• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.6
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• pp.244-250
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• 2020

β-Tricalcium phosphate (β-TCP, Ca3(PO4)2) is a kind of biodegradable calcium phosphate ceramics with chemical and mineral compositions similar to those of bone. It is a potential candidate for bone repair surgery. To improve the bioactivity and osteoinductivity of β-TCP, various ions doped calcium phosphate have been studied. Among them, Iron is a trace element and its deficiency in the human body causes various problems. In this study, we investigated the effect of Fe ions on the structural variation, degradation behavior of β-TCP. Fe-doped β-TCP powders were synthesized by the coprecipitation method, and the heat treatment temperature was set at 925 and 1100℃. The structural analysis was carried out by Rietveld refinement using the X-ray diffraction results. Fe ions existed in a different state (Fe2+ or Fe3+) with different heat treatment temperatures, and the substitution sites (Ca-(4) and Ca-(5)) also changed with temperature. The degradation rate was fastest at Fe-doped β-TCP with heated at 1100℃. The cell viability behavior was also enhanced with the substitution of Fe ions. Therefore, the substitution of Fe ion has accelerated the degradation of β-TCP and improved the biocompatibility. It could be more utilized in biomedical devices.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.1
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• pp.37-42
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• 2021

The effect of chemical composition on the structural and thermal properties of TiZrN thin films was studied. As the Zr fraction in the deposited TixZr1-xN (x = 0.87, 0.82, 0.7, 0.6, and 0.28) increased, microstructural changes consisted of reduction in the grain size and a gradual transition from columnar structure to granular structure were observed. In addition, it was also confirmed that a gradual crystal phase transition from TiN to TiZrN has occurred as the Zr fraction increased up to 0.4. After heat treatment at 900℃, Ti0.82Zr0.18N and Ti0.7Zr0.3N layers were converted to a form in which rutile phase TiO2 and TiZrO4 oxides coexist, while Ti0.6Zr0.4N layer was converted to TiZrO4 oxide. Among the five compositions of TiZrN films, the Ti0.6Zr0.4N showed the best high temperature stability and produced a significant enhancement in the thermal oxidation resistance of Inconel 617 through suppressing the surface diffusion of Cr caused by thermal oxidation of the Inconel 617 substrate.

• Journal of Korea Society of Waste Management
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• v.35 no.7
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• pp.670-682
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• 2018

Engineered nanomaterials (ENMs) can be released to humans and the environment through the generation of waste containing engineered nanomaterials (WCNMs) and the use and disposal of nano-products. Nanoparticles can also be introduced intentionally or unintentionally into waste streams. This study examined WCNMs in domestic industries, and target nanomaterials, such as silicon dioxide, titanium oxide, zinc oxide, nano silver, and carbon nanotubes (CNTs), were selected. We tested 48 samples, such as dust, sludge, ash, and by-products from manufacturing facilities and waste treatment facilities. We analyzed leaching and content concentrations for heavy metals and hazardous constituents of the waste. Chemical compositions were also measured by XRD and XRF, and the unique properties of nano-waste were identified by using a particle size distribution analyzer and TEM. The dust and sludge generated from manufacturing facilities and the use of nanomaterials showed higher concentrations of metals such as lead, arsenic, chromium, barium, and zinc. Oiled cloths from facilities using nano silver revealed high concentrations of copper, and the leaching concentrations of copper and lead in fly ash were higher than those in bottom ash. In XRF measurements at the facilities, we detected compounds such as silicon dioxide, sulfur trioxide, calcium oxide, titanium dioxide, and zinc oxide. We found several chemicals such as calcium oxide and silicon dioxide in the bottom ash of waste incinerators.

• Animal Bioscience
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• v.34 no.4
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• pp.603-612
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• 2021

Objective: We have tested our hypothesis that inclusion of purified glycerol as a replacer of portions of dried distillers grain with solubles (DDGS) would affect growth performance, rumen fermentation and blood parameters, carcass and sensory traits, reducing sugar and glycogen contents, and volatile compound profiles in longissimus thoracis (LT) in Korean cattle steers. Methods: A total of 20 Korean cattle steers (27.0±0.2 months old; 647±10.5 kg body weight [BW]) were assigned to a conventional control group or a glycerol group (3.17% purified glycerol addition as a replacement for DDGS and molasses). The steers were individually allowed to receive the experimental concentrate at the daily amount of 1.5% of their individual BW and a total 1.0 of kg/d of rice straw twice daily. The feeding trial was conducted for a period of 20 weeks. Results: Glycerol supplementation (GS) increased (p = 0.001) concentrate intake. However, GS did not affect (p>0.05) average daily gain, feed efficiency, and ruminal volatile fatty acid concentrations. GS tended to increase (p≤0.10) serum glucose concentrations at the 16th and 20th weeks. GS decreased (p = 0.001) LT pH. GS did not affect (p>0.05) carcass traits and the chemical or physicochemical compositions, reducing sugar or glycogen contents, sensory traits, and most of volatile compounds in the LT. Conclusion: The inclusion of purified glycerol as a replacement for DDGS in the finishing diet did not affect growth performance, rumen fermentation parameters, and carcass quality in Korean cattle. The purified glycerol could be used as a substitute for other energy sources such as DDGS in beef cattle, depending on the price.

