• Title/Summary/Keyword: acid strength

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Fabrication of Porous Alumina Mold for the Casting Process of Fine Ceramics (Fine Ceramics의 Casting공정을 위한 다공질 알루미나 몰드의 제조)

  • 박한수
    • Journal of the Korean Ceramic Society
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    • v.36 no.1
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    • pp.89-96
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    • 1999
  • Manufacturing conditions of the porous alumina mold were established to overcome various limits of the gypsum mold. For the preparations of the porous alumina mold, an activated charcoal was added to the Al2O3 with the wt% variation and then mixed. The binary slurry was study dispersed based on the examination of the ESA and rheological behaviro. The cylinder type alumina mold was cast in the gyspum mold and characterized by the shrinkage rate at the variable sintering temperature and the resistance against wear. It was proper to make a sintering of the Al2O3 by the surface diffusion which was non-shrinkage sintering mechansim, and intergranular neck growed stronger while sintering was being made. We studied a sintering by three categories; 1) thermodynamic method below 1,000$^{\circ}C$, 2) kinetic method above 1,000$^{\circ}C$ and 3) combined method. In the results of the respective works, combined method was superiro to the others. The prepared Al2O3 mold had relatively high strength, low drying rate, the resistance against the acid or base and good casting behavior.

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Research of Characterization of Covalently Cross-linked SPEEK/Cs-Substituted MoPA/Ceria 1wt% Composite Membrane for Water Electrolysis (Cs 치환에 따른 수전해용 공유가교 SPEEK/Cs(n)-MoPA/Ceria 1%(n = 1~3) 복합막의 특성 연구)

  • Park, Daeyoung;Hwang, Sungha;Oh, Seunghee;Yoon, Daejin;Kang, Ansoo;Moon, Sangbong;Chung, Janghoon
    • Transactions of the Korean hydrogen and new energy society
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    • v.25 no.1
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    • pp.1-10
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    • 2014
  • Ceria ($CeO_2$) was used to scavenge free radicals which attack the membrane in the polymer electrolyte membrane water electrolysis (PEMWE) circumstance and to increase the duration of the membrane. In order to improve the electrochemical, mechanical and electrocatalytic characteristics, engineering plastic of the sulfonated polyether ether ketone (SPEEK) as polymer matrix was prepared in the sulfonation reaction of polyether ether ketone (PEEK) and the organic-inorganic blended composite membranes were prepared by sol-gel casting method with loading the highly dispersed ceria and cesium-substituted phophomolybdic acid(Cs-MoPA) with cross-linking agent contents of 0.01mL. In conclusion, CL-SPEEK/$Cs_{(2.5)}$-MoPA/ceria(1%) membrane showed the optimum results such as 0.1095S/cm of proton conductivity at $80^{\circ}C$, 2.906meq./g-dry-membrane of ion exchange capacity and mechanical characteristics, and 49.73MPa of tensile strength which were better than Nafion 117 membrane.

Performance of Modified-Silicon Carbide Fiber Composites Membrane for Polymer Exchange Membrane Fuel Cells (표면처리된 실리콘 카바이드 섬유 복합막의 고분자 전해질 막 연료전지 성능)

  • Park, Jeong Ho;Kim, Taeeon;Juon, Some;Cho, Yongil;Cho, Kwangyeon;Shul, Yonggun
    • Transactions of the Korean hydrogen and new energy society
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    • v.25 no.1
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    • pp.28-38
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    • 2014
  • The organic-inorganic composite membrane in polymer exchange membrane fuel cells (PEMFCs) have several fascinating technological advantages such as a proton conductivity, thermal stability and mechanical properties. As the inorganic filler, silicon carbide (SiC) fiber have been used in various fields due to its unique properties such as thermal stability, conductivity, and tensile strength. In this study, composite membrane was successfully fabricated by modified-silicon carbide fiber. Modified process, as a novel process in SiC, takes reaction by phosphoric acid after oxidation process (generated homogeniusly $SiO_2$ layer on SiC fiber). The mechanical property which was conducted by tensile test of the 5wt% modified-$SiO_2@SiCf$ composite membrane was better than that of Aquivion casting membrane as well as ion cxchange capacity(IEC) and proton conductivity. In addition, the single cell performance was observed that the 5wt% modified-$SiO_2@SiCf$ composite membrane was approximately $0.2A/cm^2$ higher than that of a Aquivion casting electrolyte membrane and electrochemical impedance was improved with the charge transfer resistance and membrane resistance.

