• Journal of the Korean Society for Heat Treatment
• /
• v.33 no.3
• /
• pp.129-134
• /
• 2020

Due to excellent properties such as high specific strength and low density, application of magnesium alloys have been rapidly increased. However, magnesium alloy has a serious problem that is easily oxidized when exposed to high-temperature. For this reason, magnesium alloys have been generally used for SF6 gas such as protective cover gas in casting and melting, but it has been reported that this gas has a serious influence on global warming. Therefore, many researchers have been studied to improve the oxidation resistance of magnesium alloy. It was reported that addition of Be, Ca and CaO in magnesium alloy can improve the oxidation properties. In this study, the possibility of improving the oxidation resistance by adding CaO extracted from oyster shells was investigated. Oyster shells were completely decomposed into CaO and CO₂ by annealing. With the addition of CaO, a coexistence region of MgO + CaO was formed in the oxide layer and its thickness was also reduced.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.211-211
• /
• 2011

Nanostructures, with a diversity of shapes, built on substrates have been developed within many research areas. Lithography is one powerful, but complex, technique to make structures at the nanometer scale, such as platinum nanowires for studying CO catalytic reactions [1], or aluminum nanodisks for studying the plasmon effect [2]. In this work, we approach a facile method to construct nanostructures using noble metals on a titania thin film by using self-assembled structures as a pattern. Here, a large-scale silica monolayer is transferred to the titania thin film substrates using a Langmuir-Blodgett trough, followed by the deposition of a thin transition metal layer. Owing to the hexagonal close-packed structure of the silica monolayer, we would obtain a metal nanostructure that includes separated metallic triangles (islands) after removing the patterning silica beads. This nanostructure can be employed to investigate the role of metal-oxide interfaces in CO catalytic reactions by changing the patterning silica particles with different sizes or by replacing the oxide support. The morphology and chemical composition of the structure can be characterized by scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. In addition, we modify these islands to a connected island structure by reducing the silica size of the patterning monolayer, which is utilized to generating hot electron flow based on the localized surface plasmon resonance effect of the metal nanostructures.

• Transactions on Electrical and Electronic Materials
• /
• v.13 no.6
• /
• pp.305-309
• /
• 2012

In this study, ZnO nanorods and $SnO_2$-CuO heterogeneous oxide were grown on membrane-type gas sensor platforms and the sensing characteristics for carbon monoxide (CO) were studied. Diaphragm-type gas sensor platforms with built-in Pt micro-heaters were made using a conventional bulk micromachining method. ZnO nanorods were grown from ZnO seed layers using the hydrothermal method, and the average diameter and length of the nanorods were adjusted by changing the concentration of the precursor. Thereafter, $SnO_2$-CuO heterogeneous oxide thin films were grown from evaporated Sn and Cu thin films. The average diameters of the ZnO nanorods obtained by changing the concentration of the precursor were between 30 and 200 nm and the ZnO nanorods showed a sensitivity value of 21% at a working temperature of $350^{\circ}C$ and a carbon monoxide concentration of 100 ppm. The $SnO_2$-CuO heterogeneous oxide thin films showed a sensitivity value of 18% at a working temperature of $200^{\circ}C$ and a carbon monoxide concentration of 100 ppm.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.19 no.2
• /
• pp.225-231
• /
• 2021

The reaction between Li₂CO₃ and Cl₂ was investigated to verify its occurrence during a carbon-anode-based oxide reduction (OR) process. The reaction temperature was identified as a key factor that determines the reaction rate and maximum conversion ratio. It was found that the reaction should be conducted at or above 500℃ to convert more than 90% of the Li₂CO₃ to LiCl. Experiments conducted at various total flow rate (Q) / initial sample weight (W_i) ratios revealed that the reaction rate was controlled by the Cl₂ mass transfer under the experimental conditions adopted in this work. A linear increase in the progress of reaction with an increase in Cl₂ partial pressure (pCl₂) was observed in the pCl₂ region of 2.03-10.1 kPa for a constant Q of 100 mL·min^-1 and W_i of 1.00 g. The results of this study indicate that the reaction between Li₂CO₃ and Cl₂ is fast at 650℃ and the reaction is feasible during the OR process.

• Resources Recycling
• /
• v.11 no.5
• /
• pp.21-23
• /
• 2002

A new process based on the co-precipitation method was developed fer removing harmful impurities during Mn-Zn ferrite production such as $SiO_2$ and P from waste pickle liquor. By this process a final result of less than 100 ppm of $SiO_2$ and less than 10 ppm of P content in the ferric oxide is easily attained. Though Ca cannot be removed by this process, water rinsing of the ferric oxide is effective fer reducing Ca content to less than 100 pm. For further purification, the origins of each impurity must be investigated and then taken away.

