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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Ceramic Society
Journal Basic Information
Journal DOI :
The Korean Ceramic Society
Editor in Chief :
Volume & Issues
Volume 27, Issue 8 - Aug 1990
Volume 27, Issue 7 - Jul 1990
Volume 27, Issue 6 - Jun 1990
Volume 27, Issue 5 - May 1990
Volume 27, Issue 4 - Apr 1990
Volume 27, Issue 3 - Mar 1990
Volume 27, Issue 2 - Feb 1990
Volume 27, Issue 1 - Jan 1990
Selecting the target year
The Growth of Defects
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 447~456
ZnWO4 single crystals were grown by Czochralski method. And the orientation of grown crystals were determined by Laue back reflection, and the crystals were siliced at (100), (010), (001) face before polishing. The morphologys and distribution of etch pits on each face were observed by optical microscopy. In the present study, we understood that dislocation distributjioon rely on shape of solid-liquid interface, and secondary phase acts on the dislocation source. We also observed dislocation trace(etch pits) of (100) slip plane on (010) cleavage plane.
Dynamic and Quasi-Static Fracture Toughness of
Ceramic Matrix Composite Reinforced with Sic Whiskers
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 457~464
This paper presents the influence of the loading rate on the room temperature fracture toughness of a brittle Al2O3 and a SiC whisker reinforced Al2O3 composite. Dynamic fracture toughness tests were conduced using compressive fatigue pre-cracked notched round bars loaded in tension to produce a stress intensity rate K1=106 MPa√m/sec. The experimental results show that for each loading rate the fracture toughness values obtained for the ceramic matrix composite are higher than the corresponding values for the single phase alumina. In addition, both the reinforced and unreinforced ceramic are singnificantly tougher under dynamic loading than static loading. This dynamic and quasi-static fracture initiation behaviro can be interpreted by identifying quantitatively the mode of fractuer initiation as a function of loading rate.
Properties of the System
Powder Prepared by Co-Precipitation Method(II) Effects of
Addition on Mechanical Properties and Microstructures of Y-TZP
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 465~472
The effects of Al2O3 and Cr2O3 addition on the mechanical properties and microstructures of Y-TZP ceramics obtained by co-precipitation method of ZrO2＋3m/o Y2O3, following pressureless sintering at 150
for 2h were investigated. The addition of Al2O3 and Cr2O3 improved the Y-TZP sinterability and the Al2O3 addition showed the better effect on Y-TZP sintering than that of the Cr2O3 addition. The density and microstructure had the better effect on the bending strength of specimen more than stressinduced phase transformation (SIPT) of ZrO2 from tetragonal to monoclinic phase. The hardness of the specimens was found to be depend on the relative density and the fracture toughness of Y-TZP was found to rely on the amount of SIPT. The grian size of Cr2O3-doped Y-TZP was observed to be relatively smaller and had a narrower distribution than that of Al2O3-doped Y-TZP. If decomposition reaction of Cr2O3 can be controlled at high temperatures, it is anticipated that the mechanical properties of Y-TZP can be much improved by the Cr2O3 addition.
Fabrication of Low Voltage ZnO Varistor by Seed Grain Method
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 473~480
Low-voltage ZnO-based varistors were made by seed grain method at various sintering conditions. Their microstructure and electrical properties were investigated and comlpared with those of the ZnO varistors made by a conventional method at the same sintering condition. During the sintering process, the added seed ZnO grain rapidly grew to be a gaint grain(above 500
) provinding easy current path. Therefore the breakdown voltage was lowered as much as the order of 1/10-1/5 in comparison to that of the varistor made by a conventional method. But the grain size of the giant ZnO was little influenced by sintering condition, so the breakdown voltate was also little influenced. The weight loss was decreased by the addition of the seed grain, because the giant grain decreased the evaporation area. Therefore the nonobmic property of the specimen made by seed grain method was little influencedby sintering condition. In this research the low-voltage varistor made by seed grain method showed the least leakage current when sintered at 1150
for zero hour.
Microstructural Effects on the Thermoelectric Prooperties of PbTe
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 481~486
Microstructure of polycrystalline Lead Telluride was controlled by the change of sintering conditions. Three properties which determine the thermoelectric figure of merit of the material were measured in the temperature range of 300-650K in order to investigate the effect of each sintering condition on the thermoelectric efficiency. Based on the observed experimental results, defect structure is concluded to be more important than microstructure though both can be controlled by processing variables.
