• Journal of Conservation Science
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• v.37 no.6
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• pp.648-658
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• 2021

In this study, we aimed to analyze the chemical changes that occur in Korean paper in an accelerated deterioration environment of 105℃. We selected the Korean paper produced with different types of cooking agents (plant lye, Na₂CO₃) and during different manufacturing seasons (winter, summer). The degree of deterioration of the Korean paper was confirmed by measuring the brightness, yellowness, and pH level, and the degree of change in each vibrational region of cellulose as deterioration progressed through infrared (FT-IR) spectroscopy. The FT-IR analysis showed that, as deterioration progressed, the absorbance of the amorphous region in cellulose decreased, whereas the absorbance of the crystalline region slightly increased. X-Ray diffraction (XRD) analysis and Raman spectroscopy were performed to verify the changes in the crystalline and amorphous regions in cellulose indicated by the FT-IR results. Furthermore, the crystallinity index (CI) was calculated; it showed a slight increase after deterioration; therefore, CI was confirmed to follow the same trend as that observed for absorbance in the FT-IR results. In addition, as a result of Raman spectroscopic analysis, the degree of decomposition of the amorphous region in the cellulose under the manufacturing conditions was confirmed by the fluorescence measured after the deterioration.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.4
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• pp.121-127
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• 2022

β-Gallium oxide (Ga₂O₃), an ultra-wide bandgap semiconductor, has attracted great attention due to its promising applications for high voltage power devices. The most stable phase among five different polytypes, β-Ga₂O₃ has the wider bandgap of 4.9 eV and higher breakdown electric field of 8 MV/cm. Furthermore, it can be grown from melt source, implying higher growth rate and lower fabrication cost than other wide bandgap semiconductors such as SiC, GaN and diamond for the power device applications. In this study, β-Ga₂O₃ bulk crystals were grown by the edge-defined film-fed growth (EFG) process. The growth direction and the principal surface were set to be the [010] direction and the (100) plane of the β-Ga₂O₃ crystal, respectively. The spectra measured by Raman an alysis could exhibit the crystal phase an d impurity dopin g in the β-Ga₂O₃ ingot, and the crystallinity quality and crystal direction were analyzed using high-resolution X-ray diffraction (HRXRD). The crystal quality and various properties of as-grown β-Ga₂O₃ ribbon was systematically analyzed in order to investigate the spatial variation in entire crystal grown by EFG method.

• Journal of the Korean GEO-environmental Society
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• v.24 no.3
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• pp.23-27
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• 2023

Graphitic carbon nitride (g-C₃N₄) has been used as effective photocatalyst for degradation of antibiotics under visible light irradiation. However, the fast recombination of hole-electron pair may limit their photocatalytic efficiency. In our study, Ag was grafted on g-C₃N₄/g-C₃N₄ isotype heterojunction by a microwave-assisted decomposition method. The structure and physical properties of heterojunction photocatalyst were characterized through X-ray diffraction, UV-DRS, FT-IR, and Photoluminescence analyses. Ag decorated g-C₃N₄/g-C₃N₄ isotype heterojunction exhibited excellent photocatalytic activity for degradation of sulfamethoxazole under irradiation under visible light irradiation within 210 min, which is higher than g-C₃N₄/g-C₃N₄ isotype heterojunction and bulk g-C₃N₄. The addition of Ag may broaden the visible light absorption and restrict the recombination of hole-electron pair because of the surface plasmons resonance, resulting in the improving the photocatalytic activity.

• Journal of Applied Biological Chemistry
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• v.65 no.4
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• pp.457-462
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• 2022

Manganese (Mn) exists in various oxidation states and Mn(II) is the most mobile species of Mn, which is toxic to plants and limits their growth. Therefore, the purpose of this study was to reduce Mn toxicity by immobilizing Mn using various adsorbents including iron oxides and calcium compounds. Ferrihydrite, schwertmannite, goethite were synthesized, which was confirmed by X-ray diffraction. Hematite was purchased and used as Mn adsorbent. Calcium compounds such as CaNO₃, CaSO₄, and CaCO₃ were used to increase pH and oxidize Mn. For Mn adsorption, Mn(II) solution was reacted with four iron oxides, CaNO₃, CaSO₄, and CaCO₃ for 24 hours, filtered, and the remaining Mn concentrations in the solution were analyzed by inductively coupled plasma optical emission spectroscopy. The adsorption rate and adsorption isotherm were calculated. Among iron oxides, the adsorption rate was highest for hematite followed by ferrihyrite, but goethite and schwertmannite did not adsorb Mn. In the case of calcium compounds, the adsorption rate was high in the order of CaCO₃>CaNO₃>CaSO₄. In conclusion, treatment of CaCO₃ was the most effective in reducing Mn toxicity by increasing pH.

