• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2008년도 제34회 동계학술대회 초록집
• /
• pp.297-297
• /
• 2008

• 한국세라믹학회:학술대회논문집
• /
• 한국세라믹학회 2002년도 추계총회 및 연구발표회 초록집
• /
• pp.68.2-68
• /
• 2002

• 한국세라믹학회:학술대회논문집
• /
• 한국세라믹학회 2002년도 추계총회 및 연구발표회 초록집
• /
• pp.90.1-90
• /
• 2002

• 한국세라믹학회:학술대회논문집
• /
• 한국세라믹학회 2002년도 추계총회 및 연구발표회 초록집
• /
• pp.71.1-71
• /
• 2002

• 한국세라믹학회지
• /
• 제52권6호
• /
• pp.410-416
• /
• 2015

Recently, a new $Y_2O_3$ coating deposited using the EB-PVD method has been developed for erosion resistant applications in fluorocarbon plasma environments. In this study, surface crack formation in the $Y_2O_3$ coating has been analyzed in terms of residual stress and elastic modulus. The coating, deposited on silicon substrate at temperatures higher than $600^{\circ}C$, showed itself to be sound, without surface cracks. When the residual stress of the coating was measured using the Stoney formula, it was found to be considerably lower than the value calculated using the elastic modulus and thermal expansion coefficient of bulk $Y_2O_3$. In addition, amorphous $SiO_2$ and crystalline $Al_2O_3$ coatings were similarly prepared and their residual stresses were compared to the calculated values. From nano-indentation measurement, the elastic modulus of the $Y_2O_3$ coating in the direction parallel to the coating surface was found to be lower than that in the normal direction. The lower modulus in the parallel direction was confirmed independently using the load-deflection curves of a micro-cantilever made of $Y_2O_3$ coating and from the average residual stress-temperature curve of the coated sample. The elastic modulus in these experiments was around 33 ~ 35 GPa, which is much lower than that of a sintered bulk sample. Thus, this low elastic modulus, which may come from the columnar feather-like structure of the coating, contributed to decreasing the average residual tensile stress. Finally, in terms of toughness and thermal cycling stability, the implications of the lowered elastic modulus are discussed.

• 한국분말재료학회지
• /
• 제24권6호
• /
• pp.437-443
• /
• 2017

SiC-based composite materials with light weight, high durability, and high-temperature stability have been actively studied for use in aerospace and defense applications. Moreover, environmental barrier coating (EBC) technologies using oxide-based ceramic materials have been studied to prevent chemical deterioration at a high temperature of $1300^{\circ}C$ or higher. In this study, an ytterbium silicate material, which has recently been actively studied as an environmental barrier coating because of its high-temperature chemical stability, is fabricated on a sintered SiC substrate. $Yb_2O_3$ and $SiO_2$ are used as the raw starting materials to form ytterbium disilicate ($Yb_2Si_2O_7$). Suspension plasma spraying is applied as the coating method. The effect of the mixing method on the particle size and distribution, which affect the coating formation behavior, is investigated using a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) analysis. It is found that the originally designed compounds are not effectively formed because of the refinement and vaporization of the raw material particles, i.e., $SiO_2$, and the formation of a porous coating structure. By changing the coating parameters such as the deposition distance, it is found that a denser coating structure can be formed at a closer deposition distance.

• 한국결정성장학회지
• /
• 제28권6호
• /
• pp.243-249
• /
• 2018

$1000^{\circ}C$ 이상의 고온 열처리를 통하여 제작되는 도자타일은 우수한 내구성과 표면 유약의 심미성 때문에 건축용 내외장재로 많이 사용되고 있다. 최근 건축용 도자타일 공정에 양산형 잉크젯 프린팅이 빠르게 도입되고 있으며, 이와 관련한 소재(세라믹 잉크, 세라믹 안료, 유약)에 대한 연구가 활발하게 이루어지고 있다. 본 연구에서는 도자타일의 표면 유약의 원료인 고령토(kaolin)를 고에너지 밀링을 이용하여 미립화하였고, 이에 따른 표면 유약의 미세구조 변화가 세라믹 잉크의 인쇄적성에 미치는 영향에 대해 확인하였다. 세라믹 잉크는 자체 제작한 검은색 잉크를 사용하여 도자타일의 표면 유약에 잉크젯 프린팅하였다. 프린팅된 세라믹 잉크 망점의 크기, 진원도를 측정하여 표면 유약의 고령토 미립화에 따른 인쇄적성을 평가하였다. 또한 고령토 미립화에 따른 표면 유약의 거칠기와 내부 미세 기공 분포를 측정하여 표면 유약의 미세구조 변화와 세라믹 잉크의 인쇄적성의 관계에 대해서도 고찰하였다.

• Tribology and Lubricants
• /
• 제21권5호
• /
• pp.216-220
• /
• 2005

The sliding wear behaviors of three different compositions of novel low temperature degradation-free zirconia/alumina (LTD-free Z/A) composites were examined in a ceramic-ceramic contact pair. The wear tests were performed by using a pin-on-disk type wear tester in a linear reciprocal sliding motion with a line contact in both dry and bovine serum lubricated conditions at room temperature. From the results of dry sliding wear tests, Z/A#1((5.3Y, 4.6Nb)-TZP/80 $vol\%Al_2O_3$) showed the best wear resistance among three kinds of LTD-free Z/A composites. For the bovine serum lubricated sliding wear tests, wear was too little to be measured for all kinds of Z/A composites. These novel LTD-free Z/A composites having excellent wear resistance demonstrated a potential as the alternative materials for the ceramic-ceramic contact pairs of femoral head and acetabular liner in total hip replacement.

• 한국세라믹학회지
• /
• 제49권3호
• /
• pp.216-220
• /
• 2012

Mullite formation in a porcelain body was promoted extensively by replacing kaolinite with pyrophyllite. Effects of mullite formation and vitrification by substitution of kaolinite with pyrophyllite on the mechanical and thermal properties were investigated. Addition of 45-55% pyrophyllite (pyrophyllite (45-55%)-feldspar (30%)-Gairome clay (20%)) could vitrify the sintered samples (water absorption : 0.05%, bulk density : 2.66g/cc) and improve the flexural strength (122MPa) when fired at $1280^{\circ}C$. Mullite formation was found to be decreased with increasing content of pyrophyllite. On the contrary, beyond 50% of pyrophyllite quartz and cristobalite phases was found to be increased. Thermal expansion coefficient of the samples decreased with increase of mullite phase. In triaxial system of pyrophyllite-feldspar-clay, the mullite formation of the samples with 50% pyrophyllite reaches about 78.7% and thermal expansion coefficient was found to be $5.4{\times}10^{-6}/K$.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 추계학술대회 논문집
• /
• pp.14-14
• /
• 2009

In this study, we investigated the effects of Cr dopant on the bulk trap level and grain boundary characteristics of $Bi_2O_3$-based ZnO (ZB) using dielectric functions such as $Z^*$, $Y^*$, $M^*$, ${\varepsilon}^*$, and $tan{\delta}$. More than two bulk traps of $Zn_i$ and $V_o$ probably in different ionization states could be identified in ZBCr($ZnO-Bi_2O_3-Cr_2O_3$). The grain boundaries of ZBCr could be electrochemically divided into two types: sensitive to ambient oxygen and thus electrically active one and oxygen-insensitive and thus electrically inactive one.