• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.110-110
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• 2012

아라미드 섬유소재는 고강도, 고내열성의 소재로 다양한 용도전개가 가능하나, 일광 및 부식에 의한 내광성 및 내후성이 급격하게 저하되는 단점이 있다. 자외선의 광화학적 작용에 의해 변퇴, 경화, 취하, 강도저하가 일어나는 단점을 보완하기 위해 내광성 및 내화학성이 우수한 전이금속산화물 소재와의 복합화를 통해 내광성 및 내화학성 개선에 대하여 연구하였다. zinc acetate 수화물과 수산화리튬을 무수에탄올로 용해시킨 용액을 강하게 교반하여 나노 산화아연 졸을 제조하였다. 제조된 나노크기의 zinc oxide 입자의 형상과 입자분포 등 제조특성을 입도분석기, FE-SEM 및 EDS 분석을 통하여 고찰하였으며, 제조된 나노졸을 아라미드 섬유에 침지시켜 Xenon-arc 내후성시험기에서 80시간 동안 노출시켜 노출시간에 따른 물성변화를 분석하였다. 나노졸을 5~20% 픽업으로 패딩한 후 광에 노출된 아라미드의 인장강도는 나노졸을 처리하지 않은 아라미드 섬유보다 20~30% 개선된 인장강도를 나타내었다.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.473-474
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• 2010

This high pressure synchrotron X-ray diffraction study examined the change of bulk modulus of C-S-H(I), core material creating strength in alkali-activated slag cement as well as structural model of C-S-H, mainly attributed to Al-substitution for Si, which occurs at the bridging tetrahedral sites in dreierketten silicate chains in the nanostructure of C-S-H(I). This study presents that Al-substitution in C-S-H(I) does not affect the bulk modulus of C-S-H(I), which is surprising because many researchers have expected that Al-substitution should induce some critical change in mechanical properties of C-S-H(I).

• Journal of the Korean Ceramic Society
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• v.40 no.3
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• pp.234-240
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• 2003

Hardened cement pastes of OPC which contains 10 wt% CSA type expansive additives were immersed in aqueous solution of 10 wt% MgS $O_4$.7$H_2O$ and then investigated by compressive strength, XRD. SEM and DSC etc.. According to the results including the hydration products and the microstructure of the hardened paste, the case of CSA type expansive additives［No. 6(C/(equation omitted) : 2.29, A/(equation omitted) : 0.16)] prepared from raw materials increased the resistance to $Mg^{2＋}$, S $O_4$$^{2-}$ ion diffusion than that of OPC paste due to the densification by the formation of fine ettringite in the first stage and the hydrates according to $\beta$-C$_2$S hydration in the late period.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11b
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• pp.521-526
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• 1996

원자력 발전소 내의 1차계통수에 존재하는 부식생성물과 노심에서 방사화된 여러 핵종들의 종류와 그 양에 대해서 CRUDSIM/MIT모형을 이용해서 분석하였다. 고리 4호기의 차계통수내의 수화학 조건을 이용하여 CRUDSIM/MIT모형에 적용하고 그 결과를 냉각수의 Activity자료와 증기 발생기의 Activity자료와 서로 비교 분석하였고, 노심과 증기발생기의 Crud양과 Activity를 예상하였다. 이 모형의 주요 인자인 $\beta$$_{c}$와 $\beta$$_{a}$ 값을 증기발생기의 Activity측정자료에 의해서 구하였다. 그리고 발전소 운전 중에 증기 발생기와 냉각수의 Activity각 최소화 할 수 있는 최적 조건 범위도 냉각수의 온도, pH, 수소농도등을 변화시켜서 구하였다. 고리4호기에 이 모형을 적용할 때 입력 자료에서, Activation Factor와 Recoil Release 등의 인자와 증기 발생기의 방사선양과 핵연료 표면의 Crud양을 구할 수 있으면 더욱 정확한 결과 값들을 얻을 수 있다.

