• Bulletin of the Korean Chemical Society
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• v.29 no.7
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• pp.1323-1325
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• 2008

The acetylene black (AB) was dispersed into water in the presence of dihexadecyl hydrogen phosphate (DHP) via ultrasonication, resulting in a stable and well-distributed AB/DHP suspension. After evaporation of water, an AB/DHP composite film-modified electrode was prepared. The electrochemical responses of $K_3$[Fe$(CN)_6$] at the unmodified electrode, DHP film-modified electrode and AB/DHP film-modified electrode were investigated. It is found that the AB/DHP film-modified electrode possesses larger surface area and electron transfer rate constant. Furthermore, the electrochemical behaviors of 1-naphthylacetic acid (NAA) were examined. At the AB/DHP film-modified electrode, the oxidation peak current of NAA remarkably increases. Based on this, a sensitive and convenient electrochemical method was proposed for the determination of NAA. The linear range is in the range from $4.0 {\times} 10^{-8}\;to\;5.0 {\times} 10^{-6}$ mol $L^{-1}$, and the detection limit is $1.0 {\times} 10^{-8}$ mol $L^{-1}$. Finally, this new sensing method was employed to determine NAA in several soil samples.

• Membrane Journal
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• v.26 no.2
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• pp.152-158
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• 2016

The Chlor-alkali (CA) membrane cell is a major electrolysis system to produce valued chemicals such as chlorine gas and sodium hydroxide. The CA membrane process has been attracted in the industries, since it has relatively low energy consumption when compared with other CA processes. The key component in CA process is perfluorinated sulfonic acid ionomer membranes, which provide ion-selectivity and barrier properties to produced gases. Unfortunately, there is limited information to determine which factors should be satisfied for CA applications. In this study, the influences of PFSA membranes on CA performances are disclosed. They include ion transport behaviors, gas evolution capability, and chemical/electrochemical resistances under CA operation conditions.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3549-3552
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• 2010

The complex formation between diazocalix[4]dipropyl (1) and diazocalix[4]crown-6 ether (2) with alkali, alkaline earth and transition metal ions was investigated by voltammetry. Electrochemical properties of compounds 1 and 2 and their selectivity toward metal ions were evaluated in $CH_3CN$ solution by comparison of voltammetric behaviors of two phenols in each compound. Compounds 1 and 2 showed almost same voltammetric behavior which is two irreversible oxidation peaks caused by intramolecular hydrogen bonding between two phenols in 1 and 2. While, however, upon interacting with various metal ions, 1 with two propyl ether groups showed no significant changes in voltammetry, 2 with crown ether group caused significant voltammetric changes upon the addition of $Ba^{2+}$ to 2. Their behavior is closely related to the complex formation by entrapment of metal ion into crown ether cavity, and ion-dipole interaction between metal ion and two phenolic groups in calix[4]crown-6.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.923-927
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• 2017

Metal exposed to high temperature/high pressure/oxidizer-rich environment may cause rapid oxidation(ignition and combustion). Therefore, this study was performed for the selection of metal appropriate for high temperature/high pressure/oxidizer-rich environment. In order to make the high temperature, high pressure and oxidizer-rich environment, the test facility utilizing the catalytic reaction of hydrogen peroxide was constructed and the metal oxidation and ignition of the STS series metals were evaluated. The result showed that the change of the selected material (discoloration) and the surface roughness were observed, but the change in the weight and thickness of the specimen was not significant.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1999.11a
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• pp.23-29
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• 1999

Experimental studies are conducted to investigate the flame stability and the thermal/fuel NOx formation characteristics of the low calorific value (LCV) coal derived gas fuel. Synthetic LCV fuel gas is produced by mixing carbon monoxide, hydrogen, nitrogen and ammonia on the basis that the thermal input of the syngas fuel into a burner is identical to that of natural gas. The syngas mixture is fed to and burnt with air on flat flame burner. With the variation of the equivalence ratio for specific syngas fuel, flame behaviors are observed to identify the flame instability due to blow-off or flashback and to define stable combustion range. Measurements of NOx content in combustion gas are made for comparing thermal and fuel NOx from the LCV syngas combustion with those of the natural gas one. In addition, the nitrogen dilution of the LCV syngas is preliminarily attempted as a NOx reduction technique, and its effects on thermal and fuel NOx production are discussed.

• Bulletin of the Korean Chemical Society
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• v.8 no.4
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• pp.242-246
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• 1987

The hydrogen abstraction reactions of $SiH_4, SiH_2Cl_2 \;and\; SiHCl_3$ by ground state chlorine atoms generated photochemically from chlorine molecules have been studied at temperatures between 15 and $100^{\circ}C.$ The absolute rates for the reactions have been obtained by a competition technique using ethane as a competitor. The rate expressions ($in cm^3/mol/s$) are found to conform to an Arrhenius rate law: $k_{SiH_4} = (7.98 {\pm} 0.42) {\times} 10^{13}$ exp $[-(1250 {\pm}20)/T].$ $k_{SiH_2Cl_2} = (2.25 {\pm} 0.12) {\times} 10^{15}$ exp[-(1010 ${\pm}$ 10)/T]. $k_{SiHCl_3} = (9.04 {\pm} 0.28) {\times} 10^{14}\; exp[-(1200 {\pm} 10)/T].$ The activation energies obtained from this study represent the same trend as with the carbon analogues, while this trend was not found with respect to the bond dissociation energies among silicon compound homologues. These anomalous behaviors were interpreted in terms of electronic effects and of the structural differences between these compounds.

