• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.869-870
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• 2013

• 한국세라믹학회지
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• 제52권1호
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• pp.41-47
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• 2015

Celadon shards from Gangjin and Buan were analyzed for their color, chemistry and microstructures. They exhibited similar chromatic characteristics in a $CIEL^*a^*b^*$ analysis. All of the glazes assessed showed comparable compositional areas, while the bodies from Gangjin shards had higher $RO_2$ concentrations. A high degree of similarity was also noted in the microstructures of the glaze and bodies from both regions. Anorthite crystals appeared in the glaze layer, and phase separation behavior developed around these crystals. This may have been caused by the glaze chemistry and the sintering process given the lengthy heating and cooling time. A Raman analysis indicated higher isolated $SiO_4$ unit ($Q_0$) values for the Buan samples. This can stem from the higher firing temperature or the longer sintering process.

• 한국세라믹학회지
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• 제53권5호
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• pp.506-510
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• 2016

The eutectic melt of BaO-CuO flux is known to be a potential sintering aid for $Ba(Zr,Y)O_3$ (BZY) electrolyte for proton-conducting ceramic fuel cells (PCFCs). A density of BZY higher than 97% of theoretical density can be achieved via sintering at $1300^{\circ}C$ for 2 h using a flux composed of 28 mol% BaO and 72 mol% CuO. In the present study, chemical and structural evolution of BaO-CuO flux throughout the sintering process was investigated. An intermediate holding step at $1100^{\circ}C$ leads to formation of various impurity compounds such as $BaCuO_{1.977}$, $Ba_{0.92}Cu_{1.06}O_{2.28}$ and $Cu_{16}O_{14.15}$, which exhibit significantly larger unit cell volumes than the matrix. The presence of such secondary compounds with large lattice mismatch can potentially lead to mechanical failure. On the other hand, direct heating to the final sintering temperature produced CuO and $Cu_2O$ as secondary phases, whose unit cell volumes are close to that of the matrix. Therefore, the final composition of the flux is strongly affected by the thermal history, and a proper sintering schedule should be used to obtain the desired properties of the final product.

• 한국세라믹학회지
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• 제39권9호
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• pp.822-828
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• 2002

$ZrO_2$ 첨가량 변화에 따른 전기적 특성과 고주파 대용량 세라믹 캐패시터 제조공정 조건을 규명하기 위하여 고주파 대용량 세라믹 캐패시터의 제조 및 전기적 특성에 관하여 연구하였다. 단위 캐패시터는 테이프 캐스팅법으로 제조되었으며, 유전체 및 바인더의 최적조성은 57.5∼60.0: 42.5∼40.0 wt%이다. 슬러리의 점도는 4000∼5000 cps이며, 이 슬러리를 사용하여 제조한 그린 테이프는 뛰어난 캐스팅 상태를 유지하고 있다. 80$^{\circ}C$에서 200 kg/$cm^2$의 성형압으로 성형함으로서 최적의 적층 상태를 얻을 수 있었다. 단위 캐패시터의 전기적 특성, 특히 절연파괴 특성을 증진시키기 위하여 $ZrO_2$를 첨가하였다. $ZrO_2$ 첨가량이 1 wt%에서부터 5 wt%까지 첨가한 경우에는 단위 캐패시터의 유전상수 및 유전손실에 큰 영향을 미치지 못하였다. 또한 유전상수도 10 kHz에서 500 kHz 사이의 주파수 범위에서 큰 변호가 없었다. 내전압은 3 wt%를 첨가한 경우 $CaZrO_3$에 형성 및 입자크기 감소로 인하여 증진됨을 확인할 수 있었다.

• The Korean Journal of Ceramics
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• 제1권1호
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• pp.40-44
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• 1995

Ethylammonium-layered aluminosilicates intercalates were prepared by ion exchange reaction between the layered silicates with different layer changes density of 0.32∼0.41 e per unit formula and ethylammonium chloride. A kinetic study on the thermal deintercalation of the ethylammonium-layered silicate intercalates was carried out by range of 350℃ to 480℃ (heating rate of 10℃/min). Based on the Ozawa's method, the activation energies of the thermal deintercalation reaction were estimated as 171.2∼133.0 kJ/mol, which increase linearly with the layer charge densities.

• Tribology and Lubricants
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• 제22권6호
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• pp.314-319
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• 2006

In this paper, the friction and wear characteristics of contact type sealing unit far a water turbine have been presented. The sealing unit for a small hydropower generation is to stop a leakage of circulating water from an outside of an impeller to an inside of a rolling bearing. The friction heating between a seal ring and a seal seat may radically increase a surface temperature in which increase a power loss and wear on the rubbing surface. The surface wear strongly affect to the seal life of a mechanical face seal. In this study, the hardness of a stainless steel in which is a heat-treated is 892.8 in Victors hardness and the hardness of silicone carbide of SiC is 714.1 in Victors hardness. The surface hardness of a heat-treated stainless steel is 25% high compared with that of a ceramic material of SiC. The contact modes of rubbing surfaces are a dry friction, a water film friction and a mixed friction that is contaminated by a dust, silt, and moistures, etc. These two factors of a contact rubbing modes and a material property are very important parameters on the tribological performance such as a friction and wear between a seal ring and a seal seat in primary sealing unit. The experimental result shows that the surface hardness of a seal material is very important on the friction coefficient and a wear volume. Thus, the results recommend higher hardness of a seal material, which may reduce a friction loss and increase a wear life of primary seal components.