• Economic and Environmental Geology
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• v.40 no.4
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• pp.491-496
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• 2007

This study conducted a chemical experiment on the Leisegang phenomenon, which is known to be the principle of rhyolite formation, and analyzed the results. Even if the same chemical elements precipitated, the shape of Leisegang rings was different according to the condition of medium and depending on inner electrolyte and outer electrolyte. The experiment used agar, gelatin and mung-bean jelly as media. We prepared 0.01M inner electrolyte containing agar 1%, gelatin 2% and mung-bean jelly 5% and curdled the solution at room temperature for 12 hours and, as a result, we obtained viscosity optimal for experimenting on the diffusion of outer electrolyte, and Leisegang rings appeared clearly according to the characteristic of each chemical element. In $PbI_2$ with solubility product($K_{sp}$) of $7.9{\times}10^{-9}$ the intervals of Leisegang rings caused by the reaction of inner electrolyte 0.01M KI and outer electrolyte 25% $Pb(NO_3){_2}$ were narrow between 0.01cm and 0.12cmm but increased gradually, but in with of $8.3{\times}10^{-17}$ the intervals of Leisegang rings caused by the reaction of inner electrolyte 0.01M KI and outer electrolyte 25% $AgNO_3$ were between 0.7cm and 0.45cm and decreased gradually. This suggests that, in the chemical formation of Leisegang rings, the interval and size of the rings are correlated with the solubility product of the precipitates.

• Journal of the Korean institute of surface engineering
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• v.51 no.1
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• pp.27-33
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• 2018

In the present work, we demonstrate the feasibility to form large inner diameter $TiO_2$ nanotubes by anodization of Ti in a HF/ethylene glycol electrolyte. In order to achieve the large inner diameter $TiO_2$ nanotubes, optimization of the anodization condition is required. We discover the key factors in the formation of large inner diameter $TiO_2$ nanotubes are concentration of water in the electrolyte, anodization temperatures, and high-applied potential. Under optimum conditions, the inner diameters of $TiO_2$ nanotubes are 379 nm. The results are approximately 3 folders larger than the general case.

• KSBB Journal
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• v.4 no.2
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• pp.150-156
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• 1989

The chaacterisitics of a commercial membrance-coverd electrode in air-saturated saline solution were investigated in terms of a steadystate one-dimensional model. The electrode system miiersed in an aqueous medium consists of three layers: an external concentration boundary layer, a membrance, and an inner electrolyte layer. The membrance can be permeabld to the water and impermeable to the ionic species. In stationary midium, the water migrates from the external medium to the inner electrolyte layer until a thermodynamic equilibrium is reached. In a following midium, however, there is a reverse direction of water movement due to the hyrodynamic pressure differential until both thickness of the electrolyte layer and the membrance are equal.

• Journal of the Korean Chemical Society
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• v.52 no.4
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• pp.356-361
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• 2008

• Corrosion Science and Technology
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• v.16 no.5
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• pp.227-234
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• 2017

Reference electrodes are generally implemented for the purpose of monitoring the cathodic protection potentials of buried or immersed metallic structures. In the market, many types of reference electrodes are available for this purpose, such as saturated calomel, silver/silver chloride and copper/copper sulfate. These electrodes contain a porous ceramic junction plate situated in the cylindrical body bottom to permit ionic flux between the internal electrolyte (of the reference electrode) and the external electrolyte. In this work, the copper/copper sulfate reference electrode was modified by replacing the porous ceramic junction plate for a metallic platinum wire. The main purpose of this modification was to avoid the ion copper transport from coming from the inner reference electrode solution into the surrounding electrolyte, and to mitigate the copper plating on the coupon surfaces. Lab tests were performed in order to compare the performance of the two mentioned reference electrodes. We verified that the experimental errors associated with the measurements conducted with developed reference electrode would be negligible, as the platinum surface area exposed to the surrounding electrolyte and/or to the reference electrolyte are maintained as small as possible.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.173.2-173.2
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• 2016

A two-step oxidation method was applied on Al6061 to debate the growth mechanism of plasma electrolytic oxidation (PEO) coating. The specimens were first oxidized in the primary electrolyte solution {$Na_3PO_4$ (8g/l), NaOH (2g/l), consequently, the specimens were transferred into a different electrolyte {$K_2ZrF_6$ (8g/l), NaOH (2g/l), $Na_2SiF_6$ (0.5g/l)} for further oxidation. The processes was conducted for various processing times. It was found the second step electrolyte component were reached to inner layers, in contrast to the primary step components which were thrustle to the outer layer. The presence of the secondary component in the inner layers were significantly varied with processing time which suggest the change in growth properties with processing time. further more the inside growth of the secondary component confirmed the increasing trend in the downward growth of the coating layer. The corrosion and hardness properties of the coatings were found highly improved with change in growth features with increasing the processing time.

