• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
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• pp.31-34
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• 2005

미세균열이 생기기 전 $80^{\circ}C$ 물속에서 침수시간이 변함에 따른 $Avimid^{R}$ K3B/IM7 복합재의 습기노화현상에 관하여 연구하였다. $80^{\circ}C$ 물속에서 복합재의 강성을 저하시키는 요인으로는 수지 강성의 저하나 잔류응력의 변화 그리고 섬유와 수지 사이의 계면 손상이다. $80^{\circ}C$ 물속에서 수지에 습기가 포화되는 시간은 500 시간이며 K3B/IM7 복합재에 습기가 포화되는 시간은 100 시간이다. $80^{\circ}C$ 물속에서 수지가 500 시간 가속노화한 후 DSC 시험을 한 결과 $T_{g}는 1\%$ 이내 증가하였으며 무게는 $1.55\%$증가하였다. $80^{\circ}C$ 물속에서 수지의 습기 포화 속도가 복합재의 습기 포화 속도 보다 빨랐다. 500 시간 노화한 후 수지의 파괴인성은 $37\%$ 저하하였으며 100 시간 노화한 후 [+45/0/-45/90]s K3B/IM7 복합재의 미세균열 파괴인성은 $28\%$ 감소하였다.

• Bulletin of the Korean Chemical Society
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• 제26권12호
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• pp.2051-2053
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• 2005

• Transactions on Electrical and Electronic Materials
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• 제13권2호
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• pp.89-92
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• 2012

The effect of organic impurities on the electrical properties of a neat epoxy resin was studied. 0.05, 0.5 and 1.0 phr of iso-propyl alcohol (IPA) and methylene chloride (MC) mixture (50/50 wt%) were used as impurities. The current density, volume resistance and impedance characteristics of the epoxy/IPA/MC systems were measured with a high voltage source meter and broadband dielectric spectroscopy. Glass transition temperature (Tg) was measured by a differential scanning calorimetry (DSC) and it was found that Tg decreased slightly with increasing IPA/MC content. It was also found that Tg values of the epoxy systems with various IPA/MC contents were closely related to the current density, volume resistance and impedance characteristics.

• 천문학회보
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• 제35권1호
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• pp.91.2-91.2
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• 2010

We present far-ultraviolet (FUV) observations of comet C/2001 Q4 (NEAT) obtained with Far-ultraviolet Imaging Spectrograph (FIMS, also called SPEAR) around perihelion between 8 and 15 May 2004. Several important emission lines, including S I (1425, 1474 ${\AA}$), C I (1561, 1657 ${\AA}$), CO (1087.9, 1340-1680 ${\AA}$) were detected. Especially, the spectral features of CO are its electronic transitions belongings to the A-X, C-X systems. We also obtained radial profile of S I, C I, H I $Ly{\beta}$ with line fitting from central coma. The production rate of several spectral lines calculated from observed FUV photon flux. FUV spectral images of S I, C I, H I $Ly{\beta}$ emission lines were obtained.

• Carbon letters
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• 제5권1호
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• pp.23-26
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• 2004

A study of partial carbonisation of green pitch fibres to temperatures in the range of 500-$1000^{\circ}C$ was carried out on three precursors - a neat pitch and two polymer modified pitches, with a view to find out a suitable temperature at which the fibres acquire considerably improved toughness or handleability (compared to that in the green stage) for their subsequent processing into carbon fibres. A partial carbonisation temperature of 500-$600^{\circ}C$ has been identified to result in a remarkable improvement in the toughness/handleability of the fibres in all the three cases. However, from techno-economical considerations, the neat pitch appears to provide the best precursor system for the production of pitch based carbon fibres.

• 한국세라믹학회지
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• 제53권1호
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• pp.24-33
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• 2016

The grafting reaction for maleic anhydride (MA) onto high density polyethylene (HDPE) was investigated from solution process with initiators. The chemical modification of neat HDPE was carried out with various contents of MA (3-21 wt.%) and initiator (0.2-1 wt.%) at different temperature ($80-130^{\circ}C$). The grafting degree was obtained from the titration and the highest grafting degree was 3.1%. The grafting degree increased as the content of MA and initiator increased, however, the highest grafting degree was demonstrated for a particular content of MA and initiator. In the non-isothermal crystallization kinetics, the Ozawa model was unsuitable method to investigate the crystallization behavior of MA onto HDPE, whereas the Avrami and Liu models found effective. The crystallization rate was accelerated as the cooling rate increased, but postponed by combination of MA onto neat HDPE backbone.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.436-437
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• 2007

