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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 37, Issue 12 - Nov 2000
Volume 37, Issue 11 - Nov 2000
Volume 37, Issue 10 - Oct 2000
Volume 37, Issue 9 - Sep 2000
Volume 37, Issue 8 - Aug 2000
Volume 37, Issue 7 - Jul 2000
Volume 37, Issue 6 - Jun 2000
Volume 37, Issue 5 - May 2000
Volume 37, Issue 4 - Apr 2000
Volume 37, Issue 3 - Mar 2000
Volume 37, Issue 2 - Feb 2000
Volume 37, Issue 1 - Jan 2000
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(KLN) Thin Films by Heat Treatment Methods
Journal of the Korean Ceramic Society, volume 37, issue 8, 2000, Pages 731~738
KLN(K3Li2Nb5O15) has attracted a great deal of attention for their potential usefulness in piezoelectric, electro-optic, nonlinear optic, and pyroelectirc devices. Especially, the KLN single crystal has been studied in the field of optics and electronics. However it is hard to produce good quality single crystals due to the crack propagation during crystal growing. One of the solutions of this problem is prepartion of thin film. But the intensive study has not been conducted so far. In this study, after the KLN thin film were prepared by R.F. magnetron Sputtering method on SiO2/Si substrate, the post-annealing methods of RTA(rapid thermal annealin) and IPA(insitu post annealing) were employed. The deposition condition of KLN thin film was RF power(100 W), Working pressure(100 mtorr). The commonness of both RAT and IPA was that the higher were deposition and post annealing temperature, the higher was the intensity of XRD but the less surface roughness. The difference of post-annealing methods affected XRD phase and surface condition very much. And in IPA process, the influence of O2 had much effect on the formation of KLN phase.
Properties and Shape Control of YAG Powder Prepared by Hydrothermal Reaction
Journal of the Korean Ceramic Society, volume 37, issue 8, 2000, Pages 739~744
YAG(Y3Al5O12) as host material of YAG:Tb3+ was studied via hydrothermal synthesis of metal hydroxides. We changed the kind of mineralizer, the concentrations and process conditions in hydrothermal synthesis. As a result, we found, acicular YAG powders were obtained by the use of KOH as a mineralizer, the concentration of KOH affected the shape and size of YAG powder. Fine grained YAG were perpared by the use of NH4OH as a mineralizer and the concentration of NH4OH affected crystal phases but did not affect particle size. We could finally get the spherical looking YAG powder at 8 M NH4OH and at 35
for 12h. The average particle size was about 0.2
The Luminescence Properties of YAG:
Phosphor Prepared by Hydrothermal Synthesis
Journal of the Korean Ceramic Society, volume 37, issue 8, 2000, Pages 745~750
YAG:Tb3+ as green phosphor were studied for the development of low voltage FED phosphor prepared by hydrothermal synthesis. We changed the concentration of luminescence center ion Tb3+ in hydrothermal reaction of which conditions were at 8M NH4OH as mineralizer, at 35
for 12hrs. As results, we could finally get the YAG:Tb3+ (Y3-xTbxAl5O12) powder of which particle size was about 0.2~1.0
. The excitation spectra and the green emitted spectra of YAG:Tb3+ phosphor powder were observed. When we doped 0.25 mol Tb to YAG, we could observe the maximum cathodoluminescence from YAG:Tb3+ phosphor and the chromaticity coordinate of the phosphor was shown x=0.35, y=0.56 in CIE1931 diagram.
Fluidity Changes of Cement Paste added Superplasticizer and Inorganic Fine Powders for Cement Admixture
Journal of the Korean Ceramic Society, volume 37, issue 8, 2000, Pages 751~759
Effects of the dosage change, from 0 to 2.0 wt% based on cement weight, of naphthalenic (NSF) and polycarboxylic(NT-2) superplasticizers, on the fluidity of cement paste substituted by 10 wt% II-anhydrite and fly ash respectively as well as II-anhydrite and fly ash itself were investigated. Dispersion properties between particles in suspension were investigated by zeta potential test. Initial fluidity and slump loss in the paste system were observed through mini-slump and apparent viscosity changes with elapsed time. Zeta potential on the particle surface was a tendency to increase according to increasing of NSF dosage. Especially, zeta potential of fly ash has the highest value among all particles equivalent to NSF dosage. In the fluidity of cement paste substituted by inorganic particles, the specimen with substitution of 10 wt% II-anhydrite and fly ash for cement was more effective than cement itself to improve initial fluidity and retain stable fluidity of cement paste. In addition, effect of NT-2 and NSF to improve the fluidity of cement paste, addition of 1.0 wt% NT-2 was more effective than 1.5wt% NSF.
