Nonlinear impedance of mineral‐electrolyte interfaces: Part I. Pyrite

Geophysics ◽  
1978 ◽  
Vol 43 (6) ◽  
pp. 1222-1234 ◽  
Author(s):  
J. D. Klein ◽  
R. T. Shuey
Keyword(s):  
Low Frequency ◽  
Reference Electrode ◽  
Nonlinear Behavior ◽  
Hydrogen Gas ◽  
Polarization Curves ◽  
Reaction Products ◽  
Single Interface ◽  
Secondary Reactions ◽  
Current Densities ◽  
A Current

The impedance of the interface between an acidic electrolyte and polished electrodes of pyrite has been investigated at current densities in the nonlinear range (up to [Formula: see text]). The potential across a single interface relative to a reference electrode was measured in response to a current sinusoid of low frequency (0.002 Hz). Polarization curves, or linear plots of current density versus electrode potential, consisted of distorted Lissajous patterns. At peak current densities the interface impedance is low and is dominated by activation controlled reactions involving pyrite dissolution and hydrogen gas evolution. The polarization curves have a series of step‐like features at intermediate potentials due to current‐limited reactions. These secondary reactions involve solid and/or aqueous reaction products from previous reactions. The high impedance portion of each reaction step corresponds to a limit current caused by either depletion of a particular solid reactant or employment of a current larger than can be carried by diffusion of aqueous reactants. Nonlinear behavior of pyrite was found to be independent of carrier type and conductivity. The potential of the anodic pyrite dissolution reaction was weakly dependent on pH. Potentials of cathodic reactions increased with increasing pH, indicating the involvement of [Formula: see text], as demonstrated by the evolution of hydrogen gas and [Formula: see text] gas.

Nonlinear impedance of mineral‐electrolyte interfaces: Part II. Galena, Chalcopyrite, and Graphite

Geophysics ◽  
1978 ◽  
Vol 43 (6) ◽  
pp. 1235-1249 ◽  
Author(s):  
J. D. Klein ◽  
R. T. Shuey
Keyword(s):  
Low Frequency ◽  
Reference Electrode ◽  
Drill Hole ◽  
Hydrogen Gas ◽  
Mineral Dissolution ◽  
Nonlinear Phenomena ◽  
Reaction Products ◽  
Single Interface ◽  
Current Flows ◽  
Anodic Reactions

The impedance of the interface between an acidic electrolyte and monomineralic, polished electrodes of galena, graphite, and chalcopyrite has been investigated at current densities in the nonlinear range (up to [Formula: see text]). The potential across a single interface relative to a reference electrode was measured in response to a current sinusoid of low frequency, 0.002 Hz. Polarization curves, or linear plots of current density versus electrode potential, consisted of distorted Lissajous patterns. Onset of a new electrochemical reaction resulted in a decrease in impedance of the interface, and hence increase in slope of the polarization curve. For some reactions, the electrical characteristics were diagnostic of bulk mineral composition. Diagnostic reactions include (1) mineral dissolution and gas evolution reactions at extreme anodic and cathodic potentials, (2) reactions at intermediate potentials which involve reaction products from previous reactions. Response is thus dependent on previous reactions and therefore on sample history. Anodic reactions were generally independent of pH, and consisted primarily of mineral dissolution reactions. Potentials of cathodic reactions increased with increasing pH indicating the involvement of [Formula: see text] as demonstrated by the evolution of hydrogen gas and/or [Formula: see text] gas. The potentials of the main graphite reactions were larger in magnitude than any of the sulfide reaction potentials. Measurements with polymineralic electrodes indicate that current flows mainly through minerals with reactions at less extreme potentials and consequently reactions involving other minerals at higher potential do not occur. Due to its more extreme reaction potentials, graphite does not respond in the presence of sulfide minerals. It appears that nonlinear phenomena could be used for mineral discrimination in drill hole logging.

scholarly journals Nonlinear Behavior of the Radio Frequency Interference (RFI) Sources at Faculty of Applied Sciences, MARA University of Technology

