• Journal of the Korean Ceramic Society
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• v.29 no.9
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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.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.3
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• pp.291-298
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• 1995

Abstract The growth and dissolution behaviour of reaction phase was studied during dissolution reaction between sintered alumina and $CaMgSiO_4$ at $1600^{\circ}C$ for various times. The formation of $CaO{\cdot}6Al_2O_3$ an intermediate reaction phase, and $CaMgSiO_4$ spinel, the final reaction product were observed during dissolution reaction of alumina into $CaMgSiO_4$ liquid phase. The growth and dissolution shape of $CaO{\cdot}6Al_2O_3$, an intermediate phase, was quite different.

• Journal of Korea Foundry Society
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• v.26 no.3
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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.

• Journal of the Korean Ceramic Society
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• v.30 no.6
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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.

• Journal of the Korean Ceramic Society
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• v.30 no.4
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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.

• Resources Recycling
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• v.20 no.4
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• pp.58-64
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• 2011

Recovery of novel metals such as Au, Ag and Ni from wastes PCB was investigated by slag treatments. The CaO-$Al_2O_3$(-$SiO_2$) and CaO-$SiO_2$-$CaF_2$ slags were employed in the present study. The PCB/Cu ratio is recommended to be lower than unity. The use of CaO-$SiO_2$-$CaF_2$ slag provided the more higher yield of Au, Ag and Ni than the CaO-$Al_2O_3$(-$SiO_2$) slag did, which was mainly due to the lower melting point and the viscosity of $CaF_2$-containing slag. The terminal descending velocity of metal droplets in the slag phase increased with decreasing slag viscosity.

• Korean Journal of Materials Research
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• v.13 no.9
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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.

• Journal of the Korean Ceramic Society
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• v.31 no.5
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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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4185-4190
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• 2013

We executed the property changes of the sintered MgO (99.9% purity, 300nm size) specimens with addition to CaO content of 0.00wt%, 0.25wt%, and 0.50wt%, processed at 7GPa, for 5min, 600~$800^{\circ}C$. To investigate the micro-structure and physical property changes of the sintered MgO(-CaO), we employed a scanning electron microscopy(SEM), X-ray diffractomerty(XRD), Vickers hardness, and density. The SEM result showed that MgO powder of 300nm size was changed into sintered structure of 520nm by high pressure and low temperature sintering, regardless of the CaO contents. According to the XRD analysis, no CaO phase observed, while MgO peaks shift indicated the existence of CaO in the MgO matrix. The Vickers hardness result showed that hardness of sintered MgO-CaO increased by 12% compared pure MgO under the same temperature conditions. It implied that we can obtain the same hardness with $100^{\circ}C$ lowered sintering temperatures by addition of CaO. The density results showed that it was possible to obtain density of 98%, which is 5% greater than that of pure MgO at low temperature of $600^{\circ}C$.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.812-825
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• 2019

Two dolomite samples mined from the different mines were calcined using a batch-type microwave kiln ($950/60min^{\circ}C$) to produce $CaO{\cdot}MgO$. The hydration of the $CaO{\cdot}MgO$ samples shows different reactivity. MgO was separated by reacting with a strong acid cation exchange resin using the reactivity of the hydration properties of light dolomite ($CaO{\cdot}MgO$). Calcium ($Ca-(R-SO_3)_2$) was separated from the prepared $CaO{\cdot}MgO$ by the cation exchange resin ($CaO{\cdot}MgO:R-SO_3H=1:12mass%$). High purity MgO (higher than 94 mass %) with unburned $CaCO_3$ (1~2 mass %) was obtained by the separation process. The separated MgO was heated at $950^{\circ}C$ for 60 minutes to afford high purity MgO with MgO content higher than 96%. And High-grade $CaCO_3$ was prepared from the reaction with calcium adsorbed resin ($Ca-(R-SO_3)_2$) and NaOH, $CO_2$ gas.