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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 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
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Fabrication and Sintering Characteristic of MgO-Al2O3-SiO2 System Ceramic Raw Materials(Mullite, Spinel and Cordierite) II. Powder and Mechanical Properties of Mg-Al Spinel Ceramics Prepared by Alkoxide
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 593~600
Fine spinel powder was prepared from the Mg-Al double alkoxide synthesized using magnesium powder, aluminum foil and sec-butyl alcohol. This powder was compared with powder prepared by mixing two commercial alkoxides. The spinelization was started at 50
and was almost completed at 100
with a good crystallinity in the double alkoxide system. In mixed alkoxide system, homogeneous spinel powder was not obtained and MgO existed as a second phase because of solubility and hydrolysis rate differences of two alkoxides. The relative density of specimen prepared by double alkoxide was 99% and specimen prepared by mixed alkoxide was 95%. The modulus of rupture of specimens prepared by double alkoxide and mixed alkoxide was 49.9kg/
Effects of Alkali and Chloride ions on the Electric Conduction of ZrF4-Based Heavy Metal Fluoride Glasses
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 601~608
Electrical properties of ZrF4-based heavy metla fluoride glasses were measured by the ac complex impedance method. The effects of alkali and chloride ions addition into fluoro zirconate glasses on the electrical conductivity were examined. The electrical conductivities of fluoride glasses show Arrhenian behavior in the temperature range of the experiment and were decreased by the addition of sodium fluoride up to 15mol%. Mixed alkali substitution resulted in conductivity minimum at intermediate composition which is commonly observed as mixed alkali effect' in alkali oxide glasses. Chloride ion substituted for fluoride ion was found to lower the conductivity.
Effect of the Treated Amounts with Asphalt and Carbon Black on the Early Hydration and the Physical Properties of Portland Cement
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 609~616
For the development of high durable portland cement, it was tested that the some physical properties of ordinary portland cements (OPC) treated with 0.3-1.5wt.% asphalt and 0.5-1.0wt.% carbon black. From the results, the contact angles of water against cements treated with more than 0.6wt.% asphalt were increased over 80 degrees, the initial and the final setting times of cement paste were delayed about 20min. according to the every 0.3wt.% increase of asphalt. The first and the second pick heights of the hydration curve of the cement were considerabely decreased and the induction period of that was increased. And so, the cumulative hydration heat of the cement which was treated with 0.6wt.% asphalt and 0.5wt.% carbon black was lower about 10cal/g than that of ordinary portland cement during 42 hydration times.
Effects of Interface Porosity on Dielectric and Piezoelectric Properties of BaTiO3-Polymer Composites of O-3 Type Connectivity
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 617~624
Piezoelectric composites of O-3 connectivity were prepared by thermosetting barium titanate-phenolic resin composite under various cruing pressure. Among three kinds of pore in O-3 type ceramic-polymer composite, such as matrix pores, particle pores, and ceramic-polymer interface pores, the effect of interface porosity on the dielectric and piezoelectric constant was investigated. In pure barium titanate ceramics, the porosity factor of dielectric and piezoelectric constants were 5.7 and 5.0, respectively. However, in BaTiO3-polymer composite, the interface porosity factor of the piezoelectric constant was greater than that of the dielectric constant, interface porosity factor b in d33 was 9.8 and in r 4.6. On the other, piezoelectric voltage constant g33 was independent of the porosity of barium titanate ceramics. But in composite system, the piezoelectric voltage constant g33 was decreased with interface porosity.
Mullitization of Aluminium Silicate Gel
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 625~630
Aluminium silicate gels were prepared by gel-technique using Al(OH)3 and TEOS as starting materials. Aluminium silicate gel as formed mullite at 120
. From this method, homogeneous mullite was formed available needle-like shaped and close compacted. As excess SiO2 mullite composition, the needle-like shaped crystal, size according to increased with SiO2, was increased from 3
but liquid phase did not affect the formation of needle-like shaped mullite. As excess Al2O3 mullite composition, the needle-shape mullite crystal could not be detected because Al2O3 acted as chunky behavior.
Studies on the Fine Sintered Mullite(II)
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 631~636
Submicron high-purity mullite powder was prepared by a colloidal sol-gel route. Boehmite and silica were the starting materials. 2wt%
-Al2O3 or ZrO2 was used as a seeding material. The gelled powder was calcined at 130
for 100min and attrition milled for 3hrs. The mullite powder obtained was composed of submicrometer and uniform particles with a narrow size distribution. It was hot-pressed at 1
for 1hr under 10MPa or was sintered at 1
for 4hrs. The bulk densities of the products made by both processes were 3.14 and 3.12g/㎤. the mechanical, thermal and electrical properties of the sintered mullite were characterized by bending strength, thermal expansion coefficient, thermal conductivity, dielectric constant and dielectric loss, etc.
