In this paper, we report the effect of different plasticizers, such as poly ethylene glycol, propylene carbonate, ethylene carbonate and dimethyl carbonate on the ionic conductivity and dielectric ...relaxation of PEO-LiClO4 solid polymer electrolytes. The highest ionic conductivity is obtained for polymer electrolyte plasticized with poly ethylene glycol. The temperature dependence of ionic conductivity follows the well known Vogel–Tamman–Fulcher relation which indicates a strong coupling of ionic and segmental motions for all compositions. The experimental data for the complex dielectric permittivity and electric modulus have been studied using Havriliak–Negami function for the understanding of ion dynamics. Maximum dielectric strength is obtained for polymer electrolyte plasticized with poly ethylene glycol. The modulus data have been analyzed using non-exponential Kohlrausch–Williams–Watts (KWW) function. It is observed that the non-exponential parameter β is quite lower than unity, suggesting highly a non-exponential relaxation exists in these materials. The temperature dependence of relaxation times obtained from dielectric and modulus formalisms also follow Vogel–Tamman–Fulcher relation for all plasticizers in the compositions.
Polymer dispersed liquid crystal (PDLC) glazing is a potential electrically actuated switchable adaptive glazing for low energy building application as it become transparent in the presence of ...alternating current (AC) power supply and become translucent/opaque without power supply. Optical properties and protection factor for a particular type of PDLC glazing was investigated in this work. Using UV–vis–NIR (1050) spectrophotometer spectral transmittance of this glazing was measured for its both states. PDLC on state needs 20V AC power supply to offer 41% transmission while without any supply this glazing becomes 23% transparent. In the switch off state LC particles offer forward scattering which makes this glazing translucent with high 82.6% haze. Solar factor for PDLC transparent and translucent state was found to be 0.53 and 0.39 respectively. Glazing protection factors were calculated using spectral transmittance data. Switchable transparency and switchable solar factor makes this glazing suitable to match adaptability of building occupants.
•Solar, luminous, UV transmittance of a PDLC glazing was measured.•Protection factors of PDLC glazing was calculated from spectral transmittance.•PDLC transparent and translucent state offered two different solar factors.
The plasticized PMMA-LiClO4 based solid polymer nano-composite electrolytes were prepared for different concentrations of TiO2 nano-particles using standard solution cast technique. The structure, ...glass transition temperature, thermal stability and particle size of these nano-composites have been studied by X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis and transmission electron microscopic analysis respectively. The complex conductivity spectra have been measured in the frequency range of 0.01 Hz–2 MHz and analyzed using random barrier model. The contribution of the electrode polarization in low frequency region and at high temperatures has been taken into account during analysis. The temperature dependence of ionic conductivity and relaxation time has been found to obey the Vogel-Tammann-Fulcher relation. A maximum ionic conductivity of ∼3.0 × 10−4 Scm−1 has been observed for the electrolyte with 1 wt% TiO2 nano-particles. The dielectric spectra have been analyzed using Havriliak-Negami function to understand the relaxation of charge carriers. The ion-ion and ion-polymer interactions have been studied using Fourier transform infrared (FTIR) spectra. Finally, the cycling performance of a coin cell of configuration graphite/PMMA-LiClO4-30 wt% PC-1wt% TiO2/LiCoO2 evaluated at 25 °C indicates suitability of the nano-composites as solid electrolytes for Li ion polymer cell.
Low-carbon micro-alloyed steel containing coarse MnS inclusions was subjected to different thermo-mechanical processing routes to evaluate the effect of microstructure on its Charpy impact properties ...over a range of temperatures. MnS inclusions were found to deteriorate the upper shelf energy (USE) of the steel but its effect on the impact transition temperature was not as detrimental as that due to the presence of TiN particles. MnS inclusions were responsible for the initiation of micro-voids; however, the propagation of the cracks from these depends on the effective grain size and the strength of the matrix. An increase in the density of dislocations and low-angle boundaries enhances the strength and the strain-hardening ability of the ferrite matrix. This helps in retarding the growth of micro-voids, thereby reducing USE and promoting cleavage crack propagation resulting in an increase in its impact transition temperature. Refinement of effective grain size, on the other hand, increases the crack propagation resistance and therefore, improves the low-temperature toughness of the steel. Finish rolling of the steel just above the Ar3 temperature (austenite to ferrite transformation start temperature) or a simple normalizing treatment of the as-rolled plates at a low austenitization temperature is recommended from the point of view of higher impact toughness and lower impact transition temperature.
