查看更多>>摘要：? 2022 Elsevier B.V.Supercapacitors are promising energy storage systems as they offer high cycle stability and high-power density. However, mechanical, and electrochemical stability of the materials especially at high energy rates are the keys to be addressed. In this study, nanocomposites of molybdenum trioxide MoO3 (Mo) and graphene nanosheets (G) besides with carbon nanotube (CNT) were reported as mechanically stable new electrodes for practical use in devices. A low cost, non-aqueous bio-based gel electrolyte (Glycerol, (Gly)/KOH) was used to highlight the electrochemical stability as well as safety. Supercapacitors containing G-Mo20 and CNT-Mo20 electrodes provided an optimum specific capacitance of 474 F g?1 and 468 F g?1, respectively which is at least 4.5 times enhancement compared to carbon-based device. Additionally, the G-Mo20 and CNT-Mo20 devices provided specific energy of 46 Wh kg-1 and 37 Wh kg-1 at a specific power of 280 W kg-1 and 270 W kg?1, respectively. The supercapacitor with G-Mo20 and CNT-Mo20 successfully completed 17,500 charge-discharge cycles, with a capacitance retention efficiency corresponding to 93% and 88% after 30 days. Furthermore, the supercapacitor (diameter of 1.8 cm2) with the electrode G-Mo20 was successfully operated the LED light. A facile fabrication method, flexibility, robustness and safety are the advantages for the devices that can be suggested for wearable electronics.
查看更多>>摘要：? 2022 Elsevier B.V.Thin-film sensors have great advantages over bulk sensors in high-temperature applications, such as non-disturbance and fast response. However, oxidation at high temperatures affects their reliability and could even destroy the sensors. Anti-oxidative coatings or environmental barrier coatings (EBCs) can be used to protect the sensors from oxidation at high temperatures. In this study, a thin-film anti-oxidative coating based on polymer-derived ceramics (PDCs) is proposed. By using a direct-writing technique, the coating was applied to a PDC thermistor, and its electrical resistance was measured from room temperature to 800 °C. The resistance of the thermistor coated with the anti-oxidative coating remained virtually constant throughout four consecutive test runs at temperatures of up to 800 °C. The maximum relative standard deviation of the four runs of the resistance-temperature test data was 5.3%, which is one-third that of the thermistor without anti-oxidative coating. The results indicate that the coating can protect the thin-film thermistor from being oxidized at temperatures ranging from room temperature to 800 °C. The mechanism of anti-oxidation of the coating is that a layer of B2O3 forms on the surface of the coating, which prevents the oxygen from diffusing into the coating at high temperature. The coating provides a simple way of producing coatings for high-temperature applications.
查看更多>>摘要：? 2022 Elsevier B.V.Ultrasonic vibration (UV) is capable of improving material flowability and surface quality of products, thus the UV-assisted micro-forming process has become a fascinating technology for fabricating micro-parts. However, when the part is downscaled to the submillimeter level, the rheological behavior of the material during UV-assisted plastic deformation will be significantly affected by the ultrasonic and size effects, which are still not well understood. Meanwhile, the rheological behavior and microstructure evolution of advanced multi-component alloys under UV-assisted deformation are unclear. In this research, a set of UV-assisted micro-compression tests and characterization tests were carried out to investigate the role of grain size, geometrical dimension, and sound energy density on the rheological behavior and microstructure of CoCrFeMnNi high-entropy alloy (Cantor alloy). The results showed that Cantor alloy exhibits an unusual acoustic residual softening (ARS) phenomenon, which is related to the alleviation of severe lattice distortion effect and the increase of stacking fault energy during the UV. The value of ARS is not only related to the sound energy density but also affected by the grain size and geometrical dimension. Furthermore, mathematical models were developed to quantitatively characterize the ultrasonic softening (US) and ARS. The model evaluation showed that the proposed model can well predict the influence of grain size, geometrical dimension, and sound energy density on US and ARS. These findings provide a fundamental understanding for the UV-assisted micro-forming of Cantor alloy.
