查看更多>>摘要：? 2022 Elsevier B.V.To refine microstructure, adjust the ratio of γ/α2 and improve the mechanical properties, Ti46Al 2.6 C-xNb (at. %) alloys were prepared by arc melting under the action of ultrasound. The phase composition, lamellar colony size, elements distribution, the kinds and distribution of carbides and compressive properties were investigated. Results show that as the Nb content increases, the relative content of α2 phase and Ti2AlC phase increases, and the relative content of γ phase decreases. TiC phase completely reacts to form Ti2AlC phase and its shape changes from coarse long rod to short rod. The microstructure was refined with the addition of Nb under ultrasound treatment. Lamellar colony size decreases from 36.9 to 21.5 μm, lamellar spacing decreases from 1.6 to 0.8 μm, and the length-diameter ratio of Ti2AlC decreases from 5.4 to 4.0 when the Nb content increases from 0 to 8.0 at. %. During solidification process, not only the component supercooling and heterogeneous nucleation of Nb are increased, but also the crystal grains are broken and the nucleation barrier is reduced under the action of ultrasound to promote the nucleation. The microstructure is refined and the uniformity of the element distribution is improved. Compressive results show that the strength increases from 2074.1 to 2474.2 MPa and the strain increases from 23.4% to 28.0% when the Nb content increases from 0 to 4 at. %. The refinement of lamellar colony and Ti2AlC, the ratio of γ/α2 and solid-solution of Nb are the main reasons for improving compressive properties.
查看更多>>摘要：? 2022 Elsevier B.V.Prussian blue analogues, which have a stable structural framework and larger ion migration channels, are currently one of the most potential cathodes for potassium ion batteries. However, Prussian blue-based materials are susceptible to preparation conditions, resulting in vacancy defects and crystal water in structures, which seriously restricts the exertion of electrochemical properties. Herein, a novel preparation technology-an electrostatic spray assisted coprecipitation way protected by inert atmosphere is proposed and applied to the synthesis of K2Fe[Fe(CN)6] materials. The effects of preparation process on the crystallinity, microstructure and potassium storage performances of K2Fe[Fe(CN)6] are systematically discussed. The results prove that K2Fe[Fe(CN)6] synthesized by the new preparation process has good crystallinity (K1.56Fe[Fe(CN)6]0.89·□0.11·1.86 H2O), small particle size (~20 nm) and high specific surface area (104.31 m2 g?1), and finally exhibits excellent electrochemical performance, including an superb cycling stability of 89 mAh g?1 after 503 cycles at 0.5 C and rate capability of 82 mAh g?1 at 10 C. In addition, this preparation technology also provides a new strategy for the microstructure and performance optimization of other Prussian blue-based materials.
查看更多>>摘要：? 2022 Elsevier B.V.Sn-Pb-based perovskite is a promising solar cell material for its low toxicity and narrow band gap. However, the poor crystallinity of Sn-containing perovskite films and the facile oxidation of Sn2+ are obstacles to the efficiency and stability of Sn-Pb-based perovskite solar cells (PSCs). Herein, we developed a new additive strategy of tin acetate (SnAc2) to fabricate high-quality (HC(NH2)2)n(CH3NH3)1-nPb0.7Sn0.3IxBr3-x films by a two-step method and simultaneously restrict the oxidation of Sn2+ to Sn4+ by coordination between Sn2+ and Ac-. Moreover, SnAc2 built an Sn-rich environment to alleviate the intrinsic Sn2+ vacancies. All these effectively reduced the defect state densities and carrier nonradiative recombinations in the device, resulting in improvements in the performance of PSCs. The PSCs with the SnAc2 additive exhibited a increase in average power conversion efficiency (PCE) from 15.60% to 16.69%. Furthermore, the phenethylammoniumiodide (PEAI) post-treatment was introduced to passivate the SnAc2-containing perovskite films. Finally, the optimal cell with a PCE of 17.93% was obtained, which was second-best compared to the reported Sn-Pb-based PSCs by the two-step methods. Furthermore, the producibility and stability of devices are also improved due to the inhibited oxidation of Sn2+ by SnAc2 additives and the protection of two-dimensional (2D) (PEA)2PbI4 perovskites, the unencapsulated PSC maintained 80.4% of its initial efficiency when stored in air after 24 days.
