• 한국세라믹학회지
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• 제29권9호
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• pp.729-738
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• 1992

The glass formation and structural change with the glass compositions were investigated in the CaO-P2O5-SiO2 system with less than 40 wt% of P2O5. The glass formation range was determined by XRD, SEM and EDS techniques for water quenched specimens. The structural analyses were made for binary CaO-SiO2 glasses and ternary CaO-P2O5-SiO2 glasses by using FT-IR and Raman spectroscopy. The glass formation was affected by CaO/SiO2 mole ratio, P2O5 content and primary crystalline phase. The stable glass formation range was found when the transformed CaO/SiO2 mole ratio (new factor derived from structural changes) was in the range of 0.72~1.15 with less than 10 mol% of P2O5. The structural analyses of CaO-SiO2 glasses indicated that as the CaO/SiO2 ratio was increased, the nonbridging oxygens in the structural unit of the glasses were increased. With addition of P2O5 to CaO-SiO2 glasses, the P2O5 enhanced the polymerization of [SiO4] tetrahedra unit in CaO-SiO2 glasses, which contained a large portion of nonbridging oxygen. The phosphate eliminated nonbridging oxygens from silicate species, forcing polymerization of silicate structures and produced in [PO4] monomer in glasses. When added P2O5 was kept constant, the structural change with various CaO/SiO2 ratio was very similar to that of CaO-SiO2 glasses.

• 한국결정성장학회지
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• 제5권3호
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• pp.291-298
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• 1995

알루미나 고상소결체와 $CaMgSiO_4$간의 반응에 따른 반응상들의 성장 및 용해 거동을 $1600^{\circ}C$에서 열처리 시간을 변화하여 고찰하였다. 열처리시 알루미나는 $CaMgSiO_4$ 액상에 용융되어 중간에 반응상인 $CaO{\cdot}6Al_2O_3$와 최종 반응상인 $CaMgSiO_4$ 스피넬 형성이 관찰되었다. 중간상인$CaO{\cdot}6Al_2O_3$ 결정은 성장 모양과 용해 모양이 뚜렷하게 구분되었다.

• 한국주조공학회지
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• 제26권3호
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• pp.146-151
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• 2006

In this study, effects of CaD and Ca addtions on microstructure and ignition resistance of pure Mg were investigated. With increasing Ca and CaO contents, the grains in Ca and CaO added Mg were refined and ignition temperatures of CaO and Ca added Mg increased, too. As a result of phase analysis, CaO seemed to be reduced to Ca. $Mg_2Ca$ phase was formed even in 0.1 wt%CaO added pure Mg by reduction mechanism, while $Mg_2Ca$ phase was formed in over 1.35 wt% Ca added pure Mg. Thermodynamical consideration for the reduction mechanism of CaO in pure Mg was carried out.

• 한국세라믹학회지
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• 제30권6호
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• pp.433-440
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• 1993

The bioactivity of glasses in the CaO-SiO2 system and CaO-P2O5-SiO2 system with less than 10mol% of P2O5 was investigated by in vitro test in simulated body flood(SBF). The formation of Ca.P film and hydroxyapatite on the surface of glasses after in vitro test was analysed by X-ray photoelectron spectoscopy (XPS), fourier transform infrared reflection spectroscopy (FT-IRRS), energy dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM) observation. In the early stage of Ca.P film formation after in vitro test for CaO-SiO2 and CaO-P2O5-SiO2 glasses, the rate of Ca.P film formation on the surface of the glasses was dependent of structural parameter (Y) evaluated from the glass composition. First, in the case of the glasses having Y value below 2, Ca.P film and SiO2-rich layer were formed simultaneously, and there were no differences of the rate of Ca.P film formation in terms of the Y values. Second, in the case of the glasses having Y value above 2, the SiO2-rich layer was formed, and then Ca.P.Si mixed layer was formed in the silica gel structure of the SiO2-rich layer, and finally the Ca.P film on the surface of SiO2-rich layer. The rate of Ca.P film formation delayed as the Y values increased. The rate of hydroxyapatite formation of glasses (the rate of transformation from Ca.P film to hydroxyapatite) seems to be propotional to the rate of Ca.P film formation and Y value. The rate of hydroxyapatite formation of glasses belonging to the second group was delayed as structural parameter increased, and the hydroxyapatite crystal showed spherical growth in the early reaction stage, and then showed silkworm-like linear growth as the reaction time increased.

