• Title, Summary, Keyword: polymer modifier

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Improved Photovoltaic Performance of Inverted Polymer Solar Cells using Multi-functional Quantum-dots Monolayer

  • Moon, Byung Joon;Lee, Kyu Seung;Kim, Sang Jin;Shin, Dong Heon;Oh, Yelin;Lee, Sanghyun;Kim, Tae-Wook;Park, Min;Son, Dong Ick;Bae, Sukang
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.400.1-400.1
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    • 2016
  • Interfacial engineering approaches as an efficient strategy for improving the power conversion efficiencies (PCEs) of inverted polymer solar cells (iPSCs) has attracted considerable attention. Recently, polymer surface modifiers, such as poly(ethyleneimine) (PEI) and polyethylenimine ethoxylated (PEIE), were introduced to produce low WF electrodes and were reported to have good electron selectivity for inverted polymer solar cells (iPSCs) without an n-type metal oxide layer. To obtain more efficient solar cells, quantum dots (QDs) are used as effective sensitizers across a broad spectral range from visible to near IR. Additionally, they have the ability to efficiently generate multiple excitons from a single photon via a process called carrier multiplication (CM) or multiple exciton generation (MEG). However, in general, it is very difficult to prepare a bilayer structure with an organic layer and a QD interlayer through a solution process, because most solvents can dissolve and destroy the organic layer and QD interlayer. To present a more effective strategy for surpassing the limitations of traditional methods, we studied and fabricated the highly efficient iPSCs with mono-layered QDs as an effective multi-functional layer, to enhance the quantum yield caused by various effects of QDs monolayer. The mono-layered QDs play the multi-functional role as surface modifier, sub-photosensitizer and electron transport layer. Using this effective approach, we achieve the highest conversion efficiency of ~10.3% resulting from improved interfacial properties and efficient charge transfer, which is verified by various analysis tools.

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Electrical and Thermo-mechanical Properties of DGEBA Cycloaliphatic Diamine Nano PA and SiO2 Composites

  • Trnka, Pavel;Mentlik, Vaclav;Harvanek, Lukas;Hornak, Jaroslav;Matejka, Libor
    • Journal of Electrical Engineering and Technology
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    • v.13 no.6
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    • pp.2425-2433
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    • 2018
  • This study investigates a new organic based material and its dielectric and mechanical properties. It is a comprehensive nanocomposite comprising a combination of various types of nanofillers with hydrophobic silica nanoparticles (AEROSIL R 974) as a matrix modifier and a polyamide nano nonwoven textile, Ultramid-Polyamide 6, pulped in the electrostatic field as a dielectric barrier. The polymer matrix is an epoxy network based on diglycidyl ether of bisphenol A (DGEBA) and cycloaliphatic diamine (Laromine C260). The designed nanocomposite material is an alternative to the conventional three-component composites containing fiberglass and mica with properties that exceed current electroinsulating systems (volume resistivity on the order of $10^{16}{\Omega}{\cdot}m$, dissipation factor tan ${\delta}=4.7{\cdot}10^{-3}$, dielectric strength 39 kV/mm).

Surface Modification by Heat-treatment of Propellant Waste Impregnated ACF

  • Yoon, Keun-Sig;Pyo, Dae-Ung;Lee, Young-Seak;Ryu, Seung-Kon;Yang, Xiao Ping
    • Carbon letters
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    • v.11 no.2
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    • pp.131-136
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    • 2010
  • Propellant waste was impregnated on the surface of activated carbon fiber and heat-treated at different temperature to introduce newly developed functional groups on the ACF surface. Functional groups of nitrogen and oxygen such as pyridine, pyridone, pyrrol, lacton and carboxyl were newly introduced on the surface of modified activated carbon fiber. The porosity, specific surface area, and morphology of those modified ACFs were changed as increasing the heat-treated temperature from 200 to $500^{\circ}C$. The optimum heat-treatment temperature was suggested to $500^{\circ}C$, because lower temperature given rise to the decrease of specific surface area and higher temperature resulted in the decrease of weight loss. Propellant waste can be used as an useful surface modifier to porous carbons.

