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유리전이온도(Tg) 측정에 의한 무기/유기복합체의 결합특성에 관한 연구
이동아,김구대,김현민,Lee, Dong-A,Kim, Goo-Dae,Kim, Hyun-Min 한국분석과학회 1992 분석과학 Vol.5 No.3
졸-겔법에 의해 무기-유기 복합체를 합성하였으며, 복합체의 결합특성을 알아보기 위하여 DMTA(Dynamic Mechanical Thermal Analyzer)를 이용하여 유리전이 온돈(Tg)를 측정하였다. HCl 과 물의 양이 증가될수록 Tg는 고운으로 진행됨으로부터 복합화가 더 잘 일어남을 알 수 있었다. 그러나 반응시간에 따른 Tg의 변화는 관찰되지 않았다. Inorganic/organic composite was synthesized by using sol-gel process, and the bonding characteristics of composite was investigated with glass transition temperature(Tg), measured by DMTA(Dynamic Mechanical Thermal Analyzer). It was found from shift of Tg to higher temperature that composite reaction was proceeded better with the amount of HCl and water. But Tg was not varied with reaction time.
TEOS-PEG계 Sol-Gel코팅에 의한 세라믹 분리 막의 제조 및 특성
김태봉,최세영,김구대,Kim, Tae-Bong,Choi, Se-Young,Kim, Goo-Dae 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.3
Sol-gel methods offer many advantages over conventional slip-casting, including the ability to produce ceramic membranes. They are purer, more homogeneous, more reactive and contain a wider variety of compositions. We produced ormosil sol using sol-gel process under various molecular weight of polymer species[polyethylene glycol(PEG)] in total system [Tetraethyl ortho silicate(TEOS)-polyethylene glycol(PEG)]. The properties of as-prepared ormosil sol such as viscosity and gelation time are characterized. Also, the ceramic membrane was prepared by dip-coating with synthetic sol and its microstructure was observed by scanning electron microscopy. The permeability and rejection efficiency of membrane for oil/water emulsion were evaluated as crossflow apparatus. The ormosil sol coated membrane was easily formed by steric effect of polymer and it improved flux efficiency because infiltration into porous support decreased. Its flux efficiency was elevated about $200\;l/m^2h$ compared with colloidal sol coated membrane at point of five minutes from starting test. Sol-gel 공정에 의해 제조된 세라믹 분리 막은 보다 순수한 재료를 이용할 수 있고, 균일성을 향상시킬 수 있을 뿐 아니라 다양한 복합체도 넓은 범위에서 반응을 유도할 수 있다는 장점을 가지고 있어 많은 연구가 진행되고 있다. 본 연구에서는 sc,1-gel 공정을 이용하여 Tetraethyl ortho-silicate(TEOS)-Polyethylene glycol(PEG)계 organically modified silicate(ORMOSt)sol을 합성하였다. Polymer분자량을 변수로 하여 sol 합성 후 특성 변화를 점도와 겔화 시간을 측정함으로써 관찰하였다. 합성된 sol을 다공성 담체 위에 dip-coating법을 이용하여 막을 제조하였으며, SEM관찰을 통해 분리 막의 미세구조를 확인하였다. 합성 복합 막의 Oil/water 에멀젼의 처리효율을 cross-flow 타입의 막 분리 장치를 이용하여 확인하였다. Ormosilsol은 유기물의 분자량이 증가될수록 보다 쉽게 코팅 층을 형성 시킬 수 있었고, 담체를 용매에 담지 시켜 코팅 물질이 담체의 기공내로 침투될 때의 모세관력을 줄임으로써 크랙이 방지된 얇은 막을 얻을 수 있었다. Colloidal sol 코팅 막에 비해 ormosil sol코팅 막은 분리효율 뿐 아니라 flux 특설이 시험 5분경과 시점에서 약 $200\;l/m^2h$이상 향상되었음을 확인 할 수 있었다.
