• 자원환경지질
• /
• 제40권5호
• /
• pp.587-604
• /
• 2007

회동저수지의 호저퇴적물에 대하여 미량원소의 심도별 변화와 존재형태 및 이들의 상관관계에 대해서 알아보고자 하였다. 회동저수지의 5개 지점에서 깊이 21-41cm의 코어와 간극수를 채취하였다. 회동저수지 퇴적물 내 미량원소의 평균 총함량은 Zn $232{\pm}30.8mg/kg$, Cu $119{\pm}272mg/kg$, Pb $58.4{\pm}4.1mg/kg$, Ni $15.7{\pm}3.3mg/kg$ 및 Cd $1.6{\pm}0.3mg/kg$이었다. 회동저수지 안쪽으로 가면서 호저퇴적물 내 미량원소 함량이 감소하는 경향이 관찰되었다. 깊이에 따른 함량 변화는 시료채취 위치에 상관없이 Mn, Pb 및 Zn는 감소하는 반면, Cu와 Fe는 증가하였다. 간극수에 용해된 미량원소의 함량은 Fe>Mn>Cu>Zn의 순으로 낮았고 Cd, Ni 및 Pb는 검출되지 않았다. 간극수에 용해된 Zn, Cu, Fe 및 Mn 함량은 퇴적층의 하부로 가면서 증가하는 경향을 보여주고 있으며, 이는 상부로 미량원소가 확산되고 있음을 의미한다. 이러한 미량원소의 이동은 퇴적물-물과의 경계부분까지 전달될 것이며, 퇴적층 상부에서 비정질 철 및 망간 산화광물과 탄산염광물에 의하여 흡착되고 있다. 겉보기 분산계수 값을 이용한 결과, 각 미량원소의 상대적인 이동도는 Mn>Cu>Zn>Fe순이다. 연속추출결과, 미량원소의 표면집적이 비정질 산화광물형태와 탄산염광물 수반형태에 기인된 것임을 확인하였다. Cu, Fe, Mn 및 Zn의 간극수 내 함량은 호저퇴적물의 양이온교환형태와 밀접한 상관관계가 있음이 관찰되었다.

• 자원환경지질
• /
• 제40권4호
• /
• pp.491-496
• /
• 2007

본 연구는 구과상암 형성의 원리로 알려진 리제강 현상을 화학적으로 실험하여 분석한 것으로 매질의 종류에 따라, 또한 내부전해질과 외부전해질이 바뀌었을 때 같은 리제강 링의 형태가 다르게 나타났다. 매질의 종류로는 한천, 젤라틴, 청포묵을 사용하였으며 한천은 1%, 젤라틴은 2%, 그리고 청포묵은 5%를 포함하여 0.01M 내부전해질 용액을 만들어 12시간동안 실온에서 굳혔을 때 외부전해질의 확산을 실험하기에 적절한 점성도를 유지하였으며 리제강 고리가 각 화학성분의 특성에 따라 선명하게 형성되는 현상을 볼 수 있었다. 용해도곱상수($K_{sp}$)가 $7.9{\times}10^{-9}$는 내부전해질 0.01M KI와 외부전해질 25% $Pb(NO_3){_2}$가 반응하여 생성한 리제강 링 간격이 0.01cm에서 0.12cm로 좁지만 점점 커지는 반면, 가 $8.3{\times}10^{-17}$는 내부전해질 0.01M KI와 외부전해질 25% $AgNO_3$이 반응하여 생성한 리제강 링간 간격은 0.7cm에서 0.45cm로 점점 작아지는 것으로 보아 화학적으로 리제강 링의 생성에서 링 간의 간격이나 전체 링의 생성 크기는 침전 물질의 용해도곱상수와 상관관계가 있는 것으로 나타났다.

