• 한국대기환경학회지
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• 제12권2호
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• pp.131-139
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• 1996

The developent of ceramic combustor is being increased beca- use of the excellent physical properties of ceramic material, that is, high-resistant strength, high emissivity power and high corrosin-resistance. Ceramic combustor has been interested in the application of ultra-lean combustion for low NO$_{x}$ emission and gaseuos waste incineration with good combustion. This experimental study was conducted to investigate the combustion and emission characteristics of wall recess type ceramic combustor with equivalence ratio, mixture flow velocity and wall recess depth as parameters. The results in this study are as follows: 1. Wall recess played a important role to extend flame stability region. 2. The peak temperature of gas was peoportional to equivalence ratio, mixture flow velocity and wall recess depth. 3. The static pressure of mixing chamber and inlet temperature depended on the position of flame zone. 4. NO reduction was achieved by lean mixture without lower combustibility.y.

• 한국연소학회지
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• 제14권3호
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• pp.24-28
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• 2009

To improve its efficiency, most of the industrial furnace had been used recuperator. However, commonly used metal recuperator is not suitable under condition of temperature higher than $1000^{\circ}C$. The other hand, ceramic recuperator is able to use in high temperature condition. In the present study, the design program based on the basic heat exchanger design theory, and CFD modelling are applied to ceramic recuperator to verify the design results. Using design program to find the optimum design factor on the variation of recuperator condition. The result of this study are as follows : Thinner fin-plate thickness reduces pressure drop and increases heat-transfer rate, However, thin plate or plate with thin thickness(< 5 mm) is difficult to manufacture, due to limited mechanically strength.

• 한국전기전자재료학회논문지
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• 제29권8호
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• pp.476-482
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• 2016

Convectional PZT based piezoelectric ceramics have to sinter at high temperature about $1,200^{\circ}C$ for their suitable electrical properties. However, some issues: low temperature sintering piezoelectric ceramic composition and reliable internal electrode, have recently attracted a great deal of interest as a highly efficient multi-layered piezoelectric ceramics. In order to optimize low temperature sintering conditions of thick-film PMN-PZ-PT ceramic, it was investigated sintering and piezoelectric properties according to the change of $LiBiO_2$ contents. Thus, the superior piezoelectric properties were found at the pallet type PMN-PZ-PT optimized with low sintering processing at $925^{\circ}C$ including 7 wt% $LiBiO_2$ sintering aid. Consequentially, we successfully manufactured thick-film PMN-PZ-PT ceramics, which had superior piezoelectric and dielectric properties, with 5 wt% of $LiBiO_2$ sintering aid at temperature of $900^{\circ}C$.

• 한국세라믹학회지
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• 제33권2호
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• pp.192-202
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• 1996

In Li0.4Ca0.05AlP0.5Si0.75O4.5 composition glass, glass-ceramic having a near 100% crystallinity after nucleation heat treatment of 74$0^{\circ}C$/2 h and crystallization heat treatment of 90$0^{\circ}C$/2 h and in-situ TiO2 whisker reinforced glass-ceramic after heat treatment of 105$0^{\circ}C$ for 20 h were fabricated with the addition of 4% TiO2 as a nucleating agent. With these materials a ball-on-disc type wear test was conducted in order to examine the effect of TiO2 whisker prepcipitation on ambient and high temperature wear properties of the glass-ceramic. Wear test results indicated that all specimens exhibited micro-fracture wear mechanism in ambient temperature. As temperature increased the wear rates of the materials were increased. However the in-situ TiO2 whisker reinforced glass-ceramic exhibited the lowest wear rate over the test temperature range. This resulted from the improvement of harness and fracture toughness of the material as the glass converted into the glass-ceramic followed by precipitation of TiO2 whiskers throughout the glass-ceramic matrix.

• Structural Engineering and Mechanics
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• 제4권6호
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• pp.679-702
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• 1996

The finite element method is employed in conjunction with micromechanical modelling in order to assess the performance of ceramic thermal barrier coatings applied to structural components. The study comprises the conditions of the deposition of the coating by plasma spraying as well as the thermal cycling of the coated component, and it addresses particularly turbine blades. They are exposed to high temperature changes strongly influencing the behaviour of the core material and inducing damage in the ceramic material by intense straining. A concept of failure analysis is discussed starting from distributed microcracking in the ceramic material, progressing to the formation of macroscopic crack patterns and examining their potential for propagation across the coating. The theory is in good agreement with experimental observations, and may therefore be utilized in proposing improvements for a delayed initiation of failure, thus increasing the lifetime of components with ceramic thermal barrier coatings.