Evaluation of Permanent Deformation Characteristics of Recycled Asphalt Concretes Made by Improved Binder-Rejuvenation (바인더 회생방식을 개선한 재생 아스팔트 콘크리트의 소성변형 특성 연구)

  • Kim Kwang-Woo;Kweon Oh-Sun;Doh Young-Soo
    • International Journal of Highway Engineering
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    • v.8 no.1
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    • pp.1-13
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    • 2006
  • This paper is one of the studies for developing new methodologies for improving performance of hot-mix recycled asphalt mixtures. The objective of this study is to evaluate rut-resistance characteristics of recycled asphalt mixture which was prepared by newly developed mixing method. The new mixing method provided more sufficient rejuvenation of old binder of reclaimed asphalt pavement (RAP), making homogeneous binder viscosity level in a recycled mixture. Two aggregates (gneiss and granite), two RAP contents (15% and 30%) and two contents (none and 6%) of polymer modifier (LDPE) were used. Recycled mixture was prepared with two methods; method A and method F. To examine difference of binder oxidation level by type of material within a recycled mixture, Gel-permeation chromatography(GPC) analysis was performed on the binders mixed with coarse aggregates and matrix separately. Laboratory tests were performed for evaluation of rut resistance characteristics of each recycled mixture and these includes wheel tracking (WT) test and Kim test. Rut depth and dynamic stability were obtained from WT test and deformation strength $(S_D)$ was obtained from Kim test. The results of regression analysis was shown that correlation $(R^2)$ of F mixing mixtures was higher than one of A mixing mixtures. Therefore, F mixing mixtures showed more consistent rut resistance than h mixing mixtures.

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Preparation and Mechanical Properties of PMMA Panels (PMMA 판재의 제조 및 기계적 특성)

  • 길기승;김의식;김대수
    • Polymer Korea
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    • v.27 no.2
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    • pp.142-151
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    • 2003
  • PMMA panels are made by two fabrication methods; cell molding and belt molding processes. But these methods have disadvantages in productivity and cost. So plastic processing engineers are very interested in developing a new production method for PMU panels using plastic films as molds because the new method can reduce production cost of belt molding method as well as can improve productivity of cell molding method. To give a solution for developing such a new molding method, the effects of melthyl methacrylate compound composition and curing reaction condition on the processability and mechanical strength of PMMA panels were investigated in this study. Poly(vinyl acetate) film was used as molds in producing PMMA panels. To determine an MMA compound showing good processability and good mechanical properties after curing, ingredients and their compositions were optimized step by step. Acrylic acid, as a coupling agent and a modifier, played an important role in increasing mechanical strength of PMMA panels.

Carrier Transport of Quantum Dot LED with Low-Work Function PEIE Polymer

  • Lee, Kyu Seung;Son, Dong Ick;Son, Suyeon;Shin, Dong Heon;Bae, Sukang;Choi, Won Kook
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.432.2-432.2
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    • 2014
  • Recently, colloidal core/shell type quantum dots lighting-emitting diodes (QDLEDs) have been extensively studied and developed for the future of optoelectronic applications. In the work, we fabricate an inverted CdSe/ZnS quantum dot (QD) based light-emitting diodes (QDLED)[1]. In order to reduce work function of indium tin oxide (ITO) electrode for inverted structure, a very thin (<10 nm) polyethylenimine ethoxylated (PEIE) is used as surface modifier[2] instead of conventional metal oxide electron injection layer. The PEIE layer substantially reduces the work function of ITO electrodes which is estimated to be 3.08 eV by ultraviolet photoemission spectroscopy (UPS). From transmission electron microscopy (TEM) study, CdSe/ZnS QDs are uniformly distributed and formed by a monolayer on PEIE layer. In this inverted QD LED, two kinds of hybrid organic materials, [poly (9,9-di-n-octyl-fluorene-alt-benzothiadiazolo)(F8BT) + poly(N,N'-bis (4-butylphenyl)-N,N'-bis(phenyl)benzidine (poly-TPD)] and [4,4'-N,N'-dicarbazole-biphenyl (CBP) + poly-TPD], were adopted as hole transport layer having high highest occupied molecular orbital (HOMO) level for improving hole transport ability. At a low-operating voltage of 8 V, the device emits orange and red spectral radiation with high brightness up to 2450 and 1420 cd/m2, and luminance efficacy of 1.4 cd/A and 0.89 cd/A, respectively, at 7 V applied bias. Also, the carrier transport mechanisms for the QD LEDs are described by using several models to fit the experimental I-V data.

