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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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    Comment on “Comprehensive physical studies on nanostructured Zn-doped CdSe thin films [Journal of Alloys and Compounds 789 (2019) 108–118]; Structure, optical and transport properties of Mg-doped ZnMn2O4 [Journal of Alloys and Compounds 655 (2016) 188–197]”

    Aly K.A.
    2页
    查看更多>>摘要:? 2022 Elsevier B.V.In the literature a widely spread equation to correlate between the optical (σoptic) and electrical (σelec) conductivities in the form of ([Formula presented]). Unfortunately, the tow sides of this equation have different dimensions i.e this equation is incorrect and the work by this equation must be stopped. The calculation of electrical/optical conductivity should be limited to the correct forms only deduced from the correct solution of Maxwell's equations.

    Enhanced adsorption on TiO2 photoelectrodes of dye-sensitized solar cells by electrochemical methods dye

    Teng H.Venkatesan S.Lee Y.-L.Chen Y.-Y....
    10页
    查看更多>>摘要:? 2022 Elsevier B.V.Dye-adsorption is an important step in the fabrication of dye-sensitized solar cells (DSSCs). The classical dye-adsorption method is performed by spontaneous process and, to obtain the optimal cell efficiencies, about 16–24 h are required, which is considered uneconomical for the mass production of DSSCs. To solve this problem, here, a quick dye adsorption process based on electrochemical methods including cyclic voltammetry, constant potential, and constant current techniques are the first time utilized to prepare photoelectrodes for DSSC applications. To obtain the optimal cell efficiencies, the experimental conditions are regulated. Among these methods, the electrodes prepared using the constant potential methods (3 V and 4 V for 60 and 30 min, respectively) have high performance in DSSCs under room light and one-sun conditions. This method significantly reduces the time for dye adsorption from 16 to 24 h to 30 min or ~ 1 h. The cells using these electrodes have high incident photon to current efficiencies, high recombination resistances, high electron lifetimes, and low dark current densities. Owing to these characteristics, the DSSCs achieve efficiencies as high as 8.27% and 14.49%, respectively, under one-sun and room light conditions. These efficiencies are identical to that of the efficiencies obtain for the cells prepared using the classical adsorption process.

    Enhancement of the mechanical properties of ultrafine-grained WC-Co cemented carbides via the in-situ generation of VC

    Wang K.-F.Yang X.-H.Deng X.-C.Chou K.-C....
    11页
    查看更多>>摘要:? 2022 Elsevier B.V.WC-12Co-xVC cemented carbides were synthesized using an in-situ synthesis method consisting of precursor formation, deoxidization and carbonization-sintering steps. The experimental results showed the mean grain size of the WC in the sintered alloys decreased from 1.05 to 0.46 and 2.13–0.57 μm, corresponding to the VC content from 0 to 2 wt% at 1350 °C and 0–6 wt% at 1400 °C. V4WC5 thin-layer was generated in the final sintered sample with low VC addition. As the VC content increased to more than 2 wt%, the V4WC5 with larger particles size were generated except the V4WC5 thin-layer, which would effectively enhance the hardness of WC-12Co-VC cemented carbides. The fracture toughness reached the maximum value of 16.45 MPa·m1/2 for WC-12Co-2VC sintered at 1350 °C for 2 h; while the Vickers hardness reached the maximum value of 2124 HV for WC-12Co-6VC sintered at 1400 °C for 2 h, respectively.

    Enhancing the electrochemical performance of Li4Ti5O12 anode materials by codoping with Na and Br

    Zhang L.Zhang J.Xu B.
    10页
    查看更多>>摘要:? 2022 Elsevier B.V.Li4Ti5O12 (LTO) anode materials have become a research hotspot due to their “zero strain” characteristics. However, LTO has shortcomings such as a low capacity and rate performance, which severely restrict its development. In this work, Na+- and Br-- codoped LTO was successfully prepared by the sol-gel method, which effectively improved the capacity and high-rate performance. According to morphology and structure characterization, codoping retains the spinel crystal lattice and results in a more uniform phase and smaller particle size. Na+ doped at Li sites expands the lithium layer spacing, promoting the migration of Li+. Br- doped at O positions forms stronger covalent bonds with Ti, improving structural stability. Long-cycle and rate performance tests show that NB3-LTO exhibits the best electrochemical performance. The discharge capacity of NB3-LTO is 490.2 mAh g?1 at 0.2 C and 243.0 mAh g?1 at 10 C, while the corresponding values for pure LTO are only 158.5 and 66.4 mAh g?1. Codoping increased the discharge capacity 3.1- and 3.7- times respect to pure LTO at 0.2 and 10 C, respectively. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests show that the Li+ diffusion coefficient increases and the electrochemical impedance decreases. All test results show that codoping with Na+ and Br- is a feasible method to produce LTO anode materials with outstanding comprehensive performance.

