• 자원리싸이클링
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• 제24권1호
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• pp.3-11
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• 2015

산 침출에 있어서 생성되는 가용성 실리카는 고액분리 시 여과를 어렵게 하고 목적금속의 순도를 저하시키는 등 습식제련공정에 있어서 큰 문제점으로 대두되고 있다. 따라서 본 고에서는 실리케이트 광물과 산과의 반응성, 가용성 실리카의 특성, 제거방법에 대하여 검토하였다. 가용성 실리카는 알카리 전처리에 의한 제거, 결정상태의 $SiO_2$로 변환, 응집 등의 방법을 통한 여과성 향상 등의 방법으로 처리할 수 있다.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.886-891
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• 2018

Colloid silica using as abrasive for polishing sapphire has been extensively studied, which mechanism has also been deeply discussed. However, by the requirement of application enlargement and cost reduction, some new problems appear such as silica service life time, particle diameter mixing, etc. In this paper, several influences of colloid silica usage on sapphire CMP are examined. Results show particle diameter and concentration, pH value, service life time, particle diameter mixing heavily influence removal rate. Further analysis discloses there are two main effect aspects which are quantity of hydroxyl group, contact area for abrasive density stacking between abrasive and sapphire. Based on the discussions, a dynamic process of sapphire polishing is proposed.

• 상하수도학회지
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• 제27권5호
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• pp.641-648
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• 2013

Arsenic (As) contamination in drinking water is severe problem for about 100 million people who live in Bangladesh, Cambodia, Nepal, India, Vietnam, Myanmar, Mongolia, and Ethiopia etc. Chronic doses cause skin cancer, blackfoot disease, and cardiac damage. Even though the biosand filter (BSF) is popular in many developing countries, it could not remove effectively hazardous ions as As. Adsorbent is effective and feasible to reduce As. In this study the improved biosand filter (iBSF) was embedded with adsorbent, was tested to evaluate As removal as well as organic removal. In 20 days removal of turbidity, bacteria, and $UV_{254}$ have shown 60-95 % removal. Arsenic was removed more than 99.9 % in the columns embedded with silica oxides of ferric manganese ($FM{\alpha}$) while 5.8 ~ 38.3 % in columns without $FM{\alpha}$. Isotherm test showed that average amount of the adsorbed arsenic on the oxides was 0.56 mg/G.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.723-726
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• 2004

In this work, we have studied the CMP characteristics by mixing of original slurry and used slurry in order to investigated the possibility of recycle of used silica slurry. The removal rate and within-wafer non-uniformity (WIWNU) were measured as a function of different slurry composition. Also, we compared the CMP characteristics between self-developed KOH-based silica abrasive slurry and the original slurry. Our experimental results revealed comparable removal rate and good planarity with commercial products.

• 전기전자학회논문지
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• 제23권4호
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• pp.1175-1181
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• 2019

논문에서는 1:10으로 희석된 실리카 슬러리에 산화망간(MnO₂) 연마제를 첨가하여 재처리된 혼합연마제 슬러리(Mixed Abrasive Slurry; MAS)의 화학기계적연마(CMP) 특성을 연구하였다. 최적의 연마 성능을 갖는 슬러리를 설계하기 위해서는 높은 연마율, 하부층에 대한 적절한 연마선택비, 연마 후의 낮은 표면결함, 슬러리의 안정성 등을 얻어야 한다. 산화망간이 첨가된 MAS의 연마 성능은 연마율 및 비균일도와 같은 CMP 성능, 입도 분석, 표면 형상에 대해 평가하였다. 실험결과, 높은 연마율과 낮은 비균일도 측면에서 볼 때 원액 실리카 슬러리와 대등한 슬러리 특성을 얻을 수 있었다. 따라서 본 연구에서 제안하는 MnO₂-MAS를 사용하면 고가의 소모재인 슬러리를 절약하는데 매우 유용할 것이다.

