查看更多>>摘要：? 2022 Elsevier B.V.The Al-Cu-Li alloys with different grain sizes were manufactured through different routes and treated with T34 before the creep aging process. Their creep-aging behaviors at 160 °C under 175 MPa were investigated and their corresponding mechanical properties were tested. Their microstructure was characterized by EBSD and HAADF-STEM. The results show that the total creep strains increase with increasing grain size. The creep strain of specimens with an average grain size of 53.4 μm is twice as that with an average grain size of 12.2 μm. However, their yield and tensile strengths are grain size independent. This appearance could be explained by the large creep strain achieved before the secondary primary creep stage, which is contributed by dislocation motion and increases with increasing grain size. When strengthening precipitates start to nucleate and grow, the creep resistance of dislocations sharply increases and Harper-Dorn creep becomes the main creep mechanism. The alloys with different grain sizes have similar precipitates and substructures in their peak-creep-aged state, leading to their similar yield and tensile strengths at room temperature.
查看更多>>摘要：? 2022 Elsevier B.V.Non-precious metals as oxygen evolution reaction (OER) electrocatalysts for water-splitting purposes has recently attracted extensive attention. However, alloy ribbons of non-precious metals as self-supported electrodes for OER electrocatalysts have rarely been reported. Here we report a melt-spinning method to prepare an Fe35Co20Ni20Mo20Si5 alloy ribbon, which serves as a self-supporting electrode OER electrocatalysts by dealloyed etching. The etching expands the active surface area of the alloy ribbon which increases the abundant active sites. The experimental results showed that the electronic structure of FeMoSi on the ribbons surface excellently facilitates the OER process. The electrocatalytic activity test showed that the etched alloy ribbon exhibited excellent OER activity in 1 M KOH alkaline solution, with an overpotential of only 260 mV at a current density of 10 mA cm?2, a Tafel slope as low as 37.9 mV dec?1 and a stability of up to 90 h without decay. This work serves as a promising guide for the use of alloy ribbons as a highly efficient and self-supported electrocatalyst.
查看更多>>摘要：? 2022 Elsevier B.V.To improve the cathode materials performance of Li-ion batteries, an effect of nickel content in lithium borate (xNi:LiBO3) glass systems was introduced. The physical, structural, magnetic and electrochemical properties of xNi:LiBO3 glasses with x = 0, 0.15, 0.20, and 0.25 were carefully studied. XRD, XAS, and XPS techniques were used to investigate the effect of Ni contents in all glass structures. A glass structural motif was clearly confirmed by XRD and TEM results with an absence of crystallization behavior. By VSM measurement, LiBO3 based glass samples exhibited diamagnetism, while Ni doped glass samples exhibited a mixing of paramagnetism and weak ferromagnetism. Interestingly, a mixing valence state of Ni2+ and Ni3+ was observed of all glasses and local bonding distances between Ni-O and Ni-Ni were discovered ranging of 1.98–1.99 ? and 2.72–2.86 ?, respectively. Surprisingly, electrochemical properties of prepared LiBO3 glasses could be enhanced by increasing the Ni content in glass structure. In this study, the 0.25Ni:LiBO3 glass electrode showed the highest specific capacitance of 91.06 F.g?1 at a scan rate of 5 mV/s, indicating that it could be a promising glass electrode for Li ion battery.
查看更多>>摘要：? 2022 Elsevier B.V.The strengthening mechanism and stress corrosion cracking (SCC) behavior of a new Mg-6Zn-1Y-0.5Cu-0.5Zr alloy (given the name “ZWCK6100″) were investigated in this work. The results showed that the microstructure, mechanical properties and stress corrosion resistance were significantly affected by the combined addition of Cu and Y. The alloy consisted of α-Mg, Zn2Zr, CuMgZn, rod-shaped MgZn2 precipitates and I phase (Mg3Zn6Y), and displayed a balance between strength and ductility, with the yield strength, ultimate tensile strength and elongation being 320.3 MPa, 351.5 MPa and 19.8%, respectively. The main strengthening mechanisms were found to be grain refinement, second phases and texture. In addition, the stress corrosion resistance was assessed by slow strain rate testing and fractography. These tests showed that ZWCK6100 alloy exhibited improved SCC resistance and low SCC sensitivity in 3.5 wt% NaCl solution. The novel ZWCK6100 alloy may serve as a promising magnesium alloy for industrial applications.
