• Journal of the Korean Society for Heat Treatment
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• v.33 no.1
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• pp.13-19
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• 2020

Annealing effects on the properties of Bi-doped ZnO thin films were investigated. Bi- doped ZnO thin films were deposited on quartzs substrates at 300℃ by using radio-frequency magnetron sputtering system. Post heat treatments at 600, 700, and 800℃ were performed to evaluate the effect of annealing temperatures on the structural, optical, and electrical properties of Bi-doped ZnO thin films. FE-SEM images showed the dramatic surface morphology changes by rearrangement of elements at high heat treatment temperature of 800℃. X-ray diffraction analysis indicated that the peaks of the Bi-doped ZnO thin films were same as the peaks of the (002) planes of ZnO peak-positioned at 2θ=34.0° and peak intensities and FWHMs were improved as the annealing temperatures increased. The optical transmittance was improved with increasing annealing temperatures and was over 80% in the wavelength region between 435 and 1100 nm at the annealing temperature of 700 and 800℃. With increasing annealing temperature, the electron concentrations and electron mobilities were increased. On the other hand, electric resistivity of the films were decreased with increasing annealing temperatures. These results showed that the heat treatment temperature is an important parameter to improve the structural, optical, and electrical properties of Bi-doped ZnO thin films.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1794-1796
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• 1998

In this study, the $SO_2$ addition effect on NOx removal has been conducted from a combustion flue gases by the do corona discharge-activated radical shower systems. The simulated flue gases were consisted of NO-O_2-$N_2$, NO-$CO_2-N_2-O_2$ and $NO-SO_2-CO_2-Na-O_2$([NO]o:200ppm and $[SO_2]o$:800ppm). The injection gases used as radical source gases were $NH_3$-Ar-air. $SO_2$ and NOx removal efficiency and the other by-products were measured by Fourier Transform Infrared(FTIR) as well as $SO_2$. NOx and $NO_2$ gas detectors. By-product aerosol particles were also observed by Condensation Nucleation Particle Counter(CNPC) and SEM images after sampling. The results showed that asignificant aerosol Particle formation was observed during a removal operation in corona radical shower systems. The NOx removal efficiency significantly increased with increasing applied voltage and $NH_3$ molecule ratio. The $SO_2$ removal efficiency was not significantly effected by applied voltage and slightly increased with increasing $NH_3$ molecule ratio. The NOx removal efficiency for NO-$SO_2-CO_2-N_2-O_2$ was better than that for NO-$CO_2-N_2-O_2$.

• Transactions on Electrical and Electronic Materials
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• v.8 no.2
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• pp.67-72
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• 2007

High Pressure Micro Jet (HPMJ) pad conditioning system was investigated as an alternative to diamond disc conditioning in copper CMP. A series of comparative 50-wafer marathon runs were conducted at constant wafer pressure and sliding velocity using Rohm & Haas IC1000 and Asahi-Kasei EMD Corporation (UNIPAD) concentrically grooved pads under ex-situ diamond conditioning or HPMJ conditioning. SEM images indicated that fibrous surface was restored using UNIPAD pads under both diamond and HPMJ conditioning. With IC1000 pads, asperities on the surface were significantly collapsed. This was believed to be due to differences in pad wear rates for the two conditioning methods. COF and removal rate were stable from wafer to wafer using both diamond and HPMJ conditioning when UNIPAD pads were used. Also, HPMJ conditioning showed higher COF and removal rate when compared to diamond conditioning for UNIPAD. On the other hand, COF and removal rates for IC1000 pads decreased significantly under HPMJ conditioning. Regardless of pad conditioning method adopted and the type of pad used, linear correlation was observed between temperature and COF, and removal rate and COF.

