• Journal of the Korean Ceramic Society
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• v.33 no.5
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• pp.507-513
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• 1996

Nonlinear optical properties of TeO2-PbO-GeO2 glasses were investigated and their correlation with struc-tural modification was investigated. Third-order nonlinear susceptibility $\chi$, ranged between 5.0$\times$10-13 esu and 10.7$\times$10-13 esu which are approximately 20-40 times larger than that of silica glass. The glass with a composition of 85(80TeO2-20PbO)-15GeO2(mol%) seemed to provide an optimum compromise between $\chi$and the stability against crystallization. Analyses of the Raman spectra suggested that these glasses are mainly composed of [TeO4] tbp, [TeO3]tp and [GeO4] tetrahedral structural units. It was concluded that the positive contribution of Pb2+ with high polarizability to $\chi$ in TeO2-PbO glasses overwhelmed the negative influence due to the structural modification of [TeO4]tbplongrightarrow[TeO3]tp. On the other hand addition of GeO2 in TeO2-PbO-GeO2 glasses resulted in the decrease of $\chi$ values. This behavior was attributed to the formation of [GeO4] polyhedra at the expense of [TeOn] polyhedra and Pb2+ ions which normally sowed a higher contribu-tion to $\chi$ than [GeO4] polyhedra.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.3
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• pp.15-20
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• 2007

Low temperature processed ZnO-TFTs on glass below $270^{\circ}C$ for plastic substrate applications were fabricated and their electrical properties were investigated. Films in ZnO-TFTs with bottom gate configuration were made by RF magnetron sputtering system except for $SiO_2$ gate oxide deposited by ICP-CVD. ZnO channel films were grown on glass with various Ar and $O_2$ flow ratios. All of the fabricated ZnO-TFTs showed perfectly the enhancement mode operation, a high optical transmittance of above 80% in visible ranges of the spectrum. In the ZnO-TFTs with pure Ar process, the field effect mobility, threshold voltage, and on/off ratio were measured to be $1.2\;cm^2/Vs$, 8.5 V, and $5{\times}10^5$, respectively. These characteristic values are much higher than those of the ZnO-TFTs of which ZnO channel layers were processed with additional $O_2$ gas. In addition, ZnO-TFT with pure Af process showed smaller swing voltage of 1.86v/decade compared to those with $Ar+O_2$ process.

• Journal of the Korean Ceramic Society
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• v.38 no.2
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• pp.158-165
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• 2001

고체산화물 연료전지용 밀봉재로서 전지 구성원과 열팽창계수가 유사하고 비젖음성 특성을 가지며 전지 작동온도에서 화학적 안정성을 갖는 밀봉유리를 개발하고자, BaO-Al$_2$O$_3$-La$_2$O$_3$-Ba$_2$O$_3$-SiO$_2$계 유리를 제조하여 조성 변화에 따른 열적 특성 변화와 접합후의 젖음성 및 반응성 등을 조사하였다. 유리망목 형성산화물인 B$_2$O$_3$와 SiO$_2$의 함량비 및 BaO의 망목 형성산화물(B$_2$O$_3$+SiO$_2$)에 대한 함량비 변화에 따른 유리의 열적 특성을 조사한 결과, 0.33~0.71의 B$_2$O$_3$/SiO$_2$함량비하에서 BaO/(B$_2$O$_3$+SiO$_2$)가 0.70일 때 유리의 열팽창계수는 106~111$\times$$10^{-7}$/K 이었으며 이때 연료전지 구성원인 YSZ(yttria stabilized zirconia)와의 열팽창 불일치(thermal expansion mismatch)가 가장 작았다. 또한 이러한 조성의 유리로부터 분말성형체를 제조하여 YSZ에 접합을 시도한 결과, 우수한 접합성 및 비젖음성을 확인할 수 있었으며, 800~8$50^{\circ}C$의 전지 작동온도에서 100시간까지 유지시에도 YSZ와의 계면반응이 일어나지 않음을 관찰할 수 있었다.

