查看更多>>摘要：? 2022Flexible supercapacitors have attracted great attention owing to some advantages of flexibility, light weight and high-power output, and have displayed enormous potential in wearable electronic devices. However, the hydrogel electrolyte in flexible supercapacitors usually shows insufficient mechanical properties and low ionic conductivity under harsh environments, making it unsatisfactory for practical applications. Herein, a novel polyacrylamide/montmorillonite/ionic liquid-Li2SO4 hydrogel electrolyte with wide temperature tolerance, high ionic conductivity and super-stretchable ability is prepared via facile thermally initiated radical polymerization. The layered montmorillonite can not only improve the thermal stability of the hydrogel, but also form a conductive channel to promote the rapid transport of ions. Moreover, the introduction of ionic liquid into the hydrogel can further increase the working temperature range. In consequence, the polyacrylamide/montmorillonite/ionic liquid-Li2SO4 hydrogel electrolyte exhibits outstanding stretch ability (tensile strain over 1000%), high ionic conductivity (41.7 and 50.7 mS cm-1 at 25 °C and 40 °C, respectively). In addition, supercapacitor with the polyacrylamide/montmorillonite/ionic liquid-Li2SO4 hydrogel electrolyte has good electrochemical property within the wide temperature tolerance from ? 10–80 °C.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, MgAl2O4-MgAlON composites with Al, α-Al2O3, MgO and MgAl2O4 raw materials were fabricated through in-situ nitriding and reaction sintering, with a tunable MgAlON composition from 10 wt% to 25 wt%. Subsequently, the sintered samples were calcined at 1500 ℃ for 3 h in an oxidation atmosphere. The densification, mechanical properties, phase assemblage, microstructures, and oxidation behaviors of MgAl2O4-MgAlON composites were investigated. Results reveal that the MgAlON grains were well-crystallized and exhibited a spinel structure in sintered body. The mechanical properties were markedly improved with the increase of MgAlON mass fraction and reached the maximum at 25 wt%. After oxidation, the densification and mechanical properties have both declined, despite the composites were oxidized to a core-shell structure. Additionally, the weight gain rate and linear expansion rate of oxidized samples simultaneously exhibited a gradual rise with the increase in MgAlON contents. More specifically, the MgAlON grains were transformed into many submicron MgAl2O4 and α-Al2O3 grains with particle sizes< 1 μm after oxidation, while the oxidation reaction was carried out along the particle gaps created by MgAlON grains oxidized from surface to interior. Our findings provide some scientific guidance for enhancing the oxidation resistance and application potentials of MgAlON composites in high-temperature.
查看更多>>摘要：? 2022 Elsevier B.V.Colloidal CsPbBr3 perovskite quantum dots (PQDs) have substantially improved modern optoelectronic applications, including solid-state lighting, thanks to their highly pure and intense green light emission. However, some drawbacks including lead toxicity, poor stability, and difficulties in emission color tuning hinder their practical applications. Herein, ultra-stable Eu3+/Dy3+ co-doped CsPbBr3 PQD glass nanocomposites (GNCs) with tunable color emissions from green to red and then white are synthesized via melt-quenching followed by heat-treatment method to be used in white light-emitting diodes (WLEDs). Eu3+ and Dy3+ ions are selected to overcome the color tunability obstacle of PQDs and to obtain phosphor-free white light emission with enhanced CRI values. The photoluminescent performance of GNCs is shown to be reversible at elevated temperatures and remains stable even in water. Ultimately, a prototype WLED is constructed by coupling a selected Eu3+/Dy3+ co-doped CsPbBr3 PQD GNC on top of a 400 nm-emitting LED chip to demonstrate its superior optical performance with a color rendering index of 78 and correlated color temperature of 5436 K. The developed GNCs with long-term stability, and excellent tunable luminescent properties may overcome the commercialization barriers of CsPbBr3 PQDs for WLED applications.
查看更多>>摘要：? 2022 Elsevier B.V.The 2D antimonene and graphyne monolayers have been intensively studied due to their unique physical, electronic and chemical properties. In this work, a novel antimonene/graphyne (Sb/Gy) vdW heterostructure has been designed and investigated to explore the 2D/2D hybrid effects on electronic and interface properties by the first-principle calculations. The results indicate that the Sb/Gy vdW heterostructure displays small lattice mismatch, superior thermodynamic stability and semiconductivity with a staggered type-Ⅱ band alignment. The band structure of the Sb/Gy vdW heterostructure can be modulated by external vertical electric field, which undergoes transition from indirect to direct semiconductor under positive external vertical electric field. Furthermore, an interesting transformation from type-II to type-III band alignment is observed upon the applying of negative electric field. These findings can provide a good guidance for the applications of the Sb/Gy vdW heterostructures for nanoelectronic and optoelectronic devices.
查看更多>>摘要：? 2022 Elsevier B.V.Using atomic layer deposition and high-temperature annealing to fabricate coatings for Fe-6.5 wt%Si powder reduce the hysteresis losses of the resultant composites drastically without sacrificing the permeability properties, and keep the eddy current losses at a relatively low value. The core loss of annealed FeSi SMCs is 39.67% lower than that of composites prepared using raw Fe-6.5 wt%Si powder, meanwhile the permeability remains at relatively high value (at B = 100 mT, f = 50 kHz). The decreasing of the core loss is mainly attributed to hysteresis loss reduction caused by grain growth. And the low eddy current loss is guaranteed by the uniform, complete, compact coating layer formed the surface of FeSi particles, which transforms to a protective and insulating layer containing silicate and metal oxide after annealing. On the premise of ensuring the integrity of the insulation layer, the annealing temperature of powder is significantly increased by surface modification, so as to reducing the hysteresis loss meanwhile controlling the eddy current loss.
