• Applied Chemistry for Engineering
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• v.7 no.3
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• pp.580-587
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• 1996

Synthesis of long fibrous $K_2Ti_4O_9$ was attempted to find a method to produce long fibrous $K_2Ti_6O_{13}$ and other derivatives and also phase transformation of $K_2Ti_4O_9$ synthesized was investigated. Long fibrous $K_2Ti_4O_9$ was succesively synthesized by the calcination reaction under the following reaction conditions ; reaction temperature of $1050^{\circ}C$, $TiO_2$ mole ratio to $K_2CO_3$ of 2.8 and reaction time of 3hrs, and scattering of calcined products for 10hrs with hot boiling water. $K_2Ti_4O_9$ showed lower structural stability under heat treatment and the structure of $K_2Ti_4O_9$ was converted to $K_2Ti_6O_{13}$ under heating temperature of over $250^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.36 no.7
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• pp.742-750
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• 1999

Nanosized TiO2 powders were synthesized using the chemical vapor conduensation (CVC) process with various precursor feeding rates (0.37 and 0.752 ml/min) and oxygen flow rates(1-2slm) conditions and powder characteristics were investigated in terms of formation of nanosized powder varying with the above processing conditions. For this study the main thermodynamic and fluid dynamic factors -supersaturation ratio collision frequency and residence time-were theoretically established and compared to the characteristics of formed TiO2 powder. The loosely combined anatase phase powders (including less than 3%of rutile phase) having 20-30nm crystallite size were obtained at overall conditions. The particle size and th degree of agglomeration for a precursor flow rate of 0.376 ml/min turn out to be smaller than for a flow rate of 0.742ml/min. And the decreasing of particles size and particle size distribution were observed with increasing oxygen flow rate as the residence time and collision frequency were reduced by increasing oxygen flow rate,. It appears that further scrutiny is needed to elucidate the influence of the individual thermodynamic and kinetic parameters mdependently.

• Journal of the Korean institute of surface engineering
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• v.36 no.1
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• pp.14-21
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• 2003

Thin films of ZrO$_2$ and TiO$_2$ were deposited on Si(100) substrates using RF magnetron sputtering technique. To study an influence of the sputtering parameters, systematic experiments were carried out in this work. XRD data show that the $ZrO_2$ films were mainly grown in the [111] orientation at the annealing temperature between 800 and $1000^{\circ}C$ while the crystal growth direction was changed to be [012] at above $1000^{\circ}C$. FT-IR spectra show that the oxygen stretching peaks become strong due to $SiO_2$ layer formation between film layers and silicon surface after annealing, and proved that a diffusion caused by either oxygen atoms of $ZrO_2$ layers or air into the interface during annealing. Different crystal growth directions were observed with the various deposition parameters such as annealing temperature, RF power magnitude, and added $O_2$ amounts. The growth rate of $TiO_2$ thin films was increased with RF power magnitude up to 150 watt, and was then decreased due to a sputtering effect. The maximum growth rate observed at 150 watt was 1500 nm/hr. Highly oriented, crack-free, stoichiometric polycrystalline $TiO_2$<110> thin film with Rutile phase was obtained after annealing at $1000^{\circ}C$ for 1 hour.

• Journal of Sensor Science and Technology
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• v.20 no.2
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• pp.82-89
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• 2011

Ruthenium(Ru)-doped $TiO_2$ nanofibers were prepared using electrospun Ru-$TiO_2$/poly(vinyl acetate) (PVAc) fibers and subsequent annealing for 1 h at temperatures in the range of $500^{\circ}C$ to $1000^{\circ}C$ in air. The properties of the Ru-$TiO_2$ fibers were characterized as a function of the Ru content and calcination temperature using X-ray diffraction, thermal gravimetry with differential scanning calorimetry, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and viscometer, pycnometer and dynamic tensiometer measurements. Although the diameter of the fiber decreased slightly with increasing calcination temperature, no dramatic changes were observed with respect to the ruthenium content. The XRD and FT-IR results revealed that anatase phase and ruthenium metal began to be formed after calcination at temperatures above $500^{\circ}C$. Anatase and rutile phases and ruthenium metal coexisted in the fibers calcined above $600^{\circ}C$. No anatase phase was detected in the fibers containing ruthenium when they were calcined at $1000^{\circ}C$. The morphology of the fibers changed from smooth and uniform to porous with increasing temperature. The experimental results suggest that the calcination temperature and Ru content were influential in determining the morphology and structure of the fibers.

