• 대한기계학회논문집B
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• 제26권9호
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• pp.1260-1266
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• 2002

In this study, to make an excellent heat pipe, the manufacturing technology of a sintered wick was investigated. Making a sintered wick is known to be very difficult but it has many advantages. For example, the porosity and pore size can be controlled and the capillary force is great. The mixture of copper and pore former powder was used as a wick material and ceramic-coated stainless steel was used as a mandrel which is necessary for vapor flow. To analyze the feature of the manufactured wick, not only porosity and pore size were measured but also the sintered structure was observed. A heat pipe with sintered wick was manufactured and the performance test of the heat pipe was performed in order to review cooling performance. The performance test results for the 4mm diameter heat pipe with the sintered wick shows the stability since the temperature difference between a evaporator and a condenser of the heat pipe is less than 4.4$^{\circ}C$, and thermal resistance is less than 0.7$^{\circ}C$/W, In the meantime the composite wick that is composed with sintered and woven wire was also examined. The heat transfer limit of the heat pipe with composite wick was enhanced about 51%~60% compare to the one with sintered wick.

• 한국세라믹학회지
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• 제49권4호
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• pp.347-351
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• 2012

Vermiculite-silica composites with a layered structure were fabricated by adding cellulose fibers as a pore former and by a simple uniaxial pressing and subsequent sintering process. Three different combinations of additives were used and their effects on the compressive strength and thermal conductivity of the composites were investigated. Both compressive strengths (42-128 MPa) and thermal conductivities (0.75-1.48 $W/m{\cdot}K$) in the direction perpendicular to the pressing direction (T) were higher than those (19-81 MPa and 0.32-1.04 $W/m{\cdot}K$) in the direction parallel to the pressing direction (S) in all samples. The anisotropy in both properties was attributed to the microstructural anisotropy, which was caused by the layered structure developed in the composites.

• 한국세라믹학회지
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• 제44권2호
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• pp.79-83
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• 2007

To fabricate a thick, porous yttria-stabilized zirconia without cracking and warping, a method for the simultaneous control of the porosity and shrinkage was designed. As a pore former, a potato starch was used. For the control of shrinkage the oxidation of Al metal particles was used. For the sintering of the above powder mixtures, a partial sintering technique was used at $1300^{\circ}C$ for 10 min in air. Upon adding the additives, high open porosity above 53% and a low shrinkage level were obtained. As a result cracking and warping of the sintered body were deterred. This outcome most likely resulted from the compensation of sintering shrinkage due to the volume expansion caused by oxidation of the Al metal particles during heat-treatment.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.540-543
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• 2003

There are many stone monuments which are weathered by natural or artificial factors in Korea. The partly weathering in stone could accelerate the rate of weathering, so it is demanded to keep them from the further weathering. Consolidation is evaluated as one of the efficient treatments which have a good effectiveness in stone monuments. But following the former researches, the effectiveness of consolidation could be different, related to the kinds of stone or consolidants. Therefore, in this study, the change of properties was monitored in the long term for the exact evaluation of the stability of the consolidated stone. It is estimated that the pore structure of consolidated stone was filled by consolidant, according to the measurements of ultrasonic velocity, and the digital image analysis of the sample was shown that the color property of stone surface has varied during the curing.

• 한국세라믹학회지
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• 제43권6호
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• pp.351-357
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• 2006

The fabrication process of the honeycomb filter was investigated using synthesized cordierite with the addition of pore former and extrusion additives (either organic matter or graphite). Also, the effect of additives on the resultant properties of honeycomb filter such as porosity, thermal expansion coefficient and mechanical strength were investigated. With increasing the organic matter up to 10 wt%, porosity was increased but compressive strength was decreased. With increasing the graphite content, however, both porosity and compressive strength were increased. The specimen with an optimum processing condition (C-17A30G, sintering at $1150^{\circ}C$) was demonstrated 59% in porosity, 69 MPa in compressive strength, and $2.4{\times}10^{-6}/^{\circ}C\;(25{\sim}1000^{\circ}C$) in thermal expansion coefficient, which physical properties are appropriate for the honeycomb filter applications.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.83.2-83.2
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• 2011

In this study, we fabricated tubular ceramic support for segmented-in-series solid oxide fuel cell (SOFC) by using MAO(MgAl-stabilized ) as main material and activated carbon as pore former. Thermal expansion properties of ceramic support with different amounts of activated carbon were analyzed by using dilatometer to decide a suitable sintering temperature. The tubular ceramic supports with different amounts of activated carbon (15, 20, 30wt.%) were fabricated by the extrusion technique. After sintering at $1400^{\circ}C$ for 2h, cross section and surface morphology of tubular ceramic support were analyzed by using SEM image. Also, the porosity, mechanical property, gas permeability of tubular ceramic supports was measured. Based on these results, we established the suitable fabrication technique of tubular ceramic support for segmented-in-series SOFC.

