• Journal of Environmental Science International
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• v.15 no.4
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• pp.333-340
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• 2006

A (5 wt.%)Mn-(1 wt.%)$V_{2}O_{5}/TiO_{2}$ catalyst were prepared by co-precipitation method and used for low-temperature selective catalytic reduction (SCR) of $NO_x$ with ammonia in the presence of oxygen. The properties of the catalysts were studied by X-ray diffraction (XRD), temperature programmed reduction (TPR) and scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS). The experimental results showed that (5 wt.%)Mn-(1 wt.%)$V_{2}O_{5}/TiO_{2}$ catalyst yielded 81% NO conversion at temperature as low as $150^{\circ}C$ and a space velocity of $2,400\;h^{-1}$. Crystalline phase of $Mn_{2}O_3$ was present at ${\ge}\;15%$ Mn on $V_{2}O_{5}/TiO_{2}$. XRD confirmed the presence of manganese oxide ($Mn_{2}O_{3}$) at $2{\theta}=32.978^{\circ}(222)$. The XRD patterns presented of (5 wt.%)Mn-(1 wt.%)$V_{2}O_{5}/TiO_{2}$ did not show intense or sharp peaks for manganese oxides and vanadia oxides. The TPR profiles of (5 wt.%)Mn-(1 wt.%)$V_{2}O_{5}/TiO_{2}$ catalyst showed main reduction peat of a maximum at $595^{\circ}C$.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.1
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• pp.1-10
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• 2020

This study deals with the fabrication and thermal characterization of planar heating elements attached to the backside of the reflector used in the electrodeless lamp of a freezer. We tried to solve the problem of the local heat generation of the linear heating element that occurs about 50℃. The homogeneous dispersion and manufacturing excellence of the planar heating element produced were confirmed through SEM and EDS. In addition, the test specimens was prepared according to the change in the ratio of carbon fiber to the basis weight of the planar heating element, and a sample having a basis weight of 50g/㎡ having a content ratio of carbon fiber of 70% was selected. That sample showed low surface resistance of 4.3Ω/sq and high temperature of about 81℃ at 6V. Durability was confirmed by performing repeated bending evaluation of 3000 cycles for the sample. Large area test specimens were prepared to be applied to the actual reflector, insulated by EVA film and analyzed for their thermal characteristics. From 13V application, the temperature of the linear heating element was higher than 50℃ and the average temperature of 68℃ was maximum at 18V.

• Journal of Electrochemical Science and Technology
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• v.6 no.2
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• pp.65-74
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• 2015

This work examines the characterization and corrosion behaviour of laser alloyed UNSG10150 steel with three different premixed composition Zn-Sn binary powders using a 4.4 kW continuous wave (CW) Rofin Sinar Nd:YAG laser processing system. The steel alloyed samples were cut to corrosion coupons, immersed in sulphuric acid (0.5 M H₂SO₄) solution at 30℃ using electrochemical technique and investigated for its corrosion behaviour. The morphologies and microstructures of the developed coated and uncoated samples were characterized by Optic Nikon Optical microscope (OPM) and scanning electron microscope (SEM/EDS). Moreover, X-ray diffractometer (XRD) was used to identify the phases present. An enhancement of 2.7-times the hardness of the steel substrate was achieved in sample A₁ which may be attributed to the fine microstructure, dislocations and the high degree of saturation of solid solution brought by the high scanning speed. At scanning speed of 0.8 m/min, sample A₁ exhibited the highest polarization resistance R_p (1081678 Ωcm² ), lowest corrosion current density i_corr (4.81×10⁻⁸A/cm² ), and lowest corrosion rate Cr (0.0005 mm/year) in 0.5 M H₂SO₄. The polarization resistance R_p (1081678 Ωcm² ) is 67,813-times the polarization of the UNSG10150 substrate and 99.9972% reduction in the corrosion rate.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.2
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• pp.81-88
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• 2010

Hydrogen energy applications have recognized clean materials and high energy carrier. Accordingly, Hydrogen energy applies for fuel cell by Mg and Mg-based materials. Mg and Mg-based materials are lightweight and low cost materials with high hydrogen storage capacity. However, commercial applications of the Mg hydride are currently hinder by its high absorption/desorption temperature, and very slow reaction kinetics. Therefore one of the most methods to improve kinetics focused on addition transition metal oxide. Addition to transition metal oxide in $MgH_x$ powder produce $MgH_x$-metal oxide composition by mechanical alloy and it analyze XRD, EDS, TG/DSC, SEM, and PCT. This report considers kinetics by transition metal oxide rate and Hydrogen pressure. In this research, we can see behavior of hydriding/dehydriding profiles by addition catalyst (transition metal oxide). Results of PCI make a excellent showing $MgH_x$-5wt.% Sc2O3 at 623K, $MgH_x$-10wt.% $Sc_2O_3$ at 573K.

