scholarly journals The Polarisation Behaviour of Silver in Potassium Hydroxide Solution at Elevated Temperatures

2021 ◽  
Author(s):  
◽  
Bruce George Pound
Keyword(s):  
Surface Roughness ◽  
Cyclic Voltammetry ◽  
Elevated Temperatures ◽  
Potassium Hydroxide Solution ◽  
Water System ◽  
Cyclic Voltammograms ◽  
Derived Relations ◽  
Temperature Range ◽  
State Diffusion ◽  
Extensive Surface

<p>The Polarisation behaviour of silver in 1 mol kg-1 KOH solution over the temperature range 295-478 K was studied using cyclic voltammetry, potentiostatic, galvanostatic and a.c. impedance techniques. Thermodynamic data for the silver/water system at temperatures up to 573 K is presented in the form of potential-pH diagrams which assist in the interpretation of results at elevated temperatures. The cyclic voltammograms and galvanostatic charging curves indicate the principal changes to be the appearance of additional peaks and arrests, respectively, as the temperature is increased, followed by their disappearance at higher temperatures. The data obtained from cyclic voltammetry and also potentiostatic polarisation are analysed in terms of previously-derived relations for limiting rate control, in particular that due to diffusion. The impedance data are examined using equivalent circuit models from which it is shown that surface roughness of the electrodes has a significant effect on the reaction kinetics over the temperature range studied. It is proposed that substantial changes in the electrochemistry of silver at 478 K are associated with extensive surface roughness that a change in the kinetics of growth of the Ag2O multilayer takes place at elevated temperatures with the rate of nucleation of Ag2O growth centres becoming more important in relation to the rate of solid-state diffusion.</p>

scholarly journals The Polarisation Behaviour of Silver in Potassium Hydroxide Solution at Elevated Temperatures

2021 ◽  
Author(s):  
◽  
Bruce George Pound
Keyword(s):  
Surface Roughness ◽  
Cyclic Voltammetry ◽  
Elevated Temperatures ◽  
Potassium Hydroxide Solution ◽  
Water System ◽  
Cyclic Voltammograms ◽  
Derived Relations ◽  
Temperature Range ◽  
State Diffusion ◽  
Extensive Surface

<p>The Polarisation behaviour of silver in 1 mol kg-1 KOH solution over the temperature range 295-478 K was studied using cyclic voltammetry, potentiostatic, galvanostatic and a.c. impedance techniques. Thermodynamic data for the silver/water system at temperatures up to 573 K is presented in the form of potential-pH diagrams which assist in the interpretation of results at elevated temperatures. The cyclic voltammograms and galvanostatic charging curves indicate the principal changes to be the appearance of additional peaks and arrests, respectively, as the temperature is increased, followed by their disappearance at higher temperatures. The data obtained from cyclic voltammetry and also potentiostatic polarisation are analysed in terms of previously-derived relations for limiting rate control, in particular that due to diffusion. The impedance data are examined using equivalent circuit models from which it is shown that surface roughness of the electrodes has a significant effect on the reaction kinetics over the temperature range studied. It is proposed that substantial changes in the electrochemistry of silver at 478 K are associated with extensive surface roughness that a change in the kinetics of growth of the Ag2O multilayer takes place at elevated temperatures with the rate of nucleation of Ag2O growth centres becoming more important in relation to the rate of solid-state diffusion.</p>

scholarly journals Cyclic and square-wave voltammetry for selective simultaneous NO and O<sub>2</sub> gas detection by means of solid electrolyte sensors

2020 ◽  
Vol 9 (2) ◽  
pp. 355-362
Author(s):  
Anastasiya Ruchets ◽  
Nils Donker ◽  
Jens Zosel ◽  
Daniela Schönauer-Kamin ◽  
Ralf Moos ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Solid Electrolyte ◽  
Square Wave Voltammetry ◽  
Limit Of Detection ◽  
Inert Gases ◽  
Cyclic Voltammograms ◽  
Square Wave ◽  
Temperature Range ◽  
Wave Voltammetry ◽  
Scan Rate

