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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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    Effects of cryogenic thermal cycling on a La-based metallic glass: Relaxation or rejuvenation?

    Ma Z.Huang P.Wang F.
    7页
    查看更多>>摘要：? 2022 Elsevier B.V.Despite tremendous efforts conducted to reveal the role of cryogenic thermal cycling (CTC) treatment played in the microstructural evolution of metallic glasses (MGs), the underlying mechanisms corresponding to rejuvenation (or relaxation) are still poorly understood. By altering the cycling number and temperature, in the present study, the effects of CTC on hardness and β relaxation behaviors of La60Ni15Al25 MG were evaluated. Intriguingly, the experimental results indicated the cycling number dependence on hardness and the activation energy of β relaxation Eβ following identical trends, and all samples exhibited rejuvenation first and then turned to relaxation after certain cycling numbers. Moreover, it is indicated that the MG with distinct microstructural states could exhibit identical hardness and Eβ, and this unique observation was proposed to be dominated by the mechanism correlated to the shear transformation zone (STZ) size and matrix-path between the percolated STZs.
      原文链接:
    • NSTL
    • Elsevier

    Achieving equiaxed microstructure and isotropic mechanical properties of additively manufactured AZ31 magnesium alloy via ultrasonic frequency pulsed arc

    Cao Q.Qi B.Zeng C.He B....
    7页
    查看更多>>摘要：? 2022 Elsevier B.V.The high cooling rate and thermal gradient in the wire arc additive manufacturing (WAAM) process often leads to a tendency towards columnar grains or columnar dendrites in magnesium alloys, which can result in anisotropic mechanical properties and are therefore undesirable. To address this challenge, a novel ultrasonic frequency pulsed (UFP) arc used as heat source is applied to alter the conditions in the WAAM process and promote equiaxed growth of magnesium grains. Experimental results indicate that the AZ31 magnesium alloy deposit produced by the UFP-WAAM exhibits full equiaxed-grain microstructure along the building direction. Without any additional treatments, the AZ31 magnesium alloy deposit displays promising mechanical properties, such as isotropic tensile strength and excellent ductility.
      原文链接:
    • NSTL
    • Elsevier

    Realization of volatile and non-volatile resistive switching with N-TiO2 nanorod arrays based memristive devices through compositional control

    Yu Y.Wang C.Wen Y.Jiang C....
    10页
    查看更多>>摘要：? 2022It is attractive to manipulate the volatile and non-volatile resistive switching behaviors of memristors to create genuine neuromorphic systems such as artificial neural networks (ANNs) and spiking neural networks (SNNs). To investigate the above behaviors, nitrogen has been introduced into TiO2 nanorod arrays (TiO2 NRAs) by hydrothermal processing. X-ray photoelectron spectroscopy (XPS) analysis shows that both lattice and interstitial nitrogen are incorporated into the TiO2 NRAs. Nitrogen doped TiO2 NRAs (N-TiO2 NRAs) based memristive devices with different contents of lattice nitrogen were investigated systematically. The results show that non-volatile restive switching is achieved at up to a relative lattice nitrogen content of 21%, with volatile switching behavior above this value. The volatile memristive devices show similar spiking and decay features to the Leaky Integrate-and-Fire (LIF) model. The lifetime of the decay process of the volatile devices rang from 0.029 to 1.835 s. The longest lifetime is obtained when the relative content of lattice nitrogen is about 70%. The volatile behavior is related to the large defect concentration, caused by nitrogen doping. The proposed nitrogen engineered memristive devices could pave the way to achieving a physical neuromorphic system.
      原文链接:
    • NSTL
    • Elsevier

    Reaction mechanism of Ca-reduction diffusion process used for sustainable recycling Nd-Fe-B sludge

    Xu H.Lu Q.Li Y.Liu W....
    8页
    查看更多>>摘要：? 2022 Elsevier B.V.The reduction diffusion (RD) process for Nd-Fe-B sludge has been reported as a green and efficient method for synthesizing recycled Nd2Fe14B magnetic powders. In this work, recycled Nd-Fe-B powders with low impurity content and uniform particle size distribution were successfully prepared. M3 T increased to 146.25 emu/g, which was about 17% and 32% higher than the purged and original sludge, respectively. Then, the recycled Nd-Fe-B sintered magnets with properties of Br = 12.14 kG, Hcj = 12.00 kOe, and (BH)m = 35.05 MGOe were successfully prepared by doping with 37.70 wt% Nd4Fe14B powders. Based on experimental studies of calcium thermal reduction of Nd-Fe-B sludge and thermo-kinetic analysis, the reaction mechanism of the RD method for sludge waste recovery was clarified. In the RD process, the oxides in the sludge were selectively reduced by Ca at 600–950 °C and the reduced Nd diffused to the surface of the Fe core, forming the Nd-Fe-B alloy, where the formation process included the nucleation stage, the alloy layer high-speed growth stage, and the completion stage. And the relationship between the alloy layer thickness and time during the high-speed growth period of 1–3 h was more in line with linear law (d = 5.41 t–4.31). The RD reaction conformed to the unreacted shrinking core model, and its reaction rate control step consisted of a one-way diffusion process for the diffusion of Nd into the Fe core.
      原文链接:
    • NSTL
    • Elsevier

