• Korean Journal of Materials Research
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• v.18 no.11
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• pp.604-609
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• 2008

The sintering behavior of zircon with silica was investigated. Zircon with 5 vol% of sedimentation $SiO_2$ resulted in the apparent density of $4.45\;g/cm^3$, the diametral tensile strength of $12.125\;kgf/cm^2$, and the micro Vickers hardness of 1283 HV. The dissociation temperature and mechanical characteristics of the $ZrSiO_4$ were changed with different kinds of $SiO_2$. $SiO_2$ addition prevented dissociation of $ZrSiO_4$. Zircon with 5 vol% of sedimentation $SiO_2$ and with 5 vol% of fused $SiO_2$ resulted in increased diametral tensile strength and increased micro Vickers hardness by suppression of $ZrSiO_4$ dissociation and low temperature liquid $SiO_2$ formation. Zircon with fumed $SiO_2$ and quartz $SiO_2$ resulted in decreased diametral tensile strength and decreased micro Vickers hardness because of cristobalite and quartz phase formation and high temperature liquid $SiO_2$ formation. Zircon with 10 vol% of $SiO_2$ resulted in decreased diametral tensile strength and decreased micro Vickers hardness because of weak particle coupling due to excess formation of liquid $SiO_2$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.112-112
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• 2008

최근 Ruthenium (Ru) 은 높은 화학적 안정성, 누설전류에 대한 높은 저항성, 저유전체와의 높은 안정성 등과 같은 특성으로 인해 금속층-유전막-금속층 캐패시터의 하부전극으로 각광받고 있다. 또한 Cu와의 우수한 Adhesion 특성으로 인해 Cu 배선에서의 Cu 확산 방지막으로도 주목받고 있다. 그러나 이렇게 형성된 Ru 하부전극의 각 캐패시터간의 분리와 평탄화를 위해서는 CMP 공정이 도입이 필요하다. 이러한 CMP 공정에 공급되는 Slurry 에는 부식액, pH 적정제, 연마입자 등이 첨가되는데 이때 연마입자가 응집하여 Slurry의 분산 안전성 저하에 영향을 줄수 있다. 이로 인해 응집된 Slurry는 Scratch와 Delamination 과 같은 표면 결함을 유발할 수 있으며, Slurry의 저장 안정성을 저하시켜 Slurry의 물리적 화학적 특성을 변화시킬 수 있다. 그리하여 본 연구에서는 Ru CMP Slurry에서의 Surfactant와 같은 분산 안정제에 따른 Surface tension, Zeta potential, Particle size, Sedimentation의 분석을 통해 Slurry 안정성에 대한 영향을 살펴보았다. 그 결과 pH9 조건의 31ppm Dispersant 농도에서 50%이상의 Sedimentation 상승효과를 얻을 수 있었다. 또한 선택된 Surfactant가 첨가된 Ru CMP Slurry를 제조하여 Ru wafer의 Static etch rate, Passivation film thickness 와 Wettability를 비교해 보았다. 그리고 CMP 공정을 실시하여 Ru의 Removal rate와 TEOS에대한 Selectivity를 측정해 보았다.

• Analytical Science and Technology
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• v.24 no.6
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• pp.429-434
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• 2011

In this study, a wet-sampler was developed for collection in water and simultaneous fractionation of micron-sized particles (e.g., pigment, airborne, etc.). In this new device, three cylinders (partially filled with water) through which air was forced to pass for sample collection are connected in a series. Particles of different sizes are collected in different cylinders, allowing simultaneous fractionation. An uniqueness of this new device is that it does not use any membrane filter. Microparticles are collected directly in cylinders filled partially with water. Also the particles are simultaneously fractionated within this device while they are being collected. The new device was employed for collection of airborne particles. The collected airborne particles were fractionated by using sedimentation field-flow fractionation, SdFFF), and observed with an optical microscopy (OM) for size and shape analysis. Also AAS and ICP-AES were used for composition analysis of the airborne particles. It is expected that the new device is applicable to collection and analysis of size distribution of various types of microparticles.