• 한국세라믹학회지
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• 제53권5호
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• pp.568-573
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• 2016

We explore the crystalline structure and phase transition of lithium thiophosphate ($Li_7P_3S_{11}$) solid electrolyte using electron microscopy and X-ray diffraction. The glass-like $Li_7P_3S_{11}$ powder is prepared by the high-energy mechanical milling process. According to the energy dispersive X-ray spectroscopy (EDS) and selected area diffraction (SAD) analysis, the glass powder shows chemical homogeneity without noticeable contrast variation at any specific spot in the specimen and amorphous SAD ring patterns. Upon heating up to $260^{\circ}C$ the glass $Li_7P_3S_{11}$ powder becomes crystallized, clearly representing crystal plane diffraction contrast in the high-resolution transmission electron microscopy image. We further confirm that each diffraction spot precisely corresponds to the diffraction from a particular $Li_7P_3S_{11}$ crystallographic structure, which is also in good agreement with the previous X-ray diffraction results. We expect that the microscopic analysis with EDS and SAD patterns would permit a new approach to study in the atomic scale of other lithium ion conducting sulfides.

• Composites Research
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• 제35권4호
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• pp.261-268
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• 2022

ZrB₂, ZrC, HfB₂, HfC 및 SiC 등의 초고온 세라믹스(UHTC, ultra-high temperature ceramics)들은 최근 주목 받고 있는 극초음속 체계 및 차세대 우주왕복선 등에 적용하기 위하여 최근 활발한 연구가 진행되고 있다. 본 논문에서는 한국, 중국, 미국, 일본 및 EU 등지에서 최근 5년간 발표된 주요 연구 결과들을 위주로 간략히 소개하였다. 또한 초고온 세라믹스의 단점인 취성 문제를 극복하기 위한 세라믹 섬유강화 복합재료 제조를 목적으로 Horizon 2020 프로그램의 일환으로 범 유럽차원에서 공동연구로 수행된 C³HARME 프로젝트의 내용 및 결과를 간략히 보고하였다.

• 반도체디스플레이기술학회지
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• 제21권1호
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• pp.119-126
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• 2022

MAS-based glass, which has been studied to replace the ceramic material used in the plasma etching chamber, has problems such as forming and processing due to its high melting temperature. To solve this problem, in this study, fluoride was added to the existing MAS-based glass to increase the workability in the glass manufacturing and to improve the chemical resistance to CF₄/Ar/O₂ plasma gas. Through RAMAN analysis, the structural change of the glass according to the addition of fluoride was observed. In addition, it was confirmed that high-temperature viscosity and thermal properties decreased as the fluoride content increased and plasma resistance was maintained, it showed an excellent etching rate of up to 11 times compared to quartz glass.

• 한국세라믹학회지
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• 제50권6호
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• pp.470-475
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• 2013

In this study, we report that effects of a filler with a high coefficient of thermal expansion on a sealant for high-temperature ($750{\sim}850^{\circ}C$) SOFC. We designed a $SiO_2-BaO-ZnO-B_2O_3-Al_2O_3$ glass system with a softening temperature higher than $750^{\circ}C$. The properties of the glass system show not only low volumetric shrinking but also low swelling. The glass system did not create a crystal phase during along-term heat treatment. We fabricated a seal gasket with 0, 10, 15, and 20 wt% cristobalite added as filler materials with glass powder. The coefficient of thermal expansion of the seal gasket increased according to cristobalite content. During along-term heat treatment, the leak rate decreased by about 5% after a heat treatment in an oxidizing atmosphere at $750^{\circ}C$ for 2000 h, also decreasing by about 6% after a heat treatment in a reducing atmosphere at $750^{\circ}C$ for 1000 h.

• 한국세라믹학회지
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• 제49권6호
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• pp.648-653
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• 2012

Hybridization of dense ceramic membranes for hydrogen separation with an electronically conductive metallic phase is normally utilized to enhance the hydrogen permeation flux and thereby to increase the production efficiency of hydrogen. In this study, we developed a nickel and proton conducting oxide ($BaCe_{0.9}Y_{0.1}O_{3-{\delta}}$: BCY) based cermet (ceramic-metal composites) membrane. Focused on the general criteria in that the hydrogen permeation properties of a cermet membrane depend on its microstructural features, such as the grain size and the homogeneity of the mix, we tried to optimize the microstructure of Ni-BCY cermets by controlling the fabrication condition. The Ni-BCY composite powder was synthesized via a solid-state reaction using $2NiCO_3{\cdot}3Ni(OH)_2{\cdot}4H_2O$, $BaCeO_3$, $CeO_2$ and $Y_2O_3$ as a starting material. To optimize the mixing scale and homogeneity of the composite powder, we employed a high-energy milling process. With this high-energy milled composite powder, we could fabricate a fine-grained dense membrane with an excellent level of mixing homogeneity. This controlled Ni-BCY cermet membrane showed higher hydrogen permeability compared to uncontrolled Ni-BCY cermets created with a conventionally ball-milled composite powder.