查看更多>>摘要：? 2022 Elsevier B.V.The work is devoted to the study of the phenomenon of irreversibility of the magnetocaloric effect (MCE) in the vicinity of the magnetostructural phase transition (PT) in Ni-Mn-Ga Heusler alloys. For this purpose, the MCE was studied by the direct method in stationary (up to 14 T) and pulsed magnetic fields (up to 50 T), and a magnetic phase diagram was constructed. Using a specially designed microscope, in-situ studies of the magnetostructural phase transition were carried out in magnetic fields of up to 14 T. Comparing the results of the MCE with those of the phase diagram, as well as in-situ studies, made it possible to determine the width of the irreversible MCE region. In-situ studies have shown, that the main reason of the occurrence of the irreversible MCE is the presence of the residual martensite formed as a result of the first magnetization of the sample. The results are discussed within the framework of Landau's phenomenological PT theory, which predicts the disappearance of thermal hysteresis under a field of 30 T. Within the framework of the same theory, a recommendation is made to reduce the value of the critical field and, as a result, the width of the hysteresis.
查看更多>>摘要：? 2022 Elsevier B.V.It is drawing increased interest to exploit highly active and durable electrocatalysts based on earth-abundant elements for oxygen evolution reaction (OER). In this work, we successfully synthesized Fe-doped (Ni,Mn)Co2O4 nanorod arrays on nickel foam (labeled as FNMCO/NF) via a anion-exchange route with subsequent annealing process. Experiments showed that the initial concentration of [Fe(CN)6]3- anions could affect the electrocatalytic activity of the as-synthesized FNMCO/NF integral electrode. The FNMCO-6/NF prepared from 6 mM of K3[Fe(CN)6] solution presented the strongest OER electrocatalytic activity. Only overpotential of 242 mV or 449 mV was required to reach the current density of 10 mA cm?2 in 1 M KOH solution or 0.1 M phosphate buffer solution (PBS). Also, after continuously catalyzing for 155 h at 100 mA cm?2 in 1 M KOH solution or 150 h at 20 mA cm?2 in 0.1 M PBS, the overpotential of the as-obtained FNMCO-6/NF electrode rarely varied, implying its superb durability.
查看更多>>摘要：? 2022 Elsevier B.V.Antimony-doped SnO2 (SnO2:Sb) thin films were deposited on glass substrates via sol-gel spin coating and tested for CO2 gas and humidity sensors. The dominant peak (110) of XRD pattern of SnO2:Sb thin films confirmed the cassiterite tetragonal structure regardless of Sb dopant concentration. The spherical particles like morphology were found for all sample and confirmed by scanning electron microscopy (SEM). The transmittance spectra were recorded in the wavelength range 300–800 nm and the optical bandgap was varied from 3.65 to 4.03 eV on increasing Sb concertation in SnO2. From I-V characteristics, sample C3 has the minimum resistivity (1.08 × 108 Ω.cm) and maximum conductivity 9.23 × 10?9 (Ω.cm)?1 at bias voltage 5 V. The gas sensing characteristics of Sb-SnO2 thin films were examined at different operating temperatures (30 °C to 80 °C) for sample C0 to C4. The optimized sample C0 have gas sensor response 78.5% at ambient temperature (30 °C). The higher doping of Sb in SnO2 as sample C3 and C4 were suitable for higher operating temperatures (80 °C) and responses were 18.74% and 71%, respectively. The characteristics of humidity sensors were analysed in relative humidity (%RH) range from 10% to 90%RH for Sb-SnO2 thin films and found suitable for sample C0 at ambient temperature in mid humidity range (35–60%RH). The present study is an attempt to design a cost-effective and low-temperature-based resistive CO2 gas sensor and humidity sensor for the enhancement in sensing properties.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, a one-step chemical vapor deposition (CVD) method was used, utilizing template NaCl and dextrin as the porogen and structural support. The synthesized spinel MFe2O4 (M = Zn, Ni, Cu, Co and Mn) microspheres with multiple cavities structure were applied to the acetone gas sensor detection. Through the characterization of the sensitive materials, the average pore diameter of the microspheres was about 60 nm. Compare with other metal cations, when M = Zn or Ni, the MFe2O4 samples revealed the super gas sensitivity at working temperatures of 250 °C and 175 °C, and the response values to 100 ppm acetone were 25 and 24.3, respectively. In addition, they also exhibited excellent selectivity and long-term stability to acetone. The excellent gas sensitivity of ZnFe2O4 and NiFe2O4 could be attributed to the replacement of Fe with Zn and Ni ions to obtain a higher Fe3+/Fe2+ atomic ratio, thereby increasing the content of adsorbed oxygen. In summary, the gas sensing performance of spinel MFe2O4 oxide had been systematically studied by replacing Fe with other transition metals. The iron-containing spinel oxides are expected to be promising sensing material for gas sensors due to their rich elements and excellent activity.
