• 한국세라믹학회지
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• 제44권4호
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• pp.219-223
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• 2007

The ionic conductivity of $Li_2O-ZrO_2-SiO_2$ glasses has been designed and analyzed on the basis of a mixture design experiment with constraints. Fitted models for the activation energy and the ionic conductivity are as follows: $Q(kJ/moi)=54.8565x_1+144.825x_2+133.846x_3-170.908x_1x_3-334.338x_2x_3$ $log{\sigma}(300K)=-5.00245x_1-1.17876x_2-15.5173x_3+17.4522x_1x_3$. The electrical properties are very sensitive to the ratio of $Li_2O/SiO_2$. The effect of $ZrO_2$ is less than that of this ratio but $ZrO_2$ component attributes to the reduction of the activation energy. The optimal composition for best ionic conduction based on these fitted models is $55Li_2O{\cdot}10ZrO_2{\cdot}35SiO_2$. Its activation energy and ionic conductivity at 300 K are 46.98 kJ/mol and $1.08{\times}10^{-5}{\Omega}^{-1}{\cdot}cm^{-1}$, respectively.

• 분석과학
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• 제6권3호
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• pp.275-282
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• 1993

지르콘사 광물에서 지르코니아를 회수하기 위하여 지르콘사를 분해 반응시킨 소성산물 중의 $SiO_2$와 $ZrO_2$를 DC arc source를 이용한 직독식 분광기로 동시 분석하였다. 순수한 금속산화물을 혼합하여 합성표준시료를 만들고 완충제(흑연)와 융제($Li_2B_4O_7$)의 혼합비를 조절하면서 최적의 들뜸조건을 선정하였다. 완충제와 흑연의 비를 0.22:1로 하고 시료와의 혼합비를 40배로 하였을 때 가장 좋은 들뜸조건을 얻을 수 있었다. 분석 결과의 표준편차는 $SiO_2$는 1.3%, $ZrO_2$는 4.9%였다.

• 전기학회논문지
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• 제57권11호
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• pp.2015-2022
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• 2008

The effect of content of $Al_2O_3+Y_2O_3$ sintering additives on the densification behavior, mechanical and electrical properties of the pressureless-sintered $SiC-ZrB_2$ electroconductive ceramic composites was investigated. The $SiC-ZrB_2$ electroconductive ceramic composites were pressurless-sintered for 2 hours at 1,700[$^{\circ}C$] temperatures with an addition of $Al_2O_3+Y_2O_3$(6 : 4 mixture of $Al_2O_3$ and $Y_2O_3$) as a sintering aid in the range of $8\;{\sim}\;20$[wt%]. Phase analysis of $SiC-ZrB_2$ composites by XRD revealed mostly of $\alpha$-SiC(6H), $ZrB_2$ and In Situ YAG($Al_5Y_3O_{12}$). The relative density, flexural strength, Young's modulus and vicker's hardness showed the highest value of 89.02[%], 81.58[MPa], 31.44[GPa] and 1.34[GPa] for $SiC-ZrB_2$ composites added with 16[wt%] $Al_2O_3+Y_2O_3$ additives at room temperature respectively. Abnormal grain growth takes place during phase transformation from $\beta$-SiC into $\alpha$-SiC was correlated with In Situ YAG phase by reaction between $Al_2O_3$ and $Y_2O_3$ additive during sintering. The electrical resistivity showed the lowest value of $3.l4{\times}10^{-2}{\Omega}{\cdot}cm$ for $SiC-ZrB_2$ composite added with 16[wt%] $Al_2O_3+Y_2O_3$ additives at 700[$^{\circ}C$]. The electrical resistivity of the $SiC-TiB_2$ and $SiC-ZrB_2$ composite was all negative temperature coefficient resistance (NTCR) in the temperature ranges from room temperature to 700[$^{\circ}C$]. Compositional design and optimization of processing parameters are key factors for controlling and improving the properties of SiC-based electroconductive ceramic composites.

