• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.109-112
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• 2005

Electronic and magnetic properties of $Ti_{1-x}M_xO_{2-\delta}$ (M=Co and Fe) thin films grown by sol-gel method have been investigated. Anatase and rutile $Ti_{1-x}Co_xO_{2-\delta}$ films were successfully grown on $Al_2O_3$ (0001) substrates and exhibited p-type electrical conductivity while the undoped films n-type conductivity. Room temperature vibrating sample magnetometry measurements on the anatase and rutile $Ti_{1-x}Co_xO_{2-\delta}$ films with same x ($=4.8 at.{\%}$) showed quite similar magnetic hysteresis curves with the saturation magnetic moment of $\~4 {\mu}_B$ per Co ion despite their differences in structural and electronic properties. Such giant magnetic moment is attributable to the unquenched orbital moment of the $Co^{2+}$ ions substituting the octahedral $Ti^{4+}$ sites. Similar ferromagnetic behavior was observed for $Ti_{1-x}Fe_xO_{2-\delta}$ films that are highly resistive compared to the Co doped samples. Saturation magnetic moment was found to decrease for higher x, i.e., $\~2$ and $\~1.5 {\mu}_B$ per Fe ion for x=2.4 and 5.8 at. $\%$, respectively. Conversion electron $M\ddot{o}ssbauer$ spectroscopy measurements predicted the coexistence of $Fe^{2+}$ and $Fe^{3+}$ ions at the octahedral sites of $Ti_{1-x}Fe_xO_{2-\delta}$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.5
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• pp.213-218
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• 2014

An investigation of the influence of $WO_3$ addition with different precursors and preparation methods on the phase formation and selective catalytic reduction (SCR) efficiency of anatase-$TiO_2$ powders has been carried out. An anatase-$TiO_2$ synthesized by precipitation process was used as a catalyst support. For $WO_3(10wt%)/TiO_2$, the W loading to the $TiO_2$ support led to the lower in anatase to rutile transition temperature to ${\sim}900^{\circ}C$ from $1200^{\circ}C$ of the $TiO_2$ support alone. In the case of $WO_3(10wt%)/TiO_2$ SCR powders obtained from a wet process with ammonium meta-tungstate (AMT) precursor, the highest $NO_X$ conversion efficiency was achieved at $450^{\circ}C$ remaining high efficiency at $500^{\circ}C$, while the same composition prepared from a dry process with $WO_3$ addition showed the lowered efficiency with temperature after reaching the efficiency maximum at $350^{\circ}C$. The same tendency has been found that the $V_2O_5(5wt%)-WO_3(10wt%)/TiO_2$ SCR powders obtained from the wet process with AMT precursor has shown the superior $NO_X$ conversion efficiency over 90 % in a wider temperature range of $300{\sim}500^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.5
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• pp.510-515
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• 1999

Synthesize of anatase type $TiO_2$ from $TiCl_4$ solution was studied. KOH was used on dehydration reaction of $TiCl_4$ solution. Products of dehydration reaction was calcined at 300, 500, 700, 900, $1000^{\circ}C$ during 1hour. Calcined products was studied by XRD, DTA, and FT-IR for effect of calcined temperature. The results are as follow. \circled1 Product pf dehydration reaction at$ 90^{\circ}C$ was semicrystalline anatase type $TiO_2$ because it has a peak vary broad and low at the position of anatase crysral XRD pattern. \circled2 Pure titanium oxide semi-crystalline products were produced at acid pH condition which convert to anatase crystal at $300^{\circ}C$ and to rutile crystal at $700^{\circ}C$. \circled3 The chemical composition of semicrystalline products which was produce at alkali pH conditions, were potasium titante. Potasium-titanate semi-crystalline products crystallized at 630~$640^{\circ}C$ \circled4 The transition temperature of potassium dopped titanium oxide semi-crystalline products was increased with the contents of potasium. \circled5 The optimum synthesise condition of anatase $TiO_2$ products from $TiCl_4$ and KOH are pH 3~5 and $300^{\circ}C$ calcination.