查看更多>>摘要：? 2022 Elsevier B.V.The CoCrFeNiMo eutectic high entropy alloy (EHEA) was fabricated successfully by directed energy deposition (DED). The microstructure and mechanical properties of the CoCrFeNiMo EHEA samples were investigated in this work. Interestingly, the different microstructure morphology and phase composition were shown from bottom to top along the building direction. The seaweed eutectic structure, herringbone-like hierarchical eutectic structure and irregular lamellar structure were observed at the top, middle and bottom parts, respectively, which was due to changes in temperature gradients caused by increasing deposition height. The dominant phases in the CoCrFeNiMo EHEA samples were FCC, σ and μ phases. The FCC phase alternated with the σ phase, and μ phase particles were precipitated from the fringes of the σ phase. Moreover, the CoCrFeNiMo EHEA samples by DED achieved high hardness (658.44 HV) and high wear resistance (the friction coefficient (COF) is 0.586), which were guaranteed by the intermetallic compounds and fine eutectic lamellar structure.
查看更多>>摘要：? 2022 Elsevier B.V.Novel perovskite-type A-site calcium-doped Nd1–xCaxBaCo2O5+δ oxides were studied in terms of oxygen electrode materials for reversible solid oxide cells (RSOCs). The electrode of x ≤ 0.2 was composed of a tetragonal perovskite structure with a P4/mmm space group. A Ca2+ dopant was used to improve the thermal expansion coefficient (TEC), conductivity, and electrochemical properties of the NdBaCo2O5+δ oxides, with TEC and conductivity values of Nd1–xCaxBaCo2O5+δ (x = 0–0.2) of 17.5–16.2 × 10?6 K?1 and 960.4–1068 S cm?1, respectively. The X-ray photoelectron spectroscopy results indicated that Ca2+ doping has a beneficial influence on the surface oxygen adsorption properties and the increase in the concentration of Co4+. On the basis of the first-principles density functional theory, doping with Ca2+ leads to easier oxygen release and uptake. The area specific resistance of the x = 0.2 electrode was 0.058 Ω cm2 at 700 °C, whereas at 800 °C, the cell using the x = 0.2 oxygen electrode exhibited a maximum power density of 740 mW cm?2 when H2 was used as the fuel, and the current density of the electrolytic pure CO2 at 1.5 V was 1.68 A cm?2. These attractive electrochemical properties suggest that Ca-based doping is an effective method for developing (reversible solid oxide cell) RSOC oxygen electrodes.
查看更多>>摘要：? 2022 Elsevier B.V.The oxidation behaviors of Fe-3.0 wt%Si non-oriented electrical steel were studied in the high-purity Ar, compressed dry air, Ar-H2O mixed, and Air-H2O mixed atmosphere when annealed at 1200 °C for 200 min. The oxide layers generation and transformation mechanism of electrical steel during the high-temperature annealed process was characterized and discussed systematically by means of the XRD, SEM, EDS, and XPS analysis methods. Under compressed air conditions, only O2 participates in the oxidation reaction. And the oxide layer has a typical three-layer structure. The oxidized particle layer only could be observed in the H2O-containing atmosphere, and the particle size and morphology of the oxide layer present an obviously evolution process. During the oxidation reactive process between Fe, Si and O, H2O and O2 could play a synergistic effect. In addition, this synergistic effect leads to the cross-wrap structure appearing between the oxidized particle layer and the outermost oxide layer. The oxide layer thickness increases significantly in the Air-H2O atmosphere because of above conditions. This research lays the groundwork for a more in-depth investigation of silicon steel oxidation behavior.
查看更多>>摘要：? 2022 Elsevier B.V.Although hafnium oxide-based resistive switching (RS) devices have been explored extensively, extremely high operating voltages and currents hinder their application in low power operations. In this study, the growth temperature and annealing conditions have been varied to significantly improve the characteristics of hafnium oxide-based RS devices. Deposited using a rf magnetron sputtering at different temperatures, HfOx films are subsequently subjected to vacuum annealing to create a high density of oxygen vacancies. It is observed that the crystallinity, defect density, and RS device performance of these films are influenced by these thermal treatments. The HfOx film annealed at 450 oC exhibited bipolar RS with the substantial improvement in the device performance, such as electroforming, set/reset voltages, and operating currents as low as ~1 V, 0.5/? 0.5 V, and ~1 μA, respectively, in addition to large ON/OFF ratio> 103, good endurance (>103 cycles), and retention capability (>104 s). The localized conductive filaments composed of oxygen vacancies are found to be responsible for the RS behavior in Al/HfOx/FTO devices, and the simple vacuum annealing approach considerably increases the proportion of oxygen vacancies. With the insights into the influence of annealing temperatures on the switching parameters, this work paves the way for the design of low-power devices for data storage applications.
