查看更多>>摘要：The construction of Fe_2O_3/Fe_2TiO_5 heterostructure has been proven as an effective strategy to improve the photoconversion efficiency of hematite, however its controllable synthesis is still a great challenge. In this study, by performing a comparative investigation on two distinct Ti precursors, a novel, convenient, and low-cost approach for fabricating efficient Fe_2O_3/Fe_2TiO_5 photoanodes is developed. It clearly demonstrates that the adoption of typical TiCl_4 precursor leads to a Fe_2O_3/TiO_2 composite with a lower PEC activity, while a core-shell Fe_2O_3/Fe_2TiO_5 heterostructure is built via using the stable and water-soluble peroxo-titanium complex (PTC) precursor. The as-fabricated photoanode exhibits a comparable photocurrent density of 2.51 mA/cm~2 at 1.23 V vs. RHE to most of Fe_2O_3/Fe_2TiO_5 photoanodes in literatures. Based on various characterizations, the significant enhancement in PEC performance can be attributed to the largely increased donor density and the formation of Fe_2O_3/Fe_2TiO_5 core-shell heterostructure, which effectively facilitate the charge separation and transport in the bulk and surface of photoanode. This work provides a new idea for fabricating high-efficient Fe_2O_3/Fe_2TiO_5 photoanodes.
查看更多>>摘要：The ductility of the Al alloys produced by additive manufacturing (AM) has become a critical property, as the AM Al alloys are increasingly used in the automotive industry. However, the ductility of as-built AM Al alloys is relatively low, even with optimized AM conditions. The post-annealing treatment provides an efficient way to improve ductility. Previous investigation has shown that the annealed AM AlSi3.5Mg2.5 alloy possesses superior ductility. However, the plastic deformation micro-mechanisms of the annealed AM AlSi3.5Mg2.5 alloy remain unclear. In this study, in-situ neutron diffraction was employed to explore the annealed AM AlSi3.5Mg2.5 alloy. The evolutions of phase stresses, dislocation density, and crystallite size in the annealed AM AlSi3.5Mg2.5 alloy during tensile deformation were analyzed. The experimental investigation reveals that the dislocation density in the Al matrix of the annealed AM AlSi3.5Mg2.5 alloy increases slowly in the early plastic deformation stage, and it reaches a saturated level upon the following uniform deformation. The crystallite size decreases quickly in the early deformation stage, and then it decreases slowly. The Kocks-Mecking model and the Voce model can capture the strain hardening behavior well. The determined physical constitutive equations can be applied in continuum mechanical computer simulations.
查看更多>>摘要：A comparative study on the structure and photocatalytic activity of halo-aggregated and differently connected ZrO_2@TiO_2 and TiO_2@ZrO_2 nanocomposites was investigated here towards photodegradation of Alizarin yellow GG model azo dye. The nanocomposites were synthesized by two-step sol-gel method with predominant monoclinic phase for ZrO_2, anatase phase for TiO_2, and characterized through different structural and spectroscopy tools. The photocatalysts with high adsorption capability were however differing in their photodegradation efficiency attributed to varying preferential binding at their interfaces and Zr~(4+) substitution in the TiO_2 lattice. Between the two nanocomposites, superior photocatalytic property was shown by ZrO_2@TiO_2 exhibiting 90-93% degradation efficiency with reproducibility. The growth of titania over zirconia in ZrO_2@TiO_2 reduced the surface states and defects of the core nanocrystal (NC) through strong Zr-O-Ti binding, besides providing shallow traps in smaller TiO_2 NCs that enhanced the separation of photogenerated carriers. The process was also assisted through trapping of holes by surface OH groups on ZrO_2 reducing the carrier migration to TiO_2. The type I heterojunction had favorable positive and negative potentials for valence and conduction bands in ZrO_2 and TiO_2 compared to intermediate superoxide anion and hydroxyl radical generation potentials that catapulted the dye degradation. The interfacial contact in TiO_2@ZrO_2 nanocomposite on the other hand, has been very weak as understood from their absorption and photoluminescence spectra resulting in poorer degradation efficiency. Alizarin yellow GG being a prominent textile azo dye and there are not many reports on its photodegradation, the study also assumes significance in the context of sunlight driven photocatalysis and environmental remediation.
