• Journal of the Korean Applied Science and Technology
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• v.30 no.3
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• pp.423-430
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• 2013

Carbon coils could be synthesized using $C_2H_2/H_2$ as source gases and $SF_6$ as an incorporated additive gas under thermal chemical vapor deposition (CVD) system. Prior to the carbon coils deposition reaction, two kinds of samples having different combination of Ni catalyst and substrate were employed, namely, a commercially-made $Al_2O_3$ ceramic boat with Ni powders and a commercially-made $Al_2O_3$ substrate with Ni layer. By using a commercially-made $Al_2O_3$ ceramic boat, the synthesis of carbon coils could be enhanced as much as 10 times higher than that of $Al_2O_3$ substrate. Furthermore, the dominant formation of the microsized carbon coils could be obtained by using $Al_2O_3$ ceramic boat. The surface roughness of the supporting substrate of $Al_2O_3$ ceramic boat was understood to be associated with the large scale synthesis of carbon coils as well as the dominant formation of the larger-sized, namely the microsized carbon coils.

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.161-163
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• 2008

$TiO_2-V_2O_5$ sol was fabricated using sol-gel method and $TiO_2-V_2O_5$, thin films were fabricated using dip-coating method. $V_2O_5$ sol was added 0.01mole, 0.03mole, 0.05mole into $TiO_2$ sol. Capacitance of thin films decreased with increasing $V_2O_5$ additive and it increased largest at 0.01mole. Because adsorption time and desorption time of thin films was about 2 minutes 40 seconds and about 3 minutes 40 seconds respectively, adsorption time was faster about 1 minutes than desorption time.

• Metals and materials international
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• v.24 no.6
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• pp.1309-1314
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• 2018

In this study, we investigated the state of $Y_2O_3$, as a major additive element in Fe-based ODS alloys, during mechanical alloying (MA) processes by thermodynamic approaches and experimental verification. For this purpose, we introduced $Ti_2O_3$ that formed different reaction products depending on the state of $Y_2O_3$ into the Fe-based ODS alloys. In addition, the reaction products of $Ti_2O_3$, Y, and $Y_2O_3$ powders were predicted approximately based on their formation enthalpy. The experimental results relating to the formation of Y-based complex oxides revealed that $YTiO_3$ and $Y_2Ti_2O_7$ were formed when $Ti_2O_3$ reacted with Y; in contrast, only $Y_2Ti_2O_7$ was detected during the reaction between $Ti_2O_3$ and $Y_2O_3$. In the alloy of $Fe-Cr-Y_2O_3$ with $Ti_2O_3$, $YTiO_3$ (formed by the reaction of $Ti_2O_3$ with Y) was detected after the MA and heat treatment processes were complete, even though $Y_2O_3$ was present in the system. Using these results, it was proved that $Y_2O_3$ decomposed into monoatomic Y and O during the MA process.

• Journal of the Korean Ceramic Society
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• v.19 no.4
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• pp.281-286
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• 1982

The composition of glasses to be suitable for crystallisation of $BaTiO_3$ by heat-treatment and the dielectric properties of the glass-ceramics were investigated. The composition of the family of glasses was defined by the formula $\chi$ $BaTiO_3 + (100-$\chi$)Al_2O_3$.$2SiO_2$ and excess BaO. Data were presented on dielectric constant and loss tangent at various frequencies. The effects of excess BaO on dielectric properties were investigated. The additions of $Na_2O$ and $Nb_2O_5$ shifted the Curite temperature of these glass-ceramics. The glass composition which was able to be melted at 145$0^{\circ}C$ and moulded as homogeneous glass phase without devitrification should contain $Al_2O_3$.$2SiO_2$ more than 30 mole %. The more the amount of additive BaO increased, the more dielectric constant increased. When the maximum heat-treatment temperature was 105$0^{\circ}C$, we obtained higher dielectric constant than that of 95$0^{\circ}C$. The dielectric constant and the dielectric loss were stable at frequencies between 5$\times$104 and 107 cycle per second. When $Na_2O$ and $Nb_2O_5$ were added, the Curie temperature, presented at 14$0^{\circ}C$ to 15$0^{\circ}C$, shifted to lower temperature. Therefore, the glass-ceramics having high dielectric constant at room temperature were obtained.

• Journal of the Korean Electrochemical Society
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• v.15 no.3
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• pp.190-197
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• 2012

We employed the vinyl ethylene carbonate (VEC) as an electrolyte additive and investigated the effect of the electrolyte additive on the electrochemical performance in hybrid capacitor. The activated carbon was adopted as cathode material, and the $Li_4Ti_5O_{12}$ oxide was used as anode material. The electrolyte was prepared with the $LiPF_6$ salt in the mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate(EMC). We evaluated the electrochemical performance of the hybrid capacitor with increasing the amount of the VEC electrolyte additive, which is known as the remover of oxygen functional group and the stabilizer of the electrode by reducing the surface of electrode, and obtained the superior performance data especially at the addition of the VEC electrolyte additive of around 0.7 vol%. On the contrary, the addition of the VEC more than 0.7 vol% in the electrolyte leads to the degradation in electrochemical performance of hybrid capacitor, suggesting the increase of the side reaction from the excessive VEC additive. X-ray photoelectron spectroscopy (XPS) revealed that the addition of the VEC suppressed the formation of LiF component, which is known as the insulator, on the surface of electrode. The optimized addition of VEC exhibited the improved capacity retention around 82.7% whereas the bare capacitors without VEC additive showed the 43.2% of capacity retention after 2500 cycling test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.333-336
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• 1999

