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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 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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Powder by Glycine-Nitrate Process Using Oxide as Starting Materials
Journal of the Korean Ceramic Society, volume 34, issue 10, 1997, Pages 1003~1008
The (La, Sr)MnO3 powder used as air-electrode material of Solid Oxide Cell (SOFC) was synthesized by Modified-GNP(Modified-Glycine Nitrate Process). The powders were prepared using oxide and carbonate stable in atmosphere and nitric acid was used as a solvent of starting material as well as an oxidant for combustion. The (La, Sr)MnO3 powders were synthesized with 0.5, 1, 2, 3, 4 of glycine/cation molar ratio. The ICP (Inductively Coupled Plasma Mass Spectrometer) result represented compositional equality between synthesized and desired powders. In case of 2 molar ratio, the as-synthesized powder showed perovskite phase and specific surface area were 19
/g. After calcination of 85
, the calcined powder except 0.5, 1 molar ratio of glycine to cation showed perovskite phase.
Effect of pH on the Preparation of Spherical Fine Zirconia Powders Using Gas-Liquid Phase Reaction
Journal of the Korean Ceramic Society, volume 34, issue 10, 1997, Pages 1009~1014
Ammonia gas was blown into the solution of zirconium ion to induce precipitation of supersaturated zirconium ion at gas-liquid interface with increase in pH. The influence of pH on the phase and particle size of precipitate and calcined powders has been investigated. At pH 4.5 of zirconium solution, maximum yield of 98.7% was obtained. Above pH 4.5, there was no more increase of yield. Above pH 5.5, large aggregates consisting of primary particles were observed in precipitate and calcined powders. At pH 4.5, almost aggregate-free fine spherical zirconia powders were obtained.
Effect of Temperature Gradient on the Defects of Nd;YAG Single Crystal Grown by Czochralski Method
Journal of the Korean Ceramic Society, volume 34, issue 10, 1997, Pages 1015~1020
In the Nd;YAG crystal growth by Czochralski method, the relationship between the core formation and the solid-liquid interface was observed by controlling the temperature gradient in the furnace. When the crystal was grown along<111> direction, defects and core area were reduced as the temperature gradient increased. The optimum temperature gradient was found to be higher than 4
/cm. The Nd3+ concentration analysis by ICP-Mass showed that the segregation coefficient was about 20% higher in the core region than core-free region, where the segregation coefficients of core region and core-free region were 0.22 and 0.18, respectively.
Anisotropic Silicon Etching Using
Thin Film as a Mask Layer by TMAH Solution
Journal of the Korean Ceramic Society, volume 34, issue 10, 1997, Pages 1021~1026
RuO2 thin film has reasonably good conductivity and stiffness and it is thought to substitute for the cantilever beam made up of Pt and Si3N4 double layers in microactuators. Therefore, anisotopic Si etching was performed using RuO2 thin film as a mask layer in 25 wt. % TMAH water solution. In the etching temperature ranging from 6
, the etch rates of all the crystallographic directions increased linearly as the etching temperature increased. The etch rate ratio(selectivity) of / which varied from 0.08 to 0.14, was not sensitive to temperature. The activation energies for  direction,  direction and  direction were 0.50, 0.66 and 1.04eV, respectively. RuO2 cantilever beam with a clean surface was formed at the etching temperatures of 6
. But the damages due to formation of pin holes on RuO2 surface were observed beyond 7
. The tensile stress of RuO2 thin films caused the cantilever bending upward. As a result, it was demonstrated that the formation of conducting oxide RuO2 cantilever beam which can replace the role of an electrode and supporting layer could be possible by TMAH solution.
A Study of Effecting Factor in the Reology and Physical Properties of Cements
Journal of the Korean Ceramic Society, volume 34, issue 10, 1997, Pages 1027~1036
The reology and several physical properties of cements are studied by varying the different mineral composition and particle size distribution(PSD) of cements with closed circuit ball mill for high workability, low heat of hydration, and high strength. In this study, we found that the workability of concretes is related to the viscosity of cement, and affects to strength. Here, this workability is affected by mineral composition (C3A) and the PSD. Especially, rosin-rammer index and 44
residue in the PSD of cements are affected to water demand, casting property, slump loss, strength of cements. From the above results, the conditions of cement for high workability, low heat of hydration and high strength are to use low C3A clinker, 5-10% slag addition, and to grind cement below 0.7 rosin-rammer index, above 3.5-4.5% 44
/g blaine. Such cements are, therefore, supurior to super low heat cement and slag-blended cement in comparing the physical properties of strength, slump, slump-flow, adiabetic temperature, etc.
