• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.193-193
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• 2011

To obtain ceramic films, the sol-gel coating technique has been broadly used with heat treatment, but crack formation tend to occur during heat treatment in thick sol-gel films. We prepared PZT thin films by sol-gel method with single-step spin coating process. The PZT solution have been synthesized using lead acetate ($Pb(CH_3COO)_2$), zirconium acetylacetonate ($Zr(OC_3H_7^n)_4$), and titanium diisopropoxide bis(acetylacetonate) 75wt% in isopropanol ($Ti(OC_3H_7^i)_2(OC_3H_7^n)_2$) as starting materials and n-propanol was selected as a solvent. The poly(vynilpyrrolidone) (PVP) was added with 0, 0.25, 0.5, 0.75, and 1 molar ratios to control viscosity of solution. We investigated influence of the viscosity on thickness, microstructure, and electrical properties of final PZT films. Thermo-gravimetric analysis and differential scanning calorimeter (TGA/DSC) was carried out from room temperature to $800^{\circ}C$ in order to measure pyrolysis temperature. Structural characteristics were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Ferroelectric and dielectric properties were measured by RT66A (Radiant) and impedance analyzer (Agilent), respectively. The thicknesses of PZT films depended on incorporation of an excess amount of PVP. Finally, we obtained PZT films of good quality without crack formation via single-step spin coating.

• Journal of Electrochemical Science and Technology
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• v.8 no.2
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• pp.87-95
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• 2017

Enzymatic fuel cells are promising low cost, compact and flexible energy resources. The basis of enzymatic fuel cells is transfer of electron from enzyme to the electrode surface and vice versa. Electron transfer is done either by direct or mediated electron transfer (DET/MET), each one having its own advantages and disadvantages. In this study, the DET and MET of laccase-based biocathodes are compared with each other. The DET of laccase enzyme has been studied using two methods; assemble of needle-like carbon nanotubes (CNTs) on the electrode, and CNTs/Nafion polymer. MET of laccase enzyme also is done by use of ceramic electrode containing, ABTS (2,2'-azino-bis [3-ethylbenzthiazoline-6-sulphonic acid]) /sol-gel. Cyclic voltammetric results of DET showed a pair of well-defined redox peaks at $200{\mu}A$ and $170{\mu}A$ in a solution containing 5and $10{\mu}M$ o-dianisidine as a substrate for needle-like assembled CNTs and CNTs-Nafion composite respectively. In MET method using sol-gel/ABTS, the maximum redox peak was $14{\mu}A$ in the presence of 15 M solution o-dianisidine as substrate. The cyclic voltammetric results showed that laccase immobilization on needle-like assembled CNTs or CNTs-Nafion is more efficient than the sol-gel/ABTS electrode. Therefore, the expressed methods can be used to fabricate biocathode of biofuel cells or laccase based biosensors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.5
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• pp.801-804
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• 2006

[ $GdAlO_3(GAO)$ ] buffer layer for $YBa_2Cu_3O_{7-{\delta}}(YBCO)$ coated superconductor wire was fabricated by sol-gel processing. Precursor solution was prepared by dissolving 1:1 stoichiometric quantaties of gadolinium nitrate hexahydrate and aluminum nitrate nonahydrate in methanol. The solution was spin-coated on $SrTiO_3(STO)$(100) single crystal substrates and heated at $1000^{\circ}C$ for 2h in wet $N_2-5%\; H_2$, atmosphere. A SEM(scanning electron microscopy) observation of the surface morphology of the GAO layer has shown that it has a faceted morphology indicating epitaxy. It was shown from x-ray diffraction(XRB) that GAO buffer layer was highly c-axis oriented epitaxial thin film with both good out-of-plane($FWHM=0.29^{\circ}$ for the (002) reflection) and in-plane ($FWHM=1.10^{\circ}$ for the {112} reflection) alignment.

• Resources Recycling
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• v.17 no.5
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• pp.52-59
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• 2008

Sol-gel process applied in this study was carried out by chelation of metal ions and citric acid. From the results of thermal gravimetric analysis and XRD analysis of gel powder obtained through sol-gel and heat treatment, gel powders are mostly amorphous, and crystallize completely at $900^{\circ}C$, and the crystalline structure of YAG increases with increasing calcinations temperature. Since YAG prepared by sol-gel & calcinations process was porous, and the sape and size was irregular and nonuniform, the shape and size of YAG powder had to be controlled. Therefore the effects of organic materials such as ethylene glycol and surfactant on the crystalline structure of YAG powder were investigated. Polyesterification of ethylene glycol and citric acid separated reaction area of metal ions in the solution and decreased the size of YAG primary particles. The addition of Igepal 630 as surfactant formed the droplet in the solution, and increased the size of primary particles which forms the aggregate of YAG In order to obtain monodispersed YAG particles of uniform size, gel powder prepared with organic materials had to be milled before calcination. And milling process was very important for obtaining YAG of uniform size.

