• Journal of the Korean Ceramic Society
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• v.17 no.1
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• pp.20-26
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• 1980

The crystallization behaviors of slag-based glass in $CaO-MgO-Al_2O_3-SiO_2(-Na_2O)$ system have been studied. The mother glass containing 16.50 CaO, 7.50MgO, 19.70Al2O3, 50.80SiO3 and 2.09wt% $Na_2O$ was prepared by using Korean domestic raw materials such as granulated slag, serpentine, sea sand and etc. The glass-ceramics composed of major crystalline phase diopside was produced by the heat treatment in a temperature range from 850$^{\circ}$ to 9$25^{\circ}C$ for 0-6hr. The composition and morphology of diopside phase formed in the system were examined by X-ray diffraction analysis and electron microscopy. The kinetic measurements such as J.M. A plot and Arrhenius plot indicated that the process of nucleation of the initially formed diopside phase could be described from the view point of instantaneous nucleation. It was also demonstrated that the linear crystal growth of diopside phase was proceeded by short range diffusion of $Mg^{2+}$ and $Ca^{2+}$ ion. The microstructures of the resulting glass-ceramics were consisted of leafroidal shaped crystalline aggregations.

• Journal of Energy Engineering
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• v.20 no.3
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• pp.171-177
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• 2011

PVA/GLA/$Al_2O_3{\cdot}3SiO_2$ composite membranes were prepared through the reaction polyvinyl alcohol (PVA) with glutaraldehyde (GLA) as a cross-linking agent and subsequently adding aluminum silicate ($Al_2O_3{\cdot}3SiO_2$) as an inorganic material. The water uptake decreased as the GDL contents increased due to cross-linking process of PVA with GDL, and the ion conductivity increased as the $Al_2O_3{\cdot}3SiO_2$ contents increased in PVA/GLA/$Al_2O_3{\cdot}3SiO_2$ composite membranes. The cross-linking structure of the polymers was confirmed using IR and the tendency of water uptake. The thermal analysis of the copolymers was carried out by TGA. TGA results showed that PVA/GLA composite membrane were more heat-resistant than PVA due to the cross-linking of PVA, and the heat stability of the composite membranes improved much more as the concentration of $Al_2O_3{\cdot}3SiO_2$ increased. Membranes prepared in this study seem to be have thermal stability and increase a tendency of the cation conductivity up to $60^{\circ}C$, but to be exhibit lower performance tendency at over $90^{\circ}C$. Therefore, it is necessary to do more aggressive effort to explore the possibility of application as an ion-conductive composite electrolyte.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.551-554
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• 2000

The stability of $Pr_6$$O_{11}$-based ZnO varistors doped with $Y_2$$O_3$ was investigated under various d.c. stresses. The varistors were sintered at $1350^{\circ}C$ for 1h in the addition range of 0.0 to 4.0 mol% $Y_2$$O_3$. The varistors doped with $Y_2$$O_3$ exhibited much higher nonlinearity than that without $Y_2$$O_3$. In Particular, the varistors containing 0.5 mol% $Y_2$$O_3$ showed very excellent V-I characteristics, which the nonlinear exponent was 51.19 and the leakage current was 1.32 $\mu\textrm{A}$. And these varistors also showed an excellent stability, which the variation rate of the varistor voltage and the nonlinear exponent were -0.80% and -2.17%, respectively, under 4th d.c. stress, such as (0.80 $V_ {1mA}$/$90^{\circ}C$/12h)+(0.85 $V_{1mA}$/$115^{\circ}C$/12h)+(0.90 $V_{1mA}$/$120^{\circ}C$/12h)+(0.95 $V_{1mA}$/$125^{\circ}C$/12h). Consequently, since $Pr_ 6$$O_{11}$-based ZnO varistors doped with 0.5 mol% $Y_2$$O_3$ have an excellent stability as well as good nonlinearity, it is expected to be usefully used to develop the superior varistors in future.

• Journal of the Korean Ceramic Society
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• v.36 no.7
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• pp.734-741
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• 1999

Al2O3/t-ZrO2 particulate composites were prepared by sintering at 150$0^{\circ}C$ and 1$600^{\circ}C$ for 2h in air and microstructure and mechanical properties of the composites were investigated. Although most ZrO2 particles existed at Al2O3 grain boundaries a few ZrO2 particles within Al2O3 grains. Al2O3 grain growth was depressed due to the pinning effect by ZrO2 particles. During sintering coarsening of intergranular ZrO2 particles occurred as a results of the elimination of ZrO2 intraagglomerate grain boundaries and the coalescence of dragged ZrO2 particles by migrating Al2O3 grain boundries. Changes in mechanical properties of Al2O3 composites were dependant on microstructure of Al2O3 matrix and on size and structure of dispersed ZrO2.

• Journal of the Korean institute of surface engineering
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• v.49 no.1
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• pp.75-80
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• 2016

$In_2O_3$ nanowires were coated with $Co_3O_4$ nanoparticles to investigate the improvement of ethanol gas sensing performance compared with as-synthesized $In_2O_3$ nanowires. Scanning electron microscopy showed that the nanowires synthesized by VLS mechanism had diameters and lengths of approximately 50-100 nm and a few micrometers, respectively. $Co_3O_4$ nanoparticles produced by hydrothermal method was in the size range of a few to a few tens nm. As-synthesized and $Co_3O_4$ nanoparticles coated $In_2O_3$ nanowires sensors exhibited responses of 1.96% and 4.57%, respectively for the ethanol gas concentration of 200 ppm at $200^{\circ}C$. The underlying mechanism for the improved responses of $Co_3O_4$ nanoparticles coated $In_2O_3$ nanowires sensors is discussed.

