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Journal of the Korean Ceramic Society
Journal Basic Information
pISSN :
1229-7801
eISSN :
2234-0491
Journal DOI :
10.4191/KCERS
Frequency :
Others
Publisher:
The Korean Ceramic Society
Editor in Chief :
Han-Ill Yoo
Volume & Issues
Volume 35, Issue 12 - Dec 1998
Volume 35, Issue 11 - Nov 1998
Volume 35, Issue 10 - Oct 1998
Volume 35, Issue 9 - Sep 1998
Volume 35, Issue 8 - Aug 1998
Volume 35, Issue 7 - Jul 1998
Volume 35, Issue 6 - Jun 1998
Volume 35, Issue 5 - May 1998
Volume 35, Issue 4 - Apr 1998
Volume 35, Issue 3 - Mar 1998
Volume 35, Issue 2 - Feb 1998
Volume 35, Issue 1 - Jan 1998
Volume 4, Issue 3 - 00 1998
Volume 4, Issue 2 - 00 1998
Volume 4, Issue 1 - 00 1998
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1
The Study of Water Stability of MDF Cement Composite by Addition of Silane Coupling Agent
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Journal of the Korean Ceramic Society, volume 35, issue 5, 1998, Pages 421~428
Abstract
The effect of silane coupling agents on the water stability of HAC/PVA based MDF cement composites which were modified with urethane and epoxy resin were studied as a function of the functional groups and addition amount of silane coupling agent. According to the composition of polymer matrix the silanes with different functional groups showed the different effectiveness. In case of the only PVA matrix the silane with vinyl functional group was more effective than other silanes. When the epoxy resin was added the silane of epoxy-methodxy group enhanced the flexural strength of dry and wet state more than other. In case of urethane-added MDF cement the silane of diamine group was effective and enhanced the water sta-bility fo MDF cement composite more and more as the addition amount of silane increased, Especially in case of warm-presed composite the effect of silane was enhanced By addition of 2wt% of silane with 야-amine group the flexural strength of urethane-added composites were enhanced by 20% more in dry state 40-70% in wet state in accord with the porosity analysis. The flexural strength of the poxy resin-added MDF cement composite was increased by addition of 1wt% and 2wt% silane of epoxy-methoxy group However the addition of 4wt% of silane decreased the flexural strength of dry and wet state by formation of closed pore in the polymer matrix.
2
Contact Damage and Strength Degradation of Yttria doped Tetragonal Zirconia Polycrystal
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Journal of the Korean Ceramic Society, volume 35, issue 5, 1998, Pages 429~436
Abstract
The mechanical properties and damage mode of {{{{ {Y}_{2 } {O}_{3} }}-doped tetragonal (Y-TZP) can-didated as biomaterials were performed under indentation stress-strain curve critical load for yield and cracking strength degradation and fatigue behavior with Hertzian indentation tests. This material shows the brittle behavior which is confirmed by indentation stress-strain response. The critical load for cracking(Pc) is much higher than that for yields (Py) indicating crack resistance Strength were strongly dependant on contact area and there were no degradation when the indenter size was
=3.18 mm suggesting that Y-TZP should be highly damage tolerant to the blunt contacts. Multi-cycle contact were found to be innocuous up to {{{{ {10 }^{6 } }} cycles at 500N and {{{{ {10 }^{5 } }} cycles at 1000N in water. On the other hand contacts at {{{{ {10 }^{6 } }} cycles at 1000 N in water did show some signs of incipient degradation. By contrast contacts with Vickers indenter pro-duced substantial strength losses at much lower loads suggesting that the mechanical integrity of this ma-terial would be compromised by inadvertent sharp contacts.
3
The Mechanical Properties of Several Fiber Reinforced Cement under Different Curing Condition
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Journal of the Korean Ceramic Society, volume 35, issue 5, 1998, Pages 437~442
Abstract
In order to investigate the mechanical properties of several fibers for reinforced cement these speciments with 2wol% of ARG and organic fibers were formed by vacuum extrusion process. After steam curing and autoclaving the flexural strength and the elastic modulus of FRC were measured. It was found that the ARG-FRC showed the elastic-brittle fracture behavior in both steam cured and autoclaved condition. And also the steam cured PP and PVA-FRC had elstic-plastic behavior but their ductility were reduced and changed to the elastic-brittle after autoclaving This change in mechanical behavior was found to be related to the thermal stablity of thes organic fibers.
