• Journal of Korean Society of Environmental Engineers
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• v.31 no.12
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• pp.1135-1142
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• 2009

This study was carried out to investigate of aerobic granulation by using aerobic granular reactor. To make aerobic granular sludge in short period of time, we used polymer. In reactor, we have studied on physicochemical characteristics of particle size, density, and microbial secreting polymer depending on aerobic particle's formation. The results of running aerobic granular reactor with 3, 6, 9 $kg{\cdot}COD/m^3{\cdot}d$ of COD loading rate and 35 days reaction time showed that particle size were 3.6 mm, 4.3 mm, and 3.4 mm respectively. The settling velocities were 1.5 cm/s, 1.6 cm/s, and 1.2 cm/s respectively. The microbic growth rates were 0.12 $d^{-1}$, 0.135 $d^{-1}$, and 0.133 $d^{-1}$ respectively. The overall result of aerobic granular reactor showed that $6kg{\cdot}COD/m^3{\cdot}d$ of COD loading rate had optimal physicochemical characteristics.

• Korean Journal of Optics and Photonics
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• v.29 no.5
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• pp.215-219
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• 2018

In this paper we show that the localized surface-plasmon resonance of Ag nanoparticles produced by laser dewetting can be effectively utilized for improving the photocurrent and efficiency of a dye-sensitized $TiO_2$ solar cell. An Ag thin film deposited on a conducting glass substrate was dewetted into nanoparticles by a pulsed laser. A dye-sensitized $TiO_2$ solar cell fabricated on this substrate containing the Ag nanoparticles exhibited improved photovoltaic performance, compared to a reference cell. This is attributed to the increased light trapping that arises from the localized surface-plasmon resonance of the dewetted Ag nanoparticles.

• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.92-97
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• 2020

In this study, the solubilities of a pharmaceutical compound, nifedipine, in three mixed solvents were determined. In addition, the nifedipine, that was dissolved in solvents (acetone, DMF, methylene chloride), was recrystallized using antisolvents (water, hexane, carbon dioxide) The external shape, size, and melting point of the crystallized nifedipine were measured. As the mixed solvents, acetone+water, DMF+water, and methylene chloride+hexane were used, and the solubility of nifedipine decreased with increasing antisolvent concentrations in the mixtures. In case of acetone+water, the solubility maximum was observed due to the density anomaly of the mixture, and this phenomenon was not observed in other systems. The crystallized nifedipine particles exhibited the bladed, equant, and prismatic habits, and the particles size was significantly reduced compared to the raw material. The average particle size of raw nifedipine was 337 ㎛, and the size of crystallized particles was in the range of 11.6~69.8 ㎛. All the crystallized nifedipine particles had the same thermal behavior and this result was not influenced by the change of solvent and antisolvent.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.39-44
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• 2023

In this study, the particle size of Si polycrystals was controlled through wet-sedimentation method, and changes in the capacity and cyclic characteristics of the Si anode material according to the particle size were observed. After wet-sedimentation of Si particles pulverized by a vibration mill, the non-uniform particle distribution of Si was uniformly controlled. The d₅₀ of a sample in which Si was sedimented for 24 hours decreased to 0.50 ㎛. As a result of the electrochemical characteristic analysis, the Rct value representing the resistance in the electrode was significantly reduced due to the decrease in particle size. The unclassified Si sample exhibited a discharge capacity of 2,869 mAh/g in the first cycle, and decreased to 85.7 mAh/g after 100 cycles. The sample in which Si was classified for 24 hours showed a capacity of 3,394 mAh/g initially, and maintained a capacity of 1,726 mAh/g after 100 cycles. As the size of the Si particles decreased, the discharge capacity increased and the cycle life was also increased.

• Economic and Environmental Geology
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• v.56 no.5
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• pp.557-564
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• 2023

Nuclear materials such as uranium are used as fuel for nuclear power generation, but there is a high possibility that they will be used for non-peaceful purposes, so international inspections and regulations are being conducted. Isotope analysis data of fine particulate obtained from nuclear facilities can provide important information on the origin and concentration method of nuclear material, so it is widely used in the field of nuclear safety and nuclear forensics. In this study we describe the analytical method that can directly identify nuclear particles and measure their isotopic ratios for fine samples using a large-geometry secondary ion mass spectrometer and introduce its preliminary results. Using the U-200 standard material, the location of fine particles was identified and the results consistent with the standard value were obtained through microbeam analysis.

• Korean Journal of Soil Science and Fertilizer
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• v.39 no.4
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• pp.224-229
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• 2006

Utilization of organic by-product fertilizers has many beneficial effects on agricultural activities and in aspects of the disposal of enormous amounts of livestock manure. Most of these beneficial effects are related to the improvement of soil condition, such as fertility status and physicochemical quality of soil. But, appropriate indexes are needed to effectively manage the quality of organic by-product fertilizers amended on soil. To find chemical and physical standard to control the compost quality, the changes in chemical and physical characteristics of organic by-product fertilizers during composting were investigated, and also an appropriate physical method for this end. The results showed chemical properties, such as humic acid content, OM/N ratio, cation exchange capacity and salt content, had significant relationships during the composting. The water content, particle and bulk densities, particle size and color indices, as physical properties, were also applicable factors for the quality control of compost.

