• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.3021-3024
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• 2009

$Zn_2Ti_{1-x}Fe_xO_4\;(0\;{\leq}\;x\;{\leq}\;0.7)$ photocatalysts were synthesized by polymerized complex (PC) method and investigated for its physico-chemical as well as optical properties. $Zn_2Ti_{1-x}Fe_xO_4$ can absorb not only UV light but also visible light region due to doping of Fe in the Ti site of $Zn_2TiO_4$ lattice because of the band transition from Fe 3d to the Fe 3d + Ti3d hybrid orbital. The photocatalytic activity of Fe doped $Zn_2TiO_4$ samples for hydrogen production under UV light irradiation decreased with an increase in Fe concentration in $Zn_2TiO_4$. Consequently, there exists an optimized concentration of iron for improved photocatalytic activity under visible light (${\lambda}{\leq}$420 nm)

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.554-560
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• 2009

We investigate a method for the electrochemical preparation of titanium dioxide/carbon nanotube ($TiO_2$/CNT) composites involving the electroplating of Ti in a titanium n-butoxide (TNB) electrolyte into a CNT matrix. The Brunauer-Emmett-Teller (BET) surface areas of $TiO_2$/CNT composites decrease as the electrochemical operating time increases. Changes in XRD patterns show a typical anatase type on the $TiO_2$/CNT composite prepared with a CNT matrix by the electroplating method in a TNB solution. In SEM micrographs, the titanium complex particles are uniformly distributed on the CNT surface. The results of chemical elemental analysis for the $TiO_2$/CNT composites show that most of the spectra for these samples produce stronger peaks for carbon and Ti metal than for any other element. Finally, the prominent photoelectrocatalytic activities of the $TiO_2$/CNT composites can be attributed to the combined effects of photodegradation of $TiO_2$, electron assistance of CNT, and the application of a sufficient voltage.

• Journal of the Korean Ceramic Society
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• v.46 no.4
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• pp.357-364
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• 2009

We investigate a method for the electrochemical preparation of titanium dioxide/carbon nanotube ($TiO_2$/CNT) composites involving the electroplating of Ti in a titanium n-butoxide (TNB) electrolyte into a CNT matrix. The BET surface areas of $TiO_2$/CNT composites decreased as electrochemical operating time increased. Changes in XRD patterns showed a typical anatase type on the $TiO_2$/CNT composite prepared with a CNT matrix by the electroplating method in the TNB solution. In SEM micrographs, the titanium complex particles were uniformly distributed on the CNT surface. The results of chemical elemental analysis for the $TiO_2$/CNT composites showed that most of the spectra for these samples produced stronger peaks for carbon and Ti metal than those of any other element. Finally, the prominent photoelectrocatalytic (PEC) activities of the $TiO_2$/CNT composites could be attributed to the combined effects of photodegradation of $TiO_2$, electron assistance of CNT and the application of a sufficient voltage.

• Journal of the Korean Ceramic Society
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• v.25 no.3
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• pp.293-299
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• 1988

The effects of flux KCl and dopants, La2O3 and Ta2O5, on the PTCR characteristics in molten salt synthesized BaTiO3 have been studied. The resistivity of BaTiO3 at room temperature decreases with increasing amount of dopant La2O3 up to 0.2 atom%, and then increases with La2O3 content. In case of dopant Ta2O5, it increases with increasing amount ofthe dopant. These results could be explained by observation of the microstructure and defect equation. From the results of complex impedance-frequency characteristics, the grain resistances are almost same but the resistances at the grain boundary are quite different.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.6
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• pp.662-669
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• 2007

The effect of advanced oxidation processes such as $O_3$, $UV/TiO_2$, $O_3/UV$ and $O_3/UV/TiO_2$ on decolorization and COD removal of Rhodamine B(RhB) wastewater were considered. The results showed that the higher the $O_3$ concentration was, the higher the decolorization observed and the optimum $TiO_2$ dosage was 0.4 g/L in $UV/TiO_2$ and $O_3/UV/TiO_2$ process. $O_3/UV$ process showed the higher initial decolorization rate constant and the shorter termination time for decolorization than those of the $O_3$ process. The decolorization rate constants in various systems followed the order of $O_3/UV/TiO_2>O_3/UV>O_3{\gg}UV/TiO_2$. The decolorization rate of the RhB solution in every processes was more rapid than the mineralization rate identified by COD removal. The latter took longer time for further oxidation. The COD removal rate constants in four systems followed the order of $O_3/UV/TiO_2>O_3/UV>UV/TiO_2{\geqq}O_3$. Among four processes, combined photocatalysis and ozonation$(O_3/UV/TiO_2)$ was the most prospective process for removing color and COD such as dye wastewater.

• Journal of the Korean Chemical Society
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• v.44 no.1
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• pp.60-67
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• 2000

The wavelength of the surface plasmon absorption depends on the dielectric matrix. $TiO_2/SiO_2$ complex oxide films doped with Au nanoclusters were prepared by sol-gel spin-coating method using $Ti(OPr^i)_4$, $Si(OEt)_4$, and $HAuCl_4{\cdot}7H_2O$. The wavelength of the maximum absorption of Au nanoehrsters in the $TiO_2/SiO_2$ thin films was obtained with lineality from 540 nm to 615 nm depending on the molar ratio of $TiO_2$. The particle sizes and structures of these nanoclusters have been identified through a TEM and X-ray diffraction patterns. The dielectric constants of $TiO_2/SiO_2$ thin films were calculated from the experimental results.