Abstract. Solid electrolyte gas sensors (SESs) based on yttria-stabilized zirconia (YSZ) are suitable to detect traces of redox components in inert gases. Usually, their signals are generated as a voltage between two electrodes at open circuit potential or as a current flowing between constantly polarized electrodes. In these rather stationary modes of operation, SESs often lack the desired selectivity. This drawback can be circumvented if SESs are operated in dynamic electrochemical modes that utilize the differences of electrode kinetics for single components to distinguish between them. Accordingly, this contribution is directed to the investigation of cyclic voltammetry and square-wave voltammetry as methods to improve the selectivity of SESs. For this, a commercial SES of the type “sample gas, Pt|YSZ|Pt, air” was exposed to mixtures containing NO and O2 in N2 in the temperature range between 550 and 750 ∘C. On cyclic voltammograms (CVs), NO-related peaks occur in the cathodic direction at polarization voltages between −0.3 and −0.6 V at scan rates between 100 and 2000 mV s−1 and temperatures between 550 and 750 ∘C. Their heights depend on the NO concentration, on the temperature and on the scan rate, providing a lower limit of detection below 10 ppmv, with the highest sensitivity at 700 ∘C. The O2-related peaks, appearing also in the cathodic direction between −0.1 and −0.3 V at scan rates between 100 and 5000 mV s−1, are well separated from the NO-related peaks if the scan rate does not exceed 2000 mV s−1. Square-wave voltammograms (SWVs) obtained at a pulse frequency of 5 Hz, pulses of 0.1 mV and steps of 5 mV in the polarization range from 0 to −0.6 V also exhibit NO-related peaks at polarization voltages between −0.3 and −0.45 V compared to the Pt–air (platinum–air) electrode. In the temperature range between 650 and 750 ∘C the highest NO sensitivity was found at 700 ∘C. O2-related peaks arise in the cathodic direction between −0.12 and −0.16 V, increase with temperature and do not depend on the concentration of NO. Since capacitive currents are suppressed with square-wave voltammetry, this method provides improved selectivity. In contrast to cyclic voltammetry, a third peak was found with square-wave voltammetry at −0.48 V and a temperature of 750 ∘C. This peak does not depend on the NO concentration. It is assumed that this peak is due to the depletion of an oxide layer on the electrode surface. The results prove the selective detection of NO and O2 with SESs operated with both cyclic voltammetry and square-wave voltammetry.

Dynamic Indentation of Copper and an Aluminium Alloy with a Conical Projectile at Elevated Temperatures

1965 ◽  
Vol 180 (1) ◽  
pp. 285-294 ◽  
Author(s):  
F. U. Mahtab ◽  
W. Johnson ◽  
R. A. C. Slater
Keyword(s):  
Strain Rate ◽  
Aluminium Alloy ◽  
Temperature Coefficient ◽  
Elevated Temperatures ◽  
Dynamic Pressure ◽  
Pure Metal ◽  
Dynamic Indentation ◽  
Strain Rate Effects ◽  
Dynamic Temperature ◽  
Temperature Range

The dynamic indentation of copper (B.S. 1433) and an aluminium alloy (B.S. 1476 HE 10) has been investigated, using cylindro-conical projectiles fired from an air-actuated gun. The experiments were performed with impact velocities varying between 1000 and 2500 in/s and at elevated temperatures up to 600°C for the copper and 550°C for the aluminium alloy. The magnitude of the corresponding range of mean strain rate was then 103-104/s, depending upon the material; impact velocity and temperature (see Appendix I). For the range of impact velocities investigated no consequential transition temperature † was encountered. The dynamic temperature coefficient† thus remained constant throughout the test temperature range for each material. This dynamic temperature coefficient was found to be equal to the static temperature coefficient corresponding to the sub-transitional temperature range for the respective materials. The mean effective dynamic indentation pressure is shown to decrease with temperature but the ratio of this dynamic pressure to the static indentation pressure increases with temperature. Strain rate effects for both materials were negligible for sub-transitional temperatures but become important at super-transitional temperatures. It was observed that the parameters on which the strain rate effect depends are in some way related to the absolute melting point of a pure metal.

Polyaniline: Influence of Polymerization Current Density

1994 ◽  
Vol 369 ◽  
Author(s):  
Steen Skaarup ◽  
L.M.W.K. Gunaratne ◽  
Keld West ◽  
Birgit Zachau-Christiansen
Keyword(s):  
Cyclic Voltammetry ◽  
Current Density ◽  
High Current Density ◽  
Electrochemical Polymerization ◽  
Regular Structure ◽  
Spectral Lines ◽  
Complex Nature ◽  
Cyclic Voltammograms ◽  
Layer By Layer ◽  
Current Densities

AbstractPolyaniline has been synthesized in propylene carbonate by galvanostatic electrochemical polymerization at current densities between 16 and 1000 μA/cm2. Earlier results for polypyrrole have shown that low and high current density films have different properties: The films synthesized at low current density have a higher conjugation length and a more regular structure. The corresponding effect in PANI has been investigated by cyclic voltammetry and UV/visible spectroscopy. Simultaneous measurement of cyclic voltammograms and the absorbtion of selected spectral lines is used because of the complex nature of the PANI system which involves several redox systems as well as forms differing in the degree of protonation and morphology.The main result is that the method of galvanostatic synthesis at low current densities (-16 μA/cm2) produces polyaniline polymers of different, more conjugated and more regular structure than those prepared at higher current densities. The standard method of in situ layer-by-layer polymerization of conducting polymers during cyclic voltammetry often results in uncontrolled and unmeasured current densities of 0.5-2 mA/cm2 which produces a film that probably has a less regular structure containing more deviations from ideality.

