• Composites Research
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• 제29권5호
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• pp.269-275
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• 2016

Multiscale hybrid composites, which consist of polymeric resins, microscale fibers and nanoscale reinforcements, have drawn significant attention in the field of advanced, high-performance materials. Despite their advantages, multiscale hybrid composites show challenges associated with nanomaterial dispersion, viscosity, interfacial bonding and load transfer, and orientation control. In this paper, carbon nanotube(CNT)/carbon fiber(CF)/polycarbonate(PC) multiscale hybrid composite were fabricated by a solution process to overcome the difficulties associated with controlling the melt viscosity of thermoplastic resins. The dependence of CNT loading was studied by varying the method to add CNTs, i.e., impregnation of CF with CNT/PC/solvent solution and impregnation of CNT-coated CF with PC/solvent solution. In addition, hybrid composites were fabricated through surfactant-aided CNT dispersion followed by vacuum filtration. The morphologies of the surfaces of hybrid composites, as analyzed by scanning electron microscopy, revealed the quality of PC impregnation depends on the processing method. Dynamic mechanical analysis was performed to evaluate their mechanical performance. It was analyzed that if the position of the value of tan ${\delta}$ is closer to the ideal line, the adhesion between polymer and carbon fiber is stronger. The effect of mechanical interlocking has a great influence on the dynamic mechanical properties of the composites with CNT-coated CF, which indicates that coating CF with CNTs is a suitable method to fabricate CNT/CF/PC hybrid composites.

• Journal of the Korean Wood Science and Technology
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• 제23권4호
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• pp.1-9
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• 1995

This study was carried out to experiment the dimensional stabilization of woods of red pine (Pinus densiflora S. et Z.) and sugi(Cryptomeria japonica D. Don) by vacuum impregnation of polyehtylene glycols(PEG) with mo. wt. 200, 400, 600, 1000; polypropylene glycols (PPG) with mo. wt. 425,725 ; PEG-acryloylates, and PPG-acryloylates synthesized, and then by water soaking. The results obtained are as follows: 1. The density of sapwood and heartwood was different from each other in both species. 2. The PEG and PEG-macromers with lower molecular weight by impregnation has increased the density of wood specimens more higher, thereby caused their higher volume expansion, and those with higher molecular weight than 600 has tended to down their density increment. 3. Before and after water soaking, the density decrease of specimen impregnated was high in woods impregnated with simple PEG and PPG, while lower in specimens impregnated with PEG-macromers and PPG-macromers. 4. So PEG-macromer was expected to hold the original dimension of decayed wood for antiques, but it was necessary to develop another penetration method as well as aqueous solvent.

• KEPCO Journal on Electric Power and Energy
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• 제3권2호
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• pp.113-117
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• 2017

As the competition in the manufacturing market for small and medium sized generators is intensifying, there is increasing pressure to reduce production cost. Manufacturing the generator stator windings with global vacuum pressure impregnation (GVPI) is a very effective way to reduce costs. However, the stator winding has a fatal disadvantage in that the insulation wears due to vibration in the slot. KEPRI (KEPCO Research Institute) conducted insulation diagnosis for three generators in KOMIPO (Korea Midland Power Co., Ltd.) which were manufactured by GVPI and operated for about 17 years. Insulation diagnosis showed that deterioration of insulation has progressed significantly. Therefore, KEPRI recommended replacing the stator windings of all three generators. In this paper, the insulation properties of the generator stator winding with global GVPI are described by comparing and analyzing the insulation diagnosis results and visual inspection for stator windings.

• 전기학회논문지P
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• 제59권3호
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• pp.311-316
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• 2010

According to increase of combined cycle power generation, the manufacturing market of gas turbine generator has become more competitive, so there is high pressure on the manufacturer to reduce generator price. Global VPI(vacuum pressure impregnation) method is effective to save the production cost and time for manufacturing stator windings, but it has an abrasion problem by vibration between stator windings and slots. This paper presents the insulation breakdown case, which is for VPI type generator during high voltage insulation tests, and also shows the cause analysis, repair works as well as reliability test. the purpose of this paper is to understand the insulation properties of VPI type generator and to know prevention of insulation weakness.

• Journal of the Korean Wood Science and Technology
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• 제28권4호
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• pp.51-55
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• 2000

The woodceramics which are new porous carbon materials were obtained by carbonizing from thinned small log of Aomori HIBA (Thujopsis dolabrata S. et. Z. var. hondae M.) impregnated with phenol resin in a vacuum furnace. During the carbonization process, the resin changes into glassy carbon, which has superior property. The resin impregnation rate and bending strength depend on the types of board and density. In this paper, the manufacturing method of woodceramics made from thinned small logs of Aomori HIBA was introduced and some properties were examined.

