查看更多>>摘要：? 2022 Elsevier B.V.The aim of this work is to investigate the hydrogen sorption kinetics and thermodynamics of Mg-Ni nanoparticles at relatively low temperature in relation to their microstructure. To this purpose, Mg-Ni nanoparticles (20 at% Ni) were prepared by gas phase condensation employing two thermal vapour sources. In the as-prepared state, Mg and Ni are mixed within individual nanoparticles, but the intermetallic Mg2Ni compound is not fully formed. After keeping the nanoparticles at 150 °C for two hours under high vacuum or at a mild hydrogen pressure of 0.15 bar, the formation of a Mg-Mg2Ni or MgH2-Mg2NiH0.3 nanocomposite is observed. Subsequently, fast kinetics of hydrogen sorption are recorded at 150 °C with activation energy of 80±8 kJ/mol (absorption) and 60±6 kJ/mol (desorption). However, the maximum hydrogen storage capacity is limited to 2.5 wt% because the transformation from Mg2NiH0.3 to Mg2NiH4 does not take place at 150 °C even at pressures well above the expected thermodynamic equilibrium. Therefore, only the transformation Mg?MgH2 contributes to the reversible storage capacity. The corresponding equilibrium pressure determined by pressure-composition isotherms of absorption and desorption at 150 °C is 7.5 mbar, very close to the extrapolated value for bulk Mg. The partial replacement of Ni with Fe does not significantly alter the thermodynamics and kinetics of hydrogen sorption. The structure and hydrogen sorption properties of Mg-Ni nanoparticles are compared to those of Mg-Ti nanoparticles prepared by a similar procedure.
查看更多>>摘要：? 2022 Elsevier B.V.The β-Al4.5FeSi phase occurs as plate-shaped particles in secondary, i. e. recycled, Fe-containing hypoeutectic Al-Si alloys and as a component of the intermetallic reaction layer between Al-Si alloys and steels joints. Unsolved issues of the structure interpretation with consequences at all microstructural scales are addressed based on experimental results and new theoretical evidence from DFT calculations. On top of the previously described polytypism (AB and ABCD polytypes, where the letters refer to the positions of a certain type of double layers perpendicular to the stacking direction), ordering of Al vs. Si atoms adds a further aspect of structural variability. Thus, three different ordered crystal structures of β-Al4.5FeSi with different ordering of Al vs. Si atoms and different stacking sequences (AB or ABCD) could be encountered in the same alloy. The two AB structures can be described in space groups A12/a1 with (DFT-base) lattice parameters a = 6.1667 ?, b = 6.1683 ?, c = 20.779 ? and β = 91.51° and A21/e11 with lattice parameters a = 6.1739 ?, b = 6.1602 ?, c = 20.7840 ? and α = 88.63°. The third structure has ABCD stacking. Unit cell distortions away from a pseudotetragonal orthorhombic metric comply with the symmetry are shown to be induced by the ordering of Al vs. Si atoms. Frequently observed δ-like stacking sequences are discussed as consequence of excess Si in β-Al4.5FeSi. Furthermore, recommendation is given for optimal experimental conditions for the characterization of the type of order and polytype in β-Al4.5FeSi.
查看更多>>摘要：? 2022 Elsevier B.V.Metals with nanometer-sized grains are strong but often suffer from poor thermal stability. Herein, nanolaminated (NL) structure with an average thickness of 110 nm and a low angle grain boundaries (LAGBs) fraction of 80% was obtained in an Al-1Mn (in wt%) alloy produced by high strain rate deformation at cryogenic temperature. The NL structures are thermally stable up to 523 K, which can effectively suppress GB precipitation during aging, thus improving the pitting corrosion resistance in 0.6 M NaCl solution. The high thermal stability of NL structures can be mainly attributed to the formation of a large fraction (80%) of LAGBs.
