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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Ceramic Society
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Journal DOI :
The Korean Ceramic Society
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Volume & Issues
Volume 32, Issue 12 - Dec 1995
Volume 32, Issue 11 - Nov 1995
Volume 32, Issue 10 - Oct 1995
Volume 32, Issue 9 - Sep 1995
Volume 32, Issue 8 - Aug 1995
Volume 32, Issue 7 - Jul 1995
Volume 32, Issue 6 - Jun 1995
Volume 32, Issue 5 - May 1995
Volume 32, Issue 4 - Apr 1995
Volume 32, Issue 3 - Mar 1995
Volume 32, Issue 2 - Feb 1995
Volume 32, Issue 1 - Jan 1995
Volume 1, Issue 4 - 00 1995
Volume 1, Issue 3 - 00 1995
Volume 1, Issue 2 - 00 1995
Volume 1, Issue 1 - 00 1995
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Densification and Enhancement of the Hydration Resistance of CaO with Aluminum
Journal of the Korean Ceramic Society, volume 32, issue 5, 1995, Pages 527~534
In this research, the emphasis was focused on the rearrangement and densification behavior of CaO particles when the aluminum was added to improve the hydration resistance. For the case of 0.5vol% Al added specimen, the rearrangement of CaO particles due to liquid aluminum was terminated near 140
where the theoretically calculated fractional volume of solid reached 0.74 under Ar atmosphere. The density of the specimen sintered at 155
for 5hrs reached 96% of relative theoretical density when the ambient was switched to O2 at intermediate and final stages of the sintering. The weight gain due to the hydration after 60 days under 72% of relative humidity at 26
was less than 1%.
Microwave Dielectric Properties of
Ceramics in the Response Surface Methodology
Journal of the Korean Ceramic Society, volume 32, issue 5, 1995, Pages 535~542
The effect of sintering temperature, sintering time and forming pressure on microwave dielectric properties of (Zr1-xSnx)TiO4 ceramics containing 1.0wt% B2O3, 0.3 wt% La2O3 and 1.0wt% NiTa2O6 was investigated using the response surface methodology. The optimum values of processing variables were determined based on the reproducibility. The optimum values of the dielectric constant of >35. Q.f0 of >55000 and
could be obtained when the sample was pressed at 500~600kg/
and sintered at 1500~155
for 2~3 hrs.
Preparation of Li-ferrite Powders by Hyrtothermal Method
Journal of the Korean Ceramic Society, volume 32, issue 5, 1995, Pages 543~548
Li-ferrite powders were prepared from mixture of Fe and Li salts using a hydrothermal method. Their crystal structure, microstructure and magnetic property were investigated with X-ray diffraction analysis, chemical analysis, SEM, and VSM. In the case of using FeCl3 as a precursor, Li-ferrite powders were synthesized. However, Fe3O4 was formed when the precursor was a divalented Fe2SO4 or FeCl2. The precipitation rate of Li-ferrite was increased as the reaction temperature increased. The optimum conditions of synthesis were the mole ratio of Fe+++/Li+=2, pH 13, the reaction temperature of 25
and the reaction time of 120min. With this condition, the spherical particles with good dispersion were obtained with average particle size of 0.4
and saturation magnetization of 65 emu/g.
Spray Drying of Ferrite Powders and the Characteristics of the Granule
Journal of the Korean Ceramic Society, volume 32, issue 5, 1995, Pages 549~558
Mn-Zn ferrite granules were prepared by spray drying of the slurry containing different kinds and concentration of binders at various spray drying temperatures and atomizing pressures. The characteristics of the spraydried granules were analyzed according to the processing variables of spray drying and the slurries containing different solid loading and kinds and concentration of binders. Typical shape of the spray dried granules was spherical. The granules spray dried at 15
were more spherical and containing lower hollow percentage than any other granules prepared at higher temperature. The granules prepared at higher atomizing pressures were more spherical and become smaller in size. The granules prepared using slurry containing higher solid loading were larger in size and less defective in shape. As increasing the concentration of binder the number of donut-shaped granules was increased and the size distribution become broader. The granules prepared using the slurry containing PVA 205 were more spherical than those containing PVA 217 and PVA 117. As the amount of granules which were donut-shaped or dimpled increased the compaction response were less effective. The hollows were not fractured completely even at hight pressures and remained after sintering.
