查看更多>>摘要：Bi2WO6/BN heterojunction photocatalyst with high catalytic activity has been successfully constructed by the solvothermal synthesis. It is worth noting that the formation of superoxide radicals (center dot O2-) and hydroxyl free radicals (center dot OH) benefit from the formation of heterojunctions, which effectively degrade pollutants. The photocatalytic activities of the optimal sample for tetracycline (TC) and ofloxacin (OFL) degradation efficiency reached almost 99.1% and 94.66% under visible-light irradiation, respectively. It is mainly because the addition of BN not only provided more active sites for the catalyst but also improved the separation efficiency of electron-hole pairs. It can be found that h+ and center dot O2- played a major role in the degradation process through the active species quenching experiment. Furthermore, the possible photocatalytic degradation pathways of TC were revealed by analyzing intermediates and a reasonable photocatalytic mechanism was proposed. Moreover, Bi2WO6/BN heterojunctions were endowed with excellent recycling and stability. Therefore, this research illustrated that two dimensions/two dimensions (2D/2D) Bi2WO6/BN heterojunction may hold a great prospect for the degradation of antibiotics in wastewater. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：We have investigated the effect of In/Ga ratio on InGaN waveguide layers obtained by the epitaxial growth, and analyzed their physical mechanisms in detail. It is found that enhancing the In/Ga ratio by increasing the TMIn flux and reducing the TEGa flux can alleviate the decrease of In composition in InGaN waveguide. Moreover, the intensity of the yellow band of the photoluminescence is obviously reduced due to the reduction of the residual carbon impurity concentration. The smaller scattering of injected carriers by impurities and defects is beneficial for enhancing the hole concentration in the p-type layer. Meanwhile, the results of Raman spectroscopy clarify that InGaN waveguide layers grown with larger In/Ga ratio can achieve higher carrier mobility and lower resistivity. Therefore, properly increasing the In/Ga ratio during the growth can effectively improve the crystal quality of InGaN waveguide layers, which facilitates the obtaining of high-performance GaN-based laser diodes. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：The thermal deformation behavior and flow stress modeling of a novel CoNi-based wrought superalloy after forging was investigated at gamma' sub-solvus temperature (1050 degrees C and 1075 degrees C) and gamma' super-solvus temperature (1100 degrees C and 1125 degrees C) with strain rate range from 0.001 s-1 to 0.1 s-1 under a 50% strain. Scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscope (TEM) techniques were used to characterize the microstructures and explain the flow behavior. The results show that the flow stress increases with decreasing temperature and increasing strain rate. Dynamic recrystallization (DRX) occurs under all deformation conditions. When the alloy was deformed sub-solvusly at 1075 degrees C/0.01 s-1 and 0.001 s-1 conditions, the gamma' phase dissolved resulting in substantial grain growth. The constitutive equations were established via the flow stress data with the respect to the gamma' phase dissolution. The activation energies for the gamma + gamma' dual-phase region and the gamma single-phase region of the studied alloy are about 650 and 390 kJ/mol, respectively, which is comparable with traditional Ni-based superalloys. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：In this paper, the effect of pre-ageing treatment on the mechanical properties, microstructure, and fracture behavior of the extruded Mg-9.5Gd-4Y-2.2Zn-0.5Zr (wt%) alloys was studied. The results show that the poor mechanical properties of the solution-extruded (SE) sample with a bimodal microstructure are attributed to the deformation incompatibility between different regions (deformed grain region, fine grain region and bulk-shaped long period stacking ordered (LPSO) phases), which is prone to crack initiation and propagation. In contrast, pre-aged sample with various morphological phases (lamellar-shaped LPSO phases, granular-shaped beta phases and bulk-shaped LPSO phases) promotes the dynamic recrystallization (DRX) by the particle-stimulated nucleation (PSN) mechanism during extrusion, which results in the pre-aged-extruded (PE) sample having a more homogeneous microstructure with a finer and higher percentage of dynamically recrystallized grains. The densely distributed fine precipitates in the dynamically recrystallized region and homogeneous microstructure can enhance the capacity of the different regions to accommodate strain, and avoid premature fracture of the alloy without sufficient work hardening. Therefore, the PE sample has excellent strength-ductility synergy, and its yield strength (YS), ultimate tensile strength (UTS) and elongation (EL) were 408 MPa, 476 MPa and 8.3%, respectively. The YS and UTS of the PE sample after further ageing treatment (PEA sample) increased to 461 MPa and 535 MPa, respectively. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Multiple {10 (1) over bar2} twin variants can be activated when the external tension loading is parallel to the normal direction of magnesium alloy plate. In the current work, we report that in addition to abundant primary {10 (1) over bar2} twins, an atypical double twinning sequence, i.e. {10 (1) over bar2}{10 (1) over bar2} double twin can also occur during uniaxial loading. The results of electron backscatter diffraction (EBSD) observation indicate that these secondary twins prefer to be formed at the regions where two primary {10 (1) over bar} twins belonging to different twin variant pairs interact with each other. Meanwhile, abundant dislocations activated can also be found within the primary twin containing secondary {10 (1) over tilde2} twin. Accordingly, the possible formation mechanisms of such secondary {10 (1) over bar2} twin are proposed and discussed based on the local strain accommodation evaluated by a combination of geometrical compatibility parameter (m') and Schmid factor. The analysis results suggest that the formation of these secondary twins may be closely related to the minimization of local strain incompatibility at the twinning boundary caused by the basal dislocation within the primary twins. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：The composite (GQDs-MoS2/NSG) of molybdenum disulfide (MoS2) and N/S dual-doped graphene (NSG) has been successfully synthesized through in situ self-assembly by a new hydrothermal strategy using graphene quantum dots (GQDs) as auxiliary agent. The effect of GQDs dosage on the morphology of MoS2 has been investigated. Results show that adding GQDs to the nanohybrids can significantly improve the dispersion uniformity and binding state of MoS2 and NSG, and increase the overall defect density. When the GQDs dosage is 20 mg, the sample GQDs-MoS2/NSG20 has the best performance, and its specific capacitance reaches 564.3 .Fg(-1) at a scan rate of 10 .mV s(-1). Under a large current density of 20 .A g(-1), the specific capacitance retention rate of GQDs-MoS2/NSG20 is 92.8% after 10,000 constant current charge/discharge loops. The contribution of the pseudocapacitance of GQDs-MoS2/NSG20 at 10-200 mV.s(-1) was studied by using dynamic analysis and density functional theory calculation. All-solid-state asymmetric supercapacitor (ASC) was fabricated with NSG and GQDs-MoS2/NSG20. When the power density is 900 W.kg(-1), the energy density reaches 68.8 Wh.kg(-1). At a current density of 20 A.g(-1), the specific capacitance retention rate is 92.2% after 10000 constant current charge/discharge loops. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：The development of current technology imposes more and more requirements for measurement techniques, where one of the most important is temperature measurement. In recent years, non-contact optical thermometry based on fluorescence intensity ratio (FIR) technique has received tremendous attention in inorganic compounds for its promising applications in the electromagnetic field, micro-temperature field and thermally harsh environments. In this work, the current advancement of optical thermometry is reviewed in detail. Herein, the FIR thermometers are classified into two types: thermally coupled levels (TCLs) and non-TCLs based on the different energy level pairs. We investigate the relationship between the absolute sensitivity S-a and relative sensitivity S-r, temperature T and energy difference increment E based on the TCLs of lanthanide ions. The most important results obtained in each case are summarized, which indicates that some new strategies can extend the temperature operating range, improve the sensitivity and enhance signal discriminability. It is expected that this review will provide important guidance in exploring novel FIR optical thermometry with excellent properties in the future. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：A novel ternary g-C3N4 coupling with TiO2 and alpha-Fe2O3 composed magnetic nanocomposite was fabricated by facile calcination and hydrothermal process. The chemical, surface and magnetic characterizations of as obtained g-C3N4/TiO2/alpha-Fe2O3 magnetic nanocomposite was explored by various analytical systems. The superior degradation efficiency of magnetic g-C3N4/TiO2/alpha-Fe2O3 ternary nanocomposite is about 95.7% of Rhodamine B (RhB) in 50 min under visible-light exposure. The photocatalytic upgrading performance was recognized to the synergetic interface among TiO2, g-C3N4 and alpha-Fe2O3, with effective separation of electron/hole (e(-)/h(+)) pair's, increases in the redox species and great visible-light exploitation owing to less bandgap. The scavenging species presented in superoxide (.O-2(-)) radicals and photo-holes (h(+)) were played a substantial part and hence establish the Z-scheme RhB dye photo-degradation mechanism. The magnetic gC(3)N(4)/TiO2/alpha-Fe2O3 ternary PCs still maintain the excellent photo-degradation rate (95.7-88.4%) for the RhB dye aqueous solution after five consecutive recycles, which signifies that the great photocatalyst durability, and is more beneficial for wastewater treatment. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：This work aims at depositing high-crystallinity NiOx nanoparticles on the surface of graphitic carbon nitride (g-CN) nanosheets to improve light-driven hydrogen (H-2) generation. Notably, assisted by transmission electron microscopy (TEM), we can discover that the solvothermal-processed NiOx nanoparticles attached over g-CN possess a great crystallinity with a diameter size of approx. 3-5 nm. As a result, the NiOx-nanoparticle loading can obviously enhance the H-2 evolution rate (HER) of g-CN from 0 to 307 mu Mol h(-1) g(-1) under irradiation of AM1.5 spectra. Meanwhile, the apparent quantum efficiencies (AQE) at 400 nm can even approach the superior 1.5%. What's more, X-ray photoelectron spectroscopy (XPS) and transient ab- sorption (TA) spectra contribute to propose that the photogenerated electrons can first reduce Ni3+ into metallic nickel (Ni-0), and then the H+ prefers to be reduced on the surface of Ni2+/Ni-0 sites. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：In this study, we fabricated TiO2 nanorod arrays (TiO2), which were decorated with AgVO3 quantum dots (QDs) on and a layer of V2O5 film, forming a heterojunction material for removal pollutants and photo-electrochemical (PEC) water splitting. The AgVO3/V2O5-TiO2 nanorod arrays (AgVO3/V2O5-TiO2) synthesized by the secondary hydrothermal method were grown on conductive glass to form one-dimensional (1D) nanorod and p-n junction structures. Through experimental characterisation and testing, optical, mor-phological photocatalysis and PEC characteristics of the materials were measured and studied. The TiO2 modified with AgVO3 and V2O5 can significantly improve the visible light optical absorption, the reduce the electron-hole pair binding rate and shorten the band gap (3.07-1.41 eV) of TiO2. The resulting photocurrent density (116 uA/cm(2)) and photodegradation efficiency (rate constant, k = 0.025 min(-1)) of AgVO3/V2O5-TiO2 are approximately 20 (6 uA/cm(2)) and 5 times (0.005 min(-1)) higher than those of bare TiO2, respectively. The AgVO3/V2O5-TiO2 achieved a current density of 10 mA at an overpotential of 246.2 mV and exhibited ex-cellent oxygen evolution reaction (OER) performance. The systematic PEC experiments concluded that the optimized of the TiO2 interface by AgVO3 and V2O5 could promote the separation and transport of charge carriers. (C) 2021 Published by Elsevier B.V.
NSTL
Elsevier