查看更多>>摘要：? 2022 Elsevier B.V.The present work investigated the effect of Sn on the microstructure, hardness, and tribological behaviors of CoCrFeNi high entropy alloys fabricated via vacuum arc melting. The results showed that Sn addition in CoCrFeNi alloys led to a distinct structure change from single FCC to dendritic microstructure in which Ni3Sn2 phase was distributed between the FCC dendrites. With the increase in Sn content, the volume fraction of Ni3Sn2 phase increased and thus brought about the improved hardness due to the second phase strengthening. The friction and wear test indicated that the best tribological performance was achieved by Sn1 alloy under a load of 2 N (the friction coefficient and wear rate were as low as 0.21 and 2.7 × 10?5 mm3/N?m, respectively), which was attributed to the competitive effect between the applied load and Sn content. Moreover, the wear mechanisms of CoCrFeNiSnx alloys during sliding were carefully discussed.
查看更多>>摘要：? 2022 Elsevier B.V.Li metal anode has been considered as the most promising anode due to its high theoretical capacity and low redox potential. However, uncontrollable Li dendrites growth during Li deposition seriously shortens lifetime of Li metal anode. CNTs films have been regarded as the 3D frameworks for suppressing Li dendrites growth, whereas a relatively high density of CNTs film leads to Li depositing on the top of CNTs film, giving rise to lower efficiency of CNTs films. In this regard, PCF/Z-67 film is prepared by vacuum filtration of toruloid ZIF-67@CNTs on the separator. The film is auto-transferred to the surface of Li metal anode during cycling. The ZIF-67 nanoparticles increase the interspace of film, providing more space to accommodate deposited Li. Besides, the lithiophilic functional groups in the ZIF-67 are conducive to lower nucleation barrier of Li. At a current density of 1 mA cm?2, the Li||Li symmetrical cell consist of Li@PCF/Z-67 foil can cycle stably for more than 1000 h with a hysteresis voltage of 8 mV, due to the synergistic effect of CNT and ZIF-67. The coulombic efficiency of the cell with PCF/Z-67 can stabilize at 95% under a current density of 1 mA cm?2 after 200 cycles. In addition, Li@PCF/Z-67||LiFePO4 full cell delivers outstanding rate capacity and cycling stability compared with Li foil. The results demonstrate that the 3D porous framework assembled with ZIF-67@CNTs is an available strategy to enhance the electrochemical properties of Li metal anodes.
查看更多>>摘要：? 2022A novel soft magnetic composites (SMCs) was prepared by Fe-6.5 wt%Si/nano-MnZn ferrites composite powders in this work. The nano-MnZn ferrites (~ 20 nm) were synthesized by thermal decomposition method. The microstructure and electromagnetic characteristics of Fe-6.5 wt%Si/nano-MnZn ferrites SMCs were investigated in details. The results showed that the effective permeability increased firstly and then decreased with increasing nano-MnZn ferrites contents from 0 to 4 wt%. Moreover, appropriate added amounts of nano-MnZn ferrites can reduce the hysteresis losses of the SMCs. The SMCs with 2 wt% nano-MnZn ferrites and annealed at 400 ℃ have the optimum comprehensive performances with effective permeability of 142.2 (increased by 47%), total core losses of 816 mW/cm3 (decreased by 12%) and acceptable electrical resistivity of 3.18 Ω·cm.
查看更多>>摘要：? 2022 Elsevier B.V.The microstructures, mechanical properties and tribological behaviors in a wide temperature range of high velocity oxygen fuel sprayed CoMoCrSi coatings before and after 800 °C-annealed treatment were comparatively investigated. Particularly, the annealed CoMoCrSi coatings registered well crystallization, improved microstructures and enhanced properties compared to the as-sprayed coatings. Specially, the surface microhardness increased by 13.3%, and the adhesive strength increased by 12.5% after the annealed treatment. Moreover, a compact oxides layer comprising Cr2O3, Co3O4, MoO3 and CoMoO4 formed on the annealed coating surface, which could be account for the increased microhardness and excellent tribological behaviors of the annealed coatings. The annealed coatings registered lower friction coefficients and wear rates than the as-sprayed coatings in a wide temperature range. Consequently, the 800 °C-annealed treatment could significantly improve the microstructures and properties of the HVOF-sprayed CoMoCrSi coatings. Moreover, the annealed CoMoCrSi coatings could be a well candidate for the abrasion-resistant material in a wide temperature range.
查看更多>>摘要：? 2022 Elsevier B.V.Asymmetric fiber-shaped supercapacitors (FSCs), especially those using pseudocapacitive materials, have been considered one of the most promising candidates for high-performance electrochemical devices. Herein, we design a flexible, asymmetric FSC consisting of carbon fiber (CF) as the substrate, multiple and alternate Ni-Co layered double hydroxide/mono-dispersed carbon nanotube (CNT) coaxial layers ([Ni-Co LDH-x/CNT-y]@CF) as the positive electrode materials and tremella-derived activated carbon@CF (TDC-z@CF) as the negative electrode material. The 3D Ni-Co LDH/mono-dispersed CNT networks enable the high mass loading of active materials, fast electron transfer, efficient ion diffusion, and mechanical stress release. TDC-z possesses large surface areas with hierarchical porous structures, thus demonstrating high capacitive performance. Based on that, the resulting FSC achieves a remarkable energy density of 26.20 Wh kg?1, a power density of 7569.23 W kg?1, and a superior cycling stability of 112.5% over 5000 cycles at a current density of 5 A g?1. Several supercapacitors connected in series can also drive a portable LED device for over 10 min. Furthermore, the assembled device also exhibits excellent mechanical stability under various deformation conditions. These appealing properties make our FSCs an attractive candidate for powering wearable and flexible electronic devices.
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