Effect of Electric Field on Cation Migration and Electrode Reactions of Mortar with Different W/C Ratios

2011 ◽  
Vol 399-401 ◽  
pp. 1320-1325
Author(s):  
Chih Chien Liu ◽  
Wen Ten Kuo ◽  
Shu Wang Hsu
Keyword(s):  
Constant Current ◽  
Type I ◽  
Constant Current Density ◽  
Mortar Specimen ◽  
Electrode Reactions ◽  
Increase With Increase ◽  
Cation Migration ◽  
And Migration ◽  
Lithium Migration ◽  
Migration Technique

This study used Type I Portland cement with Na2Oeq of 0.67 % to fabricate a mortar specimen with a w/c ratio of 0.5 and a dimension of φ10 × 3 cm, adjusted to the 6 w/c ratios of 0.35, 0.40, 0.45, 0.50, 0.55 and 0.60. The specimen was applied constant current density of 9 A/m2 during the Accelerated Lithium Migration Technique (ALMT) experiment. The results show that during the application of the current, over 86.4% of the electricity applied used in the production of gas through electrode reactions, and about 3.9-4.6% in cation migration. The required time of removal for Na+ and K+ decreased with increases in w/c ratio. The average removal percentage of Na+ and K+ increasing with the increase in w/c ratio. There was a good linear relationship between the steSuperscript textSuperscript textady-state flux and migration coefficient of Li+ and w/c ratio, and the steady flux of migration coefficient increase with increase in the w/c ratio.

Influence of Aggregate Volume Ratio of Mortar on the Migration of Cations Using the Accelerated Lithium Migration Technique

2011 ◽  
Vol 230-232 ◽  
pp. 400-404
Author(s):  
Wei Chien Wang ◽  
Chih Chien Liu ◽  
Chau Lee
Keyword(s):  
Steady State ◽  
Current Density ◽  
Linear Correlation ◽  
Volume Ratio ◽  
Constant Current ◽  
Constant Current Density ◽  
Pass Through ◽  
And Migration ◽  
Lithium Migration ◽  
Migration Technique

This study utilizes mortar specimens, to design 3 different a/c ratios of 2.25, 2.75, and 3.25. The aggregate volume ratios (Vf) are 46 %, 52 %, and 57 %, respectively, while the w/c ratio is 0.5, and undergoing a 9, 12, and 15 A/m2 constant current density Accelerated Lithium Migration Technique after curing for 3 months. Results show that, on specimens applied with the same current density, the time of Li+ to pass through the specimen, and steady state flux and migration coefficient all exhibit a positive linear correlation with Vf. At the same time, the non-steady state migration coefficient for Li+ have a negative linear correlation with Vf.

Migration of Cations in Mortar under an Electrical Field Controlled by a Constant Current Density

2010 ◽  
Vol 150-151 ◽  
pp. 362-372 ◽  
Author(s):  
Wei Chien Wang ◽  
Chih Chien Liu ◽  
Chau Lee
Keyword(s):  
Current Density ◽  
Constant Current ◽  
Alkali Silica Reaction ◽  
Test Cases ◽  
Applied Current ◽  
Electrical Field ◽  
Constant Current Density ◽  
And Migration ◽  
Lithium Migration ◽  
Migration Technique

In this study, an Accelerated Lithium Migration Technique (ALMT) was applied to simultaneously drive alkali out and lithium into concrete as a remedy for alkali-silica reaction (ASR) problem. The mortar specimens used in the experiments contained 2.0% Na2Oeq. Constant current denities were applied during the ALMT testing process. The anolyte and catholyte solutions consisted of LiOH．H2O and Ca(OH)2, respectively. The results show that there are a well correlated linear relationship between the applied current density and the steady flux and migration coefficient of the Li+. During the process of ionic migration, K+ was first removed completely from the specimen, followed by Na+, after which the Li+ flux remained steady. The system resistance initially decreased, and then increased gradually. The time corresponding to when the Li+ concentration in the cathode/Li+ in the source cell was equal to 0.1% indicates the time-span needed for Li+ to penetrate throughout the specimen. Furthermore, the accumulated charge carried by the cations and the accumulated charge applied during testing showed a similar in all test cases.

