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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
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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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The Sialon Synthesis from Natural Silica and Al Powder Mixture by Using Home-style Microwave Oven
Journal of the Korean Ceramic Society, volume 34, issue 1, 1997, Pages 1~6
In home-style microwave oven, silica-Al powder mixture was ignited among pellets and combustion wave-front propagated to produce Si+AIN+Al2O3 as resultant phases under N2 atmosphere. Without cooling pro-cedure the resultant phases of Si+AIN+Al2O3 continously absorbed microwave and were heated to be syn-thesized into sialon phases. This synthesis rate of sialon phases from silica-Al powder mixture in home-style microwave oven was higher than that in conventional furnace, and total processing time was around 1 hour, which could save energy and cost.
A Tribological Study of SiC-Steel Couples
Journal of the Korean Ceramic Society, volume 34, issue 1, 1997, Pages 7~12
The wear behavior of SiC in SiC-steel sliding couple was investigated under various wear test conditions, such as solid state sliding - dry and wet air atmosphere - or lubricated sliding, sliding velocity and at-mosphere temperature. The effect of SiC fabrication process on the SiC wear rate was also studied under varying sliding velocities. Humidity of air plays a lubricating role in the solid state sliding, while the wear behavior is largely influenced by the sliding velocity, especially if the atmosphere is extremely dry. The fa-brication process of SiC and the surface roughness result in different wear rate depending on the magnitude of sliding velocity. High temperature is, among others, the most deteriorating factor of wear, thus being strongly wear-accelerating even under boundary lubrication.
Preparation and Characterization of Water-Soluble Glass Through Melting Process(II) : Dissolution Characteristics, Bactericidal Effects and Cytotoxicity
Journal of the Korean Ceramic Society, volume 34, issue 1, 1997, Pages 13~22
Water-soluble phosphate glasses containing Ag and Cu ion were prepared through melting process. Dis-solution characteristics, bactericidal effect and cytotoxicity were investigated with composition and time in D. I. water using the powdered sample. Surface change were observed with increasing dissolution time us-ing the bulk specimen. Dissolution amount was maximum at the molar Ag:Cu ratio of 1 and increased with increasing time. The behavior of dissolution was total dissolution from the early stage. But no new layer was observed at the glass surface during dissolution. The bactericidal effect for pseudomonas sp, e. coli, sta-phylococcus aureus, and salmonella increased with increasing dissolution amount and therefore great bac-tericidal effect appeared. The result of cytotoxicity experiment to L929 showed that solution with more than 10 ppm of Ag ion had strong cytotoxicity.
The Effect of Grain Boundary Diffusion on the Boundary Structure and Electrical Characteristics of Semiconductive
Journal of the Korean Ceramic Society, volume 34, issue 1, 1997, Pages 23~30
Semiconductive SrTiO3 ceramic bodies were prepared by conventional ceramic powder processes in-cluding sintering in a reducing atmosphere. Sodium or potassium ions were diffused from the surface of the sintered bodies into the inner region using thermal diffusion process at 800-120
. The effects of such ther-mal treatments on the electrical and chemical characteristics of the grain boundaries were investigated. The presence of sodium or potassium ions at grain boundaries produces non-linear current-voltage behaviors, electrical boundary potential barriers of 0.1-0.2eV, and threshold voltages of 10-70V. The diffused ions form diffusion layers with thicknesses of 20-50nm near the grain boundaries, reducing the concentration of strontium and oxygen.
Microstructure and Dielectric Properties in
Ceramics with Excess MgO Addition
Journal of the Korean Ceramic Society, volume 34, issue 1, 1997, Pages 31~36
The effects of 0 to 10mol% excess MgO addition on the microstructure and dielectric properties in 30Pb(Mg1/3Nb2/3)O3-20PbTiO3-50Pb(Mg1/2W1/2)O3 ternary system were investigated. Samples were prepared by mixed oxide and precursor methods to compare the role of excess MgO. Excess MgO enhanced grain growth and increased dielectric constant. The dielectric constant and tesmperature dependence of dielectric constant of the sample sintered at 100
with 5mol% MgO were above 5,000 and +25% to -50% from - 55
, respectively. For these specimens the phases percent were mainly perovskite and Pb2WO5, which was confirmed by XRD analysis. Also the amount of cubic pyrochlore Pb3Nb4O13 and PbWO4 were de-creased with sintering temperature and MgO addition. BSE image showed the chemical inhomogeneous dis-tribution. Crystal phase formed at each sintering temperature and the chemical inhomogeneous distribution caused the decrease of the temperature dependence of dielectric constant.