The Effects of Polyurethane Resin on the Water Stability of HAC/PVA Based MDF Cement Composites
Journal of the Korean Ceramic Society, volume 34, issue 10, 1997, Pages 1037~1044
Mechanical properties and water stability of HAC/PVA based MDF cement composite were investigated using polyurethane(PU) resin, silane coupling agent and various PVA. The results were as follows ; The flexural strength of MDF cement composite increased as increasing with PVA content. Low-viscosity PVA developed higher flexural strength than high-viscosity PVA under a drying curing condition. But the strength of water immersed specimen decreased. Water stability of MDF cement improved as increasing with content of PU. Consequently, water stability of polyurethane 7% added MDF cement was about 2 times higher than that of the controlled specimen. Furthermore, the strength and water stability of diamine group based silane couling agent in using MDF cement increased and improved dramatically.
Crystal Structures of Ba-ferrites Synthesize by Coprecipitation-Oxidation Method
Journal of the Korean Ceramic Society, volume 34, issue 10, 1997, Pages 1045~1052
Barium ferrites (BaFe12O19) were synthesized at the various temperature by the coprecipitation-oxidation method. X-ray diffraction Rietveld analysis for barium ferrites were performed, their microstructures were observed and their magnetic properties were measured, in order to analyze the crystal structures and determine the optimal temperature of heat-treatment. The barium ferrite, its average particle size 80 nm, was formed at 600℃ through the hematite (α-Fe2O3), but the site occupations of the Fe's in tetrahedral and bipyramidal sites and of the Ba relatively low. Increasing the heating temperature, these occupations and the magnetization increased, and the crystal c-axis decreased. These changes were very small at the heat treatment of above 800℃, but the particles were rapidly grown. It is suggested that the optimal temperature of heat-treatment is 800℃, at which temperature crystal structure is relatively stable and the particles hardly ever grow.
Dynamic Fatigue Behavior of Alumina Ceramics
Journal of the Korean Ceramic Society, volume 34, issue 10, 1997, Pages 1053~1059
The dynamic fatigue behavior of alumina ceramics was observed at room temperature using four point bending system. The dynamic fatigue fracture strength and the dynamic fatigue lifetime were observed as a function of crosshead speed and the notch length. The notched specimen showed the smaller deviation in dynamic fatigue fracture strength than the unnotched specimen. The crack growth exponent n and the material constant A of the notched specimen could be represented as functions of the notch length. Fracture strength of the specimen calculated from the notch length, when the notch length was regarded as the crack size, was in good agreement with the measured 4 point bending strength. Fracture surface of the specimen showed the different fracture modes according to the crosshead speed. The four point flexural strength, fracture toughness, Young's modulus and Weibull modulus of the alumina were measured as 360 MPa, 3.91 MPa.m1/2, 159GPa, 17.64, respectively.
The Effects of La Doping on Characteristics of PLZT Thin Films for DRAM Capacitor Applications
Journal of the Korean Ceramic Society, volume 34, issue 10, 1997, Pages 1060~1066
In this paper, the effects of La addition of PLZT thin film prepared by sol-gel method on the capacitor characteristics are investigated for gigabit generation DRAM applications. The addition of La on the PLZT capacitor results in a trade-off between charge storage density(Qc') and leakage current density(Jl). As La content increases, Qc' and permeability(εr) at 0V are reduced while Jl is significantly decreased. It is demonstrated that 5% La doping of PZT can substantially reduce Jl and also improve resistance to fatigue while incurring only minimal degradation of Qc'. Very low leakage current density (5×10-7 A/㎠ even at 125℃) and high charge storage density (100fC/㎛2) under VDD/2=1V conditions are achieved using 5% La doped PZT thin films for gigabit DRAM capacitor dielectrics. In addition, the fatigue and TDDB measurements indicate good reliability of the PLZT capacitors.
