查看更多>>摘要：Sodium-ion batteries (SIBs) have attracted widespread attention because of the economic benefit of low-cost and abundance of sodium resources. Iron-based electrodes (sulfide, selenide and phosphide) that operate through conversion mechanism have shown huge potential for excellent sodium-ion storage. However, the problems related with serious volume expansion and lack of general synthesis methods of iron-based materials shorten the cycle life and hindered their application in SIBs. Herein, a general synthetic strategy of electrospinning process was developed to achieve the yolk-shelled FexQy@C (Q = S, Se and P) film for binder-free anode of high-performance SIBs. Such method has more precursor materials to choose from and is highly scalable. More importantly, the designed electrodes have a unique yolk-shell structure and a three-dimensional conductive network. When applied as a binder-free anode of SIBs, all three samples exhibit outstanding sodium storage performance (FeS2@C-40: remaining 280 mAh g?1 after 400 cycles at 1 A g?1, Fe7Se8@C-40: remaining 186.5 mAh g?1 after 200 cycles at 0.1 A g?1 and FeP4@C-40: remaining 205 mAh g?1 after 1000 cycles at 0.5 A g?1). Therefore, the scalability and universality of this general synthetic strategy can open up a new direction for the exploration of high-energy density and flexible electrode materials.
查看更多>>摘要：This study investigated the mechanical behavior of ZrxTa1?x (x = 21–79 at%) thin films and nanolayered films of ZrTa with modulated composition as model systems to gain insight into the hardness and toughness of metallic glasses and metallic glass nanocomposites. The monolithic films exhibit two primary microstructures, namely, a fully amorphous form (Zr = 35–70at%.) and an amorphous-crystalline composite (21–30 at% Zr). The amorphous films show a monotonic hardness variation with composition over a wide range of 5.5 – 9 GPa. The partial crystallization of the films results in a further jump in hardness, as opposed to the general trend of softening upon crystallization. The emergence of the crystalline phase also improves the ductility of the films, as verified by nanoindentation-based fracture toughness measurements. The indentation pile-up exhibits several shear bands in the fully amorphous films, replaced by a featureless pile-up zone for the case of Zr25Ta75, further verifying the superior toughness of the composite. The second part of the analysis pursued obtaining a similar toughening through fully amorphous nanolayered films of Zr35Ta65 / Zr70Ta30. The results indicate that these films provide a balanced combination of high hardness and enhanced ductility, providing an alternative route to the development of tough metallic glass coatings. Data Availability: The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.
查看更多>>摘要：A highly self-ordered arrangement of a nano-concave morphology was prepared on Al foil by an anodization treatment in 0.3 M oxalic acid or 0.3 M tartaric acid followed by the removal of the resulting anodic alumina film. The foil was then used as the anode of dual-ion batteries. The wettability of the Al surface increased with increasing degree of self-assembly, facilitating a uniform distribution of electrochemically active sites during alloying/dealloying process. The highly self-ordered surface of Al foil anodized in oxalic acid can improve the electrochemical performance significantly compared to the only electropolished Al foil anode and the relatively disorderly surface state of the anodized Al foil obtained in tartaric acid. A 93 mA h g?1 capacity and 98% capacity retention were obtained after 500 cycles at 100 mA g?1, as well as a high reversible capacity of 83 mA h g?1 at 500 mA g?1. Although the capacity of the self-ordered regulated Al foil anode was not the highest among the existing anode materials, its synthesis process was more straightforward and cost-effective.
