查看更多>>摘要：The martensitic transformation in dilute Fe-Ni alloys was firstly investigated by using a composition gradient in the range from 0 to 31 mass% Ni. The current study exhibited the transformation of austenite to equiaxed or acicular ferrite at lower Ni contents can be suppressed and lath martensite can form. The electron backscattered diffraction results showed Ni has important effect on misorientation distribution in martensite. With the increase of Ni content up to similar to 27.5 mass%, the misorientation distributions above 15 degrees increased, and a peak at around 7 degrees gradually disappeared. With the further increase of Ni content, two peaks between about 50 degrees and 60 degrees at low Ni contents changed into three peaks at high Ni contents and a new peak at around 17 degrees arose due to formation of plate martensite. Moreover, it was observed that both block and sub-block was refined with increasing Ni content. Moreover, the micro-hardness/strength of martensitic Fe-Ni alloys between previous works and this work and the micro-hardness of martensite between Fe-C and Fe-Ni alloys were compared and discussed. (C) 2017 Elsevier B.V. All rights reserved.
查看更多>>摘要：Platinum-rare earth metal (Pt-RE) nanoalloys are the most promising candidates for fuel cells because of their superior activity and stability for oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). However, the preparation of Pt-RE nanoalloys with chemical method is still challenge due to their huge standard reduction potential differences and the oxophilicity of the latter. Herein, this work provides a novel and facile strategy for the chemical synthesis of Pt5La nanoalloys to apply in both ORR and MOR. Pt5La nanoalloys are synthesized by co-reduction of Pt2+ and La3+ in LaCl3 and H2PtCl6 solution containing carbon powder and C2H4N4 by first heating at 550 degrees C for 2 h under N-2, and then heating to 700 degrees C under H-2/Ar for 2 h. The as-synthesized Pt5La nanoalloys present a high alloying degree at 700 degrees C, with the average particle size of 7.8 nm. The results indicate Pt5La nanoalloys lead to a significant enhancement in ORR and MOR performances related to the commercial JM-Pt/C catalyst. (C) 2021 Published by Elsevier B.V.
查看更多>>摘要：Doping non-metal atoms into transition metal oxides (TMO) is considered as an effective method to improve the catalytic performance of TMO. Nevertheless, it is actually not easy to achieve efficient non-metal doping in TMO. To address this issue, herein, we for the first time put forwards an oxygen vacancy (V-o) assisted doping strategy to achieve high non-metal atoms doping amount in TMO. Firstly, V-o is produced by simple acid etching treatment on pristine Co3O4, and then the obtained V-o decorated Co3O4 (Co3O4-V-o) is used as precursor to conduct P doping. By systematical characterizations and analysis, it is found that the as-formed V-o in Co3O4-V-o plays a role of doping sites, which bring about efficient P doping effect. Even at relatively low temperature, the as-prepared P-doped Co3O4-V-o (P-Co3O4-V-o) is evidenced to display a high P doping amount of 6.1 wt%, which is much higher than that (1.9 wt%) of directly P-doped Co3O4 (P-Co3O4). Consequently, P-doped Co3O4-V-o shows significantly enhanced activity towards oxygen evolution reaction (OER). Clearly, this work opens a new avenue to efficiently doping non-metal atoms into TMO. (C) 2021 Published by Elsevier B.V.
查看更多>>摘要：Coherent grain boundaries (CGBs) has been revealed to improve the hardness and toughness simultaneously, but the density are not enough to increase their mechanical properties. Herein, hetero-interfaces are formed by introducing ion bombardment during magnetron sputtering to increase the amount of CGBs in the CrN coatings. By optimizing the sub-layer thickness, the quantity and width of CGBs from the (111) to (200) orientations increase significantly and consequently, the hardness and toughness of the CrN coating increase to 33.4 GPa and 14.98 MPa m(1/2), respectively. At last, the effect of the different CGBs to the coating strengthen is discussed. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Developing high-temperature microwave absorption (MA) materials remains a challenge in the field of radar stealth. Here, we propose a design concept of meta-structure for temperature-insensitive and broadband MA. The three-phase TiB2/Al2O3/MgAl2O4 composites are prepared to realize the temperature-insensitive MA properties, which is ascribed to the interaction of different components in terms of the electrical conductivity, dipolar polarization and interfacial polarization as temperature increases. On this basis, we design and fabricate a three-layer meta-structure composed of the SiO2 ceramics as environmental adaptation layer, the patch-type and flat composites as MA layers. Compared with flat composites, the meta-structure can optimize its effective permittivity, thereby realizing enhanced MA properties at elevated temperatures. This meta-structure can realize a reflection loss (RL) less than -5 dB at 8.2-18.0 GHz in the temperature range of 25 degrees C to 1100 degrees C. The experiment matches well with the simulation. The temperature-insensitive and enhanced MA properties are attributed to the consequence of the combination of traditional absorbing materials and metamaterial structures. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：YPO4 modified Ni-rich cathode materials LiNi0.8Co0.1Mn0.1O2 (NCM811) are favourably synthesized via a traditional high temperature solid-state method. Herein, the structure as well as thermal stability are promoted through the synergistic effect of Y3+ doping and LiYO2- Li3PO4 dual surface modification. The results turn out to solve the lattice structure defects, Li+ migration issue and, most of all, residual lithium issue. The most effective sample exhibits extraordinary 96.35% capacity retention with the initial specific discharge capacity of 186.1 mAh g-1 at 4.4 V cut-off voltage, 1 C, 25 degrees C after 100 cycles. Moreover, after 0.5, 1, 2, 4, 8 C cycling periods, at the time when the rate back to 0.5 C, the capacity of the YPO4 modified samples remain almost the same as the first 0.5 C cycles. It obviously can be seen that the YPO4 modification in this work is no doubt a promising strategy to optimize the manufacturing of cathode materials in Li-ion bat-teries field. (c) 2021 Published by Elsevier B.V.
