• Resources Recycling
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• v.30 no.2
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• pp.39-45
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• 2021

Spent photovoltaic module is one of the important resource of silver, while related research concerning silver recovery remains limited. In our previous research, HNO3 was utilized to dissolve Ag(I) and Al(III) from the spent silicon solar cells. In order to recover Ag(I) from the leachate of a silicon solar cell, the present study made use of a nitrate solution containing Ag(I) and Al(III), which was subjected to a solvent extraction process with 5,8-diethyl-7-hydroxydodecan-6-oxime (LIX63). Ag(I) was selectively extracted with LIX63 over Al(III) from the nitrate leach solution. Subsequently, quantitative stripping of Ag(I) from the loaded LIX63 was performed by using 20% ammonia water. The McCabe-Thiele plots for the extraction and stripping isotherms of Ag(I) were also constructed. Extraction and stripping simulation tests confirmed an Ag(I) extraction and stripping efficiency of >99.99% and 98.9%, respectively with high purity Ag (99.998%) and Al (99.99%) solution. A process flow sheet for Ag(I) recovery from the nitrate leach solution was proposed.

• The Korea Journal of Herbology
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• v.37 no.3
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• pp.29-39
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• 2022

Objective : This study is aimed to evaluate the protective effects of Rehmanniae Radix, Mori Folium, and Liriopie Tuber mixture (RML) on lung injury of Particulate matter less than 10 um in diameter and diesel exhaust particles (PM10D) mice model. Methods : To investigate the anti-inflammatory activity of RML, PM10D was diluted in aluminum hydroxide (Alum) in 7-week-old male mice and induced by Intra-Nazal-Tracheal (INT) injection method. Animal experiments were divided into 5 groups. Nor (normal mice), CTL (PM10D-induced mice with the administration of distilled water), DEXA (PM10D-induced mice with the administration of 3 mg/kg Dexamethasone), RML 100 (PM10D-induced mice treated with RML 100 mg/kg weight), and RML 200 (PM10D-induced mice treated with RML 200 mg/kg body weight). After 11 days administration, mice were sacrificed and inflammation-related immune cells in broncho-alveolar lavage fluid (BALF) were analyzed. Inflammation-related biomarkers were also analyzed in blood and lungs. Lung tissue was observed through histological examination. Results : In the PM10D induced model, the PML showed decreases in CXCL-1 and IL-17A in BALF. Expression of inflammatory cytokines and cough-related mRNA genes was significantly decreased in serum and lung tissue. The mixture treatment of RML significantly improved the immune related cells in the serum. In addition, histological observations showed a tendency to decrease the severity of lung injury. Conclusions : Overall, these results confirmed the respiratory protective effect of the RML mixture in a model of lung injury induced by air pollution (PM10+DEP), suggesting that it is a potential treatment for respiratory damage.

• Journal of the Korean Society of Radiology
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• v.17 no.1
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• pp.25-30
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• 2023

As 3D printing technology is used in the medical field, interest in metal materials is increasing. The Department of Radiation Oncology uses a shielding block to shield the patient's normal tissue from unnecessary exposure during electron beam therapy. However, problems such as handling of heavy metal materials such as lead and cadmium, reproducibility according to skill level and uncertainty of arrangement have been reported. In this study, candidate materials that can be used for metal 3D printing are selected, and the physical properties and radiation dose of each material are analyzed to develop a customized shielding block that can be used in electron beam therapy. As candidate materials, aluminum alloy (d = 2.68 g/cm³), titanium alloy (d = 4.42 g/cm³), and cobalt chromium alloy (d = 8.3 g/cm³) were selected. The thickness of the 95% shielding rate point was derived using the Monte Carlo Simulation with the irradiation surface and 6, 9, 12, and 16 energies. As a result of the simulation, among the metal 3D printing materials, cobalt chromium alloy (d = 8.3 g/cm³) was similar to the existing shielding block (d = 9.4 g/cm³) in shielding thickness for each energy. In a follow-on study, it is necessary to evaluate the usefulness in clinical practice using customized shielding blocks made by metal 3D printing and to verify experiments through various radiation treatment plan conditions.

