• Journal of the Korean Crystal Growth and Crystal Technology
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• v.2 no.2
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• pp.20-32
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• 1992

$Na_2O-CaO-MgO-Al_2O_3-SiO_2$ glass was taken as a basic glass and then $Li_2O$ O.5wt%, $K_2O$ 2.0wt% were substituted to $Na_2O$content, MgO 12.0wt %, ZnO 6.0wt % to CaO content. And also nucleation agent $ZrO_2 and $CaF_2$ were added to 1-2wt% respectively. The crystal according to the compositions appeared wollastonite, diopside and diopside.tremolite. The glasses substituted NazO by LizO was decreased thermal expansion coeffcient but substituted by ZnO was opposite direction and both of them increased bending strength. In the ratio of ZrOz to CaF, each 1: 1 and 1: 2 have shown considerable crystal growth at $1000^{circ}C~1050^{\circ}C$ and high bending strength, but the glass in the ratio 1: 2 have shown lowest thermal expansion coefficient. The activation energy was at the glass in the ratio of ZrO, to CaFz 1:2 evaluated 55.24kvsl/mol by Ozawa type and 53.05kal/mol by kissinger type.

• 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.399-402
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• 2000

For improvement of B constant in $CaMnO_3$-$CaTiO_3$ perovskite type thermistors, effect of $Cr_2$$O_3$ addition ranged from 0.0wt% to 5.0wt% on electrical properties were investigated with contents and sintering temperatures in the view of crystal and microstructures. The solubility limit of Cr$_2$O$_3$was up to 0.5wt% judging from the result of lattice parameter. The grain size was decreased and the resistance at room temperature and B constant were increased with the addition of $Cr_2$$O_3$.On particular, B constant of$CaMnO_{3-x}$$Cr_2$$O_3$ system was increased greatly from 1574k to 2598k at 0.5wt% $Cr_2$$O_3$addition. Further addition of $Cr_2$$O_3$, however, resulted in the decrease of the resistance and B constant due to the $Cr_2$$O_3$ precipitation on the grain boundary. As the$CaTiO_3$contents increased in the $CaMnO_3$-$CaTiO_3$ system, the resistance at room temperature and B constant were highly changed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.5
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• pp.397-404
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• 2009

Effects of ceramic filler types and dose on the low temperature sintering and dielectric properties of ceramic/$CaO-Al_2O_3-SiO_2$ (CAS) glass composites were investigated. All of the specimens were sintered at $850{\sim}900^{\circ}C$ for 2 h, which conditions are required by the low-temperature co-firing ceramic (LTCC) technology. Ceramic fillers of $CaCO_3$, $Al_2O_3$, $CaCO_3-Al_2O_3$ mixture, and $CaCO_3-Al_2O_3$ compound ($CaAl_2O_4$), respectively, were used. The addition of $Al_2O_3$ yielded the crystalline phase of alumina, which was associated with the inhibition of sintering, while, $CaCO_3$ resulted in no apparent crystalline phase but the swelling was significant. The additions of $CaCO_3-Al_2O_3$ mixture and $CaAl_2O_4$, respectively, yielded the crystalline phases of alumina and anorthite, and the sintering properties of both composites increased with the increase of filler addition and the sintering temperature. In addition, the $CaAl_2O_4$/CAS glass composite, sintered at $900^{\circ}C$, demonstrated good microwave dielectric properties. In overall, all the investigated fillers of 10 wt% addition, except $CaCO_3$, yielded reasonable sintering (relative density, over 93 %) and low dielectric constant (less than 5.5), demonstrating the feasibility of the investigated composites for the application of the LTCC substrate materials.

• Journal of the Korean Ceramic Society
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• v.29 no.5
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• pp.341-346
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• 1992

The effects of CaO addition on the low temperature degradation behavior of 2.5Y-TZP ceramics were investigated. Y2O3-CaO-ZrO2 ceramics were prepared from the commercial Y-TZP powder added within 1 mol% of CaO. Fully tetragonal phase could be obtained at each composition under sintering condition of 1500$^{\circ}C$ for 1 hour. As the amount of CaO increased, grain size was decreased. From the result of heat treatment at 200$^{\circ}C$, volume fraction of monoclinic phase formed on the surface of each specimen was decreased with higher CaO amount. Stability of tetragonal ZrO2 phase for low temperature heat treatment was increased by CaO addition without the degradation of mechanical properties.

