• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05b
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• pp.74-77
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• 2002

Ferroelectric Random Access Memory(FRAM) and MEMS applications require noble metal or refractory metal oxide electrodes. In this study, Ru thin films were etched using $O_2$+10% $CF_4$ plasma in an inductively coupled plasma(ICP) etching system. The etch rate of Ru thin films was examined as function of rf power, DC bias applied to the substrate. The enhanced etch rate can be obtained not only with increasing rf power and DC bias voltage, but also with small addition $CF_4$ gas. The selectivity of $SiO_2$ over Ru are 1.3. Radical densities of oxygen and fluorine in $CF_4/O_2$ plasma have been investigated by optical emission spectroscopy(OES). The etching profiles of Ru films with an photoresist pattern were measured by a field emission scanning electron microscope (FE-SEM). The additive gas increases the concentration of oxygen radicals, therefore increases the etch rate of the Ru thin films and enhances the etch slope. In $O_2$+10% $CF_4$ plasma, the etch rate of Ru thin films increases up to 10% $CF_4$ but decreases with increasing $CF_4$ mixing ratio.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1246_1247
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• 2009

Effects of hydrogen and oxygen additives on structural, optical, and electrical properties of ZnO films were extensively examined. ZnO films were deposited using RF sputtering by varying the gas mixing ratio of $H_2$ and $O_2$. Optical transmittances at visible region, electrical resistivities, and micro-structures of ZnO films were characterized in terms of the kind and amount of additive gases. It was observed that the material properties of ZnO films required for their use in transparent thin film transistors, such as approximately $10^3{\Omega}cm$ in resistivity and higher than 85% in transmittance, can be achieved by controlling the gas mixing ratio of $O_2/H_2$ (sccm) in the range of 2/2~2/8.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.5
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• pp.218-224
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• 2011

LAS ($Li_2O-Al_2O_3-SiO_2$) ceramics were sintered by a solid-state reaction. $CaCO_3$ and $ZrO_2$ were added to the ${\beta}$-spodumene ($Li_2O-Al_2O_3-4SiO_2$) composition of the LAS system for enhancement of sintering behavior and mechanical strength, respectively. We have investigated the sintering characteristics, microstructures, mechanical properties and thermal expansion characteristics according to the change of the amount of additive and sintering temperature of the ${\beta}$-spodumene. At 0.1 mol% $CaCO_3$, the densification of ${\beta}$-spodumene was significantly improved. At 0.04 mol% $ZrO_2$, the strength of ${\beta}$-spodumene was also improved. For all the selected all compositions, the thermal expansion coefficient was measured by a dilatometer, which revealed 1.2 to $1.7{\times}10^6/^{\circ}C$.

• Journal of Environmental Health Sciences
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• v.20 no.1
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• pp.62-67
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• 1994

Introduction : Recently, water and environmental pollution becomes serious social problem and high technology makes this pollution accelerate. Hydrogen sulfide, the main subject of our research, is one of the most dangerous air pollutant like SO$_x$ and NO$_x$. The major contaminant in coal gasification is H$_2$S, which is very toxic, hazardous and extremely corrosive. Therefore, control of hydrogen sulfide to a safe level is essential. Although commercial desulfurization process called liquid scrubbing is effective for removal of H$_2$S, it has drawbacks, the loss of sensible heat of the gas and costly wastewater treatment. Many investigations are carried out about high-temperature removal ol H$_2$S in hot coal-derived gas using metal oxide or mixed metal qxide sorbents. It was reported that ZnO was very effective sorbent for H2S removal, but it has big flaw to vaporize elemental zinc above 600\ulcorner \ulcorner As alternative, metal oxides such as CaO, $Fe_2O_3$, TiO$_2$ and CuO were added to ZnO. Especially, different results are reported for $Fe_2O_3$ additive. Tamhankar et al. reported SiO$_2$ with 45 wt% $Fe_2O_3$ sorbent is favorable for removal of H$_2$S and regeneration.

• Journal of Powder Materials
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• v.27 no.5
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• pp.394-400
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• 2020

Molybdenum trioxide (MoO₃) is used in various applications including sensors, photocatalysts, and batteries owing to its excellent ionic conductivity and thermal properties. It can also be used as a precursor in the hydrogen reduction process to obtain molybdenum metals. Control of the parameters governing the MoO₃ synthesis process is extremely important because the size and shape of MoO₃ in the reduction process affect the shape, size, and crystallization of Mo metal. In this study, we fabricated MoO₃ nanoparticles using a solution combustion synthesis (SCS) method that utilizes an organic additive, thereby controlling their morphology. The nucleation behavior and particle morphology were confirmed using ultraviolet-visible spectroscopy (UV-vis) and field emission scanning electron microscopy (FE-SEM). The concentration of the precursor (ammonium heptamolybdate tetrahydrate) was adjusted to be 0.1, 0.2, and 0.4 M. Depending on this concentration, different nucleation rates were obtained, thereby resulting in different particle morphologies.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.05a
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• pp.1-4
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• 1994

