Go to the main menu
Skip to content
Go to bottom
REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of the Korean Ceramic Society
Journal Basic Information
Journal DOI :
The Korean Ceramic Society
Editor in Chief :
Volume & Issues
Volume 34, Issue 12 - Dec 1997
Volume 34, Issue 11 - Nov 1997
Volume 34, Issue 10 - Oct 1997
Volume 34, Issue 9 - Sep 1997
Volume 34, Issue 8 - Aug 1997
Volume 34, Issue 7 - Jul 1997
Volume 34, Issue 6 - Jun 1997
Volume 34, Issue 5 - May 1997
Volume 34, Issue 4 - Apr 1997
Volume 34, Issue 3 - Mar 1997
Volume 34, Issue 2 - Feb 1997
Volume 34, Issue 1 - Jan 1997
Volume 3, Issue 3 - 00 1997
Volume 3, Issue 2 - 00 1997
Volume 3, Issue 1 - 00 1997
Selecting the target year
Fabrication of SiC Converted Graphite by Chemical Vapor Reaction Method
Journal of the Korean Ceramic Society, volume 34, issue 12, 1997, Pages 1199~1204
SiC conversion layer was fabricated by the chemical vapor reaction between graphite substrate and silica powder. The CVR process was carried out in nitrogen atmosphere at 175
. From the reduction of silica powder with graphite substrate, the SiO vapor was created, infiltrated into the graphite substrate, then, the SiC conversion layer was formed from the vapor-solid reaction of SiO and graphite. In the XRD pattern of conversion layer, it was confirmed that 3C
-SiC phase was created at 175
. Also, in the back scattered image of cross-sectional conversion layer, it was found that the conversion layer was easily formed at 185
, the interface of graphite substrate and SiC layer was observed. It was though that the coke particle size and density of graphite substrate mainly affect the XRD pattern and microstructure of SiC conversion layer. In the oxidation test of 100
, the SiC converted graphites exhibited good oxidation resistance compared with the unconverted graphites.
Effect of Preparation Methods of a Matrix Retaining Electrolyte on the Characteristics of a Phosphoric Acid Fuel Cell
Journal of the Korean Ceramic Society, volume 34, issue 12, 1997, Pages 1205~1212
The matrices which consisted of SiC whisker, PES(polyesterasulfone) as a binder, span 80(sorbitan monooleate) as a surfactant, TPP(triphenyl phosphate) as a plasticizer and dichloromethane as a solvent, have been prepared by the various methods such as tape casting, rolling, tape cast-coating and roll-coating method. The fuel cells of single stack type using these matrices are characterized by ac impedance spectroscopy and cyclic voltammetry technique. A fuel cell using a matrix prepared by the tape cast-coating method shows the best performance of 466.34 mA/
at 0.6V because it has the lowest polarization resistance at the interface between electrodes and a matrix due to the largest three phase contact region of gases, catalyst and electrolyte.
Effects of Particle Size of Alumina on the Behaviors of Tape Casting and Sintering of Alumina-Talc System
Journal of the Korean Ceramic Society, volume 34, issue 12, 1997, Pages 1213~1220
Effect of particle size of alumina and amount of talc on tape casting and densification behaviors of alumina-talc system were investigated. The pseudoplastic behaviors of slurries increased with increase in amount of talc addition and decrease in alumina particle size. In case of using coarse alumina powder, densification of specimens were accelerated with increase of sintering temperature and amount of talc addition. On the contrary, fine alumina powder retarded of rearrangement of alumina particle during liquid phase sintering due to premature densification of alumina matrix region before formation of liquid phase and then densification of specimens were suppressed with increase of sintering temperature and amount of talc addition.