EFfect of Molding Temperature and Debinding Conditions on Fabrication of Alumina Component by Injection Molding
Journal of the Korean Ceramic Society, volume 32, issue 5, 1995, Pages 559~566
Alumina powder was coated with stearic acid and then mixed with isotactic polypropylene, atactic polypropylene as binders at 15
for 2 hours. The mixture was then injection molded at various mold temperatures using injection molding machine to investigate the effect of the molding temperature and debinding parameters on the formation of the defects. The molded specimens were debinded in both air and nitrogen atmospheres. Wicking and solvent methods were also used to enhance debinding efficiency. The specimens were prefired at 120
and then sintered at 150
for 3 hours. Various defects were formed at mold temoperature of 3
and any noticeable defect was not formed at 85
. The density of green body increased with mold temperature. Debinding in air atmosphere was more effective than in nitrogen atmosphere. Results also proved that wicking and solvent treatments helped minimize the number of defects.
Addition on the MIcrostructure and PTCR Characteristics in Semiconducting
Journal of the Korean Ceramic Society, volume 32, issue 5, 1995, Pages 567~574
The effect of MnO2 addition to 0.1mol% Sb2O3-doped BaTiO3 ceramics on microstructure and PTCR characteristics was studied. The PTCR characteristics was observed when 0.01 and 0.02 wt% MnO2 were added and sintered at 132
for 1 hour. The characteristics can be explained by the changes in the number and size of the abnormal grain growth due to the liquid phase during sintering. when the amount of MnO2 addition was 0.03 wt%, the sample showed NTCR characteristics with room-temperature resistivity over 109 Ωm regardless of the sintering temperature. This behavior can be described by the microstructure change due to the abnormal grain growth and charge compensation effect by MnO2 added. The room-temperature resistivity was increased as the amount of MnO2 was increased. And the specific resistivity ratio (pmax/pmin) showed maximum at 0.02wt% MnO2.
Y-TZP Sintered with Spherical Fine Powders Prepared by Ultrasonic Spray Pyrolysis
Journal of the Korean Ceramic Society, volume 32, issue 5, 1995, Pages 575~581
Zr0.94Y0.06O1.97 powder was synthesized by the ultrasonic spray pyrolysis with various concentrations of starting solution and the influence of powder characteristics on sintering behavior was investigated. Powders prepared at 75
were characterized as narrowly distributed submicron spherical particles, which were crystalline, nonagglomerated, and compositionally homogeneous. The changes in concentration from 0.01 to 01. mol/ι increased mean particle size from 0.24 to 0.38
and decreased the specific surface area from 14.2 to 2.9
/g. The relative density of the specimen from the powders, prepared with the solution concentration of 0.01 mol/ι, was 98% after sintering for 2 hr at 1,45
and the monoclinic phase was observed after sintering at 1,55
. As the concentration of starting solution was increased, the formation temperature of monoclinic phase was lowered.
Phase Transition adn Crystal Structure Analysis Using Rietveld Method in the
Journal of the Korean Ceramic Society, volume 32, issue 5, 1995, Pages 582~586
The crystal structures of (Na0.3Sr0.7)(Ti0.7M0.3)O3 (M=Ta, Nb) compounds were determined using the Rietveld method. Due to the tilting of a oxygen octahedron, (Na0.3Sr0.7)(Ti0.7Nb0.3)O3 had a superlattice of doubled a, b and c of simple perovskite. The crystal structure of (Na0.3Sr0.7)(Ti0.7M0.3)O3 was tetragonal with a space group 14/mmm. The crystal structure of (Na0.3Sr0.7)(Ti0.7M0.3)O3 was a cubic with space group Pm3m, in which no tilting of oxygen octahedron was observed. The difference in the oxygen tilting of these two materials was due to the larger covalency of Nb-O bond than that of Ta-O bond, which induced a strong
Nb0 bonding in (Na0.3Sr0.7)(Ti0.7M0.3)O3. Therefore, the higher transition temperature of (Na0.3Sr0.7)(Ti0.7M0.3)O3 could be related to the larger tilting of oxygen octahedron.
