• Membrane Journal
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• v.32 no.5
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• pp.265-274
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• 2022

Separation of oily wastewater, which is a byproduct of various industries such as petroleum refineries, is essential to not exceed the tolerance limit of wastewater streams. Ceramic membranes show potential in oily wastewater separation, due to their excellent oil removal efficiency, good chemical, thermal, and mechanical stability, and simple operation. However, widespread application of ceramic membranes is limited due to high material cost of alumina, silica, and other ceramic based materials used to fabricate them. Recent efforts to reduce material cost have been made, using fly ash and clay. This review examines the fabrication and efficiency of ceramic membranes in oily wastewater separation according to material: silica, alumina, and waste ash.

• Journal of the Korean Ceramic Society
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• v.35 no.7
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• pp.691-698
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• 1998

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.247-253
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• 2019

3D printing technology has attracted considerable attention because of its potential to fabricate the intricate design of ceramic products. In this study, ceramic 3D nozzle printing was introduced to manufacture complex alumina products with a ceramic pigment. The alumina paste was formulated by incorporating an elastomer to impart viscoelastic properties. Viscoelastic pastes play an essential role in ceramic 3D nozzle printing. The effects of the viscoelastic properties of the ceramic pastes on their printability were assessed using comprehensive rheological analysis, and various shapes were printed. As a result, the paste with a high yield stress showed better printability. In addition, a ceramic pigment was added to the developed pastes to increase the aesthetics of the printed ceramic structure. The printed ceramic parts were sintered in air at 1300 ℃. The stability of the ceramic pigment was confirmed even after high-temperature sintering.

• Journal of the Korean Ceramic Society
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• v.54 no.3
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• pp.257-260
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• 2017

In this work, we present a facile one-pot synthesis of a multilayer-structured platy alumina/few-layer graphene nanocomposite by planetary milling and hot pressing. The sintered composites have electrical conductivity exhibiting percolation behavior (threshold ~ 0.75 vol.%), which is much lower than graphene oxide/ceramic composites (> 3.0 vol.%). The conductivity data are well-described by the percolation theory, and the fitted exponent values are estimated to be 1.65 and 0.93 for t and q, respectively. The t and q values show conduction mechanisms intermediate between 2D- and 3D, which originates from quantum tunneling between nearest neighbored graphenes.

• Journal of the Korean Ceramic Society
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• v.51 no.5
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• pp.406-412
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• 2014

In this study, flat-tubular-type alumina filters were manufactured using alumina powder of two sizes ($2.4{\mu}m$ ALM-44 and $0.4{\mu}m$ AP 400) by an extrusion process. The manufactured alumina filter was sintered at $1200-1600^{\circ}C$ for 1 h. As particle size increased, the largest pore size, average pore size and porosity increased; but density and linear shrinkage decreased. The alumina filter fabricated using ALM-44 powder sintered at $1500^{\circ}C$ was confirmed as the best water treatment filter after investigation of the bending strength, water permeability and impurity-removal efficiency of the experimental filters. This flat-tubular-type alumina filter is expected to be useful not only for direct water treatment, but also for use as a support filter during coating processes, to control pore size.

• Journal of the Korean Ceramic Society
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• v.54 no.4
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• pp.331-339
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• 2017

Porous alumina-based ceramics are of special interest due to their outstanding mechanical properties and their thermal and chemical stability. Nevertheless, the high electrical resistance of alumina-based ceramics, due to the generation of static electricity, leads to difficulty in applying a vacuum chuck in the semi-conductor process. Therefore, development of alumina-based ceramics for applications with vacuum chucks aims to have primary properties of low electrical resistance and high air permeability. In this study, we tailored the electrical resistance of porous alumina-based ceramics by adjusting the amount of $MnO_2$ (with $TiO_2$ fixed at an amount of 2 wt%) and by using coarse alumina powder for high air permeability. The characteristics of the specimens were studied using scanning electron microscopy, mercury porosimeter, capillary flow porosimetry, universal testing machine, X-ray diffraction and high-resistance meter.