查看更多>>摘要：? 2022 Elsevier B.V.ZIF-8 has excellent antibacterial potential as an important metal organic framework (MOFs) photocatalytic material. However, ZIF-8 is greatly restricted in photocatalytic antibacterial applications due to the wide band gap and only response to ultraviolet light. In this work, the spectral response of ZIF-8 is successfully extended to the visible light region by the thermal gas sensitization treatment technology. Meanwhile, the forbidden band width of the materials is narrowed by about 47%. The results of FTIR, XPS and EDS prove that the elements and functional groups in ZIF-8 have changed, indicating the completion of the thermal gas sensitization reaction. The results of XRD and SEM show that the modification process doesn't change the crystal structure and morphology of ZIF-8; The result of BET demonstrates that the specific surface area of ZIF-8 decreases slightly after sensitization, but it is still as high as about 1500 m2/g. Photocatalysis studies indicate that the photo-generated charge separation and transfer efficiency of ZIF-8 improve significantly and the recombination reduce substantially after thermal oxygen sensitization. Photocatalytic antibacterial performances reveal that ZIF-8 after thermo-oxygen sensitization can rapidly produce active species such as·O2- and h+ under visible light irradiation, and the bactericidal efficiency exceed 99% against Escherichia coli and Staphylococcus aureus within 20 min. This research provides scientific basis and experimental data for the application of ZIF-8 in microbial management and health protection.
查看更多>>摘要：? 2022 Elsevier B.V.The widespread use of ionizing radiation in our lives in various fields has led to an increased demand for effective methods of reducing its risks. The investigation of non-toxic, cost-effective, and high-efficiency attenuation materials for radiation protection is developing as a required approach to solving the harmful effect of gamma radiation. In this study, three kinds of YBCO ceramic mixed with transition metal oxides M3O4 (where M=Co, Mn) have been proposed to evaluate their radiation shielding performances. The three ceramics were successfully prepared by the solid-state reaction route. The ceramic composites were examined by XRD and UV–Vis spectrometer techniques for structural and optical properties. The value of the crystallite size D was found to be 39.21 nm, 26.20 nm, and 25.88 nm for Y/Co, YCo/Co, and YMn/Mn ceramic composites, respectively. The porosity percent is minimal for YCo/Co ceramic composite (3.61%) compared to the other prepared ones. The radiation shielding parameters were experimentally measured. YCo/Co sample has the lowest transmitted factor, which indicates that it is the best attenuator. The linear attenuation coefficient for the prepared composites was also determined and the maximum LAC is observed at 0.356 MeV (with an average value of 0.7 cm?1). The tenth value layer was also evaluated and according to this parameter, we need a layer of about 3 cm to attenuate the photons with the energy of 0.356 MeV, and a layer of 5 cm to attenuate 90% of the intensity of the photons with energy of 0.662 MeV. Based on these results, it can be concluded that the current ceramic composites have a promising future for their use as shielding materials against low-energy radiation.
查看更多>>摘要：? 2022 Elsevier B.V.The erbium (Er)-alloyed Sb2Te3 phase-change material has recently been found to enable fast writing speed and high data retention due to the Er-stabilized precursor and the formation of coordinate bonds between Er and Te. However, the detailed characteristics of binary alloys about Er-Sb-Te system are still missing. In this work, Er-alloyed Sb/Te binary material are investigated. The Er20Sb80 compound we designed allows a ultra-fast writing speed of 0.7 ns in the conventional PCRAM device, and the Er13Te87 also can be switched under 50 ns. The impurity Er improves the ability of forming the amorphous structure of Sb/Te, and this stems from the strong Er-Sb and Er-Te bonds stabilize glassy states. Our study demonstrates the device performance of Er-alloyed Sb/Te binary phase-change material, and the origins of these improved performance are also explained by the microscopic observation and molecular dynamics simulation.
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