• Journal of the Korean Ceramic Society
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• v.31 no.8
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• pp.879-885
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• 1994

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$0^{\circ}C$ for 1 hour was 0.19 ${\mu}{\textrm}{m}$. The optimum sintering temperature and holding time are 130$0^{\circ}C$ 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.

• Journal of the Korean Ceramic Society
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• v.29 no.12
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• pp.997-1003
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• 1992

Ultra-fine hydroxyapatite powders were synthesized by the hydrothermal reaction of Ca(OH)2 suspension or Ca(NO3)2$.$4H2O solution with (NH4)2HPO4 solution, and the powders were characterized for each synthetic condition. Crystalline hydroxyapatite powders have average grain size of less than 50 nm. By increasing the reaction pressure, the crystallinity was improved, and the crystals were preferentially growing along c-axis. When Ca(NO3)2$.$4H2O of high solubility was used, hydroxyapatite of single phase was produced. However when Ca(OH)2 of low solubility was used more than 0.334 mol/ι, unreacted Ca(OH)2 remained. Diffraction spot patterns of transmission electron microscope show that powders synthesized by the hydrothermal reaction were composed of single crystals of hexagonal phase.

• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.903-906
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• 2002

Nanosized $Mn_xFe_2O_4$ powders were prepared in ethylene glycol solution under mild temperature and pressure conditions by precipitation from metal nitrates with aqueous potassium hydroxide. The average size and distribution of the synthesized $Mn_xFe_2O_4$ powders was about 20 nm and broad, respectively. The phase of synthesized particles was crystalline reacted at 200${\circ}C$ for 6h. The magnetic properties of the synthesized $Mn_xFe_2O_4$ powders were about 35-60 (emu/g) with superparamagnetic character.

• Journal of Powder Materials
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• v.9 no.6
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• pp.433-440
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• 2002

Synthesis and compaction of Al-base nano powders by pulsed discharge method were investigated. The aluminum based powders with 50 to 200 nm of diameter were produced by pulsed wire evaporation method. The powders were covered with very thin oxide layer. The perspective process for the compaction and sintering of nanostructured metal-based materials stable in a wide temperature range can be seen in the densification of nano-sized metal powders with uniformly distributed hard ceramic particles. The promising approach lies in utilization of natural uniform mixtures of metal and ceramic phases, e.g. partially oxidized metal powders as fabricated in our synthesis method. Their particles consist of metal grains coated with oxide films. To construct a metal-matrix material from such powder, it is necessary to destroy the hard oxide coatings of particles during the compaction process. This goal was realized in our experiments with intensive magnetic pulsed compaction of aluminum nanopowders passivated in air.

• Journal of the Korean Ceramic Society
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• v.31 no.11
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• pp.1283-1292
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• 1994

Ultra-fine $\beta$-SiC powders were fabricated by self-propagating high temperature synthesis process (SHS) using chemical furnace. The dependences of the C powders with different surface areas, the molar ratios of C/Si, the weight ratios of chemical fuel content, and pellet diameter-size on synthesis were investigated. Compositional and structural characterization of these powders was carried out by scanning electron micrograph and X-ray diffraction. The $\beta$-SiC powders which had C/Si mole ratio=1.05, 3 times chemical fuel contents, and pellet diameter=20 mm were optimum for synthesis efficiency. By optimizing process-variables, it is possible to fabricate $\beta$-SiC powders which have little secondary phases ($\alpha$-SiC).

• Journal of the Korean Ceramic Society
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• v.25 no.3
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• pp.284-292
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• 1988

Alumina-zirconia composite powders for the purpose of improving fracture toughness and thermal shock resistance of alumina were prepared by the emulsion-kerosene drying method. The average particle size of composite powders was less then 1 $\mu\textrm{m}$ and their shapes were spherical. It was shown that the average particle size of composite powders decreased with the concentration of metal-salt in solution and the amount of span 80 added when preparing emulsions. The structure of all zirconia in composite powders heat-treated at 1200$^{\circ}C$ was a tetragonal form at room temperature. This result implied that fine zirconia particles were homogeneously dispersed in the alumina matrix.

• Journal of the Korean Ceramic Society
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• v.30 no.8
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• pp.651-656
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• 1993

Granulated Y-TZP powders were coated by using Sol-Gel method and the coating effect of Al2O3 on the isothermal phase transformation in Al2O3 coated Y-TZP powders was investigated. During aging, tetragonal phase in Y-TZP powder were isothermally transformed to monoclinic, but the tetragonal phase in Al2O3 coated Y-TZP powders was continuously retained in spite of long aging. It can be considered that the improvement of thermal stability of tetragonal phase in Al2O3 coated Y-TZP powders may be due to the increase of constraint effect near tetragonal phase, and the suppression of surface transformation by obstructing the reaction between the surface of Y-TZP and H2O.

• Journal of the Korean Ceramic Society
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• v.31 no.1
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• pp.31-38
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• 1994

To overcome the demerit of conventional forming method, new forming method, pressureless powder packing forming method, was investigated. This technique is performed by powder packing followed by the infiltration of binder solution. Various alumina powders were used as starting materials and the powders showing good packing condition through powder packing experiment were chosen. The green densities prepared by this new forming method with these powders were lower than those of specimens by pressing method, but, nearly same density was obtained in case of green body prepared with the powders having high packing density. The distribution of binder in a green body was homogeneous and it was possible to a complex shape form by this forming method.

• Journal of the Korean Ceramic Society
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• v.27 no.8
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• pp.1064-1070
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• 1990

ZrO2 fine powders were prepared by hydrolysis, adding 0.1, 0.2, 0.3, 0.4, 0.5, 0.6mol/1H2O/ethanol to 0.1 mol/l Zr(OC3H7)4/ethanol. When hydrolized by adding 0.1mol/l Zr(OC3H7)4/ethanol to 0.1, 0.2mol/l H2O/ethanol., spherical monodispersed ZrO2 fine powders were obtained. And in this condition average sizes were about 0.5, 0.3${\mu}{\textrm}{m}$, respectively. The more H2O/ethanol concentration increased, the more the particle size decreased and the particles were agglomerated strongly. Prepared powders were amorphous and hydrates. The calcined powders with 43$0^{\circ}C$ and 100$0^{\circ}C$ were showed tetragonal and monoclinic phase, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.799-802
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• 2005

The effects of binder content and ceramic powder content on the water absorption, carbonation depth and cl- penetration depth of polymer-modified pastes using redispersible polymer powders and ceramic powder are examined. As a result, the water absorption .of the polymer-modified pastes using redispersible polymer powders tend to decrease with increasing binder content and ceramic powder content. Regardless of the type of redispersible polymer powder, the carbonation depth and cl- penetration depth of the polymer-modified pastes with ceramic powder tend to decrease with increasing binder content and ceramic powder content.