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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 33, Issue 12 - Dec 1996
Volume 33, Issue 11 - Nov 1996
Volume 33, Issue 10 - Oct 1996
Volume 33, Issue 9 - Sep 1996
Volume 33, Issue 8 - Aug 1996
Volume 33, Issue 7 - Jul 1996
Volume 33, Issue 6 - Jun 1996
Volume 33, Issue 5 - May 1996
Volume 33, Issue 4 - Apr 1996
Volume 33, Issue 3 - Mar 1996
Volume 33, Issue 2 - Feb 1996
Volume 33, Issue 1 - Jan 1996
Volume 2, Issue 3 - 00 1996
Volume 2, Issue 2 - 00 1996
Volume 2, Issue 1 - 00 1996
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Tribological Properties of Raction-Bonded SiC-Graphite Composites
Journal of the Korean Ceramic Society, volume 33, issue 5, 1996, Pages 479~484
The tribological properties of ceramics are very important in the application to engineering ceramic parts such as mechanical seal slurry valve disc and so on. In this study the effect of graphite addition on the mechanical and tribological properties of RBSC/graphite composites were investigated. The composites were prepared by adding graphite powder to the mixture of SiC powder metallic siliconcarbon black and alumina. Bending strength water absorption friction coefficient the amount of worn out material at a certain time and maximum surface roughness(Rmax) of the prepared composites were measured and crystalline phases were examined with XRD. The composite containing 5 vol% graphite powder showed improved bending strength due to high green density and decreased friction coefficient and wear resistance. The friction coefficient and the wear resistance of the composite were increased by adding graphite powder up to 10 vol% They decreased however as increasing the amount of graphite powder more that 10vol% There was no linear relationship between the tribological properties and bending strength of the composites.
Low Pressure Synthesis of Silica Aerogels by Supercritical Drying
Journal of the Korean Ceramic Society, volume 33, issue 5, 1996, Pages 485~494
Silica Aerogels with the density and porosity of 0.1g/cm3 and 96% were synthesized by two different supercri-tical drying processes (i.e additional solvent and intial pressure methods) Isoptopanol was chosen as sol-gel and supercritical drying solvents in order to synthesize aerogels at the lower temperature and pressure because the critical values of isopropanol are lower than those of methanol and ethanol commonly used. The P-V-T relationship of isopropanol was experimentally described for optimizing supercritical drying conditions such as the amount of extra solvent and supercritical drying temperature and pressure. In the addional solvent method monolithic and transparent aerogels were obtained by supercritical drying at 25
and 900 psing after 40% of the reactor volume was filled with isopropanol. Crack-free aerogels were synthesized at 25
and 1100~1200 psig by the initial pressure method with an intial nitrogen gas pressure of 400 psig and the isopropanol amount of 5% of the reactor volume.
Preparation of Monodispersed Colloidal Particles of Yttrium Compound by Homogeneous Precipitation. I.Effect of
Journal of the Korean Ceramic Society, volume 33, issue 5, 1996, Pages 495~506
Monodispersed colloidaly yttria(Y2O3) can be used in a variety of applications such as phosphors. IR transparent materials and fine ceramics. For preparing monodispersed yttria homogeneous precipitation has been regarded as a fovorable method that is monodispersed yttria can be obtained through calcining monodispersed colloidal compound of yttrium (eg:Y(OH)CO3.nH2O)which can be prepared by homogeneous precipitation with urea. It is however still required to find out the quantitative effects of important variables of precipitation such as concentration of yttrium and urea reaction temperature and initial pH of reactant even though homogeneous precipitation of Y3+ with urea has been studied extensively. Among the effects of these variables we investiga-ted 1) the effect of yttrium concentration on the shape and size of precipitate and the reation rate 2) range of yttrium concentration required to make monodispersed colloidal particles 3) the reason for limited concentra-tion range of yttrium and 4) the effect of ultrasonic radiation on the limited concentration.