• Korean Journal of Materials Research
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• v.18 no.10
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• pp.515-520
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• 2008

We fabricated 10 nm-$TiO_2$ thin films for DSSC (dye sensitized solar cell) electrode application using ALD (atomic layer deposition) method at the low temperatures of $150^{\circ}\;and\;250^{\circ}$. We characterized the crosssectional microstructure, phase, chemical binding energy, and absorption of the $TiO_2$ using TEM, HRXRD, XPS, and UV-VIS-NIR, respectively. TEM analysis showed a 10 nm-thick flat and uniform $TiO_2$ thin film regardless of the deposition temperatures. Through XPS analysis, it was found that the stoichiometric $TiO_2$ phase was formed and confirmed by measuring main characteristic peaks of Ti $2p^1$, Ti $2p^3$, and O 1s indicating the binding energy status. Through UV-VIS-NIR analysis, ALD-$TiO_2$ thin films were found to have a band gap of 3.4 eV resulting in the absorption edges at 360 nm, while the conventional $TiO_2$ films had a band gap of 3.0 eV (rutile)${\sim}$3.2 eV (anatase) with the absorption edges at 380 nm and 410 nm. Our results implied that the newly proposed nano-thick $TiO_2$ film using an ALD process at $150^{\circ}$ had almost the same properties as thsose of film at $250^{\circ}$. Therefore, we confirmed that the ALD-processed $TiO_2$ thin film with nano-thickness formed at low temperatures might be suitable for the electrode process of flexible devices.

• Nano
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• v.13 no.10
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• pp.1850124.1-1850124.12
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• 2018

$TiO_2$ films were deposited from oxygen/titanium tetraisopropoxide (TTIP) plasmas at low temperature by Helicon-PECVD at floating potential ($V_f$) or substrate self-bias of -50 V. The influence of titanium precursor partial pressure on the morphology, nanostructure and optical properties was investigated. Low titanium partial pressure ([TTIP] < 0.013 Pa) was applied by controlling the TTIP flow rate which is introduced by its own vapor pressure, whereas higher titanium partial pressure was formed through increasing the flow rate by using a carrier gas (CG). Then the precursor partial pressures [TTIP+CG] = 0:027 Pa and 0.093 Pa were obtained. At $V_f$, all the films exhibit a columnar structure, but the degree of inhomogeneity is decreased with the precursor partial pressure. Phase transformation from anatase ([TTIP] < 0.013 Pa) to amorphous ([TTIP+CG] = 0:093 Pa) has been evidenced since the $O^+_2$ ion to neutral flux ratio in the plasma was decreased and more carbon contained in the film. However, in the case of -50 V, the related growth rate for different precursor partial pressures is slightly (~15%) decreased. The columnar morphology at [TTIP] < 0.013 Pa has been changed into a granular structure, but still homogeneous columns are observed for [TTIP+CG] = 0:027 Pa and 0.093 Pa. Rutile phase has been generated at [TTIP] < 0:013 Pa. Ellipsometry measurements were performed on the films deposited at -50 V; results show that the precursor addition from low to high levels leads to a decrease in refractive index.

• Korean Chemical Engineering Research
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• v.44 no.4
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• pp.375-381
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• 2006

In this sturdy, spherical activated carbon(SPAC) contained $TiO_2$ was made by ion-exchanged treatment and heat treatment for applying fluidizing bed system. The ion-exchange resin was treated by $TiCl_3$ aqueous solution. The treated resin and raw resin were heat-treated under nitrogen condition to convert into Ti-SPAC. During the heat-treatment, burn-off weight amounts and the element were measured by means of TGA and TGA/MS, individually. The physicochemical properties of Ti-SPAC was characterized by means of XRD, SEM, EDS, BET, EPMA, ESR, intensity and titanium content. The Ti-SPAC had spherical shape with diameter size about $350{\mu}m{\sim}400{\mu}m$ and $617m^2/g$ specific surface area. Structure of $TiO_2$ in Ti-SPAC was anatase and rutile form. Also, $TiO_2$ on SPAC were found that the $TiO_2$ were uniformly distributed through EPMA analysis. Moreover, the Ti-SPAC showed indirect photocatalyst activity estimation through ESR analysis, characteristics of photocatalyst potentially. Over all results, Ti-SPAC was used in fluidizing bed UV/photocatalyst system to remove HA(Humic Acid). That results were HA removal efficiency was about 70％ and Ti-SPAC intensity was preserved during reaction. Ti-SPAC showed practical possibility as photocatalyst in fluidizing bed system.