• Journal of Conservation Science
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• v.38 no.2
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• pp.124-132
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• 2022

Through scientific analysis, this study identified the material characteristics of metal foil decorating the border line and knotting of the National Folklore Cultural Heritage 'Pouch for the Sutra Embroidered with a Sun and Moon Design'. Through Scanning Electron Microscope-Energy Dispersive Spectroscopy results, it was estimated that silver (Ag) and sulfur (S) were present in the metal foil, and silver leaf was also attached to the medium. S may discolor Ag from yellow to black depending on its concsentration and contact time. Yellow color could not be identified in metal foil at present. But there existed an example of the preparation of a gold-colored flat silver thread; therefore, further research is needed to estimate the original color. The lamella was reddish brown on the back. Aluminum, silicon, and iron were also detected and were the main components found in red soil. This is believed to be the red adhesive in traditional flat gold thread and is considered to be an adhesive-related component of the metal foil. From the gas chromatography mass spectrometry results, the adhesive component was confirmed to be animal glue.

• Composites Research
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• v.35 no.5
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• pp.347-358
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• 2022

Carbon fiber is an excellent structural material, which has been proven in many industries, and the shipbuilding industry is no exception. In particular, in advanced maritime countries, special ships of the Navy and Coast Guard with carbon fiber composite hulls have already been deployed. In Korea, carbon fiber composite materials have been applied to a 10-ton class leisure craft or a 30-ton class patrol, but no research has been done on a hundred of tons or more vessels. In this study, the feasibility study of a 500-ton patrol vessel with a carbon fiber composite hull was conducted through an analysis of similar cases abroad. As a result, it was recognized that the developed hull can be reduced in weight by about 21% to 25% compared to the existing aluminum or FRP hull. It was also confirmed that this light-weight effect can induce the improvement of the maximum speed and the improvement of the operating range via simulations.

• Journal of Practical Engineering Education
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• v.14 no.1
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• pp.119-125
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• 2022

Materials used for education are materials such as SM20C, Al6061, and acrylic. SM20C materials are carbon steel and are often used in certification tests and functional competitions, but are also widely used in industrial sites. The Al6061 material is said to be a material that has lower hardness and stronger flexibility than carbon steel, so it is a material that generates a lot of compositional selection of tools. If students are taught practical training using acrylic materials, vibration occurs due to excessive cutting in some parts and damage to the tool occurs. In this process, we examine to what extent the impact on the 2NC head, which is a five-axis equipment, can affect precision control. The weakest part of the five-axis equipment can be said to be the weakest part of the head that controls the AC axis. When the accuracy and cumulative tolerance of this part occur, the accuracy of all products decreases. Therefore, the core part of the 2NC head, the spindle housing, was carried out using an Al7075 T6 (Alcoa, USA) material. In the process of vibration and cutting applied to this material, the analysis was conducted to find out the value applied to the finite element analysis under extreme conditions. It is hoped that this analysis data will help students see and understand the structure of 5-axis machining rather than 5-axis cutting.

• Clean Technology
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• v.28 no.2
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• pp.154-162
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• 2022

Microstructured Al@Al₂O₃ and Al@Ni-Al LDH (LDH = layered double hydroxide) core-shell metal-ceramic composites are prepared by hydrothermal reactions of aluminum (Al) metal substrates. Controlled hydrothermal reactions of Al metal substrates induce the hydrothermal dissolution of Al ions at the Al-substrate/solution interface and reconstruction as porous metal-hydroxides on the Al substrate, thereby constructing unique metal-ceramic core-shell composite structures. The morphology, composition, and crystal structure of the core-shell composites are affected largely by the ions in the hydrothermal solution; therefore, the critical physicochemical and surface properties of these unique metal-ceramic core-shell microstructures can be modulated effectively by varying the solution composition. A Ni/Al@Al₂O₃ catalyst with highly dispersed catalytic Ni nanoparticles on an Al@Al₂O₃ core-shell substrate was prepared by a controlled reduction of an Al@Ni-Al LDH core-shell prepared by hydrothermal reactions of Al in nickel nitrate solution. The reduction of Al@Ni-Al LDH leads to the exolution of Ni ions from the LDH shell, thereby constructing the Ni nanoparticles dispersed on the Al@Al₂O₃. The catalytic properties of the Ni/Al@Al₂O₃ catalyst were investigated for CO₂ methanation reactions. The Ni/Al@Al₂O₃ catalyst exhibited 2 times greater CO₂ conversion than a Ni/Al₂O₃ catalyst prepared by conventional incipient wetness impregnation and showed high structural stability. These results demonstrate the high effectiveness of the design and synthesis methods for the metal-ceramic composite catalysts derived by hydrothermal reactions of Al metal substrates.

