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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 31, Issue 12 - Dec 1994
Volume 31, Issue 11 - Nov 1994
Volume 31, Issue 10 - Oct 1994
Volume 31, Issue 9 - Sep 1994
Volume 31, Issue 8 - Aug 1994
Volume 31, Issue 7 - Jul 1994
Volume 31, Issue 6 - Jun 1994
Volume 31, Issue 5 - May 1994
Volume 31, Issue 4 - Apr 1994
Volume 31, Issue 3 - Mar 1994
Volume 31, Issue 2 - Feb 1994
Volume 31, Issue 1 - Jan 1994
Selecting the target year
Wetting Characteristics and Interfacial Reaction at
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 815~822
Sessile drop studies of molten Al on single crystal sapphire substrate were conducted to understand the wetting behavior and interfacial reaction at Al/Al2O3 interface. To investigate the wetting mechanism, the variation in contact angle was determined with time. The contact angle obtained in this study decreased exponentially with time. This result means that the driving force for wetting is the reduction in interfacial energy between liquid Al and sapphire caused by the interfacial reaction. The closer examination revealed that the reaction was the dissolution of sapphire by molten Al. Ti has been frequently used to improve wetting on ceramic materials. Therefore, the influence of Ti content on the wetting behaviour was investigated in this work. The equilibrium wetting angles of pure Al, Al-0.3 wt%Ti, and Al-1.0 wt%Ti at 100
, and 54
respectively. The difference is considered as the result of the change in interfacial energy caused by the reaction between Ti and sapphire and the interfacial reaction formed the reaction products of varying stoichiometry (TiO, Ti2O3, TiO2 etc.).
Application of Compression Molding to Determination of Binder System for Low Pressure Injection Molding
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 823~828
Dispersion condition of Si3N4 powder in molten wax was established by comparing relative viscosity of mixture with 20 vol% solids loading, while the evaluation of compression-molded sample was demonstrated as an effective method for developing a binder system for injection molding. The best dispersion of Si3N4 powder in molten wax was achieved when Si3N4 powder was treated with 5% stearic acid, and the critical powder volume fraction was determined to be about 0.51 from density measurement of compression-molded samples. Samples containing polar secondary binder showed markedly improved green strength, higher thermal expansion and increased wicking rate in the early stage.
Dielectric and Remnant Mechanical Properties Due to Cyclic Stress in PZT Ceramics
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 829~834
The aim of this study is to investigate the changes in dielectric properties, Young's modulus and remnant compressive strength with compressive cyclic loading in PZT of tetragonal, MPB and rhombohedral composition. Higher relative dielectric constants appeared in the poled condition than the unpoled condition for all the compositions. After poling treatment remarkably higher relative dielectric constants were observed particularly in MPB, tetragonal compositions. Until five percent of the expected fatigue life was exhausted, the dielectric constant increased with compressive cyclic stress in MPB and rhombohedral while it remained nearly constant in tetragonal. During the subsequent compressive cyclic stress, dielectric constant decreased in all the three compositions. As the compressive cyclic stress is applied the change of Young's modulus was coincided with the change of remnant compressive strength.
Addition on the Synthesis and Microwave Dielectric Properties of
Fabricated by Oxalate method
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 835~840
In this study, the synthesis of Ba2Ti9O20 powder having chemically homogeneous and highly pure fine particle size distribution was attempted by the oxalate method. And the effects of ZrO2 addition was investigated. The four compositions (X=0, 0.028, 0.048, 0.068) of Ba2(Ti9-x, Zrx)O20 were prepared by precipitation reaction of BaCl2, TiCl4, and ZrOCl2, with oxalic acid and NH4OH acting as a precipitating agent and a pH regulator respectively, in aqueous solution. In case of 4.8 mol% ZrO2 addition, the single phase Ba2Ti9O20 was obtained at 120
and its dielectric properties was excellent showing K=40.5, Q=4621 at 5.4 GHz.
Sintering Behavior, Dielectric and Pyroelectric Properties of
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 841~848
The sintering behavior of La-modified PbTiO3 ceramics was investigated in order to improve the poor sinterability of PbTiO3. Addition of La improved the sinterability. It was confirmed that this improvement was due to the decrease in tetragonality ratio c/a of crystal lattice. The variations of dielectric constant and pyroelectric coefficient were measured with temperature. It was observed that with the increase of La content, Curie temperature decreased and dielectric constant at room temperature increased. La-modified PbTiO3 ceramics had smaller pyroelectric figure of merits than those of pyroelectric materials in use. The effects of grain size on dielectric and pyroelectric properties were also investigated. The change of grain size had effect on maximum dielectric constant and pyroelectric coefficient, but is had little effect on pyroelectric figure of merit at room temperature. The closer examination near ferro-paraelectric phase transition temperature revealed that the behavior of phase transition approached a more relaxor character with the increase of La content and the decrease of grain size.
