• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.2
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• pp.45-50
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• 2015

Compositionally graded AlGaN epilayer was grown by HVPE (hydride vapor phase epitaxy) on (0001) c-plane sapphire substrate. During the growth of graded AlGaN epilayer, the temperatures of source and the growth zone were set at $950^{\circ}C$ and $1145^{\circ}C$, respectively. The growth rate of graded AlGaN epilayer was about 100 nm/hour. The changing of Al contentes was investigated by field emission scanning electron microscope (FE-SEM) and energy dispersive spectroscopy (EDS). From the result of atomic force microscope (AFM), the average of roughness in 2 inch substrate of graded AlGaN epilayer was a few nanometers scale. X-ray diffraction (XRD) with the result that the AlGaN (002) peak ($Al_{0.74}Ga_{0.26}N$) and AlN (002) peak were appeared. It seems that the graded AlGaN epilayer was successfully grown by the HVPE method. From these results, we expect to use of the graded AlGaN epilayer grown by HVPE for the application of electron and optical devices.

• Journal of the Korean institute of surface engineering
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• v.41 no.6
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• pp.292-300
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• 2008

Dental implant system is composed of abutment, abutment screw and implant fixture connected with screw. The problems of loosening/tightening and stability of abutment screw depend on surface characteristics, like a surface roughness, coating materials and friction resistance and so on. For this reason, surface treatment of abutment screw has been remained research problem in prosthodontics. The purpose of this study was to investigate the stability of TiN and WC coated dental abutment screw, abutment screw was used, respectively, for experiment. For improving the surface characteristics, TiN and WC film coating was carried out on the abutment screw using EB-PVD and sputtering, respectively. In order to observe the coating surface of abutment screw, surfaces of specimens were characterized, using field emission scanning electron microscope(FE-SEM) and energy dispersive x-ray spectroscopy(EDS). The stability of TiN and WC coated abutment screw was evaluated by potentiodynamic, and cyclic potentiodynamic polarization method in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The corrosion potential of TiN coated specimen was higher than those of WC coated and non-coated abutment screw. Whereas, corrosion current density of TiN coated screws was lower than those of WC coated and non-coated abutment screw. The stability of screw decreased as following order; TiN coating, WC coating and non-coated screw. The pitting potentials of TiN and WC coated specimens were higher than that of non-coated abutment screw, but repassivation potential of WC coated specimen was lower than those of TiN coated and non-coated abutment screws due to breakdown of coated film. The degree of local ion dissolution on the surface increased in the order of TiN coated, non-coated and WC coated screws.

• Journal of Conservation Science
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• v.28 no.2
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• pp.119-129
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• 2012

Excavated textiles provide very important research data on the costume culture of the Joseon dynasty. In particular, dyed textiles are indispensable for textile conservation research and for restoration of remains as well as for general costume culture research. Unfortunately, a prolonged burial environment causes the colors to change and gradually fade after excavation. Therefore, it is very difficult to identify the original color. In this study, natural dyed samples of red, yellow, purple and blue were prepared and analyzed using HPLC-PDA. Dyes of colorants extracted from excavated textile remains were analyzed by HPLC. In addition, mordants were analyzed using (SEM-EDX) in order to estimate the original color. The 16~17th Century's three samples were analyzed, sample 1, and 2 from Eunjin Song's Song Mun-Chang excavated at the Songchon-dong in Daejeon, and sample 3 from Yeosan Song's Song, Hee-Jong excavated at the Mokdal-dong in Daejeon. From the HPLC results, alizarin, purpurin, and indigo were detected on sample 1, alizarin and purpurin on sample 2, ellagic acid and indigo on sample 3. Therefore they were dyed with madder and indigo (sample 1), madder (sample2), pomagranted and indigo (sample 3). Al mordant was identified on three samples.

• Journal of Veterinary Clinics
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• v.27 no.1
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• pp.93-96
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• 2010

We describe a case of enterolithiasis in an eight-year-old male Grant's zebra (Equus burchelli boehmi) that died after a 10-day history of depression, anorexia, dehydration and colic. On necropsy, an enterolith was discovered at the conjunction of the descending colon and the rectum. The spherical enterolith weighed 1,660 g and was $13.5cm{\times}8cm$ in size. According to scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), the nidus consisted primarily of $SiO_2$ with outer layers of magnesium and phosphate. The formation of enteroliths is closely related to diet. We suggest that this captive zebra's diet, which consisted primarily of alfalfa hay with mineral supplements, was the cause of enterolithiasis in this case. This is the first report of enterolithiasis in a captive equid in Korea. Our findings provide information valuable for the development of dietary guidelines to prevent enterolithiasis in captive wild equids.

• Applied Chemistry for Engineering
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• v.27 no.5
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• pp.502-507
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• 2016

This study was conducted to develop novel antimicrobial nano-composites, with the aim of fully utilizing antimicrobial properties of multi-walled carbon nanotubes (MWCNTs), nickel (Ni) and zinc oxide (ZnO). Ni coated-MWCNTs (Ni-CNT) were prepared and evaluated for their potential application as an antimicrobial material for inactivating bacteria. Field emission scanning electron microscopy (FE-SEM), and X-ray energy dispersive spectroscopy (EDS) were used to characterize the Ni coating and morphology of Ni-CNT. Staphylococcus aureus (S. aureus) and Escherichia coil (E. coil) were employed as the target bacterium on antimicrobial activities. Comparing with the nitric acid treated MWCNTs and Ni-CNT which have been previously reported to possess antimicrobial activity towards S. aureus and E. coil, Ni-CNT/ZnO exhibited a stronger antimicrobial ability. The nickel coating was confirmed to play an important role in the bactericidal action of Ni-CNTs/ZnO composites. Also, the addition of ZnO to the developed nanocomposite is suggested to improve the antimicrobial property.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.2
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• pp.185-192
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• 2010

