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임대우(Dae Woo Ihm) 호서대학교 공업기술연구소 2015 공업기술연구 논문집 Vol.34 No.2
O pposed je t를 사용하는 신장 흐름 시스템을 구성하고, 이 시스템에서 관측된 리타데이션 패턴으로부터, 폴리에틸렌 테레프탈레이트 고분자의 복굴절율을 측정하였다. 또한 이 값은 기존의 케필러리 다이를 사용하여 측정한 복굴절율과 비교 관찰하였다. 대칭축에 따라 관찰된 대칭 복굴절 패턴으로부터 이 지역에서의 분자간 정렬이 이루어짐을 알 수 있었고, 압출 온도를 낮출수록 간섭 프린지의 수가 증가하여 온도를 낮춤에 따라 분자 간 배향이 증가됨을 알 수 있었다. 이는 opposed jet 시스템을 활용하여 높은 속도구배와 고도의 배향도를 가진 멜트를 생성할 수 있음을 보여준다. Tne opposed jet system were used to generate elongational flow. The birefringence of Poly (ethylene terephthalate) was estimated by the observed retardation and was compared with that produced by using a conventional capillary die geometry. A symmetrical birefringence pattern is seen along the symmetry axis indicating molecular orientation in this region. The number of interference innges from the birefringent area to the symmetry axis is increased as the temperature is lowered. This indicates that the opposed jet system can produce high degree of elongational gradients and highly oriented melts.
임대우 ( Dae Woo Ihm ),권원호 ( Won Ho Kwon ) 한국공업화학회 2015 공업화학 Vol.26 No.1
Microcapsules containing the suspension of conducting materials such as carbon nanotube (CNT) or polyaniline (PANI) were prepared by in-situ polymerization of melamine and formaldehyde. Stable microcapsules were prepared and the mean diameter of the observed microcapsules was in the range of 10-20 μm. The surface morphology and chemical structure of microcapsules were investigated using optical microscope (OM), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FT-IR). The thermal properties of samples were investigated by thermogravimetric analysis (TGA). The conductivity of ruptured microcapsule containing the suspension of CNTs or PANIs in tetrachloroethylene and Isopar-G was measured. As the amount of CNTs and PANIs in the core of microcapsules increased, the measured current increased. Conductivity measurement results suggest that poly (melamine-formaldehyde) based core-shell microcapsules could be applied to self-healing electronic materials systems, where CNTs or PANIs bridge a broken circuit upon release.
태양전지용 다결정실리콘 웨이퍼의 표면 처리용 텍스쳐링제
임대우 ( Dae Woo Ihm ),이창준 ( Chang Joon Lee ),서상혁 ( Sang Hyuk Suh ) 한국공업화학회 2013 공업화학 Vol.24 No.1
텍스쳐링에 의해 실리콘 웨이퍼의 표면반사율을 감소시키는 것은 실리콘 태양전지의 효율향상을 위해 매우 중요한 공정이다. 본 연구에서는 에칭속도 제어를 위해 촉매제를 포함한 산 용액으로 텍스쳐링 처리한 웨이퍼의 표면효과와 그 태양전지 특성을 평가 고찰하였다. 텍스쳐링 전 HNO3-H2O2-H2O 용액의 전처리는 표면반사율의 초기 저감효과를 가져왔다. 이는 산화특성에 의해 유기 불순물이 제거되고 텍스쳐링을 위한 핵의 생성에 기인한다고 할 수 있다. 이후 공정에서 불산/질산 용액에 인산 및 초산과 같은 완충제를 첨가한 혼합용액을 제조하고, 적정 농도 조합과 그 처리시 간의 최적화를 통해 개선된 텍스쳐링 효과를 얻을 수 있었으며 이 효과는 표면반사율 감소를 통해 확인할 수 있었다. 이렇게 제조된 실리콘 웨이퍼에 반사방지막 코팅 후 태양전지를 제작하여 그 변환효율을 측정한 결과 16.4%의 양호 한 특성을 나타냈다. 