查看更多>>摘要：? 2022 Elsevier B.V.Cobalt-nitrogen-doped carbon (Co-N-C) materials are regarded as promising candidates to replace Pt-based catalysts for oxygen reduction reaction (ORR). Introducing Zn species with a small electronegativity to form Co/Zn-N-C catalysts could promote the electron transfer and enhance the ORR activity. Herein, we report Zn-anchored Co nanoparticles encapsulated in porous N-doped carbon ((Zn, Co)/NC) derived from Zn/Co-ZIF-67. Compared with the catalyst without Zn, (Zn, Co)/NC exhibits higher ORR catalytic activities in alkaline and acidic media with outstanding methanol tolerance and stability. The assembled Zn-air battery used (Zn, Co)/NC presents higher peak power density (186 mW·cm?2) and specific capacity (807 mAh·g?1) than those of Pt/C. The density functional theory (DFT) calculations demonstrate Zn atoms on Co NPs induce more charges transfer from inner metal NPs to carbon shell, leading to more charges accumulation around N-C active sites to activate O2 and reducing the energy barrier of (Zn, Co)/NC for ORR.
查看更多>>摘要：? 2022 Elsevier B.V.Titanium and titanium alloys have been widely used as biomedical materials as a result of low density, high specific strength, good biological propertise, good mechanical compatibility and easy processing. However, problems such as stress shielding and bacterial infection often occur in the clinical application. In this paper, Ti-15Mo-xAg (x = 10, 12) alloys were designed and prepared to obtain low elastic modulus and excellent antibacterial ability. We studied the microstructure, mechanical properties, antibacterial properties and cytocompatibility by scanning electron microscopy, differential scanning calorimeter, X-ray diffraction, micro-hardness instrument and plate counting method. The calculated results indicated that Ti-15Mo alloys with different Ag contents could be β-type or near β-type alloy with potential of a low elastic modulus. Microstructure results demonstrated that the increasing Ag content from 10 wt% to 12 wt% increased the phase transformation temperature and resisted the formation of ω phase in Ti-Mo-Ag system. Both the elastic modulus and the antibacterial ability were significantly influenced by the ageing treatment and Ag content due to the phase constitution, and high Ag content and the precipitation of Ti2Ag were beneficial to the antibacterial performance but increased the elastic modulus. Cell assessment showed that Ti-Mo-Ag alloys did not have cytotoxicity to MC3T3. Ti-15Mo-10Ag alloy exhibited strong antibacterial rate of 99.5%, good cellular compatibility and low elastic modulus of 85 GPa, which suggests that this alloy might be a highly competitive medical material.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, the effect of trace addition of Ag on the microstructure, tensile strength, and fracture toughness of novel Al-Mg-Zn alloys was evaluated using transmission electron microscopy, scanning electron microscopy, electron back-scattered diffraction analysis, tensile test, and Khan tear test. The age-hardening response was improved by Ag owing to the stimulation of matrix precipitation. The type of MPts was unchanged by Ag, and the density and size of MPts were improved and refined. But the ability of matrix precipitates (MPts) to obstruct dislocation motion was weakened by Ag, thus, the Al-Mg-Zn alloys strength was not improved by Ag as expected. The addition of 0.2 wt% Ag improved the fracture toughness, while the addition of 0.4 wt% and 0.6 wt% Ag decreased the fracture toughness of Al-Mg-Zn alloys. The fracture toughness results are based on many factors such as MPts, misorientation of grain boundaries, fraction of deformed grains, and stress-strain concentration. The mechanism of the effect of microstructure on properties was also elucidated.
