• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.85-86
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• 2020

With the increasing importance of environmental issues, the cementitious materials with self-cleaning or photocatalytic properties by introducing TiO₂ materials have been gaining a lot of attention. In this work, the influence of TiO₂ particle size and structure on its photocatalytic effect in cement paste was investigated. The degradation of methylene blue solution was used as the parameter for evaluating the photocatalytic effect of micro-TiO2 (m-TiO₂), nano-TiO2 (n-TiO₂), and TiO₂ nanotube (TNT). Moreover, the effect of these three TiO₂ materials on the cement hydration products was characterized by X-ray diffraction (XRD) and thermgravimetric analysis (TG). According to the results, it can be found that all of the TiO₂ materials promoted the formation of hydration products, especially TNT. On the other hand, the m-TiO₂ exhibited a better photocatalytic effect compared to other materials.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.4
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• pp.756-760
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• 2007

The $(1-x)Mg_4Ta_2O_9-xwt%TiO_2\;(x=5\sim20)$ microwave dielectric ceramics were prepared by solid-state reaction method and sintered at $1450^{\circ}C$. According to the X-ray diffraction data, the $Mg_4Ta_2O_9-xwt%TiO_2$ ceramics had main phase of $Mg_4Ta_2O_9$ and $MgTi_2O_5$ peaks were added by increasing of $TiO_2$ addition. Microwave dielectric properties of the $Mg_4Ta_2O_9-xwt%TiO_2$ ceramics were influenced by $MgTi_2O_5$ phase and properties of $TiO_2$. There was a little decrement of the quality factor from 116,800GHz of pure $Mg_4Ta_2O_9$ to 100,100GHz of 15wt% $TiO_2$ added one. But there was excellent improvement in temperature coefficient of the resonant frequency (TCRF) by addition of 15wt% $TiO_2$. The dielectric constant quality factor and TCRF of the $Mg_4Ta_2O_9-xwt%TiO_2$ ceramics sintered at $1450^{\circ}C$ were $13.08\sim16.41,\;45,000\sim165,410GHz,\;-24.82\sim+3.88ppm/^{\circ}C$, respectively, depending on the value of x. Simulated dielectric resonator (DR) with $Mg_4Ta_2O_9-15wt%TiO_2$ ceramics had the operating frequency of 11.97GHz and $S_{2,1}$ of -35.034dB.

• Journal of the Korean GEO-environmental Society
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• v.11 no.10
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• pp.33-39
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• 2010

A self-organized nano-structured, photocatalytic $TiO_2$ membrane with large surface area of anatase crystallites was successfully fabricated by anodization. The nano-structured anodized $TiO_2$ membrane was characterized using EDX, SEM and XRD techniques and the effect of electrolyte type and concentration to fabricate $TiO_2$ metal membrane was also investigated. Regular nano tubular arrays were obtained By the EDX, SEM and XRD patterns, the anodized $TiO_2$ membrane showed the enhanced photocatalytic properties of anatase phase. Photocatalytic activities of fabricated $TiO_2$ metal membrane was also experimentally investigated as model compound of humic acid.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.123-130
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• 1997

In this study, (Sr.Pb.Ca)TiO3-Bi2O3.3TiO2(SPCT) systems were investigated to develop a new material which has a high dielectric constant, a low dielectric loss and a small TCC(Temperature Coefficient of Capa-citance), and are suitable for high voltage applications as a function of the additions of Bi2O3.3TiO2 from 5 mol.% to 9 mol.%. The result obtained from our investigation showed that up to 6 mol.% Bi2O3.3TiO ad-dition the dielectric constant increased and it deteriorated at higher concentrations with increasing amount of the acicular grains. As a result of some dopants (SiO2, Nb2O3, MnO2) addition to SPCT, the specimens with MnO2 showed good dielectric properties. The dielectric constant decreased, but the TCC was improved with the addition of MnO2 from 0.15 wt.% to 0.45 wt. %.

• Membrane Journal
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• v.20 no.2
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• pp.120-126
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• 2010

In this study, the effect of surface deposition of $TiO_2$ nanoparticles at polyethersulfone (PES) microfiltraiton (MF) membrane on humic acid fouling was investigated. The effect was observed as a function of crystal structures of $TiO_2$ nanoparticles and solution chemistries including pH and divalent cation such as calcium. Our results showed clearly that $TiO_2$-deposited membrane could mitigate membrane fouling significantly. However, this effect was observed to be dependent upon crystal structures of $TiO_2$ nanoparticles and solution chemistries. In the absence of calcium, fouling mitigation was less pronounced for both anatase and hybrid $TiO_2$-deposited membrane than for rutile $TiO_2$-deposited membrane while opposite trend was observed after addition of calcium. In the presence of calcium, the adsorption of humic acid to $TiO_2$-deposited membrane can be reduced by electrostatic repulsions between humic acid and $TiO_2$ surface. Addition of calcium provided further beneficial effect on fouling mitigation particularly at higher pH for the anatase $TiO_2$ deposited membrane, implying that both increased hydrophilicity due to $TiO_2$ nanoparticles and negative surface charge of the membrane should affect fouling mitigation. However, rutile $TiO_2$ having more inertness generally than the anatase $TiO_2$ showed relatively robust effect on the fouling mitigation regardless of solution properties.

• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.153-158
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• 2002

$Al_2O_3$ composites powders with 1∼11 wt% $TiO_2$ were prepared by wet method and sintered at 1350$^{\circ}C$, 1450$^{\circ}C$ for 2h. Mechanical properties and microstructural evolution were investigated in this study. $Al_2O_3$-3 wt% $TiO_2$ composite were high bulk density of 2.37 g/$cm^3$ and low apparent porosity of 6.3%. The composites containing of 3 wt% $TiO_2$ showed moderately high bending strength of 68.9 MPa and the young's modulus of 35.5 MPa. The composites with increasing $TiO_2$ contents exhibit reduced thermal expansion coefficient due to the formation of $Al_2TiO_5$ phase.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.44 no.8
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• pp.1068-1074
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• 1995

Effect of (Zn$_{1}$3/Nb$_{2}$3/) $O_{2}$ addition on the phase changes and microwave dielectric properties of BaTi $O_{3}$-3Ti $O_{2}$ ceramics were investigated. Addition of (Zn$_{1}$3/Nb$_{2}$3/) $O_{2}$ to BaTi $O_{3}$-3Ti $O_{2}$ resulted in the formation of Ba $Ti_{4}$$O_{9}$, $Ba_{2}$ $Ti_{9}$ $O_{20}$, Ba(Zn$_{1}$3/Nb$_{2}$3/) $O_{3}$, and Ti $O_{2}$ phases. Ba $Ti_{4}$$O_{9}$ phase was gradually transformed to $Ba_{2}$ $Ti_{9}$ $O_{20}$. This was identified by XRD and microstructure. As the Ba $Ti_{4}$$O_{9}$ phase transformed to $Ba_{2}$ $Ti_{9}$ $O_{20}$ phase, the dielectric constant increased to 37.5. Q*f$_{o}$ value was 40000 at x=0.04, and the temperature coefficient of resonant frequency was +10ppm/.deg. C.C.. C.C.

• Clean Technology
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• v.23 no.1
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• pp.104-112
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• 2017

Hydrogen production via steam reforming of liquefaction liquid from marine algae over hydrothermal liquefaction was carried out at 873 ~ 1073 K with a commercial catalyst and Ni based $K_2Ti_xO_y$ added catalysts. Liquefaction liquid obtained by hydrothermal liquefaction (503 K, 2 h) was used as a reactant and comparison studies for catalytic activity over different catalysts (FCR-4-02, $Ni/K_2Ti_xO_y-Al_2O_3$, $Ni/K_2Ti_xO_y-SiO_2$, $Ni/K_2Ti_xO_y-ZrO_2/CeO_2$ and Ni/$K_2Ti_xO_y$-MgO), reaction temperature were performed. Experimental results showed Ni/$K_2Ti_xO_y$ based catalysts ($Ni/K_2Ti_xO_y-Al_2O_3$, $Ni/K_2Ti_xO_y-SiO_2$, Ni/$K_2Ti_xO_y-ZrO_2$/ $CeO_2$ and Ni/$K_2Ti_xO_y$-MgO) have a higher activity than commercial catalyst (FCR-4-02) and In particular, a product composition was different depending on support materials. An acidic support ($Al_2O_3$) and a basic support (MgO) led to a higher selectivity for CO while a neutral support ($SiO_2$) and a reducing support ($ZrO_2/CeO_2$) resulted in a higher $CO_2$ selectivity due to water gas shift reaction.

• Journal of Powder Materials
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• v.25 no.1
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• pp.48-53
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• 2018

One-dimensional rutile $TiO_2$ is an important inorganic compound with applicability in sensors, solar cells, and Li-based batteries. However, conventional synthesis methods for $TiO_2$ nanowires are complicated and entail risks of environmental contamination. In this work, we report the growth of $TiO_2$ nanowires on a Ti alloy powder (Ti-6wt%Al-4wt%V, Ti64) using simple thermal oxidation under a limited supply of $O_2$. The optimum condition for $TiO_2$ nanowire synthesis is studied for variables including temperature, time, and pressure. $TiO_2$ nanowires of ${\sim}5{\mu}m$ in length and 100 nm in thickness are richly synthesized under the optimum condition with single-crystalline rutile phases. The formation of $TiO_2$ nanowires is greatly influenced by synthesis temperature and pressure. The synthesized $TiO_2$ nanowires are characterized using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HR-TEM).

• Journal of Soil and Groundwater Environment
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• v.21 no.2
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• pp.8-14
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• 2016

We compared the plausible reaction mechanism and quantitative efficiency of highly self-organized TiO₂ nanotube (ntTiO₂) film with TiO₂ powder. Film was fabricated by electrochemical potentiostatic anodization of titanium thin film in an ethylene-glycol electrolyte solution containing 0.3 wt% NH₄F and 2 vol% deionized water. Nanotubes with a pore size of 80-100 nm were formed by anodization at 60 V for 3 h. Humic acid (HA) was degraded through photocatalytic degradation using the ntTiO₂ film. Pseudo first-order rate constants for 0.3 g of ntTiO₂, 0.3 g TiO₂ powder, and 1 g TiO₂ powder were 0.081 min⁻¹, 0.003 min⁻¹, and 0.044 min⁻¹, respectively. HA adsorption on the ntTiO₂ film was minimal while adsorption on the TiO₂ powder was about 20% based on thermogravimetric analysis. Approximately five-fold more normalized OH radicals were generated by the ntTiO₂ film than the TiO₂ powder. These quantitative findings explain why ntTiO₂ film showed superior photocatalytic performance to TiO₂ powder.