• Journal of the Korean GEO-environmental Society
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• v.11 no.7
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• pp.25-31
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• 2010

In this study, it was intended to suggest new cooling method that enables to improve the applicability and added value higher than existing slag by applying new cooling method(powder cooling slag) at the time discharging slag, which is produced from the ash melting system that the plasma torch is used for the first time in Korea. It is suggested the applicative direction in the development of future recycling process by discovering its nature of material and applicative possibility as earthwork material. The ashes produced after the sewage sludge discharged from Y city was incinerated by the fluidized bed method and was used as test materials. As result of XRF(X-Ray Flourescence Spectrometry) analysis, main ingredient of sewage sludge ashes was $SiO_2$(32%) besides CaO, $Al_2O_3$, $Fe_2O_3$, and so on. In addition, as result of XRD analysis, traditional diffuse pattern of glass could be found from granulated air-cooled slags, while a minor crystal phase could be observed from powder cooling slag, because the powder on the surface exists in the state not melted. From EDX(Energy Dispersive X-ray Spectroscopy) analysis, it is deemed that powder ingredient has no change before and after it is used as cooling medium, and accordingly it is thought that the powder can be produced as the material where the function is added if used in different shape.

• Journal of the Korean GEO-environmental Society
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• v.17 no.2
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• pp.5-11
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• 2016

$MWCNT-TiO_2$ nano composites and $Ag-MWCNT-TiO_2$ nano composites were prepared from Multi-Walled Carbon NanoTube (MWCNT), titanium (IV) butoxide (TNB) solution and silver nitrate ($AgNO_3$) by the sol-gel method. The dispersion and structure of Ag in the synthesized composites was observed by Scanning Electron Microscopy (SEM) and Field Emission Transmission Electron Microscopy (FE-TEM). X-Ray Diffraction (XRD) patterns of the composites showed that the composites contained an anatase phase. The Energy Dispersive X-ray spectroscopy (EDX) showed the presence of C, O, Ti and Ag peaks. The $TiO_2$ particles were distributed uniformly in the MWCNT network, and Ag particles were virtually fixed on the surface of the tubes. Also decomposition of the methylene blue was investigated according to UV radiation times for study photocatalytic activity. $Ag-MWCNT-TiO_2$ nano composites show high photodegradation than $MWCNT-TiO_2$ nano composites. The results indicate that the high conductivity of Ag improved the photoactivity of the $MWCNT-TiO_2$ composite.

• Tribology and Lubricants
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• v.34 no.3
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• pp.84-92
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• 2018

Bearings are essential for reducing vibration and wear, in order to achieve high durability and increase longevity. White metal treatment of tilting pads via centrifugal casting method has the possibility of increasing durability. However, this manufacturing method has drawbacks such as long processing time, high defect rate, and harmful health effects. Laser cladding deposition technique is a powerful method that can address these issues by decreasing the processing time and providing good adhesion. In this study, we suggest optimum conditions for laser cladding deposition that can be used in industrial applications. We deposited a soft white metal layer on SCM440 that is primarily used in shafts to minimize wear of bearing pads. During the laser deposition process, we controlled factors such as laser power, powder feed rate, and laser head speed to determine the optimum conditions. In addition, we measured the hardness using micro Vickers, and performed field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and friction tests to investigate the mechanical properties and surface characteristics for different parameters. Based on the experimental results, we suggest that laser power, powder feed rate, and laser head speed of 1.3 kW, 2.5 rpm, and 10 mm/s, respectively, constitute the optimum conditions for producing white metals using laser cladding.

• Applied Chemistry for Engineering
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• v.17 no.6
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• pp.575-579
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• 2006

Solid electrolyte interface is formed on a carbon electrode used as an anode in Li-ion battery, which can be of $Li^{+}$ intercalation/deintercalation during the first cycle. The passivation film formed by a solvent decomposition during the initial charge process affects cell performance and it was one of the main reason of an initial irreversible capacity. This paper describes the use, for the first time, of $Li_2CO_3$ as the additive for the formation of a passivation film on the carbon surface to suppress the initial irreversible reaction. Chronopotentiometry, cyclic voltammetry, and impedance spectroscopy were used to investigate the effects of the $Li_{2}CO_{3}$ additive. Scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction were also used to monitor changes in the surface morphology and composition of the passivation film formed by solvent decomposition and the precipitation of $Li_{2}CO_{3}$. The addition of $Li_{2}CO_{3}$ to a solution of 1 M $LiPF_{6}$/EC:MA (1:3, v/v) resulted in a decrease in the initial irreversible capacity and it was due to the suppression of the solvent decomposition on the electrode surface.