• 한국세라믹학회지
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• 제30권4호
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• pp.289-298
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• 1993

Properties in terms of the variation of the glass compositions, which were density (p), molar volume(Vm), atom/ion packing density (Dp), refractive index (nD), transformation temperature (Tg), dilatometric softening point (Td), thermal expansion coefficient (α), Young's modulus (E), and knoop hardness (KHN) were investigated in CaO-SiO2 glasses and CaO-P2O5-SiO2 glasses containing less than 10mole% of P2O5. Those properties were measured by density measurement kit, Abbe refractometer, dilatometer, ultrasonic pulse echo equipment, and micro hardness tester. When CaO content was increased in CaO-SiO2 glasses, p, Dp, nD, Tg, Td, α, E and KHN were increased, while Vm was decreased. When P2O5 was added to the CaO-SiO2 glasses with constant CaO/SiO2 ratio as 1.07, p, Dp, nD, Tg, Td, α, E and KHN were decreased, while Vm was increased. When the amount of P2O5 in glasses was kept constant, the changes of the properties with variation of CaO content in the CaO-P2O5-SiO2 glasses were very similar to those of CaO-SiO2 glasses. These phenomena could be explained by the structural role of P2O5 in the CaO-P2O5-SiO2 glasses, which was polymerization of siicate structures and resulted in [PO4] monomer structure in glasses. Due to this structural characteristics, the bond strength and packing density were changed with compositions. Proportional relationships between 1) np and Dp, 2) Tg, Td, α and CaO content, 3) E and Vm-1, and 4) KHN and P2O5 content were evaluated in this investigation.

• 자원리싸이클링
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• 제20권4호
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• pp.58-64
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• 2011

고온에서 PCB 처리를 통한 Au, Ag와 같은 귀금속뿐 아니라 Ni과 같은 주요 회유금속을 회수하기 위한 기초연구로서 CaO-$Al_2O_3$(-$SiO_2$) 및 CaO-$SiO_2$-$CaF_2$ 슬래그를 이용하여 Au, Ag, Ni의 회수거동올 관찰하였다. 슬래그 투입 없이 PCB만으로 용융실험을 수행한 결과 PCB는 거의 용융되지 않았으며, 이로부터 유도전류를 이용한 용융을 촉진할 뿐 아니라 유가금속의 회수를 위해서는 Cu와 갇은 적절한 base metal이 필요함을 확인하였다. 본 연구결과, PCB/Cu ratio는 1 이하가 바람직할 것으로 생각된다. CaO-$Al_2O_3$(-$SiO_2$) 및 CaO-$SiO_2$-$CaF_2$ 슬래그를 투입한 결과, $CaF_2$를 함유하는 fluorosilicate계 슬래그가 calcium aluminate계 슬래그보다 융점과 점도가 낮게 제어되었으며, 이로부터 Au, Ag, Ni의 높은 분배비를 얻을 수 있었다. 점도가 낮은 $CaF_2$ 함유 슬래그 적용 시 높은 유가금속 회수율은 슬래그 내에서 각 금속입자의 등속침강속도가 상승하기 때문인 것으로 평가되었다.

• 한국재료학회지
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• 제13권9호
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• pp.572-580
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• 2003

Synthesizing behavior and microstructural evolution of $CaZrO_3$and $m-ZrO_2$in a thermal reaction process of $ZrSiO_4$-$xCaCO_3$mixtures, where x is 7 and 19, were investigated to determine the addition amount of CaO in CaO:$ZrO_2$:$SiO_2$ternary composition. CaZrO$_3$-Ca$_2$SiO$_4$precursor prepared by the mixture of $ZrSiO_4$and CaCO$_3$in aqueous suspending media was controlled to the acidic (pH=4.0) condition with HCI solution to enhance the thermal reaction. The addition amount of dispersant into the $ZrSiO_4$-$xCaCO_3$slip increased with increasing mole ratio of $CaCO_3$, which was associated with the viscosity of slip. Decarbonation reaction was activated with an increase of the addition amount of $CaCO_3$, showing different final temperatures in $ZrSiO_4$-$7CaCO_3$and $ZrSiO_4$-$19CaCO_3$mixtures as about 980 and 116$0^{\circ}C$, respectively, for finishing decarbonation reaction. The grain morphology was changed to spherical shape for all samples with an increase of sintering temperature. The grain size and phase composition of the synthesized composites depended on the mixture ratio of Zrsi04 and CacO3 powders, indicating that the main crystals were m-ZrO2 ($\leq$3 $\mu\textrm{m}$) and $CaZrO_3$ ($\leq$ 7 $\mu\textrm{m}$) in $ZrSiO_4$$>-7CaCO_3$and $ZrSiO_4$-$19CaCO_3$mixtures, respectively.