查看更多>>摘要：Low abundance, high cost and corrosiveness towards the liquid electrolyte is the main limitation of Platinum (Pt) as a counter electrode (CE) in dye-sensitized solar cells (DSSCs) in spite of its excellent electrochemical properties. The present study focuses to enhance the electrochemical properties of CZTS by compositing it with MoS2 towards the replacement of Pt. Pure CZTS, pure MoS2, CZTS/MoS2 nanocomposites are synthesized by hydrothermal method, then characterized and compared to analyze their properties. The outcomes of characterizations techniques from XRD, Raman, XPS, SEM, EDS and TEM confirmed the for-mation of CZTS/MoS2 nanocomposites. The electrochemical characterizations and Impedance analysis of the pure CZTS, pure MoS2 and CZTS/MoS2 are compared. Results showed enhanced catalytic property and lower charge transfer resistance for the CZTS/MoS2 nanocomposites. Nanocomposite with 8 wt% of MoS2 in CZTS exhibited higher carrier concentration of 6.126 x 1018 cm-3, higher mobility of 5.03 cm2Vs-1 and lower resistivity of 2.62 Omega cm compared to CZTS and other nanocomposites. Electrical conductivity and catalytic activity were improved with increase in the wt% of MoS2 in the Cu2ZnSnS4/MoS2 nanocomposites. DSSC device fabricated by interpolating di-tetrabutylammonium cis-bis(isothiocyanate)bis(2,2 ''-bipyridyl- 4,4 ' dicarboxylato) ruthenium (II) (N719) dye-loaded titanium dioxide (commercial P25 TiO2 as photoanode) and with CZMo8 (as CE) using iodine/iodide as a liquid electrolyte exhibited the maximum open circuit voltage of 720 mV, a short circuit current of 8.45 mA/cm2, a fill factor of 0.66, and a power conversion efficiency of 4.07%. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：It was an effective strategy to improve photocatalytic degradation performance by constructing step-scheme (S-scheme) heterojunction photocatalysts with superior photo-redox capacity and high charge transfer efficiency. In this study, two-dimensional/two-dimensional (2D/2D) S-scheme g-C3N4/ZnIn2S4 (CN/ZIS) heterojunction with different mass ratios were synthesized by the hydrothermal method. Transmission electron microscopy (TEM) analysis showed that ZnIn2S4 nanosheets with an average size of similar to 20 nm were coupled on the surface of ultra-thin graphitic carbon nitrogen (g-C3N4) nanosheets, which can effectively increase the contact area. UV-vis diffuse reflectance spectra (DRS), Photoluminescence spectra (PL) and photochemical tests showed that CN/ZIS had strong visible light absorption ability and photo-generated carriers transfer ability. Under visible light irradiation, CN/ZIS-10 degraded 93.41% of tetracycline (TC), which was 1.38 times than that of pristine g-C3N4. Moreover, the photocatalytic activity of CN/ZIS-10 was almost no change after five cycles. The S-scheme mechanism of CN/ZIS-10 was explored through electron spin response (ESR) and capture experiments of active species. In conclusion, this work provided a reasonable example for the construction of g-C3N4-based S-scheme heterojunction. (C) 2021 Published by Elsevier B.V.
查看更多>>摘要：ZnO based heterostructures with metal chalcogenides have gained enormous attention in photonic applications owing to their high absorption coefficient and high photo-response. Several studies have been carried out on ZnO-based photodetectors. In present work, simple facile hydrothermal route was opted for synthesis of ZnO-ZnSe heterostructures. The as-prepared heterostructures were characterized by PXRD, TEM and UV-vis spectroscopy. PXRD showed that there is lattice shrinkage of the ZnO after the heterostructure formation with ZnSe. The DRS and UV-vis data revealed a Type II band alignment of ZnO and ZnSe in the heterostructure which results in the slower recombination of electron-hole pairs after illumination of light. ZnO-ZnSe heterostructures showed wide range absorption spectra and expected to have better photogenerated charge carrier's life time, which will be ideal for the fabrication of photo-detector. The ZnO-ZnSe heterostructures based photodetector produced a fast rise and decay time of 23 and 80 ms; and a high photo-responsivity (91.25 mAW(-1)) indicating importance of ZnO-ZnSe heterostructures for high performance photodetectors. This work demonstrates the instant photo-response with high photo-responsivity which proves it as a potential candidate for optoelectronic devices. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：The microstructural evolutions and properties variations of a CuCrZrY alloy processed by equal channel angular pressing (ECAP) with different passes were studied systematically. After 4 passes of ECAP, the average grain size was decreased to 500 nm, and the grain size distribution became more uniform during the subsequent processing. After 8 passes ECAP-ed and aged at 400 degrees C for 7 h, the samples' tensile strength and electrical conductivity are 560 MPa and 86.4%IACS. The main strengthening mechanisms are precipitation strengthening, low-angle grain boundary strengthening, and high-angle grain boundary strengthening (about 82% in total). Finite element simulation was carried out through ABAQUS to obtain the equivalent strain distribution diagram of ECAP, resulting in that the strain force of the outer region was less than that of the inner one. The inconsistency of deformation leads to the inhomogeneity of microstructure. These findings will effectively guide researchers to develop high-strength high-electrical conductivity copper alloys. (c) 2021 Published by Elsevier B.V.
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