In this article, we report first the effect of concentration of ethylene carbonate plasticizer on conduction and relaxation of charge carriers in PEO/PVDF-HFP–LiClO4 blend electrolytes. Second, the ...results for different plasticizers, such as ethylene carbonate, propylene carbonate, and dimethyle carbonate, on the conductivity and relaxation in these blend electrolytes are compared. We have followed a new approach for the analysis of the conductivity data. The frequency dependent conductivity is analyzed using random free-energy barrier model, taking into consideration the low frequency polarization effect. The temperature dependences of the ionic conductivity and the relaxation time obtained from the model exhibit Vogel–Tammann–Fulcher behavior. Using the scaling of the ac conductivity spectra it is observed that the relaxation dynamics of charge carriers in blend electrolytes are independent of temperature but depend on the nature of plasticizers. The electric modulus is studied using Havriliak–Negami function for the understanding of ionic relaxation. The modulus data are also analyzed using nonexponential Kohlrausch–Williams–Watts function. The temperature dependence of the relaxation time obtained from modulus analysis follows Vogel–Tammann–Fulcher relation for all plasticized electrolytes. It is observed that the stretched exponent is much lower than unity, which suggests that charge carrier relaxation is highly nonexponential in these plasticized electrolytes.
In this study, we report physicochemical properties of poly(vinylidene fluoride-hexafluoropropylene) based gel polymer electrolytes embedded with different ionic liquids such as ...1-butyl-2,3-dimethylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium tetrafluoroborate with a view to using them as electrochemical devices such as electrochemical capacitors. We also study the influence of cationic size and viscosity, dielectric constant of the ionic liquids on the physicochemical properties and electrochemical stability of the gels and also on electrochemical performance of the electrochemical capacitors fabricated with these gel electrolytes. The electrochemical performance of the electrochemical capacitors is studied by cyclic voltammerty, galvanostatic charge-discharge and electrochemical impedance spectroscopy. It is observed that the polymer electrolyte embedded with 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid having smallest size of cations and highest ionic conductivity displays a promising set of physicochemical properties and performs well as an electrolyte/separator in device in terms of specific capacitance, energy density, and cycle life comparatively. The values of specific capacitance obtained from galvanostatic charge-discharge, equivalent series resistance, energy density, response time, and pulse power for the electrochemical capacitor assembled with 1-ethyl-3-methylimidazolium tetrafluoroborate doped gel electrolytes are 113.6 F g−1, 20 Ω-cm2, 17.48 Wh kg−1, 5.46 s and 7.19 kW kg−1 at 1.0 mA cm−2 current respectively.
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•Effect of BDMIMBF4, BMIMBF4, and EMIMBF4 ILs based GPEs in EDLC are reported.•ILs with big cation and high viscosity exhibit less plasticization effect for GPEs.•Ionic conductivity of GPEs increases with decrease of cation size and viscosity.•Capacitance of EDLC increases with decrease of cation size and viscosity of ILs.•EMIMBF4 based GPE shows significantly good performance as electrolyte in devices.
We have studied ion conduction and relaxation in plasticized PMMA-LiClO4 solid polymer electrolyte for different salt concentrations over a wide range of temperature. We have measured the complex ...conductivity spectra in a wide frequency range of 0.01 Hz–3 GHz and analyzed the experimental results using the random barrier model coupled with the contribution of electrode polarization in low frequency region. The temperature dependence of ionic conductivity and charge carrier relaxation time obtained from the analysis follows Vogel-Tammann-Fulcher behavior. The nearly constant loss response has been observed at low temperatures and/or at high frequency region. The temperature and frequency range of nearly constant loss response depends on the salt concentration in polymer matrix. The electric modulus spectra have been used to study charge carrier relaxation further. The stretched exponent, obtained from Kohlrausch-Williams-Watts (KWW) function, indicates highly non-exponential relaxation in the polymer electrolytes.
