• Title/Summary/Keyword: 화학 영역

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Corrosion Monitoring of Reinforcing Bars in Cement Mortar Exposed to Seawater Immersion-and-dry Cycles (해수침지-건조 환경에 노출된 모르타르속 철근의 부식속도 평가)

  • Kim, Je-kyoung;Kee, Seong-Hoon;Yee, Jurng-Jae
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.22 no.4
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    • pp.10-18
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    • 2018
  • The primary purposes of this study are to understand a fundamental aspect of current uniformity around a reinforcing bar (rebar) in cement mortar, and to develop an accurate monitoring method in a wet-dry cycling process with the alternative current (AC) impedance method. Three cement mortar specimens with two embedded rebars were prepared in the laboratory. As a main variable, the distance between two rebars was designed to be 10, 20 and 30 mm with the same thickness of 20 mm. To simulate the corrosion of rebars in concrete structures in a marine environment, three cement mortar specimens were exposed to 15 wet-drying cycles (24-hour-immersion in seawater and 48-hour-drying in a room temperature) in the laboratory. It was observed that the potential level shifted to a noble value during corrosion potential monitoring, which is attributed to acceleration of dissolved oxygen diffusion at the drying process. AC impedance was measured in a frequency range from 100 kHz to 1 mHz on a wet-drying process. A theoretical model was proposed to explain the interface condition between the rebars and cement mortar by using the equivalent circuit consisting of a solution resistance, a charge transfer resistance and a CPE (constant phase element). It was observed that the diffusion impedance appeared in a low frequency range as corrosion of rebars progresses. At the drying stage of the wet-drying cycles, the currents line for monitoring tended to be non-uniform at the interface of rebar/mortar, being phase shift, ${\theta}$, close to $-45^{\circ}$.

Phase Behavior and Structural Analyses of the THF + H2 Binary Clathrate Hydrate (THF + H2 이성분계 크러스레이트 하이드레이트의 상거동 및 구조 분석)

  • Cha, Jong-Ho;Park, Youngjune;Cha, Min-Jun;Yeon, Sun-Hwa;Lee, Huen
    • Korean Chemical Engineering Research
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    • v.46 no.6
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    • pp.1095-1099
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    • 2008
  • In this study, we investigated that hydrate formation and phase behavior of the $THF+H_2$ binary clathrate hydrates. In order to confirm the binary clathrate hydrate formation we employed the Raman and NMR spectroscopies that are known to be quite powerful tools, particularly for examining the cage occupancy pattern of guest molecules. In addition, we traced the P-T profiles from clathrate hydrate formation and dissociation process, which made it possible for the resulting phase equilibrium boundary to be clearly established. In the binary clathrate hydrate matrix we further identified that the relatively large THF molecules can only occupy the large $5^{12}6^4$ cavities, while the small $H_2$ molecules are entrapped in the empty $5^{12}$ cavities in structure-II, making the hydrate to be stable above 273 K even at relatively low pressure condition. Considering that pure $H_2$ hydrate can be produced at the extreme pressures higher that 1,000 bar, we can conclude that the water-soluble second guest inclusion induces $H_2$ storage and transportation to be readily achievable under much milder conditions.

Partial Oxidation of Methane for Hydrogen Production over Co and Ni Catalysts (수소생산을 위한 메탄 부분산화용 코발트와 니켈촉매의 반응특성 연구)

  • Lee, Sang-Sik;Hong, Ju-Hwan;Ha, Ho-Jung;Kim, Byung-Kwan;Han, Jong-Dae
    • Korean Chemical Engineering Research
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    • v.48 no.6
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    • pp.776-783
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    • 2010
  • Co and Ni catalysts supported on $Al_2O_3$ for partial oxidation of methane producing hydrogen were synthesized using impregnation to incipient wetness. The activities of these catalysts for the partial oxidation of methane was investigated at 1 atm and $CH_4/O_2=2.0$ in the temperature range of $450{\sim}650^{\circ}C$. The reaction activity of $Ni/Al_2O_3$ and $Co/Al_2O_3$ catalysts with different loading was investigated. And the beneficial effects of Ni addition to $Co/Al_2O_3$ and the promotional effects of Ce and La addition to $Ni/Al_2O_3$ and $Co/Al_2O_3$ were investigated. These catalysts were characterized by XRD and SEM/EDX. Comparing catalyst loadings, 10 wt% Co and 10 wt% Ni were found to be optimal at the experimental conditions. The 10 wt% $Ni/Al_2O_3$ and 10 wt% $Co/Al_2O_3$ catalysts in partial oxidation of methane showed $CH_4$ conversions and CO selectivity close to the thermodynamic equilibrium levels, but showed lower $H_2$ selectivity than equilibrium level. The addition of Ni to $Co/Al_2O_3$ exhibited higher $H_2$ selectivity but beneficial effect was not observed in the $CH_4$ conversion. Addition of Ce to $Co/Al_2O_3$ and addition of La to $Ni/Al_2O_3$ a improved the $CH_4$ conversion level and $H_2$ selectivity.

