查看更多>>摘要：? 2022 Elsevier B.V.Carbides are vital phases in determining the mechanical properties of solid solution nickel-based superalloys. The precipitation, transformation, and coarsening of carbides in a high-carbon Ni-based superalloy during selective laser melting and the HIP process were investigated using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and thermodynamic modeling. A high carbon content (0.2 wt%) resulted in complicated MxCy-type carbides enriched in W and Cr due to the uneven segregation of Cr and W in the as-built GH3230G. The complicated carbides were transformed into M6C-type carbides, and coarsening of carbides occurred after HIP treatment. Thermodynamic calculation results explained the precipitation and coarsening of carbides. In addition, larger carbide particles with a size of 1.1 μm were always distributed along the epitaxial grain boundaries, while smaller carbide particles at a scale of 0.3 μm were apt to form at the subgrain boundaries. The cross-section micrographs below the fractures showed that some microvoids were always initiated at coarse carbide/matrix interfaces, which induced intergranular fracture at elevated temperatures. This work can be extended to elucidate carbide formation, transformation, and evolution for additively manufactured superalloys and predict their impact on the mechanical properties of this kind of alloy.
查看更多>>摘要：? 2022 Elsevier B.V.Manganese dioxide (MnO2) is a promising cathode candidate for advanced rechargeable Zn-ion batteries (ZIBs) owing to its low cost, high theoretical capacity and high output voltage. However, the poor stability and low practical capacity has greatly hampered its commercialization. Herein, we demonstrate a crystal form modulation strategy to enhance the capacity and cycling durability of commercial γ-MnO2 as robust ZIBs cathode material. By introducing new β-MnO2 crystal form with compact (1 × 1) tunnel structure after simple calcination, the γ- and β- co-existed MnO2 (denoted as m-MO) shows enhanced electrical conductivity and structural stability. Consequently, the m-MO cathode exhibits an excellent capacity of 273.6 mAh g–1 at 0.25 A g–1 with good cycle stability, much higher than the pristine γ-MnO2 cathode (156.7 mAh g–1). Furthermore, an aqueous ZIBs based on m-MO cathode delivers a large peak energy density of 349.1 W h kg–1 at 0.322 kW kg–1 and power density of 4.77 kW kg–1 at 123.01 W h kg–1. This work presents an effective crystal form modulation strategy to construct high-performance ZIBs cathodes based on commercial MnO2, which is highly potential for further commercial applications.
查看更多>>摘要：? 2022 Elsevier B.V.It is well known that Fe-Al intermetallic compounds have broad application prospects at high temperatures. The performance of Fe(Al,Ta)/Fe2Ta(Al) eutectic composite prepared by Bridgman directional solidification technology has been further improved as compared with that of Fe-Al intermetallic compounds. In this paper, high-temperature oxidation behaviors of directionally solidified Fe(Al,Ta)/Fe2Ta(Al) eutectic composite in static air were studied by isothermal oxidation test. The oxidized surface and cross section of directionally solidified Fe(Al,Ta)/Fe2Ta(Al) eutectic composite were characterized by scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy. The mechanism of high-temperature oxidation was analyzed from the point of view of kinetics and thermodynamics studies combined with the data of the Ellingham-Richardson diagram. The oxidation weight gain of the Fe(Al,Ta)/Fe2Ta(Al) eutectic composite at the same solidification rate is increased with temperature and Al2O3 is formed at the beginning of oxidation. However, a dense oxide film is not formed due to the small content of Aluminum, and the final oxide film for Fe(Al,Ta)/Fe2Ta(Al) eutectic composite after 100 hours′ oxidation is composed of Fe2O3 and Al3Fe5O12.
