查看更多>>摘要：Eutectic materials have been widely employed in many high-tech fields, and recently, eutectic high-entropy alloys (EHEAs) have become a research focus of eutectic materials; however, it is challenging to determine/ design the eutectic composition of alloys accurately, especially multi-component alloys and EHEAs. In this study, a new electromagnetic directional crystallization approach was proposed to determine/design eutectic alloy compositions. First, standard eutectic Al-Si, Al-Si-Fe, Al-Si-Ti, and Al-Si-Fe-Mn alloys were obtained by directly separating their respective melts using electromagnetic directional crystallization. Then their eutectic compositions were accurately determined by inductively coupled plasma-optical emission spectroscopy. Conflicting reports about the eutectic reactions and phase transformations occurring in the Al-Si-Ti system were also resolved. Thereafter, the application of electromagnetic directional crystallization was extended to EHEAs. The widely investigated AlCoCrFeNi2.1 EHEA was confirmed to have a eutectic composition, and a new EHEA Al16.8Co12.6Cr13.8Fe11.8Ni45.1 with a combination of high strength and high ductility was obtained in this study by separating the AlCoCrFeNi3 melt via electromagnetic directional crystallization. Therefore, in the absence of thermodynamic data, electromagnetic directional crystallization provides a promising approach for determining and designing the eutectic composition of alloys, especially EHEAs. This new approach is more direct, efficient, and simpler than the conventional thermodynamiccalculation approach because the application of the latter is significantly limited when thermodynamic data are not available.
查看更多>>摘要：In this article, we studied the magnetic and transport properties by magnetization, resistivity, and specific heat measurements for EuCu4As2 crystals with a rhombohedral structure. Strongly anisotropic magnetism and rich magnetic phases were observed under magnetic field in this compound. Interestingly, we observed two types of magnetoresistance: a large negative magnetoresistance (-55%, at 35 K, 9 T) near the magnetic transition temperature, due to reduction of magnetic scattering under magnetic field; a large positive magnetoresistance (60% at 2 K, 9 T) at lower temperatures when Eu2+ moments ordering ferromagnetically, similar to that observed in the non-magnetic isostructural analogue SrAg4As2 with possible nontrivial topological bands, which may be related to its special band structure.(c) 2022 Elsevier B.V. All rights reserved.
Makola, Lekgowa C.Moeno, SharonOuma, Cecil N. M.Sharma, Ajit...
15页
查看更多>>摘要：Clean energy production and environmental detoxification through photocatalysis have received wide-spread attention due to their efficiency and capability to address global energy and environmental related calamities. Moreover, graphitic carbon nitride (g-C3N4) and many other single-semiconductor based pho-tocatalysts have been widely explored; however, their performance is still unsatisfactory. Herein, the engineering of g-C3N4 as a primary photocatalyst interlayered with niobium carbide (Nb2CTx) MXene co-catalyst for the formation of efficient photo-responsive Schottky-heterojunction photocatalyst is demon-strated. Visible-light absorption of g-C3N4 is proportional to the Nb2CTx contents. Moreover, g-C3N4 energy bandgap was significantly lowered from 2.61 eV to 2.19, 2.08, and 2.32 eV for 1, 3, and 5 wt% of Nb2CTx loaded onto g-C3N4, respectively. Nb2CTx MXene as a co-catalyst allows a formation of an efficient photo-catalyst with high potential to eliminate the use of costly noble metals. The devised Schottky-junction restrained the electron recombination rates threefold relative to the pristine g-C3N4. The conduction band potential of g-C3N4 and the composites were observed to be more positive in relation to the standard reduction potential of O-2/center dot O-2- (-0.33 V) CO2/CO (-0.53 V), CO3N4 (-0.24 V), H-2/H+ (0.0 V), signifying its merits potentials for photocatalysis. The observed charge carriers with more negative reduction potential facilitates efficient photocatalytic reactions, particularly in hydrogen production and catalytic transforma-tion of carbon dioxide into useful sources of energy. Fabricating a heterostructure between g-C3N4 and Nb2CTx MXene demonstrates the feasibility of facile preparation of photocatalysts with merit features due to synergistic catalytic effects. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Blown-powder additive manufacturing process, directed energy deposition (DED) is applicable to scale-up material development with cost-effective elemental powder mixtures. In this paper, the effectiveness of applying DED to the design and synthesis of model CoCrFeNiTi high entropy alloys (HEAs) was demonstrated. Through a careful design of composition and delicate selection of particle size and shape, three CoCrFeNiTi HEAs with different microstructures were in-situ synthesized from premixed elemental powders. Transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction were used for microstructure characterization. H3-Co24.4Cr17.4Fe17.5Ni24.2Ti16.5 in at% (close to Co1.5CrFeNi1.5Ti) was fabricated with a soft face-centered cubic (FCC)-gamma phase structure while hard intermetallic phases such as sigma-FeCr, delta-NiTi2, and a small amount of Ni3Ti2 were precipitated and uniformed distributed in the FCC matrix for H1-Co22.2Cr16.1Fe19Ni21.8Ti20.9 and H2-Co25.9Cr15Fe17Ni20.8Ti21.3. With a large percent of the secondary phases, H1 exhibited a hardness value of about 853 HV0.5. These HEAs displayed a high oxidation resistance comparable to Inconel 625 superalloy. A detailed evaluation of the composition, microstructure, hardness, oxidation resistance, and wear resistance of these HEAs was conducted as compared with those of a reference HEA and two popular wear-resistant steels. (c) 2022 Elsevier B.V. All rights reserved.