• 한국구조물진단유지관리공학회 논문집
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• 제24권2호
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• pp.103-110
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• 2020

본 연구는 바인더젯 3D 프린팅 출력물의 강도증진을 위하여 진공함침 후처리 공정의 적용성을 검토하였다. 또한, 출력물 크기에 따른 강도발현 한계를 확인하기 위하여 10 mm, 20 mm, 30 mm 및 40 mm 큐빅 출력물을 대상으로 침투성, 부피밀도 및 압축강도를 확인하였다. 그 결과, 진공함침 후처리 공정에서 최대압력이 증가함에 따라 후처리 용액이 출력물 내부까지 침투하게 되고 이에 따라서 침투면적률이 개선되는 것을 확인하였다. 출력물 압축강도율과 후처리 용액 침투면적률은 보정결정계수 0.992의 지수함수 형태의 상관관계를 나타내고 있다. 또한, 부피밀도가 증가하였으며 이는 후처리 용액이 내부까지 침투한 것으로 유추할 수 있다. 결론적으로 바인더젯 3D 프린팅 출력물의 강도증진을 위해서는 출력물 내부까지 후처리 용액을 침투하는 것이 필수적이며, 이를 위한 유효한 방법으로써 진공함침을 제안한다.

• 보존과학회지
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• 제6권2호
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• pp.126-140
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• 1997

과거에는 유적에서 수침목재유물이 발굴되면 적당한 보존처리 방법을 찾지못해 그대로 방치하여 유물을 심하게 손상시키는 경우도 있었다. 1975년 경주 안압지에서 발굴된 목선이 PEG함침법으로 보존처리된 이 후, 대부분의 수침목재유물은 보다 다양하고 과학적인 방법에 의하여 보존처리 되고 있다. 우리나라에서 주로 이용되고 있는 수침목재의 보존처리법은 PEG함침법과 알코올-에테르-수지법, 진공 동결건조법 등이며 근래 유럽과 일본에서 실용화된 슈크로오스와 당-알콜류를 이용한 함침강화법, 고급 알코을 등에 대한 적용방법 연구가 진행되고 있다. 수침목재 보존처리에 있어서 가장 중요한 과제는 우리나라 풍토와 환경조건에 적합하고 물성이 우수한 함침재료와 그 적용방법을 개발하는 것이다. 또 효율적인 보존처리가 이루어질 수 있도록 하기 위해서는 처리대상 유물의 재질적 특성, 함침재료의 물성, 함침과 건조 조건 간의 상호 유기적인 관계를 정확히 파악하는 것이 중요하며 이를 위해 다각적 측면에서의 실험연구가 필요하다.

• 보존과학회지
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• 제21권
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• pp.49-58
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• 2007

고대칠기 보존처리를 모의시험하기 위하여 현생 칠기를 대상으로 다양한 보존처리법을 적용한 결과 PEG#3350 40%(수용액)처리가 수축률이 낮아 치수안정화 처리효과가 우수한 것으로 나타났다. Sucrose 19%+Glycerin 1%(t-butanol 5% in water)처리의 경우 지속적으로 중량이 증가되었다. 반면 Sucrose의 함침처리과정에서 시험편내부와 처리용액의 농도평형을 이루지 못하여 농도 차가 발생되므로 내부의 수분이 시험편 밖으로 나오는 탈수현상에 의해 중량이 감소하였다. 따라서 보다 긴 함침기간이 요구되는 것으로 판단되며 이는 장기간 함침처리로 탈수 현상을 방지할 수 있다. 또한 고분자량(PEG #3,350)의 처리제와 저분자량의 처리제 모두 칠기 내부로의 침투가 확인되어 진공 동결건조법뿐 만 아니라 각 처리제를 고농도로 함침 처리 한 후 자연건조 조습건조처리도 가능함을 보여주고 있다.

• Journal of the Korean Wood Science and Technology
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• 제43권6호
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• pp.792-797
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• 2015

진공가압 수지함침 처리에 의한 목재의 휨강도, 경도 및 내마모성 향상을 위하여 침엽수 3수종에 수용성 멜라민 수지를 수지농도와 처리시간별로 진공가압 처리한 후 수지함침 열압축목재(compreg)를 제조한 다음 물성을 검토하였다. 또한 같은 수종에 수용성 난연제를 도포처리하는 방법과 진공가압 후 열압처리 방법으로 제조한 다음 난연성 향상정도를 측정하였다. 수지의 농도가 높을수록 휨강도 및 브리넬 경도는 증가하였고 내마모성은 향상되었으나, 처리시간과는 일정한 경향이 없었다. 난연성은 도포시험편 보다 진공가압처리 시험편이 총 방출열량이 감소하여 진공가압처리에 의한 난연성 개선 방법이 효과가 있었다.

• 한국세라믹학회지
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• 제35권9호
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• pp.974-980
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• 1998

This study is concerned with the production of carbon fiber reinforced carbon(C/C) with polyaromatic mesophase pitch as matrix precursor and with the investigation of friction-wear characteristics in ambient air using a constant speed type of friction tester. The main problem in using the polyaromatic mesophase as the matrix precursor is the high viscosity which may limit the complete impregnation of the fiber preform in the vacuum. To solve these problems two dimensional carbon fiber fabrics were infiltrated with meso-phase pitch in the pitch impregnator. After the impregnation and the heat treatment process. C/C com-posites were characterized by density porosity to monitor the influence of high pressure and temperature. It showed that the bulk density was increased and the apparent porosity and the density increasing rate was reduced as repeating the impregnation the carbonization and the heat treatment. The friction-wear charac-teristics of C/C composites were investigated by measuring the average friction coefficient and the specific wear rate as functions friction speed and friction pressure using a constant speed type of friction tester. C/C composite4s showed the average friction coefficient to be reduced as increasing the friction speed and the friction pressure.