• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.151.1-151
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• 2002

• Proceedings of the KIEE Conference
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• 1985.07a
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• pp.189-190
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• 1985

• Journal of the Korean Chemical Society
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• v.21 no.2
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• pp.121-124
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• 1977

A study on the formation of black iron oxide was carried in differents of Fe(III), Fe(II) ion in the aqueous solution that iron(II) sulfate was calcined under various temperature and leached in water. The results obtained was follows; (1) It was found that the sample calcined in an electric muffle furnace maintained at $500^{\circ}C$ for 1 hour and leached in water was equivalent mole (Fe(III) /Fe(II) = 1) in 20% aqueous solution. (2) When the above mentioned solution was hydrolyzed at pH range of 7 to 8 for 2 hours at $100^{\circ}C$, 93% and over of iron was recovered in the form of ${\alpha}-Fe_3O_4$ with a black colour.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.137-141
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• 1999

금속 다층박막과 미세입상 합금박막에서 발견된 Giant Magnetoresistance(GMR) 현상에 고무되어 최근에는 50년대에 밝혀졌던 산화물 자기저항 재료에 관하여 새롭게 연구하고 있으며 perovskite 구조를 가지는 La$_{1-x}$ Ca/xub x/MnO$_{3}$ 박막에서 큰 자기저항을 얻었으며 이를 Colossal Magentoresistance (CMR) 이라 부른다. 본 연구에서는 La$_{1-x}$ Ca/xub x/MnO$_{3}$ 분말을 하소온도를 700-90$0^{\circ}C$로 변화시킨 고상반응법과 자발착화연소합성법(Glycine-Nitrate Process) 으로 각각 제조하였으며 비교 분석하였다. TG-DTA을 이용하여 불순물과 미반응 물질을 확인하여 적당한 하소 온도를 결정하였고 XRD를 이용하여 결정상을 분석하였다. 주사전자현미경(SEM)으로 각각 제조된 분말의 하소후 입자의 크기를 비교하였다. GNP법으로 합성한 경우가 고상반응법을 이용한 경우보다 입자의 크기가 submicron 단위로 미세하고 균질하며 고순도의 perovskite 구조를 갖는 La$_{1-x}$ Ca/xub x/MnO$_{3}$ 분말을 얻을 수 있었다.었다.

• Korean Journal of Materials Research
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• v.10 no.3
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• pp.191-198
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• 2000

A serpentine mineral was treated in hydrochloric acid solution to obtain amorphous silica residue with high surface area. The highly porous silica with aluminum hydroxide and sodium hydroxide was hydrothermally reacted in an autoclave. A numerous experiments were performed in terms of reaction time, temperature, alkalinity, and calcinations temperature. As a result, a ZSM-5 zeolite of the highest crystallinity was produced under such conditions as $^170{\circ}C$ of the reaction temperature, 24 hours of the reaction time, and $11.7Na_2O{\cdot}Al_2O_3{\cdot}90SiO_2{\cdot}3510H_2O{\cdot}10.8(TPA)_2O$ the composition along with 3 hours of the calcinations at $600^{\circ}C$.

• Electrical & Electronic Materials
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• v.6 no.6
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• pp.537-544
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• 1993

기본조성이 0.5[Pb(Ni$_{1}$3/Nb$_{2}$3/)O$_{3}$]-0.5[0.65PbTiO$_{3}$ -0.35PbZrO$_{3}$] (PNN-PT-PZ)인 압전세라믹스를 NaCl-KCI를 사용한 flux의 양 및 소결온도에 따른 생성반응과 소결특성, 유전 및 압전특성을 조사하였다. 이때 1몰의 산화물에 대한 flux의 양은 0.1, 2 및 5mole로 하였으며 소결온도는 1000-1200.deg.C로 하였다. 본 연구의 flux법은 고상반응법에 비해 낮은 하소온도에서 pyrochlore상을 현저히 줄일수 있었으며 고상반응법보다 낮은 온도에서 치밀화가 이루어질뿐 아니라 유전 및 압전특성을 개선할 수 있었으며 소결온도도 낮출 수 있었다. Flux의 양이 증가할수록 결정의 입성장이 빨랐으며 유전 및 압전특성이 가장 좋은 flux의 첨가량의 조건은 1mole이었다.

• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.441-446
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• 2003

Fine powders of ZnO were synthesized by the sol-gel method. The shape of gel powders with calcination temperatures changed into the sheet structure, the needle shape, and the spherical grain. The growth rate of grain size was slow to 700$^{\circ}C$ but high above 700$^{\circ}C$. The bigger the grain size is, the higher the degree of crystallization is. The organic element in gel powders evaporated below 300$^{\circ}C$. Temperature dependence of conductances showed the sigmoidal shape, but the temperature range of the constant conductances narrowed with the decrement of the calcination temperature of gel powders. The optimum sensing property for CO gas were observed with the specimen calcined at 500$^{\circ}C$ and degraded with the increment of calcination temperature.

• Applied Chemistry for Engineering
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• v.23 no.6
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• pp.534-538
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• 2012

$Na^+$-beta-alumina solid electrolyte was synthesized by solid state reaction using $Li_2O$ and MgO as a phase stabilizer, and the effect of stabilizers on the phase formation and sintering density was investigated. In order to determine the phase fraction according to the synthesizing temperature, the molar ratio of [$Na_2O$] : [$Al_2O_3$] was fixed at 1 : 5, and calcination was conducted at temperatures between $1200{\sim}1500^{\circ}C$ for 2 h. In the $Li_2O$-$Na_2O$-$Al_2O_3$ ternary system, ${\beta}^{{\prime}{\prime}}$-alumina phase fraction considerably increased by the secondary phase transition at $1500^{\circ}C$, whereas it maintained similarly in the MgO-$Na_2O$-$Al_2O_3$ system. Additionally, the disc-type specimens of $Na^+$-beta-alumina were sintered at the temperature between $1550{\sim}1650^{\circ}C$ for 30 min, and relative sintering densities, phase changes, and microstructures were analyzed. In case of $Li_2O$-stabilized $Na^+$-beta-alumina, ${\beta}^{{\prime}{\prime}}$-phase fraction and relative density of specimen sintered at $1600^{\circ}C$ were 94.7% and 98%, respectively. Relative density of MgO-stabilized $Na^+$-beta-alumina increased with a rise in sintering temperature.

• Journal of Sensor Science and Technology
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• v.6 no.4
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• pp.316-327
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• 1997

Polycrystalline $Sr_{2}Nb_{2}O_{7}$ and $La_{2}Ti_{2}O_{7}$ ceramics with very high Curie temperatures were synthesized by the chemical coprecipitation method (CCP). The powders synthesized were identified by XRD and their sintering behavior and physical properties were studied. The grain-orientation and electrical properties of sintered ceramics were investigated as a function of firing temperature. Single phase could be obtained by CCP method at temperature lower than that of the conventional method by 100 - $150^{\circ}C$. Strontium niobate, $Sr_{2}Nb_{2}O_{7}$, powder was Prepared by CCP method at temperatures as low as $800^{\circ}C$ via intermediate phase of $Sr_{5}Nb_{4}O_{15}$ formed at $700^{\circ}C$. The resulting CCP-derived powder was observed to have finer and more uniform particle size distribution than those obtained through the conventional or the molten salt synthesis method. Sintering of CCP-derived $Sr_{2}Nb_{2}O_{7}$ powder at $1500^{\circ}C$ yielded a highly dense ceramics with 97% theoretical density. Very high grain-orientation developed along the (0k0) direction was observed by SEM, which resulted in anisotropic dielectric properties of the sintered samples, with the dielectric constant values approaching those for single crystal.

• Electrical & Electronic Materials
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• v.4 no.3
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• pp.201-210
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• 1991

본 논문에서는 (B $i_{1-x}$ P $b_{x}$)$_{2}$S $r_{2}$C $a_{2}$C $u_{3.6}$ $O_{y}$ (x=0~0.5)로 조성된 분말의 최적 하소온도를 결정하고 시편의 최적 소결온도를 규명하기 위하여 열분석을 하였다. 또 단일상의 고온 초전도체를 제작하기 위하여 열처리 온도, 시간 및 Pb 함량 변화에 따라 제작된 시편의 미세구조, 조성, 전기저항 및 전류밀도를 측정하여 상호 연관성을 종합적으로 분석, 검토하여 상변이에 관한 원인을 규명하고자 하였다. 또한 실용화 전 단계로서 임계특성 해석을 위하여 성형조건을 변화시켜 시편을 제작, 전류밀도값을 측정하였다.였다.다.