Thi, Lan NguyenPhan, Thi Thuy TrangNgoc, Tri NguyenViswanath, N. S. M....
15页
查看更多>>摘要：To overcome the limitations in the reversibility of Fe2+/Fe3+ in the Fenton reaction, a reasonable concept of the addition of photoinduced electron donors has been developed. In this study, a facile solid-state reaction has been used to synthesize composites of Prussian Blue and g-C3N4 as an effective catalyst in the photo Fenton reaction for organic pollutants decomposition. As a result, the degradation efficiencies of Rhodamine B and Tetracycline under the photo-Fenton catalytic process are 94.1% and 84.3%, respectively, after 60 min of treatment. Therein, a step-scheme model of electron-hole transport accelerated by a built-in electric field was ascribed as the origin of the significant improvement in the catalytic performance of the composites. A reasonable pathway for charge carrier transfer was proposed and demonstrated by both experimental and calculation proofs. Furthermore, the theoretical calculation result indicates that the decomposition of H2O2 to hydroxyl radicals is preferable on Prussian Blue, while the g-C3N4 is considered an electron-generator. Additionally, the decomposition mechanism of organic pollutants under the photo-Fenton reaction of the composites was also investigated. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：A partially recrystallized sample of the Ni-based superalloy AD730 was taken from an intermediate stage of the ingot to billet conversion process and isothermally forged in a single stroke compression test at a subsolvus temperature (1080 degrees C). The as-received material had a heterogeneous microstructure, containing a mixture of coarse and much finer recrystallized grains as well as unrecrystallized ones, and also heterogeneous gamma ' precipitation. The recrystallization mechanisms occurring dynamically in the different grain populations were investigated via electron backscatter diffraction (EBSD). It was found that local microstructure could affect the operative recrystallization mechanism, with different mechanisms seen in the deformed and recrystallized regions, owing to their different precipitate distributions. Within a single deformed grain, three apparently distinct dynamic recrystallization (DRX) mechanisms were identified. The interaction of recrystallization with precipitates plays a central role in DRX. In certain cases precipitates may stimulate discontinuous DRX by providing recrystallization nuclei, alternatively they may impede and limit the growth of recrystallized grains, or in other cases still they promote continuous recrystallization.(c) 2022 The Author(s). Published by Elsevier B.V. CC_BY_4.0
查看更多>>摘要：Vanadium-based oxides are one of the most promising cathode materials, but pure vanadium-based oxides have poor cycle performance and are prone to structural collapse. Hence, many cumbersome synthesis methods have been used to synthesize vanadium-based compounds. Here, we used a very simple one-step hydrothermal method to fabricate disordered V12O26/V2O5 composites with different microstructure, indicating that layered structure is beneficial to improve electrochemical performance of V12O26/V2O5 composites. After assembling the battery, the specific capacity is 374 mAh g(-1) at 0.5 A g(-1), and the capacity remains 211.5 mAh g(-1) after 2500 cycles at 5 A g(-1). (C) 2022 Elsevier B.V.All rights reserved.
