• Resources Recycling
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• v.29 no.3
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• pp.3-10
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• 2020

The chlorination kinetics of synthetic rutile prepared by selective chlorination of ilmenite with Cl₂ and CO gas mixture were studied in a fluidized bed. Th e effects of reaction temperature, reaction time, and the ratio of Cl₂ and CO partial pressure ($p_{Cl_2}/p_{CO}$) on the conversion rate of TiCl₄ were investigated. The conversion rate of TiC₄ was low under the high $p_{Cl_2}/p_{CO}$ conditions. Moreover, it was considered that the partial pressure of CO gas was more effective than that of Cl₂ gas when comparing the stoichiometric conversion rate and experimental results of high CO partial pressure. Considering the porous structure of particles, the rate controlling step of the chlorination of synthetic rutile was determined to be chemical reaction and the activation energy was calculated as 53.77 kJ/mol.

• Korean Membrane Journal
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• v.3 no.1
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• pp.69-74
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• 2001

Films of TiO$_2$/SiO$_2$ were deposited on the inner surface of the porous glass support tubes by decomposition of tetraisopropyl titanate (TIPT) and tetraethyl orthosilicate (TEOS) at atmospheric pressure. Dense and hydrogen -permselective membranes were formed at 400-600$\^{C}$. The permeation rates of H$_2$ through the membrane at 600$\^{C}$ were 0.2-0.4 ㎤(STP)/min-㎠ atm and H$_2$:N$_2$permeation ratios were above 1000. The permeation properties of the membranes were investigated at various deposition temperatures and TIPT/TEOS concentrations. Decomposition of TIPT alone at temperatures above 400$\^{C}$ produced porous crystalline TiO$_2$ films and they were not H7-selective. Decomposition of TEOS produced H$_2$-permeable SiO$_2$ films at 400-600$\^{C}$ but film deposition rate was very low. Addition of TIFT to the TEOS stream significantly accelerated the deposition rate and produced highly H$_2$-selective films. Increasing the TIPT/TEOS concentration ratio increased the deposition rate. The TiO$_2$/SiO$_2$ membranes formed at 600 $\^{C}$ have the permeation properties comparable to those of SiO$_2$ membranes produced from TEOS.

• Korean Journal of Metals and Materials
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• v.50 no.2
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• pp.164-170
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• 2012

Nanotubular structure formation on the Ti-6Al-4V and Ti-Ta alloy surfaces by electrochemical methods has been studied using the anodizing method. A nanotube layer was formed on Ti alloys in 1.0 M $H_3PO_4$ electrolyte with small additions of $F^-$ ions. The nanotube nucleation and growth of the ${\alpha}$-phase and ${\beta}$-phase appeared differently, and showed different morphology for Cp-Ti, Ti-6Al-4V and Ti-Ta alloys. In the ${\alpha}$-phase of Cp-Ti and martensite ${\alpha}^{\prime}$ and in the ${\alpha}^{{\prime}{\prime}}$ and ${\beta}$-phase of the Ti-Ta alloy, the nanotube showed a clearly highly ordered $TiO_2$ layer. In the case of the Ti-Ta alloy, the pore size of the nanotube was smaller than that of the Cp-Ti due to the ${\beta}$-stabilizing Ta element. In the case of the Ti-6Al-4V alloy, the ${\alpha}$-phase showed a stable porous structure; the ${\beta}$-phase was dissolved entirely. The nanotube with two-size scale and high order showed itself on Ti-Ta alloys with increasing Ta content.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.961.1-961.1
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• 2006

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.681-681
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• 2006

• Applied Chemistry for Engineering
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• v.28 no.6
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• pp.601-606
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• 2017

One-dimensional nanostructured metal oxide can be formed through an anodic oxidation, which is a typical technique of metal surface treatment. Studies on $TiO_2$ nanotubes have been widely carried out with increasing interests in $TiO_2$, which has an excellent functionality among various metal oxides. The present article reviews the principles of formation of $TiO_2$ nanotubes, which have been studied so far. In particular, the article discussed the equilibrium relationship between the oxide formation and etching, which is a key parameter of $TiO_2$ nanotube growth, and the formation of the porous structure. Furthermore, morphological considerations of $TiO_2$ nanotubes according to electrolyte conditions will be explained to the researchers who will study the application of $TiO_2$ nanotubes formed through the anodic oxidation in the future.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1098-1101
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• 1995

