• 한국결정성장학회지
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• 제12권1호
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• pp.56-61
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• 2002

전남 영암산 이타점토 출발원료에 계면활성제를 사용하여 고농도의 slurry를 발포시킨 후 성형하여 다공질 세라믹스를 제조하였다. slurry에서의 계면활성제 농도변화는 다공질 세라믹스의 기공변화 및 물리적 특성을 제어하는 중요한 요인이었다. 발포용 slurry의 농도는 발포제인 계면활성제 농도가 증가할수록 발포력과 포말층의 안전도는 향상되었으나, 6.0 wt% 농도 이상에서는 계면활성제 양이 많아짐으로써 초기 slurry의 점도가 높아져 발포력이 좋지 못했다. 성형시편을 $1150^{\circ}C$와 $1200^{\circ}C$ 온도에서 소성하였고, 그 결과 부피비중은 약 0.9, 흡수율은 45%, 겉보기 기공율은 50%, 수축율은 14% 그리고 압축강도는 70kg/$\textrm{cm}^2$인 다공질 세라믹스를 제조할 수 있었다.

• 한국세라믹학회지
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• 제36권6호
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• pp.671-678
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• 1999

Porous ceramics were fabricated from pressureless powder packing forming method using mullite and cordierite powders granulate by spray drying. The bending strength and shrinkage of porous ceramics were increased and their porosity were decreased with increasing temperature. It showed homogeneous distribution of 2$\mu\textrm{m}$ intergranular pores of mullite at 1400$^{\circ}C$, 2.5$\mu\textrm{m}$ intergranular pores of cordierite at 1300$^{\circ}C$ respedtively. Above that temperature intragranular particles were sintered and sintering by intergranular necking was extremely proceeded. In the test of thermal shock resistance sudden decrease of bending strength to $\Delta$T was not shown because intergranular large pore prevented sudden crack propagation.

• 한국세라믹학회지
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• 제31권9호
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• pp.1044-1052
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• 1994

Tape casting technique was successfully applied to produce porous ceramics and multi-layered ceramics containing porous layers, where spherical hollow polymer particles were introduced as pore precursors. In the presence of extreme differences in density and size between Al2O3 and pore precursor particles, hindered settling was effective in preventing segregation of component particles and packing behavior of mixed powders was improved through bimodal packing. There were two transitions in packing behavior of mixed powders. The first transition took place at 40~50 vol% pore precursor addition, where majority of pores changed from close to open pore state. The other transition occured at 60~70 vol% pore precursor addition, where pore precursor particles formed a continuous network structure.

• 한국세라믹학회지
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• 제46권5호
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• pp.520-524
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• 2009

Porous self-bonded silicon carbide (SBSC) ceramics were fabricated at temperatures ranging from 1750 to $1850^{\circ}C$ using SiC, Si, C as starting materials and Al as an optional sintering additive. The effect of Al addition on the porosity and strength of the porous SBSC ceramics were investigated as functions of sintering temperature and Si:C ratio. The porosity increased with decreasing the Si:C ratio and increasing the sintering temperature. It was possible to fabricate SBSC ceramics with porosities ranging from 37% to 44% by adjusting the Si:C ratio and the sintering temperature. Addition of Al additive promoted densification and necking between SiC grains, resulting in improved strength. Typical flexural strengths of SBSC ceramics with and without Al addition were 44 MPa and 34MPa, respectively.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.3.1-3.1
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• 2009

Normal sintering process of producing porous ceramics is not to sinter perfectly, i.e., stop sintering in middle-process. Our porous ceramic materials are a product of complete sintering. For example if one want to make a porous carborundum, raw carborundum powder is sintered at either lower temperatures than normal sintering temperature or shorter sintering periods than normal sintering time to obtain incompletely sintered materials, i.e., porous carborundum. This implies normally sintered porous ceramic materials can mot be used in high vacuum conditions due to dust coming out from uncompleted sintering. We could produce completely sintered porous ceramic materials. For example, we can produce porous carborundum material by using carborundum particles bonded by glassy material. The properties of this material are similar to carborundum. We could make quasi-zero thermal expansion porous material by using carborundum and particles of negative thermal expansion materials bonded by the glassy material. We apply to sinter them also by microwave to sinter quickly. We also use HIP process to introduce closed pores. We could sinter them in large size to produce $2.5m{\times}2.5m$ ceramic plate to use as a precision plate for flat display industries. This flat ceramic plate is the world largest artificial ceramic plate. Precision plates are basic importance to any advanced electronic industries. The produced precision plate has lower density, lower thermal expansivity, higher or similar damping properties added extra properties such as vacuum vise, air sliding capacity. These plates are highly recommended to use in flat display industries. We could produce also cylindrical porous ceramics materials, which can applied to precision roller for polymer film precision motion for also electronic industries.