2014 ◽  
Vol 34 ◽  
pp. 39-47
Author(s):  
Zety Sharizat Hamidi ◽  
N.N.M. Shariff
Keyword(s):  
Applied Sciences ◽  
Radio Frequency ◽  
Low Frequency ◽  
Nonlinear Behavior ◽  
Current Status ◽  
Radio Frequency Interference ◽  
Monitoring Frequency ◽  
University Of Technology ◽  
Current Scenario ◽  
A Current

In this article, we describe and compare several sources of the nonlinear of Radio Frequency Interference (RFI) based on classification methods. It is very important to characterize and understand the nature of interference in as much of the candidate spectrum as possible. Preliminary analysis has been done in 2011. As data sizes of observations grow with new and improved solar monitoring system, the need for completely automated, robust methods for RFI mitigation is highlighted. The current status of RFI noise level is being compared at two different sites (i) indoor and (ii) outdoor. The main objective is to evaluate and find the best range of low frequency in MHz for the solar monitoring purpose. Our findings are consistent with those of previous studies. There is not much different in terms of the sources of RFI. However, the level of RFI is become increase. Based on the results, it was found that the distribution of RFI sources in indoor site is in the range from -(80-105) dBm. A strong and moderate RFI can be identified in the range of -100 dBm. The dominant sources in this region are due to the fixed mobile signal with 10 points of this signal from 1-2000 MHz. If we compare with outdoor site, the distribution of RFI sources in indoor site is in the range from -(75-105) dBm. It means that the signal of noise is larger compared with indoor site. While new sources strive to remain the increasing of RFI signal levels, numerous factors interact to influence the pattern of this noise. Reporting to the authoritative body should be made to make sure the allocation of the solar monitoring frequency region was not used by other applications. This work is a current scenario of the nonlinear RFI level at our site.

On: “Effect of surface polarization on resistivity modeling” by D. Guptasarma (GEOPHYSICS, v. 48, January 1983, p. 98–106).

Geophysics ◽  
1984 ◽  
Vol 49 (3) ◽  
pp. 314-314
Author(s):  
K. Duckworth
Keyword(s):  
Stainless Steel ◽  
Current Density ◽  
Low Frequency ◽  
Input Current ◽  
Steel Cylinder ◽  
Surface Polarization ◽  
Order Of Magnitude ◽  
Current Densities ◽  
A Current ◽  
Effect Of Surface

I am glad to see that this paper confirms the resistive behavior of metallic models when immersed in electrolyte and subject to low‐frequency currents, which my coauthor and I reported in 1978 (Saydam and Duckworth, 1978). It is also gratifying that this paper confirms the transition from resistive to conductive behavior with increase of frequency which we reported in that same paper. However, I must call into question the validity of the conclusions reached by the author of this paper. I do so for several reasons, the first of which is that the author is not entitled to display complex resistivity spectra derived in a model tank environment unless evidence is provided that those spectra are invariant for a range of primary currents extending over at least two decades from an upper limit of 1 mA. I say this because a current of 1 mA, as apparently used by the author, causes severe nonlinearity in tank modeling as my coauthor and I showed in 1978 (Saydam and Duckworth, ibid). In tests of stainless steel which we performed and in tests on pyrite performed by Anderson and Keller (1964) the maximum permissible current density for linear conditions to exist was [Formula: see text]. Current densities at the surface of the aluminum cylinder of 3 cm diameter used by the authors would have been as high as [Formula: see text] when it was located at a depth of 7 mm (as quoted) directly under one of the current electrodes if the delivered current was 1 mA. It seems unlikely that aluminum would behave linearly at current densities 32 times greater than the maximum permissible for either stainless steel or pyrite, but we have no way of knowing because this paper fails to provide any experimental evidence in this regard. However, in the case of the results for a vertical stainless steel cylinder shown by the author in Figure 6 we can readily compute that if a 1 mA input current was used, the current density at the surface of the cylinder closest to the [Formula: see text] electrode would have been [Formula: see text]. Thus, in this case, linearity could only have been ensured by using an input current at least an order of magnitude lower than the 1 mA quoted by the author.

