• Journal of the Korean Ceramic Society
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• v.34 no.9
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• pp.949-956
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• 1997

With the increase of ZnO content, burnability of raw materials was improved and the formation of clinker minerals was accellerated. When ZnO was added 1wt%, the clinkering temperature was decreased about 30~5$0^{\circ}C$. As an increase of ZnO added, aluminate phase was decreased and ferrite phase was increased. When ZnO was added more than 3.0wt.%, the new phases, such as ZnO.Al2O3 and ZnO.Fe2O3 were formed. In the excess of amount of ZnO added, the decomposition of alite phase was intensed and the lamella structure in belite could not be observed due to the decomposition.

• Economic and Environmental Geology
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• v.32 no.4
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• pp.373-378
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• 1999

An investigation was conducted to find out formation and is mechanism of kaolinite from pyrophyllite under hydrothermal conditions. First, a pyropyllite sample from the Heenam district, Korea, was activated by heat-treating at $400^{\circ}C$ for 3 hrs. The kaolinite powder was successfully obtained by subjecting the dried feedstock to autoclaving at $200^{\circ}C$, 15atm, pH<1 for 5days with addition of 17.4mol/l $AlCl_3$. Evidently, the $AlCl_3$ addition as a mineralizer strongly promoted incorporation of $Al^{3+}$ ion into pyrophyllite structure which was subdequently converted into kaolinite. It also indicated that the formation of octahedral feed solution. The final pH of the solution was decreased to ~0.3. The transformation reaction was not noticeably accelerated when 10wt% natural kaolinite was added as the seeds, suggesting that the transformation was not reconstructional, but substitutional type.

• Korean Journal of Crystallography
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• v.11 no.1
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• pp.52-57
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• 2000

Hydrothermal synthesis of find CeO₂ powder has been investigated. Synthesis was performed with Ce(NO₃)₃·6H₂O, in ethanol and water solution. Mineralizer were NH₄OH and KOH and reaction for the powder synthesis has performed at 130℃. The morphology of CeO₂ was nearly spherical in using NH₄OH and cubic form in KOH. Particle size increased with addition of NH₄OH. Ethanol solution was effective to reduced the agglomeration.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1417-1422
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• 1994

Effect of MgO, CaSO4, and CaF2 addition on the formation of clinker minerals in portland cement have been investigated by measuring the amounts of free-CaO and C3S in the fired specimens and analyzing the Mg and S concentration in C3S and C2S. It was found that CaSO4 inhibited C3S formation but MgO addition offset this effect of CaSO4. MgO addition also enhanced the mineralizing effect of CaSO4+CaF2, resulting in the acceleration of C3S formation. It was suggested that Mg might inhibit the formation of sulphate compounds rim around C2S and thus C2S+CaOlongrightarrowC3S reaction was facilitated.

• Journal of the Korean Ceramic Society
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• v.23 no.2
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• pp.50-54
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• 1986

Effects of additionof $NH_4Cl$, NaBr and LiF on the formation of Zircon and the synthesis of CdS-Se red stain were investigated by means of XRD, DTA and the color standard and color nomenclature. The red stain of CdS-Se system shows a little difference dependent on firing temperature on firing conditon. Consequently it forms a good soid-solution with red color under the ratio of CdS and Se 3.5 -4.1 at 58$0^{\circ}C$. But it changes to dark red as increasing Se. LiF is the most effective in mineralizer to preparae zircon with the equilbrant molar $SiO_2$ and ZrO Zircon makes a good preparation in 0.33 mole LiF from 90$0^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.31 no.6
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• pp.617-622
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• 1994

Single crystals of misfit layered (LaS)xVS2(x 1.18) were grown using LaCl3(or I2) as a mineralizer (or transport agent) for the single crystal X-ray diffraction analysis. Procession photographs of (LaS)xVS2(x 1.18) were analyzed as the stacking structure of two kinds of LaS-and VS2-subcell. The result shows that two sublattices have common periodicities along the a*-and c*-axes, respectively, but not along the b*-axis. Sublattice dimensions of LaS and VS2 layers along b-axis were 5.67$\AA$ and 3.42$\AA$, respectively. Their ratio was 1.657 which is very close to 5/3.