• Journal of the Korean Chemical Society
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• v.33 no.3
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• pp.326-331
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• 1989

Superconducting fiber of high Tc $YBa_2Cu_3O_{7-{\sigma}}$ was successfully prepared by the sol-gel method. The stoichiometric mixture of Y, Ba and Cu nitrates was dissolved in water, to which citric acid solution was added. Then ammonium hydroxide was added to the mixture in order to increase the pH to a value between 5.8 and 6.2. The mixture was heated carefully to form a homogeneous colloid sol at 358 K. The solution was viscous enough to draw a long gel fiber, which was then heated at 1223K for 8 hrs. under oxygen partial pressure of $Po_2$ = 1 atm., cooled slowly and annealed at 723K for 13 hrs.. The reacted superconducting sample maintained a fiber form with some shrinkage of its volume. The superconducting transition temperatures (Tc, onset and Tc, offset) of $YBa_2Cu_3O_{7-{\sigma}}$ have been determined to be approximately 95K and 82K, respectively. The superconducting phase was also confirmed by Meissner effect at liquid nitrogen boiling temperature.

• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.62-68
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• 2003

Ba-ferrite particles added with Co and Ti, which were known well the additives for the control in coercivity, were synthesized by sol-gel method. In the range 90 to 120 minute reaction time, a stable sol solution which showed no change with temperature, pH, viscosity and aging time. After dried and heat treatment of sol solution, Ba-ferrite phase formed at $700^{\circ}C$ with Differential Thermal Analysis(DTA) and X-Ray Diffractometer(XRD) measurement. The crystallinity became to be better with increasing the temperature. It were showed by Scanning Electron Microscopy(SEM) that Ba-ferrite increased to particle sizes as increasing heating temperature and obtained of narrow particles size distribution. Also, magnetic characteristics of Ba-ferrite powders Co and Ti added were observed by a Vibrating Sample Magnetometer(VSM). Saturation magnetization$(M_s)$ was not much changed, however. the coercivity$(H_c)$dramatically dropped with addition of Co and Ti.

• Journal of Powder Materials
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• v.16 no.4
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• pp.254-261
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• 2009

In this study, we investigated the unit process parameters in spherical $UO_2$ kernel preparation. Nearly perfect spherical $UO_3$ microspheres were obtained from the 0.6M of U-concentration in the broth solution, and the microstructure of the $UO_2$ kernel appeared the good results in the calcining, reducing, and sintering processes. For good sphericity, high density, suitable microstructure, and no-crack final $UO_2$ microspheres, the temperature control range in calcination process was $300{\sim}450^{\circ}C$, and the microstructure, the pore structure, and the density of $UO_2$ kernel could be controlled in this temperature range. Also, the concentration changes of the ageing solution in aging step were not effective factor in the gelation of the liquid droplets, but the temperature change of the ageing solution was very sensitive for the final ADU gel particles.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.535-540
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• 2011

Organic-inorganic hybrid coating solutions were prepared starting from colloidal silica, lanthanum nitrate and ${\gamma}$-glycidoxypropyl trimethoxysilane by the sol-gel method. Also, spiropyran-doped hard coating solutions were prepared by mixing the spiropyran solution, obtained after dissolving spiropyran dye into tetrahydrofuran solvent, with the organic-inorgnic hybrid coating solutions. The spiropyran-doped hard coating solutions were applied as a thin layer to polycarbonate sheets, and their photochromic properties were investigated. The effect of amount of colloidal silica added into the coating solutions was investigated on the photochromic properties of coating films. Both decoloration rate and pencil hardness of the coating films were increased with increasing the amounts of colloidal silica.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.274-278
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• 2008

Hard coating solutions were prepared from glycidoxypropyl trimethoxysilane (GPTMS) and methacryloxypropyl trimethoxysilane (MPTMS) precursors with different molar ratios of 10:0, 9:1, 7:3, 5:5, 3:7, and 0:10, respectively, by the sol-gel method. The polycarbonate (PC) sheets were spin-coated, and cured at $130^{\circ}C$ for 3 h. The effect of the GPTMS:MPTMS molar ratios of the mixture was investigated on the properties of coating films. The highest pencil hardness and adhesion to PC sheets of coating films were found for solution with GPTMS:MPTMS molar ratio of 5:5. Also, the pencil hardness of coating films was increased with increasing the $H_2O$ content in the coating solutions.

• Journal of the Korean Ceramic Society
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• v.40 no.2
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• pp.184-190
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• 2003

$Sr_{0.9}Bi_{2.1}Ta_2O_9$thin films were deposited on $IrO_2$ electrode by spin coating method using photosensitive sol-gel solution. To ensure the UV-exposure effect on SBT thin films, UV irradiated films and non-UV irradiated films were analyzed by XRD, SEM. As a result, UV-irradiation on SBT thin films promoted grain growth of SBT compared with no UV irradiation. In case of the UV irradiated films annealed at$740{\circ}C$for 1 h in an oxygen ambient, the 2Pr value and Pr/Ps at${pm}5$V were$11.48{mu}C/cm^2$and 0.53, respectively. 2Pr values of the UV irradiated SBT thin films at$660-740{circ}C were approximately 12% higher than those of non-UV irradiated thin films.