查看更多>>摘要：? 2022 Elsevier B.V.The heterojunction formed by semiconductors with a matching electronic energy level structure can effectively promote charge transfer, thereby greatly improving the photocatalytic hydrogen production activity of the catalyst. Herein, the Cu3Mo2O9/TiO2 hybrid was prepared via a simple mechanical mixing method. In the binary composite, the p-n heterojunction formed between Cu3Mo2O9 and TiO2 can favor the charge separation, resulting in excellent hydrogen production rate of 3401.9 μmol·g?1·h?1, it is 14.5-fold of pristine TiO2. According to the optional and photoelectrochemical properties, it can be confirmed that Cu3Mo2O9 plays a pivotal role in accelerating charge transfer and improving light absorption capacity of the composite. As a new type of photocatalyst, there is very limited information on Cu3Mo2O9 for its application in photocatalytic hydrogen production. This work provides the possibility to expand application range of Cu3Mo2O9 in energy conversion.
查看更多>>摘要：? 2022 Elsevier B.V.Clinically, multidrug resistant (MDR) bacteria caused by the abuse of antibiotics and the formation of biofilms are the two major obstacles to the treatment of bacterial infections. The utilization of noble metal materials has wide prospects to therapy pathogenic bacterial infections as the substitutes of antibiotics. Noble metal nanoparticles (NMNPs), especially gold (Au), silver (Ag), and platinum (Pt), have been attaching great attentions in antimicrobial field, owing to their multiple bactericidal properties, simple synthesis methods, good photo-responsive performance, etc. NMNPs can kill bacteria and eradicate biofilms by disrupting cell membrane potential and stability, binding to biological macromolecules (DNA or enzymes). Additionally, some NMNPs can produce hyperthermia locally or radical oxygen species (ROS). The underlying mechanism is that these NMNPs can be excited under light with different wavelength to exhibit photothermal and photocatalytic effect, aroused by the surface plasmon resonance of activated electrons. In this review, NMNPs and their functionalized nanocomposites for combating pathogenic bacterial infections are reviewed. Herein, the synthetic methods and antibacterial mechanisms of noble metal nanomaterials are discussed. Finally, it's important to balance antibacterial efficiency and metallic poisoning, specifically for safety assessment in biomedical application.[Formula presented]
查看更多>>摘要：? 2022 Elsevier B.V.The curved structure and hierarchical structure are two effective strategies to improve the efficiency of electrocatalysis. Herein, hierarchical nitrogen-doped curved MoS2 embedded in graphite oxide nanosheets (MoS2-NGO) were developed via a flexible hydrothermal process and followed by nitrogen doping aiming to improve the oxygen reduction reaction (ORR) electrocatalytic activity. For the prepared MoS2-NGO, the curved MoS2 with tailored electronic structure can strengthen the mechanical strength of GO nanosheets, promoting the formation of robust hierarchical GO nanosheets, which can accelerate electron/mass transmission for beneficial ORR electrocatalytic process. The optimal MoS2-NGO-10, with a close to four electron reaction pathway, showed sharply enhanced catalytic capability for ORR compared to most reported MoS2 catalysts. As a cathode catalyst, a homemade MoS2-NGO-10-driven zinc air battery (ZAB) delivered a high peak power density of 150 mW cm?2 as well as robust catalytic durability when compared to commercial Pt/C-driven ZAB. This work highlighted the significance of monolithic structure comprising of curved MoS2 and hierarchical GO nanosheets on enhancing the overall electrocatalytic performance for ZAB and other energy conversion systems.
