查看更多>>摘要：? 2022 Elsevier B.V.The searching for green memristor with good environmental robustness will be significant for next generation biodegradable devices. In this work, bio-compatible and non-toxic polydopamine (PDA) was prepared by self-polymerization of dopamine in simple aqueous solution, which was protonated by different acid concentrations (3–12 M HCl) and further fabricated as memory devices with structures of FTO/PDA/Ag. The ON/OFF ratio are enhanced gradually from 2.80 × 102 (PDA-3 M), 8.39 × 102 (PDA-6 M), 5.18 × 103 (PDA-9 M) to 2.41 × 104 (PDA-12 M). The lower conjugated degree, the closer lattice packing and the less radicals after acid treatment are the reasons for the enhanced bipolar resistive switching performances of protonated PDA-based memristor. The resistive switching mechanism is the conductive filament with three processes of Ohm, space charge limited conduction (SCLC) and trap-filled limited (TFL). In addition, the FTO/PDA-12 M/Ag exhibit good environmental robustness, including thermal (100 °C) and ionizing irradiation (UV exposure for 96 h). In all, the facial protonation treatment and the simple sandwich device structures together with good environmental robustness endow its promising applications in as green, stable and biodegradable next generation electron devices.
查看更多>>摘要：? 2022 Elsevier B.V.Magnetostriction and damping of forced vibrations in Fe-Mo single and polycrystal alloys is studied and analyzed with respect to existing approaches and experimental data. Our data suggest that a more complex dependence (compared with linear dependence predicted by Smith and Birchak) between damping capacity and magnetostriction takes place for this and possibly other Fe-based ferromagnetic alloys. We believe that more factors related to the structural changes, brought about by the additions (elements added to Fe), which can affect phase stability as well as magnetic and electric contributions influencing property response, should be considered to provide a better correlation between the magnetic and magnetomechanical characteristics of this alloy.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, unique Co3S4/Fe3S4 heterostructures (denoted as CoFe-HM-T) were synthesized from CoFe layered double hydroxides (LDHs) by a two-step hydrothermal process (hydrazine monohydrate and thiourea treatment). The effect of Co3S4/Fe3S4 heterostructures on the electrocatalytic water splitting was investigated in alkaline solution. The CoFe-HM-T electrode exhibited excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalytic activity with overpotentials of 320 mV and 200 mV at the current density of 100 mA cm?2, respectively. CoFe-HM-T also possessed the smallest Tafel slope among the prepared samples, which was estimated to be 38.1 mV dec?1 and 144.9 mV dec?1 for OER and HER, respectively. Serving as bifunctional catalysts, the CoFe-HM-T electrode reached the state-of-art current density of 10 mA cm?2 at a cell voltage of 1.70 V with excellent stability. The enhanced electrocatalytic activity was ascribed to the interconnected structure facilitating the mass transport, the heterojunction accelerating the charge transfer, and the synergistic effect between them. This study offered a new strategy for in situ synthesizing the heterojunction electrocatalysts with unique interface by readily tuning the metal components in transition-metal LDHs.
查看更多>>摘要：? 2022 Elsevier B.V.In this paper, the fatigue performance of a ceramic-coated Ti-6Al-4 V alloy was dramatically improved by ultrasonic surface rolling (USR) pretreatment. The effects of coating and residual stress field generated by USR on the fatigue performance, crack path, and failure mechanism of the Ti-6Al-4 V alloy were investigated. Owing to low intrinsic toughness of the TiZrN/TiZr coating, the fatigue crack initiation life of Ti-6Al-4 V alloy was significantly reduced. However, USR with higher processing density significantly improved the fatigue lifetime of the TiZrN/TiZr-coated titanium alloy, which could increase the TiZrN/TiZr-coated titanium alloy fatigue lifetime more than two orders of magnitude at a maximum alternating stress of 550 MPa. This behavior was ascribed mainly to USR with a high processing density hindering the fatigue crack initiation life and growth by inducing a compressive residual stress field with good thermal stability (coating process) and alternating load stability (fatigue progress) on the surface of the titanium alloy. The results promoted the application of ceramic coatings in aerospace to improve the solid-particle erosion resistance and fatigue of aviation equipment.
查看更多>>摘要：? 2022 Elsevier B.V.In this paper, Ti-10at%Al alloy samples were subjected to rolling and high speed compression under different temperatures and along different loading directions (the transverse direction (TD) and normal direction (ND) of the pre-rolled samples), to explore the effects of temperature and loading direction on the deformation mechanisms.101?2 and 112?1 twins were activated in all these deformed specimens. 112?1 twins prevailed in both the room temperature rolled and liquid nitrogen rolled specimens but were severely inhibited during hot rolling, while 101?2 twins did not show obvious change with the temperature. Planar slip of dislocations occurred during room temperature rolling and liquid nitrogen rolling, while cross slip occurred during hot rolling. The change of dislocation behaviors at different temperatures may be caused by the variation in stacking fault energy as an effect of temperature. Moreover, the number of twins in the deformed samples along TD was always higher than that along ND both under rolling and high speed compression. When loaded along TD, most of the grains were with or close to the orientations of<21?1?0> and<101?0>, which were favorable for the activation of 101?2 and 112?1 twins. Therefore twinning played a significant role when loaded along TD, while dislocation slip dominated the deformation when loaded along ND. The hardness increased after deformation under different conditions, and the hardness of specimens after rolling or compression along ND was generally higher than that along TD due to the reason that most of the grains were in the hard< 0001 > orientation when loaded along ND, activation of<c+a> dislocations on pyramidal planes with high critical resolved shear stress was required.
