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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 26, Issue 6 - Jun 1989
Volume 26, Issue 5 - May 1989
Volume 26, Issue 4 - Apr 1989
Volume 26, Issue 3 - Mar 1989
Volume 26, Issue 2 - Feb 1989
Volume 26, Issue 1 - Jan 1989
Selecting the target year
Studies on the Time Dependent Electrical Conductivity of Rutile Single Crystal
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 1~6
The phenomena that the electrical conductivity of rutile single crystal changes with time were investigated along the a and c crystallographic axes, at 85
and Po2 in the range of 1~10-18.5atm. The D.C. conductivity decreased with and saturated some value after ca. 100 hours. But the A.C. conductivity showed no time dependence in the whole Po2 range. These experimental results suggest that the time dependence of D.C. conductivity of rutile single crystal is due to space charge polarization effect; the electrode was Pt which is complete electronic conductor, while the sample was TiO2 which is mixed conductor.
Effect of MgO Contents on Electrical Properties and Oxygen Sensing Characteristics in Co1-xMgxO Ceramics
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 7~12
The effects of composition ratios and sintering conditions in Co1-xMgxO ceramics on the sintering characteristics, electrical properties and oxygen sensing characteristics were investigated. In the same sintering conditions, porosity decreased with increase of MgO contents. The relationshiop of temperature and resistance in Co1-xMgxO ceramics showed NTC(negative temperature coefficient) characteristics at the temperature range from
. In the case of pure CoO, however, the PTC(positive temperature coefficient) characteristics were shown over about 90
. The electrical conductivity of Co1-xMgxO ceramics decreased proportionally with decrease of oxygen partial pressure at the range from 1 to 10-4(atm). Particularly, Co0.5Mg0.5O ceramics showed the highest sensitivity to oxygen gas.
A Study on the Crystallization of Grain-Boundary Phases in Si3N4-Y2O3-Al2O3 System
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 13~20
After sintering Si3N4 containing 20wt% of variable composition ratio of Y2O3 and Al2O3 at 1
, the specimens were annealed at 125
for 5, 10, 15 hours in order to crystallize the remanining oxynitride glass phases. The main grain-boundary crystalline phases in the Si3N4-Y2O3-Al2O3 system were melilite and YAG. By annealing 15hrs. at 125
, almost all of the glasses were crystallized. During the growth of melilite, lattice volyume of
-Si3N4 was increased as Al3+ and O2- ions in the oxynitride glass diffuse into
-Si3N4 lattice, but during the growth of YAG, lattice volume of
-Si3N4 was decreased by reverse diffusion of Al3+ and O2- ions. In case of crystallization of glass phase to melilite, thermal expansion of sample was decreased, but in case of crystallization to YAG, inverse phenomen on was observed.
Studies on Film Growth and Mechanical Properties of TiN by Chemical Vapor Deposition
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 21~30
Titanium Nitride (TiN) was deposited onto the SKH9 tool steels by chemical vapor deposition (CVD) using a gaseous mixture of TiCl4, N2, and H2. The effects of the deposition temperature and input gas composition on the deposition rate, microstructure, preferred orientation, microhardness and wear resistance of TiN deposits were studied. The experimental results showed that the TiN deposition is thermally activated process with an apparent activation energy of about 27Kcal/mole in the temperature range between 1200
K and 1400
K. As H2/N2 gas input ratio increased, the deposition rate increased, showed maximum at H2/N2 gas input ratio of 1.5 and then decreased. Mechanical properties such as microhardness and wear resistance have close relation with the microstructure and preferred orientation of TiN deposits. It is suggested that the equiaxed structure with random orientation increases the microhardness and wear resistance of TiN deposits.
Synthesis of AlN-SiO2-Al2O3 System
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 31~36
In order to synthesize AlN-polytypes from AlN-SiO2-Al2O3 system, composition A (AlN/SiO2/Al2O3=1/0.3/0.05, mole ratio) and composition B(AlN-SiO2-Al2O3=1/0.2/0.05, mole ratio) were used. AlN-polytypes were produced by nitriding the mixture at 175
under N2 atmosphere. For lower reaction temperature, 15R phase was produced and in the case of higher reaction temperature, AlN phase was only produced. As each composition was heated at 185
in N2 atmosphere, produced main phases were 15R phase for composition A and 21R phase for composition B respectively. The fracture surfaces of produced reactants showed porous skeleton structure.
Stress Induced-Domain Formation Mechanism in LiNbO3 Single Crystals
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 37~42
Periodic layered domain structures in doped LiNbO3 crystals grown by Czochralski method were obtained by thermal fluctuation and crystal rotation with inhomogeneous radial temprature distribution. The stressinduced domain formation mechanism model was suggested and discussed.
A Study on Piezoelectric Properties and Thermal Expansion of Rhombohedral Phase PZT
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 43~50
This experiment was conducted to investigate correlation between microstructure and electrical properties according to Zr/Ti mole ratio in Rhombohedral Phase PZT. Domain behavoir was investigated by the change of thermal expansion coefficient. Piezoelectric properties, the temperature dependence of dielectric constant and the change of dielectric constant before and after poling were measured. Crystal structure, the measurement of lattice parameter were carried by X-ray analysis. Domain pattern before and after poling was examined by SEM.
