查看更多>>摘要：Zinc ion batteries (ZIBs) are newly emerging and widely attracted energy storage devices owing to its advantages of intrinsic safety and low-cost effectiveness. Herein, we reported a nanorod-like MnO_2 cathode material composited with carbon and pyrrolic nitrogen by in-situ co-precipitation method at room temperature, which was used as ZIB cathode to deliver a high specific capacity of 339 mAh g~(-1) at 100 mA g~(-1) and a long cycle stability over 2000 cycles at 1000 mA g~(-1), resulting in the ultrahigh coulombic efficiencies approximate to 100%. The improved performance was attributed to the enhancement of structural stability and more zinc ion insertion sites after introducing the 2-methylimidazole (2-MI) coating layer. The phase transition of α-MnO_2 @2-methylimidazole (α-MnO_2 @2-MI) and the formation of more porous architecture could be the origin of the continuous capacity increasing in the initial several cycles, which was proved by the results of the ex-situ x-ray diffraction (XRD) and the scanning electronic microscope (SEM). This method can be a more realistic choice for the further commercial applications of low-cost and easily-accessed ZIBs with excellent electrochemical performance.
查看更多>>摘要：Application of the super-wettability material is one of the most ideal approaches to achieve oil/water separation. The construction of the super-wettability material surface is the key to significantly boost the separation efficiency. In this work, the ZnO@Cu_2O honeycomb-likes hierarchical micro/nano-structure copper mesh (ZnO@Cu_2O/CM) is facilely fabricated through the combination of oxidation and hydrothermal deposition. Accordingly, superhydrophilicity/underwater superoleophobicity can be achieved, which endows over 99% separation efficiency as well as considerable permeation flux (>38120 L-m~(-2)-h~(-1)) for ZnO@Cu_2O/CM toward various oil/water mixtures. Besides, the combination of ZnO and Cu_2O produces a p-n heterostructure to further reduce the recombination rate of electron and hole, resulting in the improved the photocatalytic activity. The removal efficiency for methylene blue (MB) of ZnO@Cu_2O/CM could be improved to 98.1%, nearly 1.6 times than that of Cu_2O/CM. Various stability tests demonstrate that the material exhibits good mechanical stability, anti-corrosive property and thermal durability under harsh environments. Furthermore, cyclic experiments reveal that ZnO@Cu_2O/CM exhibits fascinating reusability. In conclusion, the as-synthesized dual-functional mesh performs favorable photocatalytic activity and super-wettability, which can realize wastewater remediation at low cost and energy consumption.
查看更多>>摘要：The poling of macro fiber composites (MFCs) as a vital part for manufacturing usable samples, is related with but different from that of their piezoelectric phase owing to the existence of interdigitated electrodes. Herein, beginning with the quantitative relationship between effective electric field and external electric field obtained by finite element analysis, the prediction and optimization of poling condition for lead zir-conate titanate (PZT) based-MFCs was presented. The results demonstrate that the predicted values agree with the experimental results, specifically, the poling field range of the investigated MFCs is from 16.7 kV/ cm to 33.3 kV/cm. The piezoelectric and dielectric properties of MFCs are improved by adjusting the poling condition up to a suitable value, whereas are degraded due to the interaction of domain alignment and electric field concentration. The optimal poling condition of the MFCs is 26.7 kV/cm for 10 min at room temperature. This research contributes to realizing the personalized-customization of MFCs.
查看更多>>摘要：The effect of Cu addition on the microstructural evolution and mechanical properties of hypoeutectic Al-10Mg_2Si alloys was investigated. It was found that Cu addition could effectively refine the primary a-Al grain. Simultaneously, the coarse eutectic Mg_2Si was also modified to be fine coral-like. The constitutional supercooling and the multiple nanosized precipitating layers at the edge of the eutectic Mg_2Si cause the branching and refining of the eutectic Mg_2Si through effectively restricting the growth of eutectic Mg_2Si, while the Cu-rich clusters and nanosized precipitates on the surface of the end of the eutectic Mg_2Si prevent the diffusion of the solute atoms such as Al, Mg and Si, and the growth of eutectic Mg_2Si grains is physically limited, resulting in the decrease of the length of eutectic Mg_2Si. The strength and ductility of the Cu-added Al-10Mg_2Si alloys were simultaneously improved, and the fracture failure mode transforms from brittle failure to ductile failure. The mechanism of mechanical properties enhanced by Cu addition was discussed.
查看更多>>摘要：In this study, the electrocaloric (EC) effect was enhanced at room temperature for (Ba_(0.904)Ca_(0.096)) (Zr_(0.136)Ti_(0.864)-xFe_x)O_3 (BZT-0.32BCT-xFe 0 ≤ x ≤ 0.015) thin films prepared on Pt/Ti/SiO_2/(100)Si substrates. The existence of an orthorhombic phase in the Fe-doped thin films at room temperature was confirmed by X-ray diffraction and Raman spectra. Tetragonal, orthorhombic, and rhombohedral phases coexist in all the investigated Fe-doped thin films. The relative content of the orthorhombic phase is most prominent at x = 0.0075. The BZT-0.32BCT-xFe thin film exhibits excellent properties with a giant EC effect (ΔT = 22.99 K, E = 1050 kV/cm, and T = 307 K) at x = 0.0075 compared to the undoped thin film, stemming from multiphase coexistence and a larger orthorhombic phase. The results of this study are useful for developing lead-free electrocaloric materials with superior properties.
