Daegu Technopark Nano Convergence Practical Application Center

Daegu, South Korea

Daegu Technopark Nano Convergence Practical Application Center

Daegu, South Korea
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Jin Y.-J.,Kyungpook National University | Kim B.S.-I.,Kyungpook National University | Lee W.-E.,Korea Research Institute of Chemical Technology | Lee C.-L.,Gwangju Institute of Science and Technology | And 4 more authors.
NPG Asia Materials | Year: 2014

Highly advanced phase-change hybrids (PCHs), which consist of a phase-change material and conjugated polymer, were developed for new sensor and actuator applications. PCH films with excellent characteristics were obtained simply by depositing various molten paraffin waxes (PWs) in situ onto poly(diphenylacetylene) (PDPA) films with extremely large fractional free volumes. The phase-change enthalpy of the PWs in the hybrid films was quite high and remained constant over prolonged use. The PCH films underwent critical changes in both fluorescence (FL) intensity and color during the phase change of the PWs, which facilitated various sensor applications such as highly reversible writing/erasing, fingerprinting and array-type thermometer usage. In addition, a biaxially oriented polypropylene (BOPP)-supported PCH film exhibited extremely fast and highly reproducible thermomechanical actuation with reversible curling/uncurling during the phase change of the PWs. These findings will be useful for developing novel PCH materials with highly advanced functions and applications. © 2014 Nature Publishing Group All rights reserved.

Park K.M.,Kyungpook National University | Lee M.B.,Daegu Technopark Nano Convergence Practical Application Center | Shin J.W.,Korea University | Choi S.Y.,Kyungpook National University
Solar Energy | Year: 2013

Maskless, random RIE texturing with a gas mixture of SF6/O2 (SO) and SF6/O2/Cl2 (SOC) was investigated to achieve higher efficiency for mc-Si solar cells. Cone structure with aspect ratio of 3.7 was highly effective for reducing surface reflectance particularly for wavelength from 310 to 700nm and triangular pyramid structure with aspect ratio of 2 revealed rather uniform reduction of reflectance with respect to the optimized wet texturing for whole wavelength range of 310-1100nm. On the contrary to results of reflectance, performances of fabricated cell were much better for triangular pyramid structure than cone structure. The degradation of cell performances for the cone structure was assigned both to the poor e-h pair generation efficiency relevant to the formation of highly defective surface layer with high density recombination centers, and ohmic shunt. The efficiency enhancement by 0.6% in mc-Si solar cells with triangular pyramid structures was assigned also to the slightly enhanced e-h pair generation efficiency with respect to the reference cell. © 2013 Elsevier Ltd.

Kim H.,Kyungpook National University | Kim H.,Daegu Technopark Nano Convergence Practical Application Center | Lee D.,Daegu Technopark Nano Convergence Practical Application Center | Lee S.,Kyungpook National University | And 4 more authors.
Macromolecular Rapid Communications | Year: 2013

Disubstituted acetylene monomers [1,2-diphenylacetylenes (DPAs: DPA-pC1, DPA-mC1, DPA-pC8); 1-phenyl-2-hexylacetylene (PHA-pC1)] are tested for asymmetric polymerization in chiral monoterpenes used as solvents and compared with the corresponding monosubstituted acetylene monomer [1-phenylacetylene (PA-pC1)]. DPA-pC1 containing a trimethylsilyl group in the para-position of the phenyl ring produces an optically active polymer with a large Cotton effect, despite the absence of a stereogenic center. The polymer sample obtained by polymerization in 87% ee (-)-α-pinene shows the strongest CD signal (gCD value at 385 nm: ∼3.2 × 10-3). The Cotton bands of the polymers obtained in (-)- and (+)-α-pinenes show the opposite sign in the CD signals. Theoretical calculations show that only the cis-cisoid model adopts a helical conformation. A time-correlated single photon counting experiment shows that the emission of the chiral polymer originates from a virtually single excited species with a 98% component fraction. This polymer solution does not show any significant decrease in gCD value over a wide temperature range of 20 to 80 °C. No noticeable decrease in the g CD value is detected when the polymer solution is kept at relatively low temperatures for a prolonged period (35 d). In contrast, the other polymers show no CD signal. An optically active conjugated polymer with an asymmetric intramolecular π-stack structure, long-term helical stability, and a long-lived emission single excited species is obtained using solvent chirality transfer polymerization. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Park K.M.,Korea Atomic Energy Research Institute | Lee M.B.,Daegu Technopark Nano Convergence Practical Application Center | Choi S.Y.,Kyungpook National University
Solar Energy Materials and Solar Cells | Year: 2015