Structural Dependence of Nonlinear Optical Properties in
Journal of the Korean Ceramic Society, volume 33, issue 5, 1996, Pages 507~513
Nonlinear optical properties of TeO2-PbO-GeO2 glasses were investigated and their correlation with struc-tural modification was investigated. Third-order nonlinear susceptibility
, ranged between 5.0
10-13 esu and 10.7
10-13 esu which are approximately 20-40 times larger than that of silica glass. The glass with a composition of 85(80TeO2-20PbO)-15GeO2(mol%) seemed to provide an optimum compromise between
and the stability against crystallization. Analyses of the Raman spectra suggested that these glasses are mainly composed of [TeO4] tbp, [TeO3]tp and [GeO4] tetrahedral structural units. It was concluded that the positive contribution of Pb2+ with high polarizability to
in TeO2-PbO glasses overwhelmed the negative influence due to the structural modification of [TeO4]tbplongrightarrow[TeO3]tp. On the other hand addition of GeO2 in TeO2-PbO-GeO2 glasses resulted in the decrease of
values. This behavior was attributed to the formation of [GeO4] polyhedra at the expense of [TeOn] polyhedra and Pb2+ ions which normally sowed a higher contribu-tion to
than [GeO4] polyhedra.
Preparation of ATO Thin Films by DC Magnetron Sputtering (II)Electrical Properties
Journal of the Korean Ceramic Society, volume 33, issue 5, 1996, Pages 514~518
Sb doped SnO2(ATO: Antinomy doped Tin Oxide) thin films were prepared by a DC magnetron spttuering method using an oxide target and the electrical characteristics of ATO films were investigated. The experimen-tal conditions are as follows :Ar flow rate ; 0~100 sccm deposition tempera-ture ; 250~40
DC sputter powder ; 150~550W and sputteing pressure ; 2~7 mTorr, The thickness of depositied ATO films were 600
ranges. The resistivity of ATO films was decreased due to the increase of the crystallinity of ATO films with deposition temperature. The decrease of carrier concentration of films with the increase of oxygen flow rate and working pressure is responsible for the increase of resistivity. Increasing of sputtering power raised the resistivity of films by decreasing the carrier mobility.
Studies on the Properties of High Performance and High Strength Cement Mortar Using Meta Kaolin and Silica Fume
Journal of the Korean Ceramic Society, volume 33, issue 5, 1996, Pages 519~523
Calcium hydroxide produced by cement hydration decreases the durability and the compressive strength of cement mortars. Pozzolanic property of meta kaolin and silica fume allows to avoid this drawback. Calcium hydroxide consumption according to pozzolanic raction is evaluated by Fourier differential thermal analysis. Particulary the properties of high performance and high strength of cement mortar containing above 10% meta kaolin and silica fume were resulted in the pozzolanic activity
Fabrication of Electrically Conductive
Journal of the Korean Ceramic Society, volume 33, issue 5, 1996, Pages 524~530
TiB2-BN-AlN composite was fabricated with the addition of 0~12 wt% WC by HP-sintering. Their sinterability. microstructure mechanical and electrical properties were studied as a function of the WC content. The addition of WC up to 12 wt% increased the flexural strength and decreased electrical resistivity as compared with those of the TiB2-BN-AlN composites. The electrical resistivity of TiB2-BN-AlN composite with 4.3 wt% WC was 640
-cm. It was found that the TiB2-BN-AlN composites with WC addition more than 4wt% was suitable for the application to the Al evaporation boat.
Preparation and Photoluminescence of Mn-Doped
Journal of the Korean Ceramic Society, volume 33, issue 5, 1996, Pages 531~535
ZnGa2O4 and Mn-doped ZnGa2O4 were synthesized using the state reaction method to investigate their photoluminescence characteristics depending on Mn concentration. Under 254nm excitation, ZnGa2O4 exhibited a broad-band emission extending from 330 nm to 610 nm peaking at 450nm. On the other hand Mn-doped ZnGa2O4 showed a new strong narrow-band emission peaking at 504 nm and maximum intensity at the doping concentration of 0.006 mole Mn.