查看更多>>摘要：Antiferromagnetic pyrite compound MnTe_2 is a newly discovered high-performance thermoelectric material. However, its electric and thermal transport performance remained unexplored so far. In this work, the first-principle calculations based on the density functional theory were applied to predict the electric and thermal transport performance of MnTe_2. The band structures showed that Te atoms dominate the band energies near the fermi level. The calculated electric transport performance of MnTe_2 from BoltzTraP2 package showed that n-type MnTe_2 possesses a higher power factor than that of p-type in the carrier concentration range from 10~(19) to 10~(21) cm~(-3). The peak power factor with electronic relaxation time of n-type MnTe_2 at 800 K is 3.05 x 10~(15) μW K~2 cm~(-1) s~(-1) at a lower carrier concentration of 0.78 × 10~(21) cm~(-3) while p-type is 2.18 × 10~(15) μW K~(-2) cm~(-1) s~(-1) at a higher carrier concentration of 1.35 × 10~(21) cm~(-3) It suggests that high-performance n-type doped MnTe_2 is easier to be obtained experimentally. Due to the low average phonon velocity of 2064 m-s~(-1), MnTe_2 has a low lattice thermal conductivity of 0.72 W m~(-1) K~(-1) at 800 K. The calculated charged point defect formation energy of several possible n-type doping elements showed that Y or La substituting Mn atom and Cl or Br substituting Te atom are the most possible n-type doping point defects. Combined with the optimal carrier concentration of 0.78 x 10~(21) cm~(-3)at 800 K, stoichiometric A_(0.07)Mn_(0.93)Te_2 (A = Y, La) and MnTe-1.93B0.07 (B = Cl, Br) are expected to possess high thermoelectric properties reaching the theoretical peak power factor with electronic relaxation time of 3.05× 10~(15) μW K~(-2) cm~(-1) s~(-1) and the lattice thermal conductivity of 0.72 W m~(-1) K~(-1).
查看更多>>摘要：For applications involving sodium-ion capacitor (SIC) with high energy and high power, it is necessary to develop cathode materials with high operating voltage, high capacity, and excellent cyclic stability. Prussian blue and its analogs are considered promising candidates for cathode materials owing to their high energy and high stability resulting from their open framework structure. We demonstrate that the Prussian blue-graphene oxide composite (PBGO) can be applied to SIC as a battery-type cathode. PBGO is synthesized by a single-step decomposition method and has a morphology in which graphene oxide covered Prussian blue, which has a uniform cubic structure. PBGO exhibit a high capacity of 165 mAh g~(-1) at 20 mA g~(-1), as well as 68 mAh g~(-1) at a high current density of 4 A g~(-1). The SIC is fabricated using PBGO as the cathode materials and activated carbon (AC) as a capacitor-type anode, and it exhibit a high specific energy density of 65.3 Wh kg~(-1) and a superior capacity retention of 78.8% after 10,000 cycles. The use of battery-type cathodes presents a promising strategy for developing SIC with high energy and long lifespan.
Kirill A. CherednichenkoVladimir A. MukhanovAleksandr Kalinko
8页
查看更多>>摘要：Two boron-rich chalcogenides B_(12)S and B_(12)Se isostructural to a-rhombohedral boron were synthesized by chemical reaction of the elements at high-pressure - high-temperature conditions. The crystal structures and stoichiometries of both compounds were confirmed by Rietveld refinement of synchrotron X-ray diffraction data and elemental analysis. The experimental Raman spectra of B_(12)S and B_(12)Se were investigated for the first time. All observed Raman bands have been attributed to the theoretically calculated phonon modes, and the mode assignment has been performed.
查看更多>>摘要：Transition metal oxides have achieved tremendous attention in the field of supercapacitor devices due to their outstanding structural properties and capacitive behavior. Herein, a porous a-MoO_3 microspheres (A-SMO) were synthesized with the aid of CrCl_3.6H_2O via a facile hydrothermal reaction and subsequent annealing treatment. The results showed that CrCl_3.6H_2O plays a crucial role in manipulating morphology and increasing the specific surface area of the as-prepared products. Moreover, annealing treatment could transform the crystal structure from metastable hexagonal M0O_3 to stable orthogonal MoO_3, which is more beneficial for electron storage due to the layered crystal structure. Furthermore, the A-SMO displayed an excellent specific capacitance of 201.4 F g~(-1) compared with the pristine MoO_3 (MO) of 62.0 F g~(-1) and the annealed MO (A-MO) of 186.5 F g~(-1) at 0.2 A g~(-1), when they were directly served as supercapacitor electrodes. This research demonstrates that the as-obtained a-MoO_3 microspheres can serve as promising electrode materials for supercapacitors.