Mechanical Properties of Beta-Sialon Ceramics Prepared from TEOS and Kaolin
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 637~644
Beta-sialon powder(Z=1) was synthesized by the simultaeous reduction and nitridation of the mixed powders of Hadong kaolin and silica. Silicon hydroxide was prepared from Si-alkoxide by a hydrolysis method and amorphous silica was obtained from the calcination of the prepared silicon hydroxide. Hadong kaolin was mixed with both the silicon hydroxide and amorphous silica, respectively. The average particle size was 4
and the morphology of particle was rod-like and equiaxed in the case of beta-sialon powder prepared form Hadong kaolin and silicon hydroxide(COMPOSITION A), whereas the average particle size was 3
and the morphology of particle was equiaxed in the case of beta-sialon powder prepared from Hadong kaolin and amorphous silica(COMPOSITION B). The synthesized beta-sialon powders were hot-pressed at 175
for 2 hours under 30 MPa in a nitrogen atmosphere after YAG composition(8wt%) was added to these powders as a sintering agent. The hot-pressed specimens were annealed a 140
for 4 hours in a nitrogen atmosphere. The mechanical properties of sintered bodies were investigated in terms of M.O.R., fracture toughness and hardness. The measured values are as follows. COMPOSITION A : M.O.R. 508MPa, KIC 3.5MN/m3/2, hardness 13.6GPa. COMPOSITION B : M.O.R. 653MPa, KIC 5.4MN/m3/2, hardness 13.5GPa.
Fracture Toughness and Failure Behavior of WC-Co Composites by Fracture Surface Analysis
;J.J Mecholsky, Jr.;
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 645~654
Specimens of WC-Co were indented to measure the resulting crack size and unindented samples were fractured in 3-point flexure to obtain the strength and to measure characteristic features on the fracture surface. Fracture toughness was determined using fractography and compared to those determined using identation techniques. We show that principles of fracture mechanics can be applied WC-Co composites and can be used to analyze the fracture process. The fracture surfaces were examined by scanning electron microscopy and optical microscopy. Characteristic feature observed in glasses, single crystals and polycrystalline materials known as mirror, mist, hackle, and crack branching were identified for these composites. We discuss the importance of fracture surface analysis in determining the failure-initiating sources and the failure behaviorof WC-Co composites.
A Synthesis and Characteristics for Zirconia Powders by Coprecipitation Method ; III) The Properties and Sinterabilities of ZrO2-Y2O3-Bi2O3
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 655~660
The physical properties and sinterabilities of ZrO2-Y2O3-Bi2O3 ternary system powder prepared by coprecipitation were investigated. The crystallization temperatures of ternary system were increased and the specific surface areas were decreased with increasing Bi2O3 amount as sintering agents both PSZ and FSZ. Especially, the partially stabilized zirconia showed monoclinic phase. The sinterability was increased with the amount of Bi2O3 added which caused liquid phase sintering.
Defect Structures in LiNbO3 Single Crystals Grown by Czochralski Method : Dislocation Etch Pits Morphology
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 661~669
The defect structure in LiNbO3 single crystals grown by Czochralski method from the congruently melting composition were investigated. Chemical etching patterns were studied in x-plane, z-plane, and major cleavage plane, respectively, dislocation density was higher at the periphery of crystals than at the center because the thermal stress due to radial temperature gradient had a main effect on it, as compared with dislocations formed from the solid-liquid interface. Many dislocation lineages were arranged along several directions.
Study on the Composition Analysis and Electrical Properties of Chemical Vapor Deposited PbTiO3 Thin Film
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 670~676
The PbTiO3 is well known materials having remarkable ferroelectric, piezoelectric, and pyroelectric properties. PbTiO3 thin films with a perovskite structure were successfully fabricated on titanium substrate by chemical vapor deposition. These films were characterized according to composition, crystal structure, and electrical properties. Semi-quantitative compositional analysis of the deposited films was made by Auger Electron Spectroscopy(AES). The PbTiO3 film deposited on titanium substrate at the deposition temperature 75
, the Ti(C2H5O)4 fraction 0.15, and O2 partial pressure 0.06atm, has a columnar structure and grows with(001) preferred orientation, and has stoichiometric composition. A clear dielectric transition and offset in the dc conductivity near the transition temperature(48
) were observed in the deposited lead titanate film.
The Roles of Seeds on Preparation the Silica Glass by Sol-Gel Process
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 677~681
On the preparation of silica glass by sol-gel process, we used fine powder of silica gel to prevent cracking. In this case, the best condition of silica glass preparation is the contents of 10~40wt% seed and the gelation time of solution in contract. The dried gels conversed to silica glass by heat treatment up to 125
Studies on the Synthesis of High Purity and Fine Mullite Powder (I)
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 682~690
Fine mullite powder was prepared by colloidal sol-gel route. Boehmite as a starting material of Al2O3 and silica sol or fumed silica as a starting material of SiO2 were used.
-Al2O3, TiO2 and ZrO2 were used as seeding materials. The combination of boehmite and silica was found to be the stoichiometric mullite powder. Techniques for drying used were spray drying, freeze drying, reduced pressure evaporation and drying in a oven. The gelled powder was heated at 130
for 100min and was attrition-milled for 1~3hrs. The mullite powder obtained was composed of submicrometer, uniform and spherical particles with a narrow size distribution. The mullite powder was characterized by BET, SEM, XRD and IR spectroscopy.