4
Physico-Chemical Characterization of the Layered Double Hydroxide as Pillar Host Material
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Journal of the Korean Ceramic Society, volume 35, issue 5, 1998, Pages 443~450
Abstract
Layered double hydroxides(LDHs) [{{{{ {Mg }_{1-x } }}{{{{ {Al }_{x } }}({{{{ {OH}_{2 } }})]ζ+({{{{ {CO }`_{3 } ^{2- } ){ }_{x/2 } }}
{{{{ { yH}_{2 }O }} wioth variation of layer charge densitywere synthesized by co-precipitation methdo since their charge densities have a very important role to be det-ermined the physicochemical properties of layered materials. The XRD IR and thermal studies of them were discussed and the kinetic study for the decarbonation reaction was also carried out. From the results of XRD analysis we found that the lattice parameter and the unit cell volume were linearly decreased with the amount of Al substituents(x) in the vicinity of x=2∼10
1/3
10-1 but they had nearly constant values when the x are far from these vicinit. The activation energies for the decarbonation reaction of x=6.8, 10
1/3
{{{{ { 10}^{-1 } }} were estimated to be 47.0, 37.6, 39.3 kcal/mol The specific surface areas(90-120 m2/g) of stable hy-drotalcite-type LDHs were dractically decreased with increasing of layer charge density.
5
Synthesis of
Powder by a Precipitation-Combustion Process
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Journal of the Korean Ceramic Society, volume 35, issue 5, 1998, Pages 451~457
Abstract
powder which is one of the candidates of breeding materials for the fusion reactor was syn-thesized by a precipitation-combustion process. Although precipitates from the reaction between zirconium nitrate and citric acid were existed in a precursor solution.
could easily be obtained by using the mixed fuel of urea and citric acid in stoichiometric composition. The phases of as-synthesized powder con-sisted of
and small amounts of
and
The latter phases disappeared after the cal-cination at
for 2 h. The primary particle size and the specific surface area of as-synthesized powders were smaller than 20nm and 10-14
/g, respectively. The primary particle size of the precipitation-combustion synthesized powders was affected by the size of precipitates present in a precursor solution.
6
Variations of Reaction Sequence with Precusor Mixing Methods in the Formation of
[PZMN]
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Journal of the Korean Ceramic Society, volume 35, issue 5, 1998, Pages 458~464
Abstract
Variations of reaction sequence of
[PZMN] with precusor mixing methods were ex-amined using X-ray diffraction and dielectric characteristics. In the present study three different types of precursor mixing methods (oxide mixing PbO+
[Zn+MN] and PbO+(Zn,Mg)
[ZMN] precursor mixing) were adopted. When the oxide mixing method was used for the PZMN synthesis a Zn-rich perovskite phase and pyrochlore phase were formed. Compared with PbO+ZN+MN precursor mixing method the PbO-ZMN precursor led to a lowering of the formation temperature for perovskite sin-gle phase. These variation of composition and formation temperature of the perovskite phase were dis-cussed in terms of the difference in the solid-reaction requence between these three different types of pre-cursor mixing.
7
Microwave Hydrothermal Sythesis of PbTiO
and PMN Ceramic Powders
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Journal of the Korean Ceramic Society, volume 35, issue 5, 1998, Pages 465~471
Abstract
Lead titanate(PT) and lead magnesium niobate(PMN) ceramic powders were prepared by microwave hy-drothermal method using teflon bomb. Raw materials were Pb(NO3)2 and TiO2 for lead titanate and Pb(NO3)2 Nb2O5 and Mg(NO)3.6H2O for PMN with NaOH as mineralizer in both cases. in lead titanate synthsis rate of microwave hydrothermal method was faster three times than one f conventional hydrothermal methods In lead magnesium niobate synthsis the mixture of perovskite and pyrochlore phases was obtained by single step technique and the PMN was not obtained by double step technique due to low temperature limitation of teflon bomb.
