• Journal of the Korean Ceramic Society
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• v.43 no.10 s.293
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• pp.595-600
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• 2006

The preparation of $\beta$-SiAlON powder by SHS in the system of $Si-Al-SiO_2-NH_4F(\beta-Si_3N_4)$ was investigated in this study. In the preparation of SiAlON powder, the effect of gas pressure, compositions such as Si, $NH_4F$, \beta-Si_3N_4$ and additive in mixture on the reactivity were investigated. At 50 atm of the initial inert gas pressure in reactor, the optimum composition for the preparation of pure $\beta$-SiAlON was $3Si+Al+2SiO_2+NH_4F$. The $\beta$-SiAlON powder synthesized in this condition was a single phase $\beta$-SiAlON with a rod like morphology.

• Bulletin of the Korean Chemical Society
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• v.30 no.1
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• pp.107-113
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• 2009

This study investigated the decomposition activities of toluene on 10 mol% Al-W-incorporated mesoporous titano (15 mol %) silicates. The mesopore sizes observed in the transmission electron microscopy images ranged from 2.0 to 5.0 nm, and the pores were irregular on the addition of 10 mol% Al or W ions, but changed to regular hexagonal forms with the simultaneous additions of Al and W. The X-ray photon spectroscopy results showed a shift of the special peak for Ti2p in Al-incorporated mesoporous titanosilicates to a stronger binding energy compared to those of mesoporous titanosilicates and Al-incorporated mesoporous titanosilicates. Three O1s peaks in the spectra of the Al and W coexisted samples were observed at 530.5 and 531.7, 533, and 533.7eV, which were assigned to $Ti-Os\;in\;TiO_2\;and\;Ti_2O_3,\;Si-O\;in\;SiO_2\;and\;Al-O\;in\;Al_2O_3$, respectively. The toluene molecules desorbed at lower temperatures over W-incorporated mesoporous titanosilicates, and the amounts of toluene desorbed were also small; however, Al-incorporated mesoporous titanosilicates adsorbed much more toluene, particular over $Al_7.5-W_2.5-Ti_15-Si_75$. The photocatalytic decomposition of toluene was more enhanced over $Al_7.5-W_2.5-Ti_15-Si_75$ than over Al- or W-incorporated mesoporous titanosilicates only.

• Korean Journal of Materials Research
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• v.25 no.8
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• pp.391-397
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• 2015

NiO catalysts/$Al_2O_3$/FeCrAl alloy foam for hydrogen production was prepared using atomic layer deposition (ALD) and subsequent dip-coating methods. FeCrAl alloy foam and $Al_2O_3$ inter-layer were used as catalyst supports. To improve the dispersion and stability of NiO catalysts, an $Al_2O_3$ inter-layer was introduced and their thickness was systematically controlled to 0, 20, 50 and 80 nm using an ALD technique. The structural, chemical bonding and morphological properties (including dispersion) of the NiO catalysts/$Al_2O_3$/FeCrAl alloy foam were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy and scanning electron microscopy-energy dispersive spectroscopy. In particular, to evaluate the stability of the NiO catalysts grown on $Al_2O_3$/FeCrAl alloy foam, chronoamperometry tests were performed and then the ingredient amounts of electrolytes were analyzed via inductively coupled plasma spectrometer. We found that the introduction of $Al_2O_3$ inter-layer improved the dispersion and stability of the NiO catalysts on the supports. Thus, when an $Al_2O_3$ inter-layer with a 80 nm thickness was grown between the FeCrAl alloy foam and the NiO catalysts, it indicated improved dispersion and stability of the NiO catalysts compared to the other samples. The performance improvement can be explained by optimum thickness of $Al_2O_3$ inter-layer resulting from the role of a passivation layer.

• Journal of the Korean institute of surface engineering
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• v.33 no.4
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• pp.281-288
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• 2000

To understand the effect of Fe on the oxidation behavior of TiAl alloys, TiAl-(2, 4, 6at% )Fe were oxidized at 800 and 90$0^{\circ}C$ in air. The oxidation resistance of TiAl-Fe alloys increased with increasing an iron content. The scales formed consisted of an outer $TiO_2$ layer, an intermediate $A1_2$$O_3$ layer, and an inner mixed ($TiO_2$+$A1_2$$O_3$) layer, being similar to other common TiAl alloys. But, the scales formed on TiAl-Fe alloys were generally thin compared to those formed on pure TiAl, and contained dissolved iron. Below the oxide scale, an oxygen affected zone was formed. This beneficial effects of Fe on increasing the oxidation resistance and scale adherence of TiAl alloys were attributed to the refinement of oxide grains, increased scale adherence and the enhanced alumina-forming tendency.

