• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.139-139
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• 2010

LSM is widely used as a cathode material in SOFC, because of its high electrochemical activity, good stability and compatibility with YSZ electrolyte at high temperature. However, LSM in traditional cathode materials will not generate a satisfactory performance at intermediate temperature. In order to reduce the polarization resistance of cell with the operating temperature of SOFC system, the cathode material of LSCF is one of the most suitable electrode materials because of its high mixed ionic and electronic conductivity. In this report, cathode material, $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ powder for intermediate temperature SOFC was synthesized by Pechini method using the starting materials such as nitrate of La, Sr, Co and Fe including ethylene glycol, etc. As a result, the synthesized powder that calcined above $700^{\circ}C$ exhibits successfully perovskite structure, indicating phase-pure of LSCF. Moreover, the particle size, surface area, crystal structure and morphology of the synthesized oxide powders were characterized by SEM, XRD, and BET, etc. In order to evaluate the electrochemical performance for the synthesized powder, slury mixture using the synthesized cathode material was coated by screen-printing process on the anode-supported electrolyte which was prepared by a tape casting method and co-sintering. Finally, electrochemical studies of the SOFC unit cell, including measurements such as power density and impedance, were performed.

• 공업화학
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• 제10권5호
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• pp.748-753
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• 1999

아크릴아마이드계 단량체와 실리콘분말의 혼합 슬러리를 이용한 겔캐스팅법에 있어서 단량체의 혼합비, 각종 첨가제(고분자 중합 개시제, 촉매, 분산제)의 양, 실리콘 분말 함량, 건조시 습도 등과 같은 화학적 변수가 점도, 겔화시간 등 성형변수와 성형체의 수축율과 강도에 미치는 영향을 조사하였다. 겔화시간은 개시제와 촉매의 양이 증가할수록 단축되지만 개시제의 양에 대한 의존성이 더 크게 나타났고, 슬러리의 겔화시간은 단량체용액에 비해 약 1/2 이하로 대폭 감소되었으며, 가교제 MBAM 비율이 높을수록 겔화는 지연되었다. 또한 분산제의 함량이 0.6 wt % 이상일 때는 슬러리의 유동성이 낮아졌다. 성형체는 98%의 높은 습도 하에서 300시간 이상 건조 처리할 때 7% 이하의 균일한 수축에 의해 균열과 뒤틀림 현상이 발생하지 않았으며 40, 50 vol % 실리콘 분말을 함유한 건조 겔체는 각각 평균 64 MPa, 36 MPa의 강도를 보였다.

• 한국재료학회지
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• 제21권8호
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• pp.444-449
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• 2011

Nano-sized $Y_2O_3$ powders were prepared via a sol-gel method starting with $Y(NO_3)_3{\cdot}6H_2O$ (Yttrium(III) nitrate hexahydrate) and water with ethanol as a cosolvent. $Y_2O_3$ is an important rare earth oxide and has been considered for use in nuclear applications, such as ceramic materials, due to its excellent optical and refractory characteristics. It has been used as a chemically stable substrate, a crucible material for melting reactive metals, and a nozzle material for jet casting molten rare earth-iron magnetic alloys. Oxalic acid ($C_2H_2O_4$) has been adopted as a chelating agent in order to control the rate of hydrolysis and polycondensation, and ammonia was added in order to adjust the base condition. The synthesized $Y_2O_3$ powder was characterized using TG/DTA, XRD, FE-SEM, BET and Impedance Analyzer analyses. The powder changed its properties in accordance with the pH conditions of the catalyst. As the pH increases according to the FE-SEM, the grain grew and it showed that the pore size decreased while confirming the effect of the grain size. The nano-material $Y_2O_3$ powders demonstrated that the surface area was improved with the addition of oxalic acid with ammonium hydroxide.

• 한국분말재료학회지
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• 제17권4호
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• pp.312-318
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• 2010

High speed steels (HSS) were used as cutting tools and wear parts, because of high strength, wear resistance, and hardness together with an appreciable toughness and fatigue resistance. Conventional manufacturing process for production of components with HSS was used by casting. The powder metallurgy techniques were currently developed due to second phase segregation of conventional process. The powder injection molding method (PIM) was received attention owing to shape without additional processes. The experimental specimens were manufactured with T42 HSS powders (59 vol%) and polymer (41 vol%). The metal powders were prealloyed water-atomised T42 HSS. The green parts were solvent debinded in normal n-Hexane at $60^{\circ}C$ for 24 hours and thermal debinded at $N_2-H_2$ mixed gas atmosphere for 14 hours. Specimens were sintered in $N_2$, $H_2$ gas atmosphere and vacuum condition between 1200 and $1320^{\circ}C$. In result, polymer degradation temperatures about optimum conditions were found at $250^{\circ}C$ and $480^{\circ}C$. After sintering at $N_2$ gas atmosphere, maximum hardness of 310Hv was observed at $1280^{\circ}C$. Fine and well dispersed carbide were observed at this condition. But relative density was under 90%. When sintering at $H_2$ gas atmosphere, relative density was observed to 94.5% at $1200^{\circ}C$. However, the low hardness was obtained due to decarbonization by hydrogen. In case of sintering at the vacuum of $10^{-5}$ torr at temperature of $1240^{\circ}C$, full density and 550Hv hardness were obtained without precipitation of MC and $M_6C$ in grain boundary.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.205-206
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• 2006