Fabrication of Nano $Y_{2}O_{3}-CeO_{2}$ Sintered Body Using Dispersion Stability (분산 안정성을 이용한 나노 $Y_{2}O_{3}-CeO_{2}$ 소결체의 제조)

  • Kim, Eun-Jung;Lee, Sang-Hoon;Choi, Sung-Churl
    • Journal of the Korean Ceramic Society
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    • v.38 no.9
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    • pp.853-859
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    • 2001
  • The dispersion stability of nano $Y_2O_3-CeO_2$ system was investigated using colloid surface chemistry. Green body of $Y_2O_3$ doped $CeO_2$ was prepared by slip casting in and aqueous system. The dispersion stability of suspension between powders and organic additive was accomplished through electrokinetic behavior of suspension, which was done by ESA apparatus. The dynamic mobility of particles was enhanced when the anionic dispersant of the amount of 1wt% was added. The dissolution of $Y^{3+}$ ion in suspension occurred in the acidic region so that pH value in slurries did not move to below 7.0. In the $CeO_2-Y_2O_3$ system, optimal preparation of suspension was made after adding the anionic dispersant as the amount of 1wt% and pH value of 11.0, and then slip-cast and sintered at 1400$^{\circ}$C, 2 hrs. It appeared relative density of >98% and homogeneous distribution of Y element in depth direction as well as in the microstructure of surface.

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Petrology of the Taeheung-ri Lava in Southeastern Jeju Island (제주도 남동부 태흥리 용암에 대한 암석학적 연구)

  • 윤성효;고정선;박정미
    • The Journal of the Petrological Society of Korea
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    • v.11 no.1
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    • pp.17-28
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    • 2002
  • This study has been designed to elucidate the petrography and geochemical characteristics of the Taeheung-ri lava in southeastern Jeju Island. The lava is divided into the alkaline basalt and tholeiitic basalt. More than 4 layers of tholeiitic basalt are overlain by layers of alkaline basalt. Compared with alkaline basalt, tholeiitic basalt has lower contents of $K_2O$, $P_2O_5$, Ba and Ta, but slight higher contents of $SiO_2$ and CaO. The contents of Ba and Rb of all basalts are enriched, but those of Ni and Cr are depleted compared with primitive mantle compositions. All basalts show inclined chondrite-normalized REE patterns with LREE enriched more than HREE and alkaline basalt has relatively higher. The basalts of this study area are plotted in the field of within plate basalt on the tectonomagmatic discrimination diagram. Tholeiitic basalt has higher ratios of Zr/Nb, Y/Nb, and $Al_2O_3/P_2O_5$ than alkaline basalt. Both tholeiitic and alkaline basalt are similar in their K/Ba ratios. The geochemical data suggest that the parental magma of both basalts might be produced by different degrees of partial melting of similar source mantle. The tholeiitic basalt formed by higher degree of partial melting than the alkaline basalt.

Exploring synergistic effect among essential oils in antibacterial action (항균작용에 대한 에센셜 오일들 간의 상승작용 탐색)

  • Kim, Ka-Eun;Park, Soon Kwon;Cho, Il-Young
    • Journal of Digital Convergence
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    • v.14 no.8
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    • pp.547-553
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    • 2016
  • This study was conducted to look at the antimicrobial synergistic effect of blended oil into the target skin flora. The essential oils used in antimicrobial test were 100% eucalyptus (EU), lemon (LE), lavender (LA) and four blended oils, EU+LE, LE+LA, EU+LA, and, EU+LE+LA in ratio of 1:1 and 1:1:1 respectively. As a result, LE showed the highest, LA showed the lowest antimicrobial activity among single oil group. In blended oil group, antimicrobial activity of the EU + LA showed significantly increasing effect than the sum of the antimicrobial activity of the single oil. However, the antimicrobial effects of the blend of three oils did not show any synergistic effect. This result showed that the interaction between the chemical components constituting the oil than the number of blended oil seems more significant on the synergistic effect. Therefore, blending essential oil based on scientific evidence becomes more necessary in the future.

