查看更多>>摘要：? 2022 Elsevier B.V.The friction stir lap welding (FSLW) was employed to join the dissimilar 5052 Al alloy and DP590 steel. The intermetallic compound (IMC) formation area and thickness increased linearly with increasing rotation speeds at 300 mm/min welding speed. Microvoid and gap defects existed on low-rotational-speed-produced lap interfaces, disappearing with increasing rotation speeds. However, cavities defects neighbouring the large-sized steel fragment appeared in the stir zone of the Al matrix with rotation speeds higher than 750 rpm. The negative influences from the Al-rich IMCs layer exceeding 1.5 μm thick and the aggravating internal cavities defects significantly reduced the joint strength. Correspondingly, the fracture mode of the friction stir lap welded 5052 alloy and DP590 steel was converted from the semi-brittle fracture into the full-brittle fracture. The maximum tensile shear force of 4.52 kN reached 75.2% of the Al 5052 base metal, obtained at the rotation speed of 750 rpm. However, from the combined perspective of integral bearing load capacity and local shear strength, the rotation speed of 500 rpm was recommended to achieve sound FSLW joints of Al5052/DP590.
查看更多>>摘要：? 2022 Elsevier B.V.Solid oxide electrochemical cells are promising devices for energy conversion and chemical synthesis. In this respect, one of the main challenges to improving cell performance is the decrease in the polarisation resistance (Rp) of the oxygen electrodes. Here, the electrochemical properties of composite electrodes of Ba2Co9O14/Ce0.8Gd0.2O2-δ (BCO/CGO) are investigated by electrochemical impedance spectroscopy at 600–800 °C. The composite with 50 vol% CGO exhibits the lowest polarisation resistance, 0.3 Ω cm2 at 600 °C in O2. The comparatively superior performance results from an increased triple-phase boundary (TPB) length due to the increased percolation of both phases. This successful result presents a high-performing oxygen electrode for solid oxide electrochemical systems.
查看更多>>摘要：? 2022 Elsevier B.V.In the present work, the TiZrHfNbFex (x = 0, 0.25, 0.5, 0.75, 1, 1.5, and 2, molar ratio) refractory high-entropy alloys (HEAs) were developed. The microstructure, mechanical properties, corrosion and wear resistance of the Ti-Zr-Hf-Nb-Fe HEAs were investigated. The Ti-Zr-Hf-Nb-Fe HEAs exhibited a dendrite structure with body-centered-cubic (BCC) + Laves phases. Among them, the TiZrHfNbFe0.5 HEA displayed good comprehensive mechanical properties with the hardness of 420 HV, compressive strength of 1450 MPa, and plastic strain of about 8%. In addition, the TiZrHfNbFe0.5 HEA possessed better corrosion resistance than that of the Ti6Al4V and the other Ti-Zr-Hf-Nb-Fe HEAs in phosphate buffer saline (PBS) solution, which might be related to the generation of more protective oxide films on its surface. Furthermore, the wear resistance of the Ti-Zr-Hf-Nb-Fe HEAs increased with the raise of the Fe content. The TiZrHfNbFe0.5 HEA demonstrated superior dry and wet wear resistance in comparison with the Ti6Al4V alloy. Therefore, the good mechanical properties, high corrosion, and wear resistance, the biocompatible constituent elements, as well as the low cost of the Fe addition render the Ti-Zr-Hf-Nb-Fe HEAs as promising candidates as biomedical-implantation materials.
查看更多>>摘要：? 2022 Elsevier B.V.The phase diagram of the Cu2?XSe-Sb2Se3 system is revisited to clarify ambiguity/disagreement in previously reported data. Ternary Cu3SbSe3 and CuSbSe2 compounds were obtained. In order to confirm that the phases have been identified correctly, crystal structures were solved, and the energy band gaps measured. For the sample containing 75 mol% Sb2Se3 and 25 mol% Cu1.995Se the temperature range of the stability of the high-temperature CuSb3Se5 phase was determined for the first time. This phase is formed at 445 °С, decomposes following a peritectic reaction at 527 °С, and can be quenched. A high-temperature X-ray diffraction study of a sample containing 75 mol% Sb2Se3 and 25 mol% Cu2Se allowed us to measure the thermal expansion of the CuSbSe2 and Sb2Se3 phases present in the sample. The anisotropy of thermal expansion of CuSbSe2 is similar to that of As2S3 (orpiment); thermal expansion of Sb2Se3 is similar to that of AsS (realgar). The 6 balance equations of the invariant phase transformations involving all the ternary compounds existing in the Cu2?XSe-Sb2Se3 system were suggested for the first time. The temperature and the enthalpies of all these transformations were measured. A phase diagram of the Cu2?XSe-Sb2Se3 system was found for the first time in all the range of concentrations at temperatures from ambient to the complete melting. This diagram takes into consideration the phase equilibria that involve all the ternary compounds that are possible in this system. The liquidus of the Cu2?XSe-Sb2Se3 system was calculated according to Redlich-Kister equation; it agrees with the experimental data within 1–17 °С.