• The Journal of Advanced Prosthodontics
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• v.13 no.6
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• pp.385-395
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• 2021

PURPOSE. To characterize the microstructure of three yttria partially stabilized zirconia ceramics and to compare their hardness, indentation fracture resistance (IFR), biaxial flexural strength (BFS), and fatigue flexural strength. MATERIALS AND METHODS. Disc-shaped specimens were obtained from 3Y-TZP (Vita YZ HT), 4Y-PSZ (Vita YZ ST) and 5Y-PSZ (Vita YZ XT), following the ISO 6872/2015 guidelines for BFS testing (final dimensions of 12 mm in diameter, 0.7 and 1.2 ± 0.1 mm in thicknesses). Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were performed, and mechanical properties were assessed by Vickers hardness, IFR, quasi-static BFS and fatigue tests. RESULTS. All ceramics showed similar chemical compositions, but mainly differed in the amount of yttria, which was higher as the amount of cubic phase in the diffractogram (5Y-PSZ > 4Y-PSZ > 3Y-TZP). The 4Y- and 5Y-PSZ specimens showed surface defects under SEM, while 3Y-TZP exhibited greater grain uniformity on the surface. 5Y-PSZ and 3Y-TZP presented the highest hardness values, while 3Y-TZP was higher than 4Y- and 5Y-PSZ with regard to the IFR. The 5Y-PSZ specimen (0.7 and 1.2 mm) showed the worst mechanical performance (fatigue BFS and cycles until failure), while 3Y-TZP and 4Y-PSZ presented statistically similar values, higher than 5Y-PSZ for both thicknesses (0.7 and 1.2 mm). Moreover, 3Y-TZP showed the highest (1.2 mm group) and the lowest (0.7 mm group) degradation percentage, and 5Y-PSZ had higher strength degradation than 4Y-PSZ group. CONCLUSION. Despite the microstructural differences, 4Y-PSZ and 3Y-TZP had similar fatigue behavior regardless of thickness. 5Y-PSZ had the lowest mechanical performance.

• Journal of the Korean Wood Science and Technology
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• v.30 no.4
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• pp.8-16
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• 2002

This study was performed to produce the high reactive lignin zero substrates from autohydrolyzed wood resources. In chemical compositions of used raw-materials, there were significant differences between two species, Japanese larch (Larix leptolepis) and oak (Quercus mongolica) woods. Japanese larch contained 25 to 3.5 times higher amounts of extractives than oak wood, which is mainly derived from high content of arabinogalactan in Japanese larch wood. Oak wood has 5% lower lignin content and 3% higher holocellulose and pentosans than larch wood. Concerned to changes in wood components during autohydrolysis pretreatment at 22 kg/cm² steaming pressure for 5~60 min, glucose content was constant during pretreatment, while hemicellulose and lignin were abruptly changed. Hemicellulose fraction was decreased significantly and lignin contents increased because of its condensation reaction with hemicellulose degradation products. The pH of hydrolyzates during pretreatment was decreased, reached upto pH 3 and since then leveled off. In the case of oak wood, same tendency was observed as in Japanese larch. Autohydrolysis followed by sodium chlorite and sulfite or bisulfite pretreatment was very effective in delignification of the substrates. In particular, two-stage delignification of autohydrolyzed woods with alkali and O₂-alkali resulted in very low lignin content substrates, such as 0~0.2% lignin substrate.