Simulation of Plume Length Induced by Orimulsion Combustion (오리멀젼 연소시 발생하는 백연의 연기거리 전산모사)

  • Kwak, Byoung-Kyu;Kim, Jong-Ho;Joo, Ji-Bong;Lee, Jeong-Jin;Kim, Jin-Soo;Kim, Young-Hun;Yi, Jong-Heop
    • Clean Technology
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    • v.14 no.2
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    • pp.136-143
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    • 2008
  • The objective of this study is to investigate the visibility of plume at the Y power plant stack, which fires the orimulsion as a fuel. The plume contains numerous primary particles under $1\;{\mu}m$ size and inorganic ions possibly inferred by the chemicals of secondary aerosol formation. We evaluated the visibility of the plume using the modified PLUVUE-II model. The monitoring data on the particle size distribution (PSD) and secondary aerosols of sulfate were applied to estimate and evaluate the main factors of plume opacity. The chemical reactions were applied to the model for the secondary aerosol formation of $(NH_4)_2SO_4(s)$. The maximum plume length was estimated by an optic method using threshold contrast. The results showed that the plume length was strongly dependent upon the PSD and $(NH_4)_2SO_4(s)$ concentration of the plume emitted from the stack.

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타원편광분석법을 이용한 $In_xAl_{1-x}P$ 박막의 광물성 연구

  • Byeon, Jun-Seok;Hwang, Sun-Yong;Kim, Tae-Jung;Kim, Yeong-Dong;Aspnes, D.E.;Chang, Y.C.;Yun, Jae-Jin;Lee, Eun-Hye;Bae, Min-Hwan;Song, Jin-Dong
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.02a
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    • pp.423-423
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    • 2013
  • 3~5 족 반도체 물질인 phosphorus 화합물 중 대표적인 InAlP 삼종화합물은 작은 굴절률, 큰 밴드갭, GaAs와 lattice 일치 때문에 큰 주목을 받고 있고, p-type high electron mobility transistors(p-HEMT), laser diodes 등의 고속 전자소자 및 광전 소자에 응용이 가능한 매우 중요한 물질이다. 최적의 소자 응용기술을 위해서는, 정확한 광물성 연구가 수행되어야 하지만 InxAl1-xP 화합물에 대한 유전율 함수 및 전자전이점 등의 연구는 미흡한 실정이다. 이에 본 연구에서는 1.5~6.0 eV 에너지 영역에서 각기 다른 In 조성비를 갖는 InxAl1-xP 화합물의 가유전율 함수 ${\varepsilon}={\varepsilon}_1+i{\varepsilon}_2$와 전자전이점 데이터를 보고한다. GaAs 기판 위에 molecular beam epitaxy (MBE)를 이용하여 InxAl1-xP (x=0.000, 0.186, 0.310, 0.475, 0.715, 0.831, 1.000) 박막을 성장하였고 타원편광분석기를 이용하여 유전율 함수를 측정하였다. 또한 실시간 화학적 에칭을 통하여 시료 표면에 자연산화막을 제거함으로써 순수한 InAlP의 유전율 함수를 측정할 수 있었고, 측정된 유전율 함수를 이차미분하여 In 조성비에 따른 전자전이점을 얻을 수 있었다. 얻어진 전자전이점 값을 이용하여 linear augmented Slater-type orbital method (LASTO) 를 통해 이론적 전자 밴드 구조 계산을 하였고, 이를 바탕으로 $E_0$, $E_1$, $E_2$ 전이점 지역의 여러 전자전이점($E_1$, $E_1+{\Delta}_1$, $E_0'$, $E_0'+{\Delta}_0'$, $E_2$, $E_2'$)의 특성을 정의할 수 있었고, $E_0'$$E_2$ 전이점의 에너지 값이 In 조성비가 증가함에 따라 서로 교차함을 발견할 수 있었다. 타원 편광 분석법을 이용한 유전율 함수 및 전자전이점 연구는 InAlP의 광학적 데이터베이스를 확보하는 성과와 더불어 새로운 디바이스 기술 및 광통신 산업에도 유용한 정보가 될 것이다.

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Review of Site Characterization Methodology for Deep Geological Disposal of Radioactive Waste (방사성폐기물의 심층 처분을 위한 부지특성조사 방법론 해외 사례 연구)

  • Park, Kyung-Woo;Kim, Kyung-Su;Koh, Yong-Kwon;Jo, Yeonguk;Ji, Sung-Hoon
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.15 no.3
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    • pp.239-256
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    • 2017
  • In the process of site selection for a radioactive waste disposal, site characterization must be carried out to obtain input parameters to assess the safety and feasibility of deep geological repository. In this paper, methodologies of site characterization for radioactive waste disposal in Korea were suggested based on foreign cases of site characterization. The IAEA recommends that site characterization for radioactive waste disposal should be performed through stepwise processes, in which the site characterization period is divided into preliminary and detailed stages, in sequence. This methodology was followed by several foreign countries for their geological disposal programs. General properties related to geological environments were obtained at the preliminary site characterization stage; more detailed site characteristics were investigated during the detailed site characterization stage. The results of investigation of geology, hydro-geology, geochemistry, rock mechanics, solute transport and thermal properties at a site have to be combined and constructed in the form of a site descriptive model. Based on this site descriptive model, the site characteristics can be evaluated to assess suitability of site for radioactive waste disposal. According to foreign site characterization cases, 7 or 8 years are expected to be needed for site characterization; however, the time required may increase if the no proper national strategy is provided.