• Journal of the Mineralogical Society of Korea
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• v.27 no.3
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• pp.125-134
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• 2014

The Janggun mine (Longitude $E129^{\circ}$ 03' 40", Latitude $N36^{\circ}$ 51' 19") was once operated as an underground mine and recently significant amount of mine and leachate water has been discharged from the mine adits and tailing dumps. Mine and leachate waters are characterized by neutral to weakly basic pH values (6.81-9.59). Major cations and anions have concentrations between 6.70-129.80 mg/L of Mg, 289.29-661.02 mg/L of Ca, 4.74-14.38 mg/L of Mn and 1205.00-2448.69 mg/L of $SO{_4}^{2-}$. Brownish yellow precipitates that found in the stream bottom consist of poorly crystallized 2-line ferrihydrite ($Fe_2O_3{\cdot}0.5H_2O$. Scanning electron microscope (SEM) photographs show that brownish yellow precipitates consisted of micro-sized granular particles of about $0.1{\mu}m$ in diameter. Semi-quantitative energy dispersive spectrometry (EDS) analyses show that these samples contained mainly Fe with minor Mn, Ca, Si and As.

• Korean Chemical Engineering Research
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• v.60 no.3
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• pp.446-451
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• 2022

In this study, to improve capacity and cycle stability, the pitch coated nano silicon sheets/CNT composites were prepared through electrostatic bonding of nano silicon sheets and CNT. Silica sheets were synthesized by hydrolyzing TEOS on the crystal planes of NaCl, and then nano silicon sheets were prepared by using magnesiothermic reduction method. To fabricate the nano silicon sheets/CNT composites, the negatively charged CNT after the acid treatment was used to assemble the positively charged nano silicon sheets modified with APTES. THF as a solvent was used in the coating process of PFO pitch. The physical properties of the prepared anode composites were analysed by FE-SEM, XRD and EDS. The electrochemical performances of the synthesized anode composites were performed by current charge/discharge, rate performances, differential capacity and EIS tests in the electrolyte LiPF₆ dissolve solvent (EC:DMC:EMC = 1:1:1 vol%). It was found that the anode material with high capacity and stability could be synthesized when high composition of silicon and conductivity of CNT were used. The pitch coated nano silicon sheets/CNT anode composites showed initial discharge capacity of 2344.9 mAh/g and the capacity retention ratio of 81% after 50 cycles. The electrochemical property of pitch coated anode material was more improved than that of the nano silicon sheets/CNT composites.

• Journal of the Korean Society of Groundwater Environment
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• v.7 no.3
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• pp.103-115
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• 2000

The formation of brown-colored precipitates is one of the serious problems frequently encountered in the development and supply of groundwater in Korea, because by it the water exceeds the drinking water standard in terms of color. taste. turbidity and dissolved iron concentration and of often results in scaling problem within the water supplying system. In groundwaters from the Pajoo area, brown precipitates are typically formed in a few hours after pumping-out. In this paper we examine the process of the brown precipitates' formation using the equilibrium thermodynamic and kinetic approaches, in order to understand the origin and geochemical pathway of the generation of turbidity in groundwater. The results of this study are used to suggest not only the proper pumping technique to minimize the formation of precipitates but also the optimal design of water treatment methods to improve the water quality. The bed-rock groundwater in the Pajoo area belongs to the Ca-$HCO_3$type that was evolved through water/rock (gneiss) interaction. Based on SEM-EDS and XRD analyses, the precipitates are identified as an amorphous, Fe-bearing oxides or hydroxides. By the use of multi-step filtration with pore sizes of 6, 4, 1, 0.45 and 0.2 $\mu\textrm{m}$, the precipitates mostly fall in the colloidal size (1 to 0.45 $\mu\textrm{m}$) but are concentrated (about 81%) in the range of 1 to 6 $\mu\textrm{m}$in teams of mass (weight) distribution. Large amounts of dissolved iron were possibly originated from dissolution of clinochlore in cataclasite which contains high amounts of Fe (up to 3 wt.%). The calculation of saturation index (using a computer code PHREEQC), as well as the examination of pH-Eh stability relations, also indicate that the final precipitates are Fe-oxy-hydroxide that is formed by the change of water chemistry (mainly, oxidation) due to the exposure to oxygen during the pumping-out of Fe(II)-bearing, reduced groundwater. After pumping-out, the groundwater shows the progressive decreases of pH, DO and alkalinity with elapsed time. However, turbidity increases and then decreases with time. The decrease of dissolved Fe concentration as a function of elapsed time after pumping-out is expressed as a regression equation Fe(II)=10.l exp(-0.0009t). The oxidation reaction due to the influx of free oxygen during the pumping and storage of groundwater results in the formation of brown precipitates, which is dependent on time, $Po_2$and pH. In order to obtain drinkable water quality, therefore, the precipitates should be removed by filtering after the stepwise storage and aeration in tanks with sufficient volume for sufficient time. Particle size distribution data also suggest that step-wise filtration would be cost-effective. To minimize the scaling within wells, the continued (if possible) pumping within the optimum pumping rate is recommended because this technique will be most effective for minimizing the mixing between deep Fe(II)-rich water and shallow $O_2$-rich water. The simultaneous pumping of shallow $O_2$-rich water in different wells is also recommended.

