• Korean Journal of Materials Research
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• v.15 no.7
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• pp.444-447
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• 2005

In this study, $Hydroxyapatite+TiO_2(HAp+TiO_2)$ composite sol coatings on Cp-Ti substrates were deposited by using a sol-gel derived precursor. Prior to hydroxyapatite coating, the samples were micropolished and divided into three sets. The first set was coated with hydroxyapatite (HAp) directly on Cp-Ti. The second set was first coated with intermediate titania layer and then coated with HAp. The third set samples were coated with $HAp+TiO_2$ (50:50) composite sol. Each samples were predried at $200^{\circ}C$, and heat treated at $600^{\circ}C$. The formation of hydroxyapatite has been confirmed by XRD analyses and the substrate material was found to be oxidized with negligible amount of CaO in the coating. The NaOH treated samples showed the presence of rutile crystal. The SEM studies revealed surface morphologies of each samples. $HAp+TiO_2$ composite sol coating layer was found to be smooth. The bonding strength of each samples were calculated using pull out tests. The bonding strength of the $HAp+TiO_2$ composite sol coating on substrate was 29.35MPa.

• The Korean Journal of Ceramics
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• v.3 no.1
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• pp.52-56
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• 1997

The Pt doped $TiO_2$ composite membranes were prepared by the sol-gel process. The Pt doped titania sol was peptized with hydrochloric acid in the pH range of 1.23 to 1.32 at 5$0^{\circ}C$. The average particle size of the Pt doped titania sol was shown to be below 15nm and well dispersed in the solution. XPS show the Pt elements continuous and homogeneous dispersed in the $TiO_2$ membrane. The mean particle size of the Pt doped $TiO_2$ composite membrane has smaller than that of the undoped $TiO_2$ composite membrane. The average pore size of the Pt doped $TiO_2$ composite membrane was increased from 58 to 193 $\AA$ with firing temperature changed from 550 to 85$0^{\circ}C$. It was observed that the Pt doped $TiO_2$ composite membranes showed crack-free and homogeneous microstructue as well as narrow particle size distribution up to above 75$0^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.27 no.1
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• pp.65-70
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• 2006

An amperometric glucose biosensor has been developed based on the use of the nanoporous composite film of sol-gel-derived zirconia and perfluorosulfonated ionomer, Nafion, for the encapsulation of glucose oxidase (GOx) on a platinized glassy carbon electrode. Zirconium isopropoxide (ZrOPr) was used as a sol-gel precursor for the preparation of zirconia/Nafion composite film and the performance of the resulting glucose biosensor was tuned by controlling the water content in the acid-catalyzed hydrolysis of sol-gel stock solution. The presence of Nafion polymer in the sol-gel-derived zirconia in the biosensor resulted in faster response time and higher sensitivity compared to those obtained at the pure zirconia- and pure Nafion-based biosensors. Because of the nanoporous nature of the composite film, the glucose biosensor based on the zirconia/Nafion composite film can reach 95% of steady-state current less than 5 s. In addition, the biosensor responds to glucose linearly in the range of 0.03-15.08 mM with a sensitivity of 3.40 $\mu$A/mM and the detection limit of 0.037 mM (S/N = 3). Moreover, the biosensor exhibited good sensor-to-sensor reproducibility (~5%) and long-term stability (90% of its original activity retained after 4 weeks) when stored in 50 mM phosphate buffer at pH 7 at 4 ${^{\circ}C}$.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.366-373
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• 2015

Sol-gel binder was prepared by hydrolysis and condensation reaction using boehmite sol and methyltrimethoxysilane as a function of aging-time. The coating slurry was composed of a plate-shape alumina in the sol-gel binder for the EPD process, in which particles dispersed in the slurry were deposited on the electrode under an electric field due to the surface charge. We studied the effects of three parameters: the content of boehmite, the aging time, and the applied voltage, on the physical, thermal, and electrical properties of the hybrid composite films by EPD. The amount of boehmite was 10 ~ 20 wt% and the aging time was 0.5 ~ 72, with a fixed amount of plate-shape alumina of 10 wt%. The condition of applied voltage was 5 ~ 30 V with a distance of 2 cm between the electrode during the EPD process. We confirmed that a structure of hybrid composite films of well-ordered plate alumina was deposited on the substrate when the film was prepared using a sol-gel binder composed of 15 wt% boehmite with 1 hr aging time and EPD at 10 V. The process shows a weight loss of 7% at $500^{\circ}C$ in TGA and a breakdown voltage of 8 kV at $87{\mu}m$.

