• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.288-288
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• 2013

We report the catalytic activity of Au/$TiO_2$ and Pt/$TiO_2$ nanocatalysts under CO oxidation fabricated by arc plasma deposition (APD), which is a facile dry process with no organic materials involved. Using APD, the catalyst nanoparticles were well dispersed on $TiO_2$ powder with an average particle size (2~4 nm) well below that of nanoparticles prepared by the sol-gel method (10 nm). We found that the average particle size of the dispersed gold nanoparticles can be controlled by changing the plasma discharge voltage of APD. Accordingly, the amount of loaded gold on the $TiO_2$ powder increased with increasing discharge voltage, but the specific surface area of the Au/$TiO_2$ samples decreased. As for catalytic reactivity, Au/$TiO_2$ showed a higher catalytic activity than Pt/$TiO_2$ in CO oxidation. The catalytic activity of the Au/$TiO_2$ samples showed size dependence where higher catalytic activity occurred on smaller gold nanoparticles. The study suggests that APD is a simple way to fabricate catalytically active nanocatalysts.

• 한국분말재료학회지
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• 제27권5호
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• pp.381-387
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• 2020

In this work, TiO₂ 3D nanostructures (TF30) were prepared via a facile wet chemical process using ammonium hexafluorotitanate. The synthesized 3D TiO₂ nanostructures exhibited well-defined crystalline and hierarchical structures assembled from TiO₂ nanorods with different thicknesses and diameters, which comprised numerous small beads. Moreover, the maximum specific surface area of TiO₂ 3D nanostructures was observed to be 191 ㎡g^-1, with concentration of F ions on the surface being 2 at%. The TiO₂ 3D nanostructures were tested as photocatalysts under UV irradiation using Rhodamine B solution in order to determine their photocatalytic performance. The TiO₂ 3D nanostructures showed a higher photocatalytic activity than that of the other TiO₂ samples, which was likely associated with the combined effects of a high crystallinity, unique features of the hierarchical structure, a high specific surface area, and the advantage of adsorbing F ions.

• 한국세라믹학회지
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• 제37권10호
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• pp.938-943
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• 2000

TiCl$_4$, 물 및 1-propanol의 혼합용액으로부터 미립 TiO$_2$분말 제조시, 1-propanol과 물의 부피비, 반응온도, 반응유지시간 및 TiCl$_4$mole 농도에 따른 분말 특성 및 결정상 생성에 대해 조사하였다. 반응온도가 3$0^{\circ}C$ 이상일 때 Ti 수화물의 초기 침전이 생성되었고 반응온도가 TiCl$_4$mole 농도가 증가함에 따라 입자크기는 증가하였고 $600^{\circ}C$ 하소시 1-propanol과 물의 부피비가 2보다 크고 반응온도가 7$0^{\circ}C$보다 낮을 때 주결정상은 anatase였다. 입자크기가 미세하고 입자크기 분포가 좁은 범위를 갖는 조건은 1-propanol과 물의 부피비가 2, 반응온도가 7$0^{\circ}C$, TiCl$_4$mole 농도가 0.2 mole/ι일 때였으며, 결정상의 생성은 1-propanol과 물의 부피비가 2, 반응온도가 3$0^{\circ}C$ 이상일 때 anatase에서 rutile로 전이하는 온도가 높아졌다. 이와 같은 반응인자에 따른 효과는 용매의 유전상수, 티타니아의 용해도, 입자의 표면전위 등의 효과와 관계가 있었다.

• 한국세라믹학회지
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• 제39권11호
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• pp.1108-1112
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• 2002

산화물 제어봉 물질로서 $Dy_xTi_yO_z$ 소결체를 powder process에 의해 제조하였다. $Dy_2O_3+TiO_2$ 혼합분말의 소결성과 고용체의 상을 TMA와 XRD로써 각각 분석하였으며, 소결체의 비열과 열확산계수를 측정하여 열전도도를 구하였다. $Dy_xTi_yO_z$에서 Dy의 함량에 따라 소결성과 밀도가 변하였고 $3\;g\;Dy/cm^3\;Dy_xTi_yO_z$의 경우 $1580{\circ}C$의 소결온도에서 용융이 일어났다. $4.00\;g\;Dy/cm^3$ 소결체에는 $Dy_2TiO_5+Dy_2Ti_2O_7$의 두 상이 존재하며 $4.54\;g\;Dy/cm^3$의 경우 $Dy_2TiO_5$의 단일 상만이 존재하는 결과를 보였다. $Dy_xTi_yO_z$의 열전도도는 $25~600{\circ}C$ 범위에서 온도에 따라 큰 변화가 없으며 $1600{\circ}C$ 소결체가 1.69∼1.78 W/mK, 1550$^{\circ}C$ 소결체의 경우에는 1.49~1.55 W/mK이었다.

• 한국표면공학회지
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• 제40권3호
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• pp.125-130
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• 2007

Many fundamental studies have been carried out regarding waste water and hazardous gas treatment technology using the photolysis effect of $TiO_2$. However, photolysis of both organic and organic-inorganic binders immobilizing $TiO_2$ makes permanent use impossible. In this study we manufactured a catalytic electrode by nickel-$TiO_2$ composite plating in order to immobilize $TiO_2$. The surface properties according to the current density changes of cathode and concentration changes of $TiO_2$ powder in nickel plating bath has been analysed with EDX, XRF, SEM, Raman spectrometer etc. The characterization of the catalytic electrode in decomposition of organic compound has been obtained by using UV-Visible spectrophotometer through analysing concentration changes of methyl orange solution containing the catalytic electrode vs. time with projecting UV-light in the solution. The study shows that a catalytic electrode of nickel-$TiO_2$ composite plating with high-efficiency in decompostion of organic compound has been formed under high concentration of $TiO_2$ powder and low current density of cathode.