The Emulsification of Silane as Water REpellent for Concrete
Journal of the Korean Ceramic Society, volume 37, issue 8, 2000, Pages 760~767
Recently, the protection of construction is demanded with environmental pollution. These protect modes are use of concrete admixture, coat of protective polymer and impregnate of surface with chemicals etc. The most widely used impregnation is economical and effective. The define of Impregnation for construction protect is reacted in and consolidated substrate after absorbed. The impregnation agents are Polyesters, Acrylic monomers, Epoxy and Silicone derivatives. Commonly, because the Silane has good water repellency and environmental advantages that it widely used to water proofing agents, dampproofing agents and absorption reducer for concrete of bridges. When application of Silane, it occurs pollution and harmfulness as included organic solvent. The manufactures have tired to emulsification of Silane for the reducing of the defects. The Silane emulsion is vary unstable and does not stored long periods, and it is diminished in good properties with internal reaction. In this study we tried to emulsification of Silane for effectiveness improvement and reduce pollution and hazard and discussed properties variation of emulsion. The Silane emulsions are achieved emulsifying with W/O and O/W type surfactants. It used 0.24% PVA as protective colloid and stable phase is creamy. The creamy Silane emulsion performance as the penetration depth and water absorption rate are above 4 mm and below 0.1. It stable about 6 month at room temperature.
Synthesis of Alinite Cement Using Combustion Ash of Solid Wastes
Journal of the Korean Ceramic Society, volume 37, issue 8, 2000, Pages 768~773
Alnite clinker, which is based on CaO-SiO2-CaCl2 system, was synthesized by recycling Cl-containing waste, and its hydraulic properties were onvestigated. Alinite coinkers with two different chemical compositions were burned for 10∼30 minutes in the range of temperature, 1350∼1450
. The microstructures of those clinkers were characterized by powder X-ray diiffracuion analysis, optical microscope, and scanning electronic microscope and heat of hydration of alinite cements which was measured in order to investigate hydraulic properties. X-ray analysis shwoed that f-CaO in both clinkers with different compositions significantly was decreased with transforming C2S(belite) to C3S(alite). From the results of microscopy and scanning electron microscopy(SEM), crystal of synthesized alite(C3S) was larger and better crystallinity than that of ordinary portland cement.
Synthesis and Characterization of High Luminance
Journal of the Korean Ceramic Society, volume 37, issue 8, 2000, Pages 774~780
In order to improve luminescence prperty of phosphors, we have synthesized Zn2SiO4:Mn phosphors by a new chemical synthetic route, i.e., the homogeneous precipitation method. This method has featured that the formation of phosphoris completed at relatively low temperature of 105
and the particle morphology exhibits spherical shape to be well-dispersed and uniform size. At all the Mn concentration explored, phosphors prepared by this method have exhibited the improved emission intensities. In particular, the emission intensities of phosphors with Mn doping contents between 1 at% and 3.5 at% were higher about 40% than that of commercial phosphor. On the other hand, the decay time has been decreased from 23 ms to 11 ms with increasing Mn concentration. In addition, the phosphor composition containing 3 at% Mn has displayed the most saturated color.
Spectroscopic Properties of Er-doped Sulfide Fiber
Journal of the Korean Ceramic Society, volume 37, issue 8, 2000, Pages 781~786
An Er-doped sulfide fiber was drawn, and its spectroscopic properties were analyzed. Compositions of a 1000 ppmwt Er3+-doped core and an undoped clad were Ge30-Ga1-Asg-S61 and Ge30-As8-S62, in at.%, respectively. Refractive index of the core composition was approximately 0.01 high than that of the clad. In order to enhance the mechanical stability as well as to prevent infiltration of impurity ions such as OH-, an UV-curable polymer was used for the coating. The optical loss of a fiber formed directly from a polymer coated core rod without cladding was ∼15 dB/m at 1.06
. In the case of a fiber with core/clad structure, the optical loss was so high that the stimulated emission of erbium fluorescence was not evident. It is believed that presence of inhomogeneous core/clad interface and crystalline aggregates precipitated in the clad region were responsible for the high optical loss. On the other hand, fluorescence characteristics of Er3+ embedded in the core region were more or loss deteriorate compared to fiber preform, which is attributed to the redistribution of the Er ions along with the partial crystallization of the core glass during the fiberization process.
Superconducting Properties of Ge Substitution for the Bi Site in the 2212 Phase of Bi-Sr-Ca-Cu-O Superconductors
Journal of the Korean Ceramic Society, volume 37, issue 8, 2000, Pages 787~791
Samples with the nominal composition, Bi2-xGexSr2CaCu2O8＋
(x=0, 0.1, 0.2, 0.3, 0.4, 0.5) were prepared by the solid-state reaction method. We have studied the effect of substitution Ge for Bi and investigated the superconducting properties by changing oxygen content with Ge substitution. It was found that temperature difference, ΔK, between TCon and TCzero was considerably smaller in the samples prepared by the intermediate pressing method than that in the samples by the solid-state reaction method. We found the solubility limit of Ge to the 80 K single phase was around x=0.3. Within the solubility limit, lattice constant c decreased with the increase of x. In the region of the 80K single phase, the onset critical temperature TCon increased and excess oxygen content decreased with increase of x.
