• Polymer(Korea)
• /
• v.25 no.2
• /
• pp.151-160
• /
• 2001

Polymeric membranes consisting of poly(d,1-lactide) as a polymer matrix and crystallizable progesterone as a drug were prepared by coagulating polymeric solutions. The homogeneous casting solutions in dimethyformamide were solidified by using three different coagulating processes : solvent evaporation under vacuum, solvent extraction via immersion into the nonsolvent bath, or vapor exposure at high humidity condition. With solvent removal via evaporation under vacuum, the cast solution film was vitrified to form a homogeneous film containing progesterone of spherical shape distributed evenly in the film. Being prepared by solvent extraction via immersion into a water bath, the resulting membrane showed an asymmetric structure, with progesterone of big crystallites distributed unevenly in the structure. On the other hand, the coagulation under high humidity transformed the cast film into a sponge-like structure, where progesterone took a shape like flake.

• Journal of Ocean Engineering and Technology
• /
• v.23 no.2
• /
• pp.98-103
• /
• 2009

The resin infusion method is the latest technology of FRP laminating and cleaning to improve FRP hull quality. This method is focused on how to arrange infusion channels for the laminiating strategy. The laminating strategy using the resin infusion method has been utilized to complete the infusion work and remove the cavities on the FRP surface within the curing time. It is resulting from the arrangement of infusion and vacuum channels, the resin property, and the combination of FRP. This strategy has been depended on the field experience for manufacturing FRP without the resin infusion simulation. This study can help to improve the efficiency of FRP fabrication with the laminating strategy including the resin infusion simulation instead of the field experience.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.111-111
• /
• 2010

최근 전자 소자의 집적기술은 기존의 2차원에서 System on package (SOP) 개념에 기반을 둔 3차원 집적 기술로 발전 되어가고 있다. 소자의 3차원 실장을 실현시키는 과정에서 세라믹의 여러 유용성이 언급되어져 왔지만, 취성이 매우 크다는 등의 단점이 있었다. 이러한 이유로 연성을 가지는 폴리머와 세라믹을 합성한 복합체 기판에 대하여 많은 연구가 되고 있다. 그러나 세라믹 제작을 위해서는 높은 공정온도가 요구되고 있고 이러한 높은 공정상에서의 온도는 3차원 실장에 있어서 문제점이 되고 있다. 이러한 문제점을 극복하기 위하여 상온에서 치밀한 세라믹 후막을 제작할 수 있는 공정인 Aerosol Deposition Method (ADM)방법으로 세라믹-폴리머 후막의 제조를 시도하였다. 일반적으로 ADM은 수백 나노의 출발 파우더를 사용하여 치밀한 세라믹 막을 형성하는데 사용된다. 본 연구에서는 ADM으로 100 nm미만의 나노 세라믹 파우더를 사용하여 다공성의 세라믹 후막을 제조한 후 resin을 함침시키는 방법으로 세라믹-폴리머 후막의 제조를 시도하였다. 그 결과 운송가스, aerosol 농도 등의 공정조건을 변화시켜 다공성의 $Al_2O_3$ 후막을 제조하였고, 이 다공성 후막은 반투명의 특성을 보이며 고충전율로 형성되었다. 이렇게 제조된 나노 다공성 $Al_2O_3$ 후막에 cyanate ester resin을 함침시키는 방법을 사용하여 $Al_2O_3$-cyanate ester 복합체 후막을 제조하였으며, 이의 비유전율 및 품질계수는 각각 1 MHz에서 6.7, 1000으로 우수한 유전특성을 보임이 확인되었다.

• Journal of the Korean Ceramic Society
• /
• v.39 no.11
• /
• pp.1069-1073
• /
• 2002

Properties of $B_4C/Al$ cermets were studied as a function of atmosphere during infiltration and post-heat treatment. The cermet A(infiltrated at $1100{\circ}C$/10 min under vacuum) had 19.4 wt% of Al but the cermet B(infiltratd at $1080{\circ}C$/10 min under a flowing argon) showed 14.4 wt% of Al. It indicated that the reaction between $B_4C$ and Al underwent slower under vacuum than under a flowing argon. The cermet B as infiltrated showed the density of 2.65 $g/cm^3$, the MOR of 503 MPa and the Young's Modulus of 237 GPa, but the post-heat treatment at $900{\circ}C$ for 8h under a flowing Ar gave rise to the cermet with the density of 2.65 $g/cm^3$, the MOR of 296 MPa, the Young's Modulus of 300 GPa. The cermet B showed better properties than the cermet A. Changes in compositions of the cermets by the post-heat treatment were observed qualitatively by XRD and SEM, the amount of Al was determined by analysis of its DSC curve.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 2011.04a
• /
• pp.192-195
• /
• 2011

건축물의 밀집화로 인해 화재 확산으로 인한 피해를 막기 위한 연구는 꾸준히 진행되었다. 이에 방화구획이 도입 되었으며 이 중 방화문은 화염과 연기 전파를 차단하는 문의 역할을 한다. 본 연구에서는 목재 방화문에 사용되는 목재의 난연제 처리에 따른 난연 성능을 평가하였다. 실험 결과, $0.7kgf/cm^2$ 진공압력 내에서 30분간의 함침 처리를 통해 난연성능을 확보할 수 있는 것으로 나타났다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.135-135
• /
• 2016