• Fire Science and Engineering
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• v.30 no.1
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• pp.17-23
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• 2016

Membrane structures can be used to create diverse lightweight structural forms using ductile membranes made of coated fabric. Using membrane structures, it is possible to construct large covered spaces relatively quickly and economically, and hence, they are being applied within various applications. The structures are light-weight, transparent, flexible in their application, economical and easy to maintain, and as such, their usage is being expanded. However, despite their prevalence, the standard for membrane material performance in terms of fire safety is still inadequate, and the development of membrane materials with excellent flame resistance performance is being demanded. This study determined flame resistance performance of architectural membranes, including PTFE, PVDF, PVF and ETFE film membranes, through flammability testing and incombustibility testing.

• Journal of the Korean Ceramic Society
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• v.32 no.11
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• pp.1269-1275
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• 1995

Effects of GeO2 addition on the thermal and structural stabilities of PbO-Bi2O3-Ga2O3 glasses were studied. Thermal stabilities, as assessed by the weighted thermal stability factors [(Tx-Tg)/Tg], increased with GeO2 concentraton from 0.097 to 0.210 with the addition of 20 mol% GeO2. Increasing GeO2 content resulted in the decrease of apparent density, molar volume, refractive index and thermal expansion. On the other hand, IR transmission cut-off (λT=50%) moved from 6.73${\mu}{\textrm}{m}$ for the ternary PbO-Bi2O3-Ga2O3 glass to shorter wavelength side, 5.98${\mu}{\textrm}{m}$ for a glass containing 20mol% GeO2. There were little change with GeO2 content, however, in the activation energies for the viscous flow of approximately 140 kcal/mole within the temperature interval of 300~50$0^{\circ}C$. Addition of GeO2 to PbO-Bi2O3-Ga2O3 glasses enhanced the thermal and structural stabilities significantly at the expense of their infrared transmittance. An appropriate compsomise between these two opposite trends should be made following the specifications of the final applications.

• Journal of the Korean Ceramic Society
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• v.32 no.12
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• pp.1357-1368
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• 1995

Nasigels of composition Na0.75Zr2PSi2O12 and Na3Zr2PSi2O12 have been synthesized by the sol-gel technique using metal alkoxide precursors. The monolithic dry gels of Na0.75Zr2PSi2O12 with no crack have been prepared by the control of the shrinkage rte, but gels of Na3Zr2PSi2O12 were impossible to prepare without cracking. The gels treated up to 80$0^{\circ}C$ led to the formtion of glass but the glasses were converted to the crystalline phases at above this temperature. Crystaline phases precipitated from the Na0.75Zr2PSi2O12 glass were NASICON-like phase, Na2Si2O5, and free Zirconia. Phase that precipitated from the Na3Zr2PSi2O12 was only rhombohedral NASICON. For Na0.75Zr2PSi2O12 gels, framework of PO4 tetrahedra and SiO4(PO4) tetrahedra formed at low temperature but changed to that of SiO4 and SiO4(PO4) tetrahedras as it were crystallized. In the case of Na3Zr2PSi2O12 gel, framework of isolated PO4 and SiO4 tetrahedras formed at low temperature but changed to SiO4(PO4) tetrahedra framework which usually formed in the NASICON crystal after crystallization at high temperature. The gels treated up to 80$0^{\circ}C$ contained the residual water. The ionic conduction was attributed to the motion of proton and Na+ ion at low (up to 150~20$0^{\circ}C$) and high temperatures, respectively. As the temperature of heat treatment increased, ionic conductivity gradaully increased with the extent of precipitation of crystalline phase.

• Journal of the Korean Ceramic Society
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• v.55 no.5
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• pp.446-451
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• 2018

In this study, different formulations of magnesium oxide and various modifiers (phosphoric acid, ferrous sulfate, pure acrylic emulsion, silicone acrylic emulsion, glass fiber, and polypropylene fiber) were used to prepare magnesium oxychloride cement composites. The compressive strength of the magnesium oxychloride cement was tested, and the softening coefficients of the composites after soaking in water were also calculated. The results showed that a magnesium oxychloride cement sample could not be coagulated when the MgO activity was 24.3%, but the coagulation effect of the magnesium oxide cement sample was excellent when the MgO activity was 69.5%. While pure acrylic emulsion, silicon-acrylic emulsion, and glass fiber showed insignificant modification effects on the magnesium oxychloride cement, ferrous sulfate heptahydrate, phosphoric acid, and polypropylene fiber could effectively improve its water resistance and compressive strength. When the phosphoric acid, ferrous sulfate heptahydrate, and polypropylene fiber contents were 0.47%, 0.73%, and 0.25%, respectively, the softening coefficient of a composite soaked in water reached 0.93 after 7 days, and the compressive strength reached 64.3 MPa.