scholarly journals Characterizing a thermostable Cas9 for bacterial genome editing and silencing

2017 ◽  
Author(s):  
Ioannis Mougiakos ◽  
Prarthana Mohanraju ◽  
Elleke F. Bosma ◽  
Valentijn Vrouwe ◽  
Max Finger Bou ◽  
...  
Keyword(s):  
Genome Editing ◽  
Genome Engineering ◽  
Gene Deletion ◽  
Elevated Temperatures ◽  
Bacterial Genome ◽  
Thermophilic Bacterium ◽  
Geobacillus Thermodenitrificans ◽  
Temperature Range ◽  
Fundamental Research

AbstractCRISPR-Cas9 based genome engineering tools have revolutionized fundamental research and biotechnological exploitation of both eukaryotes and prokaryotes. However, the mesophilic nature of the established Cas9 systems does not allow for applications that require enhanced stability, including engineering at elevated temperatures. Here, we identify and characterize ThermoCas9: an RNA-guided DNA-endonuclease from the thermophilic bacterium Geobacillus thermodenitrificans T12. We show that ThermoCas9 is active in vitro between 20°C and 70°C, a temperature range much broader than that of the currently used Cas9 orthologues. Additionally, we demonstrate that ThermoCas9 activity at elevated temperatures is strongly associated with the structure of the employed sgRNA. Subsequently, we develop ThermoCas9-based engineering tools for gene deletion and transcriptional silencing at 55°C in Bacillus smithii and for gene deletion at 37°C in Pseudomonas putida. Altogether, our findings provide fundamental insights into a thermophilic CRISPR-Cas family member and establish the first Cas9-based bacterial genome editing and silencing tool with a broad temperature range.

scholarly journals Electrochemical synthesis of poly(2-methyl aniline): electrochemical and spectroscopic characterization

2001 ◽  
Vol 66 (1) ◽  
pp. 27-37 ◽  
Author(s):  
Aleksandra Buzarovska ◽  
Irena Arsova ◽  
Ljubomir Arsov
Keyword(s):  
Raman Spectroscopy ◽  
Cyclic Voltammetry ◽  
Redox Reactions ◽  
Electrochemical Polymerization ◽  
Spectroscopic Characterization ◽  
Potential Range ◽  
Cyclic Voltammograms ◽  
Impedance Measurements ◽  
Order Of Magnitude ◽  
Poly Aniline

Poly(2-methyl aniline) or poly(ortho-toluidine), as ring substituted derivative of aniline, has been synthesized electrochemically in various concentrations of H2SO4 and HCl, and then characterized by cyclic voltammetry, as well as by impedance and Raman spectroscopy. The cyclic voltammograms of poly(o-toluidine) and poly(aniline) show that the electrochemical polymerization of these two polymers proceeds by almost identical mechanisms. The Raman spectroscopical measurements suggest that the redox reactions of poly(aniline) and poly(o-toluidine) are similar in the potential range between -0.2 and 0.7V vs. SCE. The impedance measurements showed that the conductivity of poly(o-toluidine) is an order of magnitude lower than that of the corresponding poly(aniline) form.

CMOS Circuits on Silicon Carbide for High Temperature Operation

2014 ◽  
Vol 1693 ◽  
Author(s):  
David T. Clark ◽  
Robin F. Thompson ◽  
Aled E. Murphy ◽  
David A. Smith ◽  
Ewan P. Ramsay ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
High Temperature ◽  
Wide Temperature Range ◽  
Integrated Circuit ◽  
Elevated Temperatures ◽  
Logic Circuits ◽  
Digital Logic ◽  
Cmos Integrated Circuit ◽  
Temperature Range ◽  
Simple Logic

ABSTRACTWe present the characteristics of a high temperature CMOS integrated circuit process based on 4H silicon carbide designed to operate at temperatures beyond 300°C. N-channel and P-channel transistor characteristics at room and elevated temperatures are presented. Both channel types show the expected low values of field effect mobility well known in SiC MOSFETS. However the performance achieved is easily capable of exploitation in CMOS digital logic circuits and certain analogue circuits, over a wide temperature range.Data is also presented for the performance of digital logic demonstrator circuits, in particular a 4 to 1 analogue multiplexer and a configurable timer operating over a wide temperature range. Devices are packaged in high temperature ceramic dual in line (DIL) packages, which are capable of greater than 300°C operation. A high temperature “micro-oven” system has been designed and built to enable testing and stressing of units assembled in these package types. This system heats a group of devices together to temperatures of up to 300°C while keeping the electrical connections at much lower temperatures. In addition, long term reliability data for some structures such as contact chains to n-type and p-type SiC and simple logic circuits is summarized.

