• Bulletin of the Korean Chemical Society
• /
• v.34 no.8
• /
• pp.2461-2465
• /
• 2013

Pd-$Ce/{\gamma}-Al_2O_3-TiO_2$ catalysts were prepared by combined sol-gel and impregnation methods. Transmission electron microscopy, X-ray diffraction, $H_2$-temperature-programmed reduction, $O_2$-temperature-programmed desorption, and ethanol oxidation experiments were conducted to determine the properties of the catalysts. Addition of an optimal amount of Ce improved the performance of the $Pd/{\gamma}-Al_2O_3-TiO_2$ catalyst in promoting the complete oxidation of ethanol. The catalyst with 1% Ce exhibited the highest activity, and catalyzed complete oxidation of ethanol at $175^{\circ}C$; its selectivity to $CO_2$ reached 87%. Characterization results show that addition of appropriate amount of Ce could enrich the PdO species, and weaken the Pd-O bonds, thus enhancing oxidation ability of the catalyst. Meanwhile, the introduction of $CeO_2$ could make PdO better dispersed on ${\gamma}-Al_2O_3-TiO_2$, which is beneficial for the improvement of the catalytic oxidation activity.

• Journal of the Korean Society of Safety
• /
• v.21 no.2 s.74
• /
• pp.35-45
• /
• 2006

Cobalt catalysts for gas mask loaded on various supports such as $Al_{2}O_{3},\;TiO_{2}$, AC(activated carbon) and $SiO_{2}$ were used to examine influences of calcination temperatures and reaction temperatures for CO oxidation. $Co(NO_{3})_2{\cdot}6H_{2}O$ was used as cobalt precursor and the catalysts were prepared by incipient wetness impregnation. The catalysts were characterized using XRD, TGA/DTA, TEM, $N_{2}$ sorption, and XPS. For the catalytic activity, support was in the order of ${\gamma}-Al_{2}O_{3}>TiO_{2}>SiO_{2}>AC\;and\;Al_{2}O_{3}$. The catalytic activity at lower temperature than $80^{\circ}C$ showed that with the increase of reaction temperature, cobalt catalysts on ${\gamma}-Al_{2}O_{3},\;TiO_{2},\;AC\$ has the negative activation energy but that of $SiO_{2}$ was positive.

• Journal of the Korean institute of surface engineering
• /
• v.36 no.4
• /
• pp.329-333
• /
• 2003

The high-temperature oxidation behavior of Ti39Al-10V alloy that consisted primarily of $\beta$-Ti, ${\gamma}$-TiAl, and $\alpha_2$ $-Ti_3$Al phases was studied. The relatively thick and porous oxide scales formed consisted primarily of an outermost, thin TiO$_2$ layer, and an outer, thin $Al_2$$O_3$-rich layer, and an inner, very thick (TiO$_2$, $Al_2$$O_3$) mixed layer. Vanadium was present uniformly throughout the oxide scale. The formation and subsequent evaporation of V-oxides such as VO, $VO_2$, and $V_2$O$_{5}$ deteriorated oxidation resistance and scale adherence of the TiAl alloy significantly.y.

• Applied Chemistry for Engineering
• /
• v.4 no.1
• /
• pp.144-152
• /
• 1993

Immobilized polyethylene glycols onto metal oxides such as ${\gamma}-Al_2O_3$, ${\alpha}-Al_2O_3$, $SiO_2$ and $TiO_2$ were used as phase transfer catalysts for the room temperature synthesis of aniline from nitrobenzene and ironpentacarbonyl. The amount of attached PEG molecules increased with specific surface area of metal oxides. Among the immobilized catalysts tested PEG/${\gamma}-Al_2O_3$ showed the highest activity. The reaction rate increased with the chain length of PEG mole-cules and the aqueous NaOH concentration. Mechanistic study carried out using infrared spectrometer revealed that the role of PEG was to increase the formation of $HFe(CO)_4{^-}$ ion, which is known as active species, and its movement from aqueous to organic phase.