NbTi thin films were prepared on Si wafer and Cu substrate by rf magnetron sputtering in the range of sputtering pressure $3{\times}10^{-2}$torr to $3{\times}10^{-4}$torr at room temperature. The influence of sputtering pressure and substrate type on crystallographic orientation and morphology of NbTi thin films was investigated by using X-ray diffraction(XRD) and scanning electron microscopy(SEM), respectively. And the effect of crystallographic orientation and morphology of NbTi film on electromagnetic behaviors was estimated by measuring critical current in various applied magnetic field. The film morphology changed from porous structure consisting of tapered crystallites to densely deposited film decreasing with sputtering pressure. The change of crystallographic orientation with the sputtering pressure and rf power was calculated from the texture coefficient of(002) plane based on XRD patterns. It was found that a change of texture coefficient of(002) plane increased with decreasing sputtering pressure. From observation of critical current in various applied magnetic field, we have identified that the change of critical current abruptly decrease applying with magnetic field and NbTi film produced at high sputtering pressure does not exhibit superconductivity but at low sputtering pressure shows superconductivity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4925-4929
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• 2015

Dye-sensitized solar cell(DSSC) has aroused intense interest owing to its competitive price and stabilized properties than Si based solar cells. Recently, many studies have been reported on the DSSC, especially development of a transparent conductive oxide-less dye-sensitized solar cell(TCO-less DSSC). In this paper, a thick and porous Ti electrode for low cost DSSC developed its properties. To estimate the Ti electrode, the films are tested FESEM and J-V evaluation method. An increase in Ti thickness from 50 nm to 200 nm mainly affects the fill factor without noticeably changing the photocurrent density. It was confirmed that optimal DSSC efficiency was obtained at Ti 150 nm.

• Journal of the Korean Ceramic Society
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• v.55 no.3
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• pp.239-243
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• 2018

Up to now, microstructure changes of photocatalysts have been studied to improve photocatalytic activity. Especially, to improve the adsorption of reactants and reactive sites, porous and fine crystal structures have received much attention because of their large specific surface area. In this study, $TiO_2$ nanotubes were synthesized by hydrothermal method using $TiO_2$ nanoparticles; nanotubes were evaluated by oxidized methylene blue reduction test. Using synthesized $TiO_2$ nanotubes, results of TEM showed that the $TiO_2$ nanoparticles were changed into folding sheets and nanotubes. XRD results showed that the peaks of the nanoparticles almost disappeared and only the rutile (110) and anatase (200) peaks were observed. Comparison of photocatalytic properties of nanoparticles and nanotube structures was performed by measuring the UV-vis absorbance with reducing oxidized methylene blue. As a result, the reduction rate of nanotubes was found to be $0.24{\mu}mol/s$, which was 2.6 times higher than the rate of reduction of nanoparticles.

• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.227-233
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• 2016

In order to make a highly ordered three-dimensional porous structure of titania ceramics, porogen beads of PS [Polystyrene] and PMMA [poly(methylmetacrylate)] were prepared by emulsion polymerization using styrene monomer and methyl methacrylate monomer, respectively. The uniform beads of PS or PMMA latex were closely packed by centrifugation as a porogen template for the infiltration of titanium butoxide solution. The mixed compound of PS or PMMA with titanium butoxide was dried and the dry compacts were calcined at $450^{\circ}C-750^{\circ}C$ according to the firing schedule to prepare micro- and meso- structures of polycrystalline titania with monodispersed porosity. Inorganic frameworks composed of $TiO_2$ were formed and showed a three Dimensionally Ordered Microstructure [3DOM] of $TiO_2$ ceramics. The pulverized particles of the $TiO_2$ ceramic skeleton were characterized using XRD analysis. A monodispersed crystalline micro-structure with micro/meso porosity was observed by FE-SEM with EDX analysis. The 3DOM $TiO_2$ skeleton showed opalescent color tuning according to the direction of light.