• 한국건설순환자원학회지
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• 제10권1호
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• pp.33-38
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• 2015

• 한국전기전자재료학회논문지
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• 제16권4호
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• pp.343-350
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• 2003

Using Bi$_2$Sr$_2$Ca$_2$.$_2$Cu$_3$ $O_{x}$ powders prepared by solid state reaction and spray drying method, the nucleation and growth behaviors of superconducting and second phases were investigated during isothermal heat treatment. When the spray drying power was used in contrast with solid state reaction powder, Bi$_2$Sr$_2$Ca$_2$.$_2$Cu$_3$ $O_{x}$ (2223) phase could be formed at the relatively shot time and second phases were much bigger. Quantitative analysis showed that as the heat treatment time increased, more Bi$_2$Sr$_2$Ca$_2$.$_2$Cu$_3$ $O_{x}$ (2212) changed to 2223 and the major second phase was changed from (Sr,Ca)$_{14}$Cu$_{24}$ $O_{x}$(14:24) to (Sr,Ca)$_2$Cu$_1$ $O_{x}$ (2:l). The superconducting phase formed at the relatively short time 14:24 phase. Following the Bi-free phase of 14:24 Phase, but long time was needed in places far from the 14:24 phase. Following the formation of the 2212 phase near the 14:24 phase, the 2223 phase nucleated preferentially at the interface between the 2212 and 14:24 phases. The preferential nuclcation of 2223 was explained by its structural similarity and low Interfacial energy with both the Bi-free and 2212 Phases.12 Phases.

• 한국초전도ㆍ저온공학회논문지
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• 제1권1호
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• pp.7-14
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• 1999

Wekk oriented $Bi_{2} Sr_{2} CaCu_{2} O_{8}$ suppercondcting thick films were fabricared on copper tape by LiReac-PreCu (liquid reaction between a Cu-free precousor and Cu tape) method. Cu-free precursor power which is composed of $Bi_{2}Sr_{2}Ca_{5}$ was printed on a copper tape by screen printing and was heat-treated. The speciment were partially in a molten state at the heat treatment temperature (85$0^{\circ}C$~87$0^{\circ}C$). The heat heat treatments for the reaction were performed in air or low oxygen pressure in several stages. XRD analyses of the resulting Bi2Sr2CaCu2O8 superconducting tapes show that the $Bi_{2} Sr_{2} CaCu_{2} O_{8}$ phase is dominant and a small amount of $Bi_{2} Sr_{2} Cu_{2} O_{6}$ phase is detected. Both phases are aligned in the c-axis direction.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
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• pp.22-25
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• 1999

A well oriented Bi-2212 superconductor thick films were fabricated by screen printing with a Cu-free Bi-Sr-Ca-Cu-O powder on a copper plate and heat-treating at 820- $880^{\circ}C$for several minute in low oxygen pressure or are. At minute in low oxygen pressure of air. At , the printing layer partially melted by reaction between the Cu-free precursor by reaction between the Cu-free$870^{\circ}C$ precursor and CuO of the oxidizing copper plate. It is believed that the solid phase is Bi : Sr : Ca : Cu = 2 : 2 : 0 : 1. It is likely that the Bi-2212 superconducting phase is formed at Bi-2212 superconducting phase is formed at Bi-free phase/liquid interface by nucleation and grows.

• 한국전기전자재료학회논문지
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• 제13권4호
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• pp.349-358
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• 2000

Fabrication and Characterization of Bi$_{2}$/Sr$_{2}$/CaCu$_{2}$/O$_{8}$(Bi2212) superconductor thick films were fabricated successfully on C tapes by liquid reaction between Cu-free precursors of Bi$_{x}$/SrCaO/$_{y}$(x=1.2-2) and Cu tapes. Cu-free Bi-Sr-Ca-O powder mixtures were screen-printed on Cu tapes and heat-treated at 850-87$0^{\circ}C$ for several minutes in air oxygen nitrogen and low oxygen pressure. In order to obtain the optimum heat-treatment condition we studied the effect of the precursor composition the printing thickness and the heat-treatment atmosphere on the superconducting properties of Bi2212 films and the reaction mechanism. Microstructures and phases of thick films were analyzed by films and the reaction mechanism. Microstructures and phases of thick films were analyzed by optical microscope and XRD. The electric properties of superonducting films were examined by the four probe method. At heat-treatment temperature the thick films were in a partially molten state by liquid reaction between CuO of the oxidized copper tape and the precursors which were printed on Cu tapes. During the heat-treatment procedure Bi2212 superconducting particle nucleate and grow in preferred orientations.ons.s.