• 한국재료학회지
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• 제16권12호
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• pp.731-738
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• 2006

It is seriously considered using Al CMP (chemical mechanical planarization) process for the next generation 45 nm Al wiring process. Al CMP is known that it has a possibility of reducing process time and steps comparing with conventional RIE (reactive ion etching) method. Also, it is more cost effective than Cu CMP and better electrical conductivity than W via process. In this study, we investigated 4 different kinds of slurries based on abrasives for reducing scratches which contributed to make defects in Al CMP. The abrasives used in this experiment were alumina, fumed silica, alkaline colloidal silica, and acidic colloidal silica. Al CMP process was conducted as functions of abrasive contents, $H_3PO_4$ contents and pressures to find out the optimized parameters and conditions. Al removal rates were slowed over 2 wt% of slurry contents in all types of slurries. The removal rates of alumina and fumed silica slurries were increased by phosphoric acid but acidic colloidal slurry was slightly increased at 2 vol% and soon decreased. The excessive addition of phosphoric acid affected the particle size distributions and increased scratches. Polishing pressure increased not only the removal rate but also the surface scratches. Acidic colloidal silica slurry showed the highest removal rate and the lowest roughness values among the 4 different slurry types.

• Bulletin of the Korean Chemical Society
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• 제26권7호
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• pp.1083-1089
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• 2005

Most experimental studies available in the literature on filtration are based on observed average zeta potential of particles (usually 10 measurements). However, analyses of data using the average zeta potential alone can lead to misleading and erroneous conclusions about the attachment behavior because of the variation of particle zeta potentials and the heterogeneous distribution of the collector surface charge. To study characteristics of zeta potential, zeta potential distributions (ZPDs) of silica particles under 9 different chemical conditions were investigated. Contrary to many researchers’ assumptions, most of the ZPDs of silica particles were broad. The solids concentration removal was better near the isoelectric point (IEP) as many researchers have noticed, thus proper destabilization of particles is very important to achieve better particle removal in particle separation processes. While, the mean zeta potential of silica particles at a given coagulant dose was a function of particle concentration; the amount of needed coagulant for particle destabilization was proportional to the total surface charge area of particles in the suspension.

• 한국막학회:학술대회논문집
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• 한국막학회 2003년도 The 4th Korea-Italy Workshop
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• pp.129-132
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• 2003

Silica/SUS composite membranes were prepared for CO removal from products of methanol steam reforming. A support was prepared by coating Ni powder of sub-micron and SiO$_2$ sols of particle size of 500nm and 150nm in turns on a porous stainless steel (SUS) substrate. Silica top layer was coated on the modified support using colloidal sol with nanoparticle. As a result of mixture gas permeation test of silica composite membrane using H$_2$(99%)/CO(1%), CO concentration of 10000 ppm was reduced to under 81 ppm, which is acceptable in PEMFC anode gas specification. Permeation mechanism through the membrane was mainly molecular sieving.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.567-568
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• 2006

To investigate the recycle possibility of slurry for the oxide-chemical mechanical polishing (oxide-CMP) application, three kinds of retreated methods were introduced as follows: First, the effects on the addition of silica abrasives and the diluted silica slurry (DSS) on CMP performances were investigated. Second, the characteristics of mixed abrasive slurry (MAS) using non-annealed and annealed alumina ($Al_2O_3$) powder as an abrasive added within DSS were evaluated to achieve the improvement of removal rates (RRs) and within-wafer non-uniformity (WIWNU%). Third, the oxide-CMP wastewater was examined in order to evaluate the possible ways of reusing it. And then, we have discussed the CMP characteristics of silica slurry retreated by mixing of original slurry and used slurry (MOS).

• Korean Journal of Chemical Engineering
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• 제35권11호
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• pp.2303-2312
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• 2018

Pretreatment process of silica-coated PET fabrics, a major low-grade PET waste, was developed using the reaction with NaOH solution. By destroying the structure of silica coating layer, impurities such as silica and pigment dyes could be removed. The removal of impurity was confirmed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The pretreated PET fabric samples were used for depolymerization into its monomer, bis(2-hydroxylethyl) terephthalate (BHET), by glycolysis with ethylene glycol (EG), and zinc acetate (ZnAc) catalyst. The quality of BHET was confirmed by DSC, TGA, HPLC and NMR analyses. The highest BHET yield of 89.23% was obtained from pretreated PET fabrics, while glycolysis with raw PET fabric yielded 85.43%. The BHET yield from untreated silica-coated PET fabrics was 60.39%. The pretreatment process enhances the monomer yield by the removal of impurity and also improves the quality of the monomer.