• Journal of the Korean Ceramic Society
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• v.35 no.5
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• pp.465-471
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• 1998

Lead titanate(PT) and lead magnesium niobate(PMN) ceramic powders were prepared by microwave hy-drothermal method using teflon bomb. Raw materials were Pb(NO3)2 and TiO2 for lead titanate and Pb(NO3)2 Nb2O5 and Mg(NO)3.6H2O for PMN with NaOH as mineralizer in both cases. in lead titanate synthsis rate of microwave hydrothermal method was faster three times than one f conventional hydrothermal methods In lead magnesium niobate synthsis the mixture of perovskite and pyrochlore phases was obtained by single step technique and the PMN was not obtained by double step technique due to low temperature limitation of teflon bomb.

• Journal of the Korean Ceramic Society
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• v.37 no.8
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• pp.745-750
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• 2000

YAG:Tb3+ as green phosphor were studied for the development of low voltage FED phosphor prepared by hydrothermal synthesis. We changed the concentration of luminescence center ion Tb3+ in hydrothermal reaction of which conditions were at 8M NH4OH as mineralizer, at 35$0^{\circ}C$ for 12hrs. As results, we could finally get the YAG:Tb3+ (Y3-xTbxAl5O12) powder of which particle size was about 0.2~1.0${\mu}{\textrm}{m}$. The excitation spectra and the green emitted spectra of YAG:Tb3+ phosphor powder were observed. When we doped 0.25 mol Tb to YAG, we could observe the maximum cathodoluminescence from YAG:Tb3+ phosphor and the chromaticity coordinate of the phosphor was shown x=0.35, y=0.56 in CIE1931 diagram.

• Journal of the Korean Ceramic Society
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• v.11 no.3
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• pp.33-38
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• 1974

The possibility of the sources for the manufacture of mullite-rich refractories from the modified domestic alunite was studied. The modifying method of alunite studied were performed by calcination, wet ballmilling, and washing with water. For synthesis of mullite-rich refractories, the modified alunite with the addition of alumina and Fe2O3 as mineralizer was fired at 1350$^{\circ}$-155$0^{\circ}C$, and the following results were obtained: 1) The suitable firing temperature range was 1450$^{\circ}$-150$0^{\circ}C$, and adequate amounts of Al2O3 and Fe2O3 were below 30% and 3~4%, respectively. 2) Thermal expansion coefficient proportional to heating temperature was about 5$\times$10-6~10$\times$10-6cm/cm.deg. 3) The mineralogical compositions of the sintered specimens were found as mainly mullite and corundum.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.654-660
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• 1998

In preparing PSZT powder by hydrothermal synthesis, effects of reaction temperature, concentration of raw materials and mineralizer on crystallinity, particle size distribution, and dielectric constant were investigated. By varying the concentration of mineralizer and the ratio of Pb to Sr or Zr to Ti, crystalline PSZT powder, having the mean particle size of $0.3{\sim}15{\mu}m$, was prepared by hydrothermal synthesis in the temperature range of $120{\sim}200^{\circ}C$ for a 2h reaction. PSZT ceramics, having dielectric constant of 1000~3000, were prepared at $1150^{\circ}C$ for a 2h sintering reaction of the PSZT powders. Experimental results showed that the weight mean particle size of $0.5{\mu}m$ was obtained when the concentration of KOH in the solution was 10 wt % and the ratio of Pb to Sr was 0.95/0.05, that of Zr to Ti was 0.52/0.48. It also showed that the ceramics of dielectric constant of 2900 were prepared through sintering of this PSZT powder. Size of PSZT particles became smaller with its narrow distribution as the concentration of KOH increased up to 10 wt %. However, it came to be larger at this concentration and above. By adding small amount of Sr that would not affect that crystallinity of particles we can improve dielectric property of sintered materials. Addition of Zr may shift the major crystal phase of synthetic PSZT powder from tetragonal to rhombohedral phase.