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Due to its atomically ultrathin morphology and superior optoelectronic properties, graphene has been broadly studied and utilized in phototransistors, photoconductors, or heterojunction nanostructures. However, in practical devices, the disadvantages of graphene should be concerned for its high dark current, very low on/off ratio, and high-priced fabrication cost. We report the photodetecting of the graphene/insulator/silicon heterojunction. The insulator layer is optimized to achieve balanced optoelectronic properties in terms of an Iph/Idark ratio of 4.17 × 103, a responsivity of 35 mA W−1, and a detectivity of 6.39 × 1010 Jones at a wavelength of 658 nm, with low operating voltage and static power dissipation (0.84 nW). Besides, response speed and degradation in the environment are tested. The mechanisms are revealed and analyzed by I-V measurements. [ABSTRACT FROM AUTHOR]

Ultra-broadband high-performance photodetectors (PDs) are promising for diverse applications such as communication, imaging, environmental monitoring, and sensing. However, many PDs currently face issues of slow response speed, low sensitivity, poor air stability, and high energy consumption. In this work, we demonstrate a self-powered, broadband, and polarization-sensitive PD based on a ternary transition metal chalcogenide Nb2Pd3Se8 single crystal. The generation mechanism of photocurrent (PC) was confirmed by photoresponse measurements related to laser power and temperature. The Nb2Pd3Se8-based PD exhibits the maximum responsivity of 2.74 mA W−1 and a detectivity of 4.73 × 106 Jones with a 55–60 ms response time at 532 nm and high stability under ambient conditions over 6 months. Broadband detection capabilities from 365 nm to 10.6 μm are tested experimentally. Moreover, a strong polarization-sensitive PD with an anisotropic ratio of 1.42 is achieved. This work exhibits the enormous potential of Nb2Pd3Se8 for ultra-broadband, self-powered, polarization-sensitive, and air-stable PDs. [ABSTRACT FROM AUTHOR]

Fluoroelastomer (FKM) has been widely used in aerospace and some particular fields, whose aging is a key problem to influence the service life of the systems. The aging behaviors of FKM in the lubricating oil have been investigated in our previous study. In this work, the influence of intentionally aged or oxidized lubricating oil (A‐O) on the aging process of FKM is reported for the first time comparing with the situation in the fresh oil (F‐O). As the oil medium aged at 200°C for different time, its color, acid number and contact angle with FKM change evidently indicating possible oxidation might occur although the Fourier transform infrared spectrometer (FTIR) has little change. Then, the influence of aged oil medium on the aging behaviors of FKM was further examined. Compared with F‐O, the aging process of FKM in A‐O was significantly accelerated as evidenced by FTIR, tensile strength, mass change, DMA, and macroscopic observation. With the increase of aging temperature from 150 to 200°C, the contrast between A‐O and F‐O conditions become more prominent. Specifically, at 200°C, the crosslinking density and tensile strength of FKM in A‐O decreased by 2.2 × 10−4 mol/cm3 and 2.5 MPa compared to that in F‐O, and the mass change reached to 3.8%, which might be due to the higher amount of oil medium by diffusion into the FKM matrix. [ABSTRACT FROM AUTHOR]

Epoxy resin (EPR) insulations play a vital role in the insulation of modern power electronic equipment owing to their excellent dielectric properties. However, due to the high‐power density and miniaturization of power equipment which causes high heat fluxes under high voltage and high‐frequency stresses, EPR with good thermal and insulation properties is urgently needed. In this study, the polydopamine functionalized micro‐BN and core‐shell nano TiO2–SiO2 particles are dispersed in EPR to simultaneously improve thermal and dielectric insulation properties. It is revealed that the addition of micro‐nano particles significantly improves the thermal and dielectric performance. Particularly, the high thermal conductivity of micro‐BN and the dielectric barrier effect due to the core‐shell structure of nano TiO2–SiO2 are the main reasons for improved thermal and dielectric insulation performance, respectively. The EPR composite containing 3 wt% of micro‐BN and 1 wt% of nano TiO2–SiO2 exhibits the optimal performance with 0.49 W/mK thermal conductivity and the highest dielectric strength among all the samples, that is, 60.61 kV/mm even at 10 kHz and 90°C. This study found that the crucial factors are the surface encapsulation, weight percent, and homogeneous dispersion of particles in EPR, the dielectric barrier effect, thermal conductivity, and the mismatch between the dielectric constant of EPR and particles. This study proposes the optimal weight percent of suitable micro‐nano particles for EPR to produce suitable composites for high‐frequency and high‐temperature applications. [ABSTRACT FROM AUTHOR]

MoS2 is considered as an ideal electrode material in the field of energy storage due to high theoretical specific capacity and unique layered structure. However, limited interlayer distance and poor intrinsic electrical conductivity restrict its potential real-world application. Herein, an alternately intercalated structure of MoS2 monolayer and N-doped porous carbon (NC) layer is grown on reduced graphene oxide (rGO) via a chemical intercalated strategy. The expanded interlayer distance of MoS2 (0.96 nm), enlarged by the intercalation of N-doped porous carbon layers, can enhance ion diffusion mobility, provide additional reactive sites for ion storage and maintain the stability of electrode structure. In addition, the hierarchical structures between rGO substrate and intercalated N-doped carbon layers construct a three-dimensional (3D) conductive network, which can significantly improve the electrical conductivity and the structural stability. As a result, the rGO-supported MoS2/NC electrode exhibits an ultrahigh reversible capacity and remarkable long cycling stability for sodium-ion batteries (SIBs) and potassium-ion (PIBs). Meanwhile, the as-obtained MoS2/NC@rGO electrode also delivers a superior cycle performance of 250 mAh·g−1 after 160 cycles at 0.5 A·g−1 when employed as an anode for sodium-ion full cells. [ABSTRACT FROM AUTHOR]

The differences of the microstructure and mechanical property between metal mould and sand mould cast Mg-10Gd-3Y-Zr alloy were investigated both under as-cast condition and after solution heat treatment. In the as-cast specimens, the microstructure is similar and composed of α-Mg solid solution and eutectic compound of α-Mg+ Mg24(Gd,Y)5; whereas the grain size using metal mould and sand mould is 27 μm and 71 μm, respectively.The eutectic compound of metal mould cast alloy was completely dissolved after solution treated at 500℃ for 8 h, however it needs higher temperature (525 ℃) and longer time (12 h) to achieve the absolute dissolving under sand mould condition. In contrast to metal mould, the peak time of sand mould alloy aged at 225 ℃ and 250 ℃ of was advanced by 4 h and 6 h, respectively. The precipitation reaction sequence in sand mould cast Mg-10Gd-3Y-Zr alloy during isothermal ageing at 250 ℃ follows S.S.S.S.→β″(D019)→β′(cboc)→β1(fcc)→β(fcc), which is similar to that in the alloy cast using metal mould.