查看更多>>摘要：Present proposed mechanisms for ageing-induced martensitic stabilization cannot explain why the amount of martensites losing reverse transformation ability (RTA) positively depended on Ms temperatures in directly-quenched CuZnAl alloys owing to dynamic ageing during the cooling process of quenching and subsequent slow heating. We proposed and confirmed that the number of vacancies at martensites boundaries (N-vmb) was the key factor controlling the occurrence of martensitic stabilization and its resulting RTA or loss in shape memory effect, not the number of vacancies inside the martensites and their long-range diffusion. All reported results can be rationalized by the positive dependence of original N-vmb on the Ms temperature. (C) 2022 Published by Elsevier B.V.
Shaterian, MaryamYulchikhani, MassoudAghasadeghi, ZahraArdeshiri, Hadi Hassani...
8页
查看更多>>摘要：Hydrogen is considered as one of the most renewable and also efficient fuels. When hydrogen is burned, its only product is water. But the most important issue in the use of hydrogen is its storage. Hydrogen must be stored reversibly in a way that is completely safe and has high storage efficiency. Due to obtaining high-efficiency hydrogen storage, new nanostructures based on barium hexaferrite nanostructures (BaFe12O19) and functionalized multi-walled carbon nanotubes BaFe(12)O(19 )nanocomposite (BaFe12O19/MWCNTs) are synthesized via sol-gel combustion method. The nanocomposites are confirmed through Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET), and vibrating sample magnetometer (VSM) techniques. Further, the hydrogen storage capacity of BaFe12O19/MWCNTs nanocomposite is assessed by chronopotentiometry analysis (CHP). The XRD studies demonstrates that the average crystallite sizes of the BaFe12O19 and nanocomposite are estimated to be about 16.3 and 7.6 nm, respectively. Also, the VSM measurement shows a saturation magnetization values (Ms) of 20.1 and 1.3 emu/g for BaFe12O19 and BaFe12O19/MWCNTs nanocomposite, respectively. The electrochemical consequences indicate that the BaFe12O19/MWCNTs nanocomposite has a high capacity for hydrogen storage and discharge rate. The maximum discharge capacity of BaFe12O19/ MWCNTs nanocomposite reaches about 360 mAh/g in the first cycle to approximately 3600 mAh/g after 20 cycles under an optimal current of 2 mA. As a result, the BaFe12O19/MWCNTs nanocomposite showed a good capacity as a promising active ingredient for hydrogen storage devices.(C) 2022 Published by Elsevier B.V.
查看更多>>摘要：Refractory high entropy alloy TiZrHfNbTa matrix composites reinforced with in-situ nitrides were prepared by vacuum arc melting. The designed composites are composed of BCC matrix and FCC nitride phases, with a particular orientation relationship between them: [111](BCC)parallel to[011](MN),(10 (1) over bar)(BCC)parallel to(200)(MN),(1 (1) over bar0)(BCC)parallel to(1 (1) over bar1)(MN). The composites show enhanced strengths both at room temperature and high temperature compared with the matrix alloy and increase with the increment of N content. The ambient and elevated temperature (1000 degrees C) compressive yield strength is up to 2125 MPa and 350 MPa, respectively, and decent fracture strains (> 19.3%) at room temperature are maintained. The underlying strengthening mechanisms are discussed systematically, and the increase in strength is mainly attributed to the combination of dislocation strengthening, load-transfer effect and Orowan strengthening. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Superior electromagnetic (EM) wave absorption properties in 8.2-12.4 GHz (X-band) can be obtained via the effective combination of polyaniline (PANI) and SnO2 nanoparticle cluster. In this work, SnO2 nanoparticle cluster@PANI (SnO2@PANI) core-shell microspheres were firstly fabricated via a hydrothermal process followed by in-situ polymerization, and the EM wave absorption properties of SnO2@PANI coreshell microspheres in X band were studied. The related structure and morphology analyses indicated SnO2@ PANI core-shell microspheres were successfully synthesized with PANI coated on the surface of SnO2 nanoparticle cluster. The minimum reflection loss (RLmin) of - 69.1 dB (thickness of 2.78 mm) and effective absorption bandwidth (EAB) covering the whole X-band (when the thickness was from 2.5 to 3.1 mm) was achieved. Remarkable EM wave absorption properties of SnO2@PANI core-shell microspheres were mainly attributed to the outstanding impedance matching characteristic and dielectric loss capability (conduction loss, interfacial polarization loss and dipole polarization loss).