• Corrosion Science and Technology
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• v.15 no.4
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• pp.182-188
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• 2016

Significant piping wall thinning caused by Flow-Accelerated Corrosion (FAC) and Erosion-Corrosion (EC) continues to occur, even after the Mihama Power Station unit 3 secondary pipe rupture in 2004, in which workers were seriously injured or died. Nuclear power plants in many countries have experienced FAC and EC-related cases in steam cycle piping systems. Korea has also experienced piping wall thinning cases including thinning in the downstream straight pipe of a check valve in a feedwater pump line, the downstream elbow of a control valve in a feedwater flow control line, and failure of the straight pipe downstream of an orifice in an auxiliary steam return line. Cause analyses were performed by reviewing thickness data using Ultrasonic Techniques (UT) and, Scanning Electron Microscope (SEM) images for the failed pipe, and numerical simulation results for FAC and EC cases in Korea Nuclear Power Plants. It was concluded that the main cause of wall thinning for the downstream pipe of a check valve is FAC caused by water vortex flow due to the internal flow shape of a check valve, the main cause of wall thinning for the downstream elbow of a control valve is FAC caused by a thickness difference with the upstream pipe, and the main cause of wall thinning for the downstream pipe of an orifice is FAC and EC caused by liquid droplets and vortex flow. In order to investigate more cases, additional analyses were performed with the review of a lot of thickness data for inspected pipes. The results showed that pipe wall thinning was also affected by the operating condition of upstream equipment. Management of FAC and EC based on these cases will focus on the downstream piping of abnormal or unusual operated equipment.

• Food Science and Biotechnology
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• v.15 no.1
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• pp.5-12
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• 2006

Degradation performance of environmentally friendly plastics that can be disintegrated by combination of sunlight, microbes in soil, and heat produced in landfills was evaluated for use in industries. Two multi-degradable master batches (MCC-101 and MCC-102 were manufactured, separately mixed with polyethylene using film molding machine to produce 0.025 mm thick films, and exposed to sunlight, microbes, and heat. Low- and high-density polyethylene (LDPE and HDPE) films containing MCC-101 and MCC-102 became unfunctional by increasing severe cleavage at the surface and showed high reduction in elongation after 40 days of exposure to ultraviolet light. LDPE and HDPE films showed significant physical degradation after 100 and 120 days, respectively, of incubation at $68{\pm}2^{\circ}C$. SEM images of films cultured in mixed mold spore suspension at $30^{\circ}C$ and 85% humidity for 30 days revealed accelerated biodegradation on film surfaces by the action of microbes. LDPE films containing MCC-l01 showed absorption of carbonyls, photo-sensitive sites, at $1710\;cm${-1}$ when exposed to light for 40 days, whereas those not exposed to ultraviolet light showed no absorption at the same frequency. MCC-101-based LDPE films showed much lower $M_w$ distribution after exposure to UV than its counterpart, due to agents accelerating photo-degradation contained in MCC-101.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.3
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• pp.118-122
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• 2018

Ceria ($CeO_2$) is a rare earth oxide, which has been widely investigated to improve the property. It is important to increase the surface area of $CeO_2$, because high surface area of $CeO_2$ can improve the catalytic ability. $CeO_2$ nanoparticles were synthesized by a solvothermal process. A discussion on the influence of solvent ratio and precursors on $CeO_2$ nanoparticles was performed. The size and degree of the agglomeration of the synthesized $CeO_2$ could be tuned by controlling those parameters. The average size and distribution of prepared $CeO_2$ powders was in the range of 3 to 13 nm and narrow, respectively. The XRD pattern showed that the synthesized $CeO_2$ powders were crystalline with cubic phase of $CeO_2$. The average particle size was calculated by Scherrer equation and FE-TEM images. The morphology of the synthesized $CeO_2$ particle was objected using FE-TEM and FE-SEM. Specific surface area of the synthesized $CeO_2$ was determined using BET (Brunauer-Emmett-Teller) equation.