查看更多>>摘要：In this paper, we studied the electrical and structural properties of Cu/Ti/Al Ohmic contacts to p-type 4 H-SiC with different annealing temperatures and Cu layer thicknesses. Compared with Ti/Al contact annealed at 900–1000 ℃ to form ohmic contact, Cu/Ti/Al contact forms ohmic contact (1.0 ×10?4 Ω·cm2) after annealing at 800 °C. When the annealing temperature is 850 ℃ and 900 ℃, the contact resistivity of Cu/Ti/Al contact is about 5.4 × 10?5 Ω·cm2. Scanning Electron Microscopy (SEM) is used to observe the surface morphology of the sample. With the increase of annealing temperature, the roughness of the sample surface and the number of pits continue to increase. X-ray spectra shows that the addition of Cu makes the contact form Ti3SiC2 at a lower annealing temperature which is the key to low contact resistivity.
查看更多>>摘要：The effect of wall thickness on the casting microstructures of polycrystalline Ni-based superalloy K465 was investigated. Abnormal feather-like grains with high-angle grain boundaries (HAGBs) were detected. The quantity of the feather-like grains increased with the decrease of the specimen thickness. Experimental investigation and numerical simulation results showed the cooling rate and the residual stress increased with the decrease of the specimen thickness. The increased residual stress and the heat treatment resulted from the sand box with elevated temperature induced the formation of the abnormal feather-like recrystallized grains. This work provides a guidance for producing turbine blades made of cast superalloys.
查看更多>>摘要：Zn-ion hybrid supercapacitors combine the advantages of high energy density of batteries, high power density, and excellent cycling stability of supercapacitors. In this report, plasma treated carbon microspheres with N, P, O co-doping are prepared and used as cathode material for Zn ion hybrid supercapacitors. The combination of plasma treating and heteroatom doping plays a critical role in tailoring the electrochemical performance of the prepared carbon microspheres in Zn ion hybrid supercapacitors. A capacitance of 215.2 F g?1 is achieved for the as-prepared carbon microspheres at 0.1 A g?1, and the supercapacitor fabricated using the carbon microsphere display a high energy density of 54.4 Wh kg?1 with a power density 4000 W kg?1 and an excellent retention rate of ~ 100% after 10,000 cycles at 5 A g?1. This work is inspiring for the manufacturing and developing new high-performance carbon materials for Zn-ion hybrid supercapacitor
查看更多>>摘要：The increasing environment pollution is an urgent problem to be solved. Photocatalytic technology has potential application in environmental governance because of its low-cost, environmental friendliness, high efficiency, and high selectivity. Among the many photocatalyst materials available, graphite carbon nitride (g-C3N4) has been highlighted because of its high stability, nontoxicity, high adsorption capacity, and good photochemical properties for wasterwater treatment. However, few review reports have used g-C3N4 of different nanomaterial dimensions (0D, 1D, 2D, and 3D) with excellent electron transport, light absorption range, and large specific surface area in dye degradation. This review summarizes the following: the use of solar energy as the driving force of the photocatalysts as a starting point, the factors affecting photocatalytic performance in the preparation process, and the catalytic mechanism of the photocatalytic degradation of dyes. Moreover, this review discusses the practical applications of 0D, 1D, 2D, and 3D photocatalytic materials of g-C3N4 in the degradation of Rhodamine B (RhB), methylene blue (MB), and methyl orange (MO). Finally, the problems and challenges in the application of photocatalysts are discussed.
查看更多>>摘要：Laser-powder bed fusion (L-PBF) is being increasingly employed in the fabrication of commercially pure titanium (CP-Ti) components for biomedical applications. However, L-PBF-manufactured CP-Ti parts typically exhibit high strength and reduced ductility owing to the formation of acicular α′ martensite. It is essential to decompose the acicular α′ martensite into the equilibrium α phase through post-heat treatments to achieve superior mechanical properties. In this study, post-heat treatments were applied to L-PBF-fabricated CP-Ti Gr. 1?Gr. 4 samples. The microstructures of the as-fabricated CP-Ti samples were dominated by acicular α′ martensite, which exhibited high strength (>800 MPa) but low ductility (<20%). Full annealing resulted in the formation of equiaxed grains and the disappearance of the columnar structures in the CP-Ti samples. The equiaxed grains contributed to high ductility (>30%) in the Gr. 1 and Gr. 2 samples, but low ductility (<20%) in the Gr. 3 and Gr. 4 samples. This low ductility is associated with the formation of grain-boundary β layers. Well-designed partial annealing led to the formation of bimodal structures consisting of both equiaxed and fine lamellar grains. This specific structure provides both a high strength (>700 MPa for Gr. 2 and,>850 MPa for Gr. 4) and high ductility (>35% for Gr. 2 and Gr. 4), which are superior to those of the samples processed under full annealing conditions. Therefore, tailoring the bimodal structure in the L-PBF-manufactured CP-Ti for both high strength and ductility is promising for biomedical applications.