• Bulletin of the Korean Chemical Society
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• 제34권4호
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• pp.1221-1224
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• 2013

The atomic layer deposition (ALD) of $ZrO_2$ was conducted in ultrahigh vacuum (UHV) conditions. The surface was exposed to $ZrCl_4$ and $H_2O$ in sequence and the surface species produced after each step were identified in situ with X-ray photoelectron spectroscopy (XPS). $ZrCl_4$ is molecularly adsorbed at 140 K on the $SiO_2$/Si(111) surface covered with OH groups. When the surface is heated to 300 K, $ZrCl_4$ loses two Cl atoms to produce $ZrCl_2$ species. Remaining Cl atoms of $ZrCl_2$ species can be completely removed by exposing the surface to $H_2O$ at 300 K followed by heating to 600 K. The layer-by-layer deposition of $ZrO_2$ was successfully accomplished by repeated cycles of $ZrCl_4$ dosing and $H_2O$ treatment.

• 한국결정성장학회지
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• 제9권2호
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• pp.217-223
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• 1999

본 연구에서는 질화규소에 지르코니아 첨가량에 따른 효과를 조사하였다. 0 wt%~40 wt%의 지르코니아를 포함하는 세라믹 복합체 재료를 토대로 하는 질화규소를 $1750^{\circ}C$에서 172 MPa의 질소가스압으로 한 시간동안 유지하는 조건으로 hot isostatic pressing (HIP)하였다. 소결된 시편의 기계적 특성과 마모 특성을 조사하였다. 질화 규소-지르코니아 복합체는 지르코니아 양이 증가함에 따라 경도와 굽힘강도는 감소하였으나 밀도는 증가하였다. 그리고, 지르코니아 첨가량이 증가함에 따른 공기 중에서의 마모량은 감소하였으며, 공기 중에서의 마모 거동은 microcracking에 유관하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1230-1231
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• 2008

The effect of content of $Al_2O_3+Y_2O_3$ sintering additives on the densification behavior, mechanical and electrical properties of the pressureless-sintered $SiC-ZrB_2$ electroconductive ceramic composites was investigated. The $SiC-ZrB_2$ electroconductive ceramic composites were pressureless-sintered for 2 hours at 1,700[$^{\circ}C$] temperatures with an addition of $Al_2O_3+Y_2O_3$(6:4 mixture of $Al_2O_3$ and $Y_2O_3$) as a sintering aid in the range of 8${\sim}$20[wt%]. Phase analysis of $SiC-ZrB_2$ composites by XRD revealed mostly of ${\alpha}$-SiC(6H), $ZrB_2$ and In Situ YAG($Al_5Y_3O_{12}$). The relative density, flexural strength, Young's modulus and vicker's hardness showed the highest value of 89.01[%], 81.58[Mpa], 31.437[GPa] and 1.34[GPa] for $SiC-ZrB_2$ composites added with 16[wt%] $Al_2O_3+Y_2O_3$ additives at room temperature respectively. Abnormal grain growth takes place during phase transformation from ${\beta}$-SiC into ${\alpha}$-SiC was correlated with In Situ YAG phase by reaction between $Al_2O_3$ and $Y_2O_3$ additive during sintering. Compositional design and optimization of processing parameters are key factors for controlling and improving the properties of SiC-based electroconductive ceramic composites. In this paper, it is convinced that ${\beta}$-SiC based electroconductive ceramic composites for heaters or ignitors can be manufactured by pressureless sintering.

• 대한기계학회논문집A
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• 제27권7호
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• pp.1132-1137
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• 2003

This study dealt with the suppression of interfacial reaction between Nb and MoSi$_2$ for the fabrication of high toughness Nb/MoSi$_2$ laminate composites, based on the results of a thermodynamical estimation. Especially, the effect of ZrO$_2$ particle on the interfacial reaction of Nb/MoSi$_2$ bonding materials has been examined. Nb/MoSi$_2$ bonding materials have been successfully fabricated by alternatively stacking matrix mixtures and Nb sheets and hot pressing in the graphite mould. The addition of ZrO$_2$ particle to MoSi$_2$ matrix is obviously effective for promoting both the interfacial reaction suppression and the sintered density of Nb/MoSi$_2$ bonding materials, since it is caused by the formation of ZrSiO$_4$ in the MoSi$_2$-ZrO$_2$ matrix mixture. The interfacial shear strength of Nb/MoSi$_2$ bonding materials also decreases with the reduction of interfacial reaction layer associated with the content of ZrO$_2$ particle and the fabrication temperature.