The objective of this study was to investigate the effectiveness of stabilization for army firing range soil highly contaminated with Pb (total Pb: 29,000 mg/kg) using calcined waste oyster shells. The calcination was conducted to activate quicklime from calcite. In order to evaluate the effectiveness of calcination, both natural oyster shells (NOS) and calcined oyster shells (COS) were applied to the Pb contaminated soil. Stabilization was conducted by mixing the contaminated soil with oyster shell media at 5-20 wt% and cured for 28 days. Following 28 days of curing, Pb leachability was measured based on the Korean Standard Test method (0.1 N HCl extraction). The treatment results showed that the COS treatment outperformed the NOS treatment. All of the NOS treatments failed to meet the Korean warning standard of 100 mg/kg. However, the Pb concentrations were significantly reduced to 47 mg/kg and 3 mg/kg upon 15 wt% and 20 wt% COS treatments, respectively which passed the Korean warning standard. Moreover, -#20 mesh materials were more effective than the -#10 mesh materials in effectively reducing Pb leachability. The scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDX) results indicated that Pb immobilization was strongly linked to Al and Si.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.2
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• pp.108-113
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• 2013

Chalcopyrite material $CuInSe_2$ (CIS) is known to be a very prominent absorber layer for high efficiency thin film solar cells. Current interest in the photovoltaic industry is to identify and develop more suitable materials and processes for the fabrication of efficient and cost-effective solar cells. Various processes have been being tried for making a low cost CIS absorber layer, this study obtained the CIS nanoparticles using commercial powder of 6 mm pieces for low cost CIS absorber layer by high frequency ball milling and cryogenic milling. And the CIS absorber layer was prepared by paste coating using milled-CIS nanoparticles in glove box under inert atmosphere. The chalcopyrite $CuInSe_2$ thin films were successfully made after selenization at the substrate temperature of $550^{\circ}C$ in 30 min, CIS solar cell of Al/ZnO/CdS/CIS/Mo structure prepared under various deposition process such as evaporation, sputtering and chemical vapor deposition respectively. Finally, we achieved CIS nanoparticles solar cell of electric efficient 1.74 % of Voc 29 mV, Jsc 35 $mA/cm^2$ FF 17.2 %. The CIS nanoparticles-based absorber layers were characterized by using EDS, XRD and HRSEM.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.353-358
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• 2013

The hot corrosion behavior of plasma sprayed 4 mol% $Y_2O_3-ZrO_2$ (YSZ) thermal barrier coatings (TBCs) with volcanic ash is investigated. Volcanic ash that deposited on the TBCs in gas-turbine engines can attack the surface of TBCs itself as a form of corrosive melt. YSZ coating specimens with a thickness of 430-440 ${\mu}m$ are prepared using a plasma spray method. These specimens are subjected to hot corrosion environment at $1200^{\circ}C$ with five different duration time, from 10 mins to 100 h in the presence of corrosive melt from volcanic ash. The microstructure, composition, and phase analysis are performed using Field emission scanning electron microscopy, including Energy dispersive spectroscopy and X-ray diffraction. After the heat treatment, hematite ($Fe_2O_3-TiO_2$) and monoclinic YSZ phases are found in TBCs. Furthermore the interface area between the molten volcanic ash layers and YSZ coatings becomes porous with increases in the heat treatment time as the YSZ coatings dissolved into molten volcanic ash. The maximum thickness of this a porous reaction zone is 25 ${\mu}m$ after 100 h of heat treatment.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.3
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• pp.96-102
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• 2020

In this paper, AlN epilayers on 6H-SiC (0001) substrate are grown by mixed source hydride vapor phase epitaxy (MS-HVPE). AlN epilayer of 0.5 ㎛ thickness was obtained with a growth rate of 5 nm per hour. The surface of AlN epilayer grown on 6H-SiC (0001) substrate was investigated by field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). Dislocation density was considered through HR-XRD and related calculations. A fine crystalline AlN epilayer with screw dislocation density of 1.4 × 10⁹ cm^-2 and edge dislocation density of 3.8 × 10⁹ cm^-2 was confirmed. The AlN epilayer on 6H-SiC (0001) substrate grown by using the mixed source HVPE method could be applied to power devices.

• Korean Journal of Soil Science and Fertilizer
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• v.46 no.1
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• pp.8-15
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• 2013

Little research has been conducted to explore the heavy metal removal potential of biochar. The adsorption characteristics of heavy metals by sesame waste biochar (pyrolysis at $600^{\circ}C$ for 1 hour) as heavy metal absorbent were investigated. The sesame waste biochar was characterized by SEM-EDS and FT-IR, and heavy metal removal was studied using Freundlich and Langmuir equations. The removal rates of heavy metals were higher in the order of Pb>Cu>Cd>Zn, showing that the adsorption efficiency of Pb was higher than those of any other heavy metals. Freundlich and Langmuir adsorption isotherms were used to model the equilibrium adsorption data obtained for adsorption of heavy metals on biochar produced from sesame waste. Pb, Cu, Cd and Zn equilibrium adsorption data were fitted well to the two models, but Pb gave a better fit to Langmuir model. Heavy metals were observed on the biochar surface after adsorption by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Main functional groups were aromatic C=O ring (at $1160cm^{-1}$, $1384cm^{-1}$ and $1621cm^{-1}$) by FT-IR analysis. Thus, biochar produced from sesame waste could be useful adsorbent for treating heavy metal wastewaters.