• Journal of the Korean Ceramic Society
• /
• v.38 no.7
• /
• pp.621-627
• /
• 2001

알루미나 졸에 평균 25nm의 TiO$_2$(Degussa P25) 광 촉매 분말을 분산하여 광촉매 코팅제를 제조하였다. 점도 약 24 cps를 가지 4.4 wt%의 알루미나 졸로부터 약 300nm 두께의 코팅막이 제조되었으며, 졸 점도의 증가에 비례하여 코팅막의 두께도 증가하였다. TiO$_2$광 촉매의 코팅용 바인더로 이용한 알루미나 졸의 결정형은 25~30$0^{\circ}C$에서 pseudo boehmite (AlOOH)이었으며, 50$0^{\circ}C$ 이상에서는 ${\gamma}$-Al$_2$O$_3$으로 전환되었다. AlOOH/TiO$_2$코팅막은 oleic acid와 humic acid에 대한 기상 및 수상 조건에서의 광 촉매 실험에서 우수한 유기물의 광분해 효능을 나타내었다. 아울러 EGI(Electro-Galvanized Iron)에 코팅된 AlOOH/TiO$_2$코팅막은 내식성 및 내지문성의 효과도 부수적으로 나타내었다.

• Proceedings of the Membrane Society of Korea Conference
• /
• 1994.04a
• /
• pp.58-58
• /
• 1994

슬립캐스팅법으로 제조한 튜브형 $\alpha$-알루미나 담체 (평균기공크기 = $0.1 \mum$)에 졸-겔 침지코팅(dipcoating) 또는 가압코팅 (pressurized coating) 법에 의하여 극미세입자 $\gamma$-AlOOH, $TiO_2, SiO_2$, 및 aluminosilicate diphasic 졸을 코팅한 후 300 ~ 500$\circ$C 에서 열처리하여 세라믹 복합막을 제조하였다. 복합막 전체에 대한 균열유무는 $N_2$ 기체투과율의 평균압력에 대한 의존성으로부터 평가하였으며, 한외여과 (ultrafiltration)에의 응용성을 규명하기 위하여 막의 재질 및 제조조건에 따른 polyethylene glycol (PEG) 수용액의 분획분자량 변화를 측정하였다. 합성 세라믹 복합막의 분획분자량 측정 결과 $SiO_2$의 경우 2,000 정도로 매우 우수하였으며 $\gamma-Al_2O_3, TiO_2$, 그리고 aluminosilcate 막들은 6,000 ~ 10,000 범위 값을 갖고 있었다. 또한 막의 기공크기 및 분획분자량을 제어하기 위한 방법으로서 $TiO_2$ 복합막을 300 ~ 700$\circ$C 에서 열처리하였으며 이들에 대한 분획분자량 변화를 비교 분석하였다.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.9
• /
• pp.3281-3289
• /
• 2011

The materials composed of the 3d series transition metals are introduced into the hydrocarbon steam-reforming reaction in order to enhance the $H_2$ production and abruptly depress the catalytic deactivation resulting from the strong sintering between the Ni component and the ${\gamma}-Al_2O_3$ support. The conventional impregnation method is used to synthesize the Ni/3d series metal/${\gamma}-Al_2O_3$ materials through the sequentially loading Ni source and the 3d series metal (Ti, V, Cr, Mn, Fe, Co, Cu, and Zn) sources onto the ${\gamma}-Al_2O_3$ support. The Mnloaded material exhibits a significantly higher reforming reactivity than the conventional Ni/${\gamma}-Al_2O_3$ and the other Ni/3d series metal/${\gamma}-Al_2O_3$ materials. Particularly the addition of Mn selectively improves the $H_2$ product selectivity by eliminating the formation of $CH_4$ and CO. The $H_2$ production is maximized at a value of 95% over Ni(0.3)/Mn(0.3)/${\gamma}-Al_2O_4$(1.0) with a butane conversion of 100% above $750^{\circ}C$ for up to 55 h.