查看更多>>摘要：In this work, the structural evolution and photoluminescence (PL) of 200 nm pseudomorphic Ge0.9338Sn0.06 62 on Ge (001) substrate grown by low-temperature molecular beam epitaxy (MBE) after rapid thermal annealing (RTA) is studied. Under RTA at 350 degrees C or lower, the GeSn film is coherently strained on Ge substrate. As RTA temperature further increases, gradual strain relaxation of GeSn is enabled by generation of misfit dislocations and threading dislocations. As RTA temperature reaches 550 degrees C or beyond, Sn segregation occurs along with strain relaxation. The PL intensity of annealed samples is enhanced compared to that of as-grown sample probably due to improved crystal quality and strain relaxation (for RTA at > 350 degrees C) of GeSn. The sample annealed at 500 degrees C exhibits highest PL intensity due to formation of a Sn-componentgraded (SCG) heterojunction with highest Sn content in surface region resulted from interdiffusion of Ge and Sn. The formation of SCG heterojunction renders spontaneous confinement of optically pumped carriers in the surface region and enlarges occupation probability of carriers in Gamma valley. Additionally, the carrier confinement in the surface region reduces self-absorption of GeSn and suppresses nonradiative recombination near the GeSn/Ge interface. The results manifest that RTA is an appropriate approach to improve the light emitting property of GeSn grown by low-temperature MBE. (c) 2022 Elsevier B.V.
查看更多>>摘要：The plate-like Fe-rich intermetallics phases in the recycled Al-Si alloys significantly deteriorate the mechanical properties. In this study, the effect of Mn addition on Fe-rich phases formation and the properties of the Al-7Si-1.2Fe alloys were systematically studied by optical microscopy, scanning electron microscopy, differential scanning calorimetry, thermodynamic calculations, synchrotron X-ray radiography and tomography. The results show that with the addition of Mn, the two-dimensional (2D) morphology of the Fe-rich phase change from plate-like to Chinese-script and star-like. The synchrotron X-ray tomography results indicate that the three-dimensional (3D) morphology of Fe-rich phases change from interconnected platelike to separated hollow polyhedron with increasing Mn content. The in-situ synchrotron X-ray radiography results reveal that the formation temperature, size, and area fraction of the primary Fe-rich phase in the Al7Si-1.2Fe-1.09Mn alloy gradually decreased, but the number density increased as the cooling rate increased. The thermodynamic calculation results indicate that beta-Al5FeSi could be eliminated when the Mn content exceeded 1.06%, which was consistent with the experimental results. However, excessive Mn addition caused the formation of large primary Fe-rich phases, resulting in a significant reduction in the elongation of the alloys. Reducing the equilibrium partition coefficient difference of Mn and Fe and reducing the formation of primary Fe-rich phases with high Mn/Fe ratios are good strategies to neutralize the negative effect of Fe-rich phases. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：CoP3 is a promising electrocatalyst for the hydrogen evolution reaction, however it is still challenging for CoP3-based catalyst to deliver excellent activities in a wide pH range. In this work, the self-standing Ni-doped CoP3 nanowire arrays (Ni-CoP3 NWs) on carbon fiber paper were synthesized by hydrothermal method followed with an in situ phosphating process. The results show that the Ni doping effectively boosts the electrocatalytic hydrogen evolution for CoP3 NWs over the wide pH range with good stability. The Ni doped CoP3 NWs sample with the Ni: Co mole ratio of 10% (Ni-CoP3-10%) shows a low overpotential of 66 mV to afford the current density of 10 mA cm(-2) in 0.5 M H2SO4, which is the optimal catalytic performance in this work. Furthermore, Ni-CoP3-10% sample also shows excellent electrocatalytic performance in alkaline and neutral conditions, which needs the overpotential of 114 and 131 mV to afford the current density of 10 mA cm(-2) in 1 M KOH and 1 M PBS, respectively. The enhanced electrocatalytic activity can be ascribed to that the Ni doping improves the electron transport, increases the electrochemical active surface area and optimizes the Gibbs free energy of