• Journal of Electrochemical Science and Technology
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• v.14 no.1
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• pp.85-95
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• 2023

In recent years, solid-state Li metal batteries (SSLBs) have attracted significant attention as the next-generation batteries with high energy and power densities. However, uncontrolled dendrite growth and the resulting pulverization of Li during repeated plating/stripping processes must be addressed for practical applications. Herein, we report a plastic-crystal-based polymer/ceramic composite solid electrolyte (PCCE) to resolve these issues. To fabricate the one-side ceramic-incorporated PCCE (CI-PCCE) film, a mixed precursor solution comprising plastic-crystal-based polymer (succinonitrile, SN) with garnet-structured ceramic (Li₇La₃Zr₂O₁₂, LLZO) particles was infused into a thin cellulose membrane, which was used as a mechanical framework, and subsequently solidified by using UV-irradiation. The CI-PCCE exhibited good flexibility and a high room-temperature ionic conductivity of over 10^-3 S cm^-1. The Li symmetric cell assembled with CI-PCCE provided enhanced durability against Li dendrite penetration through the solid electrolyte (SE) layer than those with LLZO-free PCCEs and exhibited long-term cycling stability (over 200 h) for Li plating/stripping. The enhanced Li⁺ transference number and lower interfacial resistance of CI-PCCE indicate that the ceramic-polymer composite layer in contact with the Li anode enabled the uniform distribution of Li⁺ flux at the interface between the Li metal and CI-PCCE, thereby promoting uniform Li plating/stripping. Consequently, the Li//LiFePO₄ (LFP) full cell constructed with CI-PCCE demonstrated superior rate capability (~120 mAh g^-1 at 2 C) and stable cycle performance (80% after 100 cycles) than those with ceramic-free PCCE.

• Korean Journal of Materials Research
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• v.33 no.12
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• pp.530-536
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• 2023

The theoretical capacity of silicon-based anode materials is more than 10 times higher than the capacity of graphite, so silicon can be used as an alternative to graphite anode materials. However, silicon has a much higher contraction and expansion rate due to lithiation of the anode material during the charge and discharge processes, compared to graphite anode materials, resulting in the pulverization of silicon particles during repeated charge and discharge. To compensate for the above issues, there is a growing interest in SiO_x materials with a silica or carbon coating to minimize the expansion of the silicon. In this study, spherical silica (SiO₂) was synthesized using TEOS as a starting material for the fabrication of such SiO_x through heating in a reduction atmosphere. SiO_x powder was produced by adding PVA as a carbon source and inducing the reduction of silica by the carbothermal reduction method. The ratio of TEOS to distilled water, the stirring time, and the amount of PVA added were adjusted to induce size and morphology, resulting in uniform nanosized spherical silica particles. For the reduction of the spherical monodisperse silica particles, a nitrogen gas atmosphere mixed with 5 % hydrogen was applied, and oxygen atoms in the silica were selectively removed by the carbothermal reduction method. The produced SiO_x powder was characterized by FE-SEM to examine the morphology and size changes of the particles, and XPS and FT-IR were used to examine the x value (O/Si ratio) of the synthesized SiO_x.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.1
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• pp.72-81
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• 2024

In this study, DEIPA was used for enhancing cementitious performance of bottom ash replaced cement. By applying the partial or no-known crystal structure method to X-ray diffraction data, the amounts of amorphous bottom ash and calcium silicate hydrate(C-S-H) could be separated and quantified. In the sample without DEIPA, the bottom ash hardly reacted, resulting in low compressive strength. However, the addition of DEIPA not only altered the hydration behavior of the cement but also enhanced the pozzolanic reaction between bottom ash and calcium hydroxide, leading to the generation of additional C-S-H. This resulted in high compressive strength not only in the early stages but also in the later stages. Therefore, with the addition of DEIPA during the pulverization of the bottom ash, the reactivity of the bottom ash was significantly improved. Hence, there is potential in the development of bottom ash replacement cement.

