Conductivity and dielectric properties of proton conducting poly (Vinyl)chloride (PVC) based gel polymer electrolytes

Poly (vinyl) chloride (PVC)-NH4I-EC films have been prepared by the solution cast technique. The sample containing 30 wt.% NH4I exhibited the highest room temperature conductivity of 4.60 × 10-7 S cm-1. The conductivity increased to 1.08 × 10-6 Scm-1 when 15 wt.% of ethylene carbonate (EC) was added to 70 wt.% PVC - 30 wt.% NH4I. The effects of ethylene carbonate (EC) addition on the frequency dependent dielectric properties of PVC based electrolytes were investigated by electrochemical impedance spectroscopy (EIS), in the temperature range of 300 K to 373 K. The dielectric properties and ac conductivity of the samples prepared have been analyzed. The values of dielectric constant were found to increase with increasing conductivity of the samples. Analysis of the ac conductivity data revealed the electrolytes to be of the non-Debye type with conduction mechanism of the overlapping-large-polaron-tunneling (OLPT) model

Fitting statistical distribution of extreme rainfall data for the purpose of simulation

In this study, several types of probability distributions were used to fit the daily torrential rainfall data from 15 monitoring stations of Peninsular Malaysia from the period of 1975 to 2007. The study of fitting statistical distribution is important to find the most suitable model that could anticipate extreme events of certain natural phenomena such as flood and tsunamis. The aim of the study is to determine which distribution fits well with the daily torrential Malaysian rainfall data. Generalized Pareto, Lognormal and Gamma distributions were the distributions that had been tested to fit the daily torrential rainfall amount in Peninsular Malaysia. First, the appropriate distribution of the daily torrential rainfall was identified within the selected distributions for rainfall stations. Then, data sets were generated based on probability distributions that mimic a daily torrential rainfall data. Graphical representation and goodness of fit tests were used in finding the best fit model. The Generalized Pareto was found to be the most appropriate distribution in describing the daily torrential rainfall amounts of Peninsular Malaysia. The outputs can be beneficial for the purpose of generating several sets of simulated data matrices that mimic the same characteristics of rainfall data in order to assess the performance of the modification method compared to classical method

The Use of Gum Arabic Liquid and Modified Liquid in Concrete Mixes

In this paper, the purest kind of  Gum Arabic, extracted from (Hashab) trees (in western Sudan ), is used in concrete mixes after crushing to be in a form of powder which was dissolved in water to get the liquid of this additive. In this study, Gum Arabic liquid was added to concrete mixes at ratios of 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0 % and 1.2 % of cement content. Eleven concrete mixes were prepared: One as a control mix, seven with Gum Arabic liquid, and three with Gum Arabic liquid with modified water cement ratios added. This modification was done by reducing water cement ratios in concrete mixes to be 0.4 %, 0.6% and 0.8% of cement content. The study showed that the addition of Gum Arabic to the concrete mixes has a clear effect when equal to 0.4% of cement content. The compressive strength was measured at ages of 7, 21, and 28 days and it was found that it decreases slightly with increase in the proportion of Gum Arabic in concrete mixes. The concrete mixes prepared using modified gum Arabic in its liquid state by reducing (w/c) and adding gum Arabic as a percentage of cement content showed a clear and significant change in the properties of concrete. These ratios resulted in high compressive strength concrete with good workability. Keywords: Gum Arabic, Hashab, Sudan, compressive strength, workabilit

Structural and electrical properties of Li4.08+xZn0.04AlxSi0.96-xO4 ceramic electrolyte

In this paper, we report the effect of Al3+ substitutions to the structural and electrical properties of Li4.08Zn0.4Si0.96O4 ceramic electrolyte. X-ray diffraction was applied to study the structural properties such as crystalline phase, lattice parameter and unit cell volume of the solid electrolytes. The electrical properties of the compounds measured by Ac impedance as a function of frequency in the range between 0.1 Hz to 10 MHz and in temperature range between 473 K to 773 K. The optimal value of the total conductivity were reached at x = 0.03 measured at 773 K. This result indicates that the substitutions of Al3+ in the Li4.08Zn0.4SiO4 structure improved the conductivity due to the enhancement of Li+ ion concentration and mobility

