查看更多>>摘要：? 2022 Elsevier B.V.Developing electrode materials with high specific capacitance within both positive and negative potential window is an effective way to obtain aqueous supercapacitors with high energy density. In this work, P doped Fe-Co-S binary metal sulfides (Fe-Co-S/P) was demonstrated to show high specific capacitance within a wide potential window from ? 1–0.55 V. When used as cathode, it exhibited a specific capacitance of 0.8 F cm?2 (320 F g?1). After 20,000 cycles at 20 mA cm?2, it even increased to 242.3% of the initial capacitance. When used as anode, it also had a specific capacitance of 1.34 F cm?2 (536 F g?1) and satisfied cyclic performance (71.4% of the initial capacitance after 20,000 cycles). Moreover, the symmetric supercapacitors (SSCs) assembled with the Fe-Co-S/P electrodes delivered high energy density of 106.42 Wh kg?1 at a power density of 800 W kg?1 and exhibited excellent cyclic stability by preserving 93.9% of the initial capacitance after 5000 cycles. This work not only establishes Fe-Co-S/P as a high-performance supercapacitor electrode material, but also provides a new strategy to design and construct high-performance aqueous SSCs.
查看更多>>摘要：? 2022 Elsevier B.V.We experimentally found that FeCo21.5Cr0.2Ni0.8 alloy quenched from 500 °C, slightly above the order-disorder transition temperature, surprisingly exhibited an extreme impact brittleness. Impact fracture morphology observed by scanning electron microscope (SEM) showed that the impact brittleness was caused by the fast crack growth and poor local plasticity. Short-range ordered (SRO) structures were found in the sample quenched from 500 °C by high-resolution transmission electron microscope (HRTEM) characterizations, and the average SRO size is ~1.58 nm. We contribute the impact brittleness to the formation of SROs. Molecular dynamics (MD) simulations were carried out to reveal the SRO-induced embrittlement mechanism caused by fast crack propagation under high-speed loading. MD simulations showed SROs significantly inhibited the deformation plasticity near crack tips by suppressing the dislocation proliferation, dislocation slip, and twinning. Generalized stacking fault energy (GSFE) curves were calculated to evaluate the effect of SROs on antiphase boundary (APB) energies, unstable stacking energy γusf, and intrinsic stacking energy γisf. SROs were found to prominently increase the APB energies and [Formula presented], fully supporting the SRO-induced poor dislocation and twinning plasticity near crack tips in MD simulations. These findings revealed the potential SRO-induced impact brittleness and its embrittlement mechanism, and provide a design consideration for the engineering application of materials under impact loading.
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