•Ion transport in PMMA-LiClO4 electrolyte is analyzed using random-barrier model.•Electrode polarization is taken into account in the analysis.•Charge carrier relaxation is highly non-exponential.•Existence of nearly constant loss response is observed at high frequency.
Slow earthquakes in the form of tremors and low frequency earthquakes (low‐frequency earthquakes) occur along the south‐central range of Taiwan (Aguiar et al., 2017, ...https://doi.org/10.1002/2016gl072148; Chao et al., 2012, https://doi.org/10.1111/j.1365-246x.2011.05261.x; Tang et al., 2010, https://doi.org/10.1029/2010gl043918). This study detects discrete very low frequency earthquakes (VLFEs) using a grid‐search moment tensor inversion algorithm (Ghosh et al., 2015, https://doi.org/10.1002/2015gl063286; Hutchison & Ghosh, 2019, https://doi.org/10.1029/2018jb016138). By applying a matched filtered technique, we have created a robust VLFE catalog for 3 years. The two VLFEs closer to the tremor‐producing region show a temporal relationship, but the western VLFE is the most active among the three. Our VLFE catalog of high temporal resolution allows us to identify a significant increase in VLFE activities preceding earthquake swarms. An empirical comparison of the VLFE catalog with regional and local cataloged fast earthquakes reveals two such instances. We show that fluid migration from deeper to shallower crust explains this modulation of regular fast earthquakes by VLFEs.
Plain Language Summary
Slow earthquakes are an important part of a broad spectrum of the earthquake behavior. Yet, their underlying physics and connection to rest of the earthquake spectrum remain enigmatic. Taiwan is an area with complex geology hosting slow earthquakes. Still, their characteristics and relationship to other regular earthquakes are poorly understood. Using three years of high‐quality seismic data, we have identified and located three discrete events known as very low‐frequency earthquakes occurring deeper than the typical seismogenic zone in the earth crust. Our analyses show that these events modulate regular earthquakes in its vicinity. This relationship between the slow and fast earthquakes may be a result of fluid transfer from the deep to the shallow crust.
Key Points
Discovery of Discrete very low frequency earthquakes (VLFEs) in the Central range of Taiwan
VLFEs modulate Fast earthquakes in the area
Fluid flow in the fault system can explain this observation
Gel polymer electrolytes are prepared using poly(vinylidene fluoride-co-hexafluoropropylene) polymer matrix and 1- propyl-3-methyleimidazolium bis(trifluromethylesulfonyl)-imide ionic liquid and also ...by adding lithium bis(trifluoromethanesulfonyl)imide salt and plasticizer mixture (ethylene carbonate: propylene carbonate in the ratio 1:1). Thermal and electrical properties of these electrolytes are first investigated. The electrical conductivity of these electrolytes is analyzed over a wide frequency range using a universal power law coupled with modified Poisson-Nernst-Planck model for electrode polarization. All electrolytes show excellent thermal stability up to 340 °C, high ionic conductivity (∼1 × 10−3 S cm−1) and wide potential window (∼4.0 V). Supercapacitors are fabricated with these electrolytes using activated carbon as electrodes and their electrochemical properties are studied. The cyclic voltammetry curves show almost box-like shape corresponding to an ideal and reversible capacitive characteristic. The specific capacitance of supercapacitors increases with the addition of lithium salt and plasticizer mixture. The cycle stability of these supercapacitors up to 4000 cycles confirms their electrochemical stability. A lithium ion coin cell is also fabricated using electrolytes containing plasticizer mixture. At ambient temperature, the fabricated cell delivers high specific discharge capacity (∼165.8 mAh g−1) for the first discharge cycle at a constant current rate C/12.
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