    Magnetic properties and structural anomalies observed in multiferroic NdFe3(BO3)4 by 57Fe Mossbauer spectroscopy

    Frolov K.V.Lyubutin I.S.Alekseeva O.A.Smirnova E.S....
    6页
    查看更多>>摘要：? 2022 Elsevier B.V.The results of studies of the NdFe3(BO3)4 by 57Fe Mossbauer spectroscopy in comparison with the data of single crystal X-ray diffraction measurements are presented. Scanning of the crystal cell parameters in a wide temperature range T = 15–500 K revealed a negative thermal expansion along the c axis and structural anomalies. The temperature dependences of the M?ssbauer parameters of hyperfine interaction in the paramagnetic state of NdFe3(BO3)4 correlate well with the behavior of crystal cell parameters obtained by X-ray diffraction data. The temperature of the magnetic phase transition TN = 32.54(4) K is established, below which the iron ions form a 3D magnetic order of the Izing type. The magnetic transition of the iron subsystem from a commensurate to an incommensurate structure at a temperature of about T ≈ 15 K is discussed. The “M?ssbauer” Debye temperature ΘM was estimated to be 485(2) K.
      原文链接:
    • NSTL
    • Elsevier

    Effects of solid isolation medium on the microstructure and magnetic properties of one-step sintered L10-FePtCu nanoparticles

    Dong S.Ju Y.Jiang Y.Meng C....
    6页
    查看更多>>摘要：? 2022 Elsevier B.V.To explore a more efficient process parameter for controlling the microstructure and magnetic properties of liquid-phase assisted one-step sintering method, the effects of isolation medium size and uniformity on L10-FePtCu NPs have been studied. The grain size (d) of L10-FePtCu NPs has been refined by decreasing the average size of solid isolation mediums (D), and the relationship can be approximated as d= 6.60 × D1/3 ? 9.14. The disorder-order transition of the L10 phase has been inhibited by decreasing the medium size, however, it has been facilitated by increasing the medium size uniformity. The ordering degree, coercive force, and magnetic energy product of L10-FePtCu NPs reach the highest when using the middle sized and best uniformity NaCl mediums (about 8 μm). This research indicates that controlling the interface between the solid isolation mediums and the precursors is an effective strategy to tune the microstructure and magnetic properties of one-step sintered highly ordered L10 phase NPs.
      原文链接:
    • NSTL
    • Elsevier

    Structural-phase composition of iron-containing high carbon composites with fullerite and graphite obtained by mechanosynthesis

    Larionova N.S.Nikonova R.M.Ul'yanov A.L.Lad'yanov V.I....
    11页
    查看更多>>摘要：? 2022 Elsevier B.V.In the present paper, X-ray diffraction, scanning electron microscopy, Mossbauer, Raman and X-ray photoelectron spectroscopy and thermal analysis have been used for the comparative studies of composites fullerite-Fe and graphite-Fe containing 75 at% of carbon and obtained by the mechanosynthesis method. The synthesized materials are nanoscale powders. Depending on the time of mechanosynthesis and a used form of carbon, the phase composition of the composites is significantly different. It is shown that compared with graphite, fullerite is characterized by higher stability in the composition of iron-containing mechanocomposites. The sequence of the fullerite structural changes during mechanosynthesis is as follows: fullerite → amorphous fullerite-like phase → amorphous carbon. When fullerenes are retained, carbides are not formed in the system fullerite-Fe. After the formation of amorphous carbon, the compared composites fullerite-Fe and graphite-Fe have the same composition (Fe3C, Fe7C3, paramagnetic P-phase and amorphous carbon). The stability of the mechanically synthesized phases at heating has been studied.
      原文链接:
    • NSTL
    • Elsevier

    In-situ observation of peritectic solidification of Fe-Mn-Al-C steel with medium manganese