Cation Migration in Mortar with Different Volume Fractions of Aggregate Affected by Electric Field

2011 ◽  
Vol 99-100 ◽  
pp. 711-714
Author(s):  
Wen Ten Kuo ◽  
Chih Chien Liu ◽  
Wei Chien Wang
Keyword(s):  
Constant Current ◽  
Type I ◽  
Negative Effects ◽  
Constant Current Density ◽  
Ion Migration ◽  
Volume Fractions ◽  
Cation Migration ◽  
Percolation Effect ◽  
Negative Effect ◽  
Pass Through

This study used Type I Portland cement with Na2Oeq of 0.67% to fabricate a mortar specimen with w/c ratio of 0.5 and a dimension of φ10  3 cm. The 7 volume fractions of aggregate (Vf) were adjusted to 0, 10, 20, 30, 40, 50 and 60%, and Acceleration Lithium Migration Technique (ALMT) experiments with 9 A/m2 constant current density were performed. The results show that for specimen with Vf of 10%, the negative effects on ion migration generated by aggregate dilution and tortuosity effects were the greatest; therefore, the removal times of Na + and K+, the time it took for Li+ to pass through the specimen and the time for Li+ to reach steady state were all longer than in the other experiments. When Vf was increased to 20 and 30%, the negative effect from the dilution and the tortuosity effects generated by the increase in Vf was cancelled the positive effect from ITZ on ion migration. When Vf was increased to over 30%, the percolation effect from ITZ controlled the behavior of ion migration. During the ALMT experiment, the anode steadily produced a large amount of O2, while the cathode produced a small amount of H2.

Reducing the Ecotoxicity of Pesticide Polluted Waters by Electrochemical Methods

2019 ◽  
Vol 70 (5) ◽  
pp. 1574-1578
Author(s):  
Cristian Neamtu ◽  
Bogdan Tutunaru ◽  
Adriana Samide ◽  
Alexandru Popescu
Keyword(s):  
Nitrogen Atmosphere ◽  
Constant Current ◽  
Polluted Water ◽  
Gaseous Nitrogen ◽  
Constant Current Density ◽  
Electrochemical Approach ◽  
Saline Waters ◽  
Thermal Combustion ◽  
Polluted Waters ◽  
Thermal Stability Of

Electrochlorination constitutes an electrochemical approach for the treatment of pesticide-containing wastewaters. This study evaluated the electrochemical and thermal stability of four pesticides and the efficiency of electrochlorination to remove and detoxify the simulated polluted water with: Acetamiprid, Emamectin, Imidacloprid and Propineb. This study reports the experimental results obtained by cyclic voltammetry and electrolysis at constant current density in association with UV-Vis spectrophotometry. In saline waters this pesticides are electrochemical active and anodic peaks are registered in the corresponding voltammograms. After thermal combustion, in a gaseous nitrogen atmosphere, a residue ranging from 15 to 45 % is observed at 500 �C.

60 GHz-Band Low-Noise Amplifier

2017 ◽  
Vol 26 (05) ◽  
pp. 1750075 ◽  
Author(s):  
Najam Muhammad Amin ◽  
Lianfeng Shen ◽  
Zhi-Gong Wang ◽  
Muhammad Ovais Akhter ◽  
Muhammad Tariq Afridi
Keyword(s):  
Transmission Line ◽  
Quality Factor ◽  
Noise Figure ◽  
Cmos Technology ◽  
Low Noise ◽  
Constant Current ◽  
60 Ghz ◽  
Frequency Range ◽  
Constant Current Density ◽  
Chip Area