Maskless reactive ion etching (RIE) texturing using a gas mixture of sulfur hexafluoride-oxygen (SF6/O2) and sulfur hexafluoride-oxygen-chlorine (SF6/O2/Cl2) was investigated to reveal the proper shape in surface features for higher efficiency multi-crystalline silicon (mc-Si) solar cells; hence, needle-like and round-top cone (RT cone) shapes were formed by RIE texturing with SF6/O2 gas, and pyramid and inverted pyramid shapes by RIE texturing with SF6/O2/Cl2 gas. RIE-textured mc-Si solar cells were fabricated on these surface features except for an inverted pyramid structure in the industrial production line. Performances of cells with RT cone and pyramid shapes were enhanced, whereas those with a needle-like cone were degraded, compared to the reference cells. Among these cells, those with RT cones represented the highest efficiency at 17.22%. By considering diode characteristics and electroluminescence images of fabricated solar cells, the proper shape for surface features was intimately related to control of the formation of a stable emitter layer as well as the reduction of surface reflectance. © 2014 Elsevier B.V. All rights reserved.

Jang W.G.,Keimyung University | Jeon K.S.,Daegu Technopark Nano Convergence Practical Application Center | Byun H.S.,Keimyung University
Desalination and Water Treatment | Year: 2013

A membrane material based on polyamide-imide (PAI) has received a great attention lately due to its thermal resistance, outstanding mechanical property, and low thermal expansion coefficient. In this study, we have focused on the preparation of porous PAI nanofiber membranes (PNMs) for water treatments. The preparation of PNMs was completed via the electrospinning method using PAI in a mixed solvent of dimethylacetamide and tetrahydrofuran. The resulting PNMs were then thermally treated to improve mechanical properties. These PAI-based membranes were characterized by scanning electron microscope, tensometer (tensile strength and elongation), pore characteristic, contact angle analyzer (contact angle), and dead-end cell device (water flux). We noticed that the pore diameter (1.0-0.3 μm) of PNMs was systematically controlled by simply increasing the number of PNMs layers. As these nanofiber membranes were found to be highly hydrophobic, we also attempted to prepare hydrophilic PNMs with a PAI solution containing 2-4 wt.% of diethylene glycol prior to the electrospinng. Based on contact angle tests, these modified PNMs exhibited very hydrophilic characteristics that could be utilized in water-filtration systems. © 2013 Copyright Balaban Desalination Publications.

Jung J.-H.,Hannam University | Jung S.-H.,Korea Atomic Energy Research Institute | Kim S.-H.,Daegu Technopark Nano Convergence Practical Application Center | Choi S.-H.,Hannam University
Applied Radiation and Isotopes | Year: 2012

Silica-coated gold-silver alloy nanospheres prepared by Stöber's method were irradiated in a nuclear reactor to prepare radioisotope nanospheres for use as radiotracers. The radioisotope nanospheres included two gamma nuclides: (i) Au-198, emitting major photons with 0.412. MeV and (ii) Ag-108, emitting photons with 0.434 and 0.633. MeV. The nanospheres shell and core diameters were 100-112. nm and 20-50. nm, respectively, depending on their preparation. The gamma-emitting nanospheres could be used as tracers in high-temperature petrochemical and refinery processes in which conventional organic radioactive labels will decompose. © 2012 Elsevier Ltd.

Jung J.-H.,Hannam University | Jung S.-H.,Korea Atomic Energy Research Institute | Kim S.-H.,Daegu Technopark Nano Convergence Practical Application Center | Choi S.-H.,Hannam University
Nuclear Engineering and Technology | Year: 2012

Silica-coated Au with Ag, Co, Cu, and Ir bimetallic radioisotope nanoparticles were synthesized by neutron irradiation, after coating SiO 2 onto the bimetallic particles by the sol-gel Stober process. Bimetallic nanoparticles were synthesized by irradiating aqueous bimetallic ions at room temperature. Their shell and core diameters were recorded by TEM to be 100 -112 nm and 20 - 50 nm, respectively. The bimetallic radioisotope nanoparticles' gamma spectra showed that they each contained two gamma-emitting nuclides. The nanoparticles could be used as radiotracers in petrochemical and refinery processes that involve temperatures that would decompose conventional organic radioactive labels.