查看更多>>摘要：? 2022 Elsevier B.V.SeS2 possesses the combined merits of S and Se with considerable capacity and high electronic conductivity, but is still hindered by a shuttle effect of lithium polysulfides/polyselenides and sluggish conversion kinetics. Herein, high–efficiency heterogeneous Ni2P/CoP catalysts implanted into MOF–derived carbon arrays (Ni2P/CoP@NC) are developed to simultaneous immobilize polysulfides/polyselenides and regulate their conversion. The Ni2P/CoP catalysts with hollow and hierarchical structures extremely expose abundant catalytic and adsorption sites for LiPS/LiPSe conversion reaction. Meanwhile, the strong chemical binding of Ni2P/CoP towards LiPSs/LiPSes through Ni–S, Ni–Se, Co–S and Li–P bonds favors for the regulation of polysulfide/polyselenide conversion. The DFT calculation results corroborate the heterogeneous Ni2P/CoP interface provides depressed lithium–ion diffusion barriers to promote the polysulfide/polyselenide conversion kinetics. Benefiting from abundant catalytic and adsorption sites, strong chemical binding towards LiPSs/LiPSes and depressed lithium–ion diffusion barriers, the Ni2P/CoP@NC catalysts enable considerable specific capacities, superior rate performance and stable cycling performance for Li–SeS2 batteries.
查看更多>>摘要：? 2022 Elsevier B.V.The oxidation behavior of Fe-Mn-Cr-Al-Si medium manganese austenitic steel and the effect of high-temperature oxidation on the subsurface microstructure and magnetic properties were studied. When the oxidation temperature is relatively low (800 °C and 900 °C), the oxide layer is mainly composed of Mn oxides, Fe oxides, and Mn-Cr spinel. On the other hand, at the oxidation temperature of 1000 °C, the outer oxide layer consists of Fe2O3, Mn2O3, Fe3O4, and Mn3O4, while the inner oxide layer is composed of Mn-Cr, Fe-Cr, Mn-Al, and Fe-Si spinel. A thin ferrite layer (less than 6 μm) is formed in the subsurface of the samples oxidized at 800 °C and 900 °C. However, in the subsurface of the sample oxidized at 1000 °C, a thicker martensite layer (over 100 μm) is also observed besides the ferrite layer with thickness of about 10 μm. VSM results show that the samples oxidized at 800 °C and 900 °C exhibit paramagnetic behavior attribute to the relatively thin oxide and ferrite layer. However, the sample oxidized at 1000 °C exhibits soft magnetic property due to the much thicker oxide and BCC layer.
查看更多>>摘要：? 2022 Elsevier B.V.The aim of the current study was to optimize the mechanical properties and thermal shock resistance of plasma-sprayed LaPO4/8YSZ coatings with thickness of 1 mm based on a modified Vickers indentation method. As the LaPO4 content increased from 1 wt% to 30 wt%, the increasing porosity of the composite coatings led to the decrease of bonding strength of the coatings from 8.43 ± 0.29 MPa to 6.08 ± 0.12 MPa, while residual stress and fracture toughness of the composite coatings exhibited an increased tendency. Although the bonding strength of LaPO4/8YSZ coatings was lower than that of 8YSZ coating (11.49 ± 0.19 MPa), the minimum residual stress of -(51.83 ± 3.38) MPa for the coating with LaPO4 content of 1 wt% was obtained, further resulting in the maximum thermal cycling lifetime of 5340 ± 49 cycles during thermal shock test at 900 °C. Correspondingly, thermal shock resistance was strongly dependent on the microstructure and mechanical properties of LaPO4/8YSZ coatings with the addition of nano-LaPO4 particles.
NSTL
Elsevier