查看更多>>摘要：? 2022 Elsevier B.V.Due to its unique layered structure, tungsten disulfide can be used as an excellent co-catalyst in photocatalytic reactions. In this study, the lamellar WS2 was prepared by the liquid-phase exfoliation method, and the lamellar 2D WS2 has a large specific surface area and many active sites to promote the performance of the photocatalyst.The lamellar WS2 was embedded in CdS nanoparticles by hydrothermal synthesis. Compared with single CdS, the degradation efficiency of the obtained WS2/CdS composite material is 1.8 times higher than that of single CdS under visible light irradiation. Structural characterization shows that the enhanced photocatalytic activity of WS2/CdS composites is closely related to the unique structure of the heterojunction structure between WS2 and CdS that accelerates the transfer of photoexcited electrons. The two-dimensional sheet-like WS2 provides more reaction sites for the CdS attached to it, which improves the absorption of visible light and the migration rate of photogenerated carriers. At the same time, based on first-principles calculations, the charge transfer at the heterojunction interface between WS2 and CdS was obtained. The results show that a unique type II heterojunction is formed after the intercalation of lamellar WS2 in CdS nanoparticles due to the increased band gap of monolayer WS2. This unique structure makes WS2/CdS composite material promising to become a highly efficient multi-purpose photocatalyst.
Wang Z.Panicaud B.Labergere C.Grosseau-Poussard J.-L....
15页
查看更多>>摘要：? 2022The present article describes the finite element analysis of mechanical evolution during high temperature oxidation of a metallic alloy. The concerned phenomena are the stress evolutions with time and space in Ni30Cr + Cr2O3 system during oxidation in the range 800–1000 °C. The forming of an oxide layer on chromium-based alloys in oxidizing environments for high temperature applications provides a good protection against further oxidation. During this oxidation, stresses develop in both oxide layer and metallic substrate, which may cause further layer cracking or spallation and limit the lifetime of alloys in such a challenging environment. In order to investigate the stress distributions, a full thermomechanical model is implemented in the commercial finite element software Abaqus/Standard through a UMAT FORTRAN subroutine. The time-dependent stress is especially calculated and compared to experimental results from bibliography. Different temperatures are considered to estimate their influence on the different phenomena and quantities of the mechanical state. Numerical values of stresses as well as for material parameters are provided in this study.
查看更多>>摘要：? 2022 Elsevier B.V.The microstructure evolution and its effect on the strength properties and fatigue performance of the Al-Cu-Mg alloy are investigated by using optical microscope (OM), scanning electron microscope (SEM), electron back-scattered diffraction (EBSD), X-ray diffraction (XRD) and transmission electron microscope (TEM). Results show that the strength-ductility trade-off can be improved and the fatigue crack propagation (FCP) rate of the Al-Cu-Mg alloy can be reduced by refining Goss-oriented grains. Post-fatigue electron back-scatter diffraction revealed that the strain homogenization can make the interior of fine Goss-oriented grain to occur the tiny deformation, which is not easy to transmit damage to adjacent grains. Therefore, refining Goss-oriented grains not only increases the strength but also improves the ductility and promotes crack deflection, reducing the FCP rate.
查看更多>>摘要：? 2022 Elsevier B.V.We design and synthesise a new high-entropy ceramic Hf0.25Zr0.25Ce0.25Y0.125Si0.125O2-δ through a hybrid mixing of non-metal and metal atoms. First-principles calculations predict the thermal stability of the single-crystal phase at high temperatures. XRD and EDS mapping confirm a single cubic fluorite phase with a uniform elemental distribution. In-situ high-temperature XRD shows that the phase is stable with no phase separation or secondary phases. The measured mechanical and thermal properties are comparable with reported high-entropy fluorite oxides. Our results add to the compositional space of high-entropy ceramics for a wide range of applications from thermal insulators to electronics.
