• Journal of Powder Materials
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• v.24 no.4
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• pp.326-331
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• 2017

The structural formation of inorganic nanoparticles dispersed in polymer matrices is a key technology for producing advanced nanocomposites with a unique combination of optical, electrical, and mechanical properties. Barium titanate ($BaTiO_3$) nanoparticles are attractive for increasing the refractive index and dielectric constant of polymer nanocomposites. Current synthesis processes for $BaTiO_3$ nanoparticles require expensive precursors or organic solvents, complicated steps, and long reaction times. In this study, we demonstrate a simple and continuous approach for synthesizing $BaTiO_3$ nanoparticles based on a salt-assisted ultrasonic spray pyrolysis method. This process allows the synthesis of $BaTiO_3$ nanoparticles with diameters of 20-50 nm and a highly crystalline tetragonal structure. The optical properties and photocatalytic activities of the nanoparticles show that they are suitable for use as fillers in various nanocomposites.

• Polymer(Korea)
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• v.26 no.4
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• pp.462-467
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• 2002

Blends of polymethylmethacrylate (PMMA) with polyvinylidenefluoride (PVDF) were prepared by melt mixing and investigated for optical waveguide devices by using hot embossing process. The glass transition temperatures ($T_g$) of the blends were decreased with increasing PVDF contents. However, the crystalline of PMMA/PVDF blends was not appeared by DSC and XRD due to miscibility between PMMA and PVDF. Shear viscosities and refractive indices of the blends were decreased with increasing PVDF contents. Optical transmittances and absorption losses of the blends were improved with increasing PVDF contents. This is due to a decreasing of polarizability of molecules by fluorine molecule in the PVDF.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.362-363
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• 2008

Well-defined o-$LiMnO_2$ cathode materials were synthesized using LiOH and $Mn_3O_4$ starting materials at $1050^{\circ}C$ in an argon flow by quenching method. The synthesized $LiMnO_2$ particles with crystalline phases were identified with X-ray diffraction (XRD, Dmax/1200, Rigaku). XRD results, demonstrated that the compound $LiMnO_2$ can be indexed to a single-phase material having the orthorhombic structure. In this paper, we analyzed the electrochemical performance of $LiMnO_2$/Li using solid polymer electrolyte and liquid electrolyte.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.197-199
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• 2007

Four banana-shaped compounds have beene synthesized introducing ester linking group into mesogenic unit, varying the central core with 1,6-, 1,7-, 2,3-, and 2,7-naphthylene units, and introducing the dodecyloxy group as the terminal flexible unit. All obtained compounds except one with 1,7-naphthylene unit were reversibly thermotropically liquid crystalline. The compound with 1,7-naphthylene unit could not form the mesophase due to its asymmetrical and sharp substitution angle. The compounds with 1,6- and 2,3-naphthylene units showed an antiferroelectric switchable smectic phase, which has been designated B2 phase. Interestingly, the compound with the 2,3-naphthylene unit showed the two mesophases of B2 and nematic phase.

• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.4122-4126
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• 2012

Cellulose-graft-poly (L-lactide) (cellulose-g-PLLA) was successfully prepared via ring-opening polymerization (ROP) by using 4-dimethylaminopyridine (DMAP) as an organic catalyst in an ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl). The structure and morphology of the polymer was characterized by nuclear magnetic resonance (NMR) and transmission electron microscope (TEM). From wide-angle X-ray powder diffraction (WAXD) and degradation test (by acid, alkaline, PBS and enzyme solution), changes in the crystalline structure as a result of degradation was also investigated. The results indicated that materials which have low degree of crystallinity showing higher degradability, however, in acid liquor, enzyme solution, alkaline liquor and PBS system, the degradation rate of the polymer decreased by the above sequence. Moreover, with the further increase of graft degree of this material, its degradation degree decreased.