• Journal of the Korean Ceramic Society
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• v.51 no.6
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• pp.584-590
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• 2014

Air-cooled slag showed grindability approximately twice as good as that of water-cooled slag. While the studied water-cooled slag was composed of glass as constituent mineral, the air-cooled slag was mainly composed of melilite. It is assumed that the sulfur in air-cooled slag is mainly in the form of CaS, which is oxidized into $CaS_2O_3$ when in contact with air. $CaS_2O_3$, then, is released mainly as $S_2O{_3}^{2-}$ion when in contact with water. However, the sulfur in water-cooled slag functioned as a constituent of the glass structure, so the$S_2O{_3}^{2-}$ ion was not released even when in contact with water. When no chemical admixture was added, the blended cement of air-cooled slag showed higher fluidity and retention effect than those of the blended cement of the water-cooled slag. It seems that these discrepancies are caused by the initial hydration inhibition effect of cement by the $S_2O{_3}^{2-}$ ion of air-cooled slag. When a superplasticizer is added, the air-cooled slag used more superplasticizer than did the blast furnace slag for the same flow because the air-cooled slag had higher specific surface area due to the presence of micro-pores. Meanwhile, the blended cement of the air-cooled slag showed a greater fluidity retention effect than that of the blended cement of the water-cooled slag. This may be a combined effect of the increased use of superplasticizer and the presence of released $S_2O{_3}^{2-}$ ion; however, further, more detailed studies will need to be conducted.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.369-370
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• 2005

LTCC (Low Temperature Cofired Ceramic) technology is one of technologies which can realize SIP (System-In-a-Package). In this paper realization of gas sensor using LTCC technology was described. In the conventional gas sensor structure, wire bonding method is generally used as an interconnection method whereas in the LTCC sensor structure, via was used for the interconnection. As sensing materials, $SnO_2$ was adopted. The effect of frit glass portion on the adhesion of the sensing material to the LTCC substrate and the electrical conductivity of the sensing material were analyzed. AgPd, PdO, Pt was added to the sensing material as an additive for improving the gas sensitivity and electrical conductivity and the effect of the amount of additives in the sensing material on the electrical conductivity was investigated. The effect of the amount of frit glass in the termination on the sensor performance, especially mechanical integrity, was considered and the crack initiation and propagation in the boundary between the sensing material and the termination was studied.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.9
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• pp.855-861
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• 2006

Sinterability and microwave dielectric properties of $xZWO_{4}-(1-x)TiO_{2}$ ceramic systems with zinc-borosilicate glass and $TiO_{2}$ contents for LTCC(Low Temperature Co-fired Ceramics) were investigated. The addition of $3{\sim}10\;wt%$ ZBS glass ensured the sinterability below $900^{\circ}C$. In general, increasing ZBS glass content seemed to enhance the sinterability, but the quality factor($Qxf_{0}$) significantly decreased due to the formation of an excessive liquid and second phases. As for the addition of $TiO_{2}$, the dielectric constant(${\varepsilon}_{r}$) and temperature coefficient of resonant frequency(${\tau}_{f}$) showed to increase, while the quality factor($Qxf_{0}$) did not show an apparent change. The composition of $0.7xZnWO_{4}-0.3TiO_{2}$ ceramics sintered at $900^{\circ}C$ with 5 wt% ZBS glass demonstrated 21.6 in dielectric constant(${\varepsilon}_{r}$), 14,800 in quality factor($Qxf_{0}$), and $+5\;ppm/^{\circ}C$ in temperature coefficient of resonant frequency(${\tau}_{f}$).