In this study. the microwave dielectric properties, such at dielectric constant(${\varepsilon}_{\gamma}$), unloaded quality factor multiplied with resonant frequency($Q_{u}$.f), and temperature coefficient of resonant frequency(${\tau}_{f}$), were investigated for the low-temperature sintered (Pb, Ca)$ZrO_3$ with $V_2O_{5}$ additives as well as structural properties. As a result, (Pb,Ca)ZrO$_3$ with 0.2 wt% $V_2O_{5}$ additive, sintered at $1200^{\circ}C$, showed good properties like ${\varepsilon}_{\gamma}$ 109, $Q_{u}$.f 2736 GHz, and ${\tau}_{f}$ -2.94 ppm/$^{\circ}C$. Especially ${\tau}_{f}$ was much better than ($Pb_{0.63}Ca_{0.37}$)$ZrO_3$ of which ${\tau}_{f}$ was known to be + 13.4 ppm/$^{\circ}C$, so it seems to be applicated in micorowave device components.

• Journal of Sensor Science and Technology
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• v.16 no.3
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• pp.197-201
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• 2007

The magnetron reactive ion etching (RIE) characteristics of polycrystalline (poly) 3C-SiC grown on $SiO_{2}$/Si substrate by APCVD were investigated. Poly 3C-SiC was etched by $CHF_{3}$ gas, which can form a polymer as a function of side wall protective layers, with additive $O_{2}$ and Ar gases. Especially, it was performed in magnetron RIE, which can etch SiC at a lower ion energy than a commercial RIE system. Stable etching was achieved at 70 W and the poly 3C-SiC was undamaged. The etch rate could be controlled from $20\;{\AA}/min$ to $400\;{\AA}/min$ by the manipulation of gas flow rates, chamber pressure, RF power, and electrode gap. The best vertical structure was improved by the addition of 40 % $O_{2}$ and 16 % Ar with the $CHF_{3}$ reactive gas. Therefore, poly 3C-SiC etched by magnetron RIE can expect to be applied to M/NEMS applications.

• Journal of Electrochemical Science and Technology
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• v.6 no.4
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• pp.121-130
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• 2015

The micro emulsion method has been successfully used for preparing perovskite LaCoO₃ with uniform, fine-shaped nanoparticles showing high activity as electro catalysts in oxygen reduction reactions (ORRs). They are, therefore, promising candidates for the air-cathode in metal-air rechargeable batteries. Since the activity of a catalyst is highly dependent on its specific surface area, nanoparticles of the perovskite catalyst are desirable for catalyzing both oxygen reduction and evolution reactions. Herein, LaCoO₃ powder was also prepared by sol-gel method for comparison, with a broad particle distribution and high agglomeration. The electro catalytic properties of LaCoO₃ and LaCoO₃-carbon Super P mixture layers toward the ORR were studied comparatively using the rotating disk electrode technique in 0.1 M KOH electrolyte to elucidate the effect of carbon Super P. Koutecky-Levich theory was applied to acquire the overall electron transfer number (n) during the ORR, calculated to be ~3.74 for the LaCoO₃-Super P mixture, quite close to the theoretical value (4.0), and ~2.7 for carbon-free LaCoO₃. A synergistic effect toward the ORR is observed when carbon is present in the LaCoO₃ layer. Carbon is assumed to be more than an additive, enhancing the electronic conductivity of the oxide catalyst. It is suggested that ORRs, catalyzed by the LaCoO₃-Super P mixture, are dominated by a 2+2-electron transfer pathway to form the final, hydroxyl ion product.

• The Journal of Natural Sciences
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• v.8 no.1
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• pp.53-59
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• 1995

Effects of sintering additives and sintering temperatures on the sintering behavior and mechanical properties of SiC whisker reinforced alumina composites have been investigated in this study. Dense (>95% TD) composites were obtained by using 2 wt% $Y_2O_3$ as liquid phase sintering additive. But only porous composite could be obtained when the sintering additives were MgO and $TiO_2$, which were known as the sintering additives for solid state sintering of alumina. Bending strength and fracture toughness were enhanced by reinforcement of SiC whisker. It is belived from the microstructure investigation that the enhanced by strength and toughness could be attribute to the reinforcing and grain growth inhibition effects of SiC whisker. After HIP treatment, fully dense composites were obtained and further enhanced mechanical properties achieved.

• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.554-559
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• 2007

In order to improve the reactivity for the direct synthesis of dimethyl carbonate (DMC) using methanol and carbon dioxide, the various additives were used in the DMC synthesis using $Ce_{0.8}Zr_{0.2}O_2$ catalyst, and then effect of the additives was investigated. The various additives were molecular sieves 3A and the compounds having the various functional groups such as sulfate, carbonate, nitrate and phosphate. As a result, the compound such as $K_2SO_4$ and $Na_2SO_4$ having sulfate group were the most effective additive among the various additives. When $K_2SO_4$ was used as an additive in the direct synthesis of DMC, the amount of DMC was about 0.91 mmol, which was the highest mount of DMC among using only-$Ce_{0.8}Zr_{0.2}O_2$ catalyst and the various additives.