• Progress in Medical Physics
• /
• v.29 no.4
• /
• pp.101-105
• /
• 2018

In this paper, a neutron moderation system for boron neutron capture therapy (BNCT) based on a $^{252}Cf$ neutron source is proposed. Different materials have been studied in order to produce a high percentage of epithermal neutrons. A moderator with a construction mixture of $AlF_3$ and Al, three reflectors of $Al_2O_3$, BeO, graphite, and seven filters (Bi, Cu, Fe, Pb, Ti, a two-layer filter of Ti+Bi, and a two-layer filter of Ti+Pb) is considered. The MCNPX simulation code has been used to calculate the neutron and gamma flux at the output window of the neutronic system. The results show that the epithermal neutron flux is relatively high for four filters: Ti+Pb, Ti+Bi, Bi, and Ti. However, a layer of Ti cannot reduce the contribution of ${\gamma}$-rays at the output window. Although the neutron spectra filtered by the Ti+Bi and Ti+Pb overlap, a large fraction of neutrons (74.95%) has epithermal energy when the Ti+Pb is used as a filter. However, the percentages of the fast and thermal neutrons are 25% and 0.5%, respectively. The Bi layer provides a relatively low epithermal neutron flux. Moreover, an assembly configuration of 30% $AlF_3+70%$ Al moderator/$Al_2O_3$ reflector/a two-layer filter of Ti+Pb reduces the fast neutron flux at the output port much more than other assembly combinations. In comparison with a recent model suggested by Ghassoun et al., the proposed neutron moderation system provides a higher epithermal flux with a relatively low contamination of gamma rays.

• Applied Chemistry for Engineering
• /
• v.10 no.8
• /
• pp.1129-1135
• /
• 1999

The reduction of $SO_2$ by CO over supported cobalt catalysts was investigated within the temperature range of $350{\sim}550^{\circ}C$, initial $SO_2$ concentration of 1000~10000 ppm, $CO/SO_2$ molar ratio of 1.0~3.0 and space velocity of $5000{\sim}15000h^{-1}$. Several types of supports such as ${\gamma}-Al_2O_3$, $TiO_2$ were tested. The $SO_2$ conversion and selectivity to elemental sulfur were investigated using a differential fixed bed reactor at atmospheric pressure. The catalyst prepared by wet impregration of 5 wt % cobalt on ${\gamma}-Al_2O_3$ showed $SO_2$ conversion higher than 90% and COS yield lower than 6% at temperature above $400^{\circ}C$. The optimum $CO/SO_2$ molar ratio was investigated as 2.0. At higher $CO/SO_2$ molar ratio, the $SO_2$ conversion became higher but the main product was COS. The effect of $SO_2$ concentration and space velocity over $SO_2$ conversion and COS yield was not appreciable in the experimental range. The activated cobalt phase was detected as $CoS_2$ and the $CoS_2$ phase unchanged even after reaction.

• Journal of Powder Materials
• /
• v.28 no.1
• /
• pp.31-37
• /
• 2021

This study explores reducing the oxygen content of a commercial Ti-48Al-2Cr-2Nb powder to less than 400 ppm by deoxidation in the solid state (DOSS) using Ca vapor, and investigates the effect of Ca vapor on the surface chemical state. As the deoxidation temperature increases, the oxygen concentration of the Ti-48Al-2Cr-2Nb powder decreases, achieving a low value of 745 ppm at 1100℃. When the deoxidation time is increased to 2 h, the oxygen concentration decreases to 320ppm at 1100℃, and the oxygen reduction rate is approximately 78% compared to that of the raw material. The deoxidized Ti-48Al-2Cr-2nb powder maintains a spherical shape, but the surface shape changes slightly owing to the reaction of Ca and Al. The oxidation state of Ti and Al on the surface of the Ti-48Al-2Cr-2Nb powder corresponds to a mixture of TiO2 and Al2O3. As a result, the peaks of metallic Ti and Ti suboxide intensify as TiO2 and Al2O3 in the surface oxide layer are reduced by Ca vapor deposition.