查看更多>>摘要：The effects of fibrous Cr phase on the adiabatic shearing anisotropic behavior of the Cu-15Cr in-situ composite model alloy were firstly studied by a split Hopkinson pressure bar (SHPB), Optical Microscope (OM), and X-ray diffraction (XRD) technique. Specimens were loaded along the rolling direction (Cu-15Cr0 degrees) and perpendicular to the rolling direction (Cu-15Cr-90 degrees). The experimental and analysis results showed that there were differences in the number of phase interfaces and phase interface distance that the shear stress crossed when sheared along with different directions due to the directional arrangement of the fibrous Cr phases, which caused the strain hardening, strain rate hardening and thermal softening of the Cu15Cr in-situ composite were anisotropic. The Cu-15Cr-90 degrees specimen possessed lower strain rate hardening and higher thermal softening at the same strain rate, and the strain hardening rate was similar to that of the Cu-15Cr-0 degrees specimen as the shearing process proceeded, so the Cu-15Cr-90 degrees specimen was more prone to adiabatic shearing than the Cu-15Cr-0 degrees specimen. In addition, a splitting crack was produced at the Cr phase and matrix interface in the Cu-15Cr-0 degrees specimen due to the additional tensile stress produced in the Cr phase during shearing. The perpendicular Cr phase in the Cu-15Cr-90 degrees specimen was deflected parallel to the shear stress during shearing, so it was not easy to produce splitting cracks. However, the tip of the Cr phase without deflection was more likely to possess high additional tensile stress, so the crack in the Cu15Cr-90 degrees specimen was extended along the edge of the adiabatic shear region at the tip of the Cr phase. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Through site selective substitution engineering, the (Ba2Ca)(1-2x)/3Bi(x)B(2)Si(4)O(14)(BCBSO: xBi(3+)) phosphors were prepared by high-temperature solid-phase synthesis. BCBSO: xBi(3+) phosphors show two obvious emission peaks at 330 and 500 nm, which are derived from the Bi3+ ions occupying Ba and Ca sites, respectively. The emission of the BCBSO: xBi(3+) phosphors is tunable by varying the Bi3+ content. Through XRD and XPS, the crystal structure and element composition of the samples have been determined. The emission and decay curves confirm that the two emissions come from different luminescent centers. The two emission bands of the BCBSO: Bi3+ phosphor have distinctive thermal responses to temperatures. The Sm3+ ion activated BCBSO phosphor has a bright emission mainly at 601 nm. The temperature-dependent emission of BCBSO: 0.08Bi(3+), 0.1Sm(3+) indicates an optical thermometer which is designed with high relative sensitivity at 510 K (S-r = 2.3206% K-1). (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：In this study, flame-made Rh-doped SnO2/electrochemically exfoliated graphene hybrid materials were developed and systematically investigated for gas sensing towards H2S. Structural characterizations by various microscopic and spectroscopic techniques demonstrated the dispersion of graphene sheets on Rhsubstituted polycrystalline SnO2 nanoparticles with improved specific surface area. The effects of Rh dopants and graphene on gas-sensing behaviors of the hybrid sensors were systematically evaluated towards H2S, H2, CH4, C2H2, C2H4, CH3SH, CO2, C2H5OH, C3H6O and NO2 at 200-400 degrees C in dry and humidified air with 20-80% RH. It was found that Rh doping at the optimal amount of 0.5 wt% considerably enhances the response and selectivity of flame-made SnO2 nanoparticles toward H2S and additional graphene loading further increases the H2S-sensing performance with the optimum graphene content of 0.5 wt%. Accordingly, the 0.5 wt% graphene-loaded 0.5 wt% Rh-doped SnO2 sensor provided the highest responses of similar to 439 and the shortest response time of 6.5 s to 10 ppm H2S with high selectivity against CH3SH, H2, CH4, C2H2, C2H4, CO2, C2H5OH, C3H6O and NO2 at the optimal working temperature of 350 degrees C. The mechanisms of H2S response enhancement were described by the combinative effects of catalytic p-type substitutional Rh dopants and active graphene-Rh-doped SnO2 junctions.
