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Lee S.-W.,Seoul National University | Park J.-W.,Seoul National University | Kwon Y.-E.,Seoul National University | Kim S.,Seoul National University | And 4 more authors.
International Journal of Adhesion and Adhesives | Year: 2012

Acrylic pressure-sensitive adhesives (PSAs) with different side-chain lengths in the co-monomer were synthesized. This study employed semi-interpenetrated structured polymer networks using UV-curing with a hexafunctional monomer, dipentaerythritol hexacrylate (DPHA). The optical properties of the acrylic PSAs were examined by UV-visible spectroscopy and a prism coupler. ARES was used to characterize the viscoelastic properties of the acrylic PSAs. Adhesion performance was conducted by the peel strength and probe tack tests. Also UV-curing behavior of the acrylic PSAs was investigated by FTIR. © 2012 Published by Elsevier Ltd. All rights reserved.

Jeong S.,Daegu Gyeongbuk Institute of Science and Technology | Han Y.S.,Daegu Gyeongbuk Institute of Science and Technology | Kwon Y.,Daegu University | Choi M.-S.,Konkuk University | And 3 more authors.
Synthetic Metals | Year: 2010

The synthesized n-type perylene derivative, N,N′-bis-(5- bromopyridine-2-yl)-1,6,7,12-tetrakis(4-n-butoxyphenoxy)-3,4,9,10-perylene tetracarboxydiimide (PPyB), was applied to polymer solar cells as an additive in P3HT [poly(3-hexylthiophene)]:PCBM [[6,6]-phenyl C61-butyric acid methyl ester] blend films. The addition of 1 wt% PPyB into a P3HT:PCBM layer led to a considerable improvement of over 70% in power conversion efficiency due to the enhanced short circuit current when compared with that of reference cell without an additive. Photoluminescence, X-ray measurements and carrier mobility studies revealed that the perylene additives increased electron mobility and contributed to more effective exciton dissociation due to the presence of the additive, PPyB, in the interfaces between the P3HT and PCBM domains. © 2010 Elsevier B.V. All rights reserved.

Lee S.-W.,Seoul National University | Park J.-W.,Seoul National University | Park C.-H.,Seoul National University | Kim H.-J.,Seoul National University | And 2 more authors.
International Journal of Adhesion and Adhesives | Year: 2013

Optically clear acrylic pressure-sensitive adhesives (PSAs) with different co-monomers were synthesized. This study employed metal chelate aluminum acetylacetonate and zirconium acetylacetonate as curing agents. The optical properties of the acrylic PSAs were examined by UV-visible spectroscopy and a prism coupler. In addition, the adhesion performance was obtained by assessing the peel strength, the tack, and the shear adhesion failure temperature. The decrease in the adhesion performance may be related to a higher crosslinking density, which also resulted in a higher gel content. © 2013 Elsevier Ltd.

Park B.C.,University of Ulsan | Hong I.K.,University of Ulsan | Jang H.D.,University of Ulsan | Tran V.D.N.,University of Ulsan | And 2 more authors.
Materials Letters | Year: 2010

Effects of Cu doping on the ferroelectric and piezoelectric properties of 0.0038 mol K5.4Cu1.3Ta10O29 modified (K0.5Na0.5)NbO3 ceramics have been investigated. On the basis of analyses on crystal structure and polarization hysteresis, it is suggested that Cu ions reveal amphoteric doping behavior in KNN ceramics. At doping levels up to 1 mol%, the Cu ions substitute pentavalent B-site cations, acting as acceptors that generate O-vacancies to resultantly harden the ceramics. At doping levels above 1.5 mol%, however, Cu ions play a role as donors by replacing monovalent A-site cations. A specimen doped with 0.5 mol% CuO shows an extremely high mechanical quality factor of 3053, which is higher than those of any other reports on KNN-based ceramics. © 2010 Elsevier B.V. All rights reserved.

Jeong M.,University of Ulsan | Lee Y.M.,Ulsan Fine Chemical Industry Center | Hong S.H.,University of Ulsan | Park S.Y.,Chungbuk National University | And 2 more authors.
Biotechnology Letters | Year: 2010

Methyl (R)-2-chloromandelate, a key intermediate in the synthesis of clopidogrel, was obtained by the reduction of methyl-2-chlorobenzoylformate using whole cells of Saccharomyces cerevisiae. A 100% conversion and 96.1% of enantiomeric excess (ee) value was obtained when 17 methyl-2-chlorobenzoylformate/l was reacted with 8 g S. cerevisiae/l and 83g glucose/l at pH 7. © 2010 Springer Science+Business Media B.V.

