• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.594-597
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• 2003

In the present study, the piezoelectricity and polarization of multilayer ceramic actuator, being designed to stack PMN-PZ-PT ceramic layers and Ag-Pd electrode layers alternatively, were investigated under a consideration of geometric factor, the volume ratio of the ceramic to the electrode layers. The actuators were fabricated by tape casting of 0.2Pb(Mg1/3Nb2/3)O3-0.38PbZrO3-0.42PbTiO3 followed by lamination and burnout & co-firing processes. The actuators of 10 10 0.62 nm3 in size were formed in a way that 60 200 m thick ceramics were stacked alternatively with 5 m thick electrode layer. Increases in polarization and electric field-induced displacement with thickness of the ceramic layer were attributed to change of 90o/180o domain ratio, which was affected by interlayer internal stress. The piezoelectricity and actuation behaviors were found to depend upon the volume ratio (or thickness ratio) of ceramic to electrode layers.

• 한국세라믹학회지
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• 제46권6호
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• pp.602-608
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• 2009

The yield is increasing as the manufacturing technology of ceramics progresses, however, there are many ceramics of poor quality due to variables upon producing ceramics. Some of those waste ceramics are recycled by sanitary ware or tile manufacturers, but most of them are filled in making environmental problem. Therefore, a research begins to recycle waste ceramic ware as alternative to some imported ceramic ware materials and to reduce environmental pollution. This study, succeeding last study which applied waste white ware as ceramic body material, aimed to solve problems of environment and materials by recycling waste ceradon generated in specially formed areas for ceramic in Gyeonggi-do such as Icheon, Yeoju and Gwangju as the ceramic body material. Consequently, the addition of waste ceramic ware into the ceramic body was judged to have limit up to 30% according to plasticity measurement. As we added shredded waste ceramic ware as much as 30% into basic ceramic body and checked its features, the pore rate and absorption rate were good to be average 4% and 3% respectively. In addition, it showed strength more than 720 kgf/$cm^2$ which is higher than existing ceradon body on the market with good sinter state; so it is judged to be available or developed as new ceramic body.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.230-235
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• 2000

The extrusion process for long-length multi-filaments of BSCCO 2223 superconductor tape has been investigated with aids of Finite Element Method and experimental inspection. Since the arrangement of filaments in matrix material has characteristic of rotational symmetry, a 2-dimensional commercial FEM package, DEFORM-2D, was adopted to simulate extrusion process with different variables such as hardness of sheath material, lengths of each filament and arrangement. From the FEM analysis, since the inner filaments move faster than the outer one, distribution of filaments is needed to be optimized. In the case of pure Ag matrix, undesirable non-uniform distribution of filament was obtained due to low hardness of sheath material. Dummy sample(brass (sheath) and talc powder(filament)), however, which has relatively high hardness of sheath material, had been produced with desirable results. Therefore, it is necessary to optimize hardness of sheath material, extrusion temperature and billet design.

• Composites Research
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• 제16권5호
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• pp.21-27
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• 2003

선형 압전 이론(theory of linear piezoelectricity)을 이용하여 면외전단 충격(anti-plane shear impact)을 받는 기능경사 압전 세라믹(functionally graded piezoelectric ceramic)의 중앙에 존재하는 균열(central crack)의 동적 응답에 대해 연구한다. 기능경사 압전재료의 물성치(material property)는 두께방향을 따라 연속적으로 변한다고 가정한다. 라플라스 변환(Laplace transform)과 푸리에 변환(Fourier transform)을 사용하여 두 쌍의 복합적분 방정식을 구성하며, 이를 제2종 Fredholm 적분 방정식(Fredholm integral equations of the second kind)으로 표현한다. 재료 물성치의 변화도(gradient of material properties)와 전기하중(electric loading)의 영향을 보기 위해 동응력세기계수(dynamic stress intensity factor)에 대한 수치 결과를 제시하였다.

• 한국생산제조학회지
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• 제25권4호
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• pp.258-265
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• 2016

Digital printing has been used in various industrial areas, including semiconductor manufacturing and textile printing. However, implications on ceramic textile have not been well established so far. Printing high-viscosity materials requires an understanding of their behavior. An inorganic high viscous material with a viscosity range of 20-30 cps is analyzed using a viscometer and through X-ray diffraction. In this study, a digital printer is designed and assembled using a high-viscosity material with software for PC control, resulting in reduced processing at a fast area velocity of $20m^2/hr$. The present study demonstrated that the printer is capable of controlling the shape of the drop mass to smear ink smoothly onto the ceramic surface under an economic budget. In addition, to avoid any difficulty in color management, the ceramic printer is equipped with an independent color management system designed to cope with images on a highly viscous material.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.294-294
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• 2007

Spinel cathode material $LiMn_2O_4$ is currently studied as a promising cathode material for lithium ion secondary batteries for future applications because of it is low cost, easy to be prepared and capable to be operated in high voltage range. However as a cathode material, $LiMn_2O_4$ performs a poor capacity retention which leads to short cycle life. In this study, stoichiometric $LiMn_2O_4$ was synthesized with granulation method with ion substitution to stabilize its structure and niobium doping to improve its conductivity. These well-mixed powders were calcined at $850^{\circ}C$ for 6 hours and its properties were investigated. Correlations of dopant and electrochemical properties were examined as well.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.3.1-3.1
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• 2009

