• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.309-312
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• 2004

The electronic structure of ZnO oxide semiconductor having high optical transparency and good electric conductivity was theoretically investigated by $DV-X_{\alpha}$(the discrete variation $X_{\alpha}$) method, which is a sort of the first principle molecular orbital method using Hatre-Fock-Slater approximation. The electrical and optical properties of ZnO are seriously affected by the addition of impurities. The imnurities are added to ZnO in order to increase the electric conductivity of an electrode without losing optical transparency. In this study, the effect of impurities of III and IV family on the band structure, impurity levels and the density of state of ZnO were investigated. The cluster model used for calculations was $[MZn_{50}O_{53}]^{-2}$(M=elements belonging to III and IV family).

• 한국재료학회지
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• 제21권12호
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• pp.673-678
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• 2011

With an increased production of Printed Circuit Boards (PCBs) in electronic equipment, the consumption of solder alloys is growing globally. Recently, increasing importance of recycling solder scrap has been recognized. Generally, solder scrap contains many impurities such as plastics and other metals. Hazardous components must be eliminated for recycling solder scrap. The present work studied pretreatment for reuse of solder scrap alloys. An experiment was conducted to enhance the cleanliness of solder scrap melt and eliminate impurities, especially lead. Physical separation with sieving and magnetic force was made along with pyrometallurgical methods. A small decrease in lead concentration was found by high temperature treatment of solder scrap melt. The impurities were removed by filtration of the solder scrap melt, which resulted in improvement of the melt cleanliness. A very low concentration of lead was achieved by a zone melting treatment with repeated passage. This study reports on a pretreatment process for the reuse of solder scrap that is lead free.

• 한국산업융합학회 논문집
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• 제24권5호
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• pp.581-587
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• 2021

In recent years, contamination of drinking water sources has emerged as a serious social problem, such as a large number of impurities in tap water or groundwater or the supply of suitable water due to rust of pipes. Although the government and public institutions are implementing various measures to protect water sources, they cannot improve water quality in a short period of time because of the enormous cost involved. Therefore, in recent years, preference has been given to a device that converts tap water, which is hard water, into soft water by installing a separate water softener at the faucet from which tap water is discharged. However, the existing filtration device has a problem that filtration performance is gradually lowered when impurities accumulate in the filter, requiring continuous filter replacement. In this study, the optimal design of the filter housing was performed to develop a water softener that can be washed when impurities accumulate on the filter inside the water softener connected to the faucet. For optimal design of the filter housing, fluid and fluid-structural interaction analysis were performed on the design pressure to determine the shape and thickness of the housing, and design review was performed through prototype.

• Environmental Engineering Research
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• 제24권2호
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• pp.181-190
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• 2019

Constructed wetlands are improvised man-made systems, designed for adopting the principle of natural wetlands for purifying wastewater - the elixir of life. They are used widely as a cost-effective and energy-efficient solution for treating greywater generated from different tertiary treatment sources. It provides an elaborate platform for research activities in an attempt to recycle earth's natural resources. Among the several organic impurities removal mechanisms existing in constructed wetland systems, the earth's active microbial population plays a vital role. This review deals with the recent advancements in constructed wetland systems from a microbiological perspective to (effect/ devise/ formulate) chemical and physical treatment for water impurities. It focuses on microbial diversity studies in constructed wetlands, influence of wetland media on microbial diversity and wetland performance, role of specific microbes in water reuse, removal of trace elements, some heavy metals and antibiotics in constructed wetlands. The impurities removal processes in constructed wetlands is achieved by combined interactive systems such as selected plant species, nature of substrate used for microbial diversity and several biogeochemical effected reaction cycles in wetland systems. Therefore, the correlation studies that have been conducted by earlier researchers in microbial diversity in wetlands are addressed herewith.

• Archives of Metallurgy and Materials
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• 제66권3호
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• pp.729-733
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• 2021

Ferrotitanium can be produced as a method of recycling Ti scraps. The eutectic composition of ferrotitanium, Fe_29.5Ti_70.5, can be obtained as a nanocrystalline phase due to relatively low melting point. Fe_29.5Ti_70.5 in which FeTi and β-Ti form a lamellar structure have high strength but low strain. To improve this, impurities were removed through hydrogen plasma arc melting (HPAM) and annealed. HPAM can remove substitutional/interstitial solid solutions. As a result, from 6733 ppm to 4573 ppm of initial impurities were removed by HPAM process. In addition, the strain was improved by spheroidizing and coarsening the lamellar structure through annealing. The effect of impurities removed through HPAM on the Young's modulus, yield strength, and strain was observed.