Effects of Sintering Atmosphere and Dopant Addition on the Densifcation of
Journal of the Korean Ceramic Society, volume 34, issue 12, 1997, Pages 1221~1226
The effects of sintering atmosphere and dopant addition on the behavior of densification and grain growth of SnO2 ceramics were investigated with consideration of defect chemistry. CoO and Nb2O5 were chosen as dopants, and oxygen and nitrogen were used for controlling of sintering atmospheres. With the decrease of oxygen partial pressure, densification was depressed due to evaporation of SnO2 ceramics. In the case of SnO2 sintering, the addition of CoO, which produced oxygen vacancy in SnO2 ceramics, led to acceleration of densification and grain growth. On the contrary, when Nb2O5 as a dopant producing Sn vacancy was added to SnO2 ceramics, densification and grain growth were simultaneously retarded. As results, it was conformed that diffusion of oxygen ions was rate determinant in densification and grain growth of SnO2 ceramics.
Effects of Substrate Temperature and Sputter Gas on the Physical Characteristics, Chemical Composition and Preferred Orientation of ZnO Thin Films
Journal of the Korean Ceramic Society, volume 34, issue 12, 1997, Pages 1227~1234
ZnO thin films were prepared by rf-magnetron sputter at various conditions. Crystallinity, microstructure, chemical composition, and optical composition, and optical properties of the films were investigated as functions of substrate temperature (R. T.-50
) an sputter gas (O2/Ar=0-50%). ZnO thin films grown at 50
with sputter gas of pure argon as well as at R. T. with sputter gas of a mixture of argon & oxygen(O2/Ar=2%) exhibit a strong tendency of (002) preferred orientation, compared with a considerable random orientation at the other conditions. The thin films with (002) preferred orientation has a chemical stoichiometry of Zn/O-1.01, a band gap of 3.3eV, and a packing density of 98% respectively.
In Situ Observation of Domain Structure of
Using Polarizing Microscope
Journal of the Korean Ceramic Society, volume 34, issue 12, 1997, Pages 1235~1239
Sodium niobate single crystals were grown by high temperature solution growth with Na2O/B2O3 flux. The phase transitions and domain structures of sodium niobate were observed using transmission polarizing microscope from room temperature to
. There was imperfect extinction region within as-grown crystals and this area could be removed by heat treatment. The area existed within crystal till 3
, in which temperature the space group of sodium niobate is changed from Pbma to Pmnm. The phase transition from Pbma to Pmnm happened abruptly with changing domain structure. At 48
, the colors and walls of domains were changed. All domains disappeared and the space group of sodium niobate was changed from P4/mbm to Pm3m at 64
. When sodium niobate changed from high temperature phase to low temperature phase, the memory effect of domain structure was not observed.
Preparation of Silicon Carbide Ceramics with Self-reinforced Microstructure by the Control of Starting Phases
Journal of the Korean Ceramic Society, volume 34, issue 12, 1997, Pages 1240~1246
Silicon carbides with self-reinforced microstructure which hore a small grain matrix and dispersed large grains with rod-like type were prepared by the liquid-phase sintering and the control of starting phases of raw materials. The specimens with self-reinforced microstructure could be obtained from the compacts with mixed compositions of
-SiC and 10-50 %
-SiC powders and by the pressureless sintering at 185
for 5h. Large grains with rod or plate-like types were 4H-SiC and small grains with equi-axed type were 6H-SiC. Fracture grains with rod or plate-like types were 4h-SiC and small grains with equi-axed type were 6H-SiC. Fracture toughness of specimens with self-reinforced microstructure was increased by the crack deflection and formation of microcracking due to the existence of rod-like large grains during crack propagation.
Synthesis of Sinter-active
Powders Using Urea
Journal of the Korean Ceramic Society, volume 34, issue 12, 1997, Pages 1247~1253
Sinter-active yttria powders were prepared by a solution precipitation with using a self-decomposing precipitation agent NH2CONH2(urea). The cold-pressed powders can be sintered to full density and the microstructure of grains less than 200 nm at a temperature as low as 120
. The activity of the yttria powder has been controlled by varying nucleation conditions during precipitation and by minimizing formation of aggregates. The type of precursor is decisive in preparation of a sinter-active oxide powder, and urea is desirable as a precipitation agent for an active yttrium oxide powder.