Abnormal Grain Growth Behavior of
Ceramics with Addition of Seed Grains
Journal of the Korean Ceramic Society, volume 32, issue 5, 1995, Pages 587~593
Abnomal grain growth behavior of BaTiO3 ceramics was investigated with addition of seed grains. It was foudn that the nucleation rate of abnormal grain was constant and growth of abnormal grain was linearly increased with sitnering time, regardless of amount of seed grains. These facts were also confirmed by fitting of the volume fraction of abnormal grain vs. sintering time using Avrami type equation (n=4). It was suggested that seed grains did not change the nucleation rate or growth mechanism of abnormal grain but increase the number of abnormal grains at initial stage of sintering and then it led to fine microstructure of BaTiO3 ceramics.
Change of Particle Size of Spherical Alumina Powders Prepared by Emulsion Method in the Region of Low Hydroxypropylcellulose Concentration
Journal of the Korean Ceramic Society, volume 32, issue 5, 1995, Pages 594~600
Spherical alumina gel powders were produced by hydrolysis of aluminum sec-butoxide (Al(sec-OC4H9)3) in a n-octanol/acetonitrile mixed solvent. The enlargement of particle size was induced by increasing HPC (hydroypropylcellulose) concentration (0.005, 0.1, and 0.05 g/ι) and emulsion-state aging time (10 min and 360 min). Mean particle sizes of dried alumina gel powders increased from 1.4
at 10-min emulsion-state aging time and from 1.9
at 360-min emulsion-state aging time as HPC concentration increased from 0.005 g/ι to 0.05 g/ι. At the same HPC concentration, particle size of dried alumina gel powder increased with increasing of emulsion-state aging time from 10 min to 360 min. The increase in the average particle size of dried alumina gel powder with increase in HPC concentration was interpreted as the enlargement of particles from alkoxide emulsions unprotected by HPC. The produced dried gel powder calcined at 115
for one hour transformed to
The Effect of Frit on Bonding Behavior of Low-firing-substate and Cu Conductor
Journal of the Korean Ceramic Society, volume 32, issue 5, 1995, Pages 601~607
The bond strength between the low-firing-substrate and Cu conductor depended on the softening point and the amount of frit added to the metal paste. The addition of 3 wt% frit (softening point: 68
) to the metal paste resulted in the improvement of bond strength, which was approximately 3 times higher (3kg/
) than that of non frit condition. It was also found that fracture surface shifted to the ceramic substrate in the interface region. These phenomena were attributed to the frit migration into the metal-ceramic interface. It was thought that the migration of glass frit occurred extensively when the softening point of glass firt was 68
. The sheet resistance of Cu conductor remained constant by the addition of 4 wt% frit regardless of softening point of frit. For all samples with more than 4 wt% frit, the sheet resistance increased abruptly.
A Study on the Photoluminescence of Porous Si
Journal of the Korean Ceramic Society, volume 32, issue 5, 1995, Pages 608~616
Porous silicon (PS) was prepared under different anodization conditions and the photoluminescence (PL) was measrued. In addition PL of the naturally and thermally oxidized PS was measured. It was found that the PL peak was shifted to shorter wavelength as the anodization current density and the extent of the oxidation increased. The absence of correlation between the PL behavior and the surface hydrogen species (Si-H2, Si-H) implies that the mechanism of PL of PS is not likely related to the surface hydrogen species effect but to the quantum confinement effect.