查看更多>>摘要：? 2022 Elsevier B.V.A Z-scheme MoS2/Ag2S/AgVOx ternary heterostructure was successfully synthesized by a facile hydrothermal method. The as-prepared MoS2/Ag2S/AgVOx ternary composite has been characterized by electron microscopy, XRD, XPS, UV-Vis DRS, PL, electrochemistry and ESR. TEM characterization revealed that Ag2S, Ag nanoparticles and AgVOx nanorods were dispersed homogeneously over the surface of MoS2 nanosheets The prepared heterojunction showed enhanced photocatalytic performance compared with single MoS2 and AgVOx. And 6%-MoS2/Ag2S/AgVOx heterojunction exhibits highest photocatalytic degradation efficiency, which can degrade fuchsine around 75% under visible light within 180 min. The enhanced photocatalytic activity can be attributed to the efficient separation of photogenerated charge carriers, the strong redox ability and enhancement of visible-light absorption derived from the construction of Z-scheme heterostructure. In-situ formed metallic Ag2S act as the electron mediator and Ag nanoparticles possess the surface plasmon resonance (SPR) effect. The prepared heterojunction showed decreased photoluminescence and increased photoelectrochemical performance, indicating high separation rate of photoinduced charge carriers. Furthermore, a possible degradation mechanism of fuchsine solution was proposed. And the results of radical trapping experiments indicated that superoxide radicals (?O2-) and holes (h+) play major role during the photocatalytic degradation process. This work demonstrates an interesting Z-scheme photocatalytic system for photocatalysis applications.
查看更多>>摘要：? 2022 Elsevier B.V.Hematite (α-Fe2O3) as a photoanode material has attracted widespread attention in photoelectrochemical (PEC) water oxidation reaction. However, its performance is still impeded by the severe recombination of photogenerated charges in the bulk photoanode and at the photoanode/electrolyte interface. Herein, we have fabricated an integrated photoanode consisted of Ti doped α-Fe2O3 (Ti-Fe2O3), carbon quantum dots (CQDs) and NiFe layered double hydroxide (NiFe-LDH), aiming at improving the injection efficiency as well as the separation efficiency. The results demonstrate the appearance of CQDs in NiFe-LDH/C/Ti-Fe2O3 improves the photogenerated hole extraction from Ti-Fe2O3 to NiFe-LDH, while NiFe-LDH as a cocatalyst guarantees the rapid transfer of photogenerated holes at the photoanode/electrolyte interface. Under the synergistic effect of CQDs and NiFe-LDH, NiFe-LDH/C/Ti-Fe2O3 exhibits a stable photocurrent density of 2.89 mA/cm2 at 1.23 V vs. RHE, which is much higher than that of Ti-Fe2O3.
查看更多>>摘要：? 2022 Elsevier B.V.Magnetic ternary composites Bi4O5Br2/Bi4O5I2/Fe3O4 (BBF) were constructed by the combination of exotic Fe3O4 nanoparticles and Bi4O5Br2/Bi4O5I2 with controllable molar ratios of Br to I through a facile one-pot route. Microstructural, morphological, and optical features of achieved composites were thoroughly characterized by a succession of analytical techniques. It was realized that three expected components were coexisted to form efficient heterojunction structures. These magnetic composites showed reinforced photocatalytic removal of bisphenol A (BPA) under visible light illumination. Particularly, the best candidate BBF(3:7) possessed the largest apparent reaction rate constant of 0.041 min?1 that was respectively about 1.95, 372.73, 4.71, 39.42, and 3.72 times those of Bi4O5I2/Fe3O4, Bi4O5Br2/Fe3O4, Bi4O5I2, Bi4O5Br2, and BB(3:7), mainly attributed to the strengthened visible-light absorption by the shrinkage of band gaps, the harmony of various morphologies, the suitable phase composition, and the promoted segregation of charge carriers by ternary heterojunctions with proper band structures. In addition, a possible photocatalysis mechanism was proposed by entrapping experiments and band structures estimation. The sufficient reusability by recycling experiments together with enhanced photocatalytic outcome ensured these magnetic composites as potential and applicable candidates in fields of environmental protection and energy reservation.
