• Journal of Powder Materials
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• v.17 no.5
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• pp.409-414
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• 2010

Titanium dioxide ($TiO_2$), which is one of the most basic materials in our daily life, plays a key role for environment purification. We synthesized $TiO_2$ nanoparticles by the hydrolysis reactions of titanium tetraisopropoxide using $HNO_3$ as a peptizing agent or $CH_3COOH$ as a chelating agent in the sol-gel method. The powder consisted of a rod shape or a spherical shape according to the concentration and kind of acid. The physical properties of $TiO_2$ nanoparticles were investigated with X-ray diffraction, SEM, BET analysis, and UV-Vis spectrophotometer.

• Transactions on Electrical and Electronic Materials
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• v.11 no.4
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• pp.178-181
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• 2010

An automotive IC voltage regulator which consists of one-chip based on a metal-oxide semiconductor field effect transistor (MOSFET) is investigated experimentally with three types of packaging. The closed type is filled with thermal silicone gel and covered with a plastic lid on the MOSFET. The half-closed type is covered with a plastic case but without thermal silicone gel on the MOSFET. Opened type is no lid without thermal silicone gel. In order to simulate the high temperature condition in engine bay, the operating circuit of the MOSFET is constructed and the surrounding temperature is maintained at $100^{\circ}C$. In the overshoot the maximum was mainly found at the half-closed packaging and the magnitude is dependent on the packaging type and the surrounding temperature. Also the impressed current decreased exponentially during the MOSFET operation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.83-86
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• 1998

Ferroelectric PZT(40/67)/PZT(60/40)heterolayered thin films were Prepared by the alkoxide-based Sol-Gel method. PZT(40/60) and PZT(60/40) stock solutions were made and spin-coated on the P7Ti/Si02/Si substrate alternately. These PZT(40/60) and PZT(60/40) films were dried at 300$^{\circ}C$ for 30min to remove organic materials and were sintered at 650$^{\circ}C$ for 1 hour to crystalize into a perovskite structure. The coating and heating procedure were repeated 6 times to form heterolayered films. Increasing the number of coating, coercive field was decreased. The relative dielectric constant, loss, remanent polarization and coercive field of the 4-coated PZT heterolayered were 1200, 4.1[%], 30.794[${\mu}$C/㎡] and 147.22[kV/cm], respectively.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1685-1686
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• 2000

Crack-free and homogeneous com ceramic and epitaxial lead zirconate titanat ferroelectric thin films with perovskite structure been prepared by sol-gel processing. Ti-isoprop and lead acetate trihydrate and zirconium-pro are used raw materials. EAcAc is used as a cat 2-Methoky ethanol is used as a solvent annealing temperatures of the thin films are 0$^{\circ}C$.

• Electrical & Electronic Materials
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• v.7 no.5
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• pp.369-375
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• 1994

In this study, ferroelectric thin films of PZT with different Zr/Ti ratio were prepared by sol-get processing and annealed by rapid thermal annealing at >$500^{\circ}C$>$-700^{\circ}C$ for 10 sec. -1 min. Structures of the annealed films were examined by X-ray diffraction and SEM. Thin films of PZT with perovskite structure have been obtained by annealing at >$600^{\circ}C$ or above and for 20 seconds or longer. Maximum remnant polarization of 10.24.mu.C/cm$^{2}$ and minimum coercive field of 20.06 kV/cm were obtained from the 56/44 and 65/35 Zr/Ti composition films, respectively. Dielectric constant, .epsilon.$_{r}$ of 500-1300 and dielectric loss, tan .delta., of 0.01-0.035 were obtained from the films.s.

• Electrical & Electronic Materials
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• v.10 no.1
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• pp.61-67
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• 1997

We have studied dielectric properties of sol-gel derived tantalum oxide thin films as the insulators. As the sample is annealed from 300.deg. C to 700.deg. C, it is found amorphous below 600.deg. C and crystalline over it. Dielectric constant is maximum(18.6) when Ta$_{2}$O$_{5}$ film was annealed at 400.deg. C. It is found that dielectric strength in Ta$_{2}$O$_{5}$ film annealed at 400.deg. C (1.5MV/cm) increases and then decreases over annealed at 500.deg. C. This phenomenon was attributed to pinhole effect and crystallization. The de conduction properties can be interpreted by Poole-Frenkel effect.ect.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1927-1929
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• 2005

Colloidal Silica(CS)/methyltrimethoxy silane(MTMS) sol solutions were prepared in variation with synthesizing parameters such as kinds of CS, acidity and reaction time. In order to understand its surface properties, sol-gel coating films on glass were fabricated. The coating film obtained from CS/MTMS sol had stable contact angle and more enhanced flat surface at reaction time of 24 hours. In case of the initial and final period of reaction, the coating films had unstable contact angle and more rough surface. In addition, surface of CS/MTMS sol-gel coating film was more rougher with increasing of acidity.

• Bulletin of the Korean Chemical Society
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• v.21 no.8
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• pp.817-822
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• 2000

Crack-free hard coating siIica films were prepared by sol-gel processfrom twokinds of silicon alkoxide (tetra-ethoxysilane and methyltrimethoxysilane) and two kinds of alcohol (methanol and isopropyl alcohol) with an acid catalyst,acetic acid. A silicate framework of the precursor solution was investigated by infrared spectros-copy (IR) in the process of hydrolysis and condensation. Theextent of the condensation in the intermediates was elucidated by gel permeation chromatography (GPC) and 29Si-NMR spectroscopy. The hard coating films werecharacterized by IR,scanning electron microscope (SEM), thermo gravimetric analyzer (TGA) and dif-ferential scanning calroimeter (DSC). The synthetic condition for the crack-free and transparent silica film for-mation was optimized interms of starting materials for the precursor solution as well as preparation method of the silica film.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.44-45
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• 2020

The purpose of this study was to contemplate the effectual waterproofing materials and construction methods for the restoration of underground infrastructures using precast arches(PC-Arch). Until now, there were no proper waterproofing guidelines for waterproofing precast arch tunnel when restoring cultural heritage or building underground infrastructures for noise control. Asphalt membrane sheets were commonly used, but the efficacy of waterproofing done on the precast segment was vulnerable. This study aims to examine the Synthetic Rubber Polymerised Gel(SRPG) proposed in ISO TR 16475, a guideline for the repair of water-leakages, and to demonstrate field applicability based on the waterproofing solution used on the road improvement project in front of Changgyeonggung Palace in Yulgok-ro, Seoul, Republic of Korea.

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.85.2-85
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• 2000