查看更多>>摘要：Enthalpic interaction between the elements determines the stability of the local structures in the alloy system. Multicomponent synergistic effect is expected to improve the thermal stability and the relevant properties, by regulating the enthalpic interaction. In this work, the composition of Cu-Ni-Sn alloys is explained by introducing the cluster-plus-glue-atom mode, and the strong and weak enthalpic interaction elements Si and Zn, respectively, are chosen for multi-componentization of Cu-Ni-Sn alloys. The results demonstrate that the synergistic effect of Zn and Si improves the stability of both the Cu matrix and D0_(22) or L1_2-γ' phase, inhibits the discontinuous precipitation effectively and gains a notable higher strength-over-resistivity ratio (H_(R/ρR)) than the Cu-15Ni-8Sn (wt. %) (C72900) alloy. After adding Si and Zn, the reinforcing enthalpic interaction between the elements is the crucial factor for the stability enhancement of the alloys, and it is embodied by two aspects: (a) the reducing elastic strain energy in the solution treated alloys; (b) the more homogeneous surface potential and the higher work function in the age treated alloys. Additionally, Compared with the Cu_(80)Ni_(15)Sn_5 alloy that based on the ideal cluster formula, the Cu_(79.68)Ni_(15.63)Sn_(4.69) alloy, based on the modified cluster formula: {[Cu-Cu_xNi_(12-x)]Cu_3}_a{[Sn-Ni_yCu_(12-y)]Sn_3}_(16-a), possesses a preferable thermal stability whatever solution treated or age treated state, and exhibits a decreasing amount of discontinuous precipitation although has a slightly lower H_(R/ρR), which is beneficial to the improvement of the workability of the alloys. The modified cluster formula is more suitable for the compositional design of Cu-Ni-Sn alloys. The work provides an effective theoretical and experimental basis for the composition design of high stability Cu-Ni-Sn alloys.
查看更多>>摘要：In this work, a novel Cu decorated Fe_3O_4@ CeOHCO_3 nanocomposite (Cu-Fe_3O_4@CeOHCO_3) has been prepared by a one-step hydrothermal method. Fabricating into the electrode, the electrochemical properties of the prepared materials were characterized by cyclic voltammetry (CV), galvano-static charge-discharge (GCD) test and electrochemical impedance spectroscopy (EIS). The specific capacitance of the Cu-Fe_3O_4@ CeOHCO_3 electrode was 324.7 F g~(-1) at a current density of 1.0 A g~(-1) with a capacitive retention of 88.3% after 1000 charge-discharge cycles. The assembled asymmetric supercapacitor(ASC) device can provide an energy density of 35.4 W h kg~(-1) with a high power density of 781.9 W kg~(-1). DFT calculations prove that the surface modification of Cu functions significantly in modulating the electronic structure and super-capacitive properties of CeOHCO_3. Our self-assembled Cerium-based composite may initiate the suitability for energy storage devices and provides a valuable reference for the fabrication in sodium Ion supercapacitors.
查看更多>>摘要：In the present work, a novel strategy is proposed to control the microstructures of microporous spinel aggregates and improve their strengths. This strategy controls the in-situ decomposition behavior of raw material particles and the Kirkendall effect through preheating magnesite and Al(OH)_3, then milling with balls and water. Thus, the expected microstructures of microporous spinel aggregates can be obtained. Four microporous magnesium aluminate spinel aggregates of stoichiometric ratio were prepared using magnesite, Al(OH)_3, calcined magnesite, and calcined Al(OH)_3. The microstructures and strengths of microporous spinel aggregates were analyzed by XRD, SEM, image analysis method, etc. The microporous spinel aggregates prepared from magnesite and Al(OH)_3 had slightly lower apparent porosity (58.2%) than the one (59.2%) synthesized from Al(OH)_3 and calcined magnesite. In addition, the median pore size significantly reduced from 9.5 to 6.8 um, and the compressive strength dramatically increased from 7.3 to 15.2 MPa. These results verify the reliability of this strategy.
查看更多>>摘要：Effect of Mn content on the microstructure and corrosion resistance of Al-Cu-Mg-Mn alloys was examined by optical microscope (OM), scanning electron microscope (SEM), tensile tests, pitting corrosion and electrochemical tests. It is shown that increase of Mn content can accelerate the aging process of the Al-Cu-Mg-Mn alloys, which is beneficial to shorten heat treatment time. Polarization curves indicate that the corrosion current density and corrosion rate of Al-4Cu-2Mg-1.2Mn alloy are the lowest compared with Al-4Cu-2Mg-0.6Mn and Al-4Cu-2Mg-0.9Mn alloys for both the as-cast and heat-treated conditions. Electrochemical impedance spectroscopy (EIS) tests also demonstrate that Al-4Cu-2Mg-1.2Mn alloy displays the highest resistance. The maximum pitting corrosion depth of the as-aged Al-4Cu-2Mg-1.2Mn and Al-4Cu-2Mg-0.6Mn alloys is about 65 um and 110 um, respectively. Therefore, Mn addition can improve the mechanical properties and corrosion resistance of the Al-Cu-Mg alloys.
查看更多>>摘要：The CrCoNiSi_xAl_x(x = 0.1, 0.2) medium entropy alloys (MEAs) were designed to achieve significant improvement in strength and strain hardening via the minor addition of Si and Al elements to the CrCoNi MEA. The B2 + σ precipitation structure was formed on the CrCoNiSi_(0.2)Al_(0.2) MEA. Compared to CrCoNi MEA, the yield and ultimate tensile strengths of the CrCoNiSi_(0.2)Al_(0.2) MEA enhanced from 380 MPa to 850 MPa and 790-1287 MPa, respectively, while the uniform elongation was 23±5% that outperformed various advanced steels and Al-added MEAs/HEAs. The Orowan+shearing precipitation hardening mechanisms together with the deformation twins in a face-centered cubic (FCC) matrix were identified to improve the strength and strain hardening capacity. These findings provide guidance for the development of precipitation-hardened MEAs/HEAs with strength-ductility synergy.
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Elsevier