查看更多>>摘要：Understanding the underlying transport mechanism of photogenerated carriers is crucial in designing active heterojunctions in the field of photocatalysis. In this study, the redox activity of Graphene quantum dots/TiO2 (GQDs/TiO2) hybrid was investigated through water treatment under visible light irradiation. The corresponding findings showed that the charge transfer between GQDs and TiO2 accompanied with oxygen vacancy (Vo) was expedited, resulting in enhanced redox activity in the Cr (VI) and RhB co-removing system. Further investigation revealed that Vo introduced a defect level in TiO2 just below its conduction band that could induce visible light excitation while leading to quick charge separation and effective transmission from GQDs to TiO2. Therefore, carrying out photocatalytic Cr (VI) reduction and RhB degradation synchronously over GQDs/TiO2 can roughly enhance 2 and 3 times pure TiO2 nanosheets under visible light irradiation. The findings of this study may provide novel insight into heterojunction engineering and defect level controlling in order to attain efficient photocatalyst and offer additional prospects for photocatalytic applications.
查看更多>>摘要：As a new zero-carbon energy with high calorific value, hydrogen has attracted extensive attention in recent years. In this work, multiwalled carbon nanotubes modified molybdenum sulfide and molybdenum oxide heterostructure (MWCNTs-MoS2-MoO3) was obtained via a simple hydrothermal method. The low band gap of 0.02MWCNTs-MoS2-MoO3 (1.15 eV) endowed a good near-infrared (NIR) light response. The conduction band position of 0.02MWCNTs-MoS2-MoO3 (?0.63 V vs. reversible hydrogen electrode (RHE)) was negative enough to produce hydrogen. Compared with pure MoS2, the formation of MoS2-MoO3 heterostructure and introduction of MWCNTs generated better photoelectrochemical activity and NIR irradiation improved photoelectrocatalytic (PEC) hydrogen evolution performance in wide pH range. The 0.02MWCNTs-MoS2-MoO3 had superior overpotential (68 mV @ 10 mA cm?2) and Tafel slope (56 mV dec?1) in acidic media. The NIR improved PEC hydrogen evolution activity of 0.02MWCNTs-MoS2-MoO3 in acidic media could be explained by Volmer-Heyrovsky mechanism. The presence of large amount of bridging S22? in 1 T/2 H phase MoS2 and the synergistic effect between MWCNTs and MoS2-MoO3 heterostructure made a joint effect on the photoelectrocatalytic hydrogen evolution reaction (HER). NIR irradiation could increase the charge transport rate. The introduction of MWCNTs and heterostructure formation could increase the charge transport rate and improve the electron and hole separation ability of 0.02MWCNTs-MoS2-MoO3 as well.
查看更多>>摘要：The intermetallic compounds are very interesting in a multitude of structural and functional applications, such as in turbomachines or engine parts, due to their good behaviour at high temperatures, as well as their high resistance to corrosion and oxidation. In the present work, the study of processing of the Ni-Al system intermetallics has been carried out by means of Self-Propagating High–Temperature Synthesis initiated by concentrated solar energy (SHS–CSE). Synthesis by this high-energy exothermic reaction often causes the appearance of porosity, lack of interlayer adhesion, volumetric expansion, and even the total loss of sample shape. To obtain high-quality systems, a study has been carried out on one-layer and multi-layer configurations from powder materials, considering the influence of the heating rate and time. The use of concentrated solar energy has allowed to obtain fully densified nickel parts at 1000 °C in just 15 min, compared to the 1325 °C and more than 12 h required by conventional techniques to obtain lower relative densities (~97%). The best results in multilayer configurations have been achieved in Ni-Ni/Al-Ni system with the synthesis of intermetallic compounds type Ni2Al3, NiAl and Ni3Al. The control of volumetric expansion and porosity, full densified nickel layers perfectly adhered to the interlayer and hardness values up to 900 HV have been obtained in just 2 min. This work highlights the wide possibilities of the use of CSE in metal treatment, which allows efficient and sustainable synthesis of new systems and the improvement of the final properties of the parts.