查看更多>>摘要：? 2022 Elsevier B.V.Crystal structures of U3Rh4Ge13 [structure type HT-Y3Pt4Ge13, space group R3c, a = 5.6004(6) ?, c = 15.5158(1) ?, RB = 0.022, Rp = 0.021] and of Th2Rh3Ge5 [structure type U2Co3Si5, space group Ibam, a = 10.0572(1) ?, b = 11.9142(1) ?, c = 6.0997(1) ?, RB = 0.027, RP = 0.037] are refined by powder X-ray diffraction method. Their structural relationships with primitive cubic Yb3Rh4Sn13 and body-centered tetragonal ThCr2Si2 types, respectively are discussed. The ac and dc magnetic susceptibility measurements on U3Rh4Ge13 revealed an antiferromagnetic ordering at TN = 22 K followed by a metamagnetic transition below 5 K. The magnetic entropy Smag ≈ Rln4 at TN indicates U3Rh4Ge13 to follow the classical LS coupling scheme. This finding together with the performed theoretical DFT calculations hint toward localized nature of 5f states in the studied germanide. U3Rh4Ge13 reveals metallic transport properties, low thermal conductivity (i.e. 0.4–0.6 W m?1 K?1) as well as displays a structural phase transition in the temperature range of 292–315 K. Electrical resistivity measurements and theoretical DFT calculations indicated Th2Rh3Ge5 to be a simple metal.
查看更多>>摘要：? 2022 Elsevier B.V.Bismuth (Bi)-based photocatalysts were successfully prepared by the metathesis-assisted molten salts process by a straightforward, efficient, high-yield, and environmentally friendly novel methodology. The catalysts preparation in an in-situ generated molten LiNO3/NaNO3 reaction media has no precedent. Different loads of graphene (G), and silver nanoparticles (Ag-NPs) added to the catalysts affected phases composition, physicochemical characteristics, and photocatalytic performance. The as-prepared catalysts showed plate-like shapes with heterogeneous lateral length and nanometric thickness. Methylene blue (MB), Rhodamine (RhB) dyes and binary solutions (MB + RhB) were used to estimate the photocatalytic activity of the as-prepared Bi-based catalysts. Pristine Bi2WO6 (BWO) catalyst enhanced the degradation of RhB (%XRhB) achieving 100% within 60 min using a low-power (19 W) UV-A LED source. This %XRhB is superior to those reported in the literature, considering the rated power consumption-to-degradation efficiency. MB and RhB degradation over BWO and Ag/Bi2WO6 (Ag/BWO) were substantially influenced by the catalyst dosage, dyes initial concentration, and solution pH. Trapping tests revealed that h+ is the main oxidative species causing MB, and RhB photodegradation, and the degradation mechanism was postulated based on these findings. After the fourth reuse cycle, BWO showed high chemical stability (%XRhB = 100%). In binary solutions (RhB + MB), the RhB photodegradation was significantly diminished (%XRhB = 19%) over BWO and entirely hindered (%XRhB = 0%) using Ag/BWO since the active sites on the catalysts’ surface showed greater affinity towards the MB molecule.
查看更多>>摘要：? 2022 Elsevier B.V.Lead-free (1-x)[(Bi0.5Na0.5)0.94Ba0.06TiO3]-xAgNbO3 (abbreviated as BNTBT-100xAN) ceramics were fabricated using a conventional solid-phase reaction technique. The effect of the antiferroelectric AgNbO3 dopants for fatigue resistance, energy-storage density, temperature-stable permittivity, and conductivity mechanism was systematically investigated. The addition of AgNbO3 led to the decrease of remnant polarization and the increase of dielectric breakdown strength, a large effective energy-storage density of ~1.27 J/cm3 corresponding to the conversion efficiency of ~ 77.5% for BNTBT-5AN ceramic were attained under applied 105 kV/cm field. Meanwhile, it exhibited an outstanding fatigue-resistant performance at 70 kV/cm fixed field up to 105 cycles accompanied with excellent temperature-stable properties in the temperature range of 30 °C ~ 120 °C. Besides, BNTBT-5AN sample has also obtained outstanding temperature-stable permittivity, which was associated with the enhancement of the ergodic relaxor domain structure. A little variance of dielectric content (Δε'/ε'150 °C ≤ ± 15%) was acquired from 40 °C to 387 °C with a small tangent loss (tanδ ≤ 0.05) between 50 °C and 461 °C. Hence, it revealed that the high energy storage properties and excellent dielectric temperature stability for BNTBT-5AN ceramic were conducive to its better applications in electronic equipment.