• Advances in materials Research
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• v.4 no.2
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• pp.113-132
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• 2015

The phenomena of high-voltage polarization and conductivity in oriented vinylidenefluoride and tetrafluoroethylene copolymer films have been investigated. It was shown that under certain electric fields, injection of carriers from the material of electrodes appears The barrier for holes injection in the copolymer was found to be lower than that for electrons. It results in more effective screening of the external field near the anode than near cathode. Electrones, ejected from cathode, creating negative charge by trapping on the surface. It is shown that the electrons injected from cathodes create a negative homocharge on the copolymer surface and then become captured on the surface shallow traps. Their nature has been studied by the x-ray photoelectron spectroscopy. It was shown that these traps may consist of chemical defects in the form of new functional groups formed by reactions of surface macromolecules with sputtered atoms of aluminum. The asymmetric shape of hysteresis curves was explained by the difference in mobility of injected holes and electrons. These factors caused appearance of "non-closed" hysteresis curves for fluorine-containing polymer ferroelectrics. Hysteresis phenomena observed at low electric fields (below coercive ones) are to associate with the behavior of the domains localized in the ordered regions formed during secondary crystallization of copolymers.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.6
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• pp.552-557
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• 2006

Electrical, optical, surface, and structural properties of amorphous indium-zinc-oxide (a-IZO) grown by box cathode sputtering (BCS) were compared with crystalline indium-tin-oxide (c-ITO) anode films grown by conventional DC sputtering (DCS). Although x-ray diffraction plot of BCS-grown IZO film shows amorphous structure, the optical and electrical properties of a-IZO is comparable to those of c-ITO film. In particular, BCS-grown IZO films shows very smooth surface without defects such as pin hole and cracks because most of the energy of the sputtered atoms was confined in high density plasma region in box cathode gun. Furthermore polymer organic light emitting diodes (POLED) with the a-IZO anode film shows better electrical properties than that of POLED with the c-ITO anode film due to high work function and smooth surface of a-IZO. This suggested that BCS-grown a-IZO film is promising anode materials substituting conventional c-ITO anode in OLED and flexible displays.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.232-233
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• 2007

We manufactured Liquid Crystal Polymer (LCP) and (1-x)CaTiO3-xLaAlO3 (CT-LA) ceramic composites and investigated dielectric properties to use as embedded capacitor in printed circuit boards and replace LTCC substrate. The dielectric properties of these composites are varied with volume fraction of CT-LA and ratios of CT/LA. Dielectric constants are in the range of 3~15. In addition, we could get low TCC and High Q value that could not achieve in other ceramic-polymer composites. Especially, in composite with x=0.01 and 30 vol% CT-LA, the dieletric constant and Q-value are 10 and 200, respectively. And more TCC is $-28{\sim}300ppm/^{\circ}C$ in the temperature range of $-55{\sim}125^{\circ}C$. We think that this composites can be used high-Q substrate material like LTCC and embedded temperature compensation capacitor in printed circuit boards.

• Transactions of Materials Processing
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• v.13 no.6 s.70
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• pp.515-521
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• 2004

The shrinkages of injection molded parts are different in molding operational conditions and mold design. It also differs from resins. The shrinkages of injection molded parts fur PBT (polybutylene terephthalate), PC (polycarbonate), and glass reinforced PBT and PC have been studied for various operational conditions of injection molding. The part shrinkage of crystalline polymer, PBT was higher than that of amorphous polymer, PC by about two times. The part shrinkages of both polymers decreased as glass fiber content increases. Higher injection temperature and lower injection pressure resulted in a higher shrinkage in both PBT and PC resins. As mold temperature increases the part shrinkage of PC decreased. However, the part shrinkage of PBT increased as mold temperature increases. The part shrinkages of PBT and PC resins decreased as gate size increases since the pressure delivery is mush easier for a larger gate size. The part shrinkage of flow direction was less than that of the perpendicular direction to the flow for both pure and glass fiber reinforced resins. The part shrinkage at the position close to the gate was less than that of the position far from the gate.

• Korean Journal of Metals and Materials
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• v.47 no.11
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• pp.722-727
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• 2009

The bipolar plates are not only the major part of the polymer electrolyte membrane fuel cell (PEMFC) stack in weight and volume, but also a significant contributor to the stack costs. Stainless steels are considered to be good candidates for bipolar plate materials of the PEMFC due to their low cost, high strength and easy machining, as well as corrosion resistance. In this paper, 316L stainless steel with and without nitrogen ion implantation were tested in simulated PEMFC environments for application as bipolar plates. The results showed that the nitride formed by nitrogen ion implantation contributed the decrease of the interfacial contact resistance without degradation of corrosion property. The combination of excellent properties indicated that nitrogen ion implanted stainless steel could be potential candidate materials as bipolar plates in PEMFC. Current efforts have focused on optimizing the condition of ion implantation.