This paper presents the design of a 60[Formula: see text]GHz-band LNA intended for the 63.72–65.88[Formula: see text]GHz frequency range (channel-4 of the 60[Formula: see text]GHz band). The LNA is designed in a 65-nm CMOS technology and the design methodology is based on a constant-current-density biasing scheme. Prior to designing the LNA, a detailed investigation into the transistor and passives performances at millimeter-wave (MMW) frequencies is carried out. It is shown that biasing the transistors for an optimum noise figure performance does not degrade their power gain significantly. Furthermore, three potential inductive transmission line candidates, based on coplanar waveguide (CPW) and microstrip line (MSL) structures, have been considered to realize the MMW interconnects. Electromagnetic (EM) simulations have been performed to design and compare the performances of these inductive lines. It is shown that the inductive quality factor of a CPW-based inductive transmission line ([Formula: see text] is more than 3.4 times higher than its MSL counterpart @ 65[Formula: see text]GHz. A CPW structure, with an optimized ground-equalizing metal strip density to achieve the highest inductive quality factor, is therefore a preferred choice for the design of MMW interconnects, compared to an MSL. The LNA achieves a measured forward gain of [Formula: see text][Formula: see text]dB with good input and output impedance matching of better than [Formula: see text][Formula: see text]dB in the desired frequency range. Covering a chip area of 1256[Formula: see text][Formula: see text]m[Formula: see text]m including the pads, the LNA dissipates a power of only 16.2[Formula: see text]mW.

Study on Special Morphology Hydroxyapatite Bioactive Coating by Electrochemical Deposition

2013 ◽  
Vol 537 ◽  
pp. 256-260
Author(s):  
Cai Ge Gu ◽  
Qian Gang Fu ◽  
He Jun Li ◽  
Jin Hua Lu ◽  
Lei Lei Zhang
Keyword(s):  
Electrochemical Deposition ◽  
Current Density ◽  
Electrolyte Concentration ◽  
Spherical Particles ◽  
Constant Current ◽  
Constant Current Density ◽  
Depth Direction ◽  
Special Morphology ◽  
Calcium Phosphate Coatings ◽  
Coating Weight

Bioactive calcium phosphate coatings were deposited on carbon/carbon（C/C） composites using electrochemical deposition technique. The effects of electrolyte concentration and constant current density on morphology, structure and composition of the coating were systematically investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) spectroscopy. The results show that, the coating weight elevated gradually with the increase of electrolyte concentration, and the morphology of coatings changed from spherical particles to nanolamellar crystals with interlocking structure initially. Then the coating transformed into seaweed-like and nano/micro-sized crystals along the depth direction of the coating. The coatings showed seaweed-like morphology as the deposition current density was less than 20mA. With the less current density, the coating became more homogenous. However, the coating was fiakiness crysal, with needlike crystal stacked upside as the current density reached to 20mA/cm2. The coating weight was improved gradually when the current density increased from 2.5mA/cm2 to 10mA/cm2, then reduced with the increasing current density in the range of 10 to 20mA/cm2.

Growth of passive oxide films on iron and titanium under non-stationary state

2018 ◽  
Vol 36 (1) ◽  
pp. 87-104 ◽  
Author(s):  
Toshiaki Ohtsuka
Keyword(s):  
Oxide Film ◽  
Stationary State ◽  
Ph Dependence ◽  
Ring Electrode ◽  
Constant Current ◽  
Oxide Growth ◽  
Potential Sweep ◽  
Constant Current Density ◽  
Positive Direction ◽  
Passive Oxides

AbstractGrowth of passive oxides on iron and titanium under the non-stationary state was studied during constant current density (CD) oxidation and potential sweep oxidation. Increase and decrease of the thickness of the passive oxide film were determined from the relation between dissolution and growth CDs. By using rotating Fe disc-Pt ring electrode, the CDs of the dissolution from the oxide to solution and the growth of the passive oxide on iron were simultaneously measured. From the ratio of the growth CD to the dissolution CD and the pH dependence of the growth CD, a possible mechanism was discussed. Next, the growth of passive oxides on iron in pH 8.4 borate solution and on titanium in 0.1 m sulfuric acid solution during the potential sweep oxidation was examined by using three-parameter ellipsometry. Oxide growth was initially delayed when the sweep in the positive direction was started, and then the oxide film linearly grew with the potential increase. It was found that the oxide growth rate influenced the properties of the oxide film. The electric field in the oxide film during the non-stationary growth was discussed, concerned with the CD of the oxide film formation.