查看更多>>摘要：Antibiotics contaminants gradually evolve into one of widely concerned public safety events and attract numerous investigations. In this work, hybrid AgI@Ag3PO4 nanostructures were designed and synthesized for visible-light photodegradation of norfloxacin via facile self-assembly formation strategy method. The well mixed anions here induced good interface contacts and the formation of AgI@Ag3PO4 nanostructures. The experimental results indicated that nanostructured AgI@Ag3PO4 composites showed highly enhanced visible-light photocatalytic performance, and the AgI@Ag3PO4-15 sample presented the best visible-light photocatalytic performance, which was far better than that of pristine AgI and 2.96 times of pristine Ag3PO4. These findings were mainly attributed to construction of heterostructure structures between AgI and Ag3PO4 as well as the surface plasmon resonance effects of the generated Ag nanoparticles. Besides, the main active species, possible visible-light photodegradation pathways, and visible-light photocatalytic mechanism were also proposed in detail. Current work indicates an efficient and promising visible-light composite photocatalyst for emerging pollutants degradation.
查看更多>>摘要：A series of single-phase color-adjustable Sr3MgSi2O8:Eu3+,2Tb3+ phosphors were synthesized with the application of sol-gel method. The crystal structure, luminescence characteristics, fluorescence lifetime, energy transfer mechanism and thermal stability of phosphors were investigated. The results show that the emission spectrum of Sr3?x?yMgSi2O8:xEu3+,yTb3+ compose both the 5D4→7F5 transition of Tb3+ and the 5D0→7F1, 5D0→7F2 transition of Eu3+ at the excitation wavelength of 238 nm. The optimal doping concentration of Tb3+ was determined to be 2% when concentration quenching effect was comprehensively considered. On the basis of the energy transfer of Tb3+→Eu3+, the emission peak intensity of Eu3+ increases and that of Tb3+ decreases with the rising Eu3+ concentration. The unidirectional energy transfer efficiency of Tb3+→Eu3+ reaches 89.4% when the Eu3+ doping concentration is 8%. On the basis of Dexter's theory, the major mechanism of energy transfer lies in the electric dipoles interaction between Tb3+ and Eu3+. With an activation energy of 0.309 eV, Sr2.95MgSi2O8:3%Eu3+,2%Tb3+ phosphors enjoys good thermal stability. Its color coordinate diagram indicates that the luminous colors of phosphors can be customized from red to orange, then to green with the changing doping concentrations of Eu3+ and Tb3+. Based on Sr3MgSi2O8:Eu3+,Tb3+ phosphors has a good matchability with ultraviolet and near-ultraviolet LED chips, so it can be considered that Sr3MgSi2O8:Eu3+,Tb3+ phosphors have good application potential in the field of ultraviolet and near-ultraviolet white light emitting diodes.
查看更多>>摘要：The low depolarization temperature has hindered implementation of (Na1/2Bi1/2)TiO3 (NBT)-based lead-free piezoceramics in practical application, in particular, in high temperature environment. In this work, the impact of Fe modification on the microstructure, depolarization temperature, ferroelectric and piezoelectric properties of 0.94(Na1/2Bi1/2)TiO3-0.06BaTiO3 (NBT-6BT) lead-free ceramics were studied. The results illustrates that the piezoelectric constant and depolarization temperature can be significantly tuned by Fe doping, and more importantly, both can be simultaneously enhanced. Compared to the undoped material, the room-temperature piezoelectric constant of NBT-6BT with 1.0 mol% Fe doping increases from 133 pC/N to 164 pC/N, and the depolarization temperature increases from 106 °C to 125 °C. These observations are mainly attributed to the stabilization of ferroelectric order, induced by the enhanced lattice distortion.