• 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.33 no.5
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• pp.563-571
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• 1996

In order to fabricate solid electrolyte CaO-stabilized ZrO2 of high density sintered body economically 13 mol% CaO-stabilized ZrO2 powders were synthesized by the coprecipitation method. The characteristics and sintering behavior of fine powder were investigated. The precipitates has the specific surface area of 193 m2/g and apperaed to be fine and spherical primary particles with a size of approximately 5nm. The crystalliza-tion temperture of CaO-stabilized ZrO2 was 462$^{\circ}C$. The tetragonal phase was stable in the low calcining tempe-rature regions and the cubic zirconia solid solution was formed from above 120$0^{\circ}C$ through an intermediate stage of formation of CaZrO3 By introducing fine powders washed with alcohol and ball-milling process after calcination the sintered body was possible to attain the value of above 92% of the theoretical density at low temperature of 120$0^{\circ}C$.

• Journal of the Korea Organic Resources Recycling Association
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• v.29 no.4
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• pp.41-46
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• 2021

In order to investigate the degree of sewage sludge solubilizaion using ultrasonic(US) combined with calcium peroxide(CaO₂), VSS reduction rate, solubilization rate, SCOD/VSS ratio, SCOD increasing rate, LB-EPS(Loosely-Bound EPS) and TB-EPS(Tightly-bound EPS) were measured. US was compared as a control. Solubilization rate increased by 23.4% under US and increased by 50.7% under US/CaO₂(0.05 g CaO₂/g VSS). and also, at the same conditions, VSS reduction rate increased by 7.1% and 17.7%, respectively. SCOD increasing rate from 10 to 90 minutes was 0.0151 min^-1 under US/CaO₂(0.02 g CaO₂/g VSS). TB-EPS decreased by 36.4% under US and decreased by 59.0% under US/CaO₂(0.05 g CaO₂/g VSS). TB-EPS decreased during first 10 minutes and then decreased slowly until 90 minutes. There was no significant difference in TB-EPS decrease according to the dosage of calcium peroxide.

• Korean Journal of Materials Research
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• v.6 no.7
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• pp.684-691
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• 1996

To enhance the formation of Bi,Sr,Ca,Cu,O,(Bi-2223) single phase in a shorter reaction time, the intermediate compounds such as Bi,Sr,CuO,(Bi-2201). BizSr,CaCuz08(Bi-2212) and (Ca, Sr,, ,9)CuOz in the Bi-Sr-Ca-Cu-0 system were used as the precursors. The formation of Bi-2223 was enhanced in the mixture of Bi-2201 and (Ca, ,,Sr, 119)C~eOsZpe,c ially from the mixture with (Ca, 9I Sr, ,,)CuO,-rich composition compared to Bi, iPb, 4Sr2Ca,Cu3010-cxo mposition. The formation of Bi- 2223 essentially completed within 60h at 860$^{\circ}$C and 870$^{\circ}$C. However, a small amount of the remnant Bi-2212 phase did not disappear even after a prolonged reaction at 870'C. The merit of the proposed synthetic method using the intermediate precusors can be summarized as a shorter reaction time for the formation of Bi-2223 phase, in addition to a smaller amount of second phases compared to the conventional solid-state reaction method.

• Journal of the Korean Chemical Society
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• v.46 no.4
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• pp.336-345
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• 2002

In this study, we have screened $Eu^{3+}$- and $Tb^{3+}$-activated candidate phosphors for PDP in the sys-tems of CaO-Gd$_2$O$_3$-Al$_2$O$_3$ by combinatorial chemistry and investigated the synthetic temperature, optimum com-position and luminescent properties about the candidate phosphors. To construct the emission intensity library by VUV PL, we have synthesized 210 different compositional samples using a polymerized-complex method. Good luminescent samples were identified by X-ray diffraction method. $Ca_$\alpha$$G$d_{0.95-$\alpha$-$\beta$}Al_$\beta$O_$\delta$$ : Eu(0.02< $\alpha$+$\beta$ <0.04) phos-phors screened as a red phosphor have good color purity than commercial phosphor. In the candidate phosphors of CaGdAl$_3O_7$ : Tb, Ca$Al_{12}O_{19}$ : Tb, Gd$_4$Al$_2O_9$ : Tb, and Gd$_3Al_5O_{12}$ : Tb CaGdAl$_3O_7$ : Tb, and Ca$Al_{12}O_{19}$ : Tb have shorter decay time than commercial phosphor.