis (HCS), and then various Ti-based compounds (Ti, TiH2, TiO2 and TiF3) were introduced into Mg90Al10 by ball milling. Mg90Al10 + 10 wt% TiF3 displays the most excellent dehydrogenation property compared with those doped with other Ti-based compounds. For instance, due to the addition of 10 wt% TiF3, the peak dehydrogenation temperature and the apparent dehydrogenation activation energy of the composite are 86 °C and 77.1 kJ/mol lower than those of Mg90Al10 (364 °C and 155.95 kJ/mol). In addition, the catalytic effect of TiF3 on the hydrogen storage properties of Mg90Al10 has been investigated in detail. Except for the unreacted TiF3, Al3Ti and MgF2 can be found during the first dehydrogenation process and remain stable in the subsequent de/hydrogenation cycles, which can act as the active sites to accelerate the hydrogen dissociation and recombination. Therefore, the excellent hydrogen storage properties of Mg90Al10 + 10 wt% TiF3 can be attributed to the catalytic effect of TiF3, in-situ formed Al3Ti and MgF2. Our result is very significant to emphasize the practical application of the Mg-Al hydrogen storage alloys.

    Broadband near-infrared emitting Sr3Sc4O9: Cr3+ phosphors: Luminescence properties and application in light-emitting diodes

    Lin J.Zhou L.Ren L.Shen Y....
    10页
    查看更多>>摘要:? 2022 Elsevier B.V.Near-infrared (NIR) phosphors converted to light-emitting diodes (pc-LED) sources have extensive application prospects in medical imaging, foodstuff analysis and plant growth fields. However, there are some shortcomings in NIR phosphors, such as narrow emission band and poor thermal stability. Here a new wide band NIR luminescent phosphor Cr3+-doped Sr3Sc4O9 (SSO) is introduced. The emission spectrum ranges from 600 nm to 1000 nm, with a peak value of 761 nm and the value of full width at half maximum (FWHM) is 120 nm. The internal quantum efficiency (IQE) of sample is about 87% according to the fitting result. The most appropriate doping concentration is x = 0.02 and the best excitation wavelength is 468 nm, which matches the commercial blue chip. At the same time, the phosphor shows good thermal stability in variable temperature spectrum test, and can maintain 70.4% emission intensity at 373 K relative to room temperature. To better understand its practical applications, packaged pc-LED is designed to show good NIR light penetration in spectral penetration tests. This study provides an excellent choice of NIR phosphors.

    Enhanced magnetocaloric effect from Zn substitution in perovskite Eu(Ti,Zn)O3 compounds

    Xie H.Shen J.Zhang L.Mo Z....
    7页
    查看更多>>摘要:? 2022 Elsevier B.V.The magnetic transition from antiferromagnetism to ferromagnetism (AFM-FM) in EuTiO3 provides the feasibility of regulating its magnetic properties. Foreign element substitution has been proved to be an effective way to achieve AFM-FM switching and enhanced magnetocaloric effect (MCE) in EuTiO3 system. In this study, a series of Zn substituted Eu(Ti,Zn)O3 perovskites were synthesized, the crystal structure, magnetic properties, and MCE were investigated. All the compounds crystallize in a pure cubic perovskite phase with the space group Pm3m, and undergo a second-order phase transition at the ordering temperature 6.0 K. The substitution of Zn can significantly regulate the magnetic properties and enhance the ferromagnetic coupling, thus leading to an enhanced MCE in the Eu(Ti,Zn)O3 compounds. Under field change of 0–1, 0–2, and 0–5 T, the ?ΔSMmax values are 10.3, 21.4, and 38.5 J·kg?1·K?1 for EuTi0.9375Zn0.0625O3, 10.8, 22.7, and 41.1 J·kg?1·K?1 for EuTi0.875Zn0.125O3, 12.5, 25.3, and 45.0 J·kg?1·K?1 for EuTi0.8125Zn0.1875O3, respectively. Besides, the compounds exhibit prominent refrigeration capability and temperature averaged entropy change. The considerable magnetocaloric performances make the Eu(Ti,Zn)O3 perovskites potential candidate materials for cryogenic magnetic refrigeration.