• Journal of Powder Materials
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• v.30 no.4
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• pp.324-331
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• 2023

Lithium (Li) is a key resource driving the rapid growth of the electric vehicle industry globally, with demand and prices continually on the rise. To address the limited reserves of major lithium sources such as rock and brine, research is underway on seawater Li extraction using electrodialysis and Li-ion selective membranes. Lithium lanthanum titanate (LLTO), an oxide solid electrolyte for all-solid-state batteries, is a promising Li-ion selective membrane. An important factor in enhancing its performance is employing the powder synthesis process. In this study, the LLTO powder is prepared using two synthesis methods: sol-gel reaction (SGR) and solid-state reaction (SSR). Additionally, the powder size and uniformity are compared, which are indices related to membrane performance. X-ray diffraction and scanning electron microscopy are employed for determining characterization, with crystallite size analysis through the full width at half maximum parameter for the powders prepared using the two synthetic methods. The findings reveal that the powder SGR-synthesized powder exhibits smaller and more uniform characteristics (0.68 times smaller crystal size) than its SSR counterpart. This discovery lays the groundwork for optimizing the powder manufacturing process of LLTO membranes, making them more suitable for various applications, including manufacturing high-performance membranes or mass production of membranes.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.174-174
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• 2000

A strong antiferromagnetic coupling in Fe/Si multilayered films (MLF) had been recently discovered and much consideration has been given to whether the coupling in the Fe/Si MLF system has the same origin as the metal/metal MLF. Nevertheless, the nature of the interfacial ron silicide is still controversial. On one hand, a metal/ semiconductor structure was suggested with a narrow band-gap semiconducting $\varepsilon$-FeSi spacer that mediates the coupling. However, some features show that the nature of coupling can be well understood in terms of the conventional metal/metal multilayered system. It is well known that both magneto-optical (MO) and optical properties of a metal depend strongly on their electronic structure that is also correlated with the atomic and chemical ordering. In this study, the nature of the interfacial regions is the Fe/Si multilayers has been investigated by the experimental and computer-simulated MO and optical spectroscopies. The Fe/Si MLF were prepared by rf-sputtering onto glass substrates at room temperature with the number of repetition N=50. The thickness of Fe sublayer was fixed at 3.0nm while the Si sublayer thickness was varied from 1.0 to 2.0 nm. The topmost layer of all the Fe/Si MLF is Fe. In order to carry out the computer simulations, the information on the MO and optical parameters of the materials that may constitute a real multilayered structure should be known in advance. For this purpose, we also prepared Fe, Si, FeSi2 and FeSi samples. The structural characterization of Fe/Si MLF was performed by low- and high -angle x-ray diffraction with a Cu-K$\alpha$ radiation and by transmission electron microscopy. A bulk $\varepsilon$-FeSi was also investigated. The MO and optical properties were measured at room temperature in the 1.0-4.7 eV energy range. The theoretical simulations of MO and optical properties for the Fe/Si MLF were performed by solving exactly a multireflection problem using the scattering matrix approach assuming various stoichiometries of a nonmagnetic spacer separating the antiferromagnetically coupled Fe layers. The simulated spectra of a model structure of FeSi2 or $\varepsilon$-FeSi as the spacer turned out to fail in explaining the experimental spectra of the Fe/Si MLF in both intensity and shape. Thus, the decisive disagreement between experimental and simulated MO and optical properties ruled out the hypothesis of FeSi2 and $\varepsilon$-FeSi as the nonmagnetic spacer. By supposing the spontaneous formation of a metallic ζ-FeSi, a reasonable agreement between experimental and simulated MO and optical spectra was obtained.

• Journal of the Korea Institute of Building Construction
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• v.23 no.3
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• pp.231-240
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• 2023

In this research, our goal was to explore the potential use of cement mortar augmented with liquid red mud. To facilitate this, we neutralized liquid red mud(LR) - exhibiting a pH of 10-12 - using sulfuric acid to yield sulfuric acid neutralized red mud(SR). We then evaluated the flow, setting time, and compressive strength of the cement mortar combined with liquid red mud, while also performing a thorough examination of its chemical properties through X-ray diffraction(XRD) and scanning electron microscopy(SEM). The flow tests indicated a decrease in flow values for both MS-LR and MS-SR in comparison to the Plain. Analogously, the setting time for MS-LR and MS-SR was found to be abbreviated when juxtaposed with the Plain. With regards to compressive strength, MS-LR demonstrated a surge in strength at the 1-day mark, while MS-SR displayed a diminution at the 1-day and 3-day timepoints compared to the Plain. XRD analysis illustrated that after 28 days, the XRD patterns of Plain and MS-SR bore significant resemblance, though a new peak was detected in MS-LR. SEM imagery highlighted that the microstructures of Plain and MS-SR were alike, but MS-LR manifested a distinct microstructure, characterized by a finely fibrous formation. Based on these observations, we infer that the replacement of cement mortar with liquid red mud neutralized with sulfuric acid contributes to a noticeable enhancement in strength, thereby verifying its suitability for this application.