• Journal of Environmental Science International
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• v.33 no.9
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• pp.667-674
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• 2024

In the present study, we aimed to determine the optimal polyaluminum chloride (PAC) dosage in raw water based on the PO₄^3--P concentration using PAC coagulants with aluminum concentrations of 10%, 12%, and 17%. The correlation between the Al/P molar ratio and the removal efficiency of aggregated Al-PO₄^3--P flocs was evaluated using sedimentation and flotation processes. As the PO₄^3--P concentration in the raw water increased, the Al/P molar ratio gradually decreased from 6.14 to 1.98. The Al/P molar ratio of PAC formulations with higher aluminum contents showed a decreasing trend in the following order: PAC 17% < PAC 12% < PAC 10%. An increase in the Al/P molar ratio led to a slight increase in the average particle size of Al-PO₄^3--P flocs formed during the coagulation process. At optimal Al/P molar ratios, PO₄^3--P removal efficiency ranged from approximately 80% to 93% for both the coagulation/precipitation and coagulation/flotation processes. The coagulation/flotation process exhibited a slightly higher PO₄^3--P removal efficiency than coagulation/precipitation.

• Journal of Korean Society of Water and Wastewater
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• v.34 no.3
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• pp.211-220
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• 2020

When domestic sewage and rainwater runoff are discharged into a single sewer pipe, it is called a "combined sewer system." The sewage design standards in Korea specify the flow velocity based only on the volume of rainfall; therefore, sedimentation occurs on non-rainy days owing to the reduced flow rate and velocity. This sedimentation reduces the discharge capacity, causes unpleasant odors, and exacerbates the problem of combined sewer overflow concentration. To address this problem, the amount of sewage on non-rainy days, not just the volume of rainfall, should also be considered. There are various theories on sedimentation in sewer movement. This study introduces a self-cleansing velocity based on tractive force theory. By applying a self-cleansing velocity equivalent to the critical shear stress of a sand particle, sedimentation can be reduced on non-rainy days. The amount of sewage changes according to the water use pattern of citizens. The design hourly maximum wastewater flow was considered as a representative value, and the velocity of this flow should be more than the self-cleansing velocity. This design method requires a steeper gradient than existing design criteria. Therefore, the existing sewer pipelines need to be improved and repaired accordingly. In this study, five types of improvement and repair methods that can maximize the use of existing pipelines and minimize the depth of excavation are proposed. The key technologies utilized are trenchless sewer rehabilitation and complex cross-section pipes. Trenchless sewer rehabilitation is a popular sewage repair method. However, it is complex because the cross-section pipes do not have a universal design and require continuous research and development. In an old metropolis with a combined sewer system, it is difficult to carry out excavation work; hence, the methods presented in this study may be useful in the future.

• Journal of the Korean GEO-environmental Society
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• v.23 no.9
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• pp.33-40
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• 2022

Sedimentation and pH neutralization has been investigated as preteatment of acid contaminate water. The settling and neutralizing process derive more effective degradation efficiency as the pre-treatment process before the removal process of adsorption, volatile, biodegradation, or oxidation. Settling velocity, uniformity coefficient, coefficient of curvature, and grain size index can define in the sedimentation process for characteristics of the soil. The stainless steel sieve has been used to separate each particle size of the dry soil by assembling in order of 4, 10, 20, 40, 80, 100, and 200 mesh sizes. The soil from Gamcheon Port in Busan drops upper side of the sieve and shakes back and forth to separate each different size of the particle. The 1L of Imhoff cone and 200 mL of the mass cylinder were used as settling tanks to calculate settling velocity. Stokes' equation was used to figure out the average density of dry soil with a value from settling velocity. In the results, the average particle density and lowest settling velocity were 1.93 g/cm³ and 0.11 cm/s, respectively. These values can detect the range of settling points of sediment to prevent chemical accidents. In pH neutralization, the initial pH of 2, 3, 4, and 5 of nitric acid and sulfuric acid are used as an acid solution; 0.1, 0.01, and 0.001 M of sodium hydroxide and calcium hydroxide are used as a base solution. The main goal of this experiment is to figure out the volume percentage of the acid solution becomes pH 7. The concentration of 0.001 M of base solution exceeds all the conditions, 0.01 M exceeds partially, and 0.1 M does not exceed 5 v/v% except pH 2. Calcium hydroxide present less volume than sodium hydroxide at pH neutralization both sulfuric and nitric acid.