Normal sintering process of producing porous ceramics is not to sinter perfectly, i.e., stop sintering in middle-process. Our porous ceramic materials are a product of complete sintering. For example if one want to make a porous carborundum, raw carborundum powder is sintered at either lower temperatures than normal sintering temperature or shorter sintering periods than normal sintering time to obtain incompletely sintered materials, i.e., porous carborundum. This implies normally sintered porous ceramic materials can mot be used in high vacuum conditions due to dust coming out from uncompleted sintering. We could produce completely sintered porous ceramic materials. For example, we can produce porous carborundum material by using carborundum particles bonded by glassy material. The properties of this material are similar to carborundum. We could make quasi-zero thermal expansion porous material by using carborundum and particles of negative thermal expansion materials bonded by the glassy material. We apply to sinter them also by microwave to sinter quickly. We also use HIP process to introduce closed pores. We could sinter them in large size to produce $2.5m{\times}2.5m$ ceramic plate to use as a precision plate for flat display industries. This flat ceramic plate is the world largest artificial ceramic plate. Precision plates are basic importance to any advanced electronic industries. The produced precision plate has lower density, lower thermal expansivity, higher or similar damping properties added extra properties such as vacuum vise, air sliding capacity. These plates are highly recommended to use in flat display industries. We could produce also cylindrical porous ceramics materials, which can applied to precision roller for polymer film precision motion for also electronic industries.

• The Journal of Advanced Prosthodontics
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• 제13권1호
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• pp.36-45
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• 2021

Purpose. To investigate the fracture resistance of monolithic CAD-CAM all-ceramic surveyed crowns with two different occlusal rest seat designs. Materials and Methods. Two maxillary first premolar were prepared for all-ceramic surveyed crowns with wide (2/3rd of buccolingual width of an unprepared tooth) or narrow (1/3rd of buccolingual width of an unprepared tooth) disto-occlusal rest seat (ORS) designs. Eighty monolithic CAD-CAM all-ceramic surveyed crowns were prepared and divided into 4 groups - Group CR, Composite resin material as a control; Group LDS, Lithium disilicate based material; Group ZIPS, zirconia-material (IPS ZirCAD); and Group ZLHT, zirconia- material (CeramillZolidht+). Crowns were cemented on an epoxy resin die with adhesive resin cement. The fracture resistance of crowns was tested with the universal machine. Univariate regression analysis was used. Results. The mean ± standard deviation of maximum failure force values varied from 3476.10 ± 285.97 N for the narrow ORS subgroup of group ZIPS to 687.89 ± 167.63 N for the wide ORS subgroup of group CR. The mean ± standard deviation of maximum force was 1075 ± 77.0 N for group CR, 1309.3 ± 283.9 N for group LDS, 3476.1 ± 285.97 N for group ZIPS, and 2666.7 ± 228.21 N for group ZLHT, with narrow occlusal rest seat design. The results of the intergroup comparison showed significant differences in fracture strength with various material groups and occlusal rest seat designs (P<.001). Conclusion. The zirconia-based all-ceramic surveyed crowns fractured at more than double the load of Lithium disilicate based crowns. The crowns with narrow base occlusal rest seat design had statistically significantly higher fracture resistance than surveyed crowns with wide occlusal rest seat design. The use of narrow occlusal rest seat design in CAD-CAM all ceramic surveyed crowns provides higher fracture resistance, and therefore narrow occlusal rest design can be used for providing esthetics with high strength.

• 한국결정성장학회지
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• 제28권6호
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• pp.229-234
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• 2018

조핵제 역할을 하는 지르코늄의 원료로써 $ZrO_2$(지르코늄 옥사이드), $ZrSiO_4$(지르코늄 실리케이트), $ZrOCl_2$(지르코늄 옥시클로라이드), $Zr(SO_4)_2$(지르코늄 서페이트) 4종류의 원료를 사용하여 $Li_2O-Al_2O_3-SiO_2$계 결정화 유리를 제조하였다. 동일한 조성의 모든 유리에서 Avrami 상수는 3 이상으로 체적 결정화가 진행됨을 확인하였다. 또한 $ZrOCl_2$, $Zr(SO_4)_2$를 사용하여 제조한 유리는 용융 과정에서 미용융물이 발생하지 않으며 지르코늄 성분이 균일하게 분포되었음을 확인하였다. 이와 같은 결과를 성분 분석, 굽힘 강도를 연계하여 평가하였다.

• 한국세라믹학회지
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• 제43권5호
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• pp.315-319
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• 2006

There have been some studies on the use of coal waste as a raw material for clay bricks due to the lack of naturally producing minerals. It can help resolving the problems of pollution, forest conservation and flood control by utilizing coal waste. However, high content of carbon materials usually leads to the black core in clay bricks after firing process, and diminishes the mechanical and aesthetical properties of clay brick. In this study, the effect of firing process is investigated for the removal of black core in clay bricks with carbon content. The removal kinetics of black core are also compared and investigated with the firing schedule and black core removal.