• Clean Technology
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• v.27 no.4
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• pp.291-296
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• 2021

Recently, there has been increasing demand for advancing photocatalytic techniques that are capable of the efficient removal of organic pollutants in water. TiO₂, a representative photocatalytic material, has been commonly used as an effective photocatalyst, but it is rather expensive and an alternative is required that will fulfill the requirements of both high performing photocatalytic activities and cost-effectiveness. In this work, ZnO, which is more cost effective than TiO₂, was synthesized by using a microreactor-assisted nanomaterials (MAN) process. The process enabled a continuous production of ZnO nanoparticles (NPs) with a flower-like structure with high uniformity. In order to resolve the limited light absorption of ZnO arising from its large band gap, Ag NPs were uniformly decorated on the flower-like ZnO surface by using the MAN process. The plasmonic effect of Ag NPs led to a broadening of the absorption range toward visible wavelengths. Ag NPs also helped inhibit the electron-hole recombination by drawing electrons generated from the light absorption of the flower-like ZnO NPs. As a result, the Ag-ZnO nanocomposites showed improved photocatalytic activities compared with the flower-like ZnO NPs. The photocatalytic activities were evaluated through the degradation of methylene blue (MB) solution. Scanning electron microscopy (SEM), x-ray diffraction (XRD), and energy-dispersive x-ray spectroscopy (EDS) confirmed the successful synthesis of Ag-ZnO nanocomposites with high uniformity. Ag-ZnO nanocomposites synthesized via the MAN process offer the potential for cost-effective and scalable production of next-generation photocatalytic materials.

• Korean Journal of Heritage: History & Science
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• v.40
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• pp.413-430
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• 2007

This study analyzed the foreign substances in waterlogged archaeological woods and compounds in soil where waterlogged archaeological wood was buried, in order to examine the relationship between burial environment and foreign substances in waterlogged archaeological wood. The XRF(X-ray Fluorescence Spectroscopy) and EDX(Energy Dispersive X-ray) analysis were conducted to examine the effect of iron(Fe) to blacken the waterlogged wood. The XRF results showed that investigated soil contained Si, Al, and Fe. Wood ash contained more sulfur and Fe than any other elements in the EDX analysis. Cellulose and hemicellulose were significantly reduced at the surface of wood, which is the blackened part of waterlogged wood. Foreign substances changed the surface color. These problems could be solved by removal of foreign substances in waterlogged archaeological wood using EDTA(Ethylene Diamine Tetra Acetic acid). The optimum condition to remove Fe from waterlogged wood by EDTA was investigated. To do this, the concentration of Fe removed was measured with various concentration of EDTA-2Na. The optimum pH of EDTA-2Na was figured to be 4.1 to 4.3. As the concentration of EDTA increased, the extracted concentration of Fe also increased. In the case of 0.4 wt% of EDTA-2Na, about 60ppm of Fe was eliminated and was stabilized after 48 hours. In the case of EDTA-3Na, the optimum pH was 7 to 8, and about 10 ppm of Fe was eliminated at 0.4 wt% of EDTA-3Na. In the case of EDTA-4Na, the optimum pH was 10 to 11, and about 20 ppm of Fe was eliminated at 0.4 wt% of EDTA-4Na. In conclusion, the iron(Fe) in waterlogged archaeological wood was removed by EDTA treatment and it increased the whiteness of the surface.