Mechanical Properties and Microstructures of Alumina Composites Reinforced with SiC Whiskers and TiC Particles
Journal of the Korean Ceramic Society, volume 37, issue 8, 2000, Pages 792~798
Alumina composites reinforced with SiC whiskers only or combinded with TiC particles were prepared by hot-pressing at 1850
for 1h. The mechanical properties and microstructures of composites were investigated in this study. By of addition either 20 vol% SiC whiskers or 20 vol% TiC particles, the flexural strength fo alumina was increased from 360 MPa to 650 MPa or 730 MPa, respectively, and the KIC was also increased from 3.5 MPa
m1/2 to 5.5MPa
m1/2 or 4.4MPa
m1/2, respectively. In the case of composites with 20 vol% SiC whiskers and 2 vol% TiC particles. The flexural strength and KIC showed relatively high value of 800 MPa and 5.3MPa
m1/2, respectively. The improvement of mechanical properties was considered to be due to both the smaller average grain size and the crack deflection.
Coulometric Titration Study on the Nonstoichiometry in Copper Doped Cobaltous Oxide ((
;Michael Schroeder;Manfred Martin;;
Journal of the Korean Ceramic Society, volume 37, issue 8, 2000, Pages 799~804
Coulometric titration experiments have been done for copper doped cobaltous oxide (Co1-xCux)1-
O with various dopant concentrations. We present the obtained experimental data and compare our results to those of previous thermogravimetric investigation. The experimental data are fitted by theoretical calculations based on various defect models. For this modeling, we considered different types fo major defects like copper in substitutional and interstitial lattice sites as well as copper vacancy. We also introduced the copper evaporation effect during titration experiment into our consideration.
/SiC Ceramic Composites Prepared by Polymer Pyrolysis
Journal of the Korean Ceramic Society, volume 37, issue 8, 2000, Pages 805~810
The formation, microstructure and properties of MoSi2/SiC ceramic composites by polymer pyrolysis were investigated for the application of heating element material. Polymethylsiloxanes were mixed with Si, SiC, MoSi2 as filler and ceramic composites prepared by pyrolysis in N2 atmosphere at 1320~145
were studied. Dimensional change, density variation and phases were analyzed and correlated to the resulting material properties. Microstructures of ceramic composite prepared by polymer pyrolysis were composed of MoSi2, SiC and silicon oxycarbide glass matrix. Depending on the pyrolysis conditions, ceramic composites with a density of 86~90 TD%, a fracture strength of 213~284 MPa, a thermal expansion coefficient of 4~7
10-6 were obtained. The electrical resistivity of the specimen decreased with increasing of temperature up to 50
Hydrothermal Reactivity of Various Classified Fly Ashes by Electrostatic Precipitator
;Estuo Sakai;Masaki Daimon;
Journal of the Korean Ceramic Society, volume 37, issue 8, 2000, Pages 811~816
This paper discussed hydrothermal reactivity of Ca(OH)2 and classified bituminous fly ashes which were collected at an electrostatic precipitator in coal fired power plant at 181
. The major products of hydrothermal reaction were tobermorite and hydrogrossularite because bituminous fly ashes contained Al2O3 content greater than 20 wt%. As increasing amount of Al2O3 content greater than 20 wt%. As increasing amount of Al2O3 in glass phases, formation of hydrogrossularite increased. Formation rate of crystalline tobermorite increased with content of finer particles, higher glass content and more Al2O3 in glass phases. There was a positive correlation between residue on 45
sieve and hydrothermal reactivity of fly ash up to 3 hours. The hydrothermal reactivity of fly ash at 181
for 12 hours was more affected by fineness than by glass content of fly ash.
Solid Electrolyte and
as Reference Electrode
Journal of the Korean Ceramic Society, volume 37, issue 8, 2000, Pages 817~823
A solid-state electrochemicall cell for sensing CO2 gas was fabricated using a solid electrolyte of Li2CO3-Li3PO4-Al2O3 mixture and a reference electrode of LiMn2O4. The e.m.f. (electromotive force) of sensor showed a good accordance with theoretical Nernst slope (n=2) for CO2 gas concentration range of 100-10000 ppm above 35
. The e.m.f. of sensor was constant regardless of oxygen partial pressure at the high temperature above 0.1 atm. It was, however, a little depended on oxygen partial pressure as the pressure decreased below 0.1 atm. The oxygen-dependency of our sensor gradually disappeared as the operating temperature increased. The sensing behavior of our CO2 sensor was affected by the presence of water vapor, but its effect was small comparing with other sensors.
Effect of Organic Additive Composition on Isostatic Thermocompression Behavior of Alumina Tapes
Journal of the Korean Ceramic Society, volume 37, issue 8, 2000, Pages 824~831
Alumina tapes, having various ratios of alumina to alumina＋binder＋plasticizer (a/(a＋o)) and binder to binder＋plasticizer(b/(b＋p)), were prepared by the tape casting method. The tapes were thermocompressed varying the thermocompression parameters such as temperature, pressure, and duration time. Among the parameters, the pressure was the most influential to the tape packing density. The packing density varied in two different ways depending on the a/(a＋o) ratio. For the tapes having low a/(a＋o) ratio, a saturation density was reached by applying very a low pressure of 1 MPa. For tapes with high a/(a＋o), on the contrary, the saturation density was obtained at a relatively high pressure. These different responses to the pressure are attributed to the fact that the rearrangement of alumina particles by the pressure becomes easy as an organic content in the tapes is high.