    Solar light-responsive α-Fe2O3/CdS/g-C3N4 ternary photocatalyst for photocatalytic hydrogen production and photodegradation of methylene blue

    Yavuz C.Erten-Ela S.
    17页
    查看更多>>摘要:? 2022 Elsevier B.V.Photocatalytic degradation of waste materials in aqueous solutions, as well as photocatalytic hydrogen generation, were investigated for remediation of environment and renewable energy production. α-Fe2O3 and CdS are attractive visible-light-driven semiconductor photocatalysts because of their inexpensive cost, simple production methods, and stability. Whereas, its implementations were limited by the photocorrosion, narrow optical band gap for solar-light operations and poor separation of photogenerated electron-hole pair. To increase the performance of α-Fe2O3, CdS, α-Fe2O3/CdS, and g-C3N4; a ternary nanocomposite (α-Fe2O3/CdS/g-C3N4) was designed. To obtain binary structure, CdS nanoparticles were overgrown on α-Fe2O3 nanorods-cubes using a simple wet-chemical process, and as-prepared g-C3N4 was decorated with binary composite. XRD, SEM, XPS, BET, UV–Visible spectrometry, FT-IR, PL and EIS were employed to investigate the crystal structures, surface morphology, optical properties, functional groups and electrochemical characteristics. Considering the optical absorption properties, the photocatalytic studies were performed for hydrogen production and MB dye degradation under solar light irradiation. Among the synthesized semiconductors, the ternary material had the highest photocatalytic hydrogen evolution, 165 μmol g?12 h?1 from water. Within 120 min, the photocatalytic performance resulted in 99.4% degradation of the MB. The higher activities were attributed to Z-scheme mechanism, optical band levels and strict heterojunctions of the photocatalysts that induces an influential electron-hole separation, subsequently rapid diffusion of photogenerated charge between components and also the optical bandgap value of the ternary structure that more convenient for solar lights applications. This work paves a way for improvement of photocatalysts working in practical conditions of pollution and energy issues.

    Super-paramagnetic polymer composite-supported dendrimer–Mn catalyst: Fabrication, characterization and catalytic evaluation in selective aerobic oxidation of ethylbenzene and oximes derivatives

    Movahedian S.Farahani A.R.Faraji A.R.
    17页
    查看更多>>摘要:? 2022 Elsevier B.V.Design of strategy and catalytic for oxidation ethylbenzene, toxic petroleum, to high value-added via hydrogen-atom-transfer process is lately attracting a renewed interest from both environmentally and economic view. Herein, novel manganese-based dendritic catalysts supported on the polymer-magnetic core-shell were synthesized, fully identified and evaluated with initiator NDHPI for selective and easy-to-handle aerobic oxidation of ethylbenzene (EB) and oximes to acetophenone (ACP) & carbonyl compounds (AH/KO), respectively. Besides mild condition reaction, the supported dendrimer-encapsulated Mn NPs also exhibited outstanding catalytic performance, such as selective oxidation of ethylbenzene and oximes using O2 as green and cheaper oxidant with excellent reactivity, selectivity, stability, and magnetic recyclability. Additionally, the effect of operating parameters such as the amount of catalyst, nature of solvent, temperature and reaction time, and role of several N-hydroxyimides were studied in the catalytic efficiency of the synthesized dendritic catalyst. The results illustrated that the enhanced catalytic efficiency of the catalyst is derived from the magnetic dendritic structures, high Mn(II) content, hydrophobic arm of dendrimers, and interaction of Mn and the dendritic framework. Finally, the reaction pathway for EB and oxime has been deduced, and the crucial role of dendritic catalyst, NDPHI, and electronic effect has been elucidated.

    Construction of a novel N-doped oxygen vacancy-rich TiO2 N-TiO2?X/g-C3N4 S-scheme heterostructure for visible light driven photocatalytic degradation of 2,4-dinitrophenylhydrazine

    Dong S.Chen S.He F.Li J....
    11页
    查看更多>>摘要:? 2022 Elsevier B.V.For improving the photocatalytic activity, a new N-TiO2?X/g-C3N4 (NTCN) composite was designed and constructed successfully by a facile hydrothermal-calcination method. The co-doping N and Ti3+/Ov were achieved to reduce the band gap of TiO2, and g-C3N4 nanosheets were coated firmly on the surface of N-TiO2?X to form efficient heterojunctions. The photocatalytic activity of N-TiO2?X/g-C3N4 was evaluated fully under visible light irradiation to achieve the degradation of 2,4-dinitrophenylhydrazine (2,4-DNPH). When the content of g-C3N4 in composite is 30 wt% (NTCN0.3) with calcination temperature of 350 ℃, the photocatalytic degradation rate of 2,4-DNPH can reach 93.19% after 70 min irradiation, which is much higher than those of monomers and other composites. Furthermore, the degradation process was verified to be pseudo-first-order kinetic model, and the apparent activation energy is 17.23 ± 2.47 kJ mol?1. S-scheme heterojunction mechanism was speculated to explain the extremely high photocatalytic degradation ability of NTCN0.3 composite.