查看更多>>摘要：? 2022 Elsevier B.V.Ferritic superalloys with an α/α′ (A2/B2) microstructure constitute an auspicious materials system for high-temperature application and could help satisfy the need for more sustainable creep resistance materials. An exciting way to improve their creep resistance further through alloy development and microstructure engineering is introducing a hierarchical network consisting of α, α′, and α″ (L21). This work investigates the formation and evolution of this microstructure in Fe-Al-Ni-Co(Cr-Mo-Ti-Cu) alloys. It has been identified that the substitution of Fe by Cr leads to the stabilization of γ (fcc, A1) at intermediate temperatures. This amount of γ was found to decrease in the presence of Mo, and the transformation is entirely avoidable by carefully adjusting the α - and γ-stabilizing elements. The observations in quinary and senary alloys led to the development of two promising hierarchical α/α′/α″ alloys with additions of Co and Cu. Both solutes are enriched in the precipitates and are expected to act as strengthening elements. Microstructural analysis of the particle size evolution in the range of 800–950 °C indicates that the precipitates undergo a non-classical ripening process at early stages with coarsening exponent deviating from the t1/3-relationship predicted by the Lifshitz-Slyozov-Wagner (LSW) theory for multicomponent alloys. Furthermore, after furnace cooling from 950 °C, a pronounced reprecipitation phenomenon was found to occur not only in the matrix but also inside the primary precipitates.
查看更多>>摘要：? 2022 Elsevier B.V.Fabrication feasibility of NiCoCrAlSi/IN-738 (HEA-15), NiCoCrAlSi/Al/IN-738 (HEA-15F) joints via plasma spark sintering (SPS) method was investigated in this study. The bonding strength and hot corrosion behavior of these systems are compared with NiCrAlY/IN-738 (NiCrAlY) joint. The mentioned high entropy alloys (HEAs) were fabricated by mechanical alloying method for 40 h in Ar atmosphere. The milled powders were then applied on IN-738 superalloy by SPS method at 1170 °C and soaking time of 15 min with an average thickness of 1.1 mm. The microstructural/phase characterization of these samples was evaluated by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. The hot corrosion behavior of these joints in 90 wt% Na2SO4 ? 10% wt. NaCl at 800 °C for 100 h were studied. Bonding strengths were evaluated using the pull-off adhesion test. The lowest amount of hot corrosion was obtained for the HEA-15 joint. The highest thickness of oxide layers after the hot corrosion test was obtained for the NiCrAlY sample (366 μm), which was higher than the HEA-15 sample (194 μm). High bonding strength of 155 MPa was obtained for HEA-15 sample which was higher than that of the other joints. This value was 114 MPa for NiCrAlY joint. Contrary to expectations, HEA-15 F sample did not show appropriate bonding strength due to the presence of surface oxides in aluminum intermediate layer.