查看更多>>摘要：? 2022 Elsevier B.V.Fabrication of semiconductor-based photocatalysts with excellent charge separation efficiency has gained substantial attention due to their notable performance for water treatment applications. Herein, we synthesized a flat reduced graphene oxide-based gadolinium-doped bismuth vanadate (rGO/Gd/BiVO4) composite by a facile hydrothermal and ultra-sonication approach. By examining the photodegradation of Methylene Blue (MB) dye from an aqueous solution under visible light, we compared the photocatalytic behavior of the rGO/Gd/BiVO4 composite to that of pristine BiVO4 and Gd/BiVO4. The photo-excited electron/hole pair recombination was suppressed by adding Gd and rGO to BiVO4. This led to rGO/Gd/BiVO4 having a faster rate (k = 0.027 min?1) of MB degradation than Gd/BiVO4 (k = 0.0095 min?1) and pure BiVO4 (k = 0.006 min?1). In particular, the rGO/Gd/BiVO4 degraded almost 97% of the MB dye under visible-light irradiation in 100 min, whereas the BiVO4 and Gd/BiVO4 samples removed only 53% and 69% of the MB dye, respectively. The rGO/Gd/BiVO4 composite displayed 16-fold and 2.40-fold larger transient photocurrent responsiveness than the BiVO4 and Gd/BiVO4 samples. Subsequently, the BiVO4 and Gd/BiVO4 showed a charge recombination rate of 2.18 and 3.62 s, separately, which was relatively smaller than the rGO/Gd/BiVO4 result (= 8.41 s). The increased photocatalytic activity of rGO/Gd/BiVO4 is due to the development of heterojunction between Gd/BiVO4 and the rGO sheets, which facilitates the absorption of photons as well as the separation of photogenerated electrons and holes.
查看更多>>摘要：? 2022 Elsevier B.V.Hydrolytic dehydrogenation of ammonia borane (AB) has attracted much attention due to its high hydrogen content and stability. Therefore, the design and construction of low-cost and high-performance catalysts for AB hydrolysis are of great significance. In this work, Co/CoFeOx-X (X is the additional content of Fe precursor) bimetallic oxide nanofilms having an amorphous structure were prepared on an (IL)/water interface for the hydrolysis of AB. Strategies including the rapid addition of metal precursors and variation of Co/Fe atom ratios were employed to induce an amorphous structure for inhibiting the rearrangement of the formed metal nuclei and optimizing the alloying effect on the IL/water interface. This ultrathin amorphous nanofilm structure can expose more metal active sites. Moreover, the electronic interaction between Fe and Co after doping Fe into the Co/CoOx nanofilms facilitates the adsorption and activation for AB and H2O molecules. As a result, the optimized Co/CoFeOx-25 catalyst exhibits excellent catalytic activity with a turnover frequency (TOF) value of 12.25 molH2·molCo–1·min–1, which is considerably higher than that of the monometallic Co/CoOx catalyst. This enhanced activity can be ascribed to the morphology advantages and the electronic effect of Fe and Co on the Co/CoFeOx-25 catalyst. This work provides a promising method to design the highly efficient non-noble metal catalysts for the hydrolysis of chemical hydrides.
查看更多>>摘要：? 2022 Elsevier B.V.In recent years metal ion capacitors (MICs) and supercapacitors devices have been reported as promising alternatives for energy storage on a large scale. MICs are characterized by superior power density and energy density, combining advantages of metal-ion batteries such as lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, zinc-ion batteries, etc., and those of supercapacitors. Herein we provide a review of recent progress on MICs, focusing on the sodium-ion capacitor (SICs), potassium-ion capacitors (PICs), and zinc-ion capacitors (ZICs); starting from the basic concepts (the perspectives of the design concepts, the configuration of MICs devices, the electrochemical behavior and the energy storage mechanism), the electrode materials and electrolyte systems in details with some examples. The factors impacting the electrochemical performances of the MICs are also provided in this work and end with a conclusion. This review will be helpful for researchers, especially the new researchers in the field of MICs and supercapacitors, to have an overall understanding of MICs and supercapacitors, develop electrochemical storage devices, and respond to the need forenergy storage in electric vehicles and electronic devices.
查看更多>>摘要：? 2022 Elsevier B.V.We report an in situ synthesis of α-Fe2O3/LaFeO3 compounded with g-C3N4 and Ti3C2 MXene to form multiple Z-scheme/Schottky heterojunctions, α-Fe2O3/LaFeO3/g-C3N4 /Ti3C2 (FLCT). In FLCT, α-Fe2O3/LaFeO3 promoted carrier migration, g-C3N4 caused electrons to move directionally toward Ti3C2, inhibiting the carrier complex, and the Ti3C2 substitution of a noble metal provided more adsorption active sites and promoted carrier separation. The synergistic effect of the multiple Z-scheme/Schottky heterojunctions endowed the FLCT composite with an excellent photocatalytic performance. To demonstrate the extensive applicability of the composite materials in the photocatalytic degradation and reduction of wastewater, methylene blue (MB), rhodamine B (Rh B), tetracycline hydrochloride (TC), and hexavalent chromium ions (Cr (VI)) were used as model pollutants; 91.30% of the MB, 84.32% of the Rh B, and 76.11% of the TC were photocatalytic degraded. In addition, 79.60% of the Cr (VI) was photocatalytically reduced by FLCT. These results showed that the composite catalyst exhibited photocatalytic degradation or reduction efficiencies that were 3.41-, 3.86-, 5.44-, and 4.14-fold greater than those of pure LaFeO3 for MB, Rh B, TC, and Cr (VI), respectively. The intrinsic relationship between the composite structure and the photocatalytic performance was investigated to reveal the enhancement mechanism of the composite photocatalytic performance. The charge migration path and pollutant degradation mechanism in the photocatalytic system were elucidated. This work provides a novel concept for designing heterojunction-structured photocatalysts and provides an experimental foundation for photocatalytic technology to treat water pollution.