Microstructure and Mechanical Properties of TiC-Ni/Al Composites by the Reaction-Bonding Method
Journal of the Korean Ceramic Society, volume 33, issue 5, 1996, Pages 536~546
The TiC-Ni/Al reaction-bonding composites were prepared by the infiltration of Ni/Al melt into the TiC preforms. The microstructure the reaction composition crystalline phase and the mechanical properties of the composites were investigated. During the reaction-bonding Ni/Al mixture had a good wettability and per-meability with TiC preform and pore-free and fully dense sintered bodies were produced. In the case of the Ni/Al atomic ratio of 0.3 and 0.5 TiC raw particle shape was changed to irregular particles because of the decomposition in the liquid matrix and its phenomena was more distinguished in the Al-rich liquid matrix. With increasing more than 1 of the Ni/Al atomic ratio the sample of TiC grain shape was changed from spherical to palatelet particles. Also with increasing the atomic ratio of Ni/Al bending strength and fracture spherical to palatelet particles. Also with increasing the atomic ratio of Ni/Al bending strength and fracture toughness were increased and its maximum value was 1073 MPa and 11 MPa.m1/2 respectively.
Pore Characteristics of Porous Alumina Ceramics Fabricated from Boehmite Hydrosol and Alumina Particles
Journal of the Korean Ceramic Society, volume 33, issue 5, 1996, Pages 547~555
Porous alumina ceramics were fabricated by pseudo-boehmite phydosol-gel process within/without commercial
-alumina particles average 1 and 40 micron respectively. The pore characteristics of fired specimens were studied by the measurement of bulk density total porosity thyermal analysis pore volume pore distribution BET area XRD and SEM. with increasing of firing temperature pore volume and BET surface area were decreased and the average pore size was increased to approximately 146
by de-watering of [OH] and formation of
-alumina. The fired relative density of the alumina-dispersed specimen with average 1 micron particle was increased with the amounts of dispersed particle by bimodal packing theory which is compared to the ones of specimen including of average 40 micron particle. It was confirmed that the percola-tion threshold in porous ceramics with coarser particle (40 micron) has formed between the transformed-alumina from hydrogel and dispersed-alumina of above 50 vol% particle and the total porosity was increased at the threshold point above.
Effect of PbTiO3 Concentration on the Properties of
Relaxor Ferroelectrics -II. Phase Transition and Electric-field-induced Strains-
Journal of the Korean Ceramic Society, volume 33, issue 5, 1996, Pages 556~562
In order to understand the electrostrictive behavior of Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) solid solutions the dielectric constants the electric-field-induced strains and the pyroelectric coefficients of (1-x)PMN-xPT (x=0.1-0.4) were investigated in the temperature range -50~20
. For x=0.1~0.35 where the phase transi-tion is diffusive the strain has a maxima at the temperature of maximum pyroelectric coefficient (depolrizing temperature) rather than the temperature of maximum dielectric constant. For x=0.4 where the phase transition is relatively sharp the strain decreases monotonically as the temperature increases. Relationships among the above experimental results are discussed.