• Korean Journal of Heritage: History & Science
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• v.57 no.1
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• pp.146-159
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• 2024

In this study, a study on the production technology of the Buddha statue and the production of raw material origin was conducted through scientific analysis on the Bronze seated Bodhisattva Statue of Goseongsa Temple, a treasure. As a result of microstructure analysis through a metal microscope, it was confirmed that the microstructure of the Bronze seated Bodhisattva Statue of Goseongsa Temple was a process-type dendritic structure, and the casting structure of bronze was well represented, so it was manufactured through casting. Subsequently, as a result of analyzing the alloy composition ratio through SEM-EDS, it was identified as a ternary alloy with 81.26 wt% of copper (Cu) and 16.42 wt% of tin (Sn) and 1.72 wt% of lead (Pb). The results of the analysis of lead isotope ratios using a thermal ionization mass spectrometer (TIMS) were substituted into the distribution of lead isotope ratios on the Korean Peninsula, it was shown in corresponding to Jeolla-do and Chungcheong-do regions and North and South Gyeongsang Province. This suggests that the raw materials used in their production were likely sourced from the mines around Goseong Temple in Gangjin. Despite the fact that the statue is a medium and large Buddha with a total height of 51 centimeters, 1.72 wt% of lead (Pb) was found as a result of alloy composition ratio analysis, which showed a similar composition to the lead content ratio of small bronze and gilt-bronze Buddha statues. Therefore, we compared and analyzed the results of the analysis of the composition ratio of the alloys of bronze and gilt bronze statues, which has been scientifically analyzed with a compositional age similar to that of the Bronze seated Bodhisattva Statue of Goseongsa Temple. Comparison results, Various factors, such as the size of the Buddha statue as well as its stylistic characteristics and the age of composition, may exist in determining the alloy composition ratio of the bronze and gilt bronze Buddha statues, and it was confirmed that the alloy composition ratio or casting technology was properly adjusted when the Buddha statue was created. In other words, it is judged that a more comprehensive system of Buddha statue production technology should be investigated by conducting archaeological and art history studies on stylistic characteristics and age of composition, as well as scientific analysis results such as observation of internal structure, microstructure observation, and analysis of alloy composition ratio using radiation transmission irradiation.

• Clean Technology
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• v.25 no.1
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• pp.81-90
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• 2019

A dielectric barrier discharge (DBD) plasma reactor packed with $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst was used for the dry ($CO_2$) reforming of propane (DRP) to improve the production of syngas (a mixture of $H_2$ and CO) and the catalyst stability. The plasma-catalytic DRP was carried out with either thermally or plasma-reduced $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst at a $C_3H_8/CO_2$ ratio of 1/3 and a total feed gas flow rate of $300mL\;min^{-1}$. The catalytic activities associated with the DRP were evaluated in the range of $500{\sim}600^{\circ}C$. Following the calcination in ambient air, the ${\gamma}-Al_2O_3$ impregnated with the precursor solution ($Ni(NO_3)_2$ and $Ce(NO_3)_2$) was subjected to reduction in an $H_2/Ar$ atmosphere to prepare $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst. The characteristics of the catalysts were examined using X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectrometry (EDS), temperature programmed reduction ($H_2-TPR$), temperature programmed desorption ($H_2-TPD$, $CO_2-TPD$), temperature programmed oxidation (TPO), and Raman spectroscopy. The investigation revealed that the plasma-reduced $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst exhibited superior catalytic activity for the production of syngas, compared to the thermally reduced catalyst. Besides, the plasma-reduced $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst was found to show long-term catalytic stability with respect to coke resistance that is main concern regarding the DRP process.