Degradation of Solid Oxide Fuel Cell Cathodes Accelerated at a High Water Vapor Concentration

2010 ◽  
Vol 7 (2) ◽  
Author(s):  
S. H. Kim ◽  
K. B. Shim ◽  
C. S. Kim ◽  
J. T. Chou ◽  
T. Oshima ◽  
...  
Keyword(s):  
Water Vapor ◽  
Voltage Drop ◽  
Cell Voltage ◽  
High Water ◽  
Solid Oxide ◽  
Constant Current ◽  
Vapor Concentration ◽  
Water Vapor Concentration ◽  
Oxide Fuel ◽  
Constant Current Density

The influence of water vapor in air on power generation characteristic of solid oxide fuel cells was analyzed by measuring cell voltage at a constant current density, as a function of water vapor concentration at 800°C and 1000°C. Cell voltage change was negligible at 1000°C, while considerable voltage drop was observed at 800°C accelerated at high water vapor concentrations of 20 wt % and 40 wt %. It is considered that La2O3 formed on the (La0.8Sr0.2)0.98MnO3 surface, which is assumed to be the reason for a large voltage drop.

EFFECT OF ETCHING TIME ON OPTICAL AND MORPHOLOGICAL FEATURES OF N-TYPE POROUS SILICON PREPARED BY PHOTO-ELECTROCHEMICAL METHOD

2016 ◽  
Vol 78 (3) ◽  
Author(s):  
Asad A. Thahe ◽  
Noriah Bidin ◽  
Mohammed A. Al-Azawi ◽  
Naser M. Ahmed
Keyword(s):  
Porous Silicon ◽  
Gravimetric Method ◽  
Constant Current ◽  
Etching Time ◽  
Absorption Data ◽  
Time Duration ◽  
Constant Current Density ◽  
Force Microscopy ◽  
Atomic Force ◽  
Structure Properties

Achieving efficient visible photoluminescence from porous-silicon (PSi) is demanding for optoelectronic and solar cells applications. Improving the absorption and emission features of PSi is challenging. Photo-electro-chemical etching assisted formation of PSi layers on n-type (111) silicon (Si) wafers is reported. Samples are prepared at constant current density (~30 mA/cm2) under varying etching times of 10, 15, 20, 25, and 30 min. The influence of etching time duration on the growth morphology and spectral properties are inspected. Room temperature photoluminescence (PL) measurement is performed to determine the optical properties of as-synthesized samples. Sample morphologies are imaged via Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The thickness and porosity of the prepared samples are estimated using the gravimetric method. The emission and absorption data is further used to determine the samples band gap and electronic structure properties. Results and analyzed, interpreted with different mechanisms and compared.  

Neural repetitive firing: a comparative study of membrane properties of crustacean walking leg axons

1975 ◽  
Vol 38 (4) ◽  
pp. 922-932 ◽  
Author(s):  
J. A. Connor
Keyword(s):  
Membrane Conductance ◽  
Firing Frequency ◽  
Membrane Properties ◽  
Constant Current ◽  
Repetitive Firing ◽  
Type I ◽  
Frequency Range ◽  
Type Iii ◽  
Range Type ◽  
Sucrose Gap

1. Repetitive activity and membrane conductance parameters of crab walking leg axons have been studied in the double sucrose gap. 2. The responses to constant current stimulus could be classified into three catagories; highly repetitive with wide firing frequency range, type I; highly repetitive with narrow frequency range, type II; and nonrepetitive or repetitive to only a limited degree, type III. The minimum firing frequency for type I axons was much greater than for other recording techniques. 3. Voltage-clamp currents in type III axons were qualitatively similar to those of squid or lobster axon. 4. The outward membrane currents of type I and II axons showed a transient phase in addition to the usual delayed current. The magnitude of this transient was a function of both the holding and test voltages. 5. The direction of the transient current reversed in potassium-rich saline. 6. The type I repetitive response in the walking leg axons appears to be generated by the same types of conductance changes that have been demonstrated in molluscan central neurons.

Sign in / Sign up

Export Citation Format

Share Document