• Journal of the Korean institute of surface engineering
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• v.49 no.3
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• pp.225-230
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• 2016

The present work was conducted to investigate the effects of NaF concentration in phosphate and silicate-containing alkaline electrolyte on the morphology, thickness, surface roughness and hardness of anodic oxide films formed on AZ31 Mg alloy by plasma electrolytic oxidation (PEO) method. The PEO films showed flat surface morphology with pores in the absence of NaF in the electrolyte, but nodular features appeared on the PEO film surface prepared in NaF-containing electrolyte. Numerous pores ranging from 1 to $20{\mu}m$ in size were observed in the PEO films and the size of pores decreased with increasing NaF concentration in the electrolyte. Surface roughness and thickness of PEO films showed increases with increasing NaF concentration. Hardness of the PEO films also increased with increasing NaF concentration. It was noticed that hardness of inner part of the PEO films is lower than that of outer part of them, irrespective of the concentration of NaF. The low hardness of PEO films was explained by the presence of a number of small size pores less than $2{\mu}m$ near the PEO film/substrate interface.

• Korean Journal of Metals and Materials
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• v.48 no.8
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• pp.724-729
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• 2010

The effect of potassium permanganate ($KMnO_4$) in an electrolyte on the corrosion performance of magnesium alloy coated by micro-arc oxidation (MAO) has been investigated in this study. For this purpose, MAO coating was carried out on the present sample under AC condition in an alkaline silicate electrolyte with and without $KMnO_4$. Irrespective of the addition of $KMnO_4$, it was found from structural observation that the ceramic coating layers consisted of inner and outer layers. In the sample processed in the electrolyte with $KMnO_4$, the outer layer became dense and even contained a number of $Mn_2O_3$ atoms, resulting in high corrosion resistance. Based on the results of a potentiodynamic polarization test, it was confirmed that the coating layer formed in the electrolyte with $KMnO_4$exhibited better corrosion resistance than that without $KMnO_4$. The high corrosion resistance of the MAO-treated magnesium alloy was explained in relation to the equivalent circuit model.

• Journal of the Korean institute of surface engineering
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• v.54 no.1
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• pp.30-36
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• 2021

In this study, double-layered anodizing films were formed on Al 5052 and Al 6061 alloys consecutively first in sulfuric acid and then in oxalic acid, and hardness, withstand voltage, surface roughness and acid resistance of the anodizing films were compared with single-layered anodizing films in sulfuric acid and oxalic acid electrolytes. Hardness of the double-layered anodizing film decreased with increasing ratio of inner layer to outer layer for both Al 5052 and Al 6061 alloys, suggesting that outer anodizing film formed in sulfuric acid electrolyte is damaged during the second anodizing in oxalic acid electrolyte. Withstand voltage of the double-layered anodizing films increased with increasing the thickness ratio of inner layer to outer layer. Surface roughness of the double-layered anodizing films were comparable with that of single-layered anodizing film formed in sulfuric acid but higher than that of single layer anodizing film formed in oxalic acid electrolyte. In acid resistance test, all of the double-layered and single-layered anodizing films showed good acid resistance more than 3 h without any visible gas evolution, which is attributable to sealing of pores. Based on the experimental results obtained in this work, it is possible to design a double-layered anodizing film with cost-effectiveness and improved physical and electrical properties by combining two consecutive anodizing processes of sulfuric acid anodizing and oxalic acid anodizing methods.

• International Journal of Automotive Technology
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• v.7 no.7
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• pp.867-872
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• 2006

Fuel cells are devices that convert chemical energy directly into electrical energy. Owing to the high efficiency of the fuel cells, a large number of research work have been done during these years. Among many kinds of the fuel cells, a polymer electrolyte membrane fuel cell is such kind of thing which works under low temperature. Because of the specialty, it stimulated intense global R&D competition. Most of the major world automakers are racing to develop polymer electrolyte membrane fuel cell passenger vehicles. Unfortunately, there are still many problems to be solved in order to make them into the commercial use, such as the thermal and water management in working process of PEMFCs. To solve the difficulites facing the researcher, the analysis of the inner mechanism of PEMFC should be implemented as much as possible and mathematical modeling is an important tool for the research of the fuel cell especially with the combination of experiment. By regarding some of the assumptions and simplifications, using the finite element technique, a two-dimensional electrochemical mode is presented in this paper for the further comparison with experimental data. Based on the principals of the problem, the equations of electronic charge conservation equation, gas-phase continuity equation, and mass balance equation are used in calculating. Finally, modeling results indicate some of the phenomenon in a unit cell, and the relationships between potential and current density.