Facet Topography and Dislocation Structure as a Possible Source for Electrical Heterogeneity in [001] TILT Bicrystals of YBa2Cu3O7-δ

1996 ◽  
Vol 54 ◽  
pp. 338-339
Author(s):  
I-Fei Tsu ◽  
D.L. Kaiser ◽  
S.E. Babcock
Keyword(s):  
Grain Boundary ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Electromagnetic Properties ◽  
Length Scale ◽  
Density Values ◽  
Current Densities ◽  
Applied Fields ◽  
A Current

A current theme in the study of the critical current density behavior of YBa2Cu3O7-δ (YBCO) grain boundaries is that their electromagnetic properties are heterogeneous on various length scales ranging from 10s of microns to ˜ 1 Å. Recently, combined electromagnetic and TEM studies on four flux-grown bicrystals have demonstrated a direct correlation between the length scale of the boundaries’ saw-tooth facet configurations and the apparent length scale of the electrical heterogeneity. In that work, enhanced critical current densities are observed at applied fields where the facet period is commensurate with the spacing of the Abrikosov flux vortices which must be pinned if higher critical current density values are recorded. To understand the microstructural origin of the flux pinning, the grain boundary topography and grain boundary dislocation (GBD) network structure of [001] tilt YBCO bicrystals were studied by TEM and HRTEM.

Sample Preparation of Aluminum Bridge Test Vehicles for Tem In-Situ Crystallographic Studies of Electromigration

1987 ◽  
Vol 115 ◽  
Author(s):  
W. E. Rhoden ◽  
J. V. Maskowitz ◽  
D. R. Kitchen ◽  
R. E. Omlor ◽  
P. F. Lloyd
Keyword(s):  
High Temperature ◽  
Sample Preparation ◽  
Integrated Circuit ◽  
Circuit Reliability ◽  
Test Vehicle ◽  
Aluminum Films ◽  
Current Densities ◽  
Integrated Circuit Reliability ◽  
A Current

IntroductionElectromigration in aluminum films has been identified as an increasing concern for integrated circuit reliability. Electromigration is the mass transport of atoms in a conductor under a current stress. Electromigration occurs in conductors experiencing current densities greater than 105 A/cm2 and is accelerated by high temperature. The damage to aluminum films manifests itself in the formation of voids, hillocks and whiskers along the conductor. This paper presents a test vehicle preparation procedure which can be used to investigate electromigration.

Nitroxides as reaction intermediates

1982 ◽  
Vol 60 (12) ◽  
pp. 1414-1420 ◽  
Author(s):  
Hans Gunter Aurich
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Isopropyl Alcohol ◽  
High Reactivity ◽  
Reaction Intermediates ◽  
Reaction Products ◽  
Nitronyl Nitroxide ◽  
Reaction Conditions ◽  
Spin Resonance ◽  
Secondary Reactions

Vinyl nitroxides 4 are obtained by oxidation of the nitrones 3, as was shown by esr studies and by identification of the reaction products. The formation of 4d–f is even observed in oxidation of the hydroxylamines 1d–f, nitroxides 2d–f and nitrones 3d–f being the intermediates. The high reactivity of the vinyl nitroxides 4 at their β-position is illustrated by the reactions of 4a with various compounds affording the nitroxides 7–10, respectively. Compound 4c reacts with its precursor 3c to give 11, 12, or 13, depending on the reaction conditions. From oxidation of 3a, c, and e the dimerization products 5a, c, and e, respectively, could be isolated. Whereas further oxidation of 5d yields 6d, the acyl nitroxides 14a and c are formed in the oxidation of 5a and c, respectively.The formation of quinone 23 in the reaction of 2-methyl-2-nitrosopropane with potassium tert-butoxide in isopropyl alcohol in the presence of oxygen is discussed. The nitroxide 20 has been detected in the reaction mixture. Imines 24 react with nitrosobenzene giving nitroxides 26. These are further oxidized by nitrosobenzene to afford nitrones 27. Whereas 27a and b could be isolated, 27c and d undergo further reaction yielding the diimines 30c and d along with dinitrone 29.The formation and reactions of imino nitroxides 31 and of the nitronyl nitroxide 41 are discussed. Electron spin resonance studies revealed the high reactivity of the imidazolyl-1,3-dioxides 46 and the imidazolyl-1-oxides 50, which easily form radicals 47–49 and 51, respectively, which are derived from secondary reactions.