• Journal of the Mineralogical Society of Korea
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• v.31 no.1
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• pp.47-55
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• 2018

Talc, hydrous magnesium phyllosilicate, is one of the most popular industrial minerals due to their chemical stability and adsorptivity. While micro-sized talc has long been used as a filler and coating, nano-sized talc recently is attracting attention as additives for improving the stability of nanocomposites. In this study, we produced the nano-sized talc powder by mechanical method using high energy ball mill and investigated the changes in particle size and crystallinity with increasing milling time up to 720 minutes. X-ray diffraction results show that the peak width of talc gradually as the milling proceeded, and after 720 minutes of pulverization, the talc showed an amorphous-like X-ray diffraction pattern. Lase diffraction particle size analysis presents that particle size of talc which was ${\sim}12{\mu}m$ decreased to ${\sim}0.45{\mu}m$ as the milling progressed, but no significant reduction of particle size was observed even after grinding for 120 minutes or more. BET specific surface area, however, steadily increases up to the milling time of 720 minutes, indicating that the particle size and morphology change steadily as the milling progressed. Scanning electron microscope and transmission electron microscope images shows that layered particles of about 100 to 300 nm was aggregated as micro-sized particles after pulverization for 720 minutes. As the grinding time increases, the particle size and morphology of talc continuously change, but the nano-sized talc particles form micro sized agglomerates. These results suggest that there is a critical size along the a, b axes in which the size of plates is reduced even though the grinding proceeds, and the reduction of plate thickness along the c axis leads the increase in specific surface area with further grinding. This study could enhance the understanding of the mechanism of the formation of nano-sized talc by mechanical grinding.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.4
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• pp.497-505
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• 2005

Domestic Sewage Treatment Plants are mostly based on biological treatment, in which large amounts of excess sludge are generated and occupy about 40 ~ 60% of the total sewage treatment costs. Several methods for sludge treatment has been so far reported as upgrading biodegradation of sludge; heat treatment, chemical treatment, including thermo-alkali and ozone, mechanical treatment including ultrasonic pulverization. But, it has a limitation in case of reducing the amount of excess sludge which are already producted. In this study, application of excess sludge reduction process using thermophilic aerobic bacteria for activated sludge was examined. The research was carried out two different stage. one for a biological wastewater treatment and the other for a thermophilic aerobic solubilization of the waste sludge. A portion of excess sludge from the wastewater treatment step was into the thermophilic aerobic sludge solubilization reactor, in which the injected sludge was solubilized by thermophilic aerobic bacteria. The solubilized sludge was returned to the aeration tank in the wastewater treatment step for its further degradation. Sludge solubilization reactor was operated at $63{\pm}2^{\circ}C$ with hydraulic retention time(HRT) of 1.5 ~ 1.7 day. Control group was operated with activated sludge process(AS) and experiment group was operated with three conditions(RUN 1, RUN 2, RUN3). RUN 1 was operated with AS without sludge solubilization reactor. RUN 2 were operated with AS with sludge solubilization reactor to examine correlation between sludge circulation ratio and sludge reduction ratio by setting up sludge circulation ratio to 3. RUN 3 was operated with sludge circulation ratio of 3 and MLSS concentration of 1,700~2,000mg/L to examine optimum operation condition. The quantity of excess sludge production was reduced sharply and in operation of RUN 3, sludge The quantity of excess sludge production was reduced sharply and in operation of RUN 3, sludge solubilization ratio and sludge reduction ratio were 53. 7%, 95.2% respectively. After steady state operation, average concentration of TBOD, SBOD, $TCOD_{Cr}$, $SCOD_{Cr}$, TSS, VSS, T-N, T-P of effluent were 4.5, 1.7, 27 .8, 13.8, 8.1, 6.2, 15.1, 1.8mg/L in the control group and were 5.6, 2.0, 28.6, 19.1, 9.7, 7.2, 16.1, 2.0mg/L in the experimental group respectively. They were appropriate to effluent standard of Sewage Treatment Plants.

• Korean Journal of Food Science and Technology
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• v.36 no.3
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• pp.501-506
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• 2004

Microflora and contamination process of Saengshik products were investigated to ensure microbial safety of Saengshik. Food-borne pathogenic bacteria, such as Staphylococcus aureus, Bacillus cereus, and Clostridium perfringens detected mainly from grains were not removed by washing with tap water and freeze-drying. Contaminations of food-borne pathogenic bacteria occurred through raw material powder processed at other factories and during actual product manufacturing process, because detection rates of final products were higher than those of raw materials. Concentration of food-borne pathogenic bacteria increased with advancing of process after first pulverization. Dusts of powder and powder attached to machine were good media for air-borne microorganisms and caused to increase of food-borne pathogenic bacteria during process. Improvement of manufacturing process and sanitary control of machines arc necessary to ensure microbial safety of Saengshik.