Wear and Wear Transition Mechanisms During Sliding in Al2O3
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 51~58
Wear and wear transition mechanisms during sliding as a function of time in Al2O3 have been studied to understand the wear behaviour of brittle ceramic materials. Commercial Si3N4 ball was rotated against flat Al2O3 specimens which were hot pressed and polished using upto 1
diamond paste. Paraffin oil was used as a lubricant. Experimental data show that wear of Al2O3 is separated into distinct two stages, i.e., initial stage of slow wear and final stage of rapid wear. Microstructural observations at worn surface show that wear occurs through grooving and grain pull-out in the initial and final stage respectively. TEM observations beneath the worn surfaces show that grain pull-out starts to occur by the propagation of grain boundary cracks induced by dislocation pile-up throughthe surface.
Crystal Growth of Superconducting Y-Ba-Cu-O by Flux Technique
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 59~66
Single crystals of the superconducting Y-Ba-Cu oxide were grown by a flux technique. Stoichiometric mixture with excess BaO and CuOcontent was melted at 130
, followed by fast cooling to 108
to prevent crystallizing of CuO. It was then reheated to 110
followed by being held at this temperature to control the number of nuclei, and cooled by 5
/hr to 80
. This procedure was repeated with various compositions and crystals were obtained in cavity. Molten solution was seperated to two parts : the upper part of almost CuO and the rest of different composition. Appropriate composition of flux was 30mol% BaO and 70mol% CuO due to the seperation of molten solution. Single crystals have the habit of thin plate with good developed (001) crystal face, XRD, EDAX and single crystal X-ray investigations were carried out. The grown crystals have tetragonal structure with the lattice parameters a=b=3.84
, and the space group P4/mmm. The crystal surface were observed by SEM.
A Study on Composition and Firing Temperature of Bone China Body
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 67~72
In order to define the composition range of bone china body with use of calcium phosphate, kaolin, quartz and feldspar as raw materials, we varied calcium phosphate from 40 to 55wt/o and selected basic composition by the change of raw materials in ternary system. After these bodies were fired at 120
their properties were closely tested to determine the compositions and firing conditions of bone china body.
Preparation and Characteristics of Electroless Nickel Electrode for Semiconducting Ceramics
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 73~80
Preparation and characteristics of electroless Ni-P and Ni-B systems for semiconducting ceramics have been investigated as a function of deposit rate, reducing agent and pH variation. The effect of DMAB as ruducing agent is greater than that of sodium hypophosphite. The nickel electrode prepared from the nickel-phosphorus system with sodium hypophosphite shows low contact resistance of 0.99ohm compared with the resistance of 10chm in the electrode prepared from the nickel-boron system with DMAB. The contact resistance increases with increasing pH valuein the nickel-phosphorus system with sodium hypophosphite. The ratio of Ni to P is about 76.0/24.0 for the contact resistance of 0.99ohm in the above system.
Preparation of Alumina and Amorphous Silica from Clay Minerals
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 81~90
High purity alumina and amorphous silica were prepared from Ha-dong kaolin by means of appliance of sulfuric acid. The effect of sulfuric acid concentration, reaction temperature and reaction time on the formation of aluminum sulfate was investigated. The precipitation conditions ofaluminum sulfate from the sulfuric acid solution with ethanol and ammonium hydroxide were deteremined. In the optimum condition, the conversion of aluminum oxide in kaolin to aluminum oxide powder was 85.0 percent. Alumina powder was prepared by calcination of the precipitates, and its purity was 99.0 percent.
Synthesis of High Tc Superconductor YBa2Cu3O7-
by Oxalate Coprecipitation Method I. Theoretical Considerations based on Analytical Chemistry
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 91~99
The concentrations of hydroxide, carbonate and oxalate for Y(III), Ba(II) and Cu(II) ions in an aqueous solution have been theoretically calcuated with respect to pH and their solubility diagram could be obtained. The optimum pH ofr oxalate coprecipitates at room temperature was estimated as<4, which was not influenced by carbonates and hydroxides in H2O solvent. The yield is dependent on the concentration of added oxalic acid, but the concentration of oxalic acid was fixed as 0.1M in this calculation for simplicity.
Preparation of Aluminum Nitride from an Alkoxide and its Properties
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 100~108
Aluminum hydroxides were prepared by the alkoxide hydrolysis method using Al-isopropoxide as a starting material and NH4OH as a catalytic agent. When Al-isopropoxide was hydrolyzed in a H2O-NH3 system, only Al(OH)3 was obtained over all pH values. However, AlOOH was formed besides Al(OH)3 when Al-isopropoxide was hydrolyzed in a H2O-NH3-isopropyl alcohol system. The AlOOH/Al(OH)3 ratio was increased as the isopropyl alcohol content was increased. The hydroxides, Al(OH)3 and AlOOH, obtained in this study and the commerical products,
-Al2O3 and AlOOH were subjected to the carbothermal reduction and nitridation reaction to product AlN powder, using carbon black as a reducing agent under N2 atmosphere at various temperatures. AlN was synthesized from the obtained Al(OH)3 and the commercial AlOOH at 145
, however, synthesized from the obtained AlOOH and the commercial alpha-alumina at 135
. The temperature difference is assumed to be attributed to the reactivity of those powders. AlN powder prepared from the Al-isopropoxide was observed to have the narrower particle size distribution than that prepared from the commercial
-Al2O3 or AlOOH.