• 한국표면공학회지
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• 제26권2호
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• pp.45-54
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• 1993

In this study, magnetic properties of anodized Al film deposited with ferro-magnetic metals in the capacity of perpendicular magnetic recording media were measured and evaluated to find out the role of structure and morphology of the oxide films on magnetic characteristics. The object of this work was to present the conditions of magnetic thin film formation with more superior magnetic property. Anodizing was carried out under various conditions, and then the anodized film were electro-deposited with Co, Ni, Fe and their alloys. Coercive force and residual magnetization in perpendicular direction increased as the pore length of anodized film increased. It was attributed to the increase of the amount of depoisted metals and the ratio of length/diameter of pores. Morphology of anodized films in phosperic acid was not similar to that of sulfuric acid, and thin films in the former solution had perpendcular magnetic anisostropy because of large diameter, irregular length and distribution of the pores. It was found that magnetic properties of the thin films, which had doubled layer of two metals, were dominated by the metal electrodeposited on the surface of the anodized oxide films.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표대회 논문집(III)
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• pp.883-887
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• 1998

Hydration is the main reason for the growth of the material properties. A exact parameter to control the chemical and physical process is not the time, but the degree of hydration. Therefore, it is reasonable that development all material properties should be formulated in terms of degree of hydration. Mathematical formulation of degree of hydration is based on combination of reaction rate functions. The effect of moisture conditions as well as temperature on the rate of reaction is considered in the degree of hydration model. This effect is subdivided into two contributions: water shortage and water distribution. The former is associated with the effect of on the progress of hydration. The water needed for progress of hydration do not exist and there is not enough space for the reaction products to form. The latter is associated with the effect of free capillary water distribution in the pore system. Physically absorption layer does not contribute to progress of hydration and only free water is available for further hydration.

• 한국세라믹학회지
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• 제43권11호
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• pp.746-750
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• 2006

NiO films and Ru co-sputtered NiO films were deposited by reactive magnetron sputtering for micro-solid oxide fuel cell anode applications. The deposited films were reduced to form porous films. The reduction kinetics of the Ru doped NiO film was more sluggish than that of the NiO film, and the resulting microstructure of the former exhibited finer pore networks. The possibility of using the films for the anodes of single chamber micro-SOFCs was investigated using an air/fuel mixed environment. It was found that the abrupt increase in the resistance is suppressed in the Ru co-sputtered film, as compared to undoped film.

• 한국산학기술학회논문지
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• 제17권2호
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• pp.58-65
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• 2016

본 연구는 조직공학용 지지체로 사용될 막을 개발하기 위한 초도 연구 수행으로, 염화나트륨(NaCl)을 기공형성체로 혼합한 폴리카프로락톤(PCL)용액을 유리 캐스팅판에 분주한 후 필름 어플리케이터를 이용하여 다공성 PCL필름을 성형하였다. 성형된 필름은 건조 후 증류수에 침지시켜 NaCl을 추출하여 최종 멤브레인형 다공성 지지체를 제조하였다. 3차원 다공망을 형성시키기 위하여 NaCl을 기공형성체로 이용하였으며 $4^{\circ}C$, 실온, $40^{\circ}C$의 세 가지 건조조건에 따른 다공망의 형성과 형태를 주사전자현미경(SEM)을 이용하여 관찰 하였으며 기초적인 안전성 확보를 위한 세포독성평가를 시행하였다. 세 가지의 건조조건별 결과에서는 실온 건조조건에서 거대기공과 미세기공이 혼재된 3차원 다공망이 우수하게 형성된 것이 관찰되었으며 세포독성 시험결과 ISO10993-5 규격의 세포독성 판단기준에 따라 grade 2(mildly cytotoxic)로 나타난바 생체용으로 적합하다고 볼 수 있다. 본 연구를 통하여 멤브레인형 다공성 지지체 제조에 건조조건이 3차원 다공망의 형성 및 거대기공과 미세기공이 함께 형성되는 것에도 영향을 미치는 것으로 나타났으며 이 결과는 다공성 멤브레인 지지체의 분해성 조절 및 약물 담지 효과를 개선하기 위한 연구에서 다공도의 조절에 대한 기초적인 공정이 될 수 있다.