Kim Y.-J.,Catholic University of Daegu | Ahn C.H.,Daegu Technopark Nano Convergence Practical Application Center | Choi M.O.,Catholic University of Daegu
European Polymer Journal | Year: 2010

Composite nanofibrous membranes were prepared by the electrospinning and the thermal treatment from poly(vinylidene fluoride) (PVDF)-tetramethyl orthosilicate (TMOS) blend solutions. The average diameter of nanofibers was reduced with increasing the concentration of TMOS in the solution due to the decrease of the solution viscosity. The EDX spectra confirmed the presence of TMOS on the external surface of the composite nanofibrous membrane. The porosity of membranes was effectively enhanced by the introduction of electrospinning technique. However, the mechanical properties, thermal stability and hydrophobicity were not markedly amplified. Thus the thermal treatment of the composite membranes was carried out, leading to the enormous enhancement of the mechanical properties and hydrophobicity. In addition, XRD results revealed that the crystal structure of PVDF in the composite membranes transformed from α-phase to β-phase due to the formation of silica particles by the thermal treatment. © 2010 Elsevier Ltd. All rights reserved.

Kim Y.-J.,Catholic University of Daegu | Ahn C.H.,Daegu Technopark Nano Convergence Practical Application Center | Lee M.B.,Daegu Technopark Nano Convergence Practical Application Center | Choi M.-S.,Konkuk University
Materials Chemistry and Physics | Year: 2011

Composite nanofiber membranes were prepared by electrospinning from poly(vinylidene fluoride) (PVDF)-SiO2 blend solutions with different SiO2 contents. The nanofibers in the membranes were stacked in layers to produce fully interconnected pores that resulted in high porosity. The surface roughness of the membranes increased with increasing the SiO2 content, while the average diameter of nanofibers was rarely affected. The mechanical properties of the nanofiber membranes were significantly improved by the use of SiO2. XRD results revealed that electrospun nanofiber membranes contained mainly β-phase crystal structure of PVDF. The crystallinity obtained from the DSC data reduced with the increase of the SiO2 content from 44.9% to 37.1% due to the inhibited crystallization of the polymer by the inorganic particles during the solidification process. These nanofiber membranes exhibited a high electrolyte uptake, which reached to ∼500%. Moreover, the incorporation of SiO2 into the nanofiber membrane improved the ionic conductivity from 1.7 × 10-3 S cm-1 to 4.7 × 10-3 S cm-1 at room temperature. © 2011 Elsevier B.V. All rights reserved.

Yun J.,Korea Institute of Materials Science | Lee S.,Korea Institute of Materials Science | Bae T.-S.,Korea Basic Science Institute | Yun Y.,Daegu Technopark Nano Convergence Practical Application Center | And 2 more authors.
Plasma Processes and Polymers | Year: 2011

This study discloses (i) the chemical and morphological modifications in acrylate hard-coat and bare polyethylene terephthalate polymers occurring in the course of Ar plasma treatments and (ii) the effects of these modifications on the adhesion, barrier performance, and cohesion of silicon oxide coatings deposited on the polymers. It is concluded that the deterioration in these coating properties is dominated by the formation of nanoscopic globular polymer protrusions on the polymer surface as a result of plasma treatment. The protrusions evolve even under very mild plasma conditions in which an ion fluence of less than 1 × 10 16 ions · cm -2 is applied with low-energy ion irradiation of 6 eV. The polymer protrusions dictate the nucleation and subsequent growth of a coating by promoting the development of a three-dimensional granular morphology in the coating. At the initial oxide nucleation stage, the wetting behavior of silicon oxide on the polymer surface in the presence of nanoscopic protrusions is directly limited by the area number density and size of the protrusions. Incomplete wetting of the protrusions with a silicon oxide coating hinders adhesion between the oxide and the polymer surface. The reduction in the contact area between the oxide and the protrusions is identified as the reason that a weak boundary layer forms at the oxide-polymer interface. Furthermore, the formation of nanoscopic defects, predominantly pinholes, is inevitable in the granular coating morphology on the polymer protrusions and weakens the oxide coating's barrier performance and cohesion strength. Variations in the polar surface free energy and chemical composition of the plasma-treated polymer surface are irrelevant to the wetting dynamics whenever the protrusions develop on the polymer surface. The effects of the polar surface free energy and chemical composition are valid only to the extent that the plasma treatment improves the wettability of a polymer surface without protrusion formation. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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