• Journal of Photoscience
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• v.10 no.2
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• pp.199-202
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• 2003

The relationship between the morphology of nanostructured TiO$_2$ films and the photo-injected electron transport has been investigated using intensity-modulated photocurrent spectroscopy (IMPS). For this purpose, three different TiO$_2$ films with 5 ${\mu}{\textrm}{m}$ thickness are prepared: The rutile TiO$_2$ film with 500 nm-sized cluster-like spherical bundles composed of the individual needles (Tl), the rutile TiO$_2$ film made up of non-oriented, homogeneously distributed rod-shaped particles having a dimension of approximately 20${\times}$80 nm (T2), and the anatase TiO$_2$ film with 20 nm-sized spherically shaped particles (T3). Cross sectional scanning electron micrographs show that all of the TiO$_2$films have a quite different particle packing density: poorly packed Tl film, loosely packed T2 film and densely packed T3 film. The electron transport is found to be significantly influenced by film morphology. The effective electron diffusion coefficient D$_{eff}$ derived from the IMPS time constant is an order of magnitude lower for T2 than for T3, but the D$_{eff}$ for the Tl sample is much lower than T2. These differences in the rate of electron transport are ascribed to differences in the extent of interparticle connectivity associated with the particle packing density.ity.

• Journal of Powder Materials
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• v.26 no.6
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• pp.487-492
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• 2019

Titanium dioxide (TiO₂) is a typical inorganic material that has an excellent photocatalytic property and a high refractive index. It is used in water/air purifiers, solar cells, white pigments, refractory materials, semiconductors, etc.; its demand is continuously increasing. In this study, anatase and rutile phase titanium dioxide is prepared using hydroxyl and carboxyl; the titanium complex and its mechanism are investigated. As a result of analyzing the phase transition characteristics by a heat treatment temperature using a titanium complex having a hydroxyl group and a carboxyl group, it is confirmed that the material properties were different from each other and that the anatase and rutile phase contents can be controlled. The titanium complexes prepared in this study show different characteristics from the titania-formation temperatures of the known anatase and rutile phases. It is inferred that this is due to the change of electrostatic adsorption behavior due to the complexing function of the oxygen sharing point, which crystals of the TiO₆ structure share.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.9
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• pp.1233-1238
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• 2014

In this thesis, it is investigated the characteristics of Dye Sensitized Solar Cell (DSSC) according to variation of $TiO_2$ thickness (6, 12, 18, and $24{\mu}m$) and three distinct $TiO_2$ sintering temperatures (350, 450 and $550^{\circ}C$) by XRD, SEM, I-V and UV-Vis spectrophotometer. According to sintering temperature, $TiO_2$ was transformed into the anatase structure at $350^{\circ}C$, rutile structure at $550^{\circ}C$ and further into the two structure at $450^{\circ}C$. With increasing thickness up to $18{\mu}m$ and sintering temperature up to $450^{\circ}C$, respectively, the irradiance rate increased in the range of 9~26 percent and 2.80~5.10 percent. Whereas a further increase to $24{\mu}m$ and $550^{\circ}C$, the irradiance rate decrease in the range of 4~11 percent and 30~47 percent. The conversion efficiency increased in the range of 2.80~5.01 and 3.03~5.01 with increasing thickness up to $18{\mu}m$ and sintering temperature up to $450^{\circ}C$. By contrast, increase to $24{\mu}m$ and $550^{\circ}C$, the conversion efficiency decreased in the range of 3.31~5.01 and 2.80~3.89, respectively. The DSSC that thickness of $TiO_2$ were $18{\mu}m$ and sintered at $450^{\circ}C$ exhibited the most excellent characteristics, in which open-circuit voltage, short-circuit current, Fill Factor and conversion efficiency are 0.69 V, $11.4mA/cm^2$, 0.64 and 5.01%, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.1
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• pp.35-42
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• 2010

