Decomposition pathway and stabilization of ether-based electrolytes in the discharge process of Li-O_(2) battery

Ether-based electrolytes with relatively high stability are widely used in Li-O_(2) batteries (LOBs) with high energy density.However,they are still prone to be attacked by reactive oxygen species.Understanding the degradation chemistry of ether-based solvent induced by reactive oxygen species is significant importance toward selection of stable electrolytes for LOBs.Herein,we demonstrate that a great amount of H_(2) gas evolves on the Li anode during the long-term discharge process of LOBs,which is due to the electrolyte decomposition at the oxygen cathode.By coupling with in-situ and ex-situ characterization techniques,it is demonstrated that O_(2)^(-) induces the H-abstraction of tetraethylene glycol dimethyl ether(TEGDME) to produce a large amount of H_(2)O at cathode,and this H_(2)O migrates to Li anode and produce H_(2) gas.Based on the established experiments and spectra,a possible decomposition pathway of TEGDME caused by O_(2)^(-)at the discharge process is proposed.And moreover,three types of strategies are discussed to inhibit the decomposition of ether-based electrolytes,which should be highly important for the fundamental and technical advancement for LOBs.

Plasma Discharge Process in a Pulsed Diaphragm Discharge System

As one of the most important steps in wastewater treatment, limited study on plasma discharge process is a key challenge in the development of plasma applications. In this study, we focus on the plasma discharge process of a pulsed diaphragm discharge system. According to the analysis, the pulsed diaphragm discharge proceeds in seven stages： （1） Joule heating and heat exchange stage; （2） nucleated site formation; （3） plasma generation （initiation of the breakdown stage）; （4） avalanche growth and plasma expansion; （5） plasma contraction; （6） termination of the plasma discharge; and （7） heat exchange stage. From this analysis, a critical voltage criterion for breakdown is obtained. We anticipate this finding will provide guidance for a better application of plasma discharges, especially diaphragm plasma discharges.

Experiments on Development of Channel Pattern in the Process of River Reformation

The changing of flow conditions caused by construction of hydro-projects will result in river's refor- mation and development of channel pattern.In this paper,the development of channel pattern in the process of reformation is studied by means of flume experiments.Influence of slope,grain size,angle-of-inflow,dis- charge and discharge process are comprehensively analyzed according to the experimental data.It was found that the channel would be widened as the river slope or discharge increased and grain s...

Performance in the Discharge Process of a Novel Zeolite-Water Adsorption Thermal Energy Storage System

In order to effectively recover low and medium grade heat energy,a novel combined cooling and heating storage system based on zeolite-water is proposed in this paper.The system coupled the zeolite-water adsorption process with the water evaporation refrigeration process during discharging process to realize generating cold energy and heat energy simultaneously.A more accurate kinetic model of zeolite and water adsorption is developed,and the thermodynamic performance of discharging process of the system is numerically analyzed.The results show the system has the higher energy conversion coefficient of 1.49 and the higher energy density of 1216.6 kJ/kg-zeolite.The change laws of system performances,such as energy generated,energy conversion coefficient and energy density,with key parameters during discharging process are revealed.The study provides a way for efficient utilization of low and medium grade heat energy.

MICRO ELECTRICAL DISCHARGE MACHINING DEPOSITION IN AIR

A new deposition method is described using micro electrical discharge machining （EDM） to deposit tool electrode material on workpiece in air. The basic principles of micro electrical discharge deposition （EDD） are analyzed and the realized conditions are predicted. With an ordinary EDM shaping machine, brass as the electrode, high-speed steel as the workpiece, a lot of experiments are carried out on micro EDD systematically and thoroughly. The effects of major processing parameters, such as the discharge current, discharge duration, pulse interval and working medium, are obtained, As a result, a micro cylinder with 0.19 mm in diameter and 7.35 mm in height is deposited. By exchanging the polarities of the electrode and workpiece the micro cylinder can be removed selectively. So the reversible machining of deposition and removal is achieved, which breaks through the constraint of traditional EDM. Measurements show that the deposited material is compact and close to workpiece base, whose components depend on the tool electrode, material.

A Study of Multi-Permeating TiN/Ti Alloying Layer Using Plasma Surface Alloying Technology

TiN/Ti multi-permeating alloying layer has been formed on the low carbon steel by means of the double glow-discharge plasma surface alloying technique and hollow-cathode effect. The alloying layer was detected by axiovert 25 CA optical microscope with computer analyzing software （LEC）, GDA-2 glow discharge spectroscopy （GDS）, X-ray diffraction （XRD） and galvanochemical method. The results showed that the thickness of TiN/Ti multi-permeating alloying layer was about 10μm, the content of Ti on the surface was up to 63.48 wt% and the content of N was up to 12.46 wt%. The atom Ti and N concentrations changed gradually across the depth of the alloying layer and the preferred orientation of TiN/Ti alloying layer was crystal surface （200）. The multi-permeating alloying layer and substrate were combined through metallurgy. The surface appearances of the multi-permeating alloying layer were uniform and of a compact cellular structure. The hardness of the surface was about 1600-3000 HV0.1. The corrosion resistance of the permeating TiN/Ti alloying layer in 0.5 mol/L H2SO4 solution was greatly increased and the corrosion rate was only 0.3082 g/m^2. h.

Effects of magnetic field on electron power absorption in helicon fluid simulation

In this study,a code,named Peking University Helicon Discharge(PHD),which can simulate helicon discharge processes under both a background magnetic field greater than 500 G and a pressure less than 1 Pa,is developed.In the code,two fluid equations are used.The PHD simulations led to two important findings:(1)the temporal evolution of plasma density with the background magnetic field exhibits a second rapid increase(termed as the second density jump),similar to the transition of modes in helicon plasmas;(2)in the presence of a magnetic field,the peak positions of electron power absorption appeared near the central axis,unlike in the case of no magnetic field.These results may lead to an enhanced understanding of the discharge mechanism.

Boosting the adsorption and removal of dye from water by COOH-functionalized carbon nanotubes

Water pollution caused by dye is a serious challenge.Herein,we use a novel discharge process to functionalize carbon nanotube(CNT)by COOH groups to form CNT30 for removing methyl red(MR)from water.By pristine CNT,75%MR is removed in 60 min,with an adsorption capacity of 68.44 mg g-1.By CNT30,85%MR is fast removed in only 5 min,and the removal efficiency reaches to 95%after 30 min,with an adsorption capacity of80.33 mg g-1.Thus,a higher MR removal efficiency is achieved in a much shorter time on CNT30.Moreover,CNT30 has an outstanding reusability,with the MR removal efficiency decreasing by only 7%after ten cycles.The COOH groups on CNT30 improve the hydrophilicity of CNT30,thus promoting the interaction of MR in water with CNT30.The hydrogen bonding and electrostatic interaction of MR with the COOH groups on CNT30 could be the force to drive MR adsorption on CNT30.The higher COOH content could be the origin for the better performance of CNT30 in removing dye from water.The discharge process developed herein is operated in O2,without using harmful substances,and the COOH content on CNT can be efficiently tuned by simply changing discharge time.This is different from the chemical modification widely used to functionalize CNT by strong oxidants,e.g.,HNO_(3).The present work is of great significance to realize green construction of materials for more efficiently removing dye from water.