• 마이크로전자및패키징학회지
• /
• 제26권3호
• /
• pp.81-88
• /
• 2019

본 연구에서는 그래핀 산화(graphene oxide, GO) 분말 첨가가 ball grid array(BGA) 패키지와 printed circuit board(PCB)간 Sn-3.0Ag-0.5Cu(SAC305) 무연솔더 접합부의 electromigration(EM) 수명에 미치는 영향에 대하여 보고 하였다. 솔더 접합 직후, Ni/Au표면처리된 패키지 접합계면에서는 $(Cu,Ni)_6Sn_5$가 생성되었으며 organic solderability preservative(OSP) 표면처리 된 PCB 접합계면에서는 $Cu_6Sn_5$ 금속간화합물(intermetallic compound, IMC)이 생성되었다. $130^{\circ}C$, $1.0{\times}10^3A/cm^2$ 전류밀도 하에서 EM 수명평가 결과, GO를 첨가하지 않은 솔더 접합부의 평균 파괴 시간은 189.9 hrs으로 도출되었고, GO를 첨가한 솔더 접합부의 평균 파괴 시간은 367.1 hrs으로 도출되었다. EM에 의한 손상은 패키지 접합계면에 비하여 pad 직경이 작은 PCB 접합계면에서 전자 유입에 의한 Cu의 소모로 인하여 발생하였다. 한편, 첨가된 GO는 하부계면의 $Cu_6Sn_5$ IMC와 솔더 사이에 분포하는 것을 확인하였다. 따라서, SAC305 무연솔더에 첨가된 GO가 전류 집중 영역에서 Cu의 빠른 확산을 억제하여 우수한 EM 신뢰성을 갖는 것으로 생각된다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
• /
• pp.163.1-163.1
• /
• 2016

Lead halide perovskites CH3NH3PbX3 (X=Cl, Br, I) have received great interest in the past few years because of their excellent photoelectronic properties as well as their low-cost solution process. Their theoretical efficiency limit of the solar cell devices was predicted around 31% by a detailed balance model for the reason that exceptional light-harvesting and superior carrier transport properties. Additionally, these excellent properties contribute to the applications of optoelectronic devices such as LASERs, LEDs, and photodetectors. Since these devices are mainly using perovskite thin film, one of the most important factor to decide the efficiency of these applications is the quality of the film. Even though, optoelectrical devices are composed of polycrystalline thin film in general, not a single crystalline form which has longer carrier diffusion length and lower trap density. For these reasons, monodomain perovskite thin films have potential to elicit an optimized device efficiency. In this study, we analyzed the crystallography of the in-plane aligned perovskite thin film by X-ray diffraction (XRD) and selected area electron diffraction (SAED). Also the basic optic properties of perovskites were checked using scanning electron microscopy (SEM) and UV-Vis spectrum. From this work, the perovskite which is aligned in all directions both of out-of-plane and in-plane was fabricated and analyzed.

• 환경영향평가
• /
• 제16권1호
• /
• pp.35-43
• /
• 2007

Vitrified aggregates obtained by using mine tailings were evaluated using various leaching methods to assess their environmental safety. The leaching tests in this study include continuous batch leaching, Dutch availability leaching, pH-stat and tank diffusion test as well as TCLP (Toxicity Characteristic Leaching Procedure), which is commonly adopted. Vitrification technique has successfully been applied treating some solid wastes containing high level of heavy metals, such as EAF (Electric Arc Furnace) dust and mine tailings. The potentially most leachable element among trace metals was As and theoretically about 7% of total concentrations in the aggregate can be released under extreme condition. Zinc was leached about 4% and the other trace metals including Cd, Cr and Pb were hardly released from the vitrified mine tailing aggregate.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
• /
• pp.475-480
• /
• 2002

The reliability of the solder joint is affected by type and extent of the interfacial reaction between solder and substrates. Therefore, understanding of intermetallic compounds produced by soldering in electronic packaging is essential. In-based alloys have been favored bonding devices that demand low soldering temperatures. For photonic and fiber optics packaging, m-based solders have become increasingly attractive as a soldering material candidate due to its ductility. In the present work, the interfacial reactions between indium solder and bare Cu Substrate are investigated. For the identification of intermetallic compounds, both Scanning Electron Microscopy(SEM) and X-Ray Diffraction(XRD) were employed. Experimental results showed that the intermetallic compounds, such as Cu$_{11}$In$_{9}$ was observed for bare Cu substrate. Additionally, the growth rate of these intermetallic compounds was increased with the reaction temperature and time. We found that the growth of the intermetallic compound follows the parabolic law, which indicates that the growth is diffusion-controlled.d.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 하계학술대회 논문집
• /
• pp.395-397
• /
• 2002