Nonlinear behavior of Helmholtz resonator with a compliant wall for low frequency, broadband noise control

2021 ◽  
pp. 1-29
Author(s):  
Maya Pishvar ◽  
Ryan L Harne
Keyword(s):  
Dynamic Response ◽  
Low Frequency ◽  
Nonlinear Behavior ◽  
Helmholtz Resonator ◽  
Broadband Noise ◽  
Sound Attenuation ◽  
Wall Material ◽  
Modeling Framework ◽  
Compliant Wall ◽  
Broadband Sound

Abstract Low frequency sound attenuation is often pursued using Helmholtz resonators (HRs). The introduction of a compliant wall around the acoustic cavity results in a two-degree-of-freedom (2DOF) system capable of more broadband sound absorption. In this study, we report the amplitude-dependent dynamic response of a compliant walled HR and investigate the effectiveness of wall compliance to improve the absorption of sound in linear and nonlinear regimes. The acoustic-structure interactions between the conventional Helmholtz resonator and the compliant wall result in non-intuitive responses when acted on by nonlinear amplitudes of excitation pressure. This paper formulates and studies a reduced order model to characterize the nonlinear dynamic response of the 2DOF HR with a compliant wall compared to that of a conventional rigid HR. Validated by experimental evidence, the modeling framework facilitates an investigation of strategies to achieve broadband sound attenuation, including by selection of wall material, wall thickness, geometry of the HR, and other parameters readily tuned by system design. The results open up new avenues for the development of efficient acoustic resonators exploiting the deflection of a compliant wall for suppression of extreme noise amplitudes.

Plasma-Assisted Nitriding in Low-Frequency Inductively Coupled Plasma Enhanced with Ferromagnetic Cores

2018 ◽  
Vol 37 (6) ◽  
pp. 545-550
Author(s):  
Mikhail Isupov ◽  
Vadim Pinaev ◽  
Daria Mul ◽  
Natalia Belousova
Keyword(s):  
Inductively Coupled Plasma ◽  
High Speed ◽  
Low Frequency ◽  
Sample Surface ◽  
Ion Energy ◽  
Inductively Coupled ◽  
Steel Aisi ◽  
Current Densities ◽  
Aisi 321 ◽  
Stainless Steel Aisi

AbstractAn experimental investigation of plasma-assisted nitriding of austenitic stainless steel AISI 321 in a low-pressure (7 Pa), low-frequency (50–100 kHz) nitrogen inductively coupled plasma enhanced with ferromagnetic cores has been performed at the temperatures of 470–625 °C, sample biases of ‒500–‒750 V, current densities on the sample surface of 1.2–3.3 mA/cm2 and nitriding times of 20 and 60 min. It is found that even the short (20 min) ion-plasma treatment results in the formation of nitrided layers with the thickness of up to 40 μm and microhardness of up to 9 GPa.The high speed of nitriding can be explained as a result of the joint action of high ion flux density and high ion energy on the sample surface.

scholarly journals Reprocessing of LiH in Molten Chlorides

2008 ◽  
Vol 63 (5-6) ◽  
pp. 377-384
Author(s):  
Patrick J. Masset ◽  
Armand Gabriel ◽  
Jean-Claude Poignet
Keyword(s):  
Process Design ◽  
Diffusion Coefficients ◽  
Electrochemical Techniques ◽  
Hydrogen Gas ◽  
Standard Potential ◽  
Molten Chlorides ◽  
Metallic Lithium ◽  
Production Of Hydrogen ◽  
Current Densities ◽  
Molten Phase

LiH was used as inactive material to stimulate the reprocessing of lithium tritiate in molten chlorides. The electrochemical properties (diffusion coefficients, apparent standard potentials) were measured by means of transient electrochemical techniques (cyclic voltammetry and chronopotentiometry). At 425 ºC the diffusion coefficient and the apparent standard potential were 2.5 · 10−5 cm2 s−1 and −1.8 V vs. Ag/AgCl, respectively. For the process design the LiH solubility was measured by means of DTA to optimize the LiH concentration in the molten phase. In addition electrolysis tests were carried out at 460 ºC with current densities up to 1 A cm−2 over 24 h. These results show that LiH may be reprocessed in molten chlorides consisting in the production of hydrogen gas at the anode and molten metallic lithium at the cathode.

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