• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.1-7
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• 2003

We determined the optical constants of organic light emitting material of Alq$_3$ in a spectral range between 1.5 and 6 eV using the physical model introduced by Forouhi and Bloomer［Phys. Rev. B 34, pp. 7018-7026, 1986.］. The initial parameters of $A_i,\;B_i,\;C_i$ of Forouhi-Bloomer dispersion relations were determined from the absorption peaks and widths of absorption spectra of the Alq$_3$ film. The refractive index of substrate, a fused silica, is derived from the Sellmeier equation with the measured transmittance and reflectance spectra. Then, the complex refractive index and thickness of the Alq$_3$ film were calculated by use of a nonlinear least square fitting program with the Forouhi-Bloomer dispersion relation and the measured transmittance and reflectance spectra.

• Journal of Korean Ophthalmic Optics Society
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• v.5 no.2
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• pp.187-192
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• 2000

We prepared $SiO_2-Na_2O-R_mO_n$ thin films based on economics of water glass and investigated optical, mechanical properties of product thin films. Coating sol stabilized with 1 N HCl and 1 N $NH_4OH$, was fabricated by using water glass and calcium nitrate, and aluminum nitrate as starting materials. As-coated films on stainless steel, Si wafer and soda-lime-silica glass by spinning were finally annealed at 500, 750 and $900^{\circ}C$. Micro hardness and nitrogen content in film surface of annealed films were measured by Knoop hardness tester and EDX, respectively. Field Emission Scanning Electron Microscope (FE-SEM) and UV-VIS spectroscopy were adopted to analyze surface morphology and thickness and reflectance of our films.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.1
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• pp.71-76
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• 2008

Purpose: A simple and efficient method to prepare nanocrystalline ZnO thin film with pure strong UV emission on soda-lime-silica glass substrates by low-temperature annealing was improved. Methods: Crystal structural, surface morphological, and optical characteristics of nanocrystalline ZnO thin films deposited on soda-lime-silica glass substrates by prefiring final annealing process at 300$^{\circ}C$ were investigated by using X-ray diffraction analysis, field emission-scanning electron microscope, scanning probe microscope, ultraviolet-visible-near infrared spectrophotometer, and photoluminescence. Results: Highly c-axis-oriented ZnO films were obtained by prefiring at 300$^{\circ}C$. A high transmittance in the visible spectra range and clear absorption edge in the ultra violet range of the film was observed. The PL spectrum of ZnO thin film with a deep near band edge emission was observed while the defect-related broad green emission was nearly quenched. Conclusions: Our work will be possibly adopted to cheaply and easily fabricate ZnO-based optoelectronic devices at low temperature, below 300$^{\circ}C$, in the future.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.6_2
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• pp.1067-1074
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• 2020

Green houses provide a more conditioned and warmer environment than the outside environment due to insulation. Currently used insulation materials include soft film (PVC, PE, EVA), foamed PE sheet, non-woven fabric, reflective film, and multi-layer insulation curtain, but there are many disadvantages and to compensate for this, silica aerogel insulation material with excellent warmth, light weight, and small volume Research using is in progress. In this study, the temperature change of the quadruple-structure green house and the temperature change in the dual-structure green house of soft film and silica airgel were investigated. The daytime temperature change was highest in A and A2 (soft film) at 10 to 16:00 after sunrise, but showed the lowest temperature at 17 to 18:00, which is the sunset time, showing the greatest change. The airgels of D and D2 showed the smallest change in temperature after sunrise and right after sunset. That is, it can be said that the airgel is hardly affected by external temperature. The temperature change at night was highest in D and D2 (aerogel) for both quadruple and dual structures. The temperature at night was measured higher in the quadruple structure than in the double structure. As for the ratio of the internal temperature to the external temperature for the quadruple structure and the double structure, D (aerogel) was not affected by the external temperature during the day in the quadruple structure and the double structure. D (Aerogel) seems to be able to reduce the damage caused by high temperatures in summer due to the high thermal insulation effect of the airgel, as the temperature rises above 4℃ at night. And in winter, it helps to save heating costs due to less heat emitted to the outside.