• Applied Microscopy
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• v.32 no.2
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• pp.157-162
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• 2002

Microstructural investigations of $(Na_{1/2}Pr_{1/2})TiO_3$ (NPT) complex perovskite compounds were carried out using X-ray diffractometry and transmission electron microscopy. NPT had not 1:1 chemical ordering of Asite cations but had the antiphase and inphase tilting of oxygen octahedron and the antiparallel shift of cations. Both the antiphase boundaries and the ferroelastic domains were not present in the microstructure. Unidentified second phase was found in the microstructure. The measured dielectric properties were ${\varepsilon}_r=99.6,\;Q\;{\Large f}_o=1124\;GHz,\;{\tau}_{f}=-233.64ppm/^{\circ}C$.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.4
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• pp.368-375
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• 2006

Single and complex metal oxide catalysts supported onto a commercial DT51D $TiO_2$ have been investigated for gas-phase TCE oxidation in a continuous flow type fixed-bed reaction system to develop a better design approach to catalysts for this reaction. Among the $TiO_2$-supported single metal oxides used, i.e., $CrO_x,\;FeO_x,\;MnO_x,\;LaO_x,\;CoO_x,\;NiO_x,\;CeO_x\;and\;CuO_x$, with the respective metal contents of 5 wt.%, the $CrO_x/TiO_2$ catalyst was shown to be most active for the oxidative TCE decomposition, depending significantly on amounts of $CrO_x\;on\;TiO_2$. The use of high $CrO_x$ loadings greater than 10 wt.% caused lower activity in the catalytic TCE oxidation, which is probably due to production of $Cr_2O_3$ crystallites on the surface of $TiO_2$. $CrO_x/TiO_2$-supported $CrO_x$-based bimetallic oxide catalysts were of particular interest in removal efficiency for this TCE oxidation reaction at reaction temperatures above $200^{\circ}C$, compared to that obtained with $CrO_x$-free complex metal oxides and a 10 wt.% $CrO_x/TiO_2$ catalyst. Catalytic activity of 5 wt.% $CrO_x-5$ wt.% $LaO_x$ in the removal reaction was similar to or slightly higher than that acquired for the $CrO_x$-only catalyst. Similar observation was revealed for 5 wt.% $CrO_x$-based bimetallic oxides consisting of either 5 wt.% $MnO_x,\;CoO_x,\;NiO_x\;or\;FeO_x$. These results represent that such $CrO_x$-based bimetallic systems for the catalytic TCE oxidation on significantly minimize the usage of $CrO_x$ that is well known to be one of very toxic heavy metals, and offer a very useful technique to design new type catalysts for reducing chlorinated volatile organic substances.

• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.178-183
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• 2016

Ferroelectric relaxor ceramics with $BaTiO_3-NaNbO_3-Bi(Mg_{1/2}Ti_{1/2})O_3$ ternary compositions (BT-NN-BMT) have been prepared by sol-gel powder synthesis and consequent bulk ceramic processing. Through the modified chemical approach, fine and single-phase complex perovskite compositions were successfully obtained. Temperature and frequency dependent dielectric properties indicated typical relaxor characteristics of the BT-NN-BMT compositions. The ferroelectric-paraelectric phase transition became diffusive when NN and BMT were added to form BT based solid solutions. BMT additions to the BT-NN solid solutions affected the high temperature dielectric properties, which might be attributable to the compositional inhomogeneity of the complex perovskite and resulting weak dielectric coupling of the Bi-containing polar nanoregions (PNRs). The temperature stability of the dielectric properties was good enough to satisfy the X9R specification. The quasi-linear P-E response and the temperature- stable dielectric properties imply the high potential of this ceramic compound for use in high temperature capacitors.

• Korean Journal of Materials Research
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• v.31 no.1
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• pp.8-15
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• 2021

Transparent, photocatalytic, and self-cleaning TiO2 thin film is developed by TiO2 sol-gel coating on glass and polycarbonate (PC) substrates. Acetyl acetone (AcAc) suppresses the precipitation of TiO2 by forming a yellowish (complex) transparent sol-gel. XPS analysis confirms the presence of Ti2p and O1s in the thin films on glass and PC substrates. The TiO2-sol is prepared by stabilizing titanium (IV) isopropoxide (TTIP) with diethylamine and methyl alcohol. The addition of AcAcsilane coupling solution to the TiO2-sol instantaneously turns to yellowish color owing to the complexing of titanium with AcAc. The AcAc solution substantially improves the photocatalytic property of the TiO2 coating layer in MB solutions. The coated TiO2 film exhibits super hydrophilicity without and with light irradiation. The TiO2 thin film stabilized by adding 8.7 wt% AcAc shows the highest photo-degradation for methylene blue (MB) solution under UV light irradiation. Also, the optimum photocatalytic activity is obtained for the 8.7 wt% AcAc-stabilized TiO2 coating layer calcined at 450 ℃. The thin-films on glass exhibit fast self-cleaning from oleic acid contamination within 45 min of UV-light irradiation. The appropriate curing time at 140 ℃ improves the anti-fogging and thermal stability of the TiO2 film coated on PC substrate. The watermark-free PC substrate is particularly beneficial to combat fogging problems of transparent substrates.