    A review of hot deformation behavior and constitutive models to predict flow stress of high-entropy alloys

    Savaedi Z.Mirzadeh H.Motallebi R.
    21页
    查看更多>>摘要:? 2022 Elsevier B.V.This review article summarizes the hot deformation behavior of high entropy alloys (HEAs) and the corresponding constitutive description of flow stress. The potential of hot working for grain refinement via dynamic recrystallization (DRX), reduction of casting defects, and enhancement of mechanical properties of HEAs is explained. The necklace formation, work hardening analysis for identification of the occurrence and initiation of DRX, and the effects of processing parameters on dynamically recrystallized grain size are discussed. The effects of deformation conditions (represented by the Zener-Hollomon parameter), alloying elements, dynamic precipitation, and the presence of phases on the hot deformation behavior and restoration processes of DRX and dynamic recovery (DRV) are overviewed. The application of processing maps for the characterization of the onset of flow instability, cracking, flow softening, and DRX during hot forming of HEAs is presented. Regarding the constitutive modeling of flow stress for characterization of material flow (at different deformation temperatures, strain rates, and strain), the utilization of the threshold stress (due to the presence of phases or their precipitation during high-temperature deformation), and temperature-dependent Young's modulus, as well as correlating the obtained values of deformation activation energy and stress exponent with the expected ones from the creep theories are taken into account. Afterward, the available methods and equations for modeling and prediction of flow curves during thermomechanical processing are assessed, where the strain-compensated Arrhenius model, artificial neural network (ANN) model, Zerilli-Armstrong model, Johnson-Cook model, Hensel-Spittel model, and dislocation density-based multiscale constitutive model are presented. Finally, some suggestions for future research works are proposed.

    Synthesis and characterization of silicon clathrates of type I Na8Si46 and type II NaxSi136 by thermal decomposition

    Fix T.Chevalier C.Rehspringer J.-L.Vollondat R....
    7页
    查看更多>>摘要:? 2022 Elsevier B.V.Type I (Na8Si46) or type II (Nax≤24Si136) silicon clathrates films with a large 15 × 45 mm2 surface have been synthesized from p-type and intrinsic c-Si (001) wafers using a two-step process without the need of any glove box. Conditions to selectively obtain either type I or type II silicon clathrates phase have been finely tuned. Optical absorption coefficients are found much larger in the Si clathrates than in diamond silicon in the visible light range. Type II films provide a direct bandgap of around 1.9 eV which is supporting the high absorption coefficient observed. Photovoltaic response of the films has been confirmed using Surface Photovoltage. As prepared type II films show many surface defects, cracks and inhomogeneities which have been drastically reduced thanks to a pressure annealing treatment.

    Effect of stress-relief annealing on rolled texture of nickel-based alloys

    Ji Y.Suo H.Liu J.Ma L....
    15页
    查看更多>>摘要:? 2022 Elsevier B.V.In this study, the effects of stress-relief annealing (SRA) on the rolled texture of nickel-based alloys were extensively analysed. Biaxially textured Ni–W alloy substrates with strong cube textures were fabricated by cold rolling and recrystallisation annealing for coated conductor applications. The results indicate that the evolution of the rolled texture, and hence the annealed cube texture, were greatly influenced by the stress-induced by deformation. The stress and rolled texture were found to be significantly correlated. X-ray diffraction and electron backscattered diffraction analyses were used to explore the effect of SRA on the cold-rolled microstructure. The stress distribution was found to be associated with the copper texture. The addition of SRA effectively eliminated stress and strengthened the copper and S textures, thereby facilitating the formation of the final annealed cube texture. Finally, the mechanism by which stress influences the rolled texture of nickel-based alloys was elaborated in detail.

