• Journal of Powder Materials
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• v.19 no.4
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• pp.310-316
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• 2012

Nanocrystalline $BaTiO_3$ powder could be synthesized by solid-state reaction using the mixture which was prepared by a high energy milling process in a bead mill for $BaCO_3$ and nanocrystalline $TiO_2$ powders mixture. Effect of the milling time on the powder characteristic of the synthesized $BaTiO_3$ powder was investigated. Nanocrystalline $BaTiO_3$ with a particle size of 50 nm was obtained at $800^{\circ}C$. High tetragonal $BaTiO_3$ powder with a tetragonality(=c/a) of 1.009 and a specific surface area of $7.6m^2/g$ was acquired after heat-treatment at $950^{\circ}C$ for 2 h. High energy ball milling was effective in decreasing the reaction temperature and increasing the tetragonality.

• Journal of Life Science
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• v.9 no.5
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• pp.581-589
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• 1999

This study was carried out to compare ozonation with photocatalysis degradation for removal Geosmin of algae byproduct. The change of pH was decresed from 7.02 to 2.8 after contact time 480 minute for ozonation. In case of UV-germicidal lamp, pH was very quickly increased from 7.02 to 7.5, but Halogen lamp did very slowly change pH. Geosmin degradation ratio was as following, UV-germicidal lamp/TiO2(100mg/L) O3>UV-germicidal lamp/TiO2(50mg/L)>UV-germicidal lamp(10W)>halogen lamp(50W). Instead of TiO2 suspension solution, Geosmin degradation ratio was very low using hollow bead and pellet as coated TiO2. As a result of identifing byproducts, ozonation generated three species of aldehyde such as 3-Heptanone and three species of alcohol such as Heptanal, but photocatalysis formed 1, 14-Tetradecanediol infinitesimally.

• Journal of Welding and Joining
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• v.14 no.6
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• pp.93-100
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• 1996

Effect of a flux composition on weld metal toughness in submerged arc welding with 60kgf/$\textrm{mm}^2$ grade C-Mo type wires was investigated and interpreted in terms of weld metal microstructure and hardenability. Flux workability was also studied by characterizing a weld bead profile. Compared to other weld metals, .weld metal used alumina basic flux with nickel showed lowest oxygen content, highest hardenability and the most acicular ferrite. The highest impact toughness of that weld metal, however, was attributed to the tough matrix due to the nickel rather than to the larger amount of acicular ferrite. Manganese silicate flux had better workability than alumina basic flux, showing broader welding conditions resulting in a depth-to-width ratio of 0.5. The composition of oxides in the weld metal was dependent on the flux composition, showing MnO-SiO$_2$-TiO in manganese silicate flux and MnO-SiO$_2$-Al$_2$O$_3$-TiO in alumina basic flux. MnO-SiO$_2$composition in both oxides was similar to a tephroite.

• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.30-35
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• 2023

The glass bead surface was coated using a TiO₂ sol, after which dry-treated (TB) and calcined (TBc) samples were prepared. Photocatalytic degradation of methylene blue and toluene, as well as characterization of the TiO₂ thin films, were carried out. The TiO₂ thin film of the TB sample had the same shape as the sponge foam, according to FE-SEM, XPS, and FTIR analyses, and contained both amorphous and crystalline TiO₂. On the other hand, crystalline TiO₂ was mainly present in the TiO₂ thin film of the TBc sample, and needle-shaped particles and tiny ones were mixed. The adsorption capacity for methylene blue and the degradation rate of the TBc sample were less than 10 % compared with those of the TB sample, and the adsorption capacity and degradation rate of the TBc sample decreased similarly as the amount of TiO₂ coating increased. The amount of toluene adsorption for the TBc sample (46 mg/g) was smaller than that of the TB sample with the same coating amount, but the degradation rate was similar. In the case of the TB sample, the degradation rate for toluene decreased less than the adsorption capacity as the amount of TiO₂ coating increased. This result is considered to be because, in the non-calcined TB sample, the active site reduction of the crystalline particles occurred less and the specific surface area of the amorphous texture decreased as the amount of TiO₂ coating increased.