查看更多>>摘要：The promising quaternary chalcogenide Cu_2Fe_(1-x)In_xSnS_4 (where x = 0 -0.25 -0.50 -0.75 and 1) thin films were grown using spray pyrolysis technique. The behaviors of indium inclusion on chemical composition, morphological, structural, optical and electrical properties have been investigated using respectively: Energy dispersive X-ray spectrometry (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), Maud software, Raman spectroscopy, spectrophotometer and Hall Effect. XRD and Maud software revealed a formation of stannite Cu_2InSnS_4 (x = 1) named CITS from stannite Cu_2FeSnS_4 (x = 0) called CFTS with same preferred orientation (112) plan. Identification of chalcogenide CITS was supported from chemical composition ratio of Cu:In:Sn:S, which are near to theoretical values 2:1:1:4. Electrical resistivity was increased slightly from 5.82 10~(-3) (for CFTS) to 5.94 10~(-3) D.cm (for CITS). This trend may be due to the decrement of crystallite sizes. The energy band gap of CITS was equal to 1.4 eV. These optical and electrical behaviors favorite Cu_2InSnS_4 thin film to be implicate as an absorber material in solar cell applications. Furthermore, this work highlights the surface wettability of Cu_2Fe_(1-x)In_xSnS_4 thin films showing a conversion from hy-drophilic CFTS surface into hydrophobic CITS surface. In addition, photocatalytic activity of Cu_2InSnS_4/SnO_2:F (CITS-FTO) heterojunction has been investigated under Xenon light irradiation using methylene blue (MB) and methyl orange (MO) as representatives pollutant dyes. Moreover, MB dye was continuously degraded during four cycles, meaning that CITS-FTO photocatalyst has relatively good stability in MB degradation. Therefore, this work provides an opportunity for a new successful removal candidate CITS-FTO of water contaminants for photocatalytic applications and new absorber CITS material for photovoltaic applications.
查看更多>>摘要：Electromagnetic interference (EMI) shielding materials with great absorption effectiveness is highly required in certain application field such as stealth technology but is hard to be realized by conventional metallic shielding materials. In this work, a graphene nanosheets (GNSs) reinforced magnesium (Mg) matrix composite was fabricated by spray deposition and subsequent hot-press sintering. The micro-structure, mechanical properties and EMI shielding effectiveness of the GNSs/Mg composites were characterized systematically. The results showed that synergistic strengthening of mechanical properties and EMI shielding performance of the composites was realized. The strengthening mechanisms on the mechanical and EMI shielding performance of the GNSs/Mg composites were analyzed thoroughly. It was found that the incorporated GNSs reinforced the composites mainly by load transfer and thermal expansion mismatch strengthening. Moreover, the propagation path of electromagnetic waves in the composites is extended by the GNSs, and the GNSs induced laminar structure and thus resulting in an increased electromagnetic absorption effectiveness. The obtained results in this work revealed the synergistic strengthening mechanisms by the laminated structure and provided a novel method to fabricate GNSs/Mg composites with superior mechanical and EMI shielding performance.
查看更多>>摘要：There are numerous defect states in the anatase TiO_2 nanoparticles, which are most frequently used as the electron transporting layers in perovskite solar cells (PSCs), resulting in severe charge recombination and poor electron extracted efficiency. Herein, we report a simple and practical way to passivate the surface defects of TiO_2 by hydrothermal treating with acetic acid and H_2SO_4. Modified TiO_2 with a high percentage of {101} facets and sulfonic acid functional group is proved to be beneficial for the growth and crystallization of FAMA perovskite film. Furthermore, it can facilitate the electron extraction and inhibit the charge recombination at the perovskite-TiO_2 interface. A high PCE of 20.27% has been achieved in our modified TiO_2-based PSCs, which is 30% higher than that of control devices under the same condition. Simultaneously, the solar cells display negligible hysteresis, improved device reproducibility and stability. This work provides an efficient approach to engineer the electron transport pathway at perovskite-TiO_2 interface.
NSTL
Elsevier