• Bulletin of the Korean Chemical Society
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• 제28권9호
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• pp.1463-1466
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• 2007

Single phases of multi-component oxides films, ZrTiO4 and Ta2Zr6O17, could be synthesized by using the combinatorial approach through surface sol-gel route, coating the appropriate mole ratio of 100 mM zirconium butoxide, tantalum butoxide and titanium butoxide precursors on Pt/Ti/SiO2/Si (100) substrate, following pyrolysis at 450 oC, and annealing them at 770 oC. Both the films and bulks of ZrTiO4 and Ta2Zr6O17 showed very stable dielectric properties in temperature range, ?140 to 60 oC, and frequency range, 100 Hz to 1 MHz, promising their applications in wide range of temperatures and frequencies. The dielectric constants of the films were lower and a little more dependent on frequency than those of the bulks. The reduction of dielectric property in the film was mainly due to the interfacial effects that worked as series and parallel-connected capacitances toward the substantial film capacitance.

• 대한기계학회논문집
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• 제13권3호
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• pp.404-410
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• 1989

본 연구에서는 공업용 세라믹(요업재료등)으로 개발된 것 중에서 가장 마찰특성이 우수할 것으로 간주되고 있는 SiC, Si$_{3}$N$_{4}$와 ZrO$_{2}$ 의 건조 및 윤활마찰특성과 금속과의 마찰특성을 실험적으로 밝히려 한다.

• 한국재료학회지
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• 제20권4호
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• pp.217-222
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• 2010

Zirconium diboride (ZrB2) and mixed diboride of (Zr0.7Ta0.3)B2 containing 30 vol.% silicon carbide (SiC) composites were prepared by hot-pressing at $1800^{\circ}C$. XRD analysis identified the high crystalline metal diboride-SiC composites at $1800^{\circ}C$. The TaB2 addition to ZrB2-SiC showed a slight peak shift to a higher angle of 2-theta of ZrB2, which confirmed the presence of a homogeneous solid solution. Elastic modulus, hardness and fracture toughness were slightly increased by addition of TaB2. A volatility diagram was calculated to understand the oxidation behavior. Oxidation behavior was investigated at $1500^{\circ}C$ under ambient and low oxygen partial pressure (pO2~10-8 Pa). In an ambient environment, the TaB2 addition to the ZrB2-SiC improved the oxidation resistance over entire range of evaluated temperatures by formation of a less porous oxide layer beneath the surface SiO2. Exposure of metal boride-SiC at low pO2 resulted in active oxidation of SiC due to the high vapor pressure of SiO (g), and, as a result, it produced a porous surface layer. The depth variations of the oxidized layer were measured by SEM. In the ZrB2-SiC composite, the thickness of the reaction layer linearly increased as a function of time and showed active oxidation kinetics. The TaB2 addition to the ZrB2-SiC composite showed improved oxidation resistance with slight deviation from the linearity in depth variation.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1993년도 추계 학술발표 강연 및 논문 개요집
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• pp.36-36
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• 1993

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권2호
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• pp.98-103
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• 1999

The effect of $Al_2O_3$ additives to $\beta-SiC+39vol.%ZrB_2$ electroconductive ceramic composites by pressureless sintering on microstructural, mechanical and electrical properties were investigated. The $\beta-SiC+39vol.%ZrB_2$ ceramic composites were pressureless sintered by adding 4, 8, 12wt.% $Al_2O_3$ powder as a liquid forming additives at $1950^{\cire}C$ 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_2O_3$, therefore, porosity was increased with increasing $Al_2O_3$ contents, and showed the maximum value of 1.4197MPa.$m^{1/2}$ for composite with 4wt.% $Al_2O_3$ additives. The electrical resistivity of $\beta-SiC+39vol.%ZrB_2$ electroconductive ceramic composite was increased with increasing $Al_2O_3$ contents, and showed positive temperature coefficient resistance (PTCR) in the temperature range of $25^{\cire}C$ to $700^{\cire}C$.

• 소성∙가공
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• 제8권3호
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• pp.327-327
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• 1999

The oxidation behavior of 60%Cu-40%Zn brass haying small amounts of Zr, Cr, Mg, Al, and Si was studied between 873 and 1043 K in air. The alloying element of Mg was harmful, while other alloying elements were beneficial to oxidation resistance. Particularly, the simultaneous addition of Al and Si decreased the oxidation rate drastically. During oxidation, Zr formed ZrO₂, Cr formed CuCr₂O₄, Mg formed MgO, Al formed A1₂CuO₄, and Si formed amorphous SiO₂. These oxides were incorporated in the oxide scale composed predominantly of ZnO. The oxide scales formed on all the tested alloyswere prone to cracking, wrinkling, and spallation.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권11호
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• pp.505-513
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• 2006