Interaction between Binuclear Copper(I) Complexes and the Dioxygen Molecule Investigated by Electrochemical Methods

1992 ◽  
Vol 47 (1) ◽  
pp. 109-114 ◽  
Author(s):  
Yuzo Nishida ◽  
Izumi Watanabe ◽  
Kei Unoura
Keyword(s):  
Cyclic Voltammetry ◽  
Thin Layer ◽  
Electrochemical Reduction ◽  
High Reactivity ◽  
Electrochemical Methods ◽  
Tridentate Ligand ◽  
Cyclic Voltammograms ◽  
Binuclear Copper ◽  
Alkyl Chains ◽  
Binucleating Ligands

The cyclic voltammograms of some binuclear copper(II) compounds with binucleating ligands where two molecules of tridentate ligand, N, N -bis(benzimidazol-2-ylmethyl)amine are linked by several alkyl chains, were measured under both argon and dioxygen. The results demonstrate that the binuclear copper(I) species produced by electrochemical reduction exhibit high reactivity towards dioxygen, while the reaction of the corresponding mononuclear species with oxygen is very slow. Thin-layer coulometry ([binuclear copper(I)]/[O2] = 0.47 - 10.6) and thin-layer cyclic voltammetry ([binuclear copper(I)]/[O2] = 4.3 - 10.6 ) revealed that two molecules of the binuclear copper(I) species react with one molecule of dioxygen.

Electron Transport Features in Heterostructures 3C-SiC(n)/Si(p) at the Elevated Temperatures

2013 ◽  
Vol 740-742 ◽  
pp. 498-501
Author(s):  
A.V. Afanasyev ◽  
V.A. Ilyin ◽  
V.V. Luchinin ◽  
A.S. Petrov
Keyword(s):  
Electron Transport ◽  
Charge Transport ◽  
Wide Temperature Range ◽  
Silicon Substrate ◽  
Elevated Temperatures ◽  
Reverse Current ◽  
Current Generation ◽  
Temperature Range ◽  
Working Temperature ◽  
Transport Diffusion

3C-SiC (n) / Si (p) heterostructures were obtained and investigated in a wide temperature range. It was shown, the main mechanisms of charge transport diffusion and recombination. The properties of silicon substrate were determining the working temperature range of investigated diodes. Therefore the rectifying properties of 3С-SiC(n)/Si(p) diodes were stable only up to 473 K. Two sites with different activation energies were observed on the Jrev(1/T) curves at fixed voltage: 0,32 eV which, characterized states on the SiC/Si interface, Е2 ≈ 0,55 eV which corresponds to the middle of silicon bandgap and defines existence of reverse current generation component.

Thermodynamic Study of Eu3+ /Eu2+ Redox Reaction in Aqueous Solutions at Elevated Temperatures and Pressures by Means of Cyclic Voltammetry

1991 ◽  
Vol 46 (12) ◽  
pp. 1108-1116 ◽  
Author(s):  
B. A. Bilal
Keyword(s):  
Cyclic Voltammetry ◽  
Redox Potential ◽  
Redox Reaction ◽  
Elevated Temperatures ◽  
Saturation Pressure ◽  
Significant Shift ◽  
Positive Direction ◽  
Small Pressure ◽  
Increasing Temperature ◽  
Two Parameter

Abstract The redox potential of the couple Eu3+/Eu2+ in aqueous NaCl, NaClO4 and Na2SO4 solutions of different ionic strength and various pH values has been determined by means of cyclic voltammetry up to 458 K and 1 kbar. In all cases reversible voltammograms were obtained. Compared to the redox potential in C1O4- solutions of pH 2, no significant shift was observed in Cl-solutions of the same pH, whereas a drastic shift to more negative potentials in solutions of SO2-4 and in Cl- solutions of higher pH (pH 3-5) was obtained. This indicates a negligible complexation of Eu3* by means of CP but a strong one by means of OH and SO2-4 . An isothermal pressure increase up to 1 kbar led to a shift of only few mV more negative, indicating a small pressure dependence of the change of the partial molar volume (ΔVe1) accompanying the redox reaction, which results in this case only due to the different degrees of electrostriction. A more drastic shift of the redox potential (in the positive direction) results with increasing temperature. The isobaric temperature dependence of the redox potential is described by a two parameter equation which remains valid up to the saturation pressure at 458 K, due to the small pressure effect. ΔS and ΔH of the redox reaction has been determined

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