Manufacture of SiC-TiC System Composite by the Reaction-Bonded Sintering
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 849~860
The microstructural evolution and crystalline phases of this infiltration of Ti+Al liquids in TiC, SiC, TiC+C, and SiC+C preforms have been investigated. As the Ti and Al mixing ratio in Ti+Al infiltrated liquid changes, the newly formed reaction products, which were reacted from the Ti+Al liquid with preforms, consisted of three major phases as Ti3AlC, Al2Ti4C2 or Al4C3. The TiC grain shape was changed to spheroid, when Ti3AlC was formed. In case of Al2Ti4C2 formation, the platelet grain was formed from the original TiC grain. When Al4C3 was formed, nodular or intergranular fine-grained Al4C3 was formed around the TiC grain, while the original TiC grain shape was not changed.
Radiative Transitions of
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 861~868
CaO-Al2O3 glass is a good candidate as optical fiber amplifier and laser. In this study, optical properties for 4I13/2longrightarrow4I15/2 transition of Er3+ ions doped in CaO-Al2O3 glasses were investigated. Optical absorptions, radiative transition probabilities and lifetimes for 4I13/2 level were evaluated by using Judd-Ofelt theory. Also, induced- emmision cross-sections of 4I13/2longrightarrow4I15/2 transition were calculated. Radiative transition probability and lifetime of 4I13/2 level were 144.6s-1, 690
respectively for 60CaO.40Al2O3 glass(FS0) and 152.6s-1, 660
for 54 CaO.36Al2O3.10SiO2 glass (FS10). Each induced-emission cross sections for FS0 and FS10 was 0.749
. Obtained values were comparable with those of ZBLA glass studied as optical fiber amplifier and laser material.
Evaluation of Electrical Characteristics on Semiconducting Ceramics Using Complex Impedance Resonance Method
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 869~873
Electrical properties of each interfacial layers on semiconducting ceramics have been analized and evaluated by complex impedance resonance method as functions of ambient temperatures and applied voltages. From the analytical results, it can be observed that the interfacial layers in a semiconducting ceramics vary individually with the ambient temperature and then this influence the total properties. Also, it has been confirmed that the applied voltage on semiconducting ceramics affect mainly the electrode interface, and thus the resistance and capacitance decrease due to the variation of potential barrier layers.
Multi-layer Coating for Improvement Anti-wear Property of Graphite
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 874~878
To increase the anti-oxidation and anti-wear properties of graphite for the propellant-burning environment, SiC, Pt and Al2O3 multi-layer coatings were conducted succesisvely and the optimum condition was researched. The SiC layer was produced by pack cementation and SiC layer in thickness of 30
coating was produced after coating for 6 hours. Pt layer was coated by sputtering, and the Al2O3 layer was coated by reactive sputtering. the thickness of Pt layer and Al2O3 layer was less than one-tenth of that of SiC layer. The pack coated specimens and multi-layer coated specimens were made using above conditions and test-fired. The test result showed that the wear rate of SiC layer is approximately 1/10 compared to that of uncoated graphite.
The Synthesis of
Powders by Coprecipitation Technique and Their Sintering Behaviors
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 879~885
Coprecipitation technique was used to synthesize ZrO2+12 mol% CeO2 powders with ZrOCl2.8H2O and Ce(NO3)3.6H2O as starting materials. The powders were dried on different conditions such as distilled water, ethanol, and azeotropic distillation. The powders prepared by azeotropic distillation showed weak aggregation of particles and the average particle size of powders calcined at 85
for 1 hour was 0.19
. The optimum sintering temperature and holding time are 130
and 2.5~10 hours, respectively. Beyond the optimum conditions, a phase transition from tetragonal to monoclinic causes to produce cracks in the sintered bodies and to decrease the density.
An Effect of
Ratio on the Characteristics of RF Magnetron Sputtered
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 886~892
Structural and electrical properties of BaTiO3 thin films deposited on Pt/SiO2/Si substrates by RF magnetron sputtering method have been investigated. Crystallization behavior and electrical properties were studied for the films deposited under various sputtering gas compositions (Ar+O2 gas mixture) and substrate temperatures. All the films deposited above 50
were all crystallized and their preferred orientation changed from (001) to (111) with the addition of oxygen gas. The dielectric constant of films deposited in pure argon was about 110 and showed little dependence on the substrate temperature. But that was increased as the ratio of O2/Ar increased and its substrate temperature dependence was discernible. The highest dielectric constant reached to 550. In addition, the films deposited in mixed gas showed stable dielectric properties against the frequency and temperature.