• Journal of Industrial Technology
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• v.26 no.A
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• pp.181-188
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• 2006

In this study, we analyzed the effects of several process variables on the removal efficiencies of NO and $SO_2$ by the dielectric barrier discharge process combined with photocatalysts. The $TiO_2$ photocatalysts were coated onto the spherical-shaped glass beads as dielectric materials by the dip-coating method to analyze the effects of photodegradation reaction on the NO and $SO_2$ removal. As the voltage applied to the plasma reactor increases, or as the pulse frequency of applied voltage increases, the NO and $SO_2$ removal efficiencies increase. Also as the residence time increases, or as the initial concentration of NO decreases, the NO and $SO_2$ removal efficiencies increase. The higher the amount of $TiO_2$ particles coated onto the glass bead is, the larger the surface area of $TiO_2$ particles for the photodegradation reaction is and the NO and $SO_2$ are removed more quickly by the faster photodegradation reactions.

• Journal of environmental and Sanitary engineering
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• v.17 no.2
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• pp.26-33
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• 2002

Ultimate objective of industrial hygiene is the prevention of health impairment that may result from exposure to chemicals at workplace. Workers in solvent thinner-using occupation environment may be highly exposed to VOCs (volatile organic compounds) because solvent thinner has been used extensively such as painting, spraying, degreasing, coating and so on in Korea. The purpose of this study was to recognize, evaluate, and propose the control methods of VOCs from solvent thinner-using workplace. Five target volatile organic compounds (benzene, toluene, ethylbenzene, o-xylene, and m-xylene) were monitored in H company of Shiwa Industrial Complex and analyzed in perosnal, occupational indoor and outdoor during working hours simultaneously. Engineering control such as local ventilation should be made in considering the long-term exposure, though measured VOCs concentration did not exceed the workplace exposure standards. In addition, air cleaning device should be installed in local ventilation because Shiwa Industrial Complex has had the serious ambient air pollution. Currently, environmental purification using $TiO_2$ photocatalyst have attracted a great deal of attention with increasing number of recent environmental problems. In this study, $TiO_2$ sol coated on the ceramic bead was prepared by sol-gel method and the photodegradation of target compounds was investigated in gas phase by the exposure to UV-A lamp(365nm) in a batch system.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.16.1-16.1
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• 2011

$TiO_2$ is a promising material for gas sensors. To achieve high sensitivities, the material should exhibit a large surface-to-volume ratio and possess the high accessibility of the gas molecules to the surface. Accordingly, a wide variety of porous $TiO_2$ nanomaterials synthesized by wet-chemical methods have been reported for gas sensor applications. Nonetheless, achieving the large-area uniformity and comparability with well-established semiconductor production processes of the methods is still challenging. An alternative method is soft-templating which utilizes nanostructured inorganic or organic materials as sacrificial templates for the preparation of porous materials. Fabrication of macroporous $TiO_2$ films and hollow $TiO_2$ tubes by soft-templating and their gas sensing applications have been reported recently. In these porous materials composed of assemblies of individual micro/nanostructures, the form of links or necks between individual micro/nanostructures is a critical factor to determine gas sensing properties of the material. However, a systematic study to clarify the role of links between individual micro/nanostructures in gas sensing properties of a porous metal oxide matrix is thoroughly lacking. In this work, we have demonstrated a fabrication method to prepare highly-ordered, embossed $TiO_2$ films composed of anatase $TiO_2$ hollow hemispheres via soft-templating using polystyrene beads. The form of links between hollow hemispheres could be controlled by $O_2$ plasma etching on the bead templates. This approach reveals the strong correlation of gas sensitivity with the form of the links. Our experimental results highlight that not only the surface-to-volume ratio of an ensemble material composed of individual micro/nanostructures but also the links between individual micro/nanostructures play a critical role in evaluating the sensing properties of the material. In addition to this general finding, the facileness, large-scale productivity, and compatability with semiconductor production process of the proposed fabrication method promise applications of the embossed $TiO_2$ films to high-quality sensors.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.380-383
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• 2015

