As one of the most promising cathode materials for next-generation of lithium-ion batteries, Li-rich Mn-based oxides are still hindered by inferior cycling properties and poor rate performance. ...Surface modification is proved to be feasible to tackle these problems. Herein, we chose phytic acid to construct spinel and Li3PO4 double protection layers on the Li1.2(Ni0.17Co0.07Mn0.56)O2 cathode material via a simple synchronous approach. The 3 wt% phytic acid treated sample achieves markedly enhanced electrochemical performance, such as elevated initial Coulombic efficiency reaching 90.0%, increased capacity retention of 87.8% after 150 cycles at 1 C and alleviated average discharge voltage drop of 1.63 mV per cycle. These impressive electrochemical properties can be ascribed to the designed hierarchical interface, which not only can synergistically retain structural stability but also provide fast Li+ transport channels. Taken together, this work employs a facile and novel route to enhance the electrochemical performance of Li1.2(Ni0.17Co0.07Mn0.56)O2, which may afford inspiration to the commercialization of Li-rich cathode materials.
This paper reviews the work on huge capacity fiber-optic sensing network based on ultra-weak draw tower gratings developed at the National Engineering Laboratory for Fiber Optic Sensing Technology ...(NEL-FOST), Wuhan University of Technology, China. A versatile drawing tower grating sensor network based on ultra-weak fiber Bragg gratings (FBGs) is firstly proposed and demonstrated. The sensing network is interrogated with time- and wavelength-division multiplexing method, which is very promising for the large-scale sensing network.
One method based on the end-face reflection as a reference was used to measure weak grating reflectivity of 0.01%-1%. For measuring ultra-weak grating reflectivity, the grating group with an ...identical wavelength was used. By using anhydrous alcohol and deionized water as the reflecting medium, the single- pulse FBG reflectivity of a highly doped-Ge photosensitive fiber was calculated to be about 0.747% and 0.739%, respectively; and the single-pulse FBG reflectivity of ordinary SMF fiber was about 0.016% and 0.015%, respectively. The consistent results by the two different reflecting media showed that the end-face reflection method on the grating group was feasible.
CdS hollow structures were built up by using the one pot method and using carbon disulfide （CS2） and ethylenediamine as starting materials. CS2 is insoluble in water and could form metastable oil ...droplets in the water at a moderate temperature. The oil droplets formed chains in the circumvolving water. CdS crystals grew and mineralized on the surfaces of the CS2 droplet chains, forming CdS shells around the unreacted CS2 cores. After the surrounding temperature was raised above the boiling point of CS2, the unreacted CS2 cores vaporized, leaving the CdS shelled hollow structures. The CdS hollow structures were characterized by using a transmission electron microscope, an X-ray diffractometer, a UV-Visible spectrophotometer and a fluorescence spectrophotometer. The CdS hollow structures were mainly tubes with closed ends. The exterior diameter and the interior diameter of tubes were about 50 nm and about 15 nm, respectively. Compared with the absorption onset wavelength of the bulk CdS, the CdS hollow structures exhibited a blue shift of about 57 nm. While excited at 213 nm, the CdS hollow structures emitted greenish blue light centered at 470 nm.
•A numerical scheme is proposed for the direct numerical simulation of complex solid-liquid-gas three-phase flows.•A coupled LBM-DEM model ensuring mass conservation is proposed.•The upward migration ...of the bubbles through a brine-filled sediment column is successfully simulated at various conditions.•Simulation results indicate three different flow regimes: connected finger flow, transition flow, and dispersed bubbly flow.•The dimensionless EO and WE numbers can identify the three different flow regimes.
In this paper, we develop a numerical model for simulating the solid-liquid-gas three-phase flow in unconsolidated particle layers. Based on the discrete element method (DEM) and the multiphase fluid model in the framework of the lattice Boltzmann method (LBM), a multiphase fluid-solid two-way coupling algorithm is proposed. In this model, the fluid-fluid interface is tracked using a phase-field method, and the multiphase fluid-particle interaction is tackled by a combination of the momentum exchange method for the flow field and the immersed boundary method for the phase field. We applied the method to simulate the upward migration of the leaked gas bubbles through a brine-filled sediment column at the seafloor, and investigated the influences of the leak flow rate and the interfacial tension on the bubble rising behavior. The results indicate three different flow regimes: connected finger flow, transition flow, and dispersed bubbly flow. These flow regimes can be distinguished by the dimensionless Eötvös and Weber numbers. The proposed numerical method can accurately characterize various multiphase interaction mechanisms at the mesoscopic scale and has powerful advantages in simulating complex fluid-particle coupling problems.
•The first report of fluorescence quenching of MoS2 QDs by Fe3+ ion, to our best knowledge.•The fluorescent MoS2 QDs–Fe3+ sensor operates conveniently and effectively in extremely low ...concentrations.•The fluorescent MoS2 QDs–Fe3+ sensor is label free and has good selectivity.