查看更多>>摘要：? 2022 The Author(s)Magnetic double perovskite oxides have steadily emerged as an important class of functional materials. A clear understanding of the complex interactions that govern the magnetic behavior, and thereby, the functionality in these mixed valence compounds, however, remains elusive. In this study, we show that the complex nanostructure that forms in these compounds is at the root of their magnetic behavior. Using complementary experimental and micromagnetic simulation results, we have uncovered the complex nanostructure of polycrystalline Sm2CoMnO6, a typical double perovskite oxide, and established how the nanostructure drives its magnetic behavior. Our results show that Sm2CoMnO6 exhibits a Griffiths phase with the formation of ferromagnetic clusters above the ordering temperature. The isothermal magnetization curves show no sign of saturation, even at the highest measured field (9 T), and irreversibility in the entire magnetic field range. Despite a very clear indication of the presence of antiferromagnetic antisite defects, surprisingly, no antisite defect-induced exchange bias occurs. This is explained from the micromagnetic simulations that confirm the presence of ferromagnetic nanoclusters and nanosized, random, and uncorrelated antisite defects, resulting in no exchange bias. This work provides a clear understanding of the role of antisite defects, in particular, on how their structure can lead to the presence/absence of exchange bias. The fundamental insight offered in this work fills an important knowledge gap in the field and will be of immense value in realizing the true potential of double perovskite oxides for future technological applications.
查看更多>>摘要：? 2022 Elsevier B.V.Air annealing of MoO3 bottom layer is a simple and highly efficient surface treatment method to prepare ultrathin, continuous, and smooth Ag layers in MoO3/Ag/MoO3 (MAM) transparent conductive films (TCFs) for indium tin oxide (ITO)-free organic solar cells (OSCs). Air annealing can readily oxidize MoO3 surface and increase surface energy of the MoO3 layer, which significantly enhances the adhesion between Ag and MoO3. When the MoO3 bottom layer is annealed at 200 °C, moreover, the treatment yields a flatter MoO3 surface, which positively influences the growth of Ag nanostructures. Eventually, an almost homogeneous, smooth, and continuous surface morphology of the ultrathin Ag films with a thickness of 6.5 nm was obtained. By employing air-annealed MoO3 bottom layer, the MoO3 (200 °C, 10 min)/Ag (6.5 nm)/MoO3 TCF had higher optical transmittance (Tav = 83.6%) and lower sheet resistance (Rs = 6.5 Ω/sq) than unannealed MAM or commercial ITO TCFs, thereby obtaining the higher value of figure of merit (FTC = 2.6 ×10?2 Ω?1). When used as the transparent electrode in organic solar cells (OSCs), the improved optoelectrical properties of the MoO3 (200 °C, 10 min)/Ag (6.5 nm)/MoO3 electrode result in increased short-circuit current density (Jsc = 2.27 mA cm?2) and fill factor (FF = 54.8%) of OSCs in comparison to devices based on unannealed MAM and ITO electrodes, leading to an improvement in power conversion efficiency (PCE = 0.62%). From the results of photocurrent measurements, air annealing MoO3 increases exciton generation in active layers and reduces the carrier back-transfer induced recombination at the anode contact, yielding the enhanced photovoltaic performance.
查看更多>>摘要：? 2022Rechargeable aqueous zinc-ion batteries (AZIBs) show enormous potential in large-scale energy supply and storage attribute to safety and economy. However, the slow transport dynamics and unstable structural stability of the conventional cathodes hinder the further development of AZIBs. In this work, carbon-coated hydrated vanadium dioxide (HVO@C) was prepared by a one-step hydrothermal method. The introduction of water molecules provides suitable ambient spacing for rapidly accommodating and transporting cations, the coating of carbon further stabilizes the structure of the material and improves the conductivity of the material. The synergistic merits of pre-intercalated water molecules and carbon encapsulation are beneficial for both electron and ion transport kinetics. And the content of water molecules is controlled by regulating V/C ratio. Electrochemical results revealed that the H1.99VO@C/Zn batteries yield a good reversible specific capacity (329.0 mA h g?1 at 1 A g?1) with superior cycling stability (174.2 mA h g?1 at 5 A g?1 after 1000 cycles). This work provides a strategy for developing safe and high-performance energy storage equipment by pre-intercalated defect and carbon encapsulation.