In this paper, three types of CNT/$TiO_2$ composite electrodes were prepared with different methods. The changes in XRD patterns showed that the Electrode A contained a mixed phase of anatase and rutile while the Electrode B and Electrode C contained a typical single and clear anatase crystal structure. From SEM micrographs, $TiO_2$ particles were adhered on the surface of the CNT network in the forms of small clusters. The results of chemical elemental analysis indicated that the main elements such as C, O and Ti were existed. The results demonstrated that the efficiency of photoelectrocatalytic (PEC) oxidation for methylene blue (MB) was higher than that of photocatalytic (PC) oxidation. There was a clear enhancement trend of the MB degradation using the prepared CNT/$TiO_2$ composite electrodes with an increase of applied potential. Finally, the prominent PEC activities of the CNT/$TiO_2$ composites could be attributed to combination effects of photo-degradation of $TiO_2$, electron assistant of CNT and function of applied potential.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.1
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• pp.3-7
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• 2009

Variation in oxidation behavior with heat treatment temperature is investigated for a Ni-Ti alloy using X-ray diffraction, DSC (differential scanning calorimetry) and Auger electron spectroscopy. And the effect of oxidation on transformation behavior and superelasticity is characterized. A cold-worked 50.6Ni-Ti alloy is oxidized at 300-$700^{\circ}C$ for 1 hr in the air atmosphere. With an increase in heating temperature, the structure of $TiO_2$ changes from amorphous (300 and $400^{\circ}C$) to anatase ($500^{\circ}C$), and to rutile ($700^{\circ}C$). Activation energy of oxidation for NiTi is measured to be 51 Kcal/mol when heating temperature is $500^{\circ}C$ or above. Since Ti reacts preferably with oxygen, Ni content increases between matrix and oxide, forming $Ni_{3}Ti$ compounds. The resultant of oxidation decreases significantly $M_s$ and $A_s$ temperature in the specimen oxidized at $900^{\circ}C$ with $B_2{\rightarrow}M$ transformation path. An extra is found on cooling between two peaks in the specimen with $B_2{\rightarrow}R{\rightarrow}M$ one which is oxidized at $900^{\circ}C$ and aged at $500^{\circ}C$. Oxidation deteriorates superelasticity due to formation of Ni-rich compound.

• Korean Journal of Materials Research
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• v.11 no.1
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• pp.61-66
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• 2001

$TiO_2$films for photocatalytic reaction were synthesized by anodizing process. The photocatalytic efficiencies of anodized $TiO_2$were evaluated by the rate of decomposition of aniline blue. The properties of photocatalysis on anodic $TiO_2$films have been observed, but the efficiencies of photocatalytic reaction depended on the conditions of films formation. The microstructure of the anodic film formed in $H_2SO_4$ solution differed from that of $TiO_2$films formed in $H_2SO_4+H_3PO_4$ solution. It has been shown that the appropriate applied-voltage for anodizing of titanium for photocatalysis was 180V in both aqueous solutions.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.1
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• pp.34-44
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• 2015

This study was initiated to remove free cyanide from wastewater using the process of photocatalytic oxidation. UV lamp has been extensively used as a light source in conventional photocatalytic oxidation, but numerous drawbacks of UV lamp have been raised so far. Thus, this study focused on evaluating the applicability of UV LED as an alternative light source to overcome the drawbacks of UV lamp. Furthermore, the effects of diverse operational parameters on the performance of process were investigated. The results demonstrated the applicability of UV LED as a substitute of UV lamp. Also, the results show that the performance of process was improved by the increase in the number of UV LEDs used. To acquire economic feasibility as well as high efficacy, however, it is required to determine the optimum number of UV LED prior to practical implementation of the process. Among the three types of photocatalysts (anatase, rutile, and Degussa P25) tested, the Degussa P25 showed the greatest performance, and it was proven that the process was not improved as much as the Degussa P25 through simple mixing of anatase and rutile without any pretreatment. In addition, the removal efficiency of free cyanide appeared to be increased with the decrease in the particle size of $TiO_2$ photocatalyst. Besides, the process was enhanced with injection of oxygen which is considered as a major electron acceptor in the photocatalytic oxidation.