MoS2 quantum dots were successfully prepared by a one-step hydrothermal exfoliation procedure. The prepared MoS2 quantum dots are monodispersed and have a circular shape, with an average diameter of 4.67 nm. Excited by UV-light, MoS2 quantum dots emit blue-purple fluorescence, and the fluorescence intensity is suppressed with the addition of Fe3+ ions. On this basis a novel fluorescent MoS2 quantum dots–Fe3+ label-free detection system is proposed. The decay curves of fluorescence show that the fluorescence quenching follows a static process. The binding stoichiometry ratio of Fe3+ ions toward MoS2 quantum dots is recognized as 1:1, based on the Benesi-Hildebrand and Job’s plot methods. For the concentration range of 0–50 μmol/L, the Fe3+ and fluorescence intensity are linearly related to 99.39%. The detection limit reaches 1 μmol/L. Several common ions were also examined that have little cross-influence on the fluorescence intensity of the MoS2 quantum dots. The fluorescent MoS2 quantum dots–Fe3+ probe has good performances and provides a novel, convenient and effective approach for the detection of Fe3+ of extremely low concentrations.
We investigate experimentally the effects of pore size, surface wettability, and penetration mode on the characteristics of liquid penetration through meshes. Utilizing the impact of droplets and the ...hydrostatic pressure, we study water penetration through superhydrophobic, hydrophobic, superhydrophilic, and hydrophilic meshes with different uniform radii and pitch values of the pores. In the case of dynamic penetration enabled by the droplet impact, our results show that surface wettability has a negligible effect on either the threshold speed of the droplet penetration or the penetrating liquid mass. The threshold droplet speed is found to be mainly determined by the synergistic effects of global and local dynamic pressures of the impacting droplet, and a modified expression for the threshold droplet speed is proposed. For the quasi-static penetration based on the applied hydrostatic pressure, we find that surface wettability and pore pitch do not affect the penetration threshold pressure but do affect the pressure at which the liquid penetration ceases. This is due to the fact that under quasi-static conditions, the droplet liquid spreads out and merges with that at the adjacent pores on the mesh underside, affecting the wetted area and, hence, the capillary pressure resisting penetration.
In this paper, a lattice Boltzmann method is developed to simulate two-phase flows with soluble surfactants in complex porous media. This method not only can recover the Langmuir adsorption isotherm ...when the bulk surfactant concentration is relatively low but also allows the surfactant concentration to exceed the critical micelle concentration. Thanks to its versatility, this method is used to study the influence of surfactants on steady-state fluid distributions, specific interfacial lengths (SILs), and relative permeabilities under different wetting fluid (WF) saturations (S w) and viscosity ratios (M) of WF to non-WF (NWF). Regardless of the values of S w and M, the SIL between two fluids and the SIL between a grain surface and WF are always higher in a surfactant-laden system than in a clean system, while the SIL between a grain surface and NWF is always lower in a surfactant-laden system. For M = 1, we find that the addition of surfactants dramatically increases the relative permeability (RP) of NWF but slightly decreases the RP of WF. By adjusting M at S w = 0.5, the RP of NWF is always higher in a surfactant-laden system than in a clean system, while the relative magnitude of the WF relative permeabilities in both systems depends on M: for M < 1, the RP of WF in a surfactant-laden system is higher, whereas for M ≥ 1, the RP of WF in a clean system is higher.
Recently emerged hollow-core fiber provides an excellent platform for various studies due to its remarkable features, such as broadband transmissions, enhanced light-matter overlapping, ultra-low ...nonlinearity, low latency and dispersion. At the same time, it is generally known that nitrogen dioxide (NO2) is deemed a common air pollutant. Detecting its concentration is essential, covering environmental monitoring, industrial manufacturing, and human safety issues. Accurate detection of NO2 in gaseous state, however, has been a long-existing challenge due to the requirements for high sensitivity, compatible equipment, short sampling duration, etc. Here, a novel approach is reported for measuring NO2 gas by functionalizing a hollow-core anti-resonant fiber (HC-ARF) with CdTe-deposited quantum dots (QDs). The mechanism is based on fluorescence quenching of glutathione-capped CdTe QDs, triggered by NO2 gas. The hollow-core fiber works as a micro-reactor that enhances gas/light interactions. Consequently, the sensitivity can be effectively increased for detecting sub-ppm concentration (∼0.1 ppm) NO2 gas, with high efficiency, small sample volume, and short sampling durations of only a few minutes, much faster than that in many non-fiber-based systems. Such a rapid detection of low-concentration NO2 is applicable in most scenarios. These results provide a reliable, compatible, and promising solution for chemical and biological sensing of gas or liquid-phased substances in hollow-core fibers.
•A new gas sensor for nitrogen dioxide (NO2) detection by functionalizing a fiber is reported.•The hollow-core fiber works as a micro-reactor that enhances light-matter interactions.•Limit of detection (LoD) is improved to sub-ppm based on the efficient fluorescence quenching.•The gas detection can be completed with high efficiency, small sample volume, and short sampling durations of only a few minutes.
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