• Economic and Environmental Geology
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• v.55 no.3
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• pp.281-293
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• 2022

We examined degradation characteristics of lead based pigments(white lead, Red lead, Litharge) according to atmospheric environmet condition, for example atmospheric gas(CO₂, NO₂) and soluble salt. Painted samples not changed material compositions but were occured the color change(𝚫E 4~31) after exposed UV irradiation. All sample were not affected by CO₂ gas not only color but chemical composition. However, samples were remakably changed color exposed NO₂ gas and it was formed secondary product like as lead nitrate. Such as red lead and white lead samples' color difference were 𝚫E 2 and 𝚫 10 respectively and became dark, along with litharge became bright and color difference was 𝚫E 5 after react with NO₂ gas. It confirm that NO₂ was influential factor than CO₂ in the case of same concentration. Furthermore salt spray test was taken to figure out soluble salt influence in fine dust. The result showed noticeable color change and secondary product was formed on samples' surface. The glue film peeled off or hole, and color changed around the secondary products. After salt spray, XRD pattern showed decrease peak intensity and lower crystalinity. As a result of salt spray test, white lead was formed new product litharge and litharge was formed litharge and minium. According to the results, influential atmospheric factors for conservation of paint pigments were UV, NO₂, soluble salt, and litharge was most weakness throughout lead base pigments.

• Journal of Conservation Science
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• v.36 no.6
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• pp.440-455
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• 2020

This study aims to examine the material characteristics of bowls and compare the making techniques of flat cup with cover and jar coffin from the Oryang-dong kiln site, Naju. Bowls, the most frequently excavated small pottery have similar material characteristics, including gray surface, fine-grained texture, and small-sized tempers such as quartz and feldspar, regardless of the excavation slopes. However, the firing temperature of the bowls mostly ranges from 950 to 1,100 ℃. It is estimated that the bowls had formalized making techniques, owing to the similar material composition and firing technique regardless of the excavation slope. The flat cups with cover have similar texture and mineral phases, except their poorly sorted inclusions. However, the jar coffins contain not only fine-grained minerals but also medium-grained quartz, feldspar, and biotite, showing a relatively wide range of firing temperatures. According to the geochemical results of pottery by type, it is assumed that chemical compositions are classified into two groups: small pottery(bowl and falt cup with cover) and jar coffins. In conclusion, small potteries such as bowls and flat cups with cover were made by removing the heavy minerals from raw materials, whereas jar coffins were made by adding medium-grained minerals to raw materials to maintain and support their structures, despite the same source materials. In addition, it is presumed that pottery making proceeded by selecting the source materials, preparing according to their use and controlling the firing temperature and environment.

• Journal of Korea Foundry Society
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• v.41 no.4
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• pp.349-356
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• 2021

Effects of cooling condition after solidification on the microstructure and the mechanical properties of 0.36Mn containing ductile cast iron have been studied based on the minimized addition of Cu and Sn for vehicle component applications with better quality and cost competitiveness. Cu and Sn were selected for additional elements judging from the well-known fact of strong tendency of pearlite promotion followed by the tensile property improvement. After pouring of the Mg treated cast iron melt with various chemical compositions into the block specimens, two ways of post solidification cooling conditions were applied for comparison; both cooling in the mold and cooling in the air after dismantle at 800℃. The pearlite fraction of the mold-cooled specimens was analyzed as 27-44%, with the tensile strength and elongation of 513-568N/mm² and 10.4-14.3%, respectively. Whilest, the air cooled specimens showed the pearlite fraction of 77~85%, with the tensile strength and elongation of 728~758N/mm² and 3.2~6.0%, respectively. It is worthwhile to note that the remarkable improvement of both tensile strength and elongation of the ductile iron was achieved by the present air cooling condition with the minimized combined addition of Cu and Sn to the 0.36Mn containing ductile iron.

• Economic and Environmental Geology
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• v.55 no.5
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• pp.447-463
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• 2022

The lime and clay that used in the construction of the Tomb of King Muryeong and the Royal Tombs in Gongju are auxiliary materials, and are used joint and plaster materials for the wall to play a role of structural support. In this study, the homogeneity between the tombs and material characteristics were interpreted through quantitative analysis of lime and clay. As a result of microtexture and composition analysis, almost the same minerals were identified in each sample groups, and similar characteristics were shown in thermal analysis. Geochemically, it is confirmed that the behavior characteristics are very similar regardless of the tombs. The compositions is also confirmed high homogeneity in the diagrams of CaO-MgO-SiO₂, RO₂-(RO+R₂O) correlations, A-CN-K and A-CNK-FM triangles. Therefore, it is interpreted that the clay used for the construction of the tomb complex was supplied from around area, and the raw materials of lime were produced using shell fragments of oyster family based on mainly composed of calcite. It is interpreted that the raw materials of lime were supplied from middens along the west coast of down the Geumgang river in Korean peninsula, but the consideration of the supply site, needs to be cross-validated through stable isotope analysis, use of carbonate rock and reproduction experiments.