• Journal of the Mineralogical Society of Korea
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• v.15 no.1
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• pp.59-68
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• 2002

Chemical analyses and Rietveld structural refinement with powder X-ray diffraction data were done for Nb-rich perovskite, named latrappite ($Ca_2NbFe^{3+}O_6$)from the Oka, Quebec, Canada. Latrappite is shown to be a member of a continuous solid solution of $CaTiO_3-NaNbO_3-Ca_2NbFe^{3+}O_6$ and approximately $(Ca_{1.5}Na_{0.4})\;(Nb_{0.1}Ti_{0.6}Fe_{0.4})O_6$ in composition. The crystal structure of latrappite, determined by Rietveld refinement, is similar to that of perovskite ($CaTiO_3$). It differs in that replacement of Ti by Nb and $Fe^{3+}$ results in greater distortion and tilting of the $TiO_6$ framework octahedra relative to $CaTiO_3$. Revised unit-cell parameters of latrappite are a=5.4474(4), b=5.5264(4), c=7.7519(5) ${\AA},\;V=233.4(3){\AA}^3$ space group Pbnm.

• Journal of the Korean Magnetics Society
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• v.13 no.3
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• pp.121-126
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• 2003

The electromagnetic properties and microstructures of the basic composition of (N $i_{0.2}$C $u_{0.2}$Z $n_{0.6}$)$_{1.085}$(F $e_2$ $O_3$)$_{0.915}$ were invested by changing of the additive Sn $O_2$, CaO amounts and ferrite processes. There is no variation of grain size by changing additive amount. It can reduce the total loss when (N $i_{0.2}$C $u_{0.2}$Z $n_{0.6}$)$_{1.085}$(F $e_2$ $O_3$)$_{0.915}$ composition sintered at 1150 $^{\circ}C$ better than 130$0^{\circ}C$. Additive CaO confirmed of useful addition for the reduce total loss, because it increasing sintering density. Decreasing total loss were observed by adding both Sn $O_2$ 0.06 wt％ and CaO 0.4 wt％.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.5
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• pp.184-190
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• 2008

$CaMoO_4$ crystals with ellipsoid, peanut, dumbbell, and notched sphere shapes were synthesized using a simple precipitation reaction. The morphology of $CaMoO_4$ crystals evolved from ellipsoids, through peanut-like structures and dumbbells, to notched spheres with increasing the concentration of $Ca^{2+}$ and $MoO_4^{2-}$ ions. This morphology evolution of $CaMoO_4$ crystals is attributed to a fractal mechanism. Branched crystal growth started at both ends of the ellipsoids. The peanut-like and dumbbell morphologies were formed by the first and second fractal growths, respectively. Finally, the notched spheres were formed by further fractal growth of dumbbells.

• The Korean Journal of Ceramics
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• v.4 no.3
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• pp.204-206
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• 1998

The Gibbs free energy of formation of $BaThO_3$ from elemental oxides has been measured at temperatures between 853 and 903 K using a $CaF_2$ solid electrolyte galvanic cell. The galvanic cell consisted of Pt, $O_2, CaO+CaF_2 \parallel CaF_2 \parallelBaThO_3+ThO_2+BaF_2, O_2$, Pt EMF gave the standard Gibbs free energy for the reaction $CaF_2+BaThO_3=CaO+BaF_2+ThO_3$ as $\DeltaG^o$,/TEX>=124111.031-117.597 T(J/mol).

• Journal of Technologic Dentistry
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• v.21 no.1
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• pp.5-14
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• 1999