    Relaxor ferroelectric nature and magnetoelectric coupling of the one dimensional frustrated Ca3CoMnO6

    Gong G.Zhou J.Duan Y.Hu H....
    5页
    查看更多>>摘要:? 2022 Elsevier B.V.The typical ↑↑↓↓ spin order of the one-dimensional frustrated Ca3CoMnO6 breaks the inversion symmetry and results in the ferroelectricity. But the previous calculations predict a much larger ferroelectric polarization than the experimental observation. To comprehend the divergence, Ca3CoMnO6 ceramics were prepared and the magnetic, dielectric properties were studied. In accordance with the formation of short range magnetic correlation, around the antiferromagnetic transition temperature TN the Ca3CoMnO6 ceramics present weak relaxor ferroelectric nature. It implies the existence of polar nanoregions. Thus, the destruction of long range ferroelectric order and the formed polar nanoregions should be responsible for the suppressed macroscopic ferroelectric polarization. The activation energy and static freezing temperature of Ca3CoMnO6 are also calculated. The obtained values are Ea = 6.31 × 10?3 eV and Tf = 1.5 K, respectively. Both of them are lower about two orders of magnitude than the conventional relaxor ferroelectrics. Magnetic field dependent dielectric permittivity manifests the large magnetodielectric coupling of Ca3CoMnO6. Under the application of field of 7 T, the dielectric permittivity reduces by about 10%.

    Oxygen vacancy defect tungsten-oxide-quantum-dot-modified nitrogen-doped graphene with interfacial tiny primitives to boost oxygen reduction reaction

    Chen K.Rajendiran R.Li O.L.Wang W....
    11页
    查看更多>>摘要:? 2022 Elsevier B.V.Ultrafine quantum-dot-modified nitrogen-doped graphene has attracted board interest and has become frontier research in metal-air batteries and fuel cells. In this study, oxygen vacancy defect tungsten oxide quantum dots (Vo-WO3 QDs) are embedded in nitrogen-doped graphene (NG) to form abundant heterogeneous interfacial electrocatalysts (Vo-WO3 QDs/NG), which exhibits advanced electrocatalytic activity for oxygen reduction reaction (ORR) in an alkaline electrolyte. The optimized Vo-WO3 QDs/NG-5 (W content of 0.14 wt%) exhibits high onset potential (0.932 V vs. RHE) and decent half-wave potential (0.762 V vs. RHE) with high stability, which outperforms other reported tungsten metal oxide-based ORR electrocatalysts. The outstanding electrocatalytic performances of Vo-WO3 QDs/NG-5 are contributed by higher amount of oxygen vacancy and defects in Vo-WO3 QDs, as well as tunable interfacial electronic properties between the Vo-WO3 QDs and NG support. Furthermore, the density functional theory (DFT) is systematically conducted to determine the electronic properties and interface charge transmission for Vo-WO3 QDs/NG entity, providing important insight on the electrocatalysts in terms of band regulation and electron transport at the active interface between Vo-WO3 QDs and NG. Our finding paves an efficient pathway to design highly active hetero-structural and durable electrocatalysts for ORR applications based on defect-rich metal oxide QDs supported on nitrogen-doped graphene.

    Investigating the s and dielectric properties of CoFe2?xNixO4 spinel ferrite

    Lone G.A.Ikram M.
    8页
    查看更多>>摘要:? 2022 Elsevier B.V.The present work reports the structural and dielectric properties of pristine and Ni-doped spinel CoFe2O4. To investigate the influence of doping on the structural and dielectric properties of the samples, the samples were synthesized using a solid-state reaction approach. A single-phase FCC cubic spinel structure with space group Fd3ˉm was confirmed for all the prepared materials with the help of Rietveld refinement. The cationic distribution indicates a decrease in the occupancy of Fe2+ and the corresponding increase of that of Ni2+. The microstructural analysis and the elemental composition analysis was carried out using SEM and energy dispersive spectroscopy (EDS) respectively. For all samples the temperature-dependent dielectric characteristics were investigated, revealing the presence of orientational and interfacial polarization. The dielectric constant is temperature independent until it reaches around 270 K, after which it begins to increase with increasing temperature. And this temperature starts decreasing for higher doping concentrations. Also, CoFe1.9Ni0.9O4. was seen to have strong relaxation behavior and low dielectric loss. The low dielectric loss of CoFe1.9Ni0.9O4 makes it useful at higher frequencies in electrical circuits that faces the challenges of high-temperature rise.