• The Korean Journal of Ceramics
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• v.2 no.2
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• pp.95-101
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• 1996

Variations of the leakage current behaviors and interface potential barrier $({\Phi}_B)$ of rf-sputter deposited (Ba, Sr)$TiO_3$ (BST) thin films with thicknesses ranging from 20 nm to 150nm are investigated as a function of the thickness and bias voltages. The top and bottom electrodes are dc-sputter-deposited Pt films. ${\Phi}_B$ critically depends on the BST film deposition temperature, postannealing atmosphere and time after the annealing. The postannealing under $N_2$ atmosphere results in a high interface potential barrier height and low leakage current. Maintaining the BST capacitor in air for a long time reduces the ${\Phi}_B$ from about 2.4 eV to 1.6 eV due to the oxidation. ${\Phi}_B$ is not so dependent on the film thickness in this experimental range. The leakage conduction mechanism is very dependent on the BST film thickness; the 20 nm thick film shows tunneling current, 30 and 40 nm thick films show Shottky emission current.

• Clean Technology
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• v.8 no.4
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• pp.173-180
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• 2002

As a primary material for MLCC, $BaTiO_3$ particles coated with two additives in a core-shell structure were prepared in this study. This composite powder can not only reduce the VOC emission during MLCC manufacture but also increase the density and reliability of electronic products. The additives were $Y_2O_3$ and $MnCO_3$, whose composition information was obtained from domestic companies. It was observed that the surface of $BaTiO_3$ particles was uniformly as well as simultaneously coated by those two materials via urea-decomposition reaction over $70^{\circ}C$ as the reaction temperature. Elemental analysis indicated that the measured content of each additve was quite close to the designated value. The effect of polymeric dispersant such as PVP, on the coating characteristics was not as significant as expected.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.3
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• pp.57-61
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• 2016

In order to protect the solar cells from the moisture and oxygen, we evaluated the electrical and optical properties for the $Cu(In,Ga)Se_2$ (CIGS) solar cells which were prepared by the spray coating method. Generally, the EVA (ethylene-vinyl acetate) films are laminated to protect the CIGS flexible solar cells, which results in a high cost process due to complicated devices. In this study, we tried to prepare the protection layers of the flexible CIGS flexible solar cells by using spray coating method instead of conventional laminating films in order to reduce the device weight as well as the process time. The CIGS solar cells with spray coating method showed an enhanced efficiency than the before treated sample (2.77% to 2.93%) and relatively proper water vapor transmission rate of the solar cells about 62.891 gm/[$m^2-day$].

• Applied Chemistry for Engineering
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• v.32 no.6
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• pp.695-699
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• 2021

In this study, Selective Catalytic Reduction on Diesel Particulate Filter (SDPF) after-treatment system was introduced to simultaneously remove NO_x and Particulate Matters (PM) emitted from trucks and special cargo vehicles using old engine. First, in order to select an Selective Catalytic Reduction (SCR) catalyst for SDPF, the de-NO_x performance of V/TiO₂ and Cu-Zeolite catalysts were compared, and the SCR catalyst characteristics were analyzed through Brunauer Emmett Teller (BET), X-ray Diffraction (XRD) and NH3-TPD (Temperature Programmed Desorption). From the activity test results, the Cu-zeolite catalyst showed the best thermal stability. For optimal coating of SDPF, slurry was prepared according to the target particle size. From the coating stability and back pressure test results of SDPF according to the amount of SCR coating, As a result of comparing coating stability, back pressure, and de-NOx performance by producing A, B, and C samples for each loading amount of the SDPF catalyst, the best results were found in the B sample. The engine dynamometer test was conducted for the optimal SDPF after-treatment system, and the test results satisfied Eu-5 regulations.

• Advances in materials Research
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• v.9 no.3
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• pp.219-231
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• 2020

The aim of this study is to investigate the durability of fly ash based geopolymer mortar with and without protective coatings in aggressive chemical environments. The source materials for geopolymer are Fly ash and Ground Granulated Blast furnace Slag (GGBS) and they are considered in the combination of 80% & 20% respectively. Two Molarities of NaOH solution were considered such as 8M and 10M. The ratio of binder to sand and Sodium silicate to Sodium hydroxide solution (Na₂SiO₃/NaOH) are taken as 1:2 and 2 respectively. The alkaline liquid to binder ratio is 0.4. Compressive strength tests were conducted at various ages of the mortar specimens. In order to evaluate the performance of coatings on geopolymer mortar under aggressive chemical environment, the mortar specimens were coated with two different types of coatings such as epoxy and Acrylic. They were then subjected to different chemical environments by immersing them in 10% standard solutions of each ammonium nitrate, sodium chloride and sulphuric acid. Drop in compressive strength as a result of chemical exposure was considered as a measure of chemical attack and the drop in compressive strength was measured after 30 and 60 days of chemical exposure. The compressive strength results following chemical exposure indicated that the specimens containing the acrylic coating proved to be more resistant to chemical attacks. The control specimen without coating showed a much greater degree of deterioration. Therefore, the application of acrylic coating was invariably much more effective in improving the compressive strength as well as the resistance of mortar against chemical attacks. The results also indicated that among all the aggressive attacks, the sulphate environment has the most adverse effect in terms of lowering the strength.