8
Microstructure and Electric Properties of Ferroelectric SrBi
Ta
O
Thin Films Deposited by Modified Rf Magnetron Sputtering Technique
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Journal of the Korean Ceramic Society, volume 35, issue 5, 1998, Pages 472~478
Abstract
Ferroelectric SrBi2Ta2O9(SBT) films were deposited on Pt/Ti/SiO2/Si substrates at 50
using a sintered SBT target Bi and Ta targets by modified rf magnetron sputtering and then were annealed at 80
for 10min in oxygen ambinet(760 torr) The composition of the SBT films could be easily controlled using the mul-ti-targets. The film composition of {{{{ {Sr }_{0.8 } {Bi }_{2.9 } {Ta}_{2.0 } {O }_{9 } }} was obtained with SBTd sputtering power of 100 W Bi of 25W and Ta of 10 W. A 250nm thick SBT films exhibited a dense and uniform microstructure and showed the remanent polarization(Pr) of 14.4
C/cm2 and the coercive field({{{{ {E }_{c } }})of 60 kV/cm at applied voltage of 5 V. The SBT films show practically no polarization fatigue up to {{{{ {10 }_{10 } }} cycles under 5V bipolar pulse. The retention characteristics of the SBT films looked very promising and the leakage current density of the SBT films was about 1.23
{{{{ {10 }^{-7 } }}A/c{{{{ {m }^{2 } }} at 120kV/cm.
9
Properties of Modified Belite Cement with the Content of Clinker Minerals
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Journal of the Korean Ceramic Society, volume 35, issue 5, 1998, Pages 479~485
Abstract
Raw mateials such as limestone quartzite bauxite and anhydrite were used in the production of mod-ified beloite cement. Two kinds of clinker were synthesized with relatively higher content of
than that of
Concerning
the main mineral component borax (
) was added to stimu-late hydraulic reactivity and this would be possible by stabilizing
at room temperature. We had in-tended to compare burning and hydraulic characteristics of clinkers with one another by varying the amount of borax addition and to study the appropriate amount of anhydrite addition needed in the strengthening of cement during hydration. It was concluded that the effective amount of borax addition ne-eded for stabilization of
was 5 wt% in 60wt%
inclusive clinker and adding anhydrite in the ra-tio of 1.3 of
was appropriate in the production of cement by this clinker. Only ettringite was seen to contribute to the strength without additives but C-S-H was found to form along with ettringite with the addition of borax in the initial stage of hydration.
10
Deposition and Photoluminescence Characteristics of Silicon Carbide Thin Films on Porous Silicon
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Journal of the Korean Ceramic Society, volume 35, issue 5, 1998, Pages 486~492
Abstract
Silicon carbide (SiC) thin films were deposited on the porous silicon substrates by chemical vapour de-position(CVD) using MTS as a source material. The deposited films were
-SiC with poor crystallity con-firmed by XRD measurement. It was considered that the films showed the mixed characteistics of cry-stalline and amorphous SiC where amorphous SiC where amorphous SiC played a role of buffer layer in interface between as-dep films and Si substrate. The buffer layer reduced lattice mismatch to some extent the generally occurs when SiC films are deposited on Si. The low temperature (10K) PL (phtoluminescence) studies showed two broad bands with peaks at 600 and 720 for the films deposited at 1100
The maximum PL peak of the crystalline SiC was observed at 600 nm and the amrophous SiC of 720 nm was also confirmed. PL peak due the amorphous SiC was smaller than that of the crystalline SiC, PL of porous Si might be disapperared due to densification during heat treatment.
11
Preparationand Characteristics of ZnS-doped Borosilicate Glass(I)
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Journal of the Korean Ceramic Society, volume 35, issue 5, 1998, Pages 493~498
Abstract
ZnS doped borosilicate glass for nonlinear optical application was prepared by melting and precipitation process. The optical band gap of the precipitated ZnS particles ranged from 3.83 to 3.96 eV compared with the bulk ZnS energy gap of 3.53 eV. This result was interpreted in terms of a quantum confinement effect due to small crystal size. ZnS partilcle size estimated by effective mass approximation ranged from about 39 to 83
It increased wtih the increase of heat tratment time and temperature.