차세대 가스터빈 엔진 및 초음속 항공기 내 고온부의 온도가 증가함에 따라, 기존의 초내열합금 기반 소재를 사용하기 어려워지고 있다. 초고온 세라믹스는 높은 기계적 물성, 화학적 안정성 등 우수한 고온 특성을 가지고 있어 기존의 초고온 소재를 대체 할 수 있는 물질로 부상되고 있다. 하지만 기존의 금속 기반 소재 대비 높은 밀도로 인하여 초고온 세라믹 단일체를 비행체 부품에 적용하기에는 어려움이 있다. 이에 초고온 세라믹스와 탄소섬유를 포함하는 세라믹 복합체(Ceramic Matrix Composite, CMC)를 제작하여 동등한 기계적 물성을 보이면서 무게를 감소시키는 연구들이 진행 중에 있다. 초고온 세라믹스가 함침 된 세라믹 복합체의 경우 우수한 내삭마, 내산화 특성을 보이지만, 장시간 고온에 노출되어 탄소 섬유가 드러나게 되면 급격한 산화로 인해 소재 특성의 열화가 진행되는 단점을 가지고 있다. 따라서, 탄소 섬유가 드러나지 않도록 복합체 표면에 코팅층을 형성하여 세라믹 복합체 모재를 보호하는 방법이 활발히 연구되고 있다. 본 연구에서는 진공 플라즈마 용사 공정을 이용하여 다양한 공정조건 하에서 초고온 세라믹 코팅층을 형성하였다. 수십 마이크론 크기 분포를 갖는 HfC 분말을 Ar 유송 가스를 이용하여 플라즈마 화염 내부로 투입하였다. 플라즈마 화염 가스는 Ar 과 H2를 혼합하여 구성되었으며, 분위기 가스로는 N2를 사용하였다. 코팅에 사용된 모재로는 ZrB2 단일체와 SiC가 미량 포함된 HfC 단일체를 사용하였다. 다양한 공정 조건하에서 형성된 HfC 코팅층의 두께, 미세 조직구조를 SEM을 이용하여 관찰하였으며, XRD를 이용하여 형성된 HfC 코팅층의 결정구조를 분석하였다.

• Korean Chemical Engineering Research
• /
• v.59 no.4
• /
• pp.521-531
• /
• 2021

Vacuum Pressure Impregnation (VPI) is a process that enhances physical properties by coating some types of epoxy resins on windings of stator used in large rotators such as generators and motors. During vacuum and pressurization of the VPI process, resin gas is generated by vaporization of epoxy resin. When the tank is opened for curing after finishing impregnation, resin gas is leaked out of the tank. If the leaked resin gas spreads throughout the workplace, there are safety and environmental problems such as fire, explosion and respiratory problems. So, exhaust system for resin gas is required during the process. In this study, a case study of exhaust efficiency by location of vent was conducted using Computational Fluid Dynamics (CFD) in order to design a system for exhausting resin gas generated by the VPI process. The optimal exhaust system of this study allowed more than 90% of resin gas to be exhausted within 1,800 seconds and reduced the fraction of resin gas below the Low Explosive Limit (LEL).

• Journal of Conservation Science
• /
• v.6 no.2 s.8
• /
• pp.126-140
• /
• 1997

There were some cases in the past that waterlogged wooden finds were neglected and damaged severely because adequate methods of conservation processing could not be found. However, since a wooden ship unearthed in Anapji of Kyongju was processed by poly(ethylene glycol) (PEG) impregnation method in 1975, most of waterlogged wooden finds have been processed by diverse scientific methods. Most commonly-used conservation processing methods of waterlogged wooden finds in Korea are PEG impregnation method, alcohol-ether-resin method and vacuum freeze-drying method. New methods developed recently in Europe and Japan such as sucrose method, sugar-alcohol method and higher alcohol method are also being studied here. The most important task in conservation processing of waterlogged wood is to find good impregnation materials suitable to Korean climate and environments and develop their application methods. For efficient conservation processing, it is important to know the natures of finds and impregnation materials and relation between impregnation and drying condition. To achieve it, many experiments and studies are needed.

• Conservation Science in Museum
• /
• v.14
• /
• pp.7-12
• /
• 2013

The conservation has been conducted for the fragments of an wooden boat in the Neolithic Age, excavated from Bibong-ri, Changnyeong, Korea. The vacuum-freeze drying have been applied to mostly to the small relics, such as wooden lacquerwares or small wooden goods etc.. Therefore, the large objects like a wooden boats have been treated almost by air-drying after impregnation with aqueous PEG solution. The air-drying is needed to impregnate with PEG aqueous solution during long period and run the risk of the fault generation. This report explain an example adapted for the fragments of the wooden boat by humidity-controlled drying(HCD) with slow adjusting moisture content. We did the chemical pre-treatment, PEG aqueous solution. The concentration of the aqueous solution was increased gradually from 10% to 80%. After the impregnation, the objects were dried by the HCD. The dimensional stability of the fragments after treatment was good.

• Conservation Science in Museum
• /
• v.12
• /
• pp.47-52
• /
• 2011

The authors did conservation treatment of wooden objects excavated from Isong Sanung Fortress upon request of the Museum of Hanyang University. The authors investigated types of the trees prior to conservation treatment to find out 1 Pinus spp. and 11 Querus spp. The authors investigated paint coating of 1 wooden ware to find out No.4 of the exterior and No.3 of the interior and about 100㎛ thickness of the lacquer layer. The. conservation treatment was done to immerse wooden ware into high molecular PEG#3,350 in water solution (10 ~ 45%) and to give physical strength and to do vacuum freeze drying.