• Preventive Nutrition and Food Science
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• v.3 no.3
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• pp.292-294
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• 1998

Surimi sol and gel were prepared by mixing egg albumin, starch, oil and carrageenan, which are used as representative ingredients in the surimi composite, at different ratio. Structural properties in surimi composite were investigated by examining the phase changes and dispersion pattern (average particle size, size range and the averge number of particle) of the particulate ingredients in sol and gel with an image analyzer. A staining technique of the specimen containing egg albumin in surimi gel was developed by adjusting pH of a toluidine staining solution. Image analysis revealed that size and density of ingredient particles were function of the level and dispersion of ingredients except of starch-incorporated surimi gel which showed maximum particle size at 6%.

• Journal of the Korean Ceramic Society
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• v.36 no.4
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• pp.391-402
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• 1999

Characteristics of composite electrolytes which were prepared by coating a thin film of YSZ (yttria sta-bilized zirconia : (ZrO2)0.92 (Y2O3)0.08) on YDC (yttria doped ceria : Ce0.8Y0.2O1.9) with mixed conductivity have been investigated in order to develop the low-temperature solid oxide fuel cell. The thickness (t) of spin-coated YSZ thin films after the heat-treatment at 600$^{\circ}C$ was increased proportionally to the sol con-centrations (C) while the decrease in its thickness with the spin rate ($\omega$) could be expressed in the e-quation of ln t=9.49-0.53 ln $\omega$(0.99mol//s sol conc.) When the sol concentration and the spin rate being less than 0.99 mol/l and higher than 1000 rpm respectively reliable YSZ/YDC composite electrolytes could be obtained by multi-coating although several micro-cracks were observed in singly coated YSZ film surfaces. The dense YSZ film with a 1$\mu\textrm{m}$ thickness was prepared by coating of 0.99 mol/l YSZ sol five-times at 2000 rpm followed by heat-treatment at 1400$^{\circ}C$ for 2h, The adhesion between YSZ film and YDC substrate was found to be very good. The open circuit voltages of H2/O2 single cell with YSZ/YDC composite electrolytes were 0.79∼0.82 V at 800$^{\circ}C$ and 0.75∼0.77V at 900$^{\circ}C$ The open circuit voltage was inversely proportioned to the thickness ratio of YSZ thin film (1$\mu\textrm{m}$) to YDC substrate(0.28-2.22 mm)

• Journal of the Korean Ceramic Society
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• v.33 no.1
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• pp.110-118
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• 1996

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.137-140
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• 2001

Oragnic/inorganic hybrid materials prepared by sol-gel method have rapidly become a fasci nating research field in materials science. In this study, Polyimide/$\textrm{TiO}_2$ composites were synthesized from nano-sized anatase $\textrm{TiO}_2$ and two types of Polyimide (BTDA-PPD, PMDA-ODA) by Sol-gel method. Nano-sized $\textrm{TiO}_2$ particles were prepared from $\textrm{TiOEt}_4$ solution. The composites were charcaterized by using XRD, TGA, IR, TEM, and Atomic Force Microscope(AFM). $\textrm{TiO}_2$ nano particles were dispersed well in polyimide matrix and the thermal stability of polyimide was improved with $\textrm{TiO}_2$ nano-sized particles.

• Journal of Powder Materials
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• v.10 no.5
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• pp.310-317
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• 2003

Two-component ceramic (alumina-zirconia) composites were fabricated by a soft-solution process in which polyethylene glycol (PEG) was used as a polymeric carrier. Metal salts and PEG were dissolved in ethyl alcohol without any precipitation in 1:1 volume ratio of alumina and zirconia. In the non-aqueous system, the flammable solvent made explosive, exothermic reaction during drying process. The reaction resulted in formation of volume expanded, porous precursor powders by a vigorous decomposition of organic components in the precursor sol. The PEG content affected the grain size of sintered composites as well as the morphology of precursor powders. The difference of microstructure in sintered composite was attribute to the solubility and homogeneity of metal cations in precursor sol. At the optimum amount of the PEG polymer, the metal ions were dispersed effectively in solution and a homogeneous polymeric network was formed. It made less agglomerated particles in the precursor sol and affected on uniform grain size in sintered composite.

• Bulletin of the Korean Chemical Society
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• v.22 no.12
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• pp.1366-1370
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• 2001

Thin films of the SiO2-TiO2-PDMS composite material have been prepared by the sol-gel dip coating method. Acid catalyzed solutions of tetraethoxy silane (TEOS) and polydimethyl siloxane (PDMS) mixed with titanium isopropoxide Ti(OiPr) were used as precursors. The optical and structural properties of the organically modified 70SiO2-30TiO2 composite films have been investigated with Fourier Transform Infrared Spectroscopy (FT-IR), UV-Visible Spectroscopy (UV-Vis), Differential Thermal Analysis (DTA) and prism coupling technique. The films coated on the soda-lime-silicate glass exhibit 450-750 nm thickness, 1.56-1.68 refractive index and 88-94% transmittance depending on the experimental parameters such as amount of PDMS, thermal treatment and heating rate. The optical loss of prepared composite film was measured to be about 0.34 dB/cm.