• 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 Recycled Construction Resources Institute
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• v.11 no.1
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• pp.89-96
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• 2023

In this paper, a ferrosilicon by-product was evaluated to confirm the feasibility of recycling it as supplementary cementitious material of ordinary Portland cement in concrete. Three different levels of replacement ratio (10 %, 20 % and 30 % of total binder) were applied to find which is the most beneficial to be used as a binder. Ferrosilicon concrete was initially assessed at setting time and compressive strength. Durability was evaluated by the resistance to chloride penetration test(RCPT) and alkali-silica reaction(ASR) with a comparison to silica fume concrete due to their similarity in chemical composition. The porosimetry and X-ray diffraction analysis along with energy dispersive X-ray spectroscopy give information on the microstructural characteristics of the ferrosilicon concrete. It was found that 10 % ferrosilicon concrete has higher strength while 20 %, 30 % have lower strength than OPC concrete. However, chemical resistance to chloride attack is higher when replacement is increased. Compared to silica fume, the durability of ferrosilicon might be less efficient however, it is obviously beneficial than OPC. High SiO₂ content in ferrosilicon results in producing more C-S-H gel which could make denser pore structure. Most of the risk of alkali silica reaction to silicate binders through length change tests was less than 0.2 %, and both mortar using ferrosilicon and silica fume showed better resistance to alkali silica reaction as the substitution rate increased.Reuse of industrial waste rather than producing highly refined additives might reduce environmental load during manufacture and save costs.

• Korean Journal of Dental Materials
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• v.45 no.4
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• pp.257-274
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• 2018

The purpose of this study was to evaluate the effect of acid-treatment conditions on the surface properties of the RBM (Resorbable Blast Media) treated titanium. Disk typed cp-titanium specimens were prepared and RBM treatments was performed with calcium phosphate ceramic powder. Acid solution was mixed using HCl, $H_2SO_4$ and deionized water with 4 different volume fraction. The RBM treated titanium was acid treated with different acid solutions at 3 different temperatures and for 3 different periods. After acid-treatments, samples were cleaned with 1 % Solujet solution for 30 min and deionized water for 30 min using ultrasonic cleanser, then dried in the electrical oven ($37^{\circ}C$). Weight of samples before and after acid-treatment were measured using electric balance. Surface roughness was estimated using a confocal laser scanning microscopy, crystal phase in the surface of sample was analyzed using X-ray diffractometer. Surface morphology and components were evaluated using Scanning Electron Microscope (SEM) with Energy Dispersive X-ray spectroscopy (EDX) and X-ray Photoemission Spectroscopy (XPS). Values of the weight changes and surface roughness were statistically analyzed using Tukey-multiple comparison test (p=0.05). Weight change after acid treatments were significantly increased with increasing the concentration of $H_2SO_4$ and temperature of acid-solution. Acid-treatment conditions (concentration of $H_2SO_4$, temperature and time) did not produce consistent effects on the surface roughness, it showed the scattered results. From XRD analysis, formation of titanium hydrides in the titanium surface were observed in all specimens treated with acid-solutions. From XPS analysis, thin titanium oxide layer in the acid-treated specimens could be evaluated. Acid solution with $90^{\circ}C$ showed the strong effect on the titanium surface, it should be treated with caution to avoid the over-etching process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.145-145
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• 2008

High-k materials have been paid much more attention for their characteristics with high permittivity to reduce the leakage current through the scaled gate oxide. Among the high-k materials, $ZrO_2$ is one of the most attractive ones combing such favorable properties as a high dielectric constant (k= 20 ~ 25), wide band gap (5 ~ 7 eV) as well as a close thermal expansion coefficient with Si that results in good thermal stability of the $ZrO_2$/Si structure. During the etching process, plasma etching has been widely used to define fine-line patterns, selectively remove materials over topography, planarize surfaces, and trip photoresist. About the high-k materials etching, the relation between the etch characteristics of high-k dielectric materials and plasma properties is required to be studied more to match standard processing procedure with low damaged removal process. Among several etching techniques, we chose the inductively coupled plasma (ICP) for high-density plasma, easy control of ion energy and flux, low ownership and simple structure. And the $BCl_3$ was included in the gas due to the effective extraction of oxygen in the form of $BCl_xO_y$ compounds. During the etching process, the wafer surface temperature is an important parameter, until now, there is less study on temperature parameter. In this study, the etch mechanism of $ZrO_2$ thin film was investigated in function of $Cl_2$ addition to $BCl_3$/Ar gas mixture ratio, RF power and DC-bias power based on substrate temperature increased from $10^{\circ}C$ to $80^{\circ}C$. The variations of relative volume densities for the particles were measured with optical emission spectroscopy (OES). The surface imagination was measured by scanning emission spectroscope (SEM). The chemical state of film was investigated using energy dispersive X-ray (EDX).