Glass ceramics for dental crown prosthesis were prepared by crystallization of CaO-MgO-SiO2-$P_2O_5-TiO_2$ glasses. Their crystallization behaviors have been investigated as a function of heattreatment temperature, holding time and chemical composition in relation to mechinical properties. Crystallization peak temperatures were determined by differential thermal analysis(DTA). Crystalline phases and mircostructures of heat-treated sample were determined by the means of powder X-ray diffraction(XRD) and scanning electron microscopy(SEM). The final crystalline phase assemblages and the microstructures of the samples were found to be dependent on glass compositions, heattreatment temperature, and holding time. 1st crystallization peak temperature(TP), affected strongly by apatite, was found to be increased or decreased. From the experiment, the following results were obtained : 1. The crystallization peak temperature($T_P$) formed by apatite increased until adding up to 9wt% $TiO_2$ to base glass composition, then decreased above that. 2. Apatite($Ca_{10}P_6O_{25}$), whitlockite(${\beta}-3CaO-P_2O_5$), $\beta$-wollastonite($CaSiO_3$), magnesium tianate($MaTiO_3$) and diopside(CaO-MgO-$2SiO_2$) crystal phase were precipitated in MgO-CaO-$SiO_2-TiO_2-P_2O_5$ glass system containing 9wt% and 11wt% of $TiO_2$ 3. Vickers hardness of samples increased with increasing heat-treatment temperature and Vickers hardness of S415T9 samples heat-treated at 1075 was approxi-mately 813Kg $mm^{-2}$ as maximum value. 4. Vickers hardness of samples increased due to precipitation of apatite, whitlockite, $\beta$-wollastonite, magnesium titanate, and diopside crystal phases within glass matrix.

• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.108.2-108
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• 2002

• Korean Journal of Materials Research
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• v.13 no.12
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• pp.785-790
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• 2003

We have synthesized some phosphors in the system $CaO-Y_2$$O_3$-$Al_2$$O_3$by combinatorial polymerized-complex method. Composition and synthetic temperature of phosphors in the library was screened from the emission intensities of individual samples under VUV excitation. In $Tb^{ 3＋}$-activated $CaO-Y_2$$O_3$-$Al_2$$O_3$, green phosphors showing good intensity were found to be X$O_3$$O_{7}$, CaYA1O$_4$, YA1O$_3$, $Y_3$$Al_{5}$$O_{12}$, $Y_4$$A1_2$$O_{9}$ .

• Journal of the Korean Ceramic Society
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• v.40 no.11
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• pp.1132-1137
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• 2003

For the application of environment conscious glass-fertilizer, dissolution characteristics of phosphate glass was investigated. In 0.1K₂O-0.1SiO₂-0.6P₂O/sub 5/ glass system, the compositions were designed according to variation of CaO & MgO contents, and glass formation region was confirmed. From the glass composition, the confirmed glasses were investigated to figure out thermal and dissolution properties. It was detected that glass transition & softening temperature of the glasses increased with increasing MgO contents. The dissolution properties of the glasses was affected by CaO and MgO content ratio.

• Nuclear Engineering and Technology
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• v.49 no.8
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• pp.1778-1782
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• 2017

The interaction of $NpO^+_2$ with $Cl^-$ was studied using visible-near-infrared spectroscopy in $NaCl-Ca-Cl_2-NaClO_4$, $NaCl-NaClO_4$, and $CaCl_2-NaClO_4$ solutions with ionic strength (I) of 6M. The spectra of $NpO^+_2$ around 980 nm varied with $Cl^-$ concentration in the $NaCl-CaCl_2-NaClO_4$ and $NaCl-NaClO_4$ solutions at [$Cl^-$] ${\geq}3.5M$, but not in the $CaCl_2-NaClO_4$ solution. Assuming the 1:1 interaction between $NpO^+_2$ and $Cl^-$, the apparent equilibrium constants at I = 6M were evaluated. The presence of $Ca^{2+}$ was found to destabilize overall interaction between $NpO^+_2$ and $Cl^-$. The observations were consistent with the density functional theory calculation.

• The Journal of Natural Sciences
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• v.8 no.2
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• pp.111-118
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• 1996

In order to improve the chemical durability of glass in the $Na_2O$-CaO-$SiO_2$ system, it was investigated in the effect of $B_2O_3$ and ZnO addition and changing amount of each composition, $Na_2O$, $Al_2O_3$, $Li_2O$. In this minimize the change of softening point of glass was as follow.(wt%)$B_2O_3$:3.36%, ZnO:2.88%, $Na_2O$:9.93%, $Al_2O_3$, $Li_2O$:0.19%, $SiO_2$:70.56%, CaO:11.22%, $K_2O$:0.14%