查看更多>>摘要：? 2022 Elsevier B.V.In this paper, we investigated the structural, multiferroic, dielectric and optical properties of Aurivillius Bi6Fe1.5Co0.5Ti3-xWxO18 (0 ≤ x ≤ 0.07) ceramics. The doping of W6+ ions promoted the grain's growth and induced c-axis orientation. The remnant magnetization Mr monotonously decreased from 0.49 to 0.13 emu/g with increasing the doping level from 0 to 0.07, which was primarily attributed to the reduced Fe2+-O-Fe3+ exchange and the improved orientation growth. The remnant polarization Pr increased from 4.5μC/cm2 for x = 0–8.3μC/cm2 for x = 0.05 and then decreased to 7.2μC/cm2 for x = 0.07, the enhanced ferroelectricity was mainly related to the suppressed oxygen vacancy and larger grain size, while the weakened ferroelectricity was ascribed to the improved c-axis orientation. The Mr (0.23 emu/g) along c axis was larger 0.13 emu/g in ab plane while the Pr (7.2μC/cm2) along c axis was smaller than 9.3μC/cm2 in ab plane in x = 0.07, which demonstrated the anistropy of multiferroicity. In addition, all samples exhibited two different dielectric relaxations. The first one with activation energy ranging from 0.47 to 0.53 eV was assigned to the hopping process of electron, while the second one with activation energy varied from 1.45 to 3.63 eV was associated with the viscous motion of ferroelectric domain walls. Two direct absorption edges were demonstrated by Tauc's law in all samples. The band gap 1 increased from 1.93 to 1.95 eV due to the lower t2 g state of Fe2+. The band gap 2 varied between 2.21 and 2.28 eV, which was proposed to the competition between TiO6 distortion and Ti4+ content. These results indicate that doping donor W6+ in Aurivillius compounds is a feasible way to regulate the multiferroic and optical properties.
查看更多>>摘要：? 2022 Elsevier B.V.Metal molybdates inherit the characteristics of polyoxometalates (POMs) and have been widely used in the fields of catalysis, photoluminescence and energy storage. However, well construction of hierarchical molybdate nanostructures towards superior performance has still retained a critical challenge. Herein, hierarchical manganese molybdate (MnMoO4) nanocauliflowers are tailored from aggregated microrods utilizing dopamine as a scissor at room temperature. Meanwhile, a uniform and robust carbon coating layer can be introduced after a simple calcination. The fabricated MnMoO4/C nanocauliflowers exhibit excellent electrochemical properties as anodes for both lithium/sodium ion half/full batteries. The boosted discharge specific capacities and rate capabilities of MnMoO4/C (994 mAh g?1 at 0.1 A g?1 and 487 mAh g?1 at 2.0 A g?1 for lithium ion battery and 296 mAh g?1 at 0.1 A g?1 and 148 mAh g?1 at 2.0 A g?1 for sodium ion battery) are better than those of bare MnMoO4. Notably, the stable and sustainable cyclic property with 1500 times for lithium ion battery and 5000 times for sodium ion battery without obvious capacity fading is much superior to the state-of-art results of many other reported molybdates. This simple yet effective strategy demonstrates the feasibility of simultaneous structure engineering and surface modification of molybdates.
查看更多>>摘要：? 2022 The Author(s)Luminescence thermometry exploiting luminescence kinetics as a thermometric parameter is regarded as one of the most reliable temperature readout techniques. Transition metal ions are of particular interest in this application which is due to the possibility of modulating their spectroscopic properties by changing the strength of the crystal field of the matrix. In this work, we present a strategy to modulate the thermometric parameters including the relative sensitivity and useful temperature range of luminescent thermometers based on the lifetime of Ti3+ ions by introducing lanthanide (Ln3+) doping in SrTiO3 and CaTiO3. The mutual effect of the distortion of the local symmetry of the Ti3+ ions associated with the introduction of Ln3+ ions and/or the Ti3+ → Ln3+ energy transfer enabled relative sensitivities of SR = 5.87% K?1 at 140 K for SrTiO3:Dy3+ and SR = 4.51% K?1 at 251 K for CaTiO3:Gd3+.
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