• Journal of the Korean Ceramic Society
• /
• v.33 no.10
• /
• pp.1101-1108
• /
• 1996

No-doped PZT thin films have been fabricated on Pt/Ti/SiO2/Si substrate using Sol-Gel technique. A fast annealing metho (three times of intermediate and final annealing) was used for the preparation of multi-coated 1800$\AA$ thick Nb-doped PZT thin films. As Nb doping percent was increased leakage current was lowered approximately 2 order but dielectic properties were degraded due to the appearance of pyrochlore phase and domain pinning. Futhermore the increase of the final annealing temperature up to 74$0^{\circ}C$lowered the pyrochlore phase content resulting in enhancing the dielectric properties of the Nb doped films. The 3%-Nb doped PZT thin films with 5% excess Pb showed a capacitance density of 24.04 fF/${\mu}{\textrm}{m}$2 a dielectric loss of 0.13 a switchable polarization of 15.84 $\mu$C/cm2 and a coercive field of 32.7 kV/cm respectively. The leakage current density of the film was as low as 1.47$\times$10-7 A/cm2 at the applied voltage of 1.5 V.

• Proceedings of the KIEE Conference
• /
• 1996.07c
• /
• pp.1434-1436
• /
• 1996

In this study, ferroelectric $PbTiO_3$ thin films were deposited on the Pt/$SiO_2$/Si substrate by Sol-Gel method. $PbTiO_3$ stock solution was made and spin-cooled at 4000[rpm] for 30[sec.]. Coated specimens were dried at $400[^{\circ}C]$ for 10[min.] and then annealed at $500{\sim}800[^{\circ}C]$ for 1 hour. Annealing temperature were examined to optimize micro structural and dielectric properties of the films. The ferroelectric perovskite phase was observed in the file annealed at $700[^{\circ}C]$ for 1 hour. In the case of $PbTiO_3$ thin films annealed at $700[^{\circ}C]$ for hour, dielectric constant and dielectric loss showed the good value of 324, 2.0[%], respectively.

• Journal of the Korean Applied Science and Technology
• /
• v.26 no.3
• /
• pp.288-296
• /
• 2009

In this study, the silica-based hybrid material with high barrier property was prepared by incorporating ethylene-vinyl alcohol (EVOH) copolymer, which has been utilized as packaging materials due to its superior gas permeation resistance, during sol-gel process. In preparation of this EVOH/$SiO_2$ hybrid coating materials, the (3-glycidoxy-propyl)-trimethoxysilane (GPTMS) as a silane coupling agent was employed to promote interfacial adhesion between organic and inorganic phases. As confirmed from FT-IR analysis, the physical interaction between two phases was improved due to the increased hydrogen bonding, resulting in homogeneous microstructure with dispersion of nano-sized silica particles. However, depending on the range of content of added silane coupling agent (GPTMS), micro-phase separated microstructure in the hybrid could be observed due to insufficient interfacial attraction or possibility of polymerization reaction of epoxide ring in GPTMS. The oxygen barrier property of the mono-layer coated BOPP (biaxially oriented polypropylene) film was examined for the hybrids containing various GPTMS contents. Consequently, it is revealed that GPTMS should be used in an optimum level of content to produce the high barrier EVOH/$SiO_2$ hybrid material with an improved optical transparency and homogeneous phase morphology.

• Journal of the Korean Electrochemical Society
• /
• v.6 no.1
• /
• pp.13-17
• /
• 2003

Cryogel and aerogel Pt-Ru/C were synthesized by the sol-gel process for the electrooxidation of methanol. From XRD analysis, it was found that the catalysts had highly dispersed Pt-Ru alloys on carbon support although high temperature treatments have been conducted. Electrocatalytic activities of 3 type aerogel catalysts were investigated in half cell experiments by cyclic voltammetry. Among them, Phloroglucinol-Formaldehyde(PF) type catalyst shows the highest activity. From the results of deactivation test for each catalysts, the aerogel catalysts are found to have excellent durability compared with those prepared by colloidal method.

• Analytical Science and Technology
• /
• v.27 no.6
• /
• pp.314-320
• /
• 2014

$La_{2-x}(MoO_4)_3:Er^{3+}/Yb^{3+}$ particles with doping concentrations of $Er^{3+}$ and $Yb^{3+}$ ($x=Er^{3+}+Yb^{3+}$, $Er^{3+}$=0.05, 0.1, 0.2 and $Yb^{3+}$ = 0.2, 0.45) were successfully prepared by the microwave-modified sol-gel method, and the upconversion photoluminescence properties were investigated. Well-crystallized particles, formed after heat-treatment at $900^{\circ}C$ for 16 h, showed a fine and homogeneous morphology with particle sizes of $2-5{\mu}m$. Under excitation at 980 nm, $La_{1.7}(MoO_4)_3:Er_{0.1}Yb_{0.2}$ and $La_{1.5}(MoO_4)_3:Er_{0.05}Yb_{0.45}$ particles exhibited a strong 525 nm emission band, a weak 550 nm emission band in the green region, and a very weak 655 nm emission band in the red region. The Raman spectra of the doped particles indicated the presence of strong peaks at higher frequencies of 752, 846, 922, 1358 and $1435cm^{-1}$ and lower frequency of $314cm^{-1}$ induced by the disorder of the $[MoO_4]^{2-}$ groups with the incorporation of the $Er^{3+}$ and $Yb^{3+}$ elements into the crystal lattice or by a new phase formation.