查看更多>>摘要：? 2022 Elsevier B.V.Low-cost β-type Ti–14Mn–(x)Zr (x = 0, 3, or 6 wt%) alloys were developed and prepared using single-electrode arc furnace, and the effects of the zirconium (Zr) content and thermomechanical treatment on the phase stability, microstructural evolution, hardness, compressive stress, and corrosion resistance of the alloys were studied. The alloy thickness was reduced by approximately 45% by hot forging at 900 °C and were then water quenched and subsequently aged at 500 or 700 °C for different times. The combination of the proper Zr content, hot forging, and aging improved the alloy hardness, strength, and ductility. The dual (α + β) structure formed in the 6Zr alloy forged and then aged at 700 °C for 60 ks resulted in a high compressive yield stress of 1127 MPa and malleability above 70%. The forged and annealed alloys exhibited superior properties to commercial Ti–6Al–4 V (lower cost, corrosion resistance, and mechanical properties). The study findings elucidate the relationship between the composition and processing properties of low-cost Ti–14Mn–(x)Zr alloys for potential biomedical applications.
查看更多>>摘要：? 2022 Elsevier B.V.Metal additive manufacturing, mainly direct metal laser sintering (DMLS), is presiding over all the mechanical and manufacturing segments with its fascinating progress. Several studies have proved that the build orientation of the additive manufacturing (AM) process is very significant and influential on the mechanical properties. In this study, In718 samples were fabricated through DMLS with different Scan Orientation Strategies (SOS) of 670 (sample A), 670 + 900 (sample B), and 900 (sample C), and their impacts on mechanical characteristics and microstructures were discussed. The study revealed that due to a higher rate of elemental segregation, sample B exhibited a UTS of 1231 Mpa, which is approximately 17.21% greater than sample C and 8.36% greater than sample A. In the same way, the percentage elongation of sample C is 21% greater than that of sample B and 10.5% superior to sample A. Images obtained using a scanning electron microscope (SEM) and an optical microscope (OM) were analysed to support the specimens' fractographies, columnar pattern growth, and elemental segregation. The fractured surfaces of tensile samples A & C revealed uniform fracture and equiaxed failures with deep dimples, whereas the fractured surface of sample B revealed the presence of an intermetallic configuration displaying brittle and low plastic deformation.
查看更多>>摘要：? 2022 Elsevier B.V.In metallic materials, the nature of passivation film plays an important role in governing corrosion behavior. The present work focuses on a detailed analysis of the passivation film characteristics of a transformation induced plasticity Fe39Mn20Co20Cr15Si5Al1 (at%) high entropy alloy (HEA) in 3.5 wt% NaCl solution at room temperature. The characteristics of the passivation film were assessed using a potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). The microstructural analysis of the alloy achieved using electron backscattered diffraction revealed that it consisted of two different phases: γ phase (face-centred cubic crystal) and ε (hexagonal closed pack), with the area fraction of ε phase being 96.5%. The electrochemical experiments showed that the HEA maintained excellent uniform corrosion resistance but low pitting corrosion resistance. The scanning electron microscopy revealed deep pits covered with perforated layers, and the average pit size and pit depth was determined to be 202.8 μm and 168 μm, respectively. The EIS revealed a bilayer type of passivation film formations at different voltages. For the passivation film grown at ?0.1 V, the upper layer film thickness was 2.08 nm and the inner layer film thickness was 3.14 nm. For the passivation film grown at ?0.05 V, the upper and inner film thicknesses were 1.78 nm and 3.10 nm. The passivation film resistance was found to be one order of magnitude higher for the passivation films grown at ?0.1 V and ?0.05 V than that for the naturally grown passivation film. The XPS of the sample that corroded during the potentiodynamic polarization test revealed that the passive layer contained Fe, Mn, Co, Cr, Si, and O elements as metal oxides and hydroxides with Mn and Cr based chemical species present as dominant species. Their oxidation states were estimated to be present as Fe2+, Fe3+, Mn3+, Co2+, Cr3+, Si4+, O2-, and OH1- along with their corresponding metallic states. According to the proposed corrosion mechanism, a bilayer type of passivation film forms on the alloy. The film's upper layer is rich in Mn and Cr and the inner layer is devoid of Mn and Cr. The detection of two particles in the same pit with two different chemical compositions seems to corroborate the formation of a bilayer passivation film and its chemical compositions.
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