12
Somteromg Behavior and Electrical Characteristics of ZnO Variators Prepared by Pechini Process
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Journal of the Korean Ceramic Society, volume 35, issue 5, 1998, Pages 499~504
Abstract
ZnO varistors having a composition of 98.0 mol% ZnO 1.0 mol%
0.5 mol%
were prepared by the Pechini process and the sintering behavior and electrical characteristics were studied. ZnO varis-색 powder with
mean diameter and narow particle size distribution was obtained using the Pechni pro-cess. Typical intermediate stage grain growth of liquid phase sintering was observed by sintering at
At this temperature ZnO varistors having uniform grain size and Bi-rich liquid phase distributed uniformly along grain boundaries were prepared. The nonlinear coefficients of the ZnO varistors were in the range of 40-60 The breakdown voltages of the varistors were nearly inversely propeortional to the grain size which reflects that ZnO varistors prepared by the Pechini process have uniform distribution of Bi-rich liquid phase along grain boundaries It is believed that the microstructures of ZnO varistors can be controlled effectively by using the Pechini process which makes the control of the electrical properties of ZnO varistors possible.
13
Silicidation of Co/M/(100) Si bilayer Structures
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Journal of the Korean Ceramic Society, volume 35, issue 5, 1998, Pages 505~511
Abstract
The silicide formation mechanisms of Co/Hf and Co/Nb bilayer on (100) Si have been investigated. We ob-served that crystallographic orientationso f the 500
formed cobalt silcides were different each other with the varying intermediate layers. Epitaxial and non-epitaxial CoSi2 formed simultaneously in Co/Hf/(100Si. While only non-epitaxial CoSi2 formed in Co/Nb/(100) Si. The reason why the crystallographic orientation of CpSi2 is different for those two systems seemed to be relate to the formation and decomposition of stable reaction barriers at high temperature. The stable reaction barrier formed at high temperature could control the uniform diffusion of Co atoms which enables epitaxial growth of CoSi2
14
Strain Properties of Sn-Substituted PLZT(7.5/70/30) for Application of Ceramic Actuator
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Journal of the Korean Ceramic Society, volume 35, issue 5, 1998, Pages 512~520
Abstract
PLZT(7.5/70/30) was initially a cubic phase having diffuse phase transition at high temperatures. Sn-sub-stitution for PLZT(7.5/70/30) underwent an irreversible phase transition from cubic to rhom-bohedral structure. However PLZTS(7.5/70/30/y=5 & 10) could be reversibly switched from paraelectric to ferroelectric phase under electric field without showing a significant change in crystal structure. With in-creasing the amount of Sn-substitution the P-E behaviors of the PLZTS became more antiferroelectric which was similar to the effect of La-substitution of PLZT. Our study may suggest that Sn-substitution ef-fectively weakens a formation of long-range order between polar Ti-or Zr- containing octahedra which greatly affects strain properties.
15
Electrical Conductivity of YO
-TaO
-MgO Based Fluorite Phase
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Journal of the Korean Ceramic Society, volume 35, issue 5, 1998, Pages 521~527
Abstract
Electrical conductivity of fluorite structure phases in the {{{{ {Y }_{0.8 } }}{{{{ { Ta}_{ 0.2} {O }_{1.7 }-MgO }} system has been studied. Electrical conductivity of 8mol% MgO doped {{{{ {Y }_{0.8 } }} {{{{ {Ta }_{0.2 } {O }_{1.7 } }} fluorite phase was lower than that of the undoped {{{{ {Y }_{0.8 } }}{{{{ {Ta }_{0.2 } {O }_{1.7 } }} When {{{{ { P}_{H2O } }} was increased electrical conductivity of {{{{ {Y }_{0.8 } }}{{{{ {Ta }_{0.2 } {O }_{1.7 } }} increased linealy with {{{{ { P}`_{H2O } ^{ {1 } over {2 } } }} The {{{{ {Y }_{0.8 } }}{{{{ {Ta }_{0.2 } {O }_{1.7 } }} fluorite phase exhibited higher electrical conductivity in wet atmosphere than in dry atmosphere. The identical trend was observed from the 8mol% MgO doped {{{{ {Y }_{0.8 } }}{{{{ {Ta }_{0.2 } {O }_{1.7 } }} fluorite phase.