• Journal of Energy Engineering
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• v.28 no.1
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• pp.17-21
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• 2019

Calcium sulfaluminate (CSA) was synthesized to improve the shrinkage of OPC. In this study, the setting time, the compressive strength and the length change ratio were confirmed by replacing the synthesized CSA with OPC by 10% and 13% by 16%. In the case of shrinkage-reducing type cement, formation of Ca-Al-$H_2$-based hydrate was activated. Therefore, the setting time was shortened. The compressive strength of the shrinkage - reducing type cement is comparable to that of OPC after 7 days' strength. However, shrinkage reducing type cement showed improved initial strength compared to OPC. The length change ratio was found to be improved by drying shrinkage from -0.075% to -0.047% on the 28th day.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06b
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• pp.55-85
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• 1996

지르코니아 분말은 ZrO2 결정상이 온도변화에 따라 부피변화를 수반하는 상전이변태를 나타낸다. 단사정 ZrO2가 110$0^{\circ}C$에서는 정방정으로, 2$700^{\circ}C$ 내외에서는 입방정으로 결정구조가 가역적으로 변한다. 이 ZrO2에 금속산화물을 고용시키면 형석 (CaF2:Florite)형의 입방정 결정구조가 실온에서도 안정하게 존재하게 된다. 안정화제 산화물은 caO, MgO등 2가 산화물외에 3가 또는 4가의 금속산화물로서 Sc2O3, Y2O3, Sm2O3, Nd2O3, Gd2O3, Y2O3, CeO2 등이며 이들은 금속이온의 원자가가 변하기 쉬운 희토류 산화물이다. 안정화 지르코니아는 형석형 결정구조이며 결정화학적으로 보면 금속양이온이 산소이온에 대해서 정육면체형의 8배위를 하고 있다. 이때 이온반경비(양이온/음이온)에 따라 Zr+4자리와 O-2자리의 격자위치와 모양이 형성되므로 비틀어진 정육면체구조이건 이상적인 정육면체 형석구조를 이룬다. 이는 지르코니아의 결정상의 2상-3상인 부분안정화 지르코니아다결정체(PSZ : partially stabilized zirconia)이거나 단일상-2상인 정방정 지르코니아다결정체(TZP : tetragonal zirconia polycrystal)의 결정구조를 가지는데 기인한다. PSZ는 주로 MgO, CaO를 안정화제로 고용시켜 입방정 영역에서 소결하고 이를 다시 입방정과 정방정의 상 영역에서 열처리하여 입방정 입자내부에 정방정을 석출 형성시킨 것이며 TZP는 Y2O3 및 CeO2를 고용시켜 PSZ와 다르게 일반적인 상압소결한 정방정 결정상의 미립자이다. 산화지르코늄 분말은 지르콘사에서 열분해시킨 지르코늄소결.융해괴(caustic fusion clinker)를 산처리하여얻어진 지르코늄산용액(zirconyl acid solution : cloride, sulfide, nitride 등)으로부터 제조된다. 고순도 산화지르코늄은 용액 결정석출법에 의해 ZrOCl2.8H2O, 5ZrO2.3SO3.15H2O, ZrO(NO3)2.xH2O 등의 지르코늄 수화물만을 재결정화시킨 것으로부터 얻을 수 있으며 이 지르코늄염 수용액으로부터 입자미세구조를 효과적으로 제어하여 산화지르코늄 및 안정화 지르코니아 분말제조가 가능하다. 안정화 지르코니아 분말은 ZrO2와 안정화산화물의 고용을위하여 가열처리를 필요로 하며 일정온도에서 최적상태로 숙성하므로서 2가지 상(phase) 이상의 고용체를 가지게 된다. 안정화 지르코니아 분말은 고용처리온도를 낮추고 효과적으로 생성시키기 위해서는 지르코늄 및 안정화제염을 혼합하고 습식 직접합성하여 저온에서 고용체의 합해진상 영역을 생성시키는 것이다. 이는 지르코니아 원료분말의 미세구조를 제어하므로서 가능하며 이때 화학성분조성과 크기형태가 균일하게 분포된 입자분말을 얻을 수 있다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.6
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• pp.811-823
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• 2019

Slip form method is applied to many cases of a shaft these days because it is safer, more economical and faster than cast-in-place method. Slip-up height of the method is approximately 2.5 to 4.0 m/day. If the temperature of concrete is outside the range of 10 to 30℃, the effects of changes in strength or elastic characteristics are significant. Therefore, it is difficult for slip-up speed to be higher than 3 m/day during winter construction. In addition, concrete has heat caused by hydration, which causes temperature cracking of hardened concrete. Therefore, temperature control of concrete curing is necessary for the continuous slip-up of slip form. In this study, the rebound hardness, time of ultrasonic waves propagation, heat of hydration, and external temperature are measured by developing heating panels and test devices for the continuous slip-up. Based on this, heating slip form is manufactured; this was applied to "Kimpo sites" and "Sinwol sites". The compared slip-up speed samples were 1.9 m/day or 0.200 m/hr on average at Gimpo sites (08:00~17:30) and 2.0 m/day or 0.210 m/hr at Sinwol sites.