We prepared the $TiO_2$ layer with 0 ~ 4 wt% of polystyrene (PS) beads having a radius of 250 nm to increase the dye adsorption and energy conversion efficiency (ECE) of a dye sensitized solar cell (DSSC). Then, we fabricated DSSCs using $0.45cm^2$ active area. FE-SEM was used to characterize the microstructure consisting of $TiO_2$ layer and PS beads. UV-VIS-NIR was used to determine the optical absorbance of working electrodes (WEs). Solar simulator and potentiostat were used to determine the photovoltaic properties. We observed that pores having a radius of 250 nm were formed with the density of $0.15ea/{\mu}m^2$ in $TiO_2$ layers after conducting the sintering process. The absorbance in visible light regime was found to increase with the increase in the amount of PS beads. The ECE increased from 4.66% to 5.25% when the amount of PS beads was increased from 0 to 4 wt%. This is because the pores of PS beads increased the adsorption of dye. Our results indicate that the ECE of the DSSCs can be enhanced by the addition of an appropriate amount of PS beads into $TiO_2$ layers.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.E1
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• pp.29-36
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• 2002

The selective catalytic reduction (SCR) reaction of promoter catalysts was investigated in this study. A pure anatase type of TiO$_2$ was used as support. Activation measurement of prepared catalysts was practiced on a fixed reactor packing by the glass bead after filling up catalysts in 1/4 inch stainless tube. The reaction temperature was measured by K-type thermocouple and catalyst was heated by electric furnace. The standard compositions of the simulated flue gas mixture in this study were as follows: NO 1,780ppm, NH$_3$1,780ppm, $O_2$1% and $N_2$ as balance gas. In this study, gas analyzer was used to measure the outgassing gas. Catalyst bed was handled for 1hr at 45$0^{\circ}C$, and the reactivity of the various catalyst was determined in a wide temperature range. Conversion of NH$_3$/NO ratio and of $O_2$ concentration was practiced at 1,1.5 and 2, respectively. The respective space velocity were as follows . 10,000, 15,000 and 17,000 hr-1. It was found that the maximum conversion temperature range was in a 5$0^{\circ}C$. It was also found toi be very sensitive at space velocity, $O_2$ concentration, and NH$_3$/NO ratio. We also noticed that the maximum conversion temperature of (W, Mo, Sn) -V$_2$O$_{5}$/TiO$_2$ catalysts was broad. Specially WO$_3$-V$_2$O$_{5}$TiO$_2$2 catalyst appeared nearly 100% conversion at not only above 30$0^{\circ}C$ ut also below 25$0^{\circ}C$. At over 30$0^{\circ}C$, NH$_3$ oxidation decreased with decrease of surface excess oxygen. In addition, WO$_3$-V$_2$O$_{5}$TiO$_2$ catalyst did not appear to affect space velocity, $O_2$ concentration, and NH$_3$/NO ratio.ratio.

• Membrane Journal
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• v.21 no.1
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• pp.72-83
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• 2011

For advanced drinking water treatment of high turbidity water, we used the hybrid module that was composed of photocatalyst packing between outside of tubular ceramic microfiltration membrane and membrane module inside. Photocatalyst was PP (polypropylene) bead coated $TiO_2$ powder by CVD (chemical vapor deposition) process. Instead of natural organic matters (NOM) and fine inorganic particles in natural water source, modified solution was prepared with humic acid and kaolin. Water-back-flushing of 10 sec was performed per every period of 10 min to minimize membrane fouling. Resistance of membrane fouling ($R_f$) decreased and J increased as concentration of humic acid changed from 10 mg/L to 2 mg/L, and finally the highest total permeate volume ($V_T$) could be obtained at 2 mg/L. Then, treatment efficiencies of turbidity and $UV_{254}$ absorbance were above 98.5% and 85.7%, respectively. As results of treatment portions by membrane filtration, photocatalyst adsorption, and photo-oxidation in MF, MF + $TiO_2$, and MF + $TiO_2$ + UV processes, turbidity was treated little by photocatalyst adsorption, and photo-oxidation. However, treatment portions of humic acid by adsorption and photo-oxidation were above 10.7 and 8.6%, respectively.