Corrosion inhibition of copper in chloride media by 2-mercapto-4-(p-methoxyphenyl)-6-oxo-1,6-dihydropyrimidine-5-carbonitrile: Electrochemical and theoretical study

AbstractElectrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization have been used to investigate the inhibition effect of a new pyrimidine heterocyclic derivative, namely 2-mercapto-4-(p-methoxyphenyl)-6-oxo-1,6-dihydropyrimidine-5-carbonitrile (MPD) on copper corrosion in 3.5% NaCl solutions at 25±1°C. The electrochemical investigations showed that MPD gives sufficient inhibition against copper corrosion in 3.5% NaCl solutions. Potentiodynamic polarization measurements have shown that the MPD inhibit both the cathodic and anodic processes and thus it classified as mixed-type inhibitor. EIS measurements indicate that the values of constant phase elements (CPEs) tend to decrease and both charge-transfer resistance and inhibition efficiency tend to increase by increasing the inhibitor concentration. Electrochemical kinetic parameters obtained using EFM methods were comparable with that calculated from traditional measurements (EIS and potentiodynamic polarization). Molecular simulation technique was used to investigate the adsorption configuration of MPD on copper surface. Number of electrons transferred from MPD to the copper surface was calculated by semi-empirical quantum chemical calculations

Characterization of PVDF-HFP-LiCF3S03-Zr02 nanocomposite polymer electrolyte systems

Nanocomposite polymer electrolytes were prepared by incorporating different amounts of zirconium oxide (Zr02) nanofiller to poly(vinylidene fluoride-co exafluoropropylene)-lithium trifluoromethane sulfonate (PVDF-HFP-LiCF3S03). X-ray diffraction (XRD) study has been carried out to investigate the structural features of the electrolyte films while a.c. impedance spectroscopy has been performed to investigate their electrical properties. The conductivity of nanocomposite polymer electrolyte systems is influenced by nanofiller concentration. The increase in conductivity is attributable to the increase in the fraction of amorphous region and the number of charge carriers and vice versa. The highest conductivity obtained is in the order of 10-3 S cm-1 for the system dispersed with 5 wt% of Zr02 nanofiller

The investigation on ionic conduction of PEMA based solid polymer electrolytes

Solid polymer electrolytes comprising of various weight ratios of poly(ethyl methacrylate) (PEMA) and lithium perchlorate (LiCl04) salt were prepared via solution casting technique using N,N-Dimethylformamide (DMF) as the solvent. The conductivity values of the electrolytes were determined utilizing Solatron 1260. The highest conductivity obtained is in the order of 10-6 S ern -I. Structural properties of the electrolytes were investigated by X-ray diffraction and the results show that the highest conducting film is the most amorphous

Axial load-axial deformation behaviour of circular concrete columns reinforced with GFRP bars and helices

Fibre Reinforced Polymer (FRP) bars has attracted a significant amount of research attention in the last three decades to overcome the problems associated with the corrosion of steel reinforcing bars in reinforced concrete members. A limited number of studies, however, have investigated the behaviour of concrete columns reinforced with FRP bars. Also, available design standards either ignore the contribution of or do not recommend the use of GFRP bars in compression members. This study reports the results of experimental investigations of concrete specimens reinforced with GFRP bars and GFRP helices as longitudinal and transverse reinforcement, respectively. A total of five circular concrete columns of 205 mm in diameter and 800 mm in height were cast and tested under axial compression. The experimental results showed that reducing the spacing of the GFRP helices or confining the specimens with CFRP sheet led to improvements in the strength and ductility of the specimens. Also, an analytical model has been developed for the axial load-axial deformation behaviour of the circular concrete columns reinforced with GFRP bars and helices. The model has been validated with the experimental results

Geographical and temporal distribution of SARS-CoV-2 clades in the WHO European Region, January to June 2020

We show the distribution of SARS-CoV-2 genetic clades over time and between countries and outline potential genomic surveillance objectives. We applied three available genomic nomenclature systems for SARS-CoV-2 to all sequence data from the WHO European Region available during the COVID-19 pandemic until 10 July 2020. We highlight the importance of real-time sequencing and data dissemination in a pandemic situation. We provide a comparison of the nomenclatures and lay a foundation for future European genomic surveillance of SARS-CoV-2.Peer reviewe