Dielectric thin films of Pb$\_$0.72/La$\_$0.28/Ti$\_$0.93/O$_3$(PLT(28)) have been deposited on Pt(111)/Ti/SiO$_2$/Si(100) substrates in-situ by pulsed laser deposition using different annealing and deposition processes. We have investigated the effect of hydrogen annealing on the ferroelectric properties of PLT thin films and found that the annealing process causes the diffusion of hydrogen into the ferroelectric film resulting in the destruction of polarization. Two-step process to grow PLT films was adopted and verified to be useful to enlarge the grain size of the film. Structural properties including dielectric constant, and ferroelectric characteristics of PLT thin films were shown to be strongly influenced by grain size. The film deposited by using two-step process including pre-annealing treatment has a strong (111) orientation. However, the films deposited by using single-step process with hydrogen annealing process shows the smallest grain size.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
• /
• pp.25-27
• /
• 2005

Sn-9Zn solder balls were bonded to Cu and ENIG (Electroless Nickel/Immersion Gold) pads, and the effect of aging on their joint reliability was investigated. The interfacial products were different from the general reaction layer formed in a Sn-base solder. The intermetallic compounds formed in the solder/Cu joint were $Cu_{5}Zn_{8}$ and $Cu_{6}Sn_{5}$. After aging treatment, voids formed irregularly at the bottom side of the solder because of Sn diffusion into the $Cu_{5}Zn_{8}$ IMC. In the case of the solder/ENIG joint, $AuZn_{3}$ IMCs were formed at the interface. In the case of the Sn-9Zn/ENIG, the shear strength remained nearly constant in spite of aging for 1000 hours at $150^{\circ}C$. On the other hand, in the case of the Sn-9Zn/Cu, the shear strength significantly decreased after aging at $150^{\circ}C$ for 100hours and then remained constant by further prolonged aging. Therefore, the protective plating layer such as ENIG must be used to ensure the mechanical reliability of the Sn-9Zn/Cu joint.

• 한국세라믹학회지
• /
• 제28권3호
• /
• pp.215-224
• /
• 1991

The synthesis of SrTiO3 powders having high purity and homogeneous submicron particle size was attempted by the oxalate method. The microstructure and dielectric properties of SrTiO3 based boundary layer capacitor (BLC) were investigated. Strontium titanyl oxalate[SrTiO(C2O4)2.4H2O] was prepared from the mixing solution of (Sr, Ti) using oxalic acid(H2C2O4) as a precipitating agent at 8$0^{\circ}C$. The crystalline SrTiO3 powder was obtained by thermal decomposition of the precipitate above $600^{\circ}C$. The crystalline SrTiO3 powder containing Nb2O5 as a dopant, TiO2 and SiO2 as additives was sintered at 1360~144$0^{\circ}C$ in the reducing atmosphere to get semiconductive SrTiO3. Insulating material containing PbO-Bi2O3-B2O3 frit was printed on the sintered semiconductive SrTiO3 and fired at 120$0^{\circ}C$ for 2h to get the grain boundary diffusion.

• 한국재료학회지
• /
• 제32권6호
• /
• pp.307-312
• /
• 2022

Metal halide perovskite (MHP) nanocrystals (NCs) have emerged as promising materials for various optoelectronic applications including photovoltaics, light-emitting devices, and photodetectors because of their high absorption coefficient, high diffusion length, and photoluminescence quantum yield. However, understanding the morphological evolution of the MHP NCs as well as their controlled assembly into optoelectronic devices is still challenging and will require further investigation of the colloidal chemistry. In this study, we found that the amount of n-octylamine (the capping agent) plays a crucial role in inducing further growth of the MHP NCs into one-dimensional nanowires during the aging process. In addition, we demonstrate that the dielectrophoresis process can permit self-alignment of the MHP nanowires with uniform distribution and orientation on interdigitated electrodes. A strong light-matter interaction in the MHP NWs array was observed under UV illumination, indicating the photo-induced activation of their luminescence and electrical current in the self-aligned MHP nanowire arrays.