• Journal of the Korean Ceramic Society
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• v.21 no.2
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• pp.121-126
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• 1984

The dielectric properties of $BaTiO_3$ containing 0~0.3mol% and ZnO respectively as additives were investigated as a function of temperature from $25^{\circ}C$ to 14$0^{\circ}C$ and frequency from 24 KHz to 15MHz. The density of sintered $BaTiO_3$ was increased with addition of increasing to 0.15mol% amounts of $Sb_2O_3$ and the dielectric constant was also increased. This is due to space charge polarization with Ba vacancies. Above 0.15mol% $Sb_2O_3$ the density was decreased and the dielectric constant was also decreased due to occuring the discharge through voids. The density of sintered $BaTiO_3$ was decreased with addition of increasing to 0.15mol% amounts of ZnO and the dielectric constant was decreased due to occuring the discharge through voids. Above 0.15mol% ZnO the density was increased and the dielectric constant was also increased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.7
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• pp.432-436
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• 2017

IZO transistors with $Al_2O_3$ as gate dielectrics have been investigated. To improve permittivity in an ambient dielectric layer, we grew $Al_2O_3$ by atomic layer deposition directly onto the substrates. Then, we prepared IZO semiconductor solutions with 0.1 M indium nitrate hydrate [$In(NO_3)_3{\cdot}xH_2O$] and 0.1 M zinc acetate dehydrate [$Zn(CH_3COO)_2{\cdot}2H_2O$] as precursor solutions; the IZO solution made with a molar ratio of 7:3 was then prepared. It has been found that these oxide transistors exhibit low operating voltage, good turn-on voltage, and an average field-effect mobility of $0.90cm^2/Vs$ in ambient conditions. Studies of low-voltage driving of IZO transistors with atomic layer-deposited high-k $Al_2O_3$ as gate dielectric provide data of relevance for the potential use of these materials and this technology in transparent display devices and displays.

• Journal of Korea Foundry Society
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• v.5 no.3
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• pp.19-26
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• 1985

This study has been carried out to examine into wettability of Cu-5%Sn alloy in $Al_2O_3$, MgO, $SiO_2$ and graphite, respectively and investigated into the change in macrostructure of Cu-5%Sn alloy according to kind and mixing rate of mold-coating. The results obtained from the experiment are summerized as follows; 1. Cu Cu-5%Sn alloy, wettabilities of $Al_2O_3$ and MgO were good, on the other hand, wettabilities of $SiO_2$ and graphite were bad. 2. The fine equiaxed zone was created because of the role of $Al_2O_3$ and MgO as preferential nucleation sites. 3. Notwithstanding change of mixing rate of $SiO_2$ in mold coating the equixed zone was not created. 4. The area of equiaxed zone was varied according to mixing rate in the case of using $Al_2O_3$ and MgO in mold-coating.

• Journal of the Korean Ceramic Society
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• v.31 no.9
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• pp.981-988
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• 1994

Crystallizable glasses with precipitation of celsian were prepared for the purpose of insulating dielectric layers for the devices such as integrated circuit substrates. Crystallization behavior of these glasses were studied by DTA, SEM, XRD analysis and by the measurement of dielectric properties. The base composition of the glass-ceramic consists in weight percent of 30% SiO2, 10% Al2O3, 26% BaO, 10% CaO, 10% ZnO, 8%TiO2 and 6% B2O3. 2-6 wt% Y2O3 were selected as the nucleating agent to promote monoclinic celsian formation. As a result, in barium-rich glasses containing 4~6wt% Y2O3 , monoclinic celsian was developed as major crystalline phase in the temperature range of 850~90$0^{\circ}C$. Also, the dielectric constant and quality factor of these glass-ceramics were about 9 and more than 1000, respectively.

• Journal of the Korean Ceramic Society
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• v.11 no.2
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• pp.3-10
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• 1974

For the manufacture of the silver-yellow glass, silver nitrate was used as a colorant in the base glass of $K_2O$-CaO-$SiO_2$ system. The latter in which the optimum condition was revealed showing beautiful yellow color had been selected among others after the preparatory studies to choose base glass. Other base glass systems considered were $Na_2O$-CaO-$SiO_2$, $R_2O$-PbO-$SiO_2$ and $R_2O$-PbO-BaO-$SiO_2$. The color developed on the specimen in various conditions was examined, using spectorphotometer, in term of the changes in absorbance with wavelength in the visible range. Experimental variables were the amount of the colorant and the additives, reheating temperature and time. The additives such as ZnO, BaO, $B_2O_3$ and $As_2O_3$ were added to increase the coloring action. It was observed that as the amount of silver increased in the base glass the absorbance around $410{\mu}m$ showed the increasing tendency, but the width of absorption curve was wider. Hence, the optimum amount of silver appeared to be 0.11~0.12%. It was found that ZnO was effective additive when present about 0.1%, while $As_2O_3$ ineffective rather retarding the coloration. Borax and $BaCO_3$ were proved effective when contained separately, but appeared ineffective when coexisted. Proper reheating temperature and time was ranged 550~$580^{\circ}C$ and 50~60 minutes. The higher the reheating temperature and the longer the reheating time, the absorbance was increased, while the width of absorption curve was wider. The colored glass prepared in the present experimental condition was found to have good water-resistance for the decorative purpose.