• Journal of the Korean Geotechnical Society
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• v.25 no.6
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• pp.17-29
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• 2009

There has been an increase in the investigation of deep sea sediments with a consequent increase in the amount of energy required to undertake these investigations. The geotechnical characteristics of Ulleung Basin sediment are explored by using depressurized specimens following methane production tests carried out on pressured core samples obtained at 2,100 m water depth and 110 m below sea floor. Geotechnical index tests, X-ray diffraction, and scanning electron microscope are conducted to identify the geotechnical index parameters, clay mineralogy, chemical composition, and microstructure of the sediments. Compressibility, and elastic and electromagnetic wave parameters are investigated for two samples by using a multi sensing instrumented oedometer cell. The strength chatracteristics are obtained by the direct shear tests. The dominant clay minerals are mostly kaolinite, illite, chlorite, and calcite. The SEM shows a well-developed flocculated structure of the microfossil. Void ratio, electrical resistivity, real permittivity, conductivity, and shear wave velocity show bi-linear behavior with the effective vertical stress: as the vertical effective stress increases. The friction angle obtained by the direct shear test is about $21^{\circ}$, which is similar to the value observed in the Ulleung Basin sediments. This study shows that the understanding of the behavior acting on the diatomaceous marine sediment is important because it often maintains the useful energy resources such as gas hydrate and so will be the new engineering field in the next generation.

• Journal of the Korean Society of Radiology
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• v.15 no.5
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• pp.697-704
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• 2021

It is hard to get Filaments which are materials of the 3D printing Fused Deposition Modeling(FDM) method as radiation shielding in Korea. and also related research is insufficient. This study aims to provide basic data for the development of radiation shields using 3D printing by evaluating the physical properties and radiation shielding capabilities of filaments containing metal particles. after selecting five metal filaments containing metal particle reinforcement materials, the radiation shielding rate was calculated according to the Korean Industrial Standard's protective equipment test method to evaluate physical properties such as tensile strength, density, X-ray Diffraction(XRD), and weight measurement using ASTM's evaluation method. In the tensile strength evaluation, PLA + SS was the highest, ABS + W was the lowest, and ABS + W is 3.13 g/cm³ which value was the highest among the composite filaments in the density evaluation. As a result of the XRD, it may be confirmed that the XRD peak pattern of the particles on the surface of the specimen coincides with the pattern of each particle reinforcing material powder metal, and thus it was confirmed that the printed specimen contained powder metal. The shielding effect for each 3D printed composite filament was found to have a high shielding rate in proportion to the effective atomic number and density in the order of ABS + W, ABS + Bi, PLA+SS, PLA + Cu, and PLA + Al. In this study, it was confirmed that the metal particle composite filament containing metal powder as a reinforcing material has radiation shielding ability, and the possibility of using a radiation shielding filament in the future.

• Journal of the Korean Society for Heat Treatment
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• v.36 no.4
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• pp.198-205
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• 2023

We investigated the effects of Al and Mg on the microstructure and hardness of the coating layer of galvanized steel sheets, by thermodynamic calculations, X-ray diffraction, scanning electron microscopy, and Vickers hardness tests of Zn-0.2Al, Zn-6Al-2Mg, and Zn-10Al-5Mg coating layers. Regardless of the alloy composition of the galvanizing bath, a Fe-Al layer was observed between the coating layer and steel sheet. The Zn-0.2Al coating layer consists of major h.c.p. Zn phase and minor f.c.c. Al phase. The fraction of f.c.c. Al phase (containing a significant amount of Zn) of the coating layer increases with increasing the chemical composition of Al of the galvanizing bath. The h.c.p. MgZn₂ phase was formed in the Al/Mg-containing Zn-6Al-2Mg and Zn-10Al-5Mg coating layers, forming Zn-Al-MgZn₂ eutectic microstructure. The primary MgZn₂ phase was additionally formed in the Zn-10Al-5Mg coating layers containing high concentrations of Al and Mg. The Vickers hardness values of Zn-0.2Al, Zn-6Al-2Mg, and Zn-10Al-5Mg coating layers were 59.1 ± 1.2 HV, 161.2 ± 5.7 HV, and 215.5 ± 40.3 HV, respectively. The addition of Al and Mg increased the hardness of the coating layer by increasing the fraction of the Al phase (containing Zn) and MgZn₂ intermetallic compound, which were harder than the Zn phase.