    Design and synthesis of magnetic porous carbon nanofibers with excellent microwave absorption

    Shen Y.Zhang F.Song P.Zhang Y....
    11页
    查看更多>>摘要:? 2022The magnetic porous carbon nanofibers (CNFs) are highly desirable due to the excellent reflection loss (RL) and impedance matching in microwave absorption applications. Herein, the porous Ni/NiO/CNFs were fabricated by electrospinning combined with vacuum calcination and etching technology. Porous Ni/NiO/CNFs with different electromagnetic (EM) parameters and impedance matching could be easily obtained by adjusting the calcination temperature. On account of the synergistic loss mechanism composed of magnetic loss and dielectric loss leads to excellent impedance matching, the porous structure caused multiple reflection and scattering of incident electromagnetic waves (EMW), combined with the polarization loss between different components, the as-prepared materials exhibited enhanced EMW absorbing property compared with traditional microwave absorbers (MAs). The resulting porous Ni/NiO/CNFs obtained at 650 °C exhibited the optimal EMW absorption performance with an RL of ?47.9 dB at 9.5 GHz and broad effective absorption bandwidth (EAB) of 3.5 GHz with a thickness of 3.0 mm. This work provides a mentality for multi-component loss mechanism and rational structure design of CNFs-based absorbing materials.

    Novel synthesis of sulfur-doped graphitic carbon nitride and NiCo2S4 composites as efficient active materials for supercapacitors

    Ma J.-S.Kubendhiran S.Lin L.-Y.Yang H....
    9页
    查看更多>>摘要:? 2022 Elsevier B.V.Graphitic carbon nitride (g-C3N4) with high nitrogen contents and excellent thermal/chemical stability is widely applied as active material of supercapacitors (SC). Small surface area and electrical conductivity of g-C3N4 lead to poor electrochemical performance, which can be improved by heteroatom doping and metal compound incorporation. In this work, it is the first time to fabricate NiCo2S4/S-doped g-C3N4 (NCS-C) composite using thermal polymerization and hydrothermal reaction as active material of SC. The S-g-C3N4 electrode shows a higher specific capacitance (Csp) of 72.4 mF/g at 20 mV/s than that of 49.5 mF/g of g-C3N4 electrode. Using sulfur as doping source and anion in metal compound favors for improving compatibility of composites. NCS-C composite shows favorable S-g-C3N4 nanosheets-covered NCS flower-like structures. The NCS-C electrode presents a higher Csp value of 351.0 F/g at 1 A/g (886.2 F/g at 20 mV/s) than that of 348.9 F/g at 1 A/g (794.2 F/g at 20 mV/s) of NCS electrode, due to sulfur and nitrogen-rich carbon of S-g-C3N4 and abundant redox reactions of NCS. The symmetric SC with NCS/C electrodes delivers potential window of 1.0 V, maximum energy density of 9.7 Wh/kg at 0.65 kW/kg, and Csp retention of 97.6% and Coulombic efficiency of 90% after 10,000 charge/discharge cycles.

    Nitridated CaSiO3: Eu and SrSiO3: Eu phosphors for LEDs

    Sokolnicki J.
    8页
    查看更多>>摘要:? 2022 Elsevier B.V.Eu2+-activated single-phase CaSi(O,N)3 and SrSi(O,N)3 oxonitridosilicate phosphors were synthesized by a conventional solid-state reaction method at 1100 °C and 1200 °C. For comparative purposes, their oxide equivalents, CaSiO3 and SrSiO3, doped with Eu2+ were obtained using the same synthesis method. The XRD patterns for the obtained phosphors indicate the formation of single-phase oxide and oxynitride phosphors. Energy Dispersive Spectroscopy (EDS) confirmed the incorporation of nitrogen in the phosphor host lattices. The formation of Ca/Sr-N and Si-N bonds can be observed in the FT-IR spectra. The oxonitridosilicate phosphors showed intense emission from Eu2+ in the green-red spectral region. The emissions were redshifted compared to their oxide counterparts described in the scientific literature. The thermal stability and quantum yields (QY) of oxonitridosilicate phosphors were significantly improved compared with respective oxide phosphors. This shows the high potential of oxynitrides as phosphors for light-emitting diodes (LEDs).