Understanding Lithium-ion Transport in Sulfolane- and Tetraglyme-Based Electrolytes Using Very Low-Frequency Impedance Spectroscopy

With the increasing interest in highly concentrated electrolyte systems,correct determination of the cation transference number is important.Pulsed-field gradient NMR technique,which measures self-diffusion coefficients,is often applied on liquid electrolytes because of the wide accessibility and simple sample preparation.However,since the assumptions of this technique,that is,complete salt dissociation,all ions participating in motion,and all of them moving independently,no longer hold true in concentrated solutions,the transference numbers,thus obtained are often over-estimated.In the present work,impedance spectroscopy at a frequency range of 1 MHz to 0.1 mHz was used to examine the concentration effect on lithium-ion transference number under anion-blocking conditions T abc Liþfor two electrolytes:lithium bis(fluorosulfonyl)imide(LiFSI)in sulfolane(SL)and lithium bis(trifluorosulfonyl)imide(LiTFSI)in tetraglyme(G4).The T abc Liþof the former was almost an order of magnitude higher than that of the latter.It also appeared to increase with increasing concentration while the latter followed an opposite trend.The faster Li^(+)transport in the SL system is attributed to the formation of a liquid structure consisting of extended chains/bridges of SL molecules and the anions,which facilitate a cation-hopping/ligand-exchanged-typed diffusion mechanism by partially decoupling the cations from the anions and solvent molecules.The G4 system,in contrast,is dominated by the formation of long-lived,stable[Li(G4)]+solvation cages that results in a sluggish Li+transport.The difference between the two transport mechanisms is discussed via comparison of the bulk ionic conductivity,viscosity,ion self-diffusion coefficients,and the Onsager transport coefficients.

XRD Characterization of AlN Thin Films Prepared by Reactive RF-Sputter Deposition

AlN thin films have been grown on R((1-12) surface-cut)-Al2O3, SiO2-glass and C((001) surface-cut)-Al2O3 substrates, by using a reactive-RF-sputter-deposition method. X-ray diffraction (XRD) shows that AlN film has (110) orientation of wurtzite crystal structure for R-Al2O3 and (001) orientation for SiO2-glass and C-Al2O3 substrates. The film thickness was analyzed by Rutherford backscattering spectroscopy (RBS) and it appears that XRD intensity does not show a linear increase with the film thickness but a correlation with the stress, i.e., deviation of the lattice parameter of the film from that of bulk. The film composition and impurities have been analyzed by ion beam techniques. Effects of high-energy ion beams are briefly presented on atomic structure (whether stress relaxation occurs or not), surface morphology and optical properties.

Effects of plasma actuation and hole configuration on film cooling performance

In this paper,plasma actuators are arranged asymmetrically downstream the wall to improve film cooling performance.Effects of blowing ratio,hole configuration and applied voltage on flow characteristics and film cooling effectiveness were investigated numerically on a flat plate.Results show that highest film cooling effectiveness distribution is obtained both in the spanwise and streamwise directions under blowing ratio of 0.5.Average wall film cooling effectiveness of cylindrical hole increases by 251.9%under blowing ratio of 0.5 compared to that under blowing ratio of 1.5.The scale of the counter rotating vortex pairs(CRVP)from fan shaped hole and sister hole are significantly reduced compared to that from cylindrical hole.The console hole has an anti-counter rotating vortex pair(Anti-CRVP),which weakens the entrainment of the CRVP to the coolant air near the wall.Compared with the cylindrical hole,average wall film cooling effectivenesses for fan shaped hole,sister hole and console hole increase by 73.1%,97.5%and 119.9%.The adherent performance of the coolant air is enhanced after applying plasma actuator.The aerodynamic actuation of the plasma results in the rebound of the fluid close to the wall at 24 kV applied voltage.Average wall film cooling effectiveness of the console hole at 12 kV applied voltage is 10.6%higher than that without plasma.

Film cooling effects on the tip flow characteristics of a gas turbine blade

An experimental investigation of the tip flow characteristics between a gas turbine blade tip and the shroud was conducted by a pressure-test system and a particle image velocimetry(PIV)system.A three-times scaled profile of the GE-E3 blade with five film cooling holes was used as specimen.The effects on flow characteristics by the rim width and the groove depth of the squealer tip were revealed.The rim widths were(a)0.9%,(b)2.1%,and(c)3.0%of the axial chord,and the groove depths were(a)2.8%,(b)4.8%,and(c)10%of the blade span.Several pressure taps on the top plate above the blades were connected to pressure gauges.By a CCD camera the PIV system recorded the velocity field around the leading edge zone including the five cooling holes.The flow distributions both in the tip clearance and in the passage were revealed,and the influence of the inlet velocity was determined.In this work,the tip flow characteristics with and without film cooling were investigated.The effects of different global blowing ratios of M=0.5,1.0,1.3 and 2.5 were established.It was found that decreasing the rim width resulted in a lower mass flow rate of the leakage flow,and the pressure distributions from the leading edge to the trailing edge showed a linearly increasing trend.It was also found that if the inlet velocity was less than 1.5 m/s,the flow field in the passage far away from the suction side appeared as a stagnation zone.