查看更多>>摘要：? 2022 Elsevier B.V.The rational fabrication of an efficient photocatalyst with optimal interface engineering remains a huge challenge for the enhancement of photocatalytic perpformance. Herein, a sequence of multidimensional nanocomposites with different spatial interfaces, including point, and line or face-contact surface are controllable designed by horizontal growing diverse dimensional (0D, 1D,2D and 3D) copper sulfide (CuS) on 2D graphitic-carbon nitride (g-C3N4) nanosheets. Physical and photochemical measurements demonstrate that the formation of an extraordinary 2D/2D face-to-face contact interface can not only enhance the specific surface area, visible light utilization, and photo-excited charge separation efficiency, but also elevate the density and lifetime of photo-generated carriers. The results of ultraviolet photoemission spectroscopy (UPS) and density functional theory (DFT) calculation also confirm that charge transfer tends to occur in face-to-face contact. Among the types of nanocomposites considered, 2D/2D g-C3N4/CuS has the smallest electron transfer barrier (ФBe) between active species, thereby displaying the maximum photocatalytic apparent rate constant, which is about 12 times larger than that of pristine g-C3N4. Most importantly, this work systematically investigates the relationship between microscopic interface structure and photocatalytic activity from the perspective of the optical, and electrical and energy levels, providing a new insight on the rational design of desired interface engineering towards efficient photocatalysts.
查看更多>>摘要：? 2022 Elsevier B.V.The effect of the pulse induced current on the mechanical properties and microstructure of the 7075-T6 aluminum alloy was thoroughly studied by transmission electron microscopy, X-ray diffraction, and electron backscattered diffraction measurements. The experimental results demonstrated that the strength of the alloy decreases slightly, whereas the elongation increases significantly. On top of that, after the application of the induced electro-pulsing treatment, the dislocation density of the alloy decreases, while the grain size and the second phase particles grow slightly. In addition, the induced current also causes the Cube, Copper and S textures to decrease. On the other hand, the Goss texture is enhanced. The current density and the local temperature distribution of the sample were simulated by employing the ANSYS software. From the acquired outcomes, we can draw the conclusion that the recorded changes in the mechanical properties and microstructure of our sample can be attributed to the combination of the joule phenomenon and the pure electric effects of the current. The Joule heat and current increase the vacancy concentration and diffusion coefficient of solute atoms and promote dislocation recovery, precipitation phase growth, and grain rotation.
查看更多>>摘要：? 2022 Elsevier B.V.Pesticide residues lead to increasingly serious harmful ecological environment, which poses tremendous threats on human health. To overcome this problem, researchers are focusing on the development of highly efficient composites with excellent photocatalytic efficiency. In this work, a new C/ZnO/BiOI photocatalyst was successfully synthesized using hydrothermal, hydrolysis and ultrasonic technique for carbaryl degradation. The as-prepared photocatalyst was characterized by XRD, FT-IR, XPS, SEM, TEM, BET, UV–vis DRS and PL. The photocatalyst exhibited better carbaryl removal performances than that of ZnO, C/ZnO and ZnO/BiOI under simulated sunlight irradiation, which might be attributed to the efficient electron-hole separation and wider region of light response. The optimum C/ZnO/BiOI (20%) composite exhibited the highest degradation efficiency (62.9%) of carbaryl and excellent cycling stability. Reactive species scavenging and ESR experiments illustrated that .OH was the most important active species. Furthermore, the identification of intermediates revealed possible degradation pathways of carbaryl.
查看更多>>摘要：? 2022Ternary materials have gained great popularity in the field of solar-blind ultraviolet (UV) photodetectors due to their diverse band gaps. Whereas, quality problems brought by lattice damage and phase separation appear frequently during preparation, which greatly limit the application of ternary solar-blind photoresponsive materials. MgTiO3 (MTO), a ceramic material, has extensive application in microwave capacitors and dielectric resonators but takes no place in the field of photodetectors. Faced with this situation, this study investigates the effect of annealing on the structure of MTO thin film, and fabricates a solar-blind UV detector through combining MTO with graphene, which expands the application of ternary compound MTO to the field of photodetectors. Under solar-blind UV illumination, this MTO-based detector exhibits excellent performance with an open circuit voltage as high as 1.7 V. At 0 V bias, the detector exhibits an ultrafast response speed with the rise and decay time as short as 30 ms and 25 ms, respectively. Besides, a responsivity up to 46.5 mA/W, an external quantum efficiency (EQE) up to 20.4%, and a specific detectivity (D*) up to 6.14 × 1011 Jones also prove the great performance this detector owns. All the results achieved in this work not only suggest the great potential of MTO in being applied to fabricating solar-blind UV detectors, but also provide some guidance for the development of photovoltaic detectors based on other ternary semiconductor materials.
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