• Economic and Environmental Geology
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• v.56 no.4
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• pp.475-499
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• 2023

To infer the provenance of raw iron materials utilized in iron production at the archaeological sites in Gyeongsang province, petrographic and geochemical analyses were conducted for smelting samples and major iron ores sourced from ore deposits. The smelting samples excavated from various iron archaeological sites were classified into different types according to their refining processes, such as iron bloom, iron bloom slag, pig iron, pig iron slag, forging iron flake, smithery iron, iron flake, and arrowhead. These samples exhibited discernable differences in their mineralogical components and texture. The enrichments of major elements such as aluminum and calcium in silicate minerals of the residual slags and the high contents of trace elements such as nickel and copper in some iron-making relics reflect the characteristics of raw iron ores, and thus can be regarded as potential indicators for inferring the provenance of source materials. In particular, the compositional ranges of Pb-Sr isotope ratios for the iron smelting samples were classified into three categories: 1) those exhibiting similar ratios to those of the raw iron ores, 2) those enriched in strontium isotope ratio, and 3) those enriched in both lead and strontium isotope ratios. The observed distinct Pb-Sr isotope characteristics in the iron smelting samples suggest the potential contribution of specific additives being introduced during the high-temperature refining process. These results provide a new perspective on the interpretation of the provenance study of the iron archaeological samples in Gyeongsang province, particularly in terms of the potential contribution of additives on the refining process.

• Composites Research
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• v.36 no.3
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• pp.199-204
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• 2023

A combination of a metallic mesh and an adhesive layer of metallic particle/epoxy composite was introduced as an intermediate layer to enhance the adhesion between cold-sprayed particles and fiber-reinforced composites (FRCs). Aluminum was considered for both the metallic particles in the adhesive and the metallic mesh. To predict the mechanical characteristics of the intermediate bond layer under a high strain rate, the properties of the adhesive layer needed to be calculated or measured. Therefore, in this study, the Al particle/epoxy adhesive was homogenized by using a rule of mixture. To verify the homogenization, the penetration depth, and the thickness decrease after the cold spray deposition from the undeformed surface, was monitored with FE analysis and compared with experimental observation. The comparison displayed that the penetration depth was comparable to the diameters of one cold spray particle, and thus the homogenization approach can be reasonable for the prediction of the stress level of particulate polymer composite interlayer under a high strain rate for cold spray processing.

• Analytical Science and Technology
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• v.21 no.6
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• pp.543-552
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• 2008

This paper described the relatively sensitive and simultaneous analytical method for 3-monochloropropane-1,2-diol (3-MCDP, $C_3H_7ClO_2$, MW. 110) as well as 1,3-dichloropropan-2-ol (1,3-DCP, $C_3H_6Cl_2O$, MW. 128) in various foods. Food samples were homogenized in 5M NaCl solution, mixed with aluminum oxide and eluted with dichloromethane. The extracted chloropropanols were concentrated by rotary evaporator and $N_2$ blow serially were derivatized with HFBA (Heptafluorobutyric anhydride, $C_8F_{14}O_3$, MW. 410) and were determined by GC/MS using isotope dilution method. The characteristic molecular ions at m/z 253, 275, 289, 291, and 453 for HFBA derivatives of 3-MCPD (MW. 502) and 110, 275, and 277 for HFBA derivatives of 1,3-DCP (MW. 325) were chosen in selected ion mode. The method validation data showed sufficiently good properties of LOD (0.003 mg/kg), LOQ (0.010 mg/kg), linearity ($R^2{\geq}0.999$ at 0.010~1.000 mg/kg), and recovery rate (${\approx}97%$). The levels of chloropropanols in soy sauce, sauces, processed meat products, fishery products, and seasonings (n=56/157) determined by the presented method were 0.0~0.3 mg/kg.