• 한국세라믹학회지
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• 제49권1호
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• pp.124-129
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• 2012

An M-shaped SiC gas igniter was fabricated by a reaction sintering followed by nitrogen doping. The igniter showed both resistivity at room temperature and NTC to PTC transition temperature values that were lower than those of commercial igniters. It was deduced that the doped nitrogen reduces the electrical resistivity at room temperature, while, at high temperature, the doped nitrogen and a trace of $Si_3N_4$ phase work as scattering centers against electron transfer, resulting in a lowered NTC-to-PTC transition point (below $650^{\circ}C$). Such characteristics were correlated to the fast heating speed (as compared to the commercial models) and to the prevention of the high temperature overshooting of the nitrogen-doped SiC igniter.

• 한국분말재료학회지
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• 제16권6호
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• pp.442-448
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• 2009

$ZrB_2$-based composites are candidate materials for ultra-high temperature materials (UHTMs). $ZrB_2$ has become an indispensable ingredient in UHTMs, due to its high melting temperature, relatively low density, and excellent resistance to thermal shock or oxidation. $ZrB_2$ powders are usually synthesized by solid state reactions such as carbothermal, borothermal, or combined carbothermal reaction. SiC is added to this system in order to enhance the oxidation resistance of $ZrB_2$. In this study, $ZrB_2$?based composites were successfully synthesized and densified through two different processing paths. $ZrB_2$ or $ZrB_2$ 25 vol.%SiC was fully synthesized from oxide starting materials with reducing agents after heat treatment at 1400$^{\circ}C$. Besides, $ZrB_2$?20 vol.%SiC was fully densified with $B_4C$ as a sintering additive after hot pressing at 1900$^{\circ}C$. The synthesis mechanism and the effect of sintering additives on densification of $ZrB_2$ ?SiC composites were also discussed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.456-459
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• 2002

This paper describes fabrication and characteristics of ceramic pressure sensor for working at high temperature. The proposed pressure sensor consists of a Ta-N thin-film, patterned on a Wheatstone bridge configuration, sputter deposited onto thermally oxidized Si membranes with an aluminium interconnection layer. The fabricated pressure sensor presents a low temperature coefficient of resistance, high sensitivity, low non-linearity and excellent temperature stability. The sensitivity is 1.097~1.21mV/$V{\cdot}kgf/cm^2$ in the temperature range of $25{\sim}200^{\circ}C$ and the maximum non-linearity is 0.43 %FS.

• 한국세라믹학회지
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• 제13권1호
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• pp.20-24
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• 1976

These are many kinds of self-hardening methods for sand mold using sodium silicate. When sodium silicate solution is mixed with calcium-orthosilicate powder hardening reaction occurs, which is based for self-hardening method at high temperature. The high temperature strength and resicual strength of mold are related to the mole ratio of sodium silicate and the contents of calcium-orthosilicate powder. The results obtained in this study were as follows: 1) The high temperature strength of mold was maximum at about $600^{\circ}C$, and at higher temperature showed lower value on the contrary. 2) The high temperature strength of mold was increased by increasing the amount of sodium silicate having lower mole ratio and high concentration. 3) The residual strength of mold was reduced by increasing the mole ratio of sodium silicate and increasing the concentration of calcium-orthosilicate.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.888-891
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• 2003

This paper describes on the fabrication and characteristics of micro ceramic thin-film type pressure sensors based on Ta-N strain-gauges for high-temperature applications. The Ta-N thin-film strain-gauges are deposited onto thermally oxidized Si diaphragms by RF sputtering in an argon-nitrogen atmosphere($N_2$ gas ratio: 8 %, annealing condition: $900^{\circ}C$, 1 hr.), Patterned on a wheatstone bridge configuration, and use as pressure sensing elements with a high stability and a high gauge factor. The sensitivity is $1.097{\sim}1.21mV/V.kgf/cm^2$ in the temperature range of $25{\sim}200^{\circ}C$ and the maximum non-linearity is 0.43 %FS. The fabricated pressure sensor presents a lower TCR, non-linearity than existing Si piezoresistive pressure sensors. The fabricated micro ceramic thin-film type pressure sensor is expected to be usefully applied as pressure and load sensors that is operable under high-temperature environments.