Do N.B.,University of Ulsan | Jang H.D.,University of Ulsan | Hong I.,University of Ulsan | Han H.S.,University of Ulsan | And 3 more authors.
Ceramics International | Year: 2012

Effect of excess CuO additive on the sintering behavior and piezoelectric properties of Bi 0.5(Na 82K 0.18) 0.5TiO 3 ceramics was investigated. The addition of small amount of excess CuO as low as 1 mol% was quite effective to lower the sintering temperature (T s) of BNKT ceramics down to 975°C while their piezoelectric properties were degraded by Cu doping. However, the electric field-induced strain was markedly enhanced by further addition of Nb 2O 5 with CuO without elevating T s. The normalized strain S max/E max of 427 pm/V was obtained with a specimen sintered with 0.02 mol CuO and 0.03 mol Nb 2O 5 in excess. © 2011 Elsevier Ltd and Techna Group S.r.l.

Han H.-S.,University of Ulsan | Jo W.,TU Darmstadt | Rodel J.,TU Darmstadt | Hong I.-K.,Ulsan Fine Chemical Industry Center | And 2 more authors.
Journal of Physics Condensed Matter | Year: 2012

The effect of LaFeO 3 addition to Bi 1/2(Na 0.78K 0.22) 1/2TiO 3 ceramics on the phase stability and macroscopic functional properties was investigated. Similarly to other chemical modifiers known in the literature, LaFeO 3 addition suppresses an electric-field-induced long-range ferroelectric order, giving rise to a giant unipolar strain of 0.3% at 2mol% LaFeO 3 addition. Time-dependent changes in polarization and strain hysteresis loops both during successive electrical cycling and after removal of the electric field suggest that a specimen with 2mol% LaFeO 3 consists of both ergodic and nonergodic phases, which is unique among the known relaxor materials. © 2012 IOP Publishing Ltd.

Do N.B.,University of Ulsan | Lee H.-B.,University of Ulsan | Le D.T.,University of Ulsan | Jeong S.-K.,University of Ulsan | And 3 more authors.
Current Applied Physics | Year: 2011

The phase diagram of ternary (1-x-y) Bi 0.5Na 0.5TiO 3-x Bi 0.5K 0.5TiO 3-yLiTaO 3 (BNT-BKT-LT) ceramics was investigated within the range of x = 0-0.4 and y = 0-0.1 via analyses on their crystal structure, dielectric and field-induced strain properties. BNT-rich compositions revealed ferroelectric rhombohedral symmetry (FE R: x < 0.18 and y < 0.04) while BKT modified BNT ceramics transformed into ferroelectric tetragonal symmetry (FE T; x > 0.18 and y < 0.02). However, LT modification of BNT-BKT ceramics induced a phase transition to nonpolar pseudocubic symmetry (NP PC; x = 0-0.4 and y > 0.04). At phase boundaries between these three regions, the coexistence of two or three phases was observed. Interestingly, the electric field-induced strain was markedly enhanced at the ferroelectric-nonpolar phase boundary. © 2011 Elsevier B.V. All rights reserved.

Kim J.C.,University of Ulsan | Shin C.H.,University of Ulsan | Jeong C.W.,University of Ulsan | Kwon Y.J.,University of Ulsan | And 2 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2010

Transparent conducting ITO/Ni/ITO films were deposited by RF magnetron sputtering of Sn-doped In2O3 and DC magnetron sputtering of Ni on unheated polycarbonate substrates. Ni interlayers with thicknesses of 5, 10, and 20 nm were used as intermediate metallic layers. Changes in the work function and optical, electrical and structural properties of the films were examined with respect to Ni layer thickness. The work function was measured to be about 4.5 eV and was found to be independent of Ni layer thickness. However, the structural, optical, and electrical properties of the films were influenced by the Ni thickness. As-deposited ITO single layer films showed In2O3 diffraction peaks for the (2 2 2) and (4 0 0) planes, while after insertion of the Ni layer between ITO films, these diffraction peaks disappeared. The electrical resistivity decreased with the Ni intermediated film and the optical transmittance also decreased due to increased optical absorption. The figure of merit reached a maximum of 2.0 × 10-3 Ω-1 for a 5 nm-thick inserted Ni film, which is greater than the value for as-deposited ITO films. © 2009.

Binh D.N.,University of Ulsan | Hussain A.,University of Ulsan | Lee H.-D.,University of Ulsan | Kim I.-W.,University of Ulsan | And 2 more authors.
Journal of the Korean Physical Society | Year: 2010

The effects of Y doping on the crystal structure, and on the ferroelectric and the piezoelectric properties of Bi0.5(Na0.82K0.18)0.5TiO3 ceramics have been investigated. The Y doping induced a transition from a ferroelectric (FE) tetragonal to an electrostrcitive (ES) pseudocubic phase, leading to the degradations of the dielectric constant, loss tangent, the remnant polarization, coercive field, and piezoelectric coefficient d33. However, the electric-field-induced strain was significantly enhanced by the Y-doping-induced phase transition and reached the highest value of Smax/Emax = 278 pm/V when 0.7 wt% Y2O3 was doped. The abnormal enhancement in strain was attributed to the coexistence of FE and ES phases, which provided more degrees of freedom for domain reorientation under electric fields.

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