查看更多>>摘要：The high concentration Tm3+ ions doped fluorotellurate glass samples (TeO2-Al2O3-BaF2) fabricated by high-temperature fusion technique and the luminescence properties of the glass samples were examined based on absorption and fluorescence spectra to forecast the latent capability of TAFT4 glass for ~ 2 μm band fiber lasers. The thermodynamic properties of the glass samples utilized for drawing the optical fiber, internal structure and the maximum phonon energy were characterized based on the thermal stability parameter ΔT and Raman spectra, respectively. The Judd-Ofelt (J-O) intensity parameters (Ωt) was estimated from the recorded absorption spectral data, and the estimation results showed that the value of Ω2 was as high as 6.97 × 10?20 cm2. To reveal the spectral properties of TAFT4 glass sample, significant radiative parameters including spontaneous raditive transition probabilities (Arad), fluorescence branching ratios (β), radiative lifetimes (τrad), absorption and emission cross sections of Tm3+ ions excitation energy levels were determined using J-O intensity parameters. Furthermore, the calculation of the gain coefficient is included to determine its capability as a gain medium. The fluorescence decay behavior of Tm3+ ions and the energy transfer mechanism were investigated and analyzed in detail, and the macroscopic rate WET of the CR process between Tm3+ ions in TAFT4 glass was quantified by the transfer constants CD-D and CD-A. The value of WET was high up to 2073.4 × 10?20 cm3/s by estimation. As mentioned above, the fabricated TAFT4 glass sample may be a suitable gain medium that can be used for ~2 μm band fiber lasers.
查看更多>>摘要：This investigation highlights the synthesis of an efficient photocatalyst, 10% gadolinium (Gd) doped BiFeO3 (BGFO) nanoparticles, via a facile hydrothermal technique at a lower reaction temperature of 160 °C and its effective application towards the degradation of industrial effluents, such as rhodamine B (RhB), methylene blue (MB) and pharmaceutical pollutants such as ciprofloxacin (CIP), levofloxacin (LFX) under solar irradiation. The successful fabrication of the photocatalyst was confirmed by the Rietveld refined powder X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analyses. The high resolution transmission electron microscope imaging demonstrated the formation of nanoparticles with excellent morphology and very good crystallinity. The optical characterizations revealed a reduction in the optical band gap from 1.95 to 1.18 eV, as well as effective suppression of electron-hole pair recombination in the BGFO sample. Notably, the photocatalyst BGFO demonstrated 96% and 97% degradation of RhB and MB within 240 and 180 min of solar irradiation, respectively. Moreover, the photodegradation of colorless organic contaminants CIP and LFX was also examined to evaluate the photosensitization properties. Interestingly, about 80% and 79% degradation of CIP and LFX was obtained within 240 min of solar irradiation. The enhanced photocatalytic activities of BGFO could be attributed to the excellent morphology, good crystallinity, increased optical absorption, and effective separation of the photogenerated charge carriers. Additionally, based on the band structures, a plausible mechanism was proposed to comprehend the rationale behind the influential photocatalytic performance of the synthesized nanoparticles to explore their potential towards the future of wastewater treatment on an industrial scale.
NSTL
Elsevier