查看更多>>摘要：The development of functionalized polymer-based filament enables the fused deposition modeling (FDM) 3D-printed materials or structures with a wide range of unique functions. This work explores the use of MAPbX(3) (MA = CH3NH3, X = Cl, Br, I or mixture of them) perovskite quantum dots (PQDs) by harnessing their unique optical properties for the development of fluorescent 3D printing filaments. Firstly, a one-pot strategy for scalable synthesis of MAPbX(3) PQDs-polycaprolactone (PCL) composite was proposed by in situ formation of PQDs in PCL matrix. To demonstrate the ability for the obtained PQDs-PCL composites to fabricate fluorescent filaments, the effects of filament functionalization on optical properties of PQDs, as well as thermal and mechanical properties of polymer matrix were then comprehensively studied. Owing to the good protective capability of PCL, the synthesized PQDs-PCL composites exhibit comparable PLQY and enhanced UV, water and thermal stability compared to that of pure PQDs. Moreover, high concentration of embedded PQDs in PQDs-PCL composites was obtained with decreasing amount of PCL. The aggregation of PQDs at high temperature combined with the poor interaction between PQDs and surrounding PCL matrix led to the decreased thermal transition temperature and reduced mechanical properties in PQDs-PCL composites relative to pure PCL. The glass transition temperature was found to decrease by 5.5 degrees C, while the mode of failure changed from plastic fracture for pure PCL to brittle fracture for the highest concentration of PQDs in PCL tested. Consequently, PQD-PCL composites were further processed into fluorescent filaments and further fluorescent objects or structures via 3D printing. Green LED and white LED devices were realized by the combination of UV LED chip with 3D printed MAPbBr(3) PQD-PCL thin-film, and blue LED chip with MAPbBr(3) PQD-PCL thin-film and K2SiF6:Mn4+ phosphor, respectively, demonstrating that the PQDs-functionalized 3D printing filaments have great potential in fields of optoelectronic application. (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：The effect of the addition of Al2O3 on the viscosity of the iron-compound bearing CaO-SiO2-Al2O3-MgO slags with different SiO2 content (= 30, 40, and 50 wt%) was investigated at high temperatures. The addition of Al2O3 increased the viscosity of iron-compound bearing calcium-aluminosilicate melts. The addition of Al2O3 to the slag at low-SiO2 content (= 30 wt%) increased the fraction of Fe2+ at a fixed iron content because Fe3+ cations prefer to exist as tetrahedral unit, i.e., Fe3+ [IV], in the melt. On the other hand, the addition of Al2O3 to the slag at high-SiO2 content (= 50 wt%) increased the fraction of Fe3+ at a fixed iron content due to the preference of octahedrally coordinated Fe3+ [VI] in the slag. Although the redox equilibrium reaction of iron in the CaO-SiO2-Al2O3-FetO-MgO system was strongly affected by the basicity of the melt, the addition of Al2O3 polymerized silicate networks regardless of the SiO2 content in the slags. The activation energy for the viscous flow of the slags had a linear correlation with the non-bridged oxygen per tetrahedron (NBO/T) in the aluminosilicate network. Therefore, the viscosity of the iron-compound bearing calcium-aluminosilicate melt was determined by the degree of polymerization within the aluminosilicate networks.(c) 2022 Elsevier B.V. All rights reserved.
V. Butova, VeraAboraia, Abdelaziz M.V. Shapovalov, VictorDzhangiryan, Narek A....
9页
查看更多>>摘要：We report an eco-friendly, simple, and scalable method of FeF2 cathode production. MIL-88A was synthesized in a water medium without any additives. It was used as a source of iron (3 +) ions during pyrolysis. The porous structure of such a sacrificial agent allowed us to incorporate poly-vinylidene fluoride molecules as a guest component into a host MIL-88A framework. Pyrolysis in Ar-flow results in two simultaneous processes: reducing Fe3+ into Fe2+ and forming porous carbon shells for FeF2 nanoparticles. Applying complex analysis of high-resolution TEM images, porosity measurements, and XANES spectroscopy, we have revealed that obtained iron fluoride is composed of nanoparticles with elongated and hexagonal shapes. Both iron fluorides were attributed to tetragonal FeF2 structure type, contained only Fe2+ ions, and were covered with porous carbon shells. The obtained material was used as a cathode for a lithium-ion battery and showed good stability and a high capacity of 425-330 mA h/g. The proposed water-based synthesis of MIL-88A as a precursor in combination with mild pyrolysis conditions and good electrochemical performance make this material promising for cathode application. (c) 2022 Published by Elsevier B.V.
NSTL
Elsevier