• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.4
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• pp.172-179
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• 2006

When $Al_2O_3-MoO_3$ mixture is reduced, $MoO_3$ is only reduced to Mo at $900^{\circ}C$. But a compound between $Al_2O_3$ and Mo is not formed up to $1300^{\circ}C$. In the case of $Al_2O_3-MoO_3-MnO_2$ mixture, an intermediate compound $Mn_2Mo_3O_8$ is firstly formed at $900^{\circ}C$ and changes to $MnAl_2O_4$ at $1100^{\circ}C{\sim}1300^{\circ}C$. $Al_2O_3/Mo/MnO_2$ composite are manufactured by a selective reduction process in which Mo is only reduced in the powder mixture of $Al_2O_3,\;MoO_3\;and\;MnO_2$ oxide. For $Al_2O_3/Mo$ composite, the average grain size was not changed with increasing Mo content because of inhibition of grain growth of $Al_2O_3$ matrix in the presence of Mo particles. Fracture strength increased with increasing Mo content due to phenomenon of grain growth inhibition of $Al_2O_3$ matrix. Hardness decreased because of a lower hardness value of Mo, whereas fracture toughness increased. For $Al_2O_3,\;Mo\;and\;MnO_2$ composite, grain growth was facilitated by MnOB and it showed a lower fracture strength because of grain growth effect with increasing Mo and $MnO_2$ content. Hardness decreased because of the grain growth of matrix and coalesced Mo particles to be located in grain boundary, whereas fracture toughness increased.

• Korean Chemical Engineering Research
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• v.60 no.1
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• pp.159-168
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• 2022

Catalytic activity in ammonia decomposition reaction was studied on Mo-Al nitride obtained through temperature programmed nitridation of calcined Mo-Al mixed oxide prepared by varying the MoO₃ quantity in the range of 10-50 wt%. N₂ sorption analysis, X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS) and H₂-temperature programmed reduction (H₂-TPR), and transmission electron microscopy (TEM) to investigate the physicochemical properties of the prepared catalyst were performed. After calcination at 600 ℃, the XRD of Mo-Al oxide showed γ-Al₂O₃ and Al₂(MoO₄)₃ phases, and the nitride after nitridation showed an amorphous form. The specific surface area after nitridation by topotactic transformation of MoO₃ to nitride was increased due to the formation of Mo nitride, and the Mo nitride was observed to be supported on γ-Al₂O₃. As for the catalytic activity in the ammonia decomposition reaction, 40 wt% MoO₃ showed the best activity, and as the nitridation time increases, the activity increased, and thus the activation energy decreased.

• Journal of Electrochemical Science and Technology
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• v.10 no.4
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• pp.424-432
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• 2019

Planar BiVO₄ and 3 wt% Mo-doped BiVO₄ (abbreviated as Mo:BiVO₄) film were prepared by the facile spin-coating method on fluorine doped SnO₂(FTO) substrate in the same precursor solution including the Mo precursor in Mo:BiVO₄ film. After annealing at a high temperature of 450℃ for 30 min to improve crystallinity, the films exhibited the monoclinic crystalline phase and nanoporous architecture. Both films showed no remarkably discrepancy in crystalline or morphological properties. To investigate the effect of surface passivation exploring the Al₂O₃ layer, the ultra-thin Al₂O₃ layer with a thickness of approximately 2 nm was deposited on BiVO₄ film using the atomic layer deposition (ALD) method. No distinct morphological modification was observed for all prepared BiVO₄ and Mo:BiVO₄ films. Only slightly reduced nanopores were observed. Although both samples showed some reduction of light absorption in the visible wavelength after coating of Al₂O₃ layer, the Al₂O₃ coated BiVO₄ (Al₂O₃/BiVO₄) film exhibited enhanced photoelectrochemical performance in 0.5 M Na₂SO₄ solution (pH 6.5), having higher photocurrent density (0.91 mA/㎠ at 1.23 V vs. reversible hydrogen electrode (RHE), briefly abbreviated as V_RHE) than BiVO₄ film (0.12 mA/㎠ at 1.23 V_RHE). Moreover, Al₂O₃ coating on the Mo:BiVO₄ film exhibited more enhanced photocurrent density (1.5 mA/㎠ at 1.23 V_RHE) than the Mo:BiVO₄ film (0.86 mA/㎠ at 1.23 V_RHE). To examine the reasons, capacitance measurement and Mott-Schottky analysis were conducted, revealing that the significant degradation of capacitance value was observed in both BiVO₄ film and Al₂O₃/Mo:BiVO₄ film, probably due to degraded capacitance by surface passivation. Furthermore, the flat-band potential (V_FB) was negatively shifted to about 200 mV while the electronic conductivities were enhanced by Al₂O₃ coating in both samples, contributing to the advancement of PEC performance by ultra-thin Al₂O₃ layer.

• Korean Journal of Materials Research
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• v.12 no.3
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• pp.220-224
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• 2002

The oxide scales formed on $Ni_3Al$-7.8%Cr-1.3%Zr-0.8%Mo-0.025%B after oxidation at 900, 1000 and 110$0^{\circ}C$ in air were studied using XRD, SEM, EPMA and TEM. The oxide scales consisted primarily of $NiO,\; NiAl_2O_4,\;{\alpha}-Al_2O_3,\; monoclinic-ZrO_2,\; and \;tetragonal-ZrO_2$. The outer layer of the oxide scale was rich in Ni-oxides, whereas the internal oxide stringers were rich in Al-oxides and $ZrO_2$. Within the above oxide scales, Cr and Mo tended to exist as dissolved ions.

