Carbon-coated NaCrO2 synthesized via an emulsion method exhibits excellent cyclability and ultrafast rate capability up to a rate of 150 C, demonstrating ideal properties for advanced sodium-ion batteries.
Unlike for SnO, few studies have reported on the use of SnCO as an anode material for rechargeable lithium batteries. Here, we first introduce a SnCO-reduced graphene oxide composite produced via hydrothermal reactions followed by a layer-by-layer self-assembly process. The addition of rGO increased the electric conductivity up to ∼10 S cm. As a result, the SnCO-reduced graphene oxide electrode exhibited a high charge (oxidation) capacity of ∼1166 mAh g at a current of 100 mA g (0.1 C-rate) with a good retention delivering approximately 620 mAh g at the 200th cycle. Even at a rate of 10 C (10 A g), the composite electrode was able to obtain a charge capacity of 467 mAh g. In contrast, the bare SnCO had inferior electrochemical properties relative to those of the SnCO-reduced graphene oxide composite: ∼643 mAh g at the first charge, retaining 192 mAh g at the 200th cycle and 289 mAh g at 10 C. This improvement in electrochemical properties is most likely due to the improvement in electric conductivity, which enables facile electron transfer via simultaneous conversion above 0.75 V and de/alloy reactions below 0.75 V: SnCO + 2Li + 2e → Sn + LiCO + xLi + xe → LiSn on discharge (reduction) and vice versa on charge. This was confirmed by systematic studies of ex situ X-ray diffraction, transmission electron microscopy, and time-of-flight secondary-ion mass spectroscopy.
A three-dimensional compressible Navier-Stokes solver, KFLOW, using overlapped grids has recently been developed to simulate unsteady flow phenomena over helicopter rotor blades. The blade-vortex interaction is predicted for a descending flight using measured blade deformation data. The effects of computational grid resolution and azimuth angle increments on airloads were examined, and computed airloads and vortex trajectories were compared with HART-II wind tunnel data. The current method predicts the BVI phenomena of blade airloads reasonably well. It is found from the present study that a peculiar distribution of vorticity of tip vortices in an approximate azimuth angle range of 90 to 180 degrees can be explained by physics of the shear-layer interaction as well as the dissipation of numerical schemes.
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