• 한국세라믹학회지
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• 제46권2호
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• pp.146-154
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• 2009

It is necessary to minimize the thickness of Ni inner electrode layer and to improve the coverage of inner electrode, for the purpose of developing the ultra high-capacity multi layered ceramic capacitor (MLCC). Thus, low temperature sintering of dielectric $BaTiO_3$ ceramic should be precedently investigated. In this work, the relationship between dielectric properties of MLCC and batch condition such as mixing and milling methods was investigated in the $BaTiO_3$(BT)-Dy-Mg-Ba system with borosilicate glass as a sintering agent. In addition, several chip properties of MLCC manufactured by low temperature sintering were compared with conventionally manufactured MLCC. It was found that low temperature sintered MLCC showed better DC-bias property and lower aging rate. It was also confirmed that the thickness of Ni inner electrode layer became thinner and the coverage of inner electrode was improved through low temperature sintering.

• 한국세라믹학회지
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• 제56권4호
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• pp.331-339
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• 2019

While high-temperature ceramic composites consisting of carbides, borides, and nitrides, the so-called ultra-high-temperature ceramics (UHTCs), have been commonly produced through solid-state sintering, melt-solidification is an alternative method for their manufacture. As many UHTCs are binary or ternary eutectic systems, they can be melted and solidified at a relatively low temperature via a eutectic reaction. The microstructure of the eutectic composites is typically rod-like or lamellar, as determined by the volume fraction of the second phase. Directional solidification can help fabricate more sophisticated UHTCs with highly aligned textures. This review describes the fabrication of UHTCs through the eutectic reaction and explains their mechanical properties. The use of melt-solidification has been limited to small specimens; however, the recently developed laser technology can melt large-sized UHTCs, suggesting their potential for practical applications. An example of laser melt-solidification of a eutectic ceramic composite is demonstrated.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.398-403
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• 2000

Experimental study on the porous ceramic burner for oil burning has been performed. Temperature profile of the combustor and CO and NOx emission have been obtained for with and without porous ceramic plate. It is found that very uniform and high temperature region with porous ceramic plate can be realized due to high radiation emission from the plate and also obtained lower CO and soot particulate emission, when compared to the conventional burner. When this burning method is applied to conventional boiler of small heating capacity, it is found that near 6 and 7 percent increase in thermal efficiency could be obtained without a proper calibration for optimization.

• 한국세라믹학회지
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• 제37권4호
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• pp.302-307
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• 2000

The objective of this study was to investigate the sintering behavior, crystallization characteristic of glass-ceramic and optimal sintering condition on the glass/ceramic composite for fabricating substrate of LTCC. Glass/ceramic composite was made from alumina powder and glass frit, which was composed of SiO2-TiO2-RO-PbO/(R: Ba, Sr, Ca), and was sintered for 0, 30, 60minutes in the temperature range from 700$^{\circ}C$ to 1000$^{\circ}C$. Properties of frit and glass/ceramic compsoite were analyzed by DTA, XRD, SEM and Network Analyzer and so on. Main sintering mechanism was densification occurred above 730$^{\circ}C$ by viscous flow and crystallization starting about 780$^{\circ}C$ affected sintering also. So viscous flow was affected by sintering temperature, duration time, and creation of crystallization phase etc. From this study, it was possible to fabricate glass/ceramic composite by changing sintering temperature and duration time.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.103-108
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• 2000

Since the ceramic/metal joint material is made at a high temperature, the residual stress development when it is cooled from bonding temperature to room temperature due to remarkable difference of thermal expansion coefficient between ceramic and metal. As residual stress at ceramic/metal joints influences the strength of joints, it is important to estimate residual stress quantitatively. In this study, it is attempted to estimate joint residual stress of $Si_3N_4/STS304$ joints quantitatively and to compare the strength of Joints. The difference of residual stress is measured when repeated thermal cycle is loaded under the conditions of the practical use of the ceramic/metal joint. And 4-point bending test is performed to examine the influence of residual stress on fracture strength. As a residual it is known that the stress of joint decreases as the number of thermal cycle increases.