• Nuclear Engineering and Technology
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• v.54 no.9
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• pp.3215-3224
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• 2022

Latest studies found that for 316LN austenitic stainless steel (ASS), its LCF life decreased noticeably in high temperature water containing a great amount of dissolved oxygen (DO) (2 ppm DO), compared with that in the water containing 50 or 100 ppb DO. This finding is different from previous studies about ASSs. This study confirmed that the 316L had similar behavior to 316LN. The LCF life of 316L in water containing 1000 ppb DO water was considerably shorter than that in the water containing 50 ppb DO. Addition of boric acid & lithium hydroxide and pre-soaking did not display noticeable effects on the LCF life of this material in the water with 1000 ppb DO, indicating the discrepancy between the latest studies and previous studies was not caused by the boric acid & lithium hydroxide and pre-soaking. This study also confirmed that similar to 316LN, when a certain amount of DO was added into the water, the amount of hydrogen absorbed into the material decreased significantly compared with that when the DO was less than 5 ppb.

• Geomechanics and Engineering
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• v.33 no.2
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• pp.121-131
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• 2023

Clay sedimentation has been widely analyzed for its application in a variety of geotechnical constructions such as mine tailing, artificial islands, dredging, and reclamation. Chemical flocculants such as aluminum sulfate (Al₂(SO₄)₃), ferric chloride (FeCl₃), and ferric sulfate (Fe(SO₄)₃), have been adopted to accelerate the settling behaviors of clays. As an alternative clay flocculant with natural origin, this study investigated the settling of xanthan gum-treated kaolinite suspension in deionized water. The sedimentation of kaolinite in solutions of xanthan gum biopolymer (0%, 0.1%, 0.5%, 1.0%, and 2.0% in a clay mass) was measured until the sediment height was stabilized. Kaolinite was aggregated by xanthan gum via a direct electrical interaction between the negatively charged xanthan gum molecules and positively charged edge surface and via hydrogen bonding with kaolinite particles. The results revealed that the xanthan gum initially bound kaolinite aggregates, thereby forming larger floc sizes. Owing to their greater floc size, the aggregated kaolinite flocs induced by xanthan gum settled faster than the untreated kaolinite. Additionally, X-ray computed tomography images collected at various depths from the bottom demonstrated that the xanthan gum-induced aggregation resulted in denser sediment deposition. The findings of this study could inspire further efforts to accelerate the settling of kaolinite clays by adding xanthan gum.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.640-647
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• 2023

Material corrosion in nuclear power plant (NPP) is not controlled only by amine injection but also by ion exchange (IX) which is the best option to remove trace Na⁺. This study was conducted to understand the Na⁺ leakage characteristics of IX beds packed with ethanolamine-form (ETAH-form) and hydrogen-form (H-form) resins in the simulated water-steam cycle in terms of intrinsic behaviors of four kinds of cation-exchange resins through ASTM test and Vanselow mass action modeling. Na⁺ was inappreciably escaped throughout the channel created in resin layer. Na⁺ leakage from IX bed was non-linearly raised because of its decreasing selectivity with increasing Na⁺ capture and with increasing the fraction of ETAH-form resin. Na⁺ did not reach the breakthrough earlier than ETAH⁺ and NH₄⁺ due to the increased selectivity of Na⁺ to the cation-exchange resin (H⁺ < ETAH⁺ < NH₄⁺ ≪ Na⁺) at the feed composition. Na⁺ leakage from the resin bed filled with small particles was decreased due to the enhanced dynamic IX processes, regardless of its low selectivity. Thus, the particle size is a predominant factor among intrinsic properties of IX resin to reduce Na⁺ leakage from the condensate polishing plant (CPP) in NPPs.

• Tribology and Lubricants
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• v.40 no.3
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• pp.84-90
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• 2024

This study investigates the effect of the surface microstructure on the tribological characteristics of glass substrates. Chemical etching using hydrofluoric acid and ammonium hydrogen fluoride was employed to create controlled asperity structures on glass surfaces. By varying the etching time from 10 to 50 min, different surface morphologies were obtained and characterized using optical microscopy, surface roughness measurements, and water contact angle analysis. Friction tests were performed using a stainless steel ball as the counter surface to evaluate the tribological behavior of the etched specimens. The results showed that the specimen etched for 20 min exhibited the lowest and most stable friction coefficient, which was attributed to the formation of a uniform and dense asperity structure that effectively reduced the stress concentration and wear at the contact interface. In contrast, specimens etched for shorter (10 min) or longer (30-50 min) durations displayed higher friction coefficients and accelerated wear owing to nonuniform asperity structures that led to local stress concentration. Optical microscopy of the wear tracks further confirmed the superior wear resistance of the 20-minute etched specimen. These findings highlight the importance of optimizing the etching process parameters to achieve the desired surface morphology for enhanced tribological performance, suggesting the potential of chemical etching as a surface modification technique for various materials in tribological applications.