• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.189-189
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• 2012

Lead sulfide (PbS) nanocrystal quantum dots (NQDs) are promising materials for various optoelectronic devices, especially solar cells, because of their tunability of the optical band-gap controlled by adjusting the diameter of NQDs. PbS is a IV-VI semiconductor enabling infrared-absorption and it can be synthesized using solution process methods. A wide choice of the diameter of PbS NQDs is also a benefit to achieve the quantum confinement regime due to its large Bohr exciton radius (20 nm). To exploit these desirable properties, many research groups have intensively studied to apply for the photovoltaic devices. There are several essential requirements to fabricate the efficient NQDs-based solar cell. First of all, highly confined PbS QDs should be synthesized resulting in a narrow peak with a small full width-half maximum value at the first exciton transition observed in UV-Vis absorbance and photoluminescence spectra. In other words, the size-uniformity of NQDs ought to secure under 5%. Second, PbS NQDs should be assembled carefully in order to enhance the electronic coupling between adjacent NQDs by controlling the inter-QDs distance. Finally, appropriate structure for the photovoltaic device is the key issue to extract the photo-generated carriers from light-absorbing layer in solar cell. In this step, workfunction and Fermi energy difference could be precisely considered for Schottky and hetero junction device, respectively. In this presentation, we introduce the strategy to obtain high performance solar cell fabricated using PbS NQDs below the size of the Bohr radius. The PbS NQDs with various diameters were synthesized using methods established by Hines with a few modifications. PbS NQDs solids were assembled using layer-by-layer spin-coating method. Subsequent ligand-exchange was carried out using 1,2-ethanedithiol (EDT) to reduce inter-NQDs distance. Finally, Schottky junction solar cells were fabricated on ITO-coated glass and 150 nm-thick Al was deposited on the top of PbS NQDs solids as a top electrode using thermal evaporation technique. To evaluate the solar cell performance, current-voltage (I-V) measurement were performed under AM 1.5G solar spectrum at 1 sun intensity. As a result, we could achieve the power conversion efficiency of 3.33% at Schottky junction solar cell. This result indicates that high performance solar cell is successfully fabricated by optimizing the all steps as mentioned above in this work.

• 한국결정성장학회지
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• 제23권5호
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• pp.230-234
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• 2013

ATO 나노 입자들로 구성된 적외선 차단 박막이 솔-젤 법에 의해 성공적으로 제조되었다. 코팅액은 유무기 하이브리드 바인더와 콜로이드 ATO 용액으로 합성되었고 ATO 박막은 슬라이드 유리기판에 5~40 mm/s의 인상속도로 코팅되었다. 인상속도가 5 mm/s에서 40 mm/s로 증가함에 따라 코팅막의 두께 또한 $1.05{\mu}m$에서 $4.25{\mu}m$로 증가하였다. 그리고 파장 780 nm에서 2500 nm에서의 적외선 차단율은 49.5 %에서 66.7 %로 증가하였다. 또한 $80^{\circ}C$에서 건조된 ATO 박막의 연필경도 값은 5H를 나타내었고 tetraethylorthosilicate와 methyltrimethoxysilane을 합성한 하이브리드 바인더의 영향으로 테이프테스트 후 코팅막은 벗겨지지 않았다. 서로 다른 인상속도에 의해 제조된 박막의 표면구조, 광학적 특성 그리고 박막두께는 FE-SEM, UV-Vis-NIR 분광기 그리고 Dektak에 의해 측정되었다.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제4권3호
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• pp.173-183
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• 2000