查看更多>>摘要：Rare-earth/alkaline-earth hexaborides with high chemical stability and low work function have recently attracted much interest as promising thermionic cathodes. Their synthesis at low temperatures without post-synthesis purification treatments is still a significant challenge. The present work demonstrates a simple synthesis technique to produce pure barium, cerium and gadolinium hexaborides (BaB6, CeB6, and GdB6). For each hexaboride, a batch of samples was created by first milling highly pure precursor powders and then firing at various temperatures in a low-vacuum furnace. The synthesised products were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron dispersive spectroscopy (EDS). Their thermionic properties were investigated utilising a Schottky device. Pure BaB6, CeB6, and GdB6 were successfully synthesised at lower temperatures (<= 1400 degrees C). Nanocrystalline CeB6 was found to be produced at the lowest temperature of 1200 degrees C. The mean particle size of pure CeB6 and GdB6 synthesised is seen to be in the sub-micron range, with the exception of large BaB6 particles. The estimated work functions of the BaB6, CeB6, and GdB6 cathodes are 1.61 +/- 0.18 eV, 2.50 +/- 0.09 eV, and 2.42 +/- 0.09 eV, respectively. These findings imply that hexaborides, as promising thermionic emitters, can be easily produced at low temperatures. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Valence electron concentration (VEC) was treated as a useful parameter to predict the stability of solid solution phases. However, the available experimental data to support this criterion is far from enough. In the current study, the high-throughput ab initio modeling is applied to investigate the relative stability of FCC and BCC single crystals of the Al-Co-Cr-Fe-Ni high entropy alloys (HEAs) by using the special quasi-random structure (SQS) approach. The predictions start with pure elements of the Al-Co-Cr-Fe-Ni system and are continued with binaries, ternaries, and quaternary compositions, which come up with 180 com-positions (360 structures). After that, the reliability of the VEC criterion is testified. The results show that the VEC criterion not only works for the stable structure but also works effectively for metastable structure when both FCC and BCC are not thermodynamic stable. However, it is found that the old VEC criterion proposed by Guo et al. fails to work effectively for compositions containing high concentrations of light-weight metals such as Al at VEC < 5. To solve this problem, the present work proposed a new VEC rule to define the stability of FCC and BCC structures at the ground state. With the implementation of the new VEC rule, the effectiveness of the VEC rule (EVEC) of both FCC and BCC structures is enhanced, especially for pure elements and binary compositions, indicating that this rule does not only work effectively for multi-component systems but also works for low-order systems.(c) 2022 Published by Elsevier B.V.
查看更多>>摘要：Three-dimensional (3D) printing is considered to its the ability to make complex structures with modified properties in functional materials. In this work, a planar multi-layer anode-supported solid oxide fuel cell (SOFC) is fabricated through slurry-based 3D printing. The composition of 65 wt% NiO-YSZ (60:40 wt %)-35 wt% graphite is selected for fabrication of anode support by pressing. The low viscosity slurry with good homogeneity is prepared for fabricating of anode functional layer (AFL) consisting of NiO-YSZ (50-50), electrolyte (YSZ), and cathode (LSM) layers. After sintering of layers, uniform hierarchical porous microstructures are obtained with interconnected large pores up several microns and smaller pores of 100 nm in the AFL and cathode layer. In meanwhile, the electrolyte layer is achieved a relatively dense microstructure. The maximum power density at the output voltage of 0.5 V is achieved at 0.84 W/cm2 at an open-circuit voltage (OCV) of 1.06 V at 800 degrees C with H2 gas as fuel. The results are shown that the hierarchically macromesopores can create higher power density. Also, modification of geometry such as thickness and structure of layers can be improved electrochemical performance. Furthermore, the OCV exhibited a few fuel leakage due to the relatively dense structure and crack-free electrolyte layer. (c) 2022 Elsevier B.V. All rights reserved.
Lazurenko, D. V.Petrov, I. Yu.Mali, V. I.Esikov, M. A....