Influence of Applied Electric Field on Low Temperature Degradation of Y-TZP
Journal of the Korean Ceramic Society, volume 34, issue 12, 1997, Pages 1254~1260
Influence of applied electric field on the low temperature degradation of 3 mol% YaO3 stabilized tetragonal zirconia polycrystals(3Y-TZP) was investigated using X-ray diffractometry of specimens aged under the dc field of 1.1 kV/mm in silicone oil both of 12
. After the aging, the tetragonal to monoclinic phase transformation was observed only on the specimen surface of 3Y-TZP faced to the anode. This indicated that the surface was overcrowded with oxygen ions as a result of diffusion of oxygen vacancies toward the cathode-sided surface. To elucidate an influence of the applying time of the electric field on the extent of the degradation of 3Y-TZP in air, specimens were aged fore 0-2 hours under the electric field in the oil bath of 12
and then subsequently aged for 3h at 22
in air. The longer the specimens were aged under the field, the more extensive the transformation to the monoclinic phase was on the specimen surface faced to the cathode, probably originated from a high diffusion rate of oxygen ions due to a steep oxygen vacancy concentration gradient.
Fluidity and Setting Properties of Cement Paste by Adding of Fluoro Anhydrite and Fly Ash
Journal of the Korean Ceramic Society, volume 34, issue 12, 1997, Pages 1261~1267
Four kids of powder admixtures(A, B, C, D) based on anhydrite were manufactured by mixing at a fixed rate of II-anhydrite, fly ash and active silica as an industrial by-product. Fluidity properties of cement paste such as mini-slump, apparent viscosity with elapsed time, as well as setting time of cement pastes of these admixtures substituted up to 11wt% of cement were compared to those of cement paste(SS) substisuted by marketed high-strength powder admixture(S). Among these powder admixtures, the fluidity of cement pastes(PA, PC) substituted by A and C powder admixtures manufactured from II-anhydrite and fly ash had an excellent property than that of cement paste substituted by marketed powder admixture and also a good fluidity-retention effect with elapsed time by adding of superplasticizer. The setting time of cement paste substituted by powder admixtures based on anhydrite slightly retarded than that of cement paste substituted by marketed powder admixture.
A Study on the Coating Fracture in Silicon Nitride Bilayer : I. Effect of Elastic/Plastic Mismatch
Journal of the Korean Ceramic Society, volume 34, issue 12, 1997, Pages 1268~1274
Effect of elastic/plastic mismatch on the fracture of Si3N4 coating in Si3N4/Si3N4 -BN bilayer was investigated by Hertzian indentation testing. A different amount of mismatch between two layers was induced by different BN addition in the substrate layer, and Hertizian cracks were induced by using WC ball indenter. As a result, as the elastic/plastic mismatch between coating and substrate layer increased, the coating fracture easily occurred. A bending stress induced by different elastic/plastic mismatch was main reason to cause the fracture of coating.
Electrical Properties of Pr-doped ZnO Varistors
Journal of the Korean Ceramic Society, volume 34, issue 12, 1997, Pages 1275~1281
ZnO varistors containing 5.0 at% Co3O4 and Pr6O11, ranging from 0.1 to 1.0 at%, were sintered at 130
. The I-V characteristics and nonlinear coefficients of the specimens were investigated with respect to Pr addition and sintering temperature. In general the specimens sintered at 130
showed better varistor characteristic than those fired at 135
, which seemed to be related with the liquid phase formation during sintering. The barrier heights obtained from C-V relations, 0.29-1.36 eV, were different from those acquired using resistivity-temperature plots measured at low voltage per grain boundary. Therefore the estimation of potential barrier heights using C-V relations is better suited for the specimens prepared in this study. The carrier densities obtained using C-V relations were ~1018 cm-3.