查看更多>>摘要：? 2022 Elsevier B.V.Recently, cobalt (II, III) oxide (Co3O4) is considered as an alternative anode material for high-performance LIBs because of its high safety and theoretical capacity (890 mAh g?1). However, Co3O4 anode materials suffer from low conductivity and poor cycle life due to structural strain and huge volume change during lithiation/delithiation processes. In this work, porous N-doped graphitic carbon encapsulated Co3O4 structure (Co3O4 @PNGC) was synthesized by using mixed Zn and Co metal-organic frameworks templates (ZIF-67/ZIF-8) and coated with polydopamine as a nitrogen and carbon source. During the synthesis, Zn species was evaporated to form the structural pores, and the in-situ formation of Co(0) occurred that served as a catalyst in the graphitization of the carbon matrix. The Co3O4/PNGC exhibited an improved discharge capacity of 847.4 mAh g?1 after 500 cycles at 1 C when compared to the bare sample.
查看更多>>摘要：? 2022 Elsevier B.V.The flow behaviors and microstructural evolutions during multi-stage hot deformation are essential aspects in the processing of high performance titanium alloys. In the present work, both isothermal multi-stage deformation (IMD) and non-isothermal multi-stage deformation (NMD) over α + β and single β phase regions were employed to study the constitutive behaviors and microstructural evolutions of a near-α Ti-5Al-2.5Sn alloy. The results showed that the flow stress, restoration fraction in α + β phase region of NMD were lower than that of IMD, because that the predominant lamellar microstructures formed during NMD increased α/β boundaries and thereby promoted grain boundaries gliding. In β phase region, the flow behaviors showed slight differences with temperature and deformation passes during both IMD and NMD processes. Clear transitions were observed from the mean flow stress between different phase regions during NMD. In addition, an obvious α + β→β dynamic phase transformation occurred during deformation at 990 °C, which was identified to be a displacive nucleation and diffusion-controlled growth process. In addition, numerous FCC-Ti precipitations were observed during IMD at 960 °C and strain rate of 1 s?1 with the orientation relationship of (0 0 0 1)HCP matrix //{1 1 1}FCC.
查看更多>>摘要：? 2022 Elsevier B.V.SnSe is an emerging star material in thermoelectric community owing to its attractive electronic band structure and ultralow intrinsic lattice thermal conductivity. By now, aliovalent doping is often employed to be a route strategy to optimize the thermoelectric properties of SnSe via improving its poor electrical conductivity. In this work, AgSnSe2, as a metallic composite, is introduced with the aim to increase the hole concentration of SnSe via metal-semiconductor contact. It is demonstrated that compositing of AgSnSe2 can effectively increase the hole concentration of polycrystalline SnSe hosts by two orders of magnitude (from 1017 to 1019 cm?3) without deteriorating the carrier mobilities. Therefore, a lager power factor of 5.72 μW cm?1 K?2 is achieved at 773 K for the SnSe + 0.020AgSnSe2 sample perpendicular to the hot-pressing direction. Combined with the intrinsic low thermal conductivity, the maximum zT value of the sample can be boosted to 0.68 at 773 K, which is increased by 124% compared to that of the uncomposited counterpart. This work proves that composite engineering should be an efficient alternative strategy in optimizing the thermoelectric performance of polycrystalline SnSe and can be synergistically used with other sophisticated approaches.
查看更多>>摘要：? 2022 Elsevier B.V.Ce3+ ions (2 mol%) doped KY3F10 (Ce: KYF) single crystals were successfully grown by the vertical Bridgman method in a vacuum system. Ce3+: KYF single crystal had high crystalline quality and transmittance, and the absorption edge was significantly red shifted compared with undoped KYF. The broad band emission centered at 360 nm (λex = 300 nm) were both observed in them, while a three-fold increased emission intensity was seen when Ce3+ ions were doped. Ce: KYF crystal possessed high UV luminous efficiency due to converting the light of a 265 nm chip to its luminescence effectively. It was a surprise that Ce: KYF crystal exhibited stable zero-thermal quenching property in the UV band which covered a wide temperature range from 298 K to 573 K. The possible mechanism of the luminescent properties and the superior thermal stability of Ce: KYF was discussed. Ce: KYF single crystal will have good application prospect as an excellent UV luminescent material with high thermal stability.
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