개질 유황 고분자가 혼입된 포틀랜드 시멘트 콘크리트의 특성
유승건,최헌진,권혁,박노경,김구대,Yu, Seung-Gun,Choi, Heon-Jin,Kwon, Hyok,Park, No-Kyung,Kim, Goo-Dae 한국결정성장학회 2010 한국결정성장학회지 Vol.20 No.4
일반 포틀랜드 시멘트 콘크리트에 개질 유황 고분자가 혼입되었을 때의 압축강도 및 내염기성의 영향을 일반 포틀랜드 시멘트 콘크리트와 비교하여 나타내었다. 개질 유황이 혼입된 콘크리트는 일반 콘크리트에 비해 매우 큰 강도를 나타내었고, $55^{\circ}C$에서 배합 및 혼합 작업하였을 때 안정적으로 공시체의 제작이 가능하였다. 13%의 $CaCl_2$에 개질 유황이 혼입된 콘크리트 공시체를 침지되어 내염기성을 평가하였다. 내염기성 시험에서, 개질 유황이 혼입된 콘크리트는 $CaCl_2$에 대한 저항성은 일반 콘크리트에 비해 증가하였다. This paper describes the effects of modified sulfur polymer content on the compressive strength and chemical resistance of Portland cement concrete with and without the modified sulfur polymer. The Portland cement concrete which contained modified sulfur had much higher strength than the Portland cement concrete without modified sulfur, workability is stabled at $55^{\circ}C$. Alkali tolerance test was evaluated by immersing these concrete specimens in 13 % $CaCl_2$ solutions. In the alkali tolerance test, the resistance of Portland cement concrete with modified sulfur to $CaCl_2$ increased compared with Portland cement concrete without modified sulfur.
김구대,박지애,이동아,손용배 한국마이크로전자및패키징학회 1996 하이브리드마이크로일렉트로닉스 Vol.3 No.1
The Ru based thick film resistor for sintering at 900℃ was synthesized to prepare the co-fired LCR network. It was necessary the sintering temperature of the glass frit was increased to 900℃ in order to co-fire LCR network. This composition of glass frit could be prepared by decreasing the amount of PbO and increasing alumina and silica content. In this study, ruthenate paste was printed on inductor tape prepared by ferrite and co-fired at 900℃, and sheet resistance of the resistor was measured. The sheet resistance was increased and the residue of resistor paste was increased simultaneously with decreasing the amounts of PbO.
김구대,김창은,강현규,손용배 한국마이크로전자및패키징학회 1995 하이브리드마이크로일렉트로닉스 Vol.2 No.1
Pyrochlore type Pb₂Ru₂O_(6.5) powders with different amounts of RuO₂were synthesized, mixed with organic vehicle, solvent to form the resistor pastes. The properties of pastes were investigated after printing and sintering. ZrO₂, Nb₂O_5, CuO were added in these pastes as the TCR modifiers and the variations of TCR, with amounts of modifiers were investigated. In all cases, results showed that appropriate amounts of modifiers were less than 2wt%.
최강순,김구대,金昌殷 연세대학교 산업기술연구소 1977 논문집 Vol.7 No.1
. The effect of concentrations of urea and melamin resin solutions on the impregnation, thermosetting, and physical properties of the preformed gypsum body was studied to improve the mechanical strength and water resistivity of the substrate material. A maximum impregnation was obtained when the urea and melamin resin concentrations were 60% and 50%, or the viscosities were 100 cp and 200 cp, respectively. High mechanical strength of the resin impregnated gypsum was observed in this range of concentrations. The amount of residual free water in a heat-treated gypsum was found to be increasing and the mechanical strength, consequently, was found to be lowered with decreasing the resin concentration. Since the resin was considered to be absorbed only on the surface of the substrate material, water resistivity of the composite was found to be increasing up to three times of that of a hydrated gypsum, say 3 to 5%, as the concentration of the resin solution increased up to 60%.