查看更多>>摘要：? 2022 Elsevier B.V.Iron-based sulfides as anode materials for sodium ion batteries (SIBs) has been widely concerned because of low cost and high specific capacity. In this work, a facile and novel method is designed to prepare iron-based sulfides as anode materials for SIBs. A ternary FeS2-Fe7S8-FeCl2 composite is synthesized from FeCl3·6H2O via alcohol reduction and solid-phase sulfide. The structure and morphology of the obtained samples are characterized by XRD, XPS, SEM and TEM. Compared with binary FeS2-Fe7S8, FeS2-Fe7S8-FeCl2 exhibits enhanced electrochemical performance for SIBs. A specific capacity of 620 mAh g?1 at 200 mA g?1 after 90 cycles is obtained. In addition, FeS2-Fe7S8-FeCl2 delivers excellent rate performance (510 and 461 mAh g?1 at 1.0 and 2.0 A g?1). This new method for preparing iron-based sulfides has positive value for the synthesis of other sulfides.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, the effect of ionic substitution at the Mg-site in pure Li3Mg4NbO8 ceramics, including sintering characteristics and microwave properties, has been investigated for the first time. A novel Li3(Mg1?xZnx)4NbO8 ceramic has been successfully synthesized via the solid-phase reaction method by replacing Mg2+ with appropriate amounts of Zn2+. The relationship between crystal structure and properties has been established based on complex chemical bonding theory. There is a strong correlation between dielectric constant and ionicity, while the quality factor is related to the density and the lattice energy. The temperature coefficient of the resonance frequency and the dielectric constant after correction for porosity are closely related. Doping with appropriate amounts of Zn2+ can significantly improve the properties of pure Li3Mg4NbO8 ceramics. The Li3(Mg0.96Zn0.04)4NbO8 ceramic obtained at x = 0.04 has the following sintering properties at 1075 °C: εr = 15.0 ± 0.08, Q×f = 121,157 ± 1300 GHz, τf = ?8.23 ± 0.11 ppm/°C, which combines characteristics of low dielectric constant, high quality factor, and temperature coefficient close to zero. Therefore, the resulting ceramic can be an ideal microwave dielectric material for the miniaturization and integration of microwave devices in 5 G.
查看更多>>摘要：? 2022 Elsevier B.V.Controlled microstructures play a pivotal role in upgrading the microwave absorption properties of materials. Herein, ScFeO3 ceramics with a controllable three-dimensional (3D) network structure were prepared by adjusting the sintering temperature. Specifically, the effect of sintering temperature on microstructure and microwave absorption properties were investigated. The results show that ScFeO3 ceramics with the sintering temperature of 1300 oC possess the superior dielectric and magnetic loss capabilities for incident microwaves, which attributes to the ideal 3D network microstructure enhancing the impedance matching characteristic. Besides, this unique 3D network microstructure not only provides multiple channels for multiple reflecting and scattering of microwaves, but also offers abundant interfaces to dissipate microwaves. Furthermore, the natural resonance effect efficiently increases the magnetic loss. The optimal ScFeO3 samples possess the minimum reflection coefficient (RCmin) of ? 57.4 dB at 17.44 GHz with a thickness of 2.45 mm and an effective absorption bandwidth (EAB) covering the whole Ku band (5.6 GHz) with a thickness range of 1.35–1.55 mm. It is believed that ScFeO3 ceramics can be new promising microwave absorption material with thin, broadband, and strong absorption performance.
查看更多>>摘要：? 2022 Elsevier B.V.The rapid solidification behaviour of binary aluminum copper alloys in the hypoeutectic range of compositions has been studied in this work. Solidification at cooling rates up to 40,000 °Cs?1 can be achieved using a chip-based calorimeter, but present challenges in sample preparation and temperature correction, which are addressed in this work. Data from calorimetry has been used to produce fraction of solid curves which are important input to metal manufacturing processing models. Undercoolings range from around 50 °C at 100 °Cs?1 to around 100 °C at 40,000 °Cs?1. From these, a kinetic phase diagram was constructed for the hypoeutectic region of the Al-Cu system, for cooling rates up to 40,000 °Cs?1. The undercoolings measured in this experiment are considerably higher than those predicted theoretically for growth-based rapid solidification, but not as high as those predicted under homogeneous nucleation.
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