13页
查看更多>>摘要：Ti-Al3Ti metal-intermetallic laminate (MIL) composites are known as promising structural materials due to the unique combination of their specific properties. However, their application is still limited due to the extremely high brittleness of the Al3Ti phase. In this study, we attempt to address this issue by changing the D022 crystal structure of Al3Ti to the more ductile L12 structure by alloying it with silver. To select the best fabrication regimes of Ti-Ti(Al1-xAgx)3 composites, in situ synchrotron X-ray diffraction analysis was performed to reveal the chemical reactions occurring upon heating the Ti-Al-Ag sample. The analysis showed that the highest amount of Ti(Al1-xAgx)3 phase with the L12 structure appears at 930 degrees C. This temperature was chosen for subsequent spark plasma sintering experiments. Scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction analysis revealed that the sintered sample consisted mainly of Ti, Ti(Al1-xAgx)3, and a minor fraction of the Ag-Al compound distributed in the central parts of the intermetallic layers and at the grain boundaries. Modification of the titanium trialuminide crystal structure positively affected the properties of the composite, providing a 60% increase in fracture toughness. The Ag-Al phase also contributed to toughening, causing an additional crack deflection effect. (c) 2022 Published by Elsevier B.V.
查看更多>>摘要：Magnetite and magnetite/ceria composites prepared by chemical procedures in various mutual ratios were exposed to calcination treatment in a temperature interval between 473 K and 1073 K. A combination of several experimental methods has provided detailed structural, phase, and magnetic properties utilisable for selection of optimal compositions and calcination conditions from the viewpoint of degradation ability tested using parathion methyl and paraoxon. It was shown that the ceria content, selected between 5 wt% and 50 wt%, influences magnetic properties. Its optimal amount was determined to be above 20 wt% and the calcination temperature of 773 K when the highest rate constant, slightly above 0.06 min-1, was obtained for parathion methyl in acetonitrile using a degradation test.
查看更多>>摘要：The effect of MnCO3 additions on crystal structure, grain growth behavior, and dielectric properties were studied in the La2O3-doped BaTiO3 system. La2O3-doped BaTiO3 powders were prepared by conventional solid-state reaction routes and then after the addition of MnCO3, the powder compacts were sintered at 1250 degrees C in air. The tetragonality (c/a) of the samples increased with the amount of up to 0.5 mol% MnCO3 and then decreased above 0.5 mol%. The 3D grain shape became more spherical polygons with increasing amounts of MnCO3. The grain growth behavior changed from suppressed growth to abnormal grain growth and finally normal grain growth with increasing amounts of MnCO3 when the powder compacts were sintered. The correlation between the grain growth behavior and the grain shape change is discussed from the perspective of two-dimensional nucleation grain growth theory. Further, the dielectric properties are discussed in terms of the crystal structure, microstructural control, and charge compensation. (c) 2022 Published by Elsevier B.V.
查看更多>>摘要：In this work, a facile chemical co-precipitation method to prepare nickel-cobalt layered double hydroxide (Ni, Co-LDH) is reported. Through the addition of NaHCO3, carbonate ions (CO32-) are introduced into the LDH in a controlled way. The doping of CO(3)(2- )causes the original nanosheet structure to bend and inter-connect, which increases the contact area between the electrode and the electrolyte, enhancing the energy storage characteristics of materials. Appropriate CO(3)(2- )doping effectively increases the specific capacity of Ni, Co-LDH. When the doping ratio of carbonate is 5% (Ni, Co-LDH/CO3-5%), the specific capacity is improved from 1432 F g(-1) (undoped) to 1970 F g(-1) at 1 A g(-1). Furthermore, the electrode exhibits satisfactory rate capability, retaining 82.8% of the specific capacity at 20 A g(-1). Moreover, an asymmetric supercapacitor (ASC), assembled with Ni, Co-LDH/CO3-5% as the positive electrode and activated carbon as the negative electrode, possesses a high energy density of 54.8 Wh kg(-1) at a power density of 374.9 W kg(-1) and remains 80.8% after 10000 cycles at 10 A g(-1), demonstrating excellent cyclic stability. (C) 2022 Elsevier B.V. All rights reserved.
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