Properties of the Alkali Activated Mortar According to Metakaolin Replacement Ratio (알칼리 활성화 모르타르의 메타카올린 치환율에 따른 특성)

  • Seo, Dong-Hyeon;Hyung, Won-Gil
    • Journal of the Korea Institute of Building Construction
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    • v.16 no.4
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    • pp.313-320
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    • 2016
  • The aim of this study is to look into the metakaolin replacement ratio of blast furnace slag based alkali activated slag mortar and its mechanical characteristics according to changes in stimulant concentration. Metakaolin has high fineness, and therefore the fluidity becomes lower as the replacement ratio becomes higher. So in this study, a sufficient value of mixing water was provided to secure fluidity for the characteristic experiment, and a different W/B was derived for each specimen in order to make the fluidity identical. A characteristic experiment was conducted according to the mol concentration of NaOH, which was used as the mixing water that affects fluidity. Additionally, compressive strength measurement, observation of inner microstructure through SEM, acid resistance experiment, and neutralization resistance was conducted. The results of this study revealed that for a high concentration NaOH solution to have even fluidity, a high W/B is necessary, and the functions were enhanced, not degraded.

Evaluation of Ceramics, Alumina and Silicone Carbide Added Concrete Surface Protecting Agent (세라믹스, 알루미나 및 실리콘 카바이드 혼합물이 첨가된 콘크리트 표면보호재의 성능 평가)

  • Kong, Jin-Hee;Kim, Young-Geun;Oh, Sang-Keun
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2009.11a
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    • pp.43-46
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    • 2009
  • The purpose of this study is to enhance durability of concrete structures that uses this surface protecting material by carrying out the performance test of the surface protecting material of concrete, and as s result, we reached out the conclusion as follow. 1. As a result of the test measuring the stability and adhesive power of conductive film against ultraviolet, freezing & thawing, and damage from seawater that deteriorate the surface protecting material, it was turned out to meet the performance criteria specifying in the KS standard enough to gain a good evaluation to use as a surface protecting material. 2. As a result of the test identifying the neutralization-furtherance, it was assessed to be capable of protecting effectively concrete structures from carbonic acid gas by a very low depth of 0.1mm of neutralization. 3. As a result of the test identifying Penetrated Resistance Properties of chloride ion, as it was turned out to have a very low value of 819 Coulombs, it was assessed that even in the environment where the corrosion by chloride such sea environment is very affective, the film can effectively protect the concrete structure. 4. As a result of the test identifying freezing & thawing, as there was no change in reduction of mass after 400 cycle, it was assessed that the film has a good resistance against freezing & thawing. According to the results of study above, it is expected that this technology can extend its durability of concrete structure and be widely used for concrete structure through means (methods) to prevent the neutralization and damage from seawater as original purposes of the surface protecting material.

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Dehydrogenation of Ethylbenzene to Styrene with CO2 over TiO2-ZrO2 Bifunctional Catalyst

  • Burri, David Raju;Choi, Kwang-Min;Han, Sang-Cheol;Burri, Abhishek;Park, Sang-Eon
    • Bulletin of the Korean Chemical Society
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    • v.28 no.1
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    • pp.53-58
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    • 2007
  • In the dehydrogenation of ethylbenzene to styrene, CO2 could play a role as an oxidant to increase conversion of ethylbenzene and stability as well over TiO2-ZrO2 mixed oxide catalysts. TiO2-ZrO2 catalysts were prepared by co-precipitation method and were characterized by BET surface area, bulk density, X-ray diffraction, temperature programmed desorption of NH3 and CO2. These catalysts were found to be X-ray amorphous with enhanced surface areas and acid-base properties both in number and strength when compared to the respective oxides (TiO2 and CO2). These catalysts were found to be highly active (> 50% conversion), selective (> 98%) and catalytically stable (10 h of time-on-stream) at 600 oC for the dehydrogenation of ethylbenzene to styrene. However, in the nitrogen stream, both activity and stability were rather lower than those in the stream with CO2. The TiO2-ZrO2 catalysts were catalytically superior to the simple oxide catalysts such as TiO2 and ZrO2. The synergistic effect of CO2 has clearly been observed in directing the product selectivity and prolonging catalytic activity.