Preparation of Barium Ferrite Thin Film by Sol-Gel Method
Journal of the Korean Ceramic Society, volume 34, issue 1, 1997, Pages 37~44
Barium ferrite thin films on the thermal oxidized Si substrate were prepared by using sol-gel method (dip coating) from the sol of composition ratio of 5.25, designated by mole ratio 2Fe/Ba. The gelation process was largely divided into 4 step, and the sol prepared by reaction for 90 minutes at 8
was the suit-able for coating. Needle shaped particles formed on the coating layer were placed parallel to substrate and the inclination was increased with film thickness. The easy-direction of magnetization of needle shaped par-ticles was long-axis direction.
The Synthesis and Mechanical Property of Calcium Silicate Hydrates Using the Amorphous Silicates
Journal of the Korean Ceramic Society, volume 34, issue 1, 1997, Pages 45~55
Various kinds of amorphous silicates were used as raw materials to synthesize building materials based on calcium silicate hydrates. Relationships between the reactivities of silicates and castabilities of the building materials were investigated. In addition, effects of the reactivities of silicates on the mechanical properties of casted specimens were studied by analyzing microstructures and hydrates produced. As the reactivity of silicate increase, the press castability increases and the crystal size of hydrate and pore size also increase. For the mechanical properties, the flexural strength increases with decreasing crystal size and densifing microstructure. The compressive strength is greatly dependent on the den-sification of microstructure rather than crystal size of hydrate. Based on the results, diatomous ma-terials are desirable due to high reactivity and formation of densified microstructure. Slag and fly ash may be partially used as raw materials with amorphous silicates to manufacture building materials based on calcium silicate hydrates.
Preparation of Activated Carbon Fiber-Ceramic Composites and Its Physical Properties
Journal of the Korean Ceramic Society, volume 34, issue 1, 1997, Pages 56~62
The PAN (Polyacrylonitrile) based carbon fiber-ceramic composites (CFCC) were prepared from mixtures of short carbon fibers, phenolic resin and ceramic binder. The effects of carbonization temperature of a pre-cursor fiber, the stabilized PAN fiber, on the specific surface area and the bending strength of the activated CFCC were studied in this work. The precursor fiber was carbonized at 80
, respectively. The CFCC were activated at 85
in carbon dioxide for 10~90 minutes. As the burn-off of the activated CFCC made of the precursor fiber carbonized at 80
was increased from 37% to 76%, the specific surface area in-creased from 493m2/g to 1090m2/g, and the bending strength decreased from 4.5MPa to 1.4MPa. These values were about two times larger than those of the activated CFCC of which precursor fiber was car-bonized at 100
. The effects of carbonization temperature of a precursor fiber on the specific surface area and bending strength of the activated CCFC were explained by bonding force between carbon fiber and car-bonized phenolic resin as well as by relative shirnkage between carbon fiber and ceramic film.
Content on the Properties of Direct-Bonded Magnesia-Chromia Bricks
Journal of the Korean Ceramic Society, volume 34, issue 1, 1997, Pages 63~69
The effects of Cr2O3 content on the properties of direct-bonded MgO-Cr2O3 bricks were investigated in the range of 10 to 30 wt% of Cr2O3. Modulus of rupture of bricks was excellent in about 20 wt% of Cr2O3 content. The corrosion resistance of bricks was improved by increasing Cr2O3 content and was directly pro-portional to the amount of secondary spinels. On the other hand, the spalling resistance of bricks depended on the amount of flux rather than Cr2O3 content.
Fabrication of 3Y-TZP/SUS316 Functionally Graded Material by Slip Casting Method Using Alumina Mold
Journal of the Korean Ceramic Society, volume 34, issue 1, 1997, Pages 70~78
3Y-TZP/SUS316 Functionally Graded Material (FGM) was fabricated by slip casting method. Alumina mold was used to overcome problems of gypsum mold in slip casting process, and the optimal dispersion con-ditions of 3Y-TZP/SUS316 binary slurries was determined using electrokinetic sonic amplitude and a viscometer, and observing sedimentation behavior. The properties of the specimens casted by gypsum mold and alumina mold were compared in terms of changes in shrinkage rate, drying and sintering conditions, and microstructure. It was found that the specimens obtaine from the alumina mold showed a clean surface, easier thickness control of each layer, and higher productivity. Especially, no degradation was observed in the SUS316 prepared using alumina mold. Thus it is desirable to use porous alumina mold rather than gyp-sum mold for the slip casting of 3Y-TZP/SUS316-FGM.
