• 멤브레인
• /
• 제32권5호
• /
• pp.265-274
• /
• 2022

석유 정제 시설 등에서 발생하는 함유폐수의 처리는 폐수의 유류 허용한계를 넘기지 않기 위해 중요한 공정이다. 세라믹 멤브레인은 유류 처리에서의 높은 효율, 내화학성, 내열성, 기계적 안정성, 그리고 단순한 작동 원리 등의 장점을 가지고 있어 함유폐수의 처리에 효과적이다. 그러나 세라믹 멤브레인은 원재료의 높은 가격 때문에 널리 사용되는 데에 한계가 있다. 최근에는 이를 해소하기 위해 플라이 애시나 점토를 사용하는 노력도 있었다. 이 리뷰는 세라믹 멤브레인의 효율과 제작을 실리콘, 알루미나, 그리고 폐석탄회의 재료로 나누었다.

• 한국세라믹학회지
• /
• 제35권7호
• /
• pp.691-698
• /
• 1998

• 한국산학기술학회논문지
• /
• 제20권12호
• /
• pp.247-253
• /
• 2019

최근 3D 프린팅 산업은 다양한 형상의 세라믹 부품을 간소화된 공정으로 제조 가능하여 많은 기대를 받고 있다. 본 연구에서는 세라믹 3D 프린팅을 통하여 알루미나(Alumina) 제품을 구현하기 위하여 3D 프린팅용 점탄성 페이스트(Paste)를 제조하였다. 점탄성 특성은 세라믹 3D 프린팅 공정에서 아주 중요한 역할을 한다. 노즐을 통한 세라믹 페이스트의 압출 시에는 흐름 특성을 가져야 하며, 인쇄되어 정확한 자리에 인쇄되어 안착한 후에는 고체처럼 작동하여 형상을 유지하여야 한다. 이러한 점탄성 특성을 부여하기 위하여 페이스트를 제조할 때 엘라스토머(Elastomer) 등의 첨가물을 첨가하였고, 이렇게 제조된 페이스트의 유변학적 특성을 분석한 결과 점탄성 특성을 보이는 것을 확인하였다. 하지만, 엘라스토머의 함량에 따라 점탄성 특성이 다름을 확인하여, 점탄성 특성의 각 지표가 실질적인 인쇄성에 어떠한 영향을 미치는지 확인하기 위하여 다양한 형태로 인쇄성 평가를 진행하였다. 인쇄성 평가 결과 높은 항복 응력을 가지는 페이스트가 인쇄성이 우수함을 확인하였다. 이렇게 개발된 알루미나 인쇄물의 심미성을 증가시키기 위하여 고온에서 소결시에도 안정적으로 발색효과가 있는 세라믹 안료를 제조된 페이스트에 혼합하여 1300 ℃에서 고온 소결을 진행하고, 소결 후 발색 효과를 확인하였다.

• 한국세라믹학회지
• /
• 제54권3호
• /
• pp.257-260
• /
• 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.

• 한국세라믹학회지
• /
• 제51권5호
• /
• pp.406-412
• /
• 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.

• 한국세라믹학회지
• /
• 제54권4호
• /
• pp.331-339
• /
• 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.

• 한국세라믹학회지
• /
• 제27권7호
• /
• pp.925-933
• /
• 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.

• 한국세라믹학회지
• /
• 제49권2호
• /
• pp.179-184
• /
• 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.

• 한국세라믹학회지
• /
• 제31권4호
• /
• pp.448-456
• /
• 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
• /
• 제9권2호
• /
• pp.130-137
• /
• 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.