• 분석과학
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• 제18권1호
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• pp.5-12
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• 2005

고정밀 전자소자의 오동작의 한 원인인 soft error는 원료물질에 함유된 U, Th과 같은 알파방출 불순물로 알려져 있으며 전자소자의 소형화, 고집적화에 따라서 이들 불순물의 규제함량은 기존의 분석법으로는 불가능할 정도로 낮아지고 있다. 연구의 목적은 다양한 전자소자의 밀봉소재로 사용되는 EMC (epoxy molding compound)의 주 원료인 고순도 실리카에 함유되어 있는 U, Th을 고감도 (ng/g이하)로 분석할 수 있는 방사화분석법과 감마선분광분석법의 개발이다. 지금까지 방사화분석법에 이용하던 PTS (pneumatic transfer system) 중성자 조사 설비로는 산업계에서 요구하는 분석 감도를 충족시킬 수 없기 때문에 의약용 혹은 산업용 RI 생산에 주로 사용되고 있는 HTS (Hydraulic transfer system) 중성자 조사 설비를 이용한 방사화분석 조건을 확립하였다. 또한, 공기중 라돈 ($^{222}Rn$)과 자핵종 (progenies)에 의한 불안정한 바탕방사능은 분석의 감도는 물론 정확도를 저하시키는 주 요인으로 작용하므로 질소가스 유입시스템을 제작하여 라돈에 의한 바탕방사능을 소멸 혹은 안정화시켰다. 그 결과 U과 Th의 분석한계를 각각 0.1 ng/g, 0.01 ng/g까지 낮출 수 있었다.

• 한국산학기술학회논문지
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• 제14권8호
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• pp.3597-3601
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• 2013

본 연구에서는 고품질의 합성다이아몬드를 얻고자 합성다이아몬드 표면에 잔류하는 그래핀, DLC 등의 흑연계 준안정상을 효과적으로 제거하는 세정공정을 위해 왕수와 황산 외에 $K_2S_2O_8$, $P_2O_5$, $KMnO_4$의 산화제가 들어간 습식세정공정, P II 제안하였다. 이 공정은 기존의 산처리를 이용한 세정공정(P I) 뿐만 아니라 신세정공정(P I+P II)을 함께 사용하여 7GPa-$1500^{\circ}C$-5minutes의 조건 하에서 합성된 200um의 다이아몬드 표면에 잔류하는 흑연과 불순물 등을 제거하기 위해 진행되었다. 이를 육안분석, 광학현미경, 마이크로라만, TGA-DTA를 통하여 확인하였다. 육안분석과 광학현미경 분석 결과 새로운 습식세정공정(P I+P II) 진행 후 합성다이아몬드의 채색이 밝은 노란색으로 개선되었다. 또한 마이크로라만 분석을 통해 $1330cm^{-1}$의 다이아몬드 고유 피크 외에 $1440cm^{-1}$의 흑연계 준안정상인 DLC피크가 사라지는 것을 확인하여 정량적으로 잔류불순물의 양이 줄어든 것을 확인하였다. TGA-DTA 결과, 처리 전(P I only) 흑연계 준안정상이 먼저 분해되어 $770.91^{\circ}C$부터 열분해가 시작되었으나 신세정공정(P I+P II)으로 처리 후 순수한 합성다이아몬드는 $892.18^{\circ}C$부터 시작되어 흑연계 준안정상이 효과적으로 제거된 것을 확인하였다. 이러한 신세정공정은 합성다이아몬드의 잔류불순물제거를 통해 품질향상을 기대할 수 있었다.

• 멤브레인
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• 제32권5호
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• pp.314-324
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• 2022

본 연구에서는 분리막을 이용하여 천일염내 미세플라스틱을 비롯한 불순물을 제거하는 분리막 공정 설계를 위한 연구이다. 천일염 염전에 적합한 분리막 재질, 공경 사이즈, 모듈을 선정하여 다양한 조건에서 실험을 진행하였다. 선정된 200 kDa, 4 kDa 한외여과막 그리고 3 kDa 나노여과막을 선정하였고, 실험은 실험실과 실제 염전에 파일롯 플랜트를 건설하여 각각 실험하였다. 천일염내 불순물은 대부분 0.1 ㎛ 이상의 크기를 가졌고 크기 분포는 0.1 ㎛에서 1 ㎛ 사이 입자가 가장 많은 부분을 차지하였다. 그리고 성분 분석결과 불순물 내에 7종류 이상의 다양한 미세플라스틱이 검출되었다. 분리막 공정 이후 여과된 염전수 분석한 결과 미세플라스틱을 포함한 불순물이 검출되지 않았고 기존의 천일염과 분리막 여과수로 제작한 천일염의 성분 비교해본 결과 천일염 성분의 변화 없이 불순물만 효과적으로 제거됨을 확인하였다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 1998년도 춘계연구발표회 논문개요집
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• pp.124-124
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• 1998

• 한국진공학회:학술대회논문집
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• 한국진공학회 2003년도 제24회 학술발표회 초록집
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• pp.63-63
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• 2003