查看更多>>摘要：The intrinsic brittleness of tungsten limits the improvement on the comprehensive mechanical properties of tungsten alloys. Starting from the perspective of solid solution toughening, this study innovatively used tungsten-tantalum particles instead of tungsten particles as the sintered core to prepare 90(W-Ta)-Ni-Fe alloy. Tantalum forms a BCC solid solution with tungsten in the process of high-energy ball milling. During the vacuum sintering process, tantalum precipitated and reacted with the matrix to form acicular phase. This precipitation process reduces the liquid phase sintering temperature of the tungsten alloy and refine the tungsten particles. The microstructure of the sintered alloy is composed of tungsten particles, matrix phase, intermediate phase, acicular precipitated phase and oxides. The solid solution of tantalum increases the hardness and reduces the modulus of the tungsten particles. The hardness and modulus of the matrix phase are increased due to the influence of the acicular precipitation phase. These findings indicate that the solid solution of tantalum has the potential to improve the comprehensive mechanical properties of tungsten heavy alloys.
查看更多>>摘要：Inspired by the nanostructured graphene-based membranes for ionic sieving, an ion-oriented interface of few-layer graphene (FLG) was rationally constructed to achieve long-life zinc (Zn) metal anode. The ion-oriented interface increased the nucleation sites and inhibited localized dendrite growth, which aided the uniform transmission of Zn ions. Moreover, the fewer oxygen-containing functional groups on the FLG surface demonstrated a lower energy barrier of ion transport and a stronger Zn ion-regulating function. The FLG@Zn anode exhibited a much larger capacity with significant stability in the cycling behavior against MnO2 cathode compared to the pristine Zn anode. Specifically, a nearly 97% capacity retention was achieved for FLG@Zn/MnO2 battery after 5000 cycles at 10 A·g–1. Our work provides a novel approach to the fabrication of high-performance Zn anode for ultra-stable aqueous batteries.
查看更多>>摘要：Photolysis in multiferroic nanoferrites has wide-ranging applications in resolution of the environmental issues and actuators. In the current study, we examine the consequence of Sm3+ (x = 0.04 (S1), 0.08 (S2), 0.12 (S3) & 0.16 (S4)) substitution on catalysis and energy storage density of Bi1?xSmxFeO3 (BSFO). The BSFO nanoferrites were characterized via XRD (X-ray Diffraction), FESEM (Field Emission Scanning Electron microscopy) with EDS, UV–visible spectroscopy, AC Impedance Analyzer, VSM (Vibrating Spin Magnetometer), photon driven catalysis for MB dye degradation and polarization behavior (P-E). The photo-catalytic degradation efficiencies were increased from 49.90% to 80.78% with the substitution of Sm3+. The energy storage density and efficiency increases from 4.415 to 6.324 mJ/cm3, 42–61%, respectively. As well, the magnetic and ferroelectric curves were also traced, and the saturation magnetization (Ms) and saturation polarization (Ps) values were found to be increased from 0.529 to 1.221 emu/gm and 0.726–1.208 μC/Cm2, respectively, as extensively manipulated via Sm3+ substitution.
查看更多>>摘要：Photocatalytic technology has been attracting considerable attention due to its low cost and environmental friendly properties. In this work, a novel ZnO/Ag2MoO4/Ag (ZAA) nanocomposite was prepared by an ultrasonic-irradiation method as an efficient visible-light-driven photocatalyst. The structure and photocatalytic property of the photocatalyst were studied by XRD, SEM, FTIR, XPS, TEM, UV–vis DRS and PL Spectroscopy, respectively. The results indicated that the Ag2MoO4 nanocomposites were successfully decorated on the ZnO sheets which grabbed Ag NPs. Benefiting from local surface plasmon resonance effect of metallic silver and the formation of heterojunctions between the counterparts of ZnO and Ag2MoO4, it effectively suppresses recombination of photogenerated charge carriers, which can enhance good photocatalytic properties and antibacterial activities. An optimal photocatalysis of ZAA with molar ratio of ZnO to Ag2MoO4 at 40:1 performed the highest degradation rate for rhodamine B under visible light irradiation. In addition, over 99.999% of Gram-negative E. coli and 99.846% of Gram-positive S. aureus were reduced by ZAA-40 nanocomposites within 60 min in comparison to pure ZnO sheet. These results demonstrate that ZAA is a promising photocatalyst, making it a prospective strategy to overcome current challengers in the use of organic pollutant degradation and the photocatalytic antibacterial area.
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Elsevier