The relationship between the DC degradation characteristics of the $ZnO-Bi_2O_3$ varistor and post-annealing is investigated in this study. $ZnO-Bi_2O_3$ varistors containing $SiO_2$ range 0.3 mol% were fabricated by standard ceramic techniques. The post- annealing is performed at $550^{\circ}C$ for 0, 1.5 and 5h. A little phase transition is found according to the analysis of X-ray diffraction. DC degradation tests were conducted at $115\pm3^{\circ}C$ for periods up to 22h. Current-voltage analysis was used to determine nonlinear coefficients($\alpha$). Capacitance-voltage analysis enable the donor density($N_d$) and the barrier height($E_B$) to be determined. From above analysis, it is found that the past-annealing for 5h improved degradation characteristics in $ZnO-Bi_2O_3$ with Si additive.

• Journal of the Korean Ceramic Society
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• v.39 no.1
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• pp.45-50
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• 2002

Effect of sintering additives on the densification behavior of reaction-bonded silicon nitride prepared by using coarse Si powders is discussed. Sintering additives such as 6 wt% $Y_2O_3$+1wt% $A1_2O_3$ (6YlA) did not give rise to full densification, while full densification was obtained by using the sintering additives such as 6wt% $Y_2O_3$+3 wt% $A1_2O_3$+ 2wt% $SiO_2$ (6Y3A2S) and 9wt% $Y_2O_3$+ 1.5wt% $A1_2O_3$+ 3wt% $SiO_2$ (9Yl.5A3S). In the case of 6Y3A2S addition, high fracture strength of 960 MPa and the fracture toughness of $6.5 MPa.m^{1/2}$ were obtained.

• Journal of Environmental Health Sciences
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• v.14 no.1
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• pp.1-9
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• 1988

석탄유도가스에 포함된 황화수소를 제거시킬 흡착제를 개발하기 위하여 알칼리 토금속, 천이원소 및 아연의 이온반경보다 이온반경이 작은 금속산화물을 산화아연에 첨가시켜 다공성 흡착제를 제조하였다. 600$\circ$C에서 이들 첨가시료를 2.09vol.% 황화수소와 질소가스 혼합기체로 반응시켜 초기속도를 측정하고, 같은 온도에서 사용된 흡착제를 공기로 재생시켰다. 사용된 금속산화물 첨가 흡착제중에서 CaO, TiO$_2$, $Fe_2O_3$, CuO, $Ga_2O_3$ 및 Si$_2$O가 ZnO 흡착제의 초기속도를 증가시켜 첨가제로 사용할 수 있음을 보였다.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.4
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• pp.210-218
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• 2000

For the fabrication of $YBa_2Cu_3O_x$ thick film, a substrate of $Y_2BaCuO_5$ was fabricated by adding $CeO_2$ into $Y_2BaCuO_5$ and two types of doping materials added with binder material were prepared. Each doping material was patterned on $Y_2BaCuO_5$substrate by the screen printing method and then was annealed at the temperature with a few step. It could be observed by X-ray diffraction patterns and SEM photographs that through the diffusion process of the $Y_2BaCuO_5$ and each doping material, the $YBa_2Cu_3O_x$ phase was formed. And with n additive of $CeO_2$ the thickness of formed $YBa_2Cu_3O_x$decreased. From the experiment of current limiting on thick film, the sample with thiner thickness of $YBa_2Cu_3O_x$ showed the more effective characteristics of current limiting.

• Journal of the Korean Electrochemical Society
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• v.19 no.1
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• pp.1-8
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• 2016

Capacity of layered lithium nickel-cobalt-manganese oxide ($LiNi_{1-x-y}Co_xMn_yO_2$) cathode material can increase by raising the charge cut-off voltage above 4.3 V vs. $Li/Li^+$, but it is limited due to anodic instability of conventional electrolyte. We have been screening and evaluating various sulfone-based compounds of dimethyl sulfone (DMS), diethyl sulfone (DES), ethyl methyl sulfone (EMS) as electrolyte additives for high-voltage applications. Here we report improved cycling performance of $LiNi_{0.5}Co_{0.2}Mn_{0.3}O_2$ cathode by the use of dimethyl sulfone (DMS) additive under an aggressive charge condition of 4.6 V, compared to that in conventional electrolyte, and cathode-electrolyte interfacial reaction behavior. The cathode with DMS delivered discharge capacities of $198-173mAhg^{-1}$ over 50 cycles and capacity retention of 84%. Surface analysis results indicate that DMS induces to form a surface protective film at the cathode and inhibit metal-dissolution, which is correlated to improved high-voltage cycling performance.