Powder Properties of ZrO2-MgO System Prepared by Co-precipitation Method
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 109~115
The properties of the powders of ZrO2-MgO system prepared by co-precipitation method using ZrOCl2.8H2O and MgCl2.6H2O as starting materials were investigated after calcination from
. The crystallization temperature of amorphous ZrO2 was increased as MgO contents increased. The crystallite size of ZrO2 was increased with increasing calcination temperature. The crystallite size of tetragonal ZrO2 calcined at 100
for 1hr wa about 45nm, and MgO contributed effectively to promoting stability of tetragonal Zirconia.
Reliability Analysis of Statistical Failure Probability in Sin/Hip Si3N4
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 116~122
MOR test and concentric ring test were performed to evaluate the failure probability of sin/hip Si3N4 under uniaxial and biaxial stress state, respectively. Their failure probabilities were analized with KARA program based on Weibull PIA model and Batdorf model with 5 criteria, and they were compared with experiments. PIA model is in best accordance with experiments in higher fracture strength regions, especially for Pf 0.3. But in lower fracture strength region, none of the models predicts the failure probabilities appropriately.
Effect of Ca/P Mole Ratio on the Sintering of Hydroxyapatite Powders Synthesized by the Wet Method and its Microstructure
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 123~131
Hydroxyapatite powders were syntehsized by the reaction of Ca(NO3)2.4H2O and (NH4)2HPO4 in aqueous solution. The effect of the Ca/P mole ratio in the starting solution on the sintering of the powders and its microstructure was studied. When the Ca/P mole ratio in the starting solution was 1.69, the relative density of the sintered bodies was more than 95%. The sinterability was decreased as the Ca/P mole ratio in the starting solution was increased (Ca/P mole ratio >1.67). Hydroxyapatite sintered bodies obtained from the Ca/P mole ratio=1.69 had very excellent bending strength. The best bending strength was obtained at 110
and its value was 1220kg/
. The average grain size was 0.277
. Most of sintered bodies were almost shown 100% hydroxyapatite phase. However, in case of the Ca/P mole ratio=1.64 hydroxyapatite was decomposed to
-whitlockite above 120
Preparation of Hydrated Basic Aluminum Salts by Homogeneous Precipitation Method and Their Thermal Decomposition
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 132~138
High purity(99.99%) spherical particles of hydrated Basic Aluminum Salts(BAS) were prepared by a homogeneous precipitation process utilizing the urea decomposition reaction and characterized by XRD, SEM, TG-DTA, IR and PSA methods. Amorphous hydrated BAS was precipitated in the range of pH 4~6. The molar ratio [Al3+]/[SO42-] for the precipitate particles was about 3.7. With increasing the concentration of aluminum sulfate the precipitation of the hydrated BAS occurred slowly and the precipitate particles with a narrow size distribution were fine(1-2
in diameter). At temperatures in the range 400
, desulfurization and dehydroxylization resulted in weight loss with 22%. When the precipitate particles were thermally treated, the crystlline
-Al2O3 was identifited by XRD at 50
-Al2O3 particles were transformed into
-Al2O3 at 100
. A vermicular network was produced by calcining at 125
Microstructures and Optical Properties of Composite Crystals in the System (Bi2O3)0.85.(Nb2O5)0.15-6Bi2O3.SiO2
Journal of the Korean Ceramic Society, volume 26, issue 1, 1989, Pages 139~145
An eutectic melt in the system(Bi2O3)0.85·(Nb2O5)0.15-6Bi2O3·SiO2 was unidirectionally solidfield at a rate of 0.5mm/h under a thermal gradient of 100℃/cm. Double crucibles and seed crystal plate were used in order to botain the composite crystals which had uniform microstructure throughout the ingot. The obtained composite crystals showed uniform microstructure, in which needle-like δ-(Bi2O3)0.85·(Nb2O5)0.15 crystals were arrayed in parallel in a matrix of γ-6Bi2O3·SiO2 single crystal. It was found that the <110> direction of δ-(Bi2O3)0.85·(Nb2O5)0.15 crystal was essentially parallel to the <111> direction of γ-6Bi2O3·SiO2 crystal in the composite crystals. A transverse thin plate of the composite crystals showed a high resolution optical transmission like an optical fiber array, and sharp chatoyancy was observed in the cabochon shaped composite crystals. Then, this may be useful for applications such as screen of a cathode ray tube or artificial cat's eye gem stones.