• 한국세라믹학회지
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• 제56권3호
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• pp.211-232
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• 2019

Porous ceramics are promising materials for a number of functional and structural applications that include thermal insulation, filters, bio-scaffolds for tissue engineering, and preforms for composite fabrication. These applications take advantage of the special characteristics of porous ceramics, such as low thermal mass, low thermal conductivity, high surface area, controlled permeability, and low density. In this review, we emphasize the direct foaming method, a simple and versatile approach that allows the fabrication of porous ceramics with tailored microstructure, along with distinctive properties. The wet foam stability is achieved under the controlled addition of amphiphiles to the colloidal suspension, which induce in situ hydrophobization, allowing the wet foam to resist coarsening and Ostwald ripening upon drying and sintering. Different components, like contact angle, adsorption free energy, air content, bubble size, and Laplace pressure, play vital roles in the stabilization of the particle stabilized wet foam to the porous ceramics. The mechanical behavior of the load-displacements curves of sintered samples was investigated using Herzian indentations testes. From the collected results, we found that microporous structures with pore sizes from 30 ㎛ to 570 ㎛ and the porosity within the range from 70% to 85%.

• 한국생산제조학회지
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• 제24권4호
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• pp.368-373
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• 2015

Porous alumina ceramics with two different pore sizes were fabricated using hollow microspheres as the pore-forming agent. The relative density, total porosity, and microstructure of the obtained alumina ceramics were studied. It was found that the total porosity of sintered samples with different amounts of hollow microsphere content, from 2.0 to 4.0 wt%, was 69.3-75.6%. The interconnected and spherical cell morphology was obtained with 3.0 wt% hollow microsphere content. The resulting ceramics consist of a hierarchical structure with large-sized cells, and small-sized pores in the cell walls. Moreover, the compressive strength of the sintered samples varied from 8.3-11.5 MPa, corresponding to hollow microsphere contents of 2.0-4.0 wt%.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.608-609
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• 2006

The deformation behavior under three-point bend test was found to depend on the loading uniformity and the macrostructure for SiC reticulated porous ceramics (RPCs). However, this dependence of loading uniformity is alleviated by improved macrostructure with fewer flaws and clogged pores. Even, this dependence becomes less important as the struts become thicker and stronger. The bend result of RPCs with highly uniform macrostructure is in excellent agreement with the GA (Gibson and Ashby) model, but the one with un-uniform macrostructure deviates from the GA model, suggesting that the macrostructure plays an important role in deformation behavior of RPCs under bend.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 춘계학술대회
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• pp.221-222
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• 1996

In order to prepare the porous hydroxyapatite (HA) ceramics with different porosity, interconnectivity, mechanical properties, surface chemistry and tissue response, several methods have been developed. Of the different forms of Porous HA ceramics which were prepared by various methods, only the coralline HA has undergone major clinical applications in orthopaedic, maxillofacial and ophthalmic surgery. In this study, totally synthetic macroporous HA ceramics with various pore size distribution were prepared. It is shown that the new reticulate HA ceramics, comprised of interconnected voids surmunded by a web of ceramic, have a morphology which mimics that of human trabecular bone.

• 한국분말재료학회지
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• 제27권4호
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• pp.325-332
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• 2020

In this study, the effects of kaolin addition on the properties of reticulated porous diatomite-kaolin composites are investigated. A reticulated porous diatomite-kaolin composite is prepared using the replica template method. The microstructure and pore characteristics of the reticulated porous diatomite-kaolin composites are analyzed by controlling the PPI value (45, 60, and 80 PPI) of the polyurethane foam (which are used as the polymer template), the ball-milling time (8 and 24 h), and the amount of kaolin (0-50 wt. %). The average pore size decreases as the amount of kaolin increases in the reticulated porous diatomite-kaolin composite. As the amount of kaolin increases, it can be determined that the amount of inter-connected pore channels is reduced because the plate-shaped kaolin particles connect the gaps between irregular diatomite particles. Consequently, a higher kaolin percentage affects the overall mechanical properties by improving the pore channel connectivity. The effect of kaolin addition on the basic properties of the reticulated porous diatomite-kaolin composite is further discussed with characterization data such as pore size distribution, scanning electron microscopy images, and compressive strength.