Organic light-emitting diodes (OLEDs) were fabricated with the electron dominant complex, 4,7-diphenyl-1, 10-phenanthroline (Bphen) into the traditional electron transporting material of tris (S-hydroxyquinoline) aluminum $(Alq_3)$, neat $Alq_3$ and Bphen as electron-transporting layers (ETLs), respectively. Use of the Bphen material results in efficient electron injection and transport, allowing for high luminous efficiency devices. The devices with neat $Alq_3$(Device1), 1:1 mixed $Alq_3$ : Bphen(Device2), and Bphen(Device3) have efficiency of 15.3cd/A, 16.9cd/A, 20.9cd/A, respectively, at $20\;mA/cm^2$. The efficiency characteristic of device with Bphen is best, but the device that is satisfied high efficiency and stability at once is observed in Device2.

• 폴리머
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• 제36권6호
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• pp.745-755
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• 2012

Two types of polymers were tested in this study; poly(ethylene terephthalate) (PET) as a synthetic example and poly(lactic acid) (PLA) as a natural polymer. DSC analyses showed that the use of nanofiller increased the degree of crystallinity ($X_c$) of both PET and PLA polymers, but the effect was more noticeable on PET nanocomposites. The crystallization of PLA and PET nanocomposites occurred at higher temperatures in comparison to neat polymers. According to dynamic mechanical-thermal analysis (DMTA), the damping factor of PET/$TiO_2$ nanoparticles decreased compared to the neat matrix, but for PLA nanocomposites the opposite trend was observed. Results of the mechanical test showed that for both PET and PLA nanocomposites, the most successful toughening effect was observed at 3 wt% loading of $TiO_2$ nanoparticles. SEM micrographs revealed uniform distribution of $TiO_2$ nanoparticles at 1 and 3 wt% loading levels. The results of WAXD spectra explained that the polymorphs of PLA and PET was not affected by $TiO_2$ nanoparticles. UV-visible spectra showed that $TiO_2$ nanocomposite films had high ultraviolet shielding compared to neat polymer, but there was significant reduction in transparency.

• Composites Research
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• 제20권3호
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• pp.17-24
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• 2007

본 연구는 순수 Kevlar 직물과 실리카 입자를 포함하는 전단농화유체가 함유된 Kevlar 액체방탄재(STF-Kevlar)에 대한 방탄충격에 의한 파단모드 연구이다. Cal.22 파편탄과 9mm FMJ 볼탄에 의한 방탄시험에 의하여 이 두 재료는 거시적 측면에서 다른 파단모드를 보여주었다. 순수 Kevlar 직물에서는 얀의 뽑힘(Pull-out)이, 그리고 STF-Kevlar 액체방탄재에서는 얀의 파단이 충격에너지를 흡수하는 주 기구로 나타났다. 전자주사현미경에 의한 미시적 관찰에서 Kevlar 섬유 표면의 벗겨짐, 섬유가 여러 가닥으로 갈라지는 스프리트, 그리고 섬유의 절단, 이 세가지 파단 모드가 손상 정도의 차이는 있지만 공통적으로 두 재료에서 관찰되었다. STF-Kevlar에서, 얀 섬유의 파단은 첫째는 실리카 입자로 덮여있는 얀-얀, 직물-직물 사이의 마찰력과, 둘째는 충격시 전단농화 현상의 발생으로 얀의 이동이 강력하게 억제되기 때문인 것으로 보인다.

• Composites Research
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• 제20권3호
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• pp.1-7
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• 2007

본 연구는 전단농화유체(STF)가 함침된 Kevlar 복합재료(STF-Kevlar composite)의 제조 및 방탄성능 평가에 관한 내용이다. 전단농화유체는 fumed silica와 구형 silica를 에틸렌글리콜에 혼합하여 제조하였고 이 유체를 Kevlar직물에 함침시켜 액체방탄재료를 제작하였다. 전단농화거동을 조사한 결과 사용된 STF는 모두 전단농화거동이 발현됨을 확인하였다. 그리고 방탄시험 결과 구형silica STF-Kevlar 복합재료가 보다 우수한 방탄특성을 나타내었다. 한편 방탄시험 시 neat Kevlar 시험편에서는 탄자가 섬유를 pull-out하면서 관통하는 현상이 발생하였으나 LBA시험편에서는 섬유의 pull-out 대신 원주방향으로 섬유가 변형되면서 방탄재료가 변형되는 거동을 보여 서로 다른 변형거동을 각각 나타내는 것으로 관찰되었다.