• Journal of the Korean Ceramic Society
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• v.27 no.7
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• pp.925-933
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• 1990

The possible use of bioglass,, which is one of the surface active biomaterials, as implants materials has drawn great attention due to their ability to bond to human living tissue. In the present work, the investigation was carried out to find the bonding phenomena between alumina substrate and bioglass(45S5) or fluorine-containing bioglass(45S5$.$4F), and the properties of coated bioglass. The stable bonding between alumina and bioglass was formed when heat-treated at 1150$^{\circ}C$ for 120 minutes or at 1250$^{\circ}C$ for 30 minutes for the 45S5, and at 1150$^{\circ}C$ for 30 minutes for the 45S5$.$4F. When bioglass coated alumina was heat-treated, great amount of Al was diffused into bioglass from alumina substrate. More Al was diffused into fluorine-containing bioglass than into bioglass without fluorine. At early stage of heat-tretment, the diffused alumina content was increased with the square root of time and it was also increased with the thickness of coating layer and heat-treatment temperatures. The alumina content became constant after its saturation for longer heat-treatment time. Coated bioglasses were crystallized to Na2O$.$CaO$.$3SiO2 when heat-treated at lower temperature, and to CaO$.$SiO2 at higher temperature.

• Journal of the Korean Ceramic Society
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• v.49 no.2
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• pp.179-184
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• 2012

The size of various alumina ceramics used in semiconductor and display industry is required to increase with increase in wafer and panel size. In this research, large alumina ceramics were fabricated by uniaxial pressing, cold isostatic pressing and filter pressing with commercial powder and thereafter sintering at $1600^{\circ}C$ in gas furnace. The large alumina ceramics exhibited dense microstructure corresponding to 98.5% of theoretical density and 99.8% of high purity. The impurities and microstructural defects of the alumina were found to influence the resistance and dielectric properties. The volume resistances in these four aluminas were almost the same while the pure alumina was higher value. The dielectric constant, dielectric loss and dielectric strength of aluminas were placed within the range of 10.3~11.5, 0.018~0.036, and 10.1~12.4 kV/mm, respectively.

• Journal of the Korean Ceramic Society
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• v.31 no.4
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• pp.448-456
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• 1994

The reaction-sintered alumina and zirconia-alumina ceramics were fabricated from the Al/Al2O3 or Zl/ZrO2(Ca-PSZ) powder mixtures via the attrition milling. And the effects of the milling characteristics of used raw powders on reaction sintering were investigated. After attrition milling and isopressing at 400 MPa the Al/Al2O3 specimen was oxidated at 1200℃ for 8 hours followed by sintering at 1550℃ for 3 hours. Because mixed powders of flake-type Al with coarse alumina was much more effectively comminuted than the globular-type Al with coarse alumina powders, it's sintered body of more than 97% theoretical density was achived, but low contents of Al leads to relatively higher shrinkage of about 8%. And because coarse alumina particles was much more beneficial in cutting and reducing the ductile Al particles, using the coarse alumina powder was much more effective in reaction sintering. Fused Ca-PSZ powder was reaction sintered with Al at 1550℃ for 3 hours and low shrinkage ZrO2-Al2O3 composites were fabricated. But because Al/Ca-PSZ powder mixtures were not effectively milled the reaction sintering and densification was difficult. And the Ca ion in Ca-PSZ grains diffused into alumina grains during sintering so that the unstabilization of Ca-PSZ body was occured which gave the microcracks in the specimens.

• The Journal of Advanced Prosthodontics
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• v.9 no.2
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• pp.130-137
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• 2017

PURPOSE. The purpose of this study was to evaluate the effect of nano-structured alumina surface coating on shear bond strength between Y-TZP ceramic and various dual-cured resin cements. MATERIALS AND METHODS. A total of 90 disk-shaped zirconia specimens (HASS CO., Gangneung, Korea) were divided into three groups by surface treatment method: (1) airborne particle abrasion, (2) tribochemicalsilica coating, and (3) nano-structured alumina coating. Each group was categorized into three subgroups of ten specimens and bonded with three different types of dual-cured resin cements. After thermocycling, shear bond strength was measured and failure modes were observed through FE-SEM. Two-way ANOVA and the Tukey's HSD test were performed to determine the effects of surface treatment method and type of cement on bond strength (P<.05). To confirm the correlation of surface treatment and failure mode, the Chi-square test was used. RESULTS. Groups treated with the nano-structured alumina coating showed significantly higher shear bond strength compared to other groups treated with airborne particle abrasion or tribochemical silica coating. Clearfil SA Luting showed a significantly higher shear bond strength compared to RelyX ARC and RelyX Unicem. The cohesive failure mode was observed to be dominant in the groups treated with nano-structured alumina coating, while the adhesive failure mode was prevalent in the groups treated with either airborne particle abrasion or tribochemical silica coating. CONCLUSION. Nano-structured alumina coating is an effective zirconia surface treatment method for enhancing the bond strength between Y-TZP ceramic and various dual-cured resin cements.