이는 개선된 텍스쳐링 처리에 의해 저감된 표면특성에 의한 단락전류의 증가에 기인한 것으로 추정된다. Lowering surface reflectance of Si wafers by texturization is one of the most important processes for improving the efficiency of Si solar cells. This paper presents the results on the effect of texturing using acidic solution mixtures containing the catalytic agents to moderate etching rates on the surface morphology of mc-Si wafer as well as on the performance parameters of solar cell. It was found that the treatment of contaminated crystalline silicon wafer with HNO3-H2O2-H2O solution before the texturing helps the removal of organic contaminants due to its oxidizing properties and thereby allows the formation of nucleation centers for texturing. This treatment combined with the use of a catalytic agent such as phosphoric acid improved the effects of the texturing effects. This reduced the reflectance of the surface, thereby increased the short circuit current and the conversion efficiency of the solar cell. Employing this technique, we were able to fabricate mc-Si solar cell of 16.4% conversion efficiency with anti-reflective (AR) coating of silicon nitride film using plasma-enhanced chemical vapor deposition (PECVD) and Si wafers can be texturized in a short time.
폴리트리 메틸 렌 테 레프탈레이트 수지의 필름형성과 그 특성
임대우(Dae Woo Ihm) 호서대학교 공업기술연구소 2014 공업기술연구 논문집 Vol.33 No.1
Poly(trimethylene terephthalate)(PTT) polymer has been processed by typical thermoplastic melt extrusion processes. The molten polymer has good melt strength and can be easily extruded into films. Typical processing temperatures are about 2 5 0 to 265 で for film extrusion. To make oriented film , the stretching temperature is much lower and the stretching temperature w indow is m uch narrower than those o f PET. Physical properties have indicated that properties are similar in some respects to both PET and PBT and in some cases unique among this fam ily o f polyesters. The properties o f PTT film s indicate a potential for outstanding performance. It is a viable candidate for packaging applications which are presently addressed by N ylon 66, PET, and PBT. Poly (trimethylene terephthalate )(P T T ) 의 필름용도로서의 적용가능성을 검토하기 위하여 텐터프레임의 이축연신기를 사용하여 축차 이축연신필름을 제조하였다. PTT의 빠른 결정화속도 및낮은 T g , 높은 수축률 등은 PET 가공시에 비해 종 • 횡방향 연신온도 설정시 좁은 가공 범위와 낮은 연신온도를 필요로 하였다. 제조된 PTT 필름의 특성은 PET 대비 강 • 신도, 가스투과도 등은 유사하나, 탄성율은 1 /2 수준이며, 상온 유전율이 약간 낮은 특성을 보였다. PTT의 낮은 유리전이온도와 높은 수축률은 P TT 의 포장용도로서 수축 필름등에의 적합성을 보여준다.
Poly(L-lactide)(PLLA)/Polyoxyethylene(POE) 블록공중합체의 약불방출담체에 관한응용
이찬우,임대우,전근,Lee, Chan-Woo,Ihm, Dae-Woo,Jun, Kun 한국섬유공학회 2000 한국섬유공학회지 Vol.37 No.9
An A-B-A block copoly(ester-ether) comprising poly(L-lactic acid)(PLLA, A) and poly (oxyethylene)(POE, B) was prepared by copolymerization. The release rate of the model drugs form PLLA/POE particles was studied by varying the hydrophilicity of the model drugs as well as that of the copolymers. It was observed that the rate of controlled release from the copolymer microspheres is not dependent on the degradation of the polymer, but on the wall permeability which is defined as the product of diffusion coefficient and the solubility coefficient. The release rate was fast as long as the hydrophilicity of the copolymer was high, regardless of the composition of the copolymer. It was also found that the release rate was faster as the monomer composition of the oxyethylene unit becomes higher.