(BaSr)$TiO_3$ thick films were prepared by tape casting method, using $BaTiO_3$ and $SrTiO_3$ powder slurry in order to investigate dielectric properties. With MgO additives, the sintering density was 5.8 $g/cm^3$ and the BST sample exhibited the maximum dielectric constant, tunability at temperatures near phase transition point. Dielectric loss be on the decrease because the interface is not a pore. BST sample be applicable on tunable device.

• Progress in Superconductivity
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• 제1권1호
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• pp.56-60
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• 1999

Ultra fine MgO particles added BSCCO tapes were fabricated by tape casting using Doctor Blade Method and enclosed by silver foil for different starting compositions (that is, 2223 major, 2212 major). In order to obtain optimum microstructure, thermomechanical treatment was done. Microstructure and phase were analyzed by XRD, SEM and DTA. The critical current density was measured under magnetic field at 77K. The tapes fabricated from the precursor powder with BSCCO-2223 phase (>90%) result in a microstructure with a larger grain size and higher transport critical current density value under magnetic field at given thermomechanical treatment conditions.

• Food Science and Biotechnology
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• 제14권1호
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• pp.112-116
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• 2005

Composite films were prepared with soy protein isolate (SPI) and various clay minerals by casting from polymer and clay water suspension. Effects of clay minerals on film thickness, moisture content (MC), tensile strength (TS), elongation at break (E), water vapor permeability (WVP), and water solubility (WS) were tested. Properties including thickness, surface smoothness, and homogeneity of films prepared with organically modified montmorillonite (O-MMT), Wamok clay (W-clay), bentonite, talc powder, and zeolite were comparable to those of control SPI films. TS increased significantly (p<0.05) in films prepared with O-MMT and bentonite, while WVP decreased significantly (p<0.05) in bentonite-added films. WS of most nanocomposite films decreased significantly (p<0.05).

• 한국세라믹학회지
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• 제36권7호
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• pp.773-781
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• 1999

A new technique to fabricate complex-shaped mullite has been developed through gelcasting without organic binder. The suspension of a commercial mullite powder and boehmite-SiO2 sol as binder was elecrtrosterically stabilized. Ammonium polymetharylyate was employed as a dispersant for the electrosteric stabilization. Complex-shaped bodies were made through casting and gelation at room temperature. The green bodies were dried at a temperature of 30$^{\circ}C$ and relative humidity of 98% without crack development. The dried bodies were then pressureless-sintered at 1650$^{\circ}C$ for 2 h to get a relative density of 98% The Vickers hardness and 4-point flexural strength of sintered parts were 11.0 GPa and 150MPa respectively which are similar to those of commercially available sintered mullite.

• 한국세라믹학회지
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• 제28권12호
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• pp.943-952
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• 1991

Lead zirconate titanate(PZT) powders and thin films were prepared from an alkoxide-based solution by sol-gel method. Gelation of synthesized complex solutions, pyrolysis and crystallization behaviors of the dried powder were studied in accordance with a water content and a catalyst. PZT thin films were formed by spin-casting method on silicon and platinum substrates, and characterized. Ester produced from the reactions was completely removed when drying of the gel was finished. Pyrolysis property of the dried PZT gels were changed in order water content, class of catalyst, and quantity of catalyst. Crystalline Pb phase was transiently formed near 250$^{\circ}C$. Basic catalyst is good additive for a formation of perovskite phase in the films, and acidic catalyst for a densified film structure. By the analysis of RBS, Pb element in the PZT films were diffused into silicon substrate, and the pores, may be produced due to local densification around some grains in the films, make an origin of fault in microstructure when holding time goes to be longer at 700$^{\circ}C$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기물성,응용부문
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• pp.7-9
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• 2006

$(BaSr)TiO_3$ thick films were prepared by tape casting method using $BaTiO_3$ and $SrTiO_3$ powder slurry in order to investigate dielectric properties and low temperature sintering. Sintering density was $5.7\;g/cm^3$ and the BST sample exhibited the maximum dielectric constant, tunability at temperatures near phase transition point. The dielectric constant was increased and curie temperature was shifted to higher temperature with increasing of annealing temperature.