Preparation and Characterization of Anti-reflective and Anti-static Double Layered Films by Sol-Gel Spin-Coating Method
Journal of the Korean Ceramic Society, volume 34, issue 1, 1997, Pages 79~87
Anti-reflective and anti-static double layered films were prepared on the VDT panel by sol-gel spin-coating method. Their electrical, opticla, and mechanical properties were investigated. The outer SiO2 film with low re-fractive index was coated over the inner ATO(Antimony-doped Tin Oxide)-SiO2 film which was prepared by mixing ATO sol with SiO2 at molar ratio of 68:32 to satisfy the interference condition of double layers. The heat treatment was conducted at 45
for 30 min where residual organics were completely removed. The sheet resistance of ATO single layer showed the minimum value of 6
at 3 mol% addition of Sb and that of SiO2/ATO-SiO2 increased slightly with increasing SiO2 mol% up to 30 mol%, and then increased steeply to the value of 3
at 32 mol%. The reflectance of double layered films was about 0.64% at the wavelength of 550nm and the transmittance increased about 3.20%. The hardness of double layered films was almost the same as that of uncoated VDT panel, 471.4kg.f/mm2.
Effect of Oxidation of Bond Coat on Failure of Thermal Barrier Coating
Journal of the Korean Ceramic Society, volume 34, issue 1, 1997, Pages 88~94
The oxidation behavior of the NiCrAlY bond coat and thermal fatigue failure in the plasma-sprayed thermal barrier coating system, ZrO2.8wt%Y2O3 top coat/Ni-26Cr-5Al-0.5Y bond coat/Hastelloy X superalloy substrate, in commercial use for finned segment of gas turbine burner were investigated. The main oxides formed in the bond coat were NiO, Cr2O3, and Al2O3. It divided the oxide distribution at this interface into two types whether an Al2O3 thin layer existed beneath ZrO2/bond coat interface before operation at high temperature or not. While a continuous layer of NiO was formed mainly in the region where the Al2O3 thin layer was present, the absence of it resulted in the formation of mixture of Cr2O3 and Al2O3 beneath NiO layer. Analyses on the fracture surface of specimen spalled by thermal cycling showed that spalling occurred mainly along the ceram-ic coat near ZrO2/bond coat oxide layer interface, but slightly in the oxide layer region.
Study on Oxidation-Reaction Bonding of Aluminum Compact by Pressureless Powder Packing Method
Journal of the Korean Ceramic Society, volume 34, issue 1, 1997, Pages 95~101
Using aluminum powder with average particle size of 22.1
m, aluminum compact made by Pressureless Powder Packing Method showed 52% green density. The activation energy of aluminum oxidation was cal-culated from the weight change of TG, and it was varied in the range of 16~64 kJ/mol. It was found from the variation of the activation energy and the observation of the microstructure that oxidation was de-pendent on the destruction of oxide film and the melt-out of aluminum. Aluminum compact was reaction-bonded at 1000~140
for 4~60hrs, and oxidation was dependent on temperature rather than time. Reac-tion-bonded aluminum oxide at 140
for 60hrs showed 92% oxidation percent. It was sintered at 1
for 15hrs and the sintered body showed 62% relative density.
Preparation and Characteristics of
Structural Ceramics : II. Mechanical Properties and Thermal Stability of Sintered Body
Journal of the Korean Ceramic Society, volume 34, issue 1, 1997, Pages 102~108
ZrO2 powders stabilized with Y2O3 and CeO2 of various compositions were prepared by the coprecipitation of water-soluble ZrOCl2.8H2O, YCl3.6H2O and Ce(NO3)3.6H2O, and their compacts were pressurelessly sintered at 1400 and 150
for 2hrs in air. 2mol% Y2O3-ZrO3 showed the most superior strength (1003MPa) and microhardness (12.6GPa), while 10 mol%CeO2-ZrO2 had the hightest toughness (13.3 MPa.m1/2) after sintering at 140
. The addition of Y2O3 into Y2O3-ZrO3 decreased mean grain size and increased strength and hardness but decrease toughness. On the other hand, the addition of CeO2 into Y2O3-ZrO2 enhanced the stability of tetragonal phase during low-temperature aging for a long time under hydrothermal atmosphere.
The Intensity Scale of Multiple Scattering of X-rays in Non-Crystalline Solids
Journal of the Korean Ceramic Society, volume 34, issue 1, 1997, Pages 109~113
When the intensity of X-rays scattered from amorphous materials (very weakly absorbing materials) is measured using standard diffractometric technique, the intensity caused by multiple scattering is obtained in the measured X-ray intensity. Computer programs have been developed to estimate the intensity of the mul-tiple scattering obtained in vitreous SiO2 and B2O3 with various X-rays. Using the above computer program, the intensity ratios of multiple scattering to single scattering in vitreous SiO2 were 0.10~0.16% at CuK
, 0.98~5.87% at MoK
, and 1.88~17.86% at AgK
in the range of 2
. Therefore, pri-or to the structural analysis of vitreous SiO2 and B2O3 performed experimentally using X-ray diffractometric technique, the intensity data measured in MoK
radiations must be corrected for multiple scattering effect.