• Journal of the Korean Ceramic Society
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• v.50 no.1
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• pp.57-62
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• 2013

We investigated the thermal and electrical properties of the $B_2O_3-ZnO-Bi_2O_3$ glass system as a sealing material in sheath heater modules. A composition with over 90 wt% $Bi_2O_3$ in the $B_2O_3-ZnO-Bi_2O_3$ system was glassified by controlling the cooling rate. The glass transition temperature and thermal expansion coefficient in bismate glass could be controlled by the minor ingredients of ZnO, $SiO_2$, $BaO_2$, and $K_2O$. The $B_2O_3-ZnO-Bi_2O_3$ glass system bonded well to metal, and bismate glass insulating properties were comparable to those of bismate glass $B_2O_3-ZnO-PbO$ glass system in a sheath heater module.

• The Korean Journal of Ceramics
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• v.6 no.2
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• pp.91-95
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• 2000

Powder mixtures of $\beta$-SiC-TiC in a weight ratio of 2:1 containing 5-20 wt% additives ($Al_2O_3$-$Y_2O_3$) were liquid-phase sintered at $1830^{\circ}C$ for 1h by hot-pressing and subsequently annealed at $1950^{\circ}C$ for 6h to enhance grain growth. The annealed specimens revealed a microstructure of \"in situ-toughened composite\" as a result of the $\beta$longrightarrow$\alpha$ phase transformation of SiC during annealing. The increase of the content of additives accelerated the growth of elongated $\alpha$-SiC grains with higher aspect ratio and improved fracture toughness. The fracture toughness of SiC-TiC composite containing 20 wt% additive was 6.2 MPa.$m^{1/2}$.2}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.865-868
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• 2002

$SnO_2$ powders were prepare by precipitating $Sn(OH)_4$ from an aqueous solution of $SnCl_4{\cdot}5H_2O$, pH 9.5. The effects of stability and sensitivity of $SnO_2$ thick film sensors added with various amounts, $SiO_2$, $Al_2O_3$, $ZrO_2$, $TiO_2$ have been investigated. It is shown that the 3wt% $Al_2O_3$ or $SiO_2$ can improve the stability of $SnO_2$ gas sensor at an operating temperature of $350^{\circ}C$.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1661-1663
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• 2000

This study was to measure the dielectric characteristics of 0.05Pb($Al_{0.5}Nb_{0.5}$)-0.95Pb($Zr_{0.52}Ti_{0.48})O_3$[PAN-PZT] system ceramics according to the variation of $Cr_{2}O_3$, $Fe_{2}O_3$ addition amount. 0.0$\sim$1.2[wt%] and according to sintering temperature after creating the specimens with a general sintering way. The results of this study were summarized as follows : the dielectric constant at 20[$^{\circ}C$] reduced dy increasing additive on the whole. The dielectric loss was minimum value of 12.77[%], sintered at 1200[$^{\circ}C$], dopped with $Cr_{2}O_3$ 0.3[wt%] and minimum value of 10.89[%], sintered at 1200[$^{\circ}C$], dopped with $Fe_{2}O_3$ 0.6[wt%]. The variation rate of dielectric constant according to the change of frequency was decreased slowly by increasing frequency. The temperature coefficient of capacitance turned out increasing the stability of the temperature, decreased $Cr_{2}O_3$ 0.3wt% showed its minimum value 0.59[%/$^{\circ}C$], the maximum value 0.9[%/$^{\circ}C$] with $Cr_{2}O_3$ 3wt%.

• Journal of the Korean Ceramic Society
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• v.19 no.4
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• pp.316-320
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• 1982

The effect of the additive on dielectric properties of $BaTiO_3$ containing 0.030 mol% $Dy_2O_3$ was investigated function of frequency from 5$\times$104 to 0.3$\times$107cps and temperature from 25 to 1$25^{\circ}C$. The dielectric constant increased with increasing $Dy_2O_3$ concentration from 0 to 0.05mol% due to space charge polarization. However, the dielectric constant decreased for further increase of $Dy_2O_3$ concentration due to density increase. The dielectric constant exhibits rapid change at the Curie temperature and the Curie temperature drops from 122 to 116$^{\circ}C$ with increasing amount of $Dy_2O_3$ concentration.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.130-135
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• 2008

The objectives of this study are to investigate the combined heat and mass transfer enhancement using binary nanofluids as the working fluids in a $H_2O$/LiBr absorber. The result of heat and mass transfer experiment with the additives(Arabicgum, 2E1H) showed that the heat and mass transfer performance of binary nanofluid with 2E1H enhanced significantly in comparison with that without additive. In the case of 0.01wt% $Al_2O_3$ binary nanofluids with 2E1H, the vapor absorption rate increased up to 77% in comparison with that without additive. The heat transfer rate of 0.01wt% $Al_2O_3$ binary nanofluids with 2E1H increased up to 19%. Based on the experimental results, it is recommended that the $Al_2O_3$ binary nanofluid be good with 2E1H to improve the heat and mass transfer performance.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.543-544
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• 2006