• 한국분말재료학회지
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• 제17권3호
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• pp.216-222
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• 2010

Self-standing $TiO_2$ nanotube arrays were fabricated by potentiostatic anodic oxidation method using pure Ti foil as a working electrode and ethylene glycol solution as electrolytes with small addition of $NH_4F$ and $H_2O$. The influences of anodization temperature and time on the morphology and formation of $TiO_2$ nanotube arrays were investigated. The fabricated $TiO_2$ nanotube arrays were applied as a photoelectrode to dye-sensitized solar cells. Regardless of anodizing temperature and time, the average diameter and wall thickness of $TiO_2$ nanotube show a similar value, whereas the thickness show a different trend with reaction temperature. The thickness of $TiO_2$ nanotube arrays anodized at $20^{\circ}C$ and $30^{\circ}C$ was time-dependent, but on the other hand its at $10^{\circ}C$ are independent of anodization time. The conversion efficiency is low, which is due to a morphology breaking of the $TiO_2$ nanotube arrays in manufacturing process of photoelectrode.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 학술대회 논문집 전문대학교육위원
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• pp.167-170
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• 2006

$TiO_{2}-Nb_{2}O_{5}$ sol was prepared using sol-gel method. DTA properties of gel powder had endothermic reaction due to evaporation of propanol and water about $78^{\circ}C$, had exothermic reaction due to propanol combustion about $290^{\circ}C$ and had exothermic reaction due to changing of $TiO_2$ phase about $640^{\circ}C$. Capacitance of thin films increased according to increasing relative humidity, whereas it decreased according to increasing measured frequency.

• 한국분말재료학회지
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• 제24권1호
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• pp.41-45
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• 2017

The effects of the heat treatment temperature and of the atmosphere on the dehydrogenation and hydrogen reduction of ball-milled $TiH_2-WO_3$ powder mixtures are investigated for the synthesis of Ti-W powders with controlled microstructure. Homogeneously mixed powders with refined $TiH_2$ particles are successfully prepared by ball milling for 24h. X-ray diffraction (XRD) analyses show that the powder mixture heat-treated in Ar atmosphere is composed of Ti, $Ti_2O$, and W phases, regardless of the heat treatment temperature. However, XRD results for the powder mixture, heat-treated at $600^{\circ}C$ in a hydrogen atmosphere, show $TiH_2$ and TiH peaks as well as reaction phase peaks of Ti oxides and W, while the powder mixture heat-treated at $900^{\circ}C$ exhibits only XRD peaks attributed to Ti oxides and W. The formation behavior of the reaction phases that are dependent on the heat treatment temperature and on the atmosphere is explained by thermodynamic considerations for the dehydrogenation reaction of $TiH_2$, the hydrogen reduction of $WO_3$ and the partial oxidation of dehydrogenated Ti.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.286-287
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• 2006

Barium titanate ($BaTiO_3$) glycolate particles were synthesized at temperature as low as $100^{\circ}C$ through glycothermal reaction by using $Ba(OH)_2{\cdot}8H_2O$ and amorphous titanium hydrous gel as precursors and ethylene glycol as solvent. The particle size and morphology of $BaTiO_3$ glycolate powders can be controlled by varying the reaction conditions such as the reaction temperature and Ba:Ti molar ratio of starting precursors. After glycothermal treatment at $220^{\circ}C$ for 24 h in 1.25:1(Ba:Ti), the average particle size of the $BaTiO_3$ glycolate powder was about 200-400 nm and low agglomeration. $BaTiO_3$ powders were formed by heat-treating the glycolate powder in air at $500-1000^{\circ}C$. As a result, the size of $BaTiO_3$ crystallites changed from around 50-300 nm. It is also demonstrated that the size and shape of $BaTiO_3$ particles investigated as a function of calcination temperature. The $BaTiO_3$ particles obtained from optimum synthesis condition were pressed, sintered and measured for the dielectric property. The $BaTiO_3$ ceramics sintered at $1250^{\circ}C$ for 2 h had 98 % of theoretical density. The ceramics have an average grain size of about $1\;{\mu}m$ and displays the high dielectric constant (~3100) and low dielectric loss (<0.1) at room temperature.

• 한국분말재료학회지
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• 제31권3호
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• pp.255-262
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• 2024

Nano-oxide dispersion-strengthened (ODS) superalloys have attracted attention because of their outstanding mechanical reinforcement mechanism. Dispersed oxides increase the material's strength by preventing grain growth and recrystallization, as well as increasing creep resistance. In this research, atomic layer deposition (ALD) was applied to synthesize an ODS alloy. It is useful to coat conformal thin films even on complex matrix shapes, such as nanorods or powders. We coated an Nb-Si-based superalloy with TiO₂ thin film by using rotary-reactor type thermal ALD. TiO₂ was grown by controlling the deposition recipe, reactor temperature, N₂ flow rate, and rotor speed. We could confirm the formation of uniform TiO₂ film on the surface of the superalloy. This process was successfully applied to the synthesis of an ODS alloy, which could be a new field of ALD applications.