The present study investigated the influence of the content of $Al_2O_3+Y_2O_3$ sintering additives on the microstructure, mechanical and electrical properties of the pressureless-sintered $SiC-ZrB_2$ electroconductive ceramic composites. Phase analysis of composites by XRD revealed mostly of ${\alpha}-SiC(4H),\;ZrB_2,\;{\beta}-SiC(15R)$ and In Situ $YAG(Al_5Y_3O_{12})$. The relative density and the flexural strength showed the highest value of 86.8[%] and 203[Mpa] for $SiC-ZrB_2$ composite with an addition of 8[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid at room temperature respectively. Owing to crack deflection and crack bridging of fracture toughness mechanism, the fracture toughness showed 3.7 and $3.6[MPa{\cdot}m^{1/2}]\;for\;SiC-ZrB_2$ composites with an addition of 8 and 12[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid 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 $Al_2O_3\;and\;Y_2O_3$ additives during sintering. The electrical resistivity showed the lowest value of $6.5{\times}10^{-3}[({\Omega}{\cdot}cm]$ for the $SiC-ZrB_2$ composite with an addition of 8[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid at room temperature. The electrical resistivity of the $SiC-ZrB_2$ composites was all positive temperature coefficient(PTCR) in the temperature ranges from $25[^{\circ}C]\;to\;700[^{\circ}C]$. The resistance temperature coefficient showed the highest value of $3.53{\times}10^{-3}/[^{\circ}C]\;for\;SiC-ZrB_2$ composite with an addition of 8[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid in the temperature ranges from $25[^{\circ}C]\;to\;700[^{\circ}C]$. In this paper, it is convinced that ${\beta}-SiC$ based electroconductive ceramic composites for heaters or ignitors can be manufactured by pressureless sintering.

• 한국세라믹학회지
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• 제24권2호
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• pp.155-160
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• 1987

본 연구는 제2보에서 합성한 $ZrSiO_4-Cd(SxSe_{1-x})$ 채료의 실용성을 조사하기 위하여 행하였다. 기존의 유명회사 제품의 채료와 본 합성채료를 비교 검사하였다. 우선 각각의 채료에 Frit를 적당한 비로 혼합하고 일정조성의 Tile에 시유하여 각각다른 온도(850-120$0^{\circ}C$)에서 소성한 다음 colorimeter를 사용하여 XYZ 주파장에 따른 색도도를 측정하였다. 또한 Munsell 계의 ISCC-NBS 색명법을 적용하여 색을 정량화 시킴으로서 채료의 적응성을 연구하였다. 그 결과 $ZrSiO_4-Cd(SxSe_{1-x})$ 채료는 V나 P 계통의 여타 채료와 같이 Frit 대 Stain의 비가 9:1의 최소비로 사용이 가능하며 100$0^{\circ}C$의 높은 온도에서도 밝은 적색으로 재현 될 뿐만 아니라 내산성이 강하고 고온에서 적응성이 있음을 확인하였다.

• 공업화학
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• 제9권1호
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• pp.141-148
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• 1998

초강산 담체인 $ZrO_2$ $SO_4{^{2-}}$에 담지된 백금촉매(0.2, 0.5wt% Pt)의 저온 산화반응성을 cyclohexane의 완전산화반응에 대하여 조사 하였다. 충전층 관형반응기에서 반응물질의 전화율로 측정된 촉매활성은 촉매의 산성도와 비표면적에 비례하여 증가하였다 : $Pt/ZrO_2$ $SO_4{^{2-}}$ 촉매 제조과정에서 K(potassium)를 첨가하여 촉매의 산성도와 비표면적을 감소시켰을 때 촉매활성은 K첨가량에 비례하여 감소하였다. 또한 $Pt/ZrO_2$ $SO_4{^{2-}}$촉매는 훨씬 더 큰 비표면적을 가진 $Pt/SiO_2$, 또는 $Pt/Al_2O_3$촉매보다 뛰어난 활성을 보였다 : l5,000ppm cyclohexane농도와 $18,000hr^{-1}$공간속도를 가진 반응물질 흐름을 $250^{\circ}C$에서 0.2wt% $Pt/ZrO_2$ $SO_4{^{2-}}$촉매를 사용하여 전화시킨 결과 96%의 cyclohexane전화율을 보인 반면, 같은 반응조건 하에서 0.2wt% $Pt/SiO_2$와 0.2wt% $Pt/Al_2O_3$촉매는 각각 83%와 79%의 cyclohexane전화율을 보였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기물성,응용부문
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• pp.191-193
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• 2004

The composites were fabricated, respectively, using 61vol.% SiC-39vol.% $TiB_2$ and using 61vol.% SiC-39vol.% $ZrB_2$ powders with the liquid forming additives of 12wt% $Al_2O_3+Y_2O_3$ by hot pressing annealing at $1650^{\circ}C$ for 4 hours. Reactions between SiC and transition metal $TiB_2$, $ZrB_2$ were not observed in this microstructure. The result of phase analysis of composites by XRD revealed SiC(6H, 3C), $TiB_2$, $ZrB_2$ and $YAG(Al_5Y_3O_{12})$ crystal phase on the SiC-$TiB_2$, and SiC-$ZrB_2$ composites. The ${\beta}\;{\alpha}$-SiC phase transformation was occurred on the $SiC-TiB_2$, $SiC-ZrB_2$ composites. The relative density, the flexural strength and Young's modulus showed respectively value of 98.57%, 226.06Mpa and $86.37{\times}10^3Mpa$ in SiC-$ZrB_2$ composites.