查看更多>>摘要：? 2022 Elsevier B.V.Flexible thermoelectric materials are important as self-powered systems in wearable and flexible thermoelectric devices; to this end, using single-walled carbon nanotubes (SWCNTs) is advantageous for enhancing the overall thermoelectric performance. In this study, to further enhance the thermoelectric properties of SWCNTs and overcome the weak interfacial interaction between hydrophilic poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and hydrophobic pristine SWCNTs, a graphene quantum dots (GQDs) intermediate layer is used to couple PEDOT:PSS and SWCNTs. Multilayer films comprising PEDOT:PSS, GQDs, and SWCNTs are constructed and prepared by successively drip-coating the GQDs and PEDOT:PSS on the SWCNTs film surface. Analysis of the interfacial morphology reveals that the hydrophilic GQDs improve interfacial adhesion between PEDOT:PSS and the SWCNTs. Compared to a PEDOT:PSS/SWCNT bilayer film, the electrical conductivity of the PEDOT:PSS/GQDs/SWCNT multilayer films is enhanced, while the Seebeck coe?cient is slightly lower. Meanwhile, the thermal conductivity is significantly decreased due to the increased interfacial phonon scattering. The minimum in-plane thermal conductivity for the PEDOT:PSS/GQDs/SWCNT films is 7.4 W?m?1?K?1, resulting in an enhanced figure of merit of 1.96 × 10?3 at 298 K. Thus, the GQDs intermediate layer is beneficial for coupling PEDOT:PSS and SWCNTs layers. The strategy employed herein offers novel insights into the preparation of high-performance SWCNTs-based thermoelectric materials.
查看更多>>摘要：? 2022 Elsevier B.V.The authors regret for some errors in “Graphical Abstract” and “Fig. 18” of the above article. The corrected and final version of the mentioned figures is as follows. The authors would like to apologise for any inconvenience caused.
查看更多>>摘要：? 2022 Elsevier B.V.Understanding the microstructure evolution and mechanical property of the electron beam based process for remelting is important for manufacturing, repair, and surface modification. In this work, based on the nanoindentation theory, the sub-microscale mechanical properties of U-5.5 wt%Nb alloy (U-5.5 Nb) remelted by continuous electron beam scanning process (CEBSP) were systematically studied for the first time by the means of nanoindentation. Additionally, optical microscopy (OM) and scanning electron microscopy equipped with energy dispersive spectroscopy (SEM/EDS) were used to evaluate the evolution of the microstructure and the element redistribution. The results revealed that the microstructure and/or the microsegregation of both niobium and carbon had a significant influence on the local mechanical properties of the CEBSP treated U-5.5 Nb. A surface strengthened layer with the average elastic modulus and hardness of 68.4 ± 15.1 GPa and 4.8 ± 1.2 GPa was obtained by CEBSP, which were much higher than the corresponding values of the untreated alloy (i.e. 47.2 ± 2.8 GPa and 2.6 ± 0.3 GPa for the substrate), suggesting a 15.6–44.5% increase in the anti-wear performance. Additionally, except for plasticity, the mechanical properties including yield strength, creep resistance, and fracture toughness increased by CEBSP. Finally, based on the experimental analysis results, the relationship between microstructure and mechanical property (especially the hardness) is discussed in detail, and a model is proposed to explain the plastic deformation mechanism during nanoindentation tests.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, Pr-deficiency is presented here as an effective strategy to promote the electrochemical properties of PrxBaFe2O5+δ (PrxBF, x = 1.00, 0.97, 0.93, 0.90) cathodes for solid oxide fuel cell (SOFC). The PrxBF cathode materials were prepared by a sol-gel method. The crystal structure results show that the PrxBF (x = 1.00) is double-perovskite phase with orthorhombic structure and the PrxBF (x = 0.97, 0.93, 0.90) is tetragonal perovskite structure. Introduction of Pr-deficiency in PrxBF oxides causes the decrease of oxygen content. The average TEC values (30–850 °C) for PrxBF are mainly concentrated between 15.29 and 15.95 × 10?6 K?1. In comparison to the parent PrBaFe2O5+δ oxides, the Pr-deficiency cathodes significantly enhance the electrochemical catalytic activity while maintain the lower thermal expansion coefficient. Among the series of PrxBF cathodes, the Pr0.93BF sample obtains the lowest polarization resistance. The fitted result of impedance spectra for Pr0.93BF cathode indicates that the charge transfer process in the high frequency plays a more dominant role in the oxygen reduction reaction. Furthermore, the Pr0.93BF electrode exhibits a good tolerance to CO2. The power density of an anode supported single cell with Pr0.93BF cathode achieved 967 mW cm?2 at 700 °C. Preliminary results suggest that PrxBF oxides are expected to be promising candidates for cathode in SOFC.
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