• Journal of Microbiology and Biotechnology
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• v.14 no.6
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• pp.1105-1113
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• 2004

Disinfection of a waterborne pathogenic protozoa, Giardia lamblia, by the conventional chlorine method has been known to be difficult. An alternative disinfection has been carried out by using a UV -light illuminating optical­fiber photoreactor. Light intensity diffused from one piece of a clad-removed optical-fiber was $1- 1.5{\mu}Em^{-2}s^{-1}$. Disinfection capability in a UV -light irradiated optical-fiber reactor suspended with 0.01 g $TiO_{2}\;dm^{-3}$ was 1.4 times that in the same reactor without $TiO_{2}$ photocatalysts. To resolve the absorption and scattering of UV light by the particles themselves as well as the difficulty of recycling particles in the slurry­type reactor, $TiO_{2}$ which was obtained by a hydrothermal method, was immobilized on clad-removed optical fibers. Such pretreatment of fiber surface resulted in an excellent transparency, which enhanced the UV light to diffuse laterally from a fiber surface. Coating time of the prepared solution by the hydrothermal method was not effective after more than two times. Disinfection capability in the $TiO_{2}$-immobilized optical-fiber reactor was $83\%$ in 1 h at $40^{\circ}C$, which was slightly higher than $76\%$ at $22^{\circ}C$ and $68\%$ at $10^{\circ}C$. Disinfection capability at $22^{\circ}C$ increased from $74\%$ at an initial pH of 3.4, through $76\%$ at pH 6.5, to $87\%$ at an initial pH of 10. Oxygen supply with air-flow rate of 5 $cm^3\;min^{-1}$ did not seem to increase the disinfection capability with UV /immobilized $TiO_2$.

• Corrosion Science and Technology
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• v.17 no.3
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• pp.101-108
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• 2018

AA7010 is an Al-Zn-Mg-Cu alloy containing Zr, developed as an alternate to traditional AA7075 alloy owing to their high strength combined with better fracture toughness. It is necessary to improve the corrosion resistance and surface properties of the alloy by incorporating plasma electrolytic oxidation (PEO) method. AA7010-T7452 aluminum alloy has been processed through the forging route with multi-stage working operations, and was coated with $10{\mu}m$ thick $Al_2O_3$ ceramic aluminina coating using the plasma electrolytic oxidation (PEO) method. The corrosion, stress corrosion cracking (SCC) and nano-mechanical behaviours were examined by means of potentiodynamic polarization, slow strain rate test (SSRT) and nano-indentation tests. The results indicated that the additional thermomechanical treatment during the forging process caused a fully recrystallized microstructure, which lead to the poor environmental cracking resistance of the alloy in 3.5% NaCl solution, despite the overaging treatment. Although the fabricated PEO coating improved general corrosion resistance, the brittle nature of the coating did not provide any improvement in SCC resistance of the alloy. However, the hardness and elastic modulus of the coating were significantly higher than the base alloy.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.12 no.1
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• pp.62-68
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• 1999

Ferroelectric $Sr_{0.7}/B_{2.3}(Ta_{1-x}Nb_x)_2O_9$(x=0, 0.1, 0.2, 0.3) thin films were deposited on $Pt/SiO_2/Si$ substrate by MOD(Metalorganic Decomposition) process. Metal carboxylate and metal alkoxide were used as precursors, and 2-methoxyethanol, xylene as solvents. After spin coating, thin films were pre-annealed at $400^{\circ}C$, followed by RTA(Rapid Thermal Annealing) and final annealing at $800^{\circ}C$ in oxygen atmosphere. These procedures were repeated three times to obtain thin films with the thickness of $2000{\AA}$. To enhance the nucleation and growth of layered-perovskite phase, thin films were rapid-thermally annealed above $720^{\circ}C$ in oxygen atmosphere. As RTA temperature increased, fluorite phase was transformed to layered-perovskite phase. And the change of Nb contents affected dielectric / electrical properties and microstructure. The ferroelectric characteristics of $Sr_{0.7}/B_{2.3}(Ta_{1-x}Nb_x)_2O_9$ thin film were Pr=8.67 $\mu{C}/cm^2$, Ec=62.4kV/cm and $I_{L}=1.4\times10^{-7}A/cm^2$ at the applied voltage of 5V, respectively.

• Progress in Superconductivity
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• v.8 no.1
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• pp.22-26
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• 2006

Total Fluorine content in the precursor solution for MOD processing of YBCO coated conductors can be significantly reduced by synthesizing precursor solution with F-free Y & Cu precursor and Barium trifluoroacetate(TFA). It was shown that crack-free and uniform precursor films were formed after calcinations in humidified oxygen atmosphere. Less than 2 hours are required to finish the calcination process, and XRD measurement shows that $BaF_2,\;CuO,\;and\;Y_2O_3$ are major constituent of calcined precursor films. Film thickness after calcination was measured to be ${\sim}2.8$ um by applying slot-die coating method. In particular, addition of Samarium shows critical current of Ic=226 A/cm-w($Jc=3.4\;MA/cm^2$). Also discussed are recent developments in the reel-to-reel processing using F-free Y & Cu precursor solutions. It is shown that uniform and fast processing route to YBCO coated conductor with high Ic can be provided by employing F-free Y & Cu precursor solutions in MOD process.

• Applied Chemistry for Engineering
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• v.24 no.3
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• pp.314-319
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• 2013

In this study, nitrogen doped $TiO_2$ ($N-TiO_2$) coated on an activated carbon pellet (ACP) was prepared using sol-gel and the solid state heat treatment of urea to improve the removal property of volatile organic compounds (VOCs). To explore the visible light photocatalytic activity of the ACP under the light emitting diods (LED), the removal property of benzene gas was characterized by gas chromatography. The SEM and BET results show that the increment of titanium tetra isopropoxide contents leads to the increased $TiO_2$ coating amount of ACP surface and decreased specific surface area. From the results of benzene gas removal, the breakthrough time of ACP10 increased about 2 times compared to that of the ACP. The improved performance was attributed to the $N-TiO_2$ coating on ACP surface, which could be more effective to remove benzene gas under the condition of LED lamp.