• Proceedings of the Korean Nuclear Society Conference
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• 1996.11b
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• pp.539-544
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• 1996

핵연료 피복관용 신합금으로 개발되고 있는 여러 가지 Zr합금에서 생성되는 석출물의 특성을 규명하기 위하여 EDX가 부착된 TEM을 이용하여 석출물에 관한 연구를 수행하였다. Zrl.4Sn0.2Fe0.1Cr 합금에서는 두 종류의 석출물이 생성되는데 하나는 석출물의 대부분을 차지하는 HCP 구조의 Zr(Cr,Fe)$_2$ 석출물로서 이는 둥근 형태를 유지하며 결정립내나 결정립계에 관계없이 널리 분산되어 분포된다. 다른 하나의 석출물은 극히 일부에서만 관찰되는 Zr$_2$(Fe,Si)성분의 석출물로서 이는 tetragonal 구조를 갖는다. Zr0.5Nb0.6Fe0.3V 합금에서는 tetragonal (Zr,Nb)$_2$(Fe,V)석출물이 형성되며, Nb이 1.0 wt.% 첨가된 Zr1.0Nb0.6Fe0.3V 합금에서는 HCP 구조의 (Zr,Nb)(Fe,V)$_2$ 석출물과 BCC 구조인 $\beta$-Zr이 생성된다. Zr1.0Nb0.6Fe0.3V 합금을 제외하고는 대부분의 합금에서 석출물은 약 1.0 $\mu$m의 크기를 나타냈다. 합금 조성이 다를 경우에 석출물 크기와 35$0^{\circ}C$ 부식 특성과는 연관성이 없는 것으로 나타났다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2002.05a
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• pp.100-100
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• 2002

• Proceedings of the Korean Ceranic Society Conference
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• 2004.10a
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• pp.90.1-90.1
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• 2004

• Proceedings of the Korean Ceranic Society Conference
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• 2000.04a
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• pp.153.2-153.2
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• 2000

• Proceedings of the Korean Magnestics Society Conference
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• 2010.06a
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• pp.69-69
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• 2010

• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.41.2-41.2
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• 2008

• Journal of Industrial Technology
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• v.20 no.A
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• pp.247-256
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• 2000

Precursor gels with the composition of $xZrO_2{\cdot}(100-x)SiO_2$ systems (x=10, 20 and 30 mol%) were prepared by the sol-gel method. Kinetic parameters, such as activation energy, Avrami's exponent, n, and dimensionality crystal growth value, m, have been simultaneously calculated from the DTA data using Kissinger and Matusita equations. The crystallite size dependence on tetragonal to monoclinic transformation of $ZrO_2$ was investigated using XRD, in relation to the fracture toughness. The crystallization of tetragonal $ZrO_2$ occurred through 3-dimensional diffusion controlled growth(n=m=2) and the activation energy for crystallization was calculated using Kissinger and Matusita equations, as about $310{\sim}325{\pm}10kJ/mol$. The growth of $t-ZrO_2$, in proportion to the cube of radius, increased with increasing heating temperature and heat-treatment time. It was suggested that the diffusion of Zr4+ions by Ostwald ripening was rate-limiting process for the growth of $t-ZrO_2$ crystallite size. The fracture toughness of $xZrO_2{\cdot}(100-x)SiO_2$ systems glass ceramics increased with increasing crystallite size of $t-ZrO_2$. The fracture toughness of $30ZrO_2{\cdot}70SiO_2$ system glass ceramics heated at $1,100^{\circ}C$ for 5 h was $4.84Mpam^{1/2}$ at a critical crystaliite size of 40 nm.

• Korean Journal of Materials Research
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• v.20 no.7
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• pp.379-384
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• 2010

The usual ceramic process of mixing and milling in state of oxides $ZrO_2$ and $CeO_2$ was adopted in this study in a wet process to manufacture Ce-TZP. $CeO_2$-$ZrO_2$ ceramics containing 8~20 mol% $CeO_2$ were made by heat treatment at $1250\sim1500^{\circ}C$ for 5hr. The maximum dispersion point of every slurry manufactured with a mixture of $ZrO_2$ and $CeO_2$ was neat at pH10. A stable slurry with average particle size of 90 nm can be manufactured when it is dispersed with the use of ammonia water and polycarboxylic acid ammonium. The sintered Ce-TZP ceramics manufactured with the addition of $CeO_2$ in a concentration of less than 10 mol% progressed to the fracture of the specimen due to the existence of a monoclinic phase of more than 30% at room temperature. More than 99% of the tetragonal phase was created for the sintered body with the addition of $CeO_2$ beyond 18 mol%, but the degradation of the mechanical properties on the entire specimen was brought about due to the $CeO_2$ existing in a percentage above 3%. Consequently, the optimal Ce-TZP level combined in the oxide state was identified to be 16 mol% of $CeO_2$ contents.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.3
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• pp.91-94
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• 2007

Single-crystalline $SnO_2$ nanowires were successfully grown on Si(001) substrates via vapor-liquid-solid mechanism in a thermal chemical vapor deposition. Large quantity of $SnO_2$ nanowires were synthesized at temperature ranges of $950{\sim}1000^{\circ}C$ in Ar atmosphere. It was found that the grown $SnO_2$ nanowires are of a tetragonal rutile structure and single crystalline by diffraction and transmission electron microscopy measurements. Broad emission located at about 600 m from the grown nanowires was clearly observed in room temperature photoluminescence measurements, indicating that the emission band originated from defect level transition into $SnO_2$ nanowires.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.119-122
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• 2002

The calculated and measured dielectric constant of (1-x)(Al$\sub$1/2/Ta$\sub$1/2/)O$_2$-x(Mg$\sub$1/3/Ta$\sub$2/3/)O$_2$(O$\leq$x$\leq$1.0) solid solutions were investigated by variations of ionic polarizability and crystal structure. (Al$\sub$1/2/Ta$\sub$1/2/)O$_2$ and (Mg$\sub$1/3/Ta$\sub$2/3/)O$_2$were orthorhombic and tetragonal trirutile structure, respectively. When (Al$\sub$1/2/Ta$\sub$1/2/)O$_2$ was substituted by (Mg$\sub$1/3/Ta$\sub$2/3/)O$_2$, the phase transformed to tetragonal structure over 60 mole%. Because the ionic radius of (Mg$\sub$1/3/Ta$\sub$2/3/)O$_2$was slightly bigger than one of (A1$\sub$1/2/Ta$\sub$1/2)O$_2$, the cell parameters increased with an increase of (Mg$\sub$1/3/Ta$\sub$2/3/)O$_2$ substitution. The measured dielectric constant increased with an increase of (Mg$\sub$1/3/Ta$\sub$2/3/)O$_2$ substitution and coincided with dielectric mixing rule and the calculated dielectric constant with the molecular additivity rule. There were some differences between the measured and the calculated dielectric constant. The reason of the lowered dielectric constant comparing with the calculated one was compressed stress due to the electronic structure of tantalum.