Synthesis of TiO2 and BaTiO3 Powders by Ultrasonic Spray Pyrolysis Method
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 691~697
Fine TiO2 and BaTiO3 powders having spherical particles were synthesized by ultrasonic spray pyrolysis of alcoholic solution of metal alkoxide in an electric furnace heated at 400-90
. Microstructure and composition of particles synthesized were observed by TEM and XRD respectively. Spectific surface area of powders synthesized was examined through BET specific surface area measurement. TEM observation revealed that the particle size did not change irrespective of pyrolysis temperature but decreased according to the increase of concentration and spherical particle was consisted of primary particles of about 0.02
. As for BaTiO3 powder, the ratio of Ti/Ba was 0.987 by EDX analysis.
Effect of Water-Soluble Polymer on the Properties of High Strength Hardened Cement Paste
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 698~704
Basic investigation for the flexural strength and water stability of hardened cement pastes using ordinary portland cement with water-soluble polyer (hydroxypropyl methyl cellulose ; HPMC) was carried out with 0.2 of water cement ratio. For molding of the specimen, the paste was mixed by twin roll mill. According to increase in the content of HPMC, the setting time of cement paste was delayed and the flexural strength was increased. The maximum flexural strength of hardened cement paste with 5.0wt% of HPMC was about 330 kg/
. The expansion of the hardened cement paste immersed in water was increased with the content of water soluble polymer(HPMC). Consequently, the strength and the water stability of the hardened cement pastes were remarkably reduced by the expansion of them.
Effect of Fe2+/Fe3+ Ratio on the Crystallization of the Scoria Glass (CaO-MgO-Al2O3-SiO2 System)
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 705~711
The glass-ceramics was prepared with the scoria(CaO-MgO-Al2O3-SiO2 system) of the locally occurring volcanic ejecta containing 10-13w/o of (FeO＋Fe2O3) by melting at 140
for 4 hours and thermally treated for nucleation and crystallization. The sucrose was added to the scoria to adjust the Fe2+/Fe3+ ratio during the melting process. The addition of 1-2w/o of sucrose showed the glass-ceramics body with the finest particle developed and dispersed over the entire range. It is concluded that the impurity content of iron oxide and titanium oxide play the most-influencial effect on the crystallization. When 1-2w/o of sucrose was added to the scoria, the value of Fe2+/Fe3+ ratio was 0.93-1.32 and showed the best result of crystallization. The nucleation temperature and time were calculated by the measurements of exothermic peak temperatures of DTA for quenched and thermally treated glasses. The nucleation temperature of scoria glass without the addition of sucrose was estimated as 75
, but the addition of sucrose by 2w/o showed the nucleation temperature 6
. The nucleation time was calculated with the same DTA curves. The nucleation times estimated were about 150min. for both of glasses without and with sucrose added. Finally, the activation energies for crystallization were calculated with the DTA data. The calculated activation energies were 143 Kcal/mole for the glass without addition of sucrose and 90Kcal/mole, 87Kcal/mole, 85Kcal/mole and 71Kcal/mole for the glasses of 1w/o, 2w/o, 3w/o and 4w/o addition respectively.
Electrical Properties of Pb(Mg1/3 Nb2/3)O3 Ceramics
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 712~718
PMN ceramics with excess MgO addition in the range of 0 to 70m/o were prepared, and their electrical properties, such as dielectric constant, tan
, diffuseness coefficient, remanent polarization, coercive field and electrical conductivity were measured. Dielectric constant and remanent polarization increased with up to 5m/o excess MgO and then decreased presumely due to the precipitation of second phase, etc. Electrical conductivity slightly increased with the addition of excess MgO.
A Study on the Ceria Stabilized Tetragonal Zirconia Polycrystals(Ce-TZP)(I) : Effect of CeO2 Content on the Mechanical Properties and Fracture Behavior of Ce-TZP
Journal of the Korean Ceramic Society, volume 26, issue 5, 1989, Pages 719~727
By using commercial zirconia powder CeO2-ZrO2 ceramics containing 8~16mol% CeO2 was made by heat treatment at 1350~155
for 1~10hr. The minimum amount of CeO2 for obtaining complete tetragonal phase was 12mol%, and in the tetragonal phase region fracture toughness of Ce-TZP was decreased with increasing CeO2 content and the maximum value was obtained when 12mol% CeO2 was added. The bending strength goes through maximum at 14mol% CeO2. Fracture mode of Ce-TZP transformed from intergranular to transgranular fracture with increasing CeO2 content, so the morphology of fracture surface of 16mol% Ce-TZP was wholly transgranular and this tendency was independent on grain size. The crystal structure of the 12mol% Ce-TZP was monoclinic with fringes along the grain boundaries which are lying in the particular plane from the TEM observation. The chemical composition of the sintered body was homogeneous as a whole and some amorphism or air pocket was observed at the triple junction.