Fine Powder Synthesis and It첨s Sintering Characteristics of CaO-Stabilized
by Coprecipitation Method
Journal of the Korean Ceramic Society, volume 33, issue 5, 1996, Pages 563~571
In order to fabricate solid electrolyte CaO-stabilized ZrO2 of high density sintered body economically 13 mol% CaO-stabilized ZrO2 powders were synthesized by the coprecipitation method. The characteristics and sintering behavior of fine powder were investigated. The precipitates has the specific surface area of 193 m2/g and apperaed to be fine and spherical primary particles with a size of approximately 5nm. The crystalliza-tion temperture of CaO-stabilized ZrO2 was 462
. The tetragonal phase was stable in the low calcining tempe-rature regions and the cubic zirconia solid solution was formed from above 120
through an intermediate stage of formation of CaZrO3 By introducing fine powders washed with alcohol and ball-milling process after calcination the sintered body was possible to attain the value of above 92% of the theoretical density at low temperature of 120
C-V Characteristics of Oxidized Porous Silicon
Journal of the Korean Ceramic Society, volume 33, issue 5, 1996, Pages 572~582
The porous silicon was prepared in the condition of 70mA/cm2 and 5.10 sec and then oxidized at 800~110
MOS(Metal Oxide Semiconductor) structure was prepared by Al electrode deposition and analyzed by C-V (Capacitance-Voltage) characteristics. Dielectric constant of oxidized porous silicon was large in the case of low temperature (800, 90
) and short time(20-30min) oxidation and was nearly the same as thermal SiO2 3.9 in the case of high temperature (110
) and long time (above 60 min) It is though to be caused byunoxidized silicon in oxidized porous silicon film and capacitance increase due to surface area increment effect,
Analysis of Bridging Stress Effect of Polycrystalline aluminas Using Double Cantilever Beam Method
Journal of the Korean Ceramic Society, volume 33, issue 5, 1996, Pages 583~589
In this study a new analytical model which can describe the relationship between the bridging stress and microstructure has beenproposed in order to investigate the microstructural effect on the R-curve behavior in polycrystalline aluminas since the R-curve can be derived via the bridging stress function. In the currently developed model function the distribution of grain size is considered as a microstructural factor in modeling of bridging stress function and thus the bridging stress function including three constants PM, n, and Cx, can be established analytically and quantitatively. The results indicate that the n value is closely related to the grain size distribution thereby providing a reliability of the current model for the bridging stress analysis. Thus this model which explains the correlation of the bridging stress distribution and microstructual parame-ters is useful for the systematic interpretation of microfracture mechanism including the R-curve behavior in polycrystalline aluminas.
Analysis of Bridging Stress Effect of Polycrystalline Aluminas Using Double Cantilever Beam Method II. Development of Double Cantilever Beam Method Considering Bridging Effect
Journal of the Korean Ceramic Society, volume 33, issue 5, 1996, Pages 590~601
This study aims at developing the double cantilever beam (DCB) method in order to calculate the bridging stress distribution in polycrystalline aluminas with different grain sizes. In the already existing DCB methods the measured crack opening displacement (COD) in coarse-grained aluminas deviates generally from the calcula-ted one because of the grain-interface bridging in the crack wake. In the current DBC method developed in the present study the effect of the bridging stress was considered in the DCB analysis. whereas the only effect of applied point-loading at the end of DCB specimen was taken into account in the existing DCB analysis The crack closure due to bridging stress was calculated using the power-law relation and the theoretical model developed in Part I of the present paper as bridging stress function and then compared analytically. The limitations of the current DCB methods such as specimen dimensions applied loads and elastic modulus were discussed in detail to provide a reliability of the newly developed DCB analysis for the bridging stress distribu-tion in polycrystalline aluminas.
Analysis of bridging Stress Effect of Polycrystlline Aluminas Using Double Cantilever Beam Method
Journal of the Korean Ceramic Society, volume 33, issue 5, 1996, Pages 602~615
The purpose of the present study is to investigate the microstructural effect on the R-curve behavior in three aluminas with different grain size distributions by analyzing the bridging stress distribution. The crack opening displacement (COD) according to the distance behind the stationary crack tip was measured using an in situ SEM fracture method. The measured COD values in the fine-grained alumina agreed well with Wiederhorn's sollution while they deviated from Wiederhorn's solution in the two coarse-grained aluminas because of the increase of the crack closure due to the grain interface bridging in the crack wake. A numerical fitting procedure was conducted by the introduction of the power-law relation and the current theoretical model together with the measured COD's in order to obtain the bridging stress distribution. The results indicated that the bridging stress function and the R-curve computed by the current model were consistent with those computed by the power-law relation providing a reliable evidence for the bridging stress analysis of the current model. The strain-softening exponent in the power-law relation n, was calculated to be in the range from 2 to 3 and was closely related to the grain size distribution. Thus it was concluded from the current theoretical model that the grain size distribution affected greatly the bridging stress distribution thereby resulting in the quantitative analysis of microfracture of polycrystalline aluminas through correlating the local-fracture-cont-rolling microstructure.