    Wang W.An Z.Luo S.Zhu M....
    12页
    查看更多>>摘要：? 2022 Elsevier B.V.The design of the continuous casting process for the third generation of Fe-Mn-Al-C steel with medium manganese should be based on the understanding of the peritectic solidification mechanism. So, in the present study, Fe-5.56Mn-0.078Al-0.157C (wt%) steel was taken as the research object. By means of high-temperature confocal scanning laser microscopy (HT-CSLM), Thermo-Calc thermodynamic software and optical microscopy, the peritectic solidification process and microstructure characteristics of the medium manganese steel at different cooling rates were studied and revealed. And thus, the influence of the cooling rate on the peritectic solidification mechanism was clarified. Meanwhile, the kinetics of the γ-Fe grain wrapping the δ-Fe grain and the subsequent growth were determined. The results show that at low cooling rate of 10 °C/min, the initial δ-Fe phase is cellular. The γ-Fe phase firstly nucleates at the L/δ interface, and then grows along the δ/L interface until the L and δ-Fe phases are separated. Subsequently, the peritectic transformation occurs, that is the L and δ-Fe phases are directly transformed into the γ-Fe phase. Under the conditions with higher cooling rates of 20 and 30 °C/min, when the γ-Fe phase separates the L and δ-Fe phases completely, multiple γ-Fe grains form in a single δ-Fe grain at the same time, and the whole δ-Fe grain is covered within a very short time, which is the typical massive-like transformation. In the initial stage of the peritectic reaction, the linear velocity of the γ-Fe phase wrapping the δ-Fe phase is inversely proportional to the cooling rate, which is closely related to the size and morphology of δ-Fe grains. At cooling rates of 10, 20 and 30 °C/min, the initial migration rates of the δ/γ interface are 45.9, 8.9 and 12.5 μm/s, respectively. At higher cooling rates, the occurrence of the massive-like transformation greatly promotes the peritectic transformation, and the migration rate of the δ/γ interface increases to 16.7 and 17.8 μm/s. The initial migration rates of the γ/L interface are 6.0, 1.8 and 6.5 μm/s, respectively. It is found that the migration rate of the δ/γ interface is much larger than that of the γ/L interface. Dendrite etching experiment in the top, bottom and longitudinal sections of the medium manganese steel samples shows that the larger the cooling rate, the finer the solidification structure.
      原文链接:
    • NSTL
    • Elsevier

    Constructing oxygen vacancies and linker defects in MIL-125 @TiO2 for efficient photocatalytic nitrogen fixation

    Wang L.Wang S.Li M.Yang X....
    11页
    查看更多>>摘要：? 2022 Elsevier B.V.With the emergence of issues such as global warming and glaciers melting, reducing carbon emissions cannot be ignored. Ammonia can participate in the N element cycle in nature and has a huge market demand. In modern industry, the preparation of ammonia mainly relies on the Haber-Bosch process with huge energy consumption. Using clean photocatalytic method to prepare ammonia can alleviate the above problems. Here, the core-shell structure of MIL-125 @TiO2 was prepared by post solvothermal method for photocatalytic nitrogen fixation. Linker defects can appear as active sites in the residual MIL-125, which forms an obvious mesoporous structure that accelerates the exchange of electron/mass and promotes the activation of N2. The shell structure constructed by thin TiO2 nanosheets possesses a large specific surface area. And the oxygen vacancies active sites could be highly exposed for nitrogen adsorption and activation, so as to promote the occurrence of the photocatalytic reaction. The O?Ti?N covalent bond is established between the titanium-oxygen clusters in the peripheral of TiO2 and the linker in MIL-125, which improves the effective separation of electron-hole pairs. The ammonia formation rate of MIL-125 @TiO2-2 h is 102.7 μmol g?1 h?1 under simulated sunlight, which is 8 times higher than that of MIL-125. This work provides a novel idea for the preparation of photocatalytic nitrogen fixation materials with controllable structure and multiple active sites.
      原文链接:
    • NSTL
    • Elsevier

    Ultrasensitive V doped WO3 1D nanorods heterojunction photodetector with pronounced photosensing activities

    Ikram M.Rasheed S.Hussain D.Afzal A.M....
    10页
    查看更多>>摘要：? 2022 Elsevier B.V.In this study, vanadium-doped tungsten oxide (V-WO3) nanorods heterostructures are designed by a simple, facile, and eco-friendly hydrothermal method and applied for photo-sensing activities. Physical characterization results indicate the phase purity, crystalline nature, tuneable energy bandgap, higher surface area, and successful formation of V doped WO3 nanorods. Optoelectronic properties reveal pronounced photo-sensing capabilities of the designed material demonstrating efficient charge transfer. The photocurrent density is enhanced with laser power. Large values of open-circuit voltage (Voc) and short-circuit current (Isc) in the range of 0.91 V and 28 mA/cm2, respectively, are obtained at 56 mW/cm2 power. The Isc is enhanced considerably as a function of power intensity of laser due to the formation of large number of photo-induced electron-hole pairs and large value of built-in potential. Furthermore, to estimate the response time of the device, the measured temporal photoresponse is 4500 A/W, several-fold higher than previously reported materials, associated with suppression in the dark current. In addition, the detectivity of V doped WO3 NRs photodetector lies in the range of 5.15×1011 Jones and the calculated value of detectivity and EQE is ~70%. These results are interesting and provide a roadmap to design ultrasensitive photodetectors.
      原文链接:
    • NSTL
    • Elsevier