• Journal of Korean Society of Water and Wastewater
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• v.12 no.2
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• pp.31-41
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• 1998

As the leakage of crude oil from tankers breaks out frequently, it caused a serious problem for ocean pollution and calls for developing treatments to handle the leaked crude oil and mitigate the pollution. Thus it is required to develop new purification technolgies and appropriate treatment systems which have sufficient treatment capability in order to cope with the anticipated ocean pollution. In this experiment, A and B type heavy oils were used to make the emulsion of both water containing heavy oil and sea-water containing heavy oil. The following are the main results from this study ; 1. When A and B type heavy oils were added to the original sea-water and treatedin the homogrenizer respectively, the particle of oil beacame smaller in both cases. Under the same condition, while the initial oil density of sea-water containing B-heavy oil is higher than of emulsion with A-heavy oil, the particle of A-heavy oil is finer than that of B-heavy oil. 2. When A and B type heavy oils were added to distilled water and treated in the homogenizer respectively, the particle was more dispersed and finer than that in the case of sea-water in both cases. In this result, the water containing oil formed more stable emulsion than the sea-water containing oil. 3. In this experiment, all emulsions showed oil in water types. 4. Since the oil particle is larger in the sea-water than in the distillated water, interms of elimination of oil, it is thought to be more important to give Membrane treatment after implementing sandfilter, activity carbon, coagulation-sedimentation and floating separation as pre-treatment.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.5
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• pp.8-13
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• 2012

The flexography ink has disadvantage in a deinking process because it tends to form too fine particles in alkali condition to be removed in flotation deinking. The influence of pH conditions on the particle size of phthalocyanine cyan ink used for flexo-printing was investigated to see the effect of pH conditions on flexography ink dispersion. Flexography ink particles prepared by grinding dried ink films were used in this experiment. Greater reduction of the ink particle size was noticed under alkaline pH condition, which was attributed to dissolution of resin component of the ink. Adsorption behavior of flexography ink onto pigment particles was examined using clay and talc as substrate pigments. Pretreatment of inorganic pigments with a cationic poly-DADMAC increased the surface adsorption of flexography ink particles, which improved the removal of the inks by centrifugal sedimentation of inorganic pigments. Most efficient removal of the ink particles was achieved when an optimal addition level of the cationic polymer was used for pretreatment of inorganic pigments, and this optimal addition level corresponds to the surface saturation point of the polyelectrolyte. Adsorption of flexography ink particles onto inorganic pigments improved the ink removal in flotation deinking since the pigment particles has the optimal particle size for flotation deinking.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.516-520
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• 2008

There are many water treatment plants built over couple of decade ago in Korea. For most of those plants, they are required a countermeasure to cope with the deterioration caused from the superannuated facilities and the objective materials change of water treatment from inorganic particles like clay to algae particles due to eutrophication of lake and reservoir. A series of field and laboratory experiments was performed to investigate the feasibility of DAF hybrid process and the variation of particle characteristics by applying the additional DAF unit in conventional water treatment processes. On the basis of this experiments, the DAF was effective as an additive process in filtration basin (DAF-CSF combination processes). Using DAF-CSF combination process, the efficiency of stable particle removal can be achieved to produce the safe drinking water.

• Journal of the Korean Geosynthetics Society
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• v.12 no.3
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• pp.87-94
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• 2013

As sediment contamination problems have recently been raised in Korea, the need for technologies to remove contaminants in sediments has increased. Contaminated sediments in Korea has been annually dredged and treated using processes of coagulation/flocculation, sedimentation on barges, dewatered and dried at prepared site, and then disposed at a landfill site, which is very costly, and only a limited landfill space available in Korea. Contaminants in media containing a high percentage of silt and clay sized particles, typically, are strongly adsorbed on the particles and difficult to remove. Particle separation processes that separate the fine clay and silt particles from the coarser sand and gravel and concentrate the contaminants into a smaller volume of sediment that can be further treated of disposed of, are very effective in the post step processes. In this study are to test the feasibility of treating dredged sediments using a hydrocyclone process, and to estimate design parameters for a pilot scale test. A hydrocyclone was operated to separate larger particles from the sediments. It was found that the particle separation was greatly affected by the solid contents and inlet pressure in the hydrocyclone.