• 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.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.678-683
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• 2012

Ceria is one of the most important catalytic materials which can be used in three-way catalysts, waste water treatment, petroleum refining, etc. So far, many methods have been studied to produce ceria nanoparticles. In this study, ceria nanoparticles were prepared via solvothermal synthesis using supercritical methanol in short reaction time using a batch reactor. The size of synthesized ceria nanoparticles in supercritical methanol is 6 nm without capping agent, which is smaller than that made in supercritical water at the same conditions of $400^{\circ}C$ and 30 MPa. Size difference results from density and critical point difference between water and methanol and slow reaction rate at the surface of ceria particles in supercritical methanol which reduces crystal growth rate. Several organic compounds were added to modify the surface of ceria nanoparticles, and in-situ surface modification was confirmed by FT-IR and TGA analysis. Surface modified ceria nanoparticles have excellent dispersibility in organic solvent. Size and shape of surface modified ceria particles can be controlled by adjusting molar ratio of modifier to precursor and selection of modifier.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.185-185
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• 2012

중공 발광 나노 물질은 특유의 구조적 특성(낮은 밀도, 높은 비표면적, 다공성 물질, 낮은 열팽창계수 등)과 광학적 성질을 이용하여 디스플레이 패널, 광결정, 약물전달체, 바이오 이미징 라벨 등의 다양한 적용이 가능하다. 이러한 적용에 있어 균일한 크기와 형태의 중공 입자는 필수 조건으로 여겨진다. 지금까지 합성된 중공 발광 입자에는 BaMgAl10O17 : Eu2+-Nd3+, Gd2O3 : Eu3+, $EuPO_4{\cdot}H_2O$과 같은 것들이 있으나 크기 조절이 어렵고, 그 균일성이 확보되지 못하였다. 균일한 크기의 중공 발광 입자를 만들기 위해 SiO2나 emulsion을 템플릿으로 이용하여 황화카드뮴, 카드뮴 셀레나이드 중공 입자를 합성한 예가 있으나, 양자점의 독성으로 인하여 바이오분야 응용에는 적합하지 않다. YAG는 모체로써 형광체에서 가장 많이 이용되는 물질로, 화학적 안정성과 낮은 독성, 높은 양자 효율 등 많은 장점을 갖고 있다. 특히 세륨이 도핑된 YAG형광체의 경우 WLED, 신틸레이터, 바이오산업에 적용이 가능하다. 그러나 지금까지 중공 YAG:Ce3+형광체를 합성한 예가 없었다. 본 연구에서는 단분산 수화 알루미늄 (Al(OH)3) 입자 위에 세륨이 도핑 된 이트륨 베이직 카보네이트 ($Y(OH)CO_3$)를 균일하게 코팅한 후 열처리를 하여 균일한 크기의 Y3Al5O12:Ce3+(YAG) 중공 입자를 합성하였다. 열처리 온도에 따른 고분해능 투과 전자 현미경(HRTEM), X-선 회절(XRD), 고분해능 에너지 분광법(HREDX) 분석결과, 중공 YAG: Ce3+입자는 Kirkendall 효과에 의해 형성됨을 확인하였다. 전계방사형 주사 전자 현미경(FE-SEM) 측정을 통해, 열처리 후에도 입자의 크기와 형태가 균일함을 확인하였으며, 공초점 현미경 관찰을 통해 중공 형태를 명확히 확인 할 수 있었다. Photoluminescence (PL) 분광법과 형광 수명 이미징 현미경(FLIM)을 이용한 광 특성 분석결과, 합성된 입자는 400-500 nm에서 흡수 파장 (456 nm에서 최대 강도)과 500-700 nm 범위의 발광 파장(544 nm에서 최대 강도)을 나타냈고, 상용 YAG: Ce3+(70 ns)에 준하는 74 ns의 잔광 시간(decay time)이 측정되었다. 단분산 수화 알루미늄 입자의 크기를 조절하여 최종 합성된 YAG: Ce3+의 크기를 조절할 수 있었다. 지름 약 600 nm의 Al(OH)3를 사용한 경우, $1,300^{\circ}C$에서 열처리를 한 후 평균 지름 590 nm의 중공입자를 합성하였고, 약 170 nm의 Al(OH)3를 이용하여, 더 낮은 온도인 $1,100^{\circ}C$에서의 열처리를 통해 평균지름 140 nm의 중공 YAG: Ce3+입자를 합성하였다. 본 연구를 통하여 합성된 균일한 크기의 YAG 중공입자는 LED와 같은 광전변환 소자 및 다기능성 바이오 이미징 등의 나노바이오 소자 분야에 활용될 수 있음이 기대된다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.500-507
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• 2008

By Using various grinding mill in powder cosmetics manufacturing process; screen milt and pin mill, jet mill, properties of the powder and grinding mills were studied; talc, mica, nylon powder, silica, titanium dioxide. Besides, the experiments fur evaluation of grinding were performed by using iron oxides those are tracers. In powders of plate shape, they were grinded more vertically than horizontally at the screen mill and pin mill, although were all grinded vertically and horizontally at the jet mill. The spheric powders became the primary particles or aggregation by electrostatic interaction at the screen mill and pin mill. But, at the jet mill, they resulted the agglomeration or transformation or damage up to 2bar. Titanium dioxides became the primary particles by all grinding mill. Pin mill has an excellent result in experiments which is a change of the tone of color by grinding. From these results, suggest that the jet mill is used to pre-treat of powders of plate shape in practical cosmetic manufacturing process, and the screen mill and pin mill are used to match the color of powder cosmetics. If industrial process condition is taken into consideration, suggest that 4times of grinding is excellent on grinding effect by the screen mill, and twice grinding by the pin mill and grind air pressure of 1bar by the jet mill.