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A Study on Electric Field Dispersion Techniques of Epoxy-Nanocomposites for Application of High Voltage Power Apparatus (고전압 전력기기응용을 위한 에폭시-나노콤포지트의 전기장 분산기술연구)

  • Lee, Chang-Hoon;Kim, Hyo-Chul;Cho, Young-Haw;Kim, Hyun;Jo, Sung-Choe;Park, Jae-Jun
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.97-97
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    • 2010
  • A new electric application method was developed to prepare epoxy/organoclay nanocomposite for the electrical insulation in the AC electric fields and it could be also used in the field of various viscous polymer/organoclay systems. The applied AC electric field condition was as follows; (1) inter-electrode distance: 40 mm, (2) application voltage: 3-11 kV, (3) frequency: 60~1,000 Hz, and (4) application time: 0~60 min. To characterize the epoxy/clay nanocomposite, WAXS and TEM analyses were confirmed. In order to explain how the organic modifier affects the exfoliation phenomena, a mechanism of the oscillating collision of the quaternary ammonium head was proposed and the effects of the AC voltage and frequency and the organoclay content were studied.

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Preparation of Polyolefin Based Segmented Copolymers Through Controlled Radical Polymerization Technique (조절 라디칼 중합법에 의한 폴리올레핀 기반 분절 공중합체의 제조)

  • Hong, Sung-Chul;Lee, Seong-Hoon;Cho, Hyun-Chul
    • Elastomers and Composites
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    • v.44 no.3
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    • pp.209-221
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    • 2009
  • Polyolefins are important commodity polymers with the largest volume of business owing to their outstanding combination of cost performance and excellent physical properties. However, the lack of functional groups often has limited their end uses, such as compatibilizer, modifier and adhesive, where the interaction with other materials is especially important. The incorporation of functional groups as polymer segments to afford block or graft polyolefin copolymers has been extensively investigated in the context of the functional polyolefin hybrids. Living polymerization processes have been considered to be an efficient method to prepare the polyolefin hybrids with precisely controlled architecture and compositions. Among the living polymerization techniques, controlled/"living" radical polymerization (CRP) methods are very effective not only because of the controllability of polymerization but also because of the versatility of monomers and polymerization conditions. In this review paper, progresses on the preparations of polyolefin graft or block copolymers through CRP techniques are summarized. The commodity polymers such as polyisobutylene, polyethylene and polypropylene are combined with polar segments such as polyacrylate, polymethacrylate, polystyrene to yield functionalized polyolefins.

Impact Modification Effects of SEBS-g-MA on Polyamide 6/Maleated Polypropylene Blends (폴리아미드6/반응성 포리프로필렌 블렌드계에서 SEBS-g-MA의 충격개선효과)

  • Koh, Jae Song;Yoon, Tae Sung;Jung, In Kwon;Choi, Hyeong Ki;Jang, Yoon Ho
    • Applied Chemistry for Engineering
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    • v.10 no.8
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    • pp.1141-1146
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    • 1999
  • Melt blend of PA6/PP-g-MA system containing SEBS-g-MA as a compatible impact modifier was prepared to investigate the change of mechanical properties and morphologies. The tensile strength slightly decreased, but the elongation at break increased with increasing content of SEBS-g-MA in the blend. Also the notched izod impact strength increased with increasing the content of PP-g-MA and SEBS-g-MA. It is attributed to improved compatibilization and interfacial adhesion by reaction of the amide of PA6 with maleic anhydride of SEBS-g-MA and PP-g-MA. The result of dynamic mechanical analysis(DMA) showed a typical behavior of the compatibilization in the polymer blends. Finally, in the phase structure observed by the use of SEM, we confirmed improvement of the compatibilization and interfacial adhesion with increasing the content of SEBS-g-MA and PP-g-MA.

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A Study on the Fabrication of Hollow Glass Sphere by Using a Liquid-mix Precursor (혼합액상 전구체를 이용한 유리 중공구체의 제조에 관한 연구)

  • Lee, Yong Bin;Kim, Ki Do;Kim, Hee Taik
    • Applied Chemistry for Engineering
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    • v.10 no.8
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    • pp.1186-1191
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    • 1999
  • By using a liquid-mix precursor, we prepared the hollow glass spheres(HGS) as an additive of polymer compound which are used in the field of modifier, promoter, filler, and reinforcement. Liquid-mix precursor is a mixture of 40% sodium silicate aqueous solution, boric acid as a insolubilizing agent, and urea as a blowing agent. To obtain the precursor particles which are fed into a gas flame furnae, the above liquid-mix precursor was dried in oven and crushed with ball mill. We assumed the size of precursor particles ($53{\sim}63{\mu}m$, $63{\sim}180{\mu}m$), temperature of furnace($800{\sim}1200^{\circ}C$), and amount of urea(0~30 g) as the parameters affecting on the properties of HGS. As a result mean particle size of HGS increases with increasing the temperature of furnace and the amount of urea and with decreasing the size of precursor particles. Also, we found that incresing the amount of urea is related to a decrease of the crush strength of HGS.

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