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세라믹/고분자 복합체의 열처리에 의한 탄소 함유 실리카 유리의 제조
김구대,이동아,박지애,문지웅 한국세라믹학회 1999 한국세라믹학회지 Vol.36 No.5
A carbon-containing silica glass was prepared from orgaincally modified silicate(Ormosil) by heat treatment in N2 atmosphere after the ormosil was synthesized using sol-gel method. The Ormosil was fabricated from the TEOS as the inorganic component and the PDMS as the organic component. The Ormosil changed to balck-coloured glass by carbon decomposed from the PDMS when the Ormosil was heated to 450$^{\circ}C$ 20hrs. A dense silicon oxycarbide glass with 2.08 g/cm3 was obtained by heating the Ormosil at 1050$^{\circ}C$ 10hrs. The microstructure of the carbon-containing silica glass was observed by SEM and the SiOxC4-x structure was confirmed by XPS measurement. The densification of the glass was studied by measurements of specific surface area linear shrinkage and geometric density.
고체산화물 연료전지용 Ni-YSZ 음극의 미세구조와 임피던스특성에 미치는 YSZ 입자크기 및 소결온도의 영향
김구대,문지웅,이기태,이홍림 한국세라믹학회 2001 한국세라믹학회지 Vol.38 No.5
Ni-YSZ 음극의 미세구조와 임피던스특성에 미치는 YSZ 입자크기 및 소결온도의 영향을 고찰하였다. 0.3~0.6$\mu\textrm{m}$의 미세한 NiO 분말을 사용할 경우에는 NiO 분말과 크기가 비슷한 미세한 YSZ 분말(TZ8Y, 0.3$\mu\textrm{m}$)을 첨가했을 때 NiO의 입성장을 억제하는 효과가 가장 크고 환원후 Ni의 입자크기를 미세하게 유지할 수 있는 미세구조를 형성하였다. 또한 미세한 YSZ 분말 (TZ8Y, 0.3$\mu\textrm{m}$)과 조대한 YSZ 분말(FYT13.0, 2$\mu\textrm{m}$)의 혼합비를 달리하여 후막을 제조하였을 때에 TZ8Y 분말만 첨가한 조성이 가장 낮은 분극 저항을 나타내었다. 한편 소결온도는 삼상계면의 양과 분극저항에 영향을 주었으며, 140$0^{\circ}C$에서 소결한 시편의 분극저항이 가장 낮은 값을 나타내었다.
김구대,정형진,이해욱 한국세라믹학회 1991 한국세라믹학회지 Vol.28 No.2
Polymeric alumina sol and polymeric silica sol were synthesized from aluminum sec-butoxide and tetraethyl orthosilicate, respectively as starting materials. A clear mullite sol was obtained by mixing these sols. When the mullite sol had a proper viscosity which was dependent on drying time, the fibers were fabricated by spinning. The optimum viscosity for fabrication of mullite fibers was 103-104 cps, and the fibers with various sizeswere made using the sols. The mullite was a major phase of the calcined fibers and the diameters of the fibers were about 50$\mu\textrm{m}$.
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%.
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,박지애,이홍림,송휴섭,Kim, Gu-Dae,Park, Ji-Ae,Lee, Hong-Rim,Song, Hyu-Seop Materials Research Society of Korea 1999 한국재료학회지 Vol.9 No.1
The $BaTiO_3$ powders were synthesized by GNP (Glycine-Nitrate process). The powders were prepared using carbonate and alkoxide as starting materials and nitric acid was used as a solvent for starting materials as well as an oxidant for combustion. the effects of aggregates in $BaTiO_3$ powders on green densities, sintering and dielectric characteristics were investigated. When the glycine/cation molar ratio was 1.2, reactivity of self-combustion was most intensive and the degree of aggregates after calcination was low. On sintering at $1400^{\circ}C$, maximum theoretical relative density(94.99%%0 was obtained in case of 1.2 molar ratio of glycine/cation. The dielectric constant of this sintered $BaTiO_3$ was 1919.
유기염료의 기저체로 사용된 세라믹/고분자 복합체의 미세구조변화가 광학특성에 미치는 영향
김구대,이동아,김재동,박지애 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.12
In order to obtain a transparent and dimer-free Ormosil embedded with orgainc dye variations of gel struc-ture and optical properties were studied as a functiion of the change of gel composition. The Ormosils which have good optical property were produced in the 90/10 ratio of TEOS/PDMS and the structural variations of the gel were achived by the change of ratio of HCl/TEOS. As the ratio of HCl/TEOS was increased pore size of the Ormosil enlarged and porosity increased. Increasing HCl concentration led to gradually lower trans-mittance values. In the xerogel doped with the organic dye Rhodamine 6G perchlorate a dimer peak near 500nm was observed with the increase of the ratio of HCl/TEOS 투광성이 좋고 dimer의 형성이 억제되는 유기염료의 기저체를 얻기 위해 Ormosil(organically modified silicate)제조시에 출발물질 및 촉매의 조성을 변화시켰으며 이 각각의 조성에 따른 미세구조의 변화가 광학특성에 미치는 영향에 대한 연구가 수행되었다. 광학적 응용이 가능한 Ormosil의 TEOS/PDMS 비는 90/10이었으며 겔의 미세구조 변화는 HCI/TEOS의 비를 조절하여 달성하였다. 이 HCI/TEOS의 비가 증가될수록 그 복합체의 기공은 커졌으며, 기공률은 증가되었다. 또한 이 비의 증가에 따라 투광성이 감소되었다. 이러한 특성변화를 가지는 기저체에 염료인 Rhodamice 6G perchlorate(Rh6Gp)를 첨가하면 HCI/TEOS의 비가 증가할수록 monomer에 대한 dimer 피크의 강도가 증가되었다.
김재동,김구대,문지웅,김창은,이해원 한국세라믹학회 1998 한국세라믹학회지 Vol.35 No.9
Interface reaction between LSMC and YSZ is discussed with chemical composition of LSMC. The reac-tivity between LSMC and YSZ increased with increasing Co amount and A-site deficient perovskite is very effective on reducing reactivity. The (La0.8Sr0.2)xMn0.8Co0.2O3 (X=0.9-1) composition is not reactive with YSZ in experimental range. The electrode reaction reaction resistance increases due to reaction product.