• 한국세라믹학회지
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• 제31권5호
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• pp.505-512
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• 1994

It has been reported that a biocement obtained by mixing CaO-SiO2-P2O5 glass powder and ammonium phosphate solution has biocompatibility as well as high strength. However, the compositional dependence on its hardening and hydroxyapatite formation phenomena has not been studied. Therefore, the main objective of this work is to study the effects of P2O5, MgO in CaO-SiO2 system glass on the hardening and hydroxyapatite formation. When more than 50 mole% of CaO containing CaO-SiO2 glasses was reacted with ammonium phosphate solution, CaNH4PO4.H2O crystal was formed, but the glass with less than 50 mol% of CaO formed (NH4)2HPO4 and NH4H2PO4 crystals which are derived from ammonium phosphate solution without reacting with the glasses. As the amount of P2O5 in CaO-SiO2-P2O5 glass system was increased, the formation of CaNH4PO4.H2O crystal was enhanced. When those hardened samples were reacted with tris-buffer solution, hydroxyapatite was obtained only for the sample with CaNH4PO4.H2O. While the substitution of MgO for CaO decreased the formation of CaNH4PO4.H2O crystal. MgNH4PO4.H2O crystla was formed in high MgO containing glass, which did not react with tris-buffer solution.

• 한국산학기술학회논문지
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• 제14권9호
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• pp.4185-4190
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• 2013

본 연구에서는 불순물 첨가에 따른 MgO의 소결에 대한 물성변화를 확인하고자 99.9%순도, 300nm크기의 MgO 파우더에 고순도의 CaO를 0wt%, 0.25wt%, 0.50wt% 첨가하여 7GPa의 초고압 하에서 각각 $600^{\circ}C$~$800^{\circ}C$로 5분간 소결을 진행하였다. MgO(-CaO) 소결체의 미세구조와 기계적 물성 변화 확인을 위해 scanning electron microscopy(SEM), X-ray diffractometry(XRD), Vickers 경도, 밀도 측정을 진행하였다. SEM 분석 결과 처리전 300nm 의 MgO 응집체는 $800^{\circ}C$ 고압소결 후 CaO첨가와 관련 없이 모두 약 520nm 입도의 소결체가 되었다. XRD 분석결과 CaO상 자체는 확인할 수 없었으나 CaO고용에 따른 MgO 피크의 쉬프트에 의해 CaO의 존재를 확인할 수 있었다. 비커스 경도치 확인결과 CaO를 첨가하지 않은 MgO 소결체에 비해 동일 온도조건에서 약 12% 증가하였으며 비슷한 경도치를 얻기 위해 소결온도를 약 $100^{\circ}C$이상 낮출 수 있었음을 확인할 수 있었다. 밀도 측정결과 $600^{\circ}C$의 낮은 온도조건 하에서도 CaO를 첨가하지 않은 MgO 소결체에 비해 약 5%이상 증가한 98%이상의 효과적인 소결밀도를 얻을 수 있었다.

• Korean Chemical Engineering Research
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• 제57권6호
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• pp.812-825
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• 2019

국내에서 채광되는 백운석(dolomite, $CaMg(CO_3)_2$)을 회분식 형태의 마이크로웨이브 소성로($950^{\circ}C/60min$)에 의해 소성하여 경소백운석($CaO{\cdot}MgO$)을 제조하였다. 국내에서 산출된 두 개의 백운석 시료를 대상으로 경소백운석($CaO{\cdot}MgO$) 제조 후 수화 특성을 규명한 결과 반응성이 다름을 규명하였다. 경소백운석($CaO{\cdot}MgO$)의 수화 특성의 반응성을 이용하여 강산성 양이온 교환수지와 반응 시켜서 MgO를 분리하는 조건을 실시하였다. 분리 실험 조건은 경소백운석($CaO{\cdot}MgO$)과 $R-SO_3H$ (1:12 mass %)로 칼슘이온 흡착($Ca-(R-SO_3)_2$)하여 MgO를 분리하였다. 분리 후 MgO의 함량은 94 mass % 이상으로 분리되었다. 분리된 MgO를 $950^{\circ}C$, 60 min 동안 열처리 후 MgO의 순도는 96 mass %로 나타났다. 그리고칼슘 이온이 흡착된강산성 양이온교환수지($Ca-(R-SO_3)_2$)와 NaOH, $CO_2$ gas 반응에 의해서 98 mass %의 $CaCO_3$를 합성하였다.