Two-dimensional hierarchical structures of transition metal selenides with more active sites and shorter electrolyte diffusion channels hold great potential for application in supercapacitors. A lamellar array electro...
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Two-dimensional hierarchical structures of transition metal selenides with more active sites and shorter electrolyte diffusion channels hold great potential for application in supercapacitors. A lamellar array electrode composed of well-patterned CoSe2 nanoparticles, using leaf-like ZIF-67 as a precursor, is successfully fabricated by a two-step calcination method. Primarily, the cobalt selenide particles were anchored to the carbon skeleton, as to obtain lammellar array and keep stable in electrochemical measurements. The novel CoSe2/carbon (CoSe2/ C) electrode shows excellent electrochemical performance, with a specific capacitance of 462 F g-1 at a current density of 5 A g-1, and a 100% capacitance retention at 10 A g-1 after 10,000 cycles. Meanwhile, an asymmetric supercapacitor is assembled and it exhibits an energy density of 20.6 Wh kg- 1 with a power density of 698.8 W kg- 1 and an outstanding cycling stability. Concisely, benefiting from the effective method of controllable morphology, we construct the lamellar array composed of CoSe2 particles, and confirm it is of great potential in application for stable supercapacitors.
We present a novel method to control the rebounding behavior of small mm-sized solid balls by employing magnetoactive elastomers (MAEs) with microstructured surfaces. An MAE is a composite material consisting of mu m-...
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ISBN:
(纸本)9780791888322
We present a novel method to control the rebounding behavior of small mm-sized solid balls by employing magnetoactive elastomers (MAEs) with microstructured surfaces. An MAE is a composite material consisting of mu m-sized ferromagnetic particles dispersed in a soft elastomer (e.g., polydimethylsiloxane) matrix. In the act of rebounding, the ball hits an MAE surface and bounces back. The MAE samples contained 75 wt.% of iron. This composite material is known to respond to an applied magnetic field with increased stiffness (due to the magnetorheological effect) and plasticity. To adjust the rebound properties, the top layer of the MAE material was additionally modified by micromachining lamellar structures with different dimensions on the 100 mu m scale via laser ablation. Due to the resulting high aspect ratio, these surface structures were sensitive to the magnetic field direction. The lamellas could stand up straight or lay down flat. The rebound behavior was evaluated by using a custom build apparatus that facilitates dropping of the balls in a precise and repeatable manner. A ball was dropped from different heights. The ball trajectory was captured with a high-speed camera to investigate the rebound properties. The recorded video was processed using a custom software written in Python. The experimental procedure and data processing algorithms are presented in detail. The results for the samples with different geometrical dimensions are provided as examples. It is made evident that the magnetic field influences the rebound properties of small non-magnetic balls impinging microstructured MAE surfaces. The change in surface topography is an effective way to control the ball rebound. The fabrication flexibility in geometrical dimensions of surface microstructures opens a convenient way to tune the desired response to magnetic fields. The presented idea may find applications in impact mitigation or small-scale sorting machinery, e.g. for recycling.
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