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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 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
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Sintering Behavior of Zirconium Diboride wth Addition of Titanium Boride
Journal of the Korean Ceramic Society, volume 34, issue 11, 1997, Pages 1099~1106
In the present study, the effect of TiB2 addition on the sintering behavior of ZrB2 ceramics was studied with hot pressing under Ar atmosphere. Hot pressing experiments were carried out in graphite dies at the 1
under Ar atmosphere. The sintering density increased with increasing TiB2 contents. With the addition of 10wt% TiB2 almost theoretical density could be achieved by hot-pressing at 180
. Zr-Ti-Fe-B compound in liquid phase was observed from the EDS and WDS analysis. It was considered that sinterability was enhanced due to the mass transfer through liquid phase formed at the sintering temperature. In addition of TiB2, transition metal of groups IV, substitutional solid solution could be formed.
Vacuum Casting of Mn-Zn Ferrite Powders Prepared by Alcoholic Dehydration Method
Journal of the Korean Ceramic Society, volume 34, issue 11, 1997, Pages 1107~1112
Mn-Zn ferrite powders prepared by an alcoholic dehydration method. Vacuum casting, a kind of wet forming process was examined with this powders. As binders, polyethylene glycol and polyvinyl alcohol were used. In order to estimate this conditions, fracture morphology, densities of green and sintered bodies and the microstructure were observed. High density and homogeneous microstructure in sintered bodies were obtained in the case of 0.1 wt% PEG or 0.5 wt% PVA.
Properties of Yttria Stabilized Zirconia-Alumina Powders Prepared by Coprecipitation Method
Journal of the Korean Ceramic Society, volume 34, issue 11, 1997, Pages 1113~1120
The 2, 4, 6 and 8mol% Y2O3 doped-ZrO2 powders (20 kinds) with the addedtion of Al2O3 upto 8wt% were prepared by coprecipitation method using the zirconium oxyacetate, yttrium chloride and aluminum nitrate as starting materials. The coprecipitated powders were characterized by XRD, TG-DTA, FT-IR and SEM. The sintering properties of zirconia-alumina composites prepared by 2YSZ and 8YSZ powders containing various Al2O3 contents were also investigated. With increasing the yttria stabilizer contents, the amount of exothermic heat for zirconia crystallization decreased. And it was confirmed that the crystallizing temperature of coprecipitated zirconia powders increased and the crystallization process occurred in a wide temperature range, as Al2O3 content increased in 8YSZ.
The Improvement of Surface Roughness of Poly-
Thin Film Using Ar Plasma Treatment
Journal of the Korean Ceramic Society, volume 34, issue 11, 1997, Pages 1121~1128
In this study, the Ar plasma treatment was used to improve the surface roughness of Poly-Si1-xGex thin film deposited by RTCVD. The surface roughness and the resistivity of Si1-xGex thin film were investigated with variation of Ar plasma treatment parameters (electrode distance, working pressure, time, substrate temperature and R.F power). When the Ar plasma treatment was used, the cluster size decreased by the surface etching effect due to the increasing surface collision energy of particles (ion, neutral atom) in plasma under the conditions of decreasing electrode distance and increasing pressure, time, temperature, and R. F power. Although the surface roughness value decreased by the reduction of the cluster size due to surface etching effect, however, the resistivity increased. This may be due to the surface damage caused by the increasing surface collision energy. It was concluded that the surface roughness could be improved by the Ar plasma treatment, while the resistivity was increased by the surface damage on the substrate.
Analysis of Toughening Mechanism of Ceramic Composites by Acoustic Emission
Journal of the Korean Ceramic Society, volume 34, issue 11, 1997, Pages 1129~1138
Al2O3/20 vol%YAG composite containing equiaxed grains and Al2O3/20 vol%LaAl11O18 composite containing elongated grains were fabricated using Al2O3-Y2O3 composition and Al2O3-La2O3 composition, respectively, by hot-pressing. In order to investigate the influence of microstructural control of second phase on toughening effect of toughened ceramic composites, AE (acoustic emission) measurements have been coupled with fracture toughness experiments(SENB and SEPB method). A separation of the fracture toughness and analysis of toughening mechanism was possible using the AE technique. The fracture toughness of hot-pressed materials was estimated to be 3.2 MPam0.5 for monolithic alumina, 4.7 MPam0.5 for Al2O3/20 vol%YAG composite and 6.2 MPam0.5 for Al2O3/20 vol%LaAl11O18 composite. In monolithic Al2O3, toughening does not occur as a result of either microcracking or grain bridging, whereas, composites exhibit toughening effects by both microcracking in the frontal zone and gain bridging in the wake zone, resulting in an improvement of fracture toughness as compared with monolithic Al2O3. The fracture toughness of Al2O3/20 vol%LaAl11O18 composite is higher than that of Al2O3/20 vol%YAG composite. It may be attributed to the elongated microstructure of Al2O3/20 vol%LaAl11O18 composite, resulting relatively greater bridging effect.
Models for Relative Density and Compressive Strength of Open-Cell Ceramics with Hollow Struts
Journal of the Korean Ceramic Society, volume 34, issue 11, 1997, Pages 1139~1150
A model for predicting the relative density and the compressive strength of open-cell ceramics with three-dimensional network structure was proposed through the interpretation of their macrostructure and fracture mechanics. The equation predicting the relative density was derived under the assumption that the open-cell structure was a periodic array of the tetrakaidecahedron unit cell consisting of cylindrical struts containing the internal hollow with the shape of a triangular prism. The model for compressive strength of open-cell ceramics with the hollow strut was also developed by modifying conventional model which based on fracture behavior of them subjected to the compressive stress. Both the relative density and the compressive strength were expressed in terms of the ratio of the strut diameter to the length together with the ratio of the hollow size to the strut diameter. The proposed model for the relative density and the compressive strength of the alumina-zirconia composite with open-cell structure were accorded well with the experimental values, whereas Gibson-Ashby and Zhang's model did not show such a good agreement.