• Journal of Conservation Science
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• v.23
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• pp.103-118
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• 2008

Hobun(Oyster shell W.) is a traditional material used as extender and white pigment from ancient times. The production method of it, however, has been discontinued. We have studied the traditional production method of Hobun through calcination of oyster shell, which is one of the traditional ways for preparing Hobun. Our work has the important meaning in that we can reproduce the manufacturing method of the discontinued traditional material and also it provides a solid background knowledge to stabilize the production and supply of Hobun for the cultural asset repairing materials. The result can be summarized as followings: The production processes of Hobun by calcination method are divided into 4 steps - calcination ${\rightarrow}$ slaking(pulverization) ${\rightarrow}$ separating fine powder by submergence in water ${\rightarrow}$ drying. In calcination step, the temperature is required to exceed $700^{\circ}$ to get pure white color of Hobun, since organic materials in the shell cause the final powder to be less white below $600^{\circ}$. And the calcination methods produce significant amount of calcium hydroxide, which is incongruent for pigment materials without additional treatments. The experimental study also demonstrated that the additional treatment process introduced in traditional paintings can be a probable process since the calcium of potassium hydroxide is observed to be promoted by this treatment. It is also concluded that, the calcination method of Hobun is appropriate for a small amount and high quality production.

• Journal of the Korean Magnetics Society
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• v.15 no.3
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• pp.191-197
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• 2005

In the fabrication process of Fe-based amorphous alloy powder cores by pulverization of the melt-spun ribbons and cold compaction, the effects of powder preparation method on the magnetic & electric properties, powder shapes and microstructure of cores have been investigated. The powder cores made by using rotor mill showed low effective permeability as compared to the cores prepared by ball milling. However the frequency dependence and quality factor properties were superior in the case of rotor-milling. Further the powders prepared by rotor mill had homogeneous and round shapes through strong shearing in the sieve ring, while the ball milled powders were inhomogeneous and relatively small. The lower permeability of the powder cores fabricated with rotor mill was considered to be due to the high internal stress occurred by very intensive shearing. Moreover the powder cores produced by rotor-milling showed lower core loss and good frequency dependence of effective permeability possibly due to the higher electrical insulation between magnetic particles. The dc bias property of the powder cores made by rotor-milling was better than the one by ball-milling.

• Journal of Environmental Impact Assessment
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• v.21 no.6
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• pp.823-839
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• 2012

Environmental Specimen Banks (ESBs) are playing pivotal role in monitoring the effect of environmental pollution on the ecosystem based on the retrospective analysis of the representative samples collected regularly and stored in cryogenic condition. In Korea, National Environmental Specimen Bank (NESB) was established in 2009 and the standard operating procedures (SOPs) for sampling, and cryogenic milling and storage had been prepared during 2007-2010. Since then, the tentative SOPs for the seven kinds of specimens (shoots of Red Pine (Pinus densiflora) and Korean Pine (Pinus koraiensis), leaves of Mongolian Oak (Quercus mongolica) and Zelkova Tree (Zelkova serrata), eggs of Feral Pigeon (Columba livia var. domestica), muscles and organs of Common Carp (Cyprinus carpio), and Freshwater Bivalve (Unio (Nodularia) douglasiae)) have been put to test in the field and laboratory as well against the practicality and feasibility. The SOPs were improved by reflecting the findings from the research and the following discussion regarding the selection of specimen (Feral Pigeon suffering from a control management), sample size (a problem of decreasing number of sampling trees related to increasing sampling time) and period (a problem related to a bud growth), and sampling methods etc.. In addition, barcoding system for the management of the specimen information, and monitoring system of the cryogenic storage to regulate the optimum temperature and the liquid nitrogen level were also developed for the efficient and effective control of the samples. Lastly, the safety guide and emergency protocol were augmented to guarantee a safe work environment with the cryogenic facility. These improvements of the SOPs are expected to contribute to more stable operation of the NESB.

• Korean Journal of Food Science and Technology
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• v.36 no.6
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• pp.1020-1025
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• 2004

In previous paper, contaminations of food-borne pathogenic bacteria of Saengshik was found to occur during processing, because detection rates of food-borne pathogenic bacteria in final products were higher than those of raw materials. In this study, methods to reduce food-borne pathogenic bacteria and improved manufacturing process were developed for microbial safety of Saengshik. Food-borne pathogenic bacteria in raw materials were reduced to about 0.5-2.0 log cfu/g when seven kinds of raw materials were washed with electrolyzed water and ozonated water, but food-borne pathogenic bacteria could not be removed completely. After improvement of manufacturing process, numbers of food-borne pathogenic bacteria were same or decreased to levels of raw materials. Gaseous ozone and Biocon could control air-borne bacteria under $1{\times}10^1$ cfu/1000 L of air in pulverization and mixing rooms.