This study measured the zeta potential of both latex colloidal particles with carboxylate surface groups and glass beads (collectors) with silanol surface group employing various solution with different chemical characteristics. The results have been compared with the surface chemistry theory. The zeta potential of the particle and collector increased with increasing pH up to 5.0 regardless of the solution chemistry. For a monovalent electrolyte solution(sodium chloride solution) the zeta potential steadily increased until the pH reached 9.5. In contrast, little change in zeta potential was made between 5.0 and 9.5 for a divalent electrolyte solution (sodium chloride solution) the zeta potential steadily increased until the pH reached 9.5. In contrast, little change in zeta potential was made between 5.0 and 9.5 for a divalent electrolyte solution (calcium chloride solution). In other words, the more the pH decreases, the larger the effect of neutral salts, such as NaCl and CaCl$_2$, have on the ζ-potential values. In this study, the PZPC(point of zero proton condition) of the particle and collector occurred below a pH of 3.1, H(sup)+ and OH(sup)- acted as a PDI (potential determining ion), and Na(sup)+ acted as an IDI(indifferent ion). The magnitude of the negative ζ-potential values of the particle and collector monotonically increased as the concentrations of Na(sup)+ or Ca(sup)2+([Na(sup)+] or [Ca(sup)2+]) decreased (the values of pNa or pCa increased). In the case of latex particles, the ζ-potential should aproach zero (isoelectric point; IEP) asymptotically as the pNa approaches zero, while in the case of calcium chloride electrolyte, ζ-potential reversal may be expected to occur around 3.16$\times$10(sup)-2MCaCl$_2$(pCa=1.5). pH, valance and ionic strength can be used in various ways to improve the water treatment efficiency by modifying the charge characteristics of the particle and collector. Predictive capability is far less certain when EDL(electrical double layer) repulsive forces exist between the particle and collector.

• 한국지반환경공학회 논문집
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• 제19권5호
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• pp.5-12
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• 2018

본 연구에서는 연소재와 식품폐기물의 산업부산물을 이용하여 비점오염 수처리 여과재로 활용 가능한 여과재를 개발하였다. 첨가제 주입에 따른 공극 형성은 강도가 유지되는 전제하에 알루미늄 파우더 3%, $Ca(OH)_2$ 2%일 경우 기포형성이 가장 많이 발생하는 것으로 나타났다. 결합재의 적정 혼합비로서 (연소재+식품 폐기물+점토):(물유리+콜로이드성 실리카)는 7:3 이상에서 가장 효과적인 것으로 나타났으며, 온도에 따른 강도반응은 $1,000^{\circ}C$일 경우가 효과적이다. 최적의 혼합비율은 연소재 30%, 점토 30%, 식품 폐기물 10%에서 가장 높은 강도를 보여 비점오염 수처리로 활용도가 가장 높을 것이라 판단된다. 최적 배합조건에서 제조된 여과재는 $SiO_2$ 65.8%, 밀도 $1.4g/cm^3$, 공극률 25.6%, pH 9.8로 분석되었으며, 유해물질은 검출되지 않았다. 수처리에 대한 여과능을 알아본 결과 여과된 SS의 평균농도는 $14.06mg/{\ell}$로서 SS의 제거효율은 90.63%로 나타났으며, 역세척 회복률도 97.1%로 나타났다. 이는 폐자원의 활용뿐만 아니라 경제성 및 효율성을 고려한 수처리 여과재 제조가 가능함에 따라 폐자원의 높은 부가가치화가 가능하다.

• The Journal of Advanced Prosthodontics
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• 제11권1호
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• pp.7-15
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• 2019

PURPOSE. The aim of this study was to identify the effects of three aesthetic restorative materials on the wear between tooth and restoration by a pin-on-disk manner. MATERIALS AND METHODS. Six aesthetic restorative materials were used to prepare disk specimens for wear test, which were Lava Zirconia as zirconia group, Vintage MP and Cerabien ZR as veneering porcelain group, Gradia Direct microhybrid composite containing prepolymerized fillers, Filtek Z250 microhybrid composite containing zirconia glass and colloidal silica particles, and Filtek Z350 nanocomposite as composite resin group. Vertical loss of the worn cusp, change of the surface roughness of the restoration materials, and the surface topography were investigated after wear test under 9.8-N contact load. RESULTS. The porcelain groups (Vintage MP and Cerabien ZR) caused the largest vertical loss of teeth when compared with those of the composite resin and zirconia groups, and Filtek Z250 microhybrid composite results in the second-largest vertical loss of teeth. The surface of Filtek Z350 nanocomposite was deeply worn out, but visible wear on the surface of the zirconia and Gradia Direct microhybrid composite was not observed. When the zirconia surface was roughened by sand-blasting, vertical loss of teeth considerably increased when compared with that in the case of fine polished zirconia. CONCLUSION. It was identified that microhybrid composite resin containing a prepolymerized filler and zirconia with reduced surface roughness by polishing were the most desirable restorative materials among the tested materials to prevent the two-body wear between aesthetic restorative material and tooth.