查看更多>>摘要：? 2022 Elsevier B.V.In recent years, biodegradable Zn-based materials became a hopeful approach for new generation biomedical implants due to their acceptable mechanical performance, moderate biodegradation rate, and good biocompatibility. In this study, the combination of high-energy planetary milling and spark plasma sintering process were employed to fabricate n vol% β-TCP (n = 0, 0.5, 1, 3, 5, 10)/Zn composites with uniform microstructure and high relative density. The microstructure investigation, mechanical performance, degradation behavior, in vitro and in vivo properties of the composites were systematically investigated. As a result, β-TCP nanoparticles were homogeneously dispersed in the whole composites and possessed a good bonding interface with the Zn matrix. The degradation of pure Zn and β-TCP/Zn composites in vitro and vivo is a uniform corrosion process. Enhanced corrosion resistance attributed to the addition of β-TCP with a optimized content. The evaluation of osteogenic differentiation process showed that the addition of β-TCP induced the up-regulated expression of osteogesis-related genes (ALP) in mouse preosteoblasts, thus improving the osteogenic ability. As revealed by animal experiments, six months after implantation of pure Zn and 3TCP/Zn components, the blood biochemical parameters of rats showed no obvious tissue inflammation, indicating excellent in vivo biocompatibility of experimental materials. Histological investigation showed that with prolonged implantation time, the 3TCP/Zn components were more effective than pure Zn in promoting new bone formation. In summary, 3TCP/Zn matrix components developed in the present study should be useful for orthopedic implants.
查看更多>>摘要：? 2022Novel ionic state Co passivated carbon nanodots (Co-CDs) combined with NH2-MIL-125 as efficient photocatalysts Co-CDs/NH2-MIL-125 were fabricated in a convenient process for the first time. These materials exhibited excellent photocatalytic activity in both NO purification and hydrogen production under visible light irradiation. The NO purification rate of Co-CDs/NH2-MIL-125 increased to 46.6%, which was 20.2% and 13.4% higher than that of NH2-MIL-125 and CDs/NH2-MIL-125, respectively. Moreover, the hydrogen production efficiency of Co-CDs/NH2-MIL-125 reached 2261 μmol g?1, which was 6.86 times and 3.54 times of the values for NH2-MIL-125 and CDs/NH2-MIL-125, respectively. The corresponding properties characterized by Mott-Schottky, UCPL, and in situ DRIFTS, indicated that the introduction of Co2+ could not only passivate the CDs to further improve physicochemical properties, but also enhance the photocatalytic activity via the photosensitization and up-conversion effect. This research provides a promising strategy that adding active metal ions passivated CDs in the catalyst platform to improve photocatalytic performance.
查看更多>>摘要：? 2022 Elsevier B.V.In addition to the widely used lithium-ion secondary batteries, more and more concerns have been paid to solid-state batteries (SSBs) in the research on future-generation energy storage systems. The availability of sodium solid electrolytes, especially those with excellent ambient temperature conductivity and prominent chemical stability, is crucial for sodium-based SSBs. In this study, Na3.1Ge0.1Sb0.9S4, a novel sodium-ion solid-state electrolyte, was obtained via a solid-state chemical reaction utilizing the economical Na2S·9H2O as one of the raw ingredients. The properties of this new electrolyte were examined by using X-ray diffractometry, Raman spectroscopy, differential scanning calorimetry, scanning electron microscopy, and electrochemical techniques. The Na3.1Ge0.1Sb0.9S4 electrolyte, which released low amounts of H2S under ambient conditions, demonstrated the ionic conductivity of 5.1 × 10?3 S/cm at normal atmospheric temperature and the conducting activation energy of 0.156 eV. The enhanced ionic conductivity was attributed to the improvement of crystallinity and the unit cell enlargement caused by interstitial sodium defects.
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