Fabrication of Sol-Gel derived Antireflective Thin Films of
Journal of the Korean Ceramic Society, volume 32, issue 5, 1995, Pages 617~625
In order to reduce reflectance of soda-lime glass having average reflectance of 7.35% and refractive index of 1.53, single (SiO2), double (SiO2/20SiO2-80ZrO2), and triple (SiO2/ZrO2/75SiO2-25ZrO2) layers were designed and fabricated on the glass substrate by Sol-Gel method. Stble sols of SiO2-ZrO2 binary system for antireflective (AR) coatings were synthesized with tetraethyl orthosilicate (TEOS) and zirconium n-butoxide as precursors and ethylacetoacetate (EAcAc) as a chelating agent in an atmosphere environment. Films were deposited on soda-lime glass at the withdrawal rates of 3~11 cm/min using the prepared polymeric sols by dip-coating and they were heat-treated at 45
for 10 min to obtain homogeneous, amorphous and crack-free films. In case of SiO2-ZrO2 binary system, refractive index of film increased with an increase of ZrO2 mol%. Designed optical constant of films could be obtained through varying the withdrawal rate. In the visible region (380~780nm), reflectance was measured with UV/VIS/NIR Spectrophotometer. Average reflectances of the prepared single-layer [SiO2 (n=1.46, t=103nm)], double-layer [SiO2 (n=1.46, t=1-4nm)/20SiO2-80ZrO2 (n=1.81, t=82nm)], and triple-layer [SiO2 (n=1.46, t=104nm)/ZrO2 (n=1.90, t=80nm)/75SiO2-25ZrO2 (n=1.61, t=94 nm)] were 4.74%, 0.75% and 0.38%, respectively.
The Microstructure Control of SiC Ceramics Containing Porcelain Scherben
Journal of the Korean Ceramic Society, volume 32, issue 5, 1995, Pages 626~634
The SiC-porcelain powder mixtures containing 51.9wt% SiC are produced as by-products from the surface abrasion process of porcelain cores. This raw powders were used as starting materials for the synthesis of SiC containing ceramics. The specimen, which was fired at 135
from raw powders, had SiC,
, , cristobalite, mullite as crystalline phases, and the fractured microstructure showed dispersed SiC crystalline particles almost wetted with glassy matrix and spherical pores. Although the oxidation of SiC containing powder compacts wetted with glassy matrix and spherical pores. Although the oxidation of SiC containing powder compacts started at the range of 600~80
form the analysis of weight gain, the presence of
crystallien phase and cristobalite was confirmed at 100
by XRD analysis. Mullitization of specimens was accelerated by preheating before the final firing. The specimen sintered at 135
preheating consisted of SiC, cristobalite, mullite as crystalline phases, and revealed 2.24g/
bulk density, 11.73% water adsorption, porous microstructure with small amount of glassy phase. SiC contents of specimens, which was 51.9 wt% in the raw powders, reduced to 37~22 wt% after firing at 135
depending on the preheating condition.
Effect of A-Site Substitution on the Dielectric Properties of PZN Ceramics
Journal of the Korean Ceramic Society, volume 32, issue 5, 1995, Pages 635~641
The effects of A-site substitution with alkaline-earth ions (Ca, Sr and Ba) on the perovskite-phase formation and dielectric properties for Pb1-xMx(Zn1/3Nb2/3)O3 (0.0 x 0.5)-based relaxors were studied. Considerable improvements in the sinterability and the extent fo perovskite formation were observed with increasing the A-site substitution (x) and sintering temperature. The maximum dielectric permittivity appeared at x=0.1 for Sr and Ba substitutiion, while the relative dielectric permittivity was almost invariant in the case of Ca ion substitution. Curie temperature decreased with increasing relative amount of Sr and Ba ions but was almost invariant in case of Ca ion substitution. With increasing the amount of x, the diffuseness parameter (
) increased but the maximum dielectric constant decreased, demonstrating an enhanced diffuse phase transition (DPT) in the presence of alkaline-earth cations.