New Polytriazoleimides with High Thermal and Chemical Stabilities

  • E, Yanpeng;Wan, Liqiang;Li, Yujing;Huang, Farong;Du, Lei
    • Bulletin of the Korean Chemical Society
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    • v.33 no.7
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    • pp.2193-2199
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    • 2012
  • A series of novel polytriazoleimides were prepared from various aromatic dianhydrides and a new kind of 1,2,3-triazole-containing aromatic diamine synthesized by the Cu (I)-catalyzed 1,3-dipolar cycloaddition reaction in DMAc, and characterized by FT-IR, $^1H$-NMR, XRD, DSC and TGA techniques. The results show the polytriazoleimides are soluble in most of strong polar solvents and have inherent viscosity values of 0.51-0.62 dL/g(DMAc). The polytriazoleimide films exhibit a tensile strength of 62.3-104.5 MPa and an elongation at breakage of 4.0-8.1%, a glass transition temperature ($T_g$) of $257-275^{\circ}C$, a decomposition temperature (at 5% weight loss) of $350-401^{\circ}C$ in $N_2$ atmosphere, and a dielectric constant of 2.47-3.01 at 10 MHz, which depend on the structure of the polymers. The polytriazoleimides perform good resistance to acid and alkali solution.

The Preparation and Characteristics of Covalently Cross-Linked SPEEK/Cs-TPA/Ceria Composite Membranes for Water Electrolysis (수전해용 공유가교 SPEEK/Cs-TPA/Ceria 복합막의 제조 및 특성 연구)

  • Song, Minah;Ha, Sungin;Park, Deayong;Ryu, Cheolhwi;Moon, Sangbong;Kang, Ansoo;Chung, Janghoon
    • Transactions of the Korean hydrogen and new energy society
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    • v.23 no.5
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    • pp.437-447
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    • 2012
  • Ceria ($CeO_2$) was used to scavenge free radicals which attack the membrane in the polymer electrolyte membrane water electrolysis (PEMWE) circumstance and to increase the duration of the membrane. In order to improve the electrochemical, mechanical and electrocatalytic characteristics, engineering plastic of the sulfonated polyether ether ketone (SPEEK) as polymer matrix was prepared in the sulfonation reaction of polyether ether ketone (PEEK) and the organic-inorganic blended composite membranes were prepared by sol-gel casting method with loading the highly dispersed ceria and cesium-substituted tungstophosphoric acid (Cs-TPA) with cross-linking agent contents of 0.01 mL. In conclusion, CL-SPEEK/Cs-TPA/ceria (1%) membrane showed the optimum results such as 0.130 S/cm of proton conductivity at $80^{\circ}C$, 2.324 meq./g-dry-membrane of ion exchange capacity and mechanical characteristics, and 65.03 MPa of tensile strength which were better than Nafion 117 membrane.

Studies on the Refining and Utilization of Filefish Viscera Oil 2. Utilization of Filefish Viscera Oil (말쥐치 내장유의 정제 및 이용에 관한 연구 2. 말쥐치 내장유의 이용)

  • 강훈이;대도해명;소천천추;김동연;이응호
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.21 no.2
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    • pp.181-186
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    • 1992
  • For the effective utilizing of refined filefish viscera oil, it was added to fish meat paste based products as a dietary supplement of polyunsaturated fatty acids. The storage stability and physicochemical properties of the product(kamaboko) was tested. Lipid oxidation of kamaboko could be retarded and texture expressed as jelly strength could be enhanced by adding of emulsion curd prepared from water, refined filefish viscera oil and soybean protein and sodium erythorbate during the storage at 5$^{\circ}C$. These results suggested the possibility that the refined filefish viscera oil containing highly polyunsaturated fatty acid, especially EPA and DHA could be used as a food ingredient for dietary supply of the lipids.

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Anti-degradation of Various Mortar Mixtures Depending on Oil Submerging Conditions (모르타르 배합비별 각종 유지류 침지에 따른 열화저항성)

  • Han, Cheon-Goo;Hwang, Chan-Woo
    • Journal of the Korea Institute of Building Construction
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    • v.17 no.3
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    • pp.219-225
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    • 2017
  • The durability factors of concrete has been researched by many researchers. Among the chemical ingression by acid, alkali, or salt, specially the ingression by sulfate has been actively studied and reported. Generally, for the oil type chemical, it is reported to cause the excessive expansion of cement mortar and further to cause the collapse, while there was no enough research on influence of oil type, relationship with microstructure of mortar, and collapse pattern. Therefore, in this research, using the various oils from general market, the degradation properties of the mortar mixtures with various mix designs were evaluated. according to the experiment, Bio diesel damaged worst and the mix design with less cement content showed the worst damage against oils.