• Bulletin of the Korean Chemical Society
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• v.22 no.11
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• pp.1224-1230
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• 2001

Single crystals of nanocomposite [GaO4Al12(OH)24(H2O)12][Al(OH)6Mo6O18]2(OH)${\cdot}$30H2O, 2, were obtained by the reaction between [GaO4Al12(OH)24(H2O)12]7+ and [Mo7O24]6- clusters in an aqueous solution, analogously to the [AlO4Al12(OH)24(H2O)12][Al(OH)6Mo6O18]2(OH)${\cdot}$29.5H2O nanocomposite, 1. The crystal structure of 2 was determined by single crystal x-ray diffraction; space group $C2}c$ (No. 15), a = 27.418(2) $\AA$, b = 15.647(2) $\AA$, c = 23.960(4) $\AA$, $\beta$ = $102.850(9)^{\circ}$, V = 10,021.5(20) $\AA3$ , Z = 4. Detailed analysis of the structural data show that the clusters are held by intimate hydrogen bondings of the surface O2- and OH- groups of the clusters as well as the ionic interactions between the oppositely charged cluster ions.

• Korean Journal of Materials Research
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• v.12 no.11
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• pp.845-849
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• 2002

Alloys of $Fe_3$Al, $Fe_3$Al-6Cr, $Fe_3$Al-4Cr-1Mo, $Ni_3$Al, and $Ni_3$Al-2.8Cr were oxidized at $1000^{\circ}C$ in air, and the oxide scales formed were studied using XRD. SEM, EPMA, and TEM. The oxide scales that formed on $Fe_3$Al-based alloys consisted primarily of $\alpha$-$Al_2$$O_3$ containing a small amount of dissolved Fe and Cr ions, whereas those that formed on $Ni_3$Al-based alloys consisted primarily of $\alpha$-$Al_2$$O_3$, together with a small amount of $NiAl_2$$O_4$, NiO and dissolved Cr ions. For the entire alloys tested, nonadherent oxide scales formed, and voids were inevitably existed at the scale-matrix interface.

• Bulletin of the Korean Chemical Society
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• v.21 no.12
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• pp.1239-1244
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• 2000

A study of K addition to the catalyst of CoMo/ ${\gamma}-Al_2O_3$ was studied. The catalyst with 10 at% of K to Mo atoms in 3C10M, the catalyst added 3 wt% CoO to 10 wt% $MoO_3/{\gamma}-Al_2O_3$, showed the highest activity for water gas shift reaction. The addition of K retarded the reducibility of cobalt-molybdenum catalysts. It gave, however, good dispersion and large BET surface area to the catalysts which were attributed to the disappearance of polymolybdate clustyer such as $Mo_7O_{24}^{6-}$ and the formation of small Mo$O_4^{2-}$ cluster. It was confirmed by the analyses of pore size distribution, activation energy, Raman spectroscopy, and electron diffraction. The activation energies and the frequency factors of the catalysts 3C10M and 5KC10M (the catalyst added 5 at% K for Mo to the catalyst 3C10M) were 43.1 and 47.8 kJ/mole, and 4,297 and 13,505 $sec^{-1}$, respectively. These values were also well correlated with our suggestion. These phenomena were attributed to the direct interaction between K and CoMo oxides irrelevant to the support.

• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.936-941
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• 2001

The influence of the ${Al_2}{O_3}$ particle size on flaw tolerance of the $ZrO_2/{Al_2}{O_3}$ composites prepared by mixing 5.31 mol% ${Y_2}{O_3}$-4.45 mol% ${Nb_2}{O_5}$-90.31 mol% $ZrO_2$ and ${Al_2}{O_3}$ was investigated. The composites exhibited rising R-curve behavior and plateau fracture toughness of 7.9 and $8.8MPam^{1/2}$ for the additions of 20 vol% of 0.2 and $2.8{\mu}m$ ${Al_2}{O_3}$ particles, respectively. The difference in the fracture toughness resistance was attributed mainly to the grain size of tetragonal $ZrO_2$ phase in the composites, which scaled with the ${Al_2}{O_3}$ particle size.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.650-653
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• 2004

We have synthesized some phosphors in the system MO-$Al_2O_3-SiO_2$(M=Sr, Ba) by combinatorial polymerized-complex method. Composition and synthetic temperature of phosphors in the liblary was screened from the emission intensities of individual samples under 365nm excitation. As we were screened the higher luminescent candidate composition (or candidate host lattice) at 365nm excitation, investigated whether good radiation was possible at the 405 or 465nm excitation by give the host lattice to be discovered more various change. From libraries about 2 systems, the compound to be expected in long wavelength among the compound to be screened are $Sr_4Al_{14}O_{25}$, $Sr_3Al_2O_6$, $SrAl_2Si_2O_8$, and $BaAl_2Si_2O_8$.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.560-567
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• 2016

In this study, we characterized steam reforming reactions and surface of $Ni/Al_2O_3$ catalysts. Ni-Mo based catalysts were prepared by loading Mo as the co-catalyst and reaction activities of the Ni-Mo based catalysts were compared with those of Ni-based catalysts. Through the $H_2$-TPR and XPS analysis it was confirmed that this characteristic efficiency. $O_2$-TPO analysis was performed to examine the deposition characteristics, bonding structures and evaporation characteristics of carbon deposited on the surface of catalysts after long run experiments were performed for steam reforming reactions. As the results, it was found that durability was improved in Ni-Mo based catalysts inhibiting formation of graphitic carbon species which reduced reaction activities of the catalysts by strongly interacting with Ni in the steam reforming reaction.