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3767-3771
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• 2012

In this study, we investigate the potential use of $TiO_2@SiO_2$ and $ZnO@SiO_2$ core/shell nanoparticles (NPs) as effective UV shielding agent. In the typical synthesis, $SiO_2$ was coated over different types of $TiO_2$ (anatase and rutile) and ZnO by sol-gel method. The synthesized $TiO_2@SiO_2$ and $ZnO@SiO_2$ NPs were characterized by UV-Vis, XRD, SEM and TEM. The UV-vis absorbance and transmittance spectra of core@shell NPs showed an efficient blocking effect in the UV region and more than 90% transmittance in the visible region. XRD and SAED studies confirmed the formation of amorphous $SiO_2$ coated over the $TiO_2$ and ZnO NPs. The FESEM and TEM images shows that coating of $SiO_2$ over the surface of anatase, rutile $TiO_2$ and ZnO NPs resulted in the increase in particle size by ~30 nm. In order to study the UV light shielding capability of the samples, photocatalytic degradation of methylene blue dye on $TiO_2@SiO_2$ and $ZnO@SiO_2$ NPs was performed. Photocatalytic activity for both types of $TiO_2$ NPs was partially suppressed. In comparison, the photocatalytic activity of ZnO almost vanished after the $SiO_2$ coating.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.6
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• pp.759-764
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• 2011

Mixed-conducting oxide powders, $BaCe_{0.9}Y_{0.1}O_{2.95}$ (BCY) and $SrCe_{0.9}Y_{0.1}O_{2.95}$ (SCY) powders have been prepared by a solid-state reaction method. Xray diffraction patterns of the prepared powders showed the sharp peaks of the $BaCe_{0.9}Y_{0.1}O_{2.95}$ and $SrCe_{0.9}Y_{0.1}O_{2.95}$ phases. The oxide powders that were prepared by attrition milling showed rather large particles and severe necking between particles in FE-SEM images as well as residual reactant ($BaCO_3$) and secondary phases ($SrCeO_3$ and $CeO_2$) in XRD patterns. The oxide powders prepared using ball milling showed particles under approximately 500 nm and typical XRD patterns of the $BaCe_{0.9}Y_{0.1}O_{2.95}$ and $SrCe_{0.9}Y_{0.1}O_{2.95}$ phases. Ceramic membranes of the $BaCe_{0.9}Y_{0.1}O_{2.95}$ and $SrCe_{0.9}Y_{0.1}O_{2.95}$ phases were fabricated by the aerosol deposition method using the oxide powders synthesized.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.118-118
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• 2008

The oxide CMP has been applied to interlayer dielectric(ILD) and shallow trench isolation (STI) in chip fabrication. Recently the slurry used in oxide CMP being changed from silica slurry to ceria (cerium dioxide) slurry particularly in STI CMP, because the material selectivity of ceria slurry is better than material selectivity of silica slurry. Moreover, the ceria slurry has good a planarization efficiency, compared with silica slurry. However ceria abrasives make a material removal rate too high at the region of wafer center. Then we focuses on why profile of material removal rate is convex. The material removal rate sharply increased to 3216 $\AA$/min by $4^{th}$ run without conditioning. After $4^{th}$ run, material removal rate converged. Furthermore, profile became more convex during 12 run. And average material removal rate decreased when conditioning process is added to end of CMP process. This is due to polishing mechanism of ceria. Then the ceria abrasive remains at the pad, in particular remains more at wafer center contacted region of pad. The field emission scanning electron microscopy (FE-SEM) images showed that the pad sample in the wafer center region has a more ceria abrasive than in wafer outer region. The energy dispersive X-ray spectrometer (EDX) verified the result that ceria abrasive is deposited and more at the region of wafer center. Therefore, this result may be expected as ceria abrasives on pad surface causing the convex profile of material removal rate.

• KSBB Journal
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• v.24 no.4
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• pp.347-352
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• 2009

Ethanol extract (1.0 wt%) of Scutellaria baicalensis $G_{EORGE}$ practically satisfied CTFA (The cosmetics, Toiletry, and Fragrance Association) standard in its antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans which were inoculated in skin toner and skin lotion. At concentrations of the extract less than 1.0 wt% the survival rate was the best for S. aureus and the worst for P. aeruginosa. The antimicrobial effect seems to be due to the damage to the bacterial cell wall as evidenced by the images of a Field Emission-Scanning Electron Microscope. The extract also showed a high anti-oxidant effect, and superoxide dismutase (SOD)-like activity reached 80% at 1,000 ppm. These findings suggest that the extract of Scutellaria baicalensis $G_{EORGE}$ is applicable to cosmetics as a natural preservative and an anti-oxidant.