查看更多>>摘要：? 2022 Elsevier B.V.Developing high-capacity anode materials is one of the crucial measures to effectively increase the energy density of Li-ion batteries. As a promising anode material, ZnFe2O4 has been widely concerned because of its high specific capacity and low cost. However, the inherent poor conductivity and dramatic volume changes during cycling restrict its further commercial development. In this paper, ZnFe2O4/C composites have been successfully designed by utilizing the self-swelling effect of gelatin to embed ZnFe2O4 nanoparticles inside 3D porous carbon dispersedly. At 200 mA g–1, ZnFe2O4/C obtained at 450 °C exhibits a high initial discharge specific capacity of 1367.1 mAh g–1. The excellent electrochemical performances are derived from the synergistic effect of ZnFe2O4 active nanoparticles and 3D porous carbon framework. Nano-sized particles can shorten the transport length of ions and electrons inside the active material. The presence of 3D porous carbon can realize high-speed charge transmission, facilitate the electrolyte infiltration, protect active particles, and buffer the structural destruction caused by volume change of metal oxide upon cycling. In addition, ZnFe2O4/C composites also show promising potential as anode materials of Na-ion batteries. This work provides a bright direction for the preparation of advanced anode materials for secondary rechargeable batteries.
查看更多>>摘要：? 2022 Elsevier B.V.In this paper, four NiO nano-arrays with different morphology on nickel foam were synthesized by a hydrothermal approach. It is found that the porous single crystal NiO nanoflake array (PNFA) holds superior electrochemical properties, better than the other three samples. The specific capacitance of the PNFA obtained from the cyclic voltammetry curve was 716 F g?1 and that derived from the galvanostatic charge-discharge curve was 589 F g?1 in three-electrode system. The cycling stability of the PNFA could retain as high as 92.4% after 5000 cycles. When the PNFA was assembled into a symmetric supercapacitor, the PNFA//PNFA device exhibited an energy density of 39.3 W h kg?1 (at 550 W kg?1) and could retain 13.2 W h kg?1 (at 11,000 W kg?1) in two-electrode system. Furthermore, the SEM, XRD, TEM and XPS results prove that the PNFA is a special porous single crystal structure, which combines the advantages of the cross-linked single crystal structure for facilitating electron transfer and the porous structure providing more interfaces for insertion/exit of electrolyte ions from the active material. It indicates that the PNFA is a potential electrode material for supercapacitors.
查看更多>>摘要：? 2022 Elsevier B.V.Microstructure evolution during “abc” deformation of commercial-purity titanium was investigated. Continuous dynamic recrystallization (CDRX) played a dominant role in the microstructural changes, although mechanical twinning also contributed to some extent. It was found that CDRX developed preferentially at the original grain boundaries, thus resulting in a necklace-type microstructure. This effect was attributed to the comparatively-high local stresses in these areas, which promoted pyramidal<c+a>slip and thus enhanced evolution of deformation-induced boundaries. It was also established that changes in strain path resulted in a noticeable re-organization of the pre-existing dislocation structure due to a Bauschinger Effect and thus promoted essential material softening. This phenomenon retarded the evolution of dislocation boundaries and thus tended to lead to stagnation in microstructure refinement.
查看更多>>摘要：? 2022 Elsevier B.V.The transition of the A2 phase with random Fe and Cr atoms distribution to the sigma (σ) phase in Fe-46 wt%Cr alloy during isothermal annealing near 655 and 700 °C is investigated both in the bulk material by in situ neutron diffraction and on the surface of a sample by X-ray diffraction method. Kinetics of the σ-phase formation is quantitatively described with the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model. According to neutron data, the A2 phase fully transformed to σ-phase at 655 °C for 5 h. In X-ray diffraction experiments, the partial A2 to σ transition and subsequent reverse transformation of the σ-phase into the A2 phase are observed, and the probable reason for this phenomenon is discussed.
查看更多>>摘要：? 2022 Elsevier B.V.Activated carbon (AC) with high porosity and surface area as a catalyst carrier can enhance the catalytic activity and stability of metal nanoparticles with well dispersion to avoid aggregation. Herein, silver molybdenum oxysulfide (AgMoOS) nanoparticles supported by activated carbon with different porous sizes were synthesized through a facile method for photocatalytic H2 evolution reaction and pollutants reduction. The highest H2 evolution of 338.9 μmol/h was obtained by microporous AC-supported AgMoOS (AgMoOS@AC-1) under visible-light irradiation using Na2S/Na2SO3 as a hole scavenger reagent. Likewise, 76.9% of the 4-NP reduction is achieved by in-situ generated proton within 160 min. AC could lower the recombination rate of photo carriers due to its pore channels. Under the dark condition, 10 mg AgMoOS@AC-1 completely reduced MB, MO, RhB, 4-NP, and Cr6+ within 4, 4, 9, 9, and 12 min, respectively. This excellent catalytic activity is due to a good dispersion of AgMoOS nanoparticles on AC-1, electron hopping transport of Mo4+→ Mo6+ ions, and surface oxygen vacancy. AgMoOS@AC catalyst also exhibits good stability and efficiency that provides a practical catalytic application to reduce chemical pollutants and environmental remediation.