• 한국건설순환자원학회논문집
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• 제9권4호
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• pp.443-450
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• 2021

순환유동층보일러 석탄회(CFBA)는 탈황공정을 위한 석회석 투입에 의한 탈황석고와 free-CaO에 의해 자기경화되는 특성이 있는 것으로 알려져 있다. 본 연구에서는 시멘트 바인더 대체용 CFBA의 자가경화에 대한 고로슬래그(BFS)와 탈황석고(FDG)의 영향을 검토하였다. 다량의 Fe₂O₃, free-CaO 및 탈황 석고를 함유하는 CFBA의 수화반응에 의한 압축강도는 칼슘알루미네이트 수화물, 칼슘실리케이트 수화물, 에트링자이트 및 칼슘카보페라이트 수화물(3CaO·Fe₂O₃·3CaCO₃·12H₂O)의 형성에 기인한다. CFBA의 자가 경화에 의한 압축강도는 Ordinary Portland Cement에서 C₄AF의 수화물과 유사한 수화물을 생성하여 표현하며, C₄AF의 수화시 CaSO₄가 존재하면 CaSO₄가 CaO·Al₂O₃와 에트링자이트를 형성하고, 유리 CaO와 CaCO₃가 함께 존재하면 육방정계 결정인 탄산칼슘 또는 탄산칼슘 결정이 형성됩니다. CFBA의 경화 특성은 C₄AF의 수화 및 경화 메커니즘에 의해 유사한 특성을 가짐을 확인하였다.

• 한국재료학회지
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• 제17권3호
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• pp.147-151
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• 2007

Cu-free multi-component sol, of which final oxide composition becomes $Bi_{1.9}Pb{0.35}SrCaO,\;Bi_{1.8}Pb_{0.2}SrCaO\;and\;Bi_{1.5}SrCaO$, respectively, was prepared through sol-gel route and coated on a bare Cu substrate. Starting materials were metal-alkoxides as follows.; [$Bi(OC_{2}H_{5})_{3}\;Pb(O^{1}C_{3}H_{7})_{2},\;Sr(O^{i}C_{3}H_{7})_{2},\;Ca(OC_{2}H_{5})_{2}$] as a reagent grade. Transparent light yellowish sol was obtained in the case of $Bi_{1.9}Pb_{0.35}SrCaO\;and\;Bi_{1.8}Pb_{0.2}SrCaO$ composition and $Bi_{1.5}SrCaO$ composition's sol was light greenish. Each sol was repeatedly dip-coated on Cu substrate four times and pre-heated at $400^{\circ}C$ and finally heat-treated in the range of $740{\sim}900^{\circ}C$. In the results, crystalline phases confirmed by XRD were (2201) orthorhombic and monoclinic phases. However, only $Bi_{1.9}Pb_{0.35}SrCaO_{x}$ composition showed pseudo-superconductive behavior after heat-treatment at $900^{\circ}C$ for 12 seconds and then onset temperature was 77 K, even though it did not exhibit zero resistance below Tc.

• 한국세라믹학회지
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• 제36권4호
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• pp.410-416
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• 1999

The reactivity of three kinds of spinels which CaO-Al2O3-SiO2 slag was investigated in terms of mineral phases and microstructures. New crystal products were not formed by reaction of 12CaO.7Al2O3 in the slag with spinels and free MgO components was preferenctially dissolved into slag for MgO-rich spinel and stoichiometric spinel. Meanwhile mineral phase was changed from 12CaO.7Al2O3 to CaO.Al2O3 to CaO.2Al2O3 finally to CaO.6Al2O3 having high melting point for Al2O3 -rich spinel. The Fe-oxide component of the slag was taken up by only stoichiometric spinel grains within the spinel clinker and the trapped amount of Fe-oxide was independent of MgO content of MgO in spinel clinker the more th resistance to slag corrosion but the less resistance to slag penetration.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.217-222
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• 2003

The steel slag, a by-product which is produced during the manufacture of steel by refining pig iron, is mainly used as road materials after aging it. It is necessary to age steel slag for long time in air because the reaction with water and free-CaO in steel slag could make the expansion of volume. This problem prevents steel slag from being used as aggregate for concrete. But steel slag used in this study was controled by an air-jet method which rapidly cools substance melted at a high temperature. Rapid cooling prevents from generation of free-CaO in steel slag. In this study, properties of steel slag manufactured by air-jet method and mortar used it were investigated. As results of this study, free-CaO contents were controled under 1%. Mortar used this steel slag demanded to lower water contents, higher compressive strength and lower drying shrinkage than the basic mortar in the same condition.

• 한국구조물진단유지관리공학회 논문집
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• 제22권5호
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• pp.119-126
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• 2018

최근 화력발전소에서는 순환유동층 연소방식의 발전소가 증가하는 추세이다. 순환유동층 보일러애시는 탈황 효과를 위해 석회석을 첨가함에 따라 애시 중에 포함되는 CaO, $SO_3$성분이 증가하여 일반적인 플라이애시 보다 free-CaO 함량이 높다. 또한 순환유동층 보일러애시는 기존의 플라이애시와 다르게 자기수경성 특성과, 높은 free-CaO함량에 의해 물과 만나면 높은 반응성을 갖는다. 본 연구는 순환유동층 보일러애시의 자기수경성 특성을 이용하여, 시멘트를 대체할 수 있는 비소성 결합재로써 활용 가능성에 대해 분석하였다. 순환유동층 보일러 애시의 함량에 따른 역학적 및 수화특성에 대해 검토하였다. 또한 석고의 종류 및 함유량에 따른 순환유동층 보일러애시 활용 비소성 결합재에 대한 압축강도 및 미세구조에 미치는 영향을 분석하였다.