The biological effects of fibronectin typeIII 7-10 to MC3T3-E1 osteoblast (Fibronectin type III 7-10 이 조골세포에 미치는 영향)

  • Hong, Jeong-Ug;Choi, Sang-Mook;Han, Soo-Boo;Chung, Chong-Pyoung;Rhyu, In-Chul;Lee, Yong-Moo;Ku, Young
    • Journal of Periodontal and Implant Science
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    • v.32 no.1
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    • pp.143-160
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    • 2002
  • 타이태늄은 뛰어난 생체적합성과 적절한 물리적 성질을 바탕으로 치과 및 정형외과 영역의 매식재로 널리사용되어져 왔으며, 골과 매식재 사이의 골 융합 정도를 증가시킬 목적으로 물리, 화학적인 방법을 이용한 타이태늄의 표면처리에 관한 많은 연구들이 진행되어 왔다. 최근에는 부착단백질 또는 성장인자를 이용한 생체재료의 표면개질을 통하여 조직적합성 및 치유 능의 개선을 위한 시도들이 있어왔다. Fibronectin(FN)은 주요 세포외기질중의 하나로 생체 내 널리 분포하여 세포의 부착, 이동 및 증식에 관여하는 거대 당단백으로, RGD및 PHSRN 펩타이드 서열이 세포의 인테그린과 결합하여 세포의 활성을 조절하는 것으로 알려져 있다. 이 연구에서는 FN으로 처리된 타이태늄이 조골세포의 부착, 증식 및 분화에 미치는 영향과 이에 따른 석회화 정도에 미치는 영향을 관찰하여 부착분자를 이용한 타이태늄 표면개질의 효과를 규명하고자 하였다. 상업용 순수 타이태늄을 gold thiol법을 이용하여 표면처리 후, 혈장 FN(plasma FN, pFN)과 유전자재조합법을 이용하여 얻은 FN조각(FN type III 7-10, FNIII 7-10)을 피복한 시편을 실험군으로, 아무런 처리를 하지 않은것(smooth surface, SS)과 산 부식(Sandblasted and acid etched, SLA)처리된것을 대조군으로 이용하였다. 배양된 조골세포주(MC3T3-E1)를 사용하여 타이태늄 표면 처리에 따른 세포의 증식, 형태변화, 알칼리성 인산분해효소(ALPase) 생산 및 세포면역형광법을 이용한 분화정도를 시간 경과에 따라 관찰하였다. 조골세포증식의 경우 FNIII 7-10 처리군에서 pFN 처리군 및 대조군에 비해 시간경과에 따라 유의성있는 세포수의 증식이 관찰되었으며(p<0.05), ALPase 생성의 경우에도 FNIII 7-10 처리 군에서 아무 처리도 하지 않은 군에 비해 유의성 있게 높은 효소의 생성이 관찰되었다(p<0.05). 주사전자현미경을 이용한 세포의 형태관찰결과 아무 처리도 하지 않은 군에서는 마름모형태를 나타내었으며, 산 부식 처리된 군에서는 세포가 가시모양의 형태를 보인 반면 FN으로 처리된 두 군에서는 세포의 부착 및 펴짐이 매우 발달되어 있는 모습이 관찰되었다. 세포의 분화정도를 관찰하기 위하여 국소부착키나제(focal adhesion kinase, FAK), 및 actin stress fiber의 분포양상을 세포면역형광법을 이용하여 관찰한 결과 FN으로 표면처리된 두 군에서 아무런 처리도 하지않은 군 및 산 부식처리 한 군에 비해 프라크의 발현이 높게 나타났으며 잘 발달된 actin stress fiber의 소견을 나타내었다. 이 실험의 결과들은 gold thiol 법을 이용한 표면처리 후 FN부착을 통한 타이태늄의 표면개질이 조골세포의 부착, 증식 및 분화에 중요한 역할을 담당하여 석회화 정도를 촉진시키는 것을 보여주었으며, 이런 결과들은 더 짧은 FN조각을 이용한 다른 생체재료의 표면개질에 폭 넓게 응용할 수 있으리라 생각된다.