• Applied Chemistry for Engineering
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• v.19 no.3
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• pp.351-356
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• 2008

Titania nanoparticles were prepared by controlled hydrolysis of titanium tetraisopropoxide (TTIP) in water-in-oil (W/O) and microemulsion stabilized with a nonionic surfactant, N P-10 (Polyoxyethylene Nonylphenol Ether: $C_9H_{19}C_6H_4(OCH_2CH_2)_{10}OH$)). The nanosized particles prepared in W/O microemulsion were characterized by FT-IR, TEM, XRD, TGA, and DTA. In addition, the photocatalytic degradation of p-nitrophenol has been studied by using a batch reactor in the presence of UV light in order to compare the photocatalytic activity of prepared nanosized titania. The nanaosized titania particles calcined at $300{\sim}600^{\circ}C$ showed an anatase structure, but it transformed to a rutile phase above $700^{\circ}C$ of calacination temperature. With an increase of $W_o$ ratio, the crystallite size increased but photocalytic activity decreased. The titania synthesized at $W_o=5$, R = 2, and calcined at $400{\sim}500^{\circ}C$ showed the highest activity on the photocatalytic degradation of p-nitrophenol.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.413-418
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• 2021

Nano-materials with high effective surface areas have been applied to functional materials, such as high sensitive gas sensors and biosensors and high-efficiency catalytic materials. In this study, titanate sheets with a 3D nano-wall-like structure, high effective surface area, were synthesized vertically to the substrate by a chemical bath deposition (CBD) process using a Ti sheet and urea. The synthesis temperature and synthesis duration time were controlled to the optimal conditions of a 3D nano-wall-like structure in the CBD process. The synthesized ammonium titanate sheets with a 3D nano-wall-like structure were annealed in air to transform to TiO2 with a 3D nano-wall-like structure for various applications. As a result, the optimal temperature in the CBD process for the synthesis of a uniform ammonium titanate sheet with a 3D nano-wall-like structure was 90 ℃. TiO2 with a 3D nano-wall-like structure was obtained from the ammonium titanate sheet with a 3D nano-wall-like structure by annealing above 550 ℃ for three hours. In particular, TiO2 with a 3D nano-wall-like structure with a dominant rutile phase was obtained by post-annealing at 700 ℃. On the other hand, damage to the 3D nano-wall edge was observed after 700 ℃ post-annealing.

• Analytical Science and Technology
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• v.19 no.6
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• pp.460-467
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• 2006

Carbon-coated $TiO_2$ was prepared by $CCl_4$ solvent mixing method with different heat treatment temperature (HTT). Since the carbon layers derived from pitch on the $TiO_2$ particles were porous, the carbon-coated $TiO_2$ sample series showed a good adsorptivity and photo decomposition activity. The BET surface area was decreased by the increasing of the heat treatment temperature. The SEM results present to the characterization of surface texture on the carbon-coated $TiO_2$ sample and carbon distributions on the surfaces for all the materials used. The main elements of C, O and Ti were shown from EDX spectra. And the quantity of these elements is very rich in the samples. From XRD data, the pristine anatase peaks were observed in the X-ray diffraction patterns for the carbon-coated $TiO_2$ at the different HTTs. However, the rutile peaks were observed for the carbon-coated $TiO_2$ at HTT of 1073 K and 1123 K. Finally, the excellent photocatalytic activity of carbon-coated $TiO_2$ with UV-vis spectra between absorbance and time could be attributed to the homogeneous coated carbon on the external surface and structural phase transform, and the photocatalytic activity was decreased by the increasing of the HTT.