• Journal of the Korean Applied Science and Technology
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• v.22 no.3
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• pp.281-288
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• 2005

The silica nanoparticles were used as support of catalyst, filling material, electronic assembler, thin film material, and sensor material. And, the titania nanoparticles were used as pigment, dielectric substance, sensor and photocatalyst. In this paper, the spherical composite particles of $TiO_2/SiO_2$with narrow size distribution and phase pure were synthesized by ultrasonic spray pyrolysis method from $TiOSO_4$ and colloidal silica solution. Using ultrasonic apparatus, this starting solution was vaporized to droplets, and these droplets were induced into tube furnace by carrier gas. The resulting composite powder was characterized by scanning electron microscopy, X-ray diffraction analysis, TG-DTA, in vitro sun protection factor(SPF) and BET surface area analysis.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2193-2198
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• 2011

We prepared polycatenar 1H-imidazole amphiphiles having a structure in which a 1H-imidazole head was connected through a benzene ring to a pheny group having two or three oligo(ethylene glycol) chains and studied their supramolecular assembly by fluorescence spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM). When the aqueous solutions of the amphiphiles ($5{\times}10^{-5}M{\sim}10^{-3}M$) were deposited onto a carbon-coated copper grid and dried, twisted structures with diameters of ~200-300 nm were imaged by TEM and AFM. We presume that the structures comprised a chain of the amphiphile dimers formed via successive hydrogen bonding between the 1H of the imidazole group and 3N of the neighboring one. In a solution of pH 4, entangled fibers with diameters of several nanometers were observed by TEM. In a pH 10 solution, film-like aggregates formed exclusively. The 1H-imidazole amphiphiles hydrolyzed tetraethoxysilane to induce gelation to form fibrous and spherical silica structures at neutral pH in aqueous solutions. No silica was formed when imidazole was used instead of the amphiphiles, suggesting that the selfassembled aggregates of the amphiphiles were responsible for the gelation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.4
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• pp.309-317
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• 2000

Langasite is a promising new piezoelectric material for SAW filter application. Little was known until recently about the methods needed to mechanically polish and chemically polish/etch this material. In this experiment, polishing, slurry chemistry and chemical wet etching for langasite is described. Conventional quartz and LN ($LiNbO_3$) polishing methods did not produce satisfactory polished surfaces, and polishing with a colloidal silica slurries has shown to be most effective. The optimum condition was investigated by changing the slurry chemistry. As the planarization effect is very important in SAW filter applications, the examination of the effective particle number effect and the particle size effect was carried out. Z-cut langasite surface which had been polished with the colloidal silica slurries was etched in a variety of etchants. Conventional quartz etchants destroyed the polished surface. Other etchants formed a thin film on the surfaces. In this experiment, the reaction between langasite and a few etching solution was analysed. And an appropriate selective etchant solution for analyzing the defects was synthesized.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.7
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• pp.568-574
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• 2000

We have been optimized tungsten(W) plug CMP(chemical mechanical polishing) characteristics using two different kinds of component of slurry and two different kinds of pad which have different hardness. The comparison of oxide film roughness on around W plug after polishing has been carried out. And W plug recess for consumable sets and dishing effect at dense area according to the rate of over-polishing has been investigated. Also the analysis of residue on surface after cleaning have been performed. As a experimental result we have concluded that the consumable set of slurry A and hard pad was good for W plug CMP process. After decreasing the rate of chemical reaction of silica slurry and adding two step buffering we could reduce the expanding of W plug void however we are still recognizing to need a more development for those kinds of CMP consumables.

• Journal of the Korean Applied Science and Technology
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• v.16 no.4
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• pp.317-322
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• 1999

Transparent films were prepared using the sol-gel process by mixing TEOS with PVA solution that was solved in EtOH and distilled water homogeneously. HCl, $CH_3COOH$ and $NH_4OH$ were used as catalysts of the sol-gel process, and for improving the flexibility of films glycerol was used as plasticizer. In case of each catalyst, transparency and tensile strength were increased, and glass transition temperature (Tg) was shifted to higher temperature with increasing TEOS ratio. Also, in case of adding the plasticizer, the flexibility of films was increased. On the contrary, transparency, thermal stability and tensile strength were decreased with increasing HCl and $NH_4OH$ ratio. Also, the range of being made of film type was expanded when $CH_3COOH$ was used than HCl and $NH_4OH$.

• Korean Journal of Materials Research
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• v.29 no.2
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• pp.121-128
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• 2019

Supercapacitors are attracting much attention in sensor, military and space applications due to their excellent thermal stability and non-explosion. The ionic liquid is more thermally stable than other electrolytes and can be used as a high temperature electrolyte, but it is not easy to realize a high temperature energy device because the separator shrinks at high temperature. Here, we report a study on electrochemical supercapacitors using a composite electrolyte film that does not require a separator. The composite electrolyte is composed of thermoplastic polyurethane, ionic liquid and fumed silica nanoparticles, and it acts as a separator as well as an electrolyte. The silica nanoparticles at the optimum mass concentration of 4wt% increase the ionic conductivity of the composite electrolyte and shows a low interfacial resistance. The 5 wt% polyurethane in the composite electrolyte exhibits excellent electrochemical properties. At $175^{\circ}C$, the capacitance of the supercapacitor using our free standing composite electrolyte is 220 F/g, which is 25 times higher than that at room temperature. This study has many potential applications in the electrolyte of next generation energy storage devices.