• Journal of the Korean Ceramic Society
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• v.32 no.2
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• pp.227-233
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• 1995

By using homestyle microwave oven, Al-Al2O3 powder mixture could be oxidized and sintered into Al2O3 body. The differences in powder characteristics among the differently processed raw materials affect the oxidation and sintering behaviours, and these effects were more pronounced in case of microwave oven than of conventional furnace. Al-Al2O3 powder mixture was oxidized and sintered within 2hrs, which could save both processing time and energy.

• Journal of the Korean Ceramic Society
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• v.31 no.7
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• pp.759-766
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• 1994

The effect of additives on properties of unfired Al2O3-C bricks were investigated. The increase of carbon content and the addition of MgO or spinel improved the resistances against spalling and corrosion of unfired Al2O3-C bricks. Also, the oxidation resistance of unfired Al2O3-C brick was increased by adopting complex metals of Al and Si in spite of the increase of carbon content.

• Korean Journal of Materials Research
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• v.14 no.8
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• pp.547-551
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• 2004

The sulfidation behaviour of Fe-XAl-0.3Y(X=5, 10, 14, 25 $wt.\%$) alloys was investigated at 1123 K in $H_2/H_{2}S$ gas atmosphere for $1\sim24$ hrs using SEM/EDX, XRD and EPMA. The weight changes of Fe-XAl-0.3Y alloys followed the parabolic rate law, Sulfidation rates of iron aluminide alloys with high Al content were one-twentieth lower than that of 5Al alloys. This is due to the formation of protective $Al_{2}O_3$ oxides on the surface of 10Al, 14Al and 25Al alloys. By calculating partial pressure of impurity oxygen contained $H_2/H_{2}S$ gas, the $Al_{2}O_3$ oxides formation could be explained using Fe-Al-S-O thermodynamic stability diagram. The sulfidation product scales of the 5Al alloy showed that thick iron sulfide scale(FeS) containing porosities formed during early stages of sulfidation. With continued sulfidation, aluminum sulfide was formed at the alloy/scale interface.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.3
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• pp.269-277
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• 1995

Ultrafine TEX>$Al_2O_3$ powders were prepared from $AlCl_3$ and $Al_2(SO_4)_3$3 by using inductively coupled plasma (lCP) of ultrahigh temperature (above 5000 K) in heat source. The prepared $Al_2O_3$ powders had ${\alpha} - group ({\alpha}, {wdelta} ;and; {\theta})$ phase, a narrow size distribution and around 20 nm in meansize. It could be suggested that gas - solid reaction growth and interparticle sintering occured at the center of ICP tail flame (X = 500 mm) through the results of deposited aggregates - flock, whisker and platy on MgO polycrystal plate. And the formation mechanism of $Al_2O_3$ powders In spray - ICP reactor were described from upper results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.701-704
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• 2001

The dielectric and sintering properties of LaAlO$_3$ceramics synthesised with La$_2$O$_3$-Al$_2$O$_3$(LAO) and La$_2$O$_3$-Al(OH)$_3$(LAH) were investigated. In case of LAH samples, a single phase of LaAlO$_3$powders was formed at 100$0^{\circ}C$, density of the ceramics sintered at 140$0^{\circ}C$ was 6.41g/㎤, and the dielectric constant and loss were 22.4 and 0.003, respectively. In case of LAO samples, a single phase of LaAlO$_3$powders was formed at 130$0^{\circ}C$, density of the ceramics sintered at 150$0^{\circ}C$ was 6.35g/㎤, and the dielectric constant and loss were 22.16 and 0.009, respectively.

• Journal of Korea Foundry Society
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• v.5 no.2
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• pp.118-124
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• 1985

The thickness ranges and conditions to form the supersaturated solid solution in Al-Cr alloys were investigated with various rapid solidification conditions. Al-Cr alloys, rapidly solidified by using the small droplet chill quenching method, were examined by means of micro-vickers hardness, lattice parameter, thermal analysis and microscopic observation. The results obtained were as follows; 1. With the increase of solidification rate, the solidified structures were changed to intermetallic compound + solid solution, incompletely supersaturated solid solution, completely supersaturated solid solution, in turn. 2. The minimum solidification rate required to form completely supersaturated solid solution was $2.5{\times}10^{-2}cm/sec$, $3.6{\times}10^{-2}cm/sec$ and $6.0{\times}10^{-2}cm/sec$ for Al-1.0wt%Cr, Al-1,2wt%Cr and Al-1.5wt%Cr, respectively. 3. The maximum distance from the chill surface required to form completely supersaturated solid solution was 5mm, 1.3mm and 0.3mm for Al-1.0wt%Cr, Al-1.2wt%Cr and Al-1.5wt% Cr, respectively.