• Corrosion Science and Technology
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• 제4권6호
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• pp.242-249
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• 2005

A lot of parts in FGD (Flue Gas Desulfurization) systems of fossil-fuel power plants show the environments in which are highly changeable and extremely acidic corrosive medium according to time and locations, e.g. in duct works, coolers and re-heaters etc. These conditions are formed when system materials are immersed in fluid that flows on them or when exhausted gas is condensed into thin layered acidic medium to contact materials of the system walls and roofs. These environments make troublesome corrosion and air pollution problems that are occurred from the leakage of the condensed solution. To cathodically protect the metallic structures in extremely acidic fluid, the properties of the protective coatings on the metal surface were very important, and epoxy Novolac coating was applied in this work. On the base of acid immersion tests, hot sulfuric acid decreased the hardness of the coatings and reduced greatly the content of $Na_2O$, $Al_2O_3$, and $SiO_2$ among the main components of the coating. A special kind of CP(Cathodic Protection) system has been developed and tested in a real scale of the FGD facility. Applied coating for this CP system was peeled off and cracked in some parts of the facility. However, the exposed metal surface to extremely acidic fluid by the failure of the coatings was successfully protected by the new CP system.

• 한국해양공학회지
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• 제21권4호
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• pp.61-65
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• 2007

In this research, we have developed a manufacturing process for seawater salt by horizontal spray drying technique using the deep ocean water and seaweed(sea tangle). Deep ocean water, strong acidic electrolyzed water and strong alkaline electrolyzed water were used as extraction solvent of seaweed. Sodium content in seaweed extract solution by strong alkaline electrolyzed water was 1.63(mg/g), which was 3.5 times lower than of seaweed extract by strong acidic electrolyzed water. Major mineral content(Na, K, Ca) in seawater salt by deep ocean water were higher than strong acidic electrolyzed water and strong alkaline electrolyzed water. On the contrary, Mg contents in seawater salt by deep ocean water were lower than strong acidic electrolyzed water and strong alkaline electrolyzed water. Based on the results of seawater salt production using seaweed, it is possible to make law-salt efficiently.

• Carbon letters
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• 제14권1호
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• pp.34-39
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• 2013

Acrylonitrile (AN)-acrylamide (AM) copolymers were prepared by nitric acidic hydrolysis of homopolyacrylonitrile. The acrylamino group increased as a function of hydrolysis time, while crystallinity decreased. Differential scanning calorimetry and a thermal gravimetric analysis indicated that the acylamino introduced by acidic hydrolysis effectively enhanced the cyclization reaction at low temperature due to the change of the cyclization reaction mechanism. Char-yield of AN-AM copolymers also gradually increased with increasing hydrolysis time. The maximum char-yield was 49.48% when hydrolized at $23^{\circ}C$ in 65% nitric acid solution for 18 h, which was 30% higher than that of non-acidic hydrolysis of homopolyacrylonitrile. Simulation of the practical process also showed an increase of char yields, where the char yields were 55.43% and 62.60% for homopolyacrylonitrile and copolyacrylonitrile, respectively, with a hydrolysis time of 13 h.

• Carbon letters
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• 제6권1호
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• pp.25-30
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• 2005

The electrosorption of U(VI) from waste water was carried out by using an activated carbon fiber (ACF) felt electrode in a continuous electrosorption cell. In order to enhance the electrosorption capacity at a lower potential, the ACF was electrochemically modified in an acidic and a basic solution. Pore structure and functional groups of the electrochemically modified ACF were examined, and the effects of the modification conditions were studied for the adsorption of U(VI). Specific surface area of all the ACFs was decreased by this modification. The amount of the acidic functional groups decreased with a basic modification, while the amount increased a lot with an acidic modification. The electrosorption capacity of U(VI) decreased on the acid modified electrode due to the shielding effect of the acidic functional groups. The base modified electrode enhanced the capacity due to a reduction of the acidic functional groups. The electrosorption amount of U(VI) on the base modified electrode at .0.3 V corresponds to that of the as-received ACF electrode at .0.9 V. Such a good adsorption capacity was due to a reduction of the shielding effect and an increase of the hydroxyl ions in the electric double layer on the ACF surface by the application of negative potential.

• 한국응용과학기술학회지
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• 제30권3호
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• pp.504-517
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• 2013

The purpose of this study was to process extraction and separation for polyglucose porpyran from pophyra yezoensis as high yield. The acidic porphyran solution was extracted with 0.1~1N of ${\alpha},{\beta}$-dichloromaleic acid or ${\alpha}$-chloromaleic acid of 2% solution as organic acid instead of inorganic acid at $60^{\circ}C$ and then porphyran was collection of high yield to acidic solution and it was neutralization treated with 0.1N of $d-Ca(OH)_2$ solution and the mixture was conversion to porphyran salt form and treated with a shell powder of ouster and then added of ethanol as precipitator. It recovery porphyran contained of violet purple laver coloring matter was obtained as a crystalline and used for the next step without future purification to prepare of porphyran laver jam. so, The resulting porphyran and porphyran jam was characterized by it component and physical properties.