查看更多>>摘要：? 2022 Elsevier B.V.Room-temperature (RT) ferromagnetic atomically thin transition metal chalcogenides (TMCs) provide a novel platform for discovering new physical phenomena in the two-dimensional (2D) limit and developing the next-generation spintronic applications. Recent progress in exploring the RT ferromagnetism in 2D TMCs have attracted significant interest from experimental and theoretical scientists; However, the semiconducting TMCs are non-magnetic. In parallel, the inconsistency of magnetism between density functional theory (DFT) calculations and experimental results persist in both TMC semiconductors and metals. We review the strategies for RT ferromagnetism in 2D TMC semiconductors and the origin of RT ferromagnetism in 2D TMC metals, followed by the discussion of promising future directions in the area of RT ferromagnetic 2D TMC materials.
查看更多>>摘要：? 2022 Elsevier B.V.The dielectric properties of Ag1?xLixNbO3 (ALNx) ceramics (x ≤ 0.08) were investigated in a broad frequency range (20 Hz – 90 THz). Nature of the room temperature phase of ALNx (x ≤ 0.04) ceramics is ferrielectric while for x ≥ 0.05 ferroelectric. The frequency dependence of dielectric permittivity is mainly caused by the relaxational mode close to the ferrielectric/ferroelectric phase transition temperature and domains dynamics at lower temperatures. At room temperature and 10 GHz frequency the dielectric permittivity is quite high (270 for ALN0), while dielectric losses tanδ low (0.037 for ALN0) for all ALN compositions, therefore these ceramics are attractive for various microwave applications. Moreover, their piezoelectric properties were also investigated and the highest piezoelectric coefficient value was observed for ALN6 (200 pC/N at room temperature and 750 pC/N at 465 K). For ALNx ceramics when x ≥ 0.06 15 polar modes were distinguished in the IR spectra and 20 polar modes for ALNx ceramics with x < 0.06, however the number or modes is temperature independent in investigated temperatures range (103–500 K).
查看更多>>摘要：? 2022 Elsevier B.V.Thermal barrier coatings (TBCs) are widely used to protect high temperature structure parts against oxidation and corrosion. The failure mechanism study of TBCs is very important and the stress evolution is core content of failure mechanism research. In this work, a 8YSZ:Eu coating was produced via atmospheric plasma spraying (APS) method. Thermal cycling tests was carried out at 1300 ℃. The residual stress evolution of the coating was detected by a Eu3+ photoluminescence piezo-spectroscopy based on the relationship between stress and the peak position of 5D0→7F2 transition of Eu3+ ions. The failure mechanism of the 8YSZ:Eu coating was also studied. The as-sprayed 8YSZ:Eu coating contains metastable t ′ -ZrO2 and amorphous structure. The stress distribution is inhomogeneous with both compressive stress and tensile stress. After 1000 thermal cycles, the initial compressive stress changed to tensile stress due to the thermal expansion coefficients (TEC) mismatch and irreversible plastic deformation during thermal cycling. With thermal cycling going on, the compressive stress appeared again and the averaged tensile stress decreased due to the volume expansion caused by phase transformation of the t ′ -ZrO2 to m-ZrO2 and the formation of cracks. Formation of the thermally grown oxide (TGO), phase transformation, thermal expansion mismatch are factors for the coating failure.
查看更多>>摘要：? 2022 Elsevier B.V.A high-throughput technique can realize fast and efficient material screening, and greatly improve the discovery efficiency of advanced materials. In the present work, the gradient composition films of the W-Ta-CrFeNi high-entropy alloy were prepared by the three-target magnetron co-sputtering technique. The gradient alloy films exhibited a body-center-cubic (BCC) structure near the W or Ta element target, and an amorphous structure near the CrFeNi target region. Considering the effect of the undercooling degree, the amorphous formation region (using Ω ~ δ) was larger than that of the bulk alloys. These alloy films displayed ultra-high nano-indentation hardness, with the maximum hardness reaching ~ 20.6 GPa. The elastic modulus in the high-entropy composition region was lower than that in the low-entropy composition region. There is a nonlinear relationship between the nano-indentation hardness and mix-entropy of the alloys. This study provides a reference and alternative material library for the development of high-performance advanced materials.
查看更多>>摘要：? 2022 Elsevier B.V.Laser powder-bed fusion has been widely utilized to produce complex NiTi devices because of relatively better surface finish and geometrical accuracy. However, NiTi alloys fabricated by laser powder-bed fusion suffer from strength degradation and unstable shape recovery behavior induced by the formation of pore defects and the variation of martensitic transformation, respectively. In this work, the mechanical and functional properties of HfH2-decorated NiTi shape memory alloy fabricated by laser powder-bed fusion have been investigated. Through careful clarification of the effects of microstructure characteristics on mechanical and functional properties, it is concluded that the addition of Hf (<5 at%) efficiently strengthens the NiTi matrix and thus eliminates strength degradation induced by pore defect formation. Moreover, the addition of Hf (<5 at%) into the NiTi matrix weakens martensitic transformation variation through improvement of the critical stress to induce martensitic transformation, resulting in stability enhancement of shape recovery behavior.
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