• Journal of the Korean Chemical Society
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• v.45 no.2
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• pp.116-120
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• 2001

In order to know the physicochemical properties of magnetized water, the experimental methods of column assay, crystalization of saltsand gypsom have been explored to elucidate the effects of magnetized water on the solubility speed of salts, crystal pattern from salt squeous solutions, and gypsom crystal pattern, respectively. In the column assay for salt solubility the magnetized water showed the decreased initial solubility speed of NaCl and slightly increased initial solubility spped of KCI, however, the maximum solugilities of NaCl and KCI in the magnetized aster were almost same in the double distilled water, respectively. The column assay also indicated that the magnetized water showed the decreased initial solubility speed of urea (CH$_4$N$_2$O), sodium citrate (HOC(CO$_2$Na)-(CH$_2$CO$_2$Na)$_2$-2H$_2$O) and (NH$_4$)$_2$compared to the double distilled water, while slightly increased solubility speed of glycine (NH$_2$CH$_2$COOH), boric acid (H$_3$BO$_3$), MgSO$_4$. Crystalization of 1% or 5% salt aqueous solutions by rapid evaporation disclosed that the magnetized water produced more condensed and bigger crystal structure than the control water. The pattern of gypsom crystal formation also indicated that the magntized water enhanced the crystal formation in the hydration reaction of gypsom plaster compared to the double distilled water. Taken together, it was presumed that the magnetized water showed the different physicochemical properties in the interaction with various salts, especially showed the contrast results between NaCl and KCI.

• Journal of the Korean Chemical Society
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• v.37 no.3
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• pp.302-308
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• 1993

Monolayers of calcium palmitate were deposited on a piezoelectric quartz crystal plate by the Langmuir-Blodgett(LB) technique, and it was found from frequency changes of the quartz crystal deposited LB films. The usual carbonyl absorbance at 1704 cm$^{-1}C$ was replaced by the split band in the 1540~1590 cm$^{-1}C$. The two absorptions at 1580 cm$^{-1}C$ and 1540 cm$^{-1}C$ were assigned to the antisymmetric stretching vibration of the calcium carboxylate group and the hydrated species due to the lowering carbonyl stretching frequency by hydrogen bonding$^1$ respectively. Besides, it was demonstrated by X-ray diffraction analysis. The swelling behaviour of LB films in water phase at 23$^{\circ}C$ was observed from the frequency change of the LB films deposited quartz crystal with time. Calcium palmitate LB films has been found to swell substantially in water without flaking, whereas hexadecanol LB films hardly swelled in water. Amount of swelling of calcium palmitate LB films was equivalent to 47 wt.${\%}$ of the dry LB films, which means that ca. 7 water molecules were incorporated per calcium palmitate amphiphile. Chemical structure of calcium palmitate LB film was estimated as [CH$_3$(CH$_2$)$_{14}$COO]$_2$Ca${\cdot}$XH$_2$O, and the hydration number was 1.

• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.369-375
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• 2014

This study examined the changes of microstructural compositions in cement matrix according to the depth from the surface of a reinforced concrete (RC) column exposed to fire. The RC column was exposed to a standard fire for 180 minutes. After the fire test, core samples passing through the column section were obtained. Using the core samples, the remaining fractions of calcium-silicate-hydrates (C-S-H) and calcium hydroxide in cement matrix at the surface, the depth of 40 mm and 80 mm and the center (175 mm) were examined using thermal gravimetric analysis (TGA) and X-ray diffraction analysis (XRDA). Using nuclear magnetic resonance (NMR) technique, the silicate polymerization of C-S-H in cement matrix was also evaluated. The experimental results indicated that the amount of C-S-H loss at the center of column experiencing the transferred fire temperature of $236^{\circ}C$ has been underestimated as the TGA results showed the highest C-S-H contents are located at the depth of 80 mm, where the transferred fire temperature is $419^{\circ}C$. Moreover, the destruction of silicate connections at the center was observed as similar as that at the depth of 40 mm, where the transferred fire temperature was $618^{\circ}C$. This might be attributed to the temperature changes during cooling time after the fire test was neglected. Due to the relatively low thermal conductivity of concrete, the high temperature, which can affect the change of microstructure in cements, will hold longer at the center of the column than other depth.