• 한국세라믹학회지
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• 제23권3호
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• pp.87-93
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• 1986

Yttria-bismuth-stabilized zirconia was investigated with respect to the amount of $Bi_2O_3$ addition in the ran-ge of 0.5~5mol% to the base composition of $(ZrO_2)_{0.92}(Y_2O_3)_{0.08}.Bismuth was introduced into the ma-terial with $Bi_2O_3-SiO_2$ glasses in order to reduce the evaporation of components. The sinterbility evaporation of components phase formation and microstructure were evaluated depending on the amount of $Bi_2O_3-SiO_2$ glass addition. Two probe A. C conductivity measurement was subjected to all the specimens and the result was discussed on the possible substitution of $Bi^{3+}$ for $Zr^{4+}$ and interistial $Si^{4+}$ in the fluorite structure of zirconia crystal there-upon the possible change in the capability of oxygen transference within the material. It was found that the addition of $Bi_2O_3$ could improve the sinterbility of material very much while not so much.oxygen sensing material suitable for relative low temperature firing.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.847-849
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• 1998

The effect of $Al_{2}O_{3}$ additives on the microstructure, mechanical and electrical properties of ${\beta}$-SiC+39vol.%$ZrB_2$ electroconductive ceramic composites by pressureless sintering were investigated. The ${\beta}$-SiC+39vol.%$ZrB_2$ ceramic composites were pressureless sintered by adding 4, 8, 12wt.% $Al_{2}O_{3}$ powder as a liquid forming additives at $1950^{\circ}C$ for 1h. Phase analysis of composites by XRD revealed mostly of $\alpha$-SiC(6H), $ZrB_2$ and weakly $\alpha$-SiC(4H), $\beta$-SiC(15R) phase. The relative density of composites was lowered by gaseous products of the result of reaction between $\beta$-SiC and $Al_{2}O_{3}$ therefore, porosity was increased with increased $Al_{2}O_{3}$ contents. The fracture toughness of composites was decreased with increased $Al_{2}O_{3}$ contents, and showed the maximum value of $1.4197MPa{\cdot}m^{1/2}$ for composite added with 4wt.% $Al_{2}O_{3}$ additives. The electrical resistivity of ${\beta}$-SiC+39vol.%$ZrB_2$ electroconductive ceramic composite was increased with increased $Al_{2}O_{3}$ contents, and showed positive temperature coefficient resistance (PTCR) in the temperature from $25^{\circ}C$ to $700^{\circ}C$.

• Nuclear Engineering and Technology
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• 제52권9호
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• pp.2054-2063
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• 2020

The high-temperature oxidation behavior of ZrSi₂ used as a coating material for nuclear fuel cladding was investigated for developing accident-tolerant fuel cladding of light water reactors. Bulk ZrSi₂ samples were prepared by spark plasma sintering. In situ X-ray diffraction was conducted in air at 900, 1000, and 1100 ℃ for 20 h. The microstructures of the samples before and after oxidation were examined by scanning electron microscopy and transmission electron microscopy. The results showed that the oxide layer of zirconium silicide exhibited a layer-by-layer structure of crystalline ZrO₂ and amorphous SiO₂, and the high-temperature oxidation resistance was superior to that of Zircaloy-4 owing to the SiO₂ layer formed. ZrSi₂ was coated on the Zircaloy-4 tube surface using laser 3D printing, and the coated tube was oxidized for 2000 s at 1200 ℃ under a vapor/argon mixture atmosphere. The outer surface of the coated tube was hardly oxidized (10-30 ㎛), while the inner surface of the uncoated tube was significantly oxidized to approximately 300 ㎛.