The effect of the additives, $Y_2O_3$ and MgO, on the sintering and properties of $Al_2O_3-TiC$ composites was investigated. It is known that MgO is used as additive for improving densification and $Y_2O_3$ is applied as sintering aid. In this study, the amounts of TiC were varied in the range of 30-47 wt%. The 0.5 wt% MgO and also varied amounts of $Y_2O_3$ from 0.3 to 1 wt% were added into the composites. The sintering of $Al_2O_3-TiC$ composites was performed in a graphite-heating element furnace at different sintering temperature, 1700 and $1900\;^{\circ}C$, for 2 hr under an argon atmosphere. The results demonstrated that the properties of the composites sintered at $1700\;^{\circ}C$ were much better than those sintered at $1900\;^{\circ}C$. The comparisons on physical properties, mechanical properties and microstructure of composites with and without additives were reported. Comparing with other samples, $Al_2O_3-30wt%TiC$ composites with 0.5wt% MgO and $1\;wt%Y_2O_3$ exhibited the highest density of approximately 98% of theoretical and flexural strength of 302 MPa.

• Journal of the Korean Ceramic Society
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• v.19 no.4
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• pp.287-292
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• 1982

Nonohmic properties of ZnO ceramics with various small amounts of additives were studied in relation to experimental methods, additive contant and sintaring temperature. The kinds of additives used to following chemicals were basic additives ($0.5Bi_2O_3$, $0.3BaCO_3$, $0.5MnCO_3$, $0.5Cr_2O_3$, $0.1KNO_3$), $TiO_2$ and $Al(OH)_3$. Expecially, this study has focused on the effectsof $TiO_2$ and $Al(OH)_3$ in ZnO ceramics with the basic additives. SEM studies indicated that the addition of TiO2 promoted grain growth but retarded grain growth with the addition of $Al(OH)_3$. Also, in the case of calcination of ZnO with $TiO_2$ and ZnO with $Al(OH)_3$ previously, grain size of ZnO with $TiO_2$ was larger and that of ZnO with Al(OH)3 was smaller in comparison to the case with out calcination. From the viewpoint of nonohmic exponent and nonohimic resistance, electrical characteristics of ZnO, $TiO_2$ and the basic additives was more effective than that of ZnO, $Al(OH)_3$ and the basic additives. Nonohmic exponent and nonohmic resistance of ZnO, $TiO_2$ and the basic additives was 11-13 and 40-65 respectively.

• Journal of the Korean Ceramic Society
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• v.44 no.3 s.298
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• pp.137-141
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• 2007

$La_{2}O_{3}-TiO_{2}-SiO_{2}$ glass, a type that could not obtained so far by the conventional melting method, was prepared successfully using a sol gel process. Glass derived with the sol-gel process has compositions of $5La_{2}O_{3}-5TiO_{2}-90SiO_{2},\;5La_{2}O_{3}-10TiO_{2}-85SiO_{2}$, and $5La_{2}O_{3}-20TiO_{2}75SiO_{2}$. The UV-visible absorption edge of all glass compositions was below 400 nm. The measured density is in the range of 2.55-2.89, and was nearly identical to the calculated density and the refractive index of the glasses derived from the sol-gel ranges from 1.545 to 1.645. The molar additive coefficient of $TiO_{2}$ measured in this ternary system is lower than the calculated value, while the value of $La_{2}O_{3}$ is higher.

• Journal of the Korean Ceramic Society
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• v.22 no.2
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• pp.17-24
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• 1985

In the composition of $Pb(Mg_{0.15} W_{0.15})Ti_{0.35}-Zr_{0.35}O_3$ the effect of particle size on PbO vaporization were measured, . The initial step of discontinuous vaporization of unreated PbO during the calcining process was depended on the particle size. All additives $La_2O_3Nb_2O_5$ and $Al_2O_3$ inhibited the grain growth of the composition $Pb(Mg_{0.15} W_{0.15})Ti_{0.35}-Zr_{0.35}O_3$ +2wt% excess PbO. The dielectric and piezoelectric properties of the composition $Pb(Mg_{0.15} W_{0.15})Ti_{0.35}-Zr_{0.35}O_3$ were improved by the addition of 2wt% excess PbO and proper additive. The electromechanical planar coupling factor of 0.65 and mechnical quality factor of 390 could be obtained by adding 5wt% $Nb_2O_5$ to the composition 2wt% excess PbO+$Pb(Mg_{0.15} W_{0.15})Ti_{0.35}-Zr_{0.35}O_3$.