• Journal of Sensor Science and Technology
• /
• v.29 no.2
• /
• pp.112-117
• /
• 2020

Xylene is a hazardous volatile organic compound that should be precisely measured to monitor indoor air quality. However, the selective and sensitive detection of ppm-level xylene using oxide-semiconductor gas sensors remains a challenge. In this study, pure and Cr-doped Co₃O₄ nanoparticles (NPs) were prepared using flame spray pyrolysis, and their gas-sensing characteristics to 5-ppm xylene at 250 ℃ were investigated. The 4 at% Cr-doped Co₃O₄ NPs exhibited a high gas response to 5-ppm xylene (resistance ratio to gas and air = 39.1) and negligible cross-responses to other representative and ubiquitous indoor pollutants such as ethanol, benzene, formaldehyde, carbon monoxide, and ammonia. In this paper, the enhancement of the gas response and selectivity of Co₃O₄ NPs to xylene by Cr doping was discussed in relation to the catalytic promotion of the gas-sensing reaction. This sensor can be used to monitor indoor xylene.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.3 no.2
• /
• pp.76-82
• /
• 2003

The robust stack storage node and sufficient cell capacitance for high performance is indispensable for 90 nm DRAM capacitor. For the first time, we successfully demonstrated MIS capacitor process integration for 90 nm DRAM technology. Novel cell layout and integration technology of 90 nm DRAM capacitor is proposed and developed, and it can be extended to the next generation DRAM. Diamond-shaped OCS with 1.8 um stack height is newly developed for large capacitor area with better stability. Furthermore, the novel $Al_2O_3/HfO_2$ dielectric material with equivalent oxide thickness (EOT) of 25 ${\AA}$ is adopted for obtaining sufficient cell capacitance. The reliable cell capacitance and leakage current of MIS capacitor is obtained with ~26 fF/cell and < 1 fA/ceil by $Al_2O_3/HfO_2$ dielectric material, respectively.

• Journal of Powder Materials
• /
• v.27 no.3
• /
• pp.193-197
• /
• 2020

Porous Cu-14 wt% Co with aligned pores is produced by a freeze drying and sintering process. Unidirectional freezing of camphene slurry with CuO-Co₃O₄ powders is conducted, and pores in the frozen specimens are generated by sublimation of the camphene crystals. The dried bodies are hydrogen-reduced at 500℃ and sintered at 800℃ for 1 h. The reduction behavior of the CuO-Co₃O₄ powder mixture is analyzed using a temperature-programmed reduction method in an Ar-10% H₂ atmosphere. The sintered bodies show large and aligned parallel pores in the camphene growth direction. In addition, small pores are distributed around the internal walls of the large pores. The size and fraction of the pores decrease as the amount of solid powder added to the slurry increases. The change in pore characteristics according to the amount of the mixed powder is interpreted to be due to the rearrangement and accumulation behavior of the solid particles in the freezing process of the slurry.

• Polymer(Korea)
• /
• v.34 no.3
• /
• pp.198-201
• /
• 2010

We have worked a surface modification to release a strong agglomeration of multi-walled carbon nanotube(MWCNT) and a incorporation of hydrophilic polymer to improve compatibility between MWCNT and polymers. Carboxylated MWCNT was easily obtained by acid treatment and the carboxylate was converted to acylchloride by thionyl chloride. Then, we tried one more synthesizing routes to achieve covalent bonds with poly(ethylene oxide) having amine end groups of low molecular weight. We measured the polymer content on the surface of MWCNT by TGA and observed increased diameter of MWCNT by SEM and TEM analysis.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.96.1-96.1
• /
• 2011

Solid oxide fuel cells(SOFCs) can convert the chemical energy of fuel into electricity directly. With the rising fuel prices and stricter emission requirement, SOFCs have been widely recognized as a promising technology in the near future. In this study, lean premixed flame using the orifice swirl burner was analyzed numerically and experimentally. We used the program CHEMKIN and the GRI 3.0 chemical reaction mechanism for the calculation of burning velocity and adiabatic flame temperature to investigate the effects of equivalence ratio on the adiabatic flame temperature and burning velocity respectively. Burning velocity of hydrogen was calculated by CHEMKIN simulation was 325cm/s, which was faster than that of methane having 42 cm/s at the same equivalence ratio. Also Ansys Fluent was used so as to analysis the performance with alteration of swirl structure and orifice mixer structure. This experimental study focused on stability and emission characteristics and the influence of swirl and orifice mixer in Solid Oxide Fuel Cell Systme burner. The results show that the stable blue flame with different equivalence ratio. NOx was measured below 20 ppm from equivalence ratios 0.72 to 0.84 and CO which is a very important emission index in combustor was observed below 160 ppm under the same equivalence region.