Composite Powders by the Use of Emulsions : III. Emulsion-Coprecipitation Method
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 487~494
composite powders were prepared by the emulsion-coprecipitation method and the effects of preparative conditions on powder characteristics were investigated. In the preparation of
composite powders, toluene was used instead of kerosene as the oil phase in emulsions. After coprecipitation, the emulsion was easily broken into a single liquid phase by adding methanol, and then precipitates could be effectively collected by filteration. The fact that all
phases present at room temperature in composite powders calcined at
after washed by methanol had a tetragonal structure confirmed that methanol-washing enhanced the dispersibility of fine
composite powders were spherical particles of 0.2
diameter. Pellets sintered at
for 2hrs showed the relative theoretical density of 97.3% and the fracture toughness of 5.01MN/
Effect of Admixture on the Properties of High Strength Hardened Cement Paste
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 495~500
Investigation for the preparation of high strength hardened cement paste using ordinary portland cement, hydroxypropyl methyl cellulose (HPMC) with admixtures was carried out. For molding of the specimen, the paste was mixed with 0.1 of water cement ratio by twin roll mill. The maximum flexural strength of dried hardened cement paste was about 600∼700kg/㎠. When the SiC was added to the paste, the dry flexural strength was about 920kg/㎠ and the young's modulus was 5.2×105kg/㎠. When the admixtures were added to the specimens, wet strength of the harened cement paste immersed in water was showed around 50∼100kg/㎠ higher than that of plain specimen. Consequently it is recognized the water stability of hardened cement paste was remarkably improved by adequate admixture.
A Study on the Preparation and Sinterability of MgO-Doped
Powders by SprayPyrolysis Method
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 501~512
Al2O3 and 0.25wt% MgO-doped Al2O3 powders were made from the alcohol solution of Al(NO3)3.9H2O and Mg(NO3)2.6H2O by spray pyrolysis method. Each powder was prepared at 900 and 100
. Powders prepared at 90
were amorphous phase, but prepared at 100
-Al2O3 crystalline form. Particle size of the MgO-doped Al2O3 powders was in the range of 0.2-2
, but undooped powders shwoed comparatively wider range of particle size. All the powders prepared at 900 and 100
were transformed to
-Al2O3 crystalline form by calcination at 110
for 1hr. Each powder was sintered at 1600, 1650 and 1
for 2hrs. MgO-doped Al2O3 body sintering at 1
showed 99% of relative density but undooped Al2O3 showed 95% of relative density, even sintered at higher temperature of 1
Diamond Film Deposition by Microwave Plasma CVD Using a Mixture of
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 513~520
Diamond film was deposited on Si wafer substrate from a gas mixture of methane, hydrogen and oxygen by microwave plasma-assisted chemical vapor deposition. The effects of the pre-treatments of the substrate and of the oxygen addition on the diamond film synthesis are described. In order to obtain diamond film, the substrate was pre-treated with 3 kinds of methods. When the substrate was ultrasonically vibrated within the ethyl alcohol dispersed with 25
diamond powder, the denset diamond film was deposited. Addition of oxygen in the gas mixture of methane and hydrogen improved the crystallinity of the deposited diamond film and also increased the deposition rate of the diamond film more than two times.
Crystallization and Transparency of
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 521~528
Li2O.2SiO2 glass-ceramics were made from the melt by the nucleation and growth treatment. The optimum nucleation temperature and time were determined from DTA curves of as-quenched and thermally treated glasses, and found to be 44
and 3hrs. The optical microscopic technique was also used to support this result. The volume fractions of crystals present in the partially crystallized specimens were measured using the optical microscopy and the amorphous X-ray scattering methods. The degree of crystallization increased with increasing the crystallization temperature and time. The crystalline phase identified by X-ray diffraction was lithium disilicate. As the crystallinity increased up to 95%, the transmittance of glass-ceramics was decreased linearly. It was also found that for the same heat treatment condition (575
, 30min), a thicker specimen showed higher transmittance, presumably due to less crystallinity.