Synthesis of Aluminum Nitride Powder from Aluminum Hydroxide by Carbothermal Reduction-Nitridation
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 893~901
In this study, AlN powder of fine particle size and of high purity was synthesized by the carbothermal reduction-nitridation of monodisperse, spherical Al(OH)3 which had been prepared by sol-gel method using Al(O-sec-C4H9)3 as the starting material. Depending on the mixing order and kinds of reducing agents, the optimum condition for the preparation of AlN was determined as follows. AlN single-phase was produced by the carbothermal reduction-nitridation of (1) Benzene-washed Al(OH)3 and the reducing agent, carbon, which was mixed in a ball mill: for 5 hours at 140
under NH3 atmosphere; (2) The mixture prepared by hydrolysis of alkoxide solution into which carbon had been dispersed beforehand: for 5 hours at 135
; (3) Al(OH)3 Poly(furfuryl alcohol) composite powder: for 2.5 hours at 135
; (4) The mixture of Al(OH)3 and polyacrylonitrile: for 5 hours at 140
. Addition of CaF2 increased the nitridation rate when carbon or polyacrylonitrile was used as the reducing agent; but it had no effect on the nitridation rate when furfuryl alcohol was used as the reducing agent.
A Study on the Prediction and Reduction of Residual Stress in Glass (I): Analysis of Residual Stress in Glass by Instant Freezing Model
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 902~910
Residual stress measurements were made for cylindrical glass rods to compare experimental results with the calculated values obtained by Instant Freezing Model. According to the photoelastic measurements, the stress ratio of surface compression and center tension was increased from 1.4 to 2.0 as the heat-treatment temperature was lowered, the fictitious forzen temperature was found to be closer to the heat-treatment temperature and the fictitious coefficient was increased.
Preparation and Characterization of Alumina Thin Film by Sol-Gel Method (II); Synthesis of Alumina Sol for Coating and Preparation of Coating Films
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 911~919
As the study for preparation of single-layer anti-reflective coating on glass, the conditions of synthesis of sol for coating and of reproducible coating procedure were investigated. In case of water-based sol, coating was impossible because of poor wettability of sol. The Substitution of solvent with ethanol improved the wettability of sol on the glass surface, and optimum amount of ethanol for substitution was 70 vol%. Maximum specific surface area and total pore volume of water-based sol were 268.7
/g and 0.315 cc/g, but after substitution, those values increased to 404.1
/g and 0.376 cc/g, respectively. The upper limit withdrawl speed of coating in order to get clean coated films without aggregations or stains was 7 cm/min. In case of addition of 0.1 mol HNO3 and substitution with 70 vol% ethanol and heat-treatment at 40
for 1 hour, thin film with thickness of 94 nm was obtained at withdrawl speed of 4 cm/min. The thickness of thin film was independent of drying time.
Effects of Ta Doping in Sputter-deposited PZT Thin Films
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 920~926
Ta doped PZT thin films were prepared by a reactive sputtering method with a 3-gun magnetron co-sputter, and effects of Ta doping on physical and electrical properties of the films were studied. Within the doping range of 0 to 3.6 at%, Ta doping enhanced the crystallographic orientation of (110), but reduced that of (100). Ta doped PZT had a larger grain size of about 20
compared with that of 5
for un-doped PZT. Pits and holes of PZT films which used to appear with annealing at high temperature due to evaporation of PbO were much suppressed with addition of Ta. The leakage current could be reduced down to 1.27
and the charge storge density as large as 25.8
Preparation of Alumina Composite Membranes by Chemical Vapor Deposition
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 927~933
Alumina composite membranes were prepared by chemical vapor deposition (CVD) using aluminum-tri-isopropoxide as a precursor. Porous alumina supports were used in deposition, which were in disk shape with mean pore diameter of 0.1
and prepared by slip-coasting process. film deposition morphology on porous support was simulated through depositing alumina film on polycrystalline silicon pattern, and its step coverage observed by SEM showed one deviated from uniform step coverage. N2 permeability through composite membranes and the pressure dependence decreased as the deposition time increased. Initially, the N2 permeability of the top layer was tend to decrease rapidly, and then the degree of decrease in N2 permeability was tend to diminish with deposition time. The N2 permeability increased with heat treatment temperature and the crack was generated in top layer at 100
Study on the Polymer Gel Fiber of Alkali Resistance Zirconia System for GRC
Journal of the Korean Ceramic Society, volume 31, issue 8, 1994, Pages 934~940
Fibers of ZrO2-SiO2 system were prepared from the hydrolysis and condensation of Si(OC2H5)4 and Zr(OnC3H7)4 with different H2O/alkoxide molar ratios. It was found that fibers could be drawn in the viscosity range of 1~100 poise from HCl catalyzed solutions with lower water contents of the mole ratio H2O/alkoxide, r 2. The fibrous gels were converted into the corresponding oxide glass fibers by heating at 80
. Mechanical test was performed on E, A and 20ZrO2-80SiO2 glass fibers reinforced cement in order to investigate the flexural strength. The flexural strength value of 20ZrO2-80SiO2 glass fibers reinforced cement was greater than those of E and A. The chemical durability of the fibers in alkaline solutions increased with ZrO2 content. The weight loss due to the corrosion by 2N-NaOH solutions at
for 160 hours was about 0.31
10-2 mg/dm2 for the 20ZrO2-80SiO2 glass fibers, which was superior to that of Vycor glass.