• Proceedings of the KIEE Conference
• /
• 2005.07c
• /
• pp.1989-1991
• /
• 2005

Lithium titanium oxide as anode material for energy storage prepared by novel synthesis method. $Li_4Ti_5O_{12}$ based spinel-framework structures are of great interest material for lithium-ion batteries. We describe here $Li_4Ti_5O_{12}$ a zero-strain insertion material was prepared by novel sol-gel method and by high energy ball milling (HEBM) of precursor to from nanocrystalline phases. According to the X-ray diffraction and scanning electron microscopy analysis, uniformly distributed $Li_4Ti_5O_{12}$ particles with grain sizes of 100nm were synthesized. Lithium cells, consisting of $Li_4Ti_5O_{12}$ anode and lithium cathode showed the 173 mAh/g in the range of $1.0{\sim}3.0V$. Furthermore, the crystalline structure of $Li_4Ti_5O_{12}$ didn't transfer during the lithium intercalation and deintercalation process.

• Journal of the Korean Applied Science and Technology
• /
• v.16 no.4
• /
• pp.317-322
• /
• 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 $NH_4OH$.

• Journal of the Korean Physical Society
• /
• v.73 no.10
• /
• pp.1535-1540
• /
• 2018

In this study, we prepared and characterized Nb-doped $Li_7La_3Zr_{2-x}O_{12}$ (LLZNO) powder and pellets with a cubic garnet structure by using a modified sol-gel synthesis and hot pressing. LLZNO powder with a very small grain size and cubic structure without secondary phases could be obtained by using a synthesis method in which Li and La sources in a propanol solvent were mixed together with Zr and Nb sources in 2-methoxy ethanol. A pure cubic phase LLZNO pellet could be fabricated from the prepared LLZNO and an additional 6-wt% of $Li_2CO_3$ powder by hot pressing at $1050^{\circ}C$ and 15.8 MPa. The hot-pressed LLZNO pellet with a relative density of 99% exhibited a very dense surface morphology. The total Li ionic conductivity of the hot-pressed LLZNO was $7.4{\times}10^{-4}S/cm$ at room temperature, which is very high level compared to other reported values. The activation energy for ionic conduction was estimated to be 0.40 eV.

• Advances in nano research
• /
• v.14 no.4
• /
• pp.355-362
• /
• 2023

Physical exercise, especially intense exercise and high intensity interval training (HIIT) by trampoline, can lead to muscle injuries. These effects can be reduced with intelligent products made of nanocomposite materials. Most of these nanocomposites are polymers reinforced with silicon dioxide, alumina, and titanium dioxide nanoparticles. This study presents a polymer nanocomposite reinforced with silica. As a result of the rapid reaction between tetraethyl orthosilicate and ammonia in the presence of citric acid and other agents, silica nanostructures were synthesized. By substituting bis (4-amino phenoxy) phenyl-triptycene in N, N-dimethylformamide with potassium carbonate, followed by catalytic reduction with hydrazine and Pd/C, the diamine monomer bis (4-amino phenoxy) phenyl-triptycene is prepared. We synthesized a new polyaromatic (imide) with triptycene unit by sol-gel method from aromatic diamines and dianhydride using pyridine as a condensation reagent in NMP. PI readily dissolves in solvents and forms robust and tough polymer films in situ. The FTIR and NMR techniques were used to determine the effects of SiO₂ on the sol-gel process and the structure of the synthesized nanocomposites. By using a simultaneous thermal analysis (DTA-TG) method, the appropriate thermal operation temperature was also determined. Through SEM analysis, the structure, shape, size, and specific surface area of pores were determined. Analysis of XRD results is used to determine how SiO₂ affects the crystallization of phases and the activation energy of crystallization.

• Journal of the Korean Ceramic Society
• /
• v.31 no.4
• /
• pp.359-366
• /
• 1994

Tow types of supports were made using $\alpha$-Al2O3 powder and optimum conditions to prepare for supports were provided. Sol solution for coating was synthesized by sol-gel method with aluminum isopropoxide. Supports were coated and heat-treatemented, where the thickness of coating layer was controlled by dipping time. Flux and permeability of alumina membrane were measured by liquid and gas filtration apparatus and these were compared with the provided model. It was confirmed that the coating was done very well without micro~crack and defect.