The Role of Inorganic Compounds Additions on the Matrix Microtexture Control of C/C Composite
Journal of the Korean Ceramic Society, volume 34, issue 11, 1997, Pages 1151~1158
Fracture of uni-directional carbon fiber reinforced carbon matrix composite is strongly dependent on the orientation of basal plane in graphite matrix when it is limited within matrix. The orientation of basal planes are vertically stacked to carbon fiber which results in the weakness for applied tensile or shear force in thermosetting resin derived-carbon matrix composite. Microtextural control of the matrix was tried through chemical interaction between metal carbides and furan resin derived-carbon matrix. SiC and TiO2 addition made the orientation disordered. However, porosity increased due to decomposition of SiC. Interfacial bonding could be controlled by TiO2 addition, but carbon fiber was considerably reacted with TiC during thermal treatment higher than 2
. Therefore, it is desirable to control the thermal treatment temperature at which decomposition of SiC was not serious and TiC/C was not formed eutectoid.
The Synthesis of
Powder through Glycothermal Process
Journal of the Korean Ceramic Society, volume 34, issue 11, 1997, Pages 1159~1164
Magnetite(Fe3O4) powders were synthesized through glycothermal reaction by using crystalline
-FeOOH as precursor and ethyleanne glycol as solvent. The phase, morphology and particle size of synthesized powders were characterized by XRD and an SEM. When only ethylene glycol was used as solvent, the phase was transformed from
-Fe2O3 and finally Fe3O4 at 27
for 6hr without morphological change. But by addition of water, Fe3O4 powders were synthesized at 23
for 3hr through solution-recrystalization process. As the content of water addition increased, the particle shape changed from sphere to octahedron and the partcle size increased. When the excess amount of water added, residual
-Fe2O3 was recrystalized.
Ceramics for Thermocouple Protective Tubes by SHS Process
Journal of the Korean Ceramic Society, volume 34, issue 11, 1997, Pages 1165~1172
ZrB2 powders were prepared from a mixture of ZrO2, B2O3 and Mg by self-propagating high temperature synthesis method. The combustion product was successfully obtained from a mixture of ZrO2:B2O3:Mg=1:2:8.5 molar ratio. By-product, MgO was effectively removed by leaching with 1M HCl solution at 9
for over 5hours. After leaching, the Mg content was 0.86~1.42 wt%, and the mean particle size was 4.72
. The addition of 7.5 wt%(14Ni:1.0C) as a sintering aid greatly densified ZrB2 bodies compared with that of only Ni. The ZrB2 sintered bodies containing 7.5 wt%(14Ni:1.0C) was 94.3% of the theoretical density. In this case, ZrB2 existed as a major phase and had a bend strength of 300 MPa and a vickers hardness of 2000 kg/
Effects of Particle Size Distribution of Alumina on Behaviors of Tape Casting
Journal of the Korean Ceramic Society, volume 34, issue 11, 1997, Pages 1173~1181
Effects of particle size distribution of alumina ceramics on behaviors of tape casting were investigated with emphases on the rheological characteristic of slurry, green density, green sheet strength, and sintering density. For the control of particle size distribution of alumina, the commercial grade low soda alumina, which had different mean particle size of 3.58
, were chosen and blended together. As results, the mixing of 80 wt% fine powder and 20 wt% coarse powder(designated to FC20) led to the increase of packing density and strength of green sheet, and made it easy to handle during processing without lowering of sintering density. Besides, the pseudoplastic behavior of slurry decreased with increase of the fraction of coarse alumina powder.
Thermal Decomposition and Sintering Characteristics of Cr-Deficient
Journal of the Korean Ceramic Society, volume 34, issue 11, 1997, Pages 1182~1186
La0.8Ca0.2Cr0.98O3 powder was prepared using the modified Pechini process. Various crystalline phases formed during thermal decomposition were investigated. (La,Ca)CrO4 phase, first formed from the precursor, was transformed to (La,Ca)CrO3 and CaCrO4 above 80
, which remained up to 110
. However, only (La,Ca)CrO3 phase consisting of orthorhombic and intermediate rhombohedral polymorphs was observed after sintering at 125
. The specimens sintered at 140
exhibited 98% of relative density and rather wide grain size distribution with average grain size of 3-4
. Densification and grain growth of the specimens observed above 125
were presumably attributed to liquid phase sintering resulted from melting of Ca3(CrO4)2 phase.
Low Temperature Sintering of Alumina by Boehmite Sol-Gel Method I. Phase Transformation and Sintering Behavior
Journal of the Korean Ceramic Society, volume 34, issue 11, 1997, Pages 1187~1197
Dry gel composed of primary particles more homogeneous than starting boehmite powder was prepared by dispersing and gelling the boehmite powder. The transformation temperatures of boehmite powder, dry gel seeded with 0, 1, 3, 5 wt%
-Al2O3, and ball milled gel were 1192
, and 1106
, respectively. Sintering behavior of dry gel without seed was similar to that of boehmite powder, but the sintered density of dry gel was improved as much as 10%~15% than boehmite powder. In the case of dry gel seeded with 5 wt%
-Al2O3, sintering behavior was much improved. The relative density of the gel seeded with 5 wt%
-Al2O3 was 96% when sintered at 140
for 1h. On the other hand, ball milling of the non-seeded sol for 48h resulted in the relative density of 97% when sintered at 130
for 1h. The size and amount of
-Al2O3 particles added by ball milling were 0.107
and 0.5 wt%.