Studies on the Impedance-Hymidity Characteristics of
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 529~535
This paper describes the factors which control the impedance-relative humidity characteristics of the TiO2-V2O5 humidity sensor. To obtain the quantitative relationships between impedance and many manufacturing parameters such as V2O5mol%, the sintering time and temperature, various sets of samples are preared and tested. With changing relative hymidity from 20% to 80%, it is measrued that the corresponding capacitance and impedance from the semicircles which complex impedance plots make. As a result we found that the impedance-relative humidity characteristics are mainly controlled by the doping amount of V2O5 total pore volume and bulk resistence of the elements. We can assume the equivalent circuits of each samples and finally control the sintering time to get a linear humidity impedance response curve which plays an important role in device making. 4mol% V2O5-TiO2 specimen sintered at 90
for 10min. show liear log(Z) vs. RH characteristics and 10mol% V2O5-TiO2 specimen sintered at the same temp. for 20min. show linear (Z) vs. RH.
Crystal Growth of Superconducting
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 536~542
Single crystals of YBa2Cu3O7-x have been grown in BaCuO2 flux at temperature of 125
and examined using XRD, EDAX and light microscopy. The YBCO crystals were grown in a cavity which was formed by the reduction of CuO and became large by the directional solidification in the crucible. The observed crystal growth habit is square planar with the c-axis normal to the plane. The surface morphology of grown crystals were growth ledges and growth sprial paterns on a (001) face.
Thermodynamic Calculations of High Temperature Bubble Formation at SiC/
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 543~547
Numerous researchers have observed the bubble fromation at SiC/SiO2 interface from 130
. According to thermodynamic calculation, the bubble could be formed from the microscopic impurities which result from the chemical vapor deposition of SiC. When C-impurity is present at the interface, it is calculated that the bubble is formed at 1511
and when Si is present, the bubble is formed at 177
. These results are very close to the prior observations, but the calculation can not explain the observation of bubble below 150
Effect of Binder Addtion Method on Microstructure and Magnetic Prooperties of Sr-ferrite
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 548~552
Effects of binder addition method during compacting on microstructural change and magnetic characteristics of Sr-ferrite system was investigated. Used binders were PVA and PEG, which were added separately or simultaneously. After compacts were heated at 50
for 3hr in air for burning out all the binders, they were sintered at 125
for 2h. Based on results, in the case of using the two binders simultaneously, comparing to single binder system, compacted density was somewhat higher but sintered density was rather lower, and abnormal grain growth was accelerated. According to these sintering characteristics, remanent magnetization and coercive force were also diminished.
Effect of Boron Carbide on Nonuniform Shrinkage during Pressureless Sintering of
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 553~559
The nonuniform shrinkage has been investigaed in pressureless sintering of
-SiC, where born carbide and phenolic resin as a carbon source are used as densification aids. Compacted specimens, prepared from the granulated powder, were sintered at 215
for 30min in Ar atmosphere. Using the fresh and unseasoned graphite crucible, the upwarped specimens were obtained, while specimens were uniformly shrunk in the seasoned crucible. This effect is mainly due to the nonuniform distributjion of boron carbide during heatig, which originates in the reaction of boron carbide with CO gas, providing from the result of SiO2 reduction with carbon during heating.
Effect of Gypsum of the Early Hydration Characteristics of the System
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 560~566
The early hydration characteristics according to the C3A polymorphism and the presence of gypsum, in order to establish the hydration mechanism of the system C3S-C3A, have been studied. The hydration rate of C3A was changed according to the its crystal structure and influenced the hydration of C3S. That is, the hydration rate of C3S was accelerated in case of orthorhombic-C3A, but that was slightly retarded in case of melt-C3A than that of cubic-C3A. In the system C3S-C3A-gypsum, the retardation phenomenon of the reaction of monosulfate formation was observed in case of both orthorhombic and melt-C3A.
Preparation of Transparent
Polycrystals by Unidirection Solidification of Melt
Journal of the Korean Ceramic Society, volume 27, issue 4, 1990, Pages 567~573
Solidification condition for preparing transparent
-6Bi2O3.GeO2 polycrystals by unidirectional solidification of melt, were investigaetd and the properties of the polycrystals prepared were measured. The
-6Bi2O3.GeO2 polycrystals showing transparency like a single crystal were obtained by the unidirectional solidification of
-6Bi2O3.GeO2 melt at a solidification rate of 0.5mm/h under a thermal gradient of 12
/cm. The transparent polycrystals obtained showed the same photoconduction and optical activity as the
-6Bi2O3.GeO2 single crystals grown by Czochralski method. But the electro-optic effect of polycrystals was heterogeneous because the colummar
-6Bi2O3.GeO2 crystals were not oriented to the particular crystallographic direction.