• 폴리머
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• 제27권2호
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• pp.159-166
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• 2003

폴리(비닐 알코올) 하이드로젤 입자의 표면에 음이온성을 부여하기 위하여 비닐아세테이트(VAc)와 메타아크릴산(MMA)을 현탁 공중합하였다. $^1$H-NMR을 통해서 공중합된 입자의 표면에 카르복실기가 도입되었음을 확인하였다. poly(VAc-co-MAA) 입자를 알칼리 용액에서 불균일계 비누화를 하였으며, 단독 PVAc 입자 보다 비누화 반응이 빠름을 관찰하였다. 또한 이들 입자를 산성 용액과 알칼리 용액에서 연속적으로 처리하여 입자들의 팽창 정도를 관찰하였다. 비누화된 입자들은 산성 수용액에서는 수축이 되었다가 알칼리 수용액에서는 팽창하는 가역적인 성질을 보였다. 비누화된 입자들은 다량의 수분을 흡수하는 하이드로젤 형태였으며, $^1$H-NMR, FT-IR을 통해서 하이드로젤 표면에 -COOH기가 형성된 것을 확인할 수 있었다.

• 전기화학회지
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• 제15권1호
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• pp.54-66
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• 2012

The phase-shift method and correlation constants, which are unique electrochemical impedance spectroscopy techniques for studying the linear relationship between the phase shift ($90^{\circ}{\geq}-{\varphi}{\geq}0^{\circ}$) vs. potential (E) behavior for the optimum intermediate frequency ($f_o$) and the fractional surface coverage ($0{\leq}{\theta}{\leq}1$) vs. E behavior, are proposed and verified to determine the Frumkin, Langmuir, and Temkin adsorption isotherms and the related electrode kinetic and thermodynamic parameters. At Ni/0.5 M $H_2SO_4$ and 0.1M LiOH aqueous solution interfaces, the Frumkin and Temkin adsorption isotherms (${\theta}$ vs. E) of H for the cathodic hydrogen ($H_2$) evolution, interaction parameters (g), equilibrium constants (K), standard Gibbs energies (${\Delta}G^0_{\theta}$) of H adsorption, and rates of change (r) of ${\Delta}G^0_{\theta}$ with ${\theta}$ have been determined using the phase-shift method and correlation constants. A lateral repulsive interaction (g>0) between the adsorbed H species appears. The value of K in the alkaline aqueous solution is much greater than that in the acidic aqueous solution.

• Korea-Australia Rheology Journal
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• 제16권4호
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• pp.175-182
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• 2004

Colloidal coating solution was prepared to enhance the hydrophilic property of the film surface. Water and ethanol were used as the dispersion media and (glycidoxypropyl) trimethoxysilane (GPS) as a binder in the colloidal silica coatings. Ethylene diamine was added to the colloidal silica solution as the curing agent. The colloidal silica solution was regarded as a hard-sphere suspension model with low volume fraction of the silica particles. Rheological properties of the silica suspensions modified with GPS have been investigated as a function of pH and concentration. The acidic solution showed high viscosity change by fast hydrolysis reaction and adsorption of the organic binders on the surface of silica particles. However, the hydrolysis was slow at the basic condition and the binders combined with themselves by condensation. The viscosity change was smallest at pH 7. The viscosity increased with the curing time after adding ethylenediamine, and the increase of viscosity at low pH was higher than that at high pH. The hydrophilic properties of the coating film were investigated by the contact angle of water and film surface. The smallest contact angle was shown under the strong acidic condition of pH 2.

• Tribology and Lubricants
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• 제18권4호
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• pp.299-304
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• 2002

This paper reports the studies on the wear-corrosion behavior of ductile cast iron in the acidic environment. In atmosphere and variety of pH solution, specific wear rate and wear-corrosion characteristics of GCD 60 with various sliding speed and distance were investigated. And electrochemical polarization test of GCD 60 was examined in the environment of various pH values. The main results are as following : As the contact pressure increases, the critical velocity of specific wear rate becomes transient at low sliding speed. As pH value becomes low, wear-corrosion loss increases in the aqueous solution. As the corrosion environment is acidified, corrosion potential of GCD 60 becomes noble and corrosion current density increases.

• E2M - 전기 전자와 첨단 소재
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• 제7권6호
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• pp.496-503
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• 1994

In recent years Sol-Gel processing provides an interesting alternative method for the fabrication of ferroelectric thin layers and powder. PZT powder was prepared from an alkoxide-based solution by a Sol-Gel method. Gelation of synthesized complex solutions, microstructure, thermal analysis and crystallization behaviors of the calcined powder were studied in accordance with a water content and a catalyst. Especially gelation and crystallization behavior were analysed with the change of pH. The gelation time decreased as the pH of the mixed solution increased. For PZT powder with 650.deg. C heat treatment, 100% perovskite phase was formed by using either acidic or basic catalyst. By using either acidic or basic catalyst, we were able to get very fine powders of uniform shape with an average particle size of 0.8-1.mu.m.