hydrogen adsorption for the CoP3 NWs, which develops it as a promising electrochemical catalyst for hydrogen evolution. (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：The electrical conductivity and catalytic activity of the electrode materials greatly affect the photoelectric conversion performance of DSSCs. However, the commonly used Pt electrodes no longer meet the needs of long-term development at present. Herein, based on the Kirkendall effect, CoFe2O4 @C nanoparticles with core-shell structure are successfully prepared using the treatment of quasi-sol-gel method. The size of CoFe2O4 @C nanoparticles is homogenized without agglomeration through adjusting the ratio of metal salt in the precursor. The composite exhibits excellent counter electrode properties in DSSCs, which attributes to the large specific surface area and superior electro-catalytic activity. With the optimized film thickness (12 mu m) of CoFe2O4 @C, an excellent photoelectric conversion efficiency of 7.80% is finally achieved, significantly higher than that of pure carbon (PC) electrode (6.36%) and even Pt counter electrode (7.05%) under the same conditions. The composite can additionally catalyze the recycling of I-/I3- redox couple steadily, providing more possibilities for the study of Pt-free materials about DSSCs counter electrode. (c) 2022 Published by Elsevier B.V.
查看更多>>摘要：Antimony doped tin(IV) oxide (ATO) based materials are promising alternatives used in electrochemistry for water purification. However, their practical application remains a major bottleneck due to the drawback of poor stability. Therefore, we design a simple and viable strategy for preparing a series of TiO2 @ATO@MOx (TAM, M = Mn, Fe, Co, Ni, Cu, and Zn) electrodes. The oxygen evolution potential, electrode stability, and electrochemical activity toward methylene blue (MB) were studied and compared. When evaluated as electrode material toward methylene blue (MB) oxidation, TiO2 @ATO@NiO (TANi) exerts an excellent degradation efficiency and service lifetime; these are the highest values among these TAM electrodes. Cyclic voltammetry (CV) measurements demonstrated that NiO can effectively enhance roughness factor and voltammetric charge, indicating a large electrochemically active surface area and abundant electroactive sites. The addition of NiO effectively lowers the charge transfer resistance and enhances the electrode stability. Moreover, theoretical calculations based on the first-principle density functional theory (DFT) indicate that the conductive property of TAM is manipulated by MOx adding and thus an excellent electrochemical activity is achieved. Based on the experimental data and computational simulations, our work brings new important insights that will contribute to the development of high-performance and stable ATO-based electrode materials. (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：A new titanium matrix composites (TMCs) with distinctive architecture consisting of isolated fiber-like structural composites region (FLSCR) within continuously Ti region were designed and fabricated by powder metallurgy, hot extrusion, and subsequent hot rolling. This work systematically investigated the important role of TiB contents on microstructural evolution and mechanical response of the as-rolled fiberlike structural TMCs. The designed FLSCR-5% and FLSCR-10% with fiber-like structure obtain high ductility of 24.4% and 19%, respectively, which shows a better combination of strength and ductility. The strengthening is attributed to the refinement of the equiaxed alpha grains and the load-bearing effect of TiB whiskers. Meanwhile, continuously Ti region significantly reflects and blunts the crack propagation which is supposed to improve the static toughness of the fiber-like structural TMCs, but the ductility would be decreased by increasing TiB content in the FLSCR, which is attributed to the decreasing volume fraction of titanium matrix and the increasing crack initiation rate. Additionally, due to the fiber-like composites region, the strain hardening rate of the FLSCR-10% (from ~0.05 to ~0.135 strain) is significantly strengthened by the hetero-deformation induced back stress, which is beneficial to the ductility. (c) 2022 Elsevier B.V. All rights reserved.
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