Based Solid Electrolyte Thin Films by Electrochemical Vapor Deposition
Journal of the Korean Ceramic Society, volume 34, issue 10, 1997, Pages 1067~1073
The yttria doped ceria (YDC) thin films were fabricated by electrochemical vapor deposition on the porous
-Al2O3 substrate. The growth rates of the films obeyed a parabolic rate law, which constant was 259.0
/hr at 120
. As deposition temperature (above 110
) increased, dense thin films were enhanced. Mole fraction of XYC13 had an effect upon surface morphologies. Electrical conductivity was increased with deposition temperature. The conductivity of YDC film prepared at XYC13=7.9
10-2 was about 0.097 S/cm at 104
and the activation energy of conduction was calculated to be 26.6 kcal/mol.
A Study on Properties of Low Temperature Sintering in the NiZn Ferrite System
Journal of the Korean Ceramic Society, volume 34, issue 10, 1997, Pages 1074~1082
Microstructure and permeability as a function of sintering temperature and composition were studied on the Ni
=0, 0.1, 0.2, 0.3, 0.4) which was prepared by Cu2+ substitution for Ni2+ in Ni.0.4Zn0.6Fe2O4, then followed by 8 wt% CuO and 1wt% Bi2O3 as sintering aids. It was found that NiCuZn ferrite in which Cu2+ is substituted for Ni2+ is more effective in reduction of sintering temperature than Ni.0.4Zn0.6Fe2O4, containing CuO as a sintering aid. The specimen
=0.2 sintered at 90
for 2hr exhibited the highest initial permeability value (
o=280 at 1Mhz), but the real permeability decreased at the frequency under 10 MHz. EPMA analysis showed that Ni
=0.4), sintered at 95
for 2hrs consisted of three phase regions of Ni.0.3Cu0.1Zn0.6Fe2O4 region, Cu and Bi liquid existed at the 3-point boundary, although the stabilization energy of Ni2+ is higher than that of Cu2+ in B site.
The Powder Synthesis of (Bi,Pb)-2223 System Superconductor by Oxalate Method and Thick Film Preparation
Journal of the Korean Ceramic Society, volume 34, issue 10, 1997, Pages 1083~1091
As one of the chemical powder fabrication methods, the powder preparation method by using oxalate has the following advantages; (1) easy to control the chemical stoichiometry, (2) easy to fabricate homogeneous and fine particles, and (3) easy to be thermaly decomposed at low temperature. In the present study, the initial morphology and size distribution of the powder were controlled and the homogeniaty was improved. By carefully controlling the pH with NH4OH, the Bi(Pb)-Sr-Cu-O superconducting powders were prepared and investigated for their properties. The microstructures and the superconducting properties of the pelletized samples were investigated. Also, the microstructures and electrical properties of the samples prepared by tape casting method were investigated. The fabricated powders were spherical with less than 400 nm, but most of them were agglomerated to be 1~3
in size. The critical temperature of the pelletized sample annealed at 84
for 72 hours in air was 110K. And the critical currents of annealed samples in air prepared by tape casting process for 24 hours and 72 hours were 0.6 A (Jc=600A/
) and 1.9A (Jc=1, 900A/
Electrical Discharge Machining of Alumina Ceramic Matrix Composites Containing Electro-conductive Titanium Carbide as a Second Phase
Journal of the Korean Ceramic Society, volume 34, issue 10, 1997, Pages 1092~1098
Electrical discharge machining (EDM) was attempted on a ceramic matrix composite containing non-conductive alumina as a matrix and conductive titania as a second phase, and was found successful. As the current or duty factor increased, the material removal rate (MRR) increased and the surface roughness also increased. The EDMed surface was covered with a number of craters of a circular shape having 100-200 microns of diameter. The melting and evaporation was suggested for the EDM mechanism. The bending strength decreased 44% after EDM, but the Weibull modulus increased more than twice. Combination of EDM and barre이 polishing resulted in the maintenance of the bending strength level. Temperature distribution near a spark in the sample was computer-simulated by use of finite element method, and was found to have similar shape to the one which the observed craters have.