• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1241-1246
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• 2010

Ternary Cu/ZnO/$Al_2O_3$ catalysts were prepared by a co-precipitation method. The precursor structures were monitored during the aging. The first precipitate structure was amorphous georgeite, which transformed into the unknown crystalline structure. The transition crystalline structure was assigned to the crystalline georgeite, which was suggested with elemental analysis, IR and XRD. The final structure of precursors was malachite. The Cu surface area of the resulting Cu/ZnO/$Al_2O_3$ was maximized to be 30.6 $m^2$/g at the aging time of 36 h. The further aging rapidly decreased Cu surface areas of Cu/ZnO/$Al_2O_3$. ZnO characteristic peaks in oxide samples almost disappeared after 24 h aging, indicating that ZnO was dispersed in around bulk CuO. TOF of the prepared catalysts of the Cu surface area ranges from 13.0 to 30.6 $m^2/g_{cat}$ was to be 2.67 ${\pm}$ 0.27 mmol/$m^2$.h in methanol synthesis at the condition of $250^{\circ}C$, 50 atm and 12,000 mL/$g_{cat}$. h irrespective of the XRD and TPR patterns of CuO and ZnO structure in CuO/ZnO/$Al_2O_3$. The pH of the precipitate solution during the aging time can be maintained at 7 by $CO_2$ bubbling into the precipitate solution. Then, the decrease of Cu surface area by a long aging time can be prevented and minimize the aging time to get the highest Cu surface area.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.9
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• pp.807-811
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• 2003

We investigated the electrical characterisitics of T $a_2$ $O_{5}$ (tantalum pentoxide) film and Ti-O/T $a_2$ $O_{5}$ film deposited on $Al_2$ $O_3$based substrate. Ta (tantalum) electrode and $Al_2$ $O_3$ substrate was used for the purpose of simplifying the manufacturing process in IPD's (integrated passive devices). Dielectric materials (T $a_2$ $O_{5}$ and Ti-O/T $a_2$ $O_{5}$ films) deposited on Ta/Ti/A $l_2$ $O_3$ were annealed at 700 $^{\circ}C$ for 60 sec. in vacuum. The XRD results showed that as-deposited T $a_2$ $O_{5}$ film possessed amorphous structure, which was transformed to crystallines by rapid thermal heat treatment. We compared the lnJ- $E^{{\frac}{1}{2}}$, C-V, C-F of both as-deposited and annealed dielectric thin films deposited on Ta bottom electrode. From this results, we concluded that the leakage current could be reduced by introducing Ti-O buffer layer and conduction mechanisms of T $a_2$ $O_{5}$ and Ti-O/T $a_2$ $O_{5}$ could be interpreted appropriately by Schottky emission effect.

• Journal of the Korean Solar Energy Society
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• v.28 no.1
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• pp.33-42
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• 2008

Zr-O ($Zr-ZrO_2$) cermets solar selective coatings with a double cermets layer film structure were prepared using a DC (direct current) magnetron sputtering method. The typical film structure from surface to bottom substrate were an $Al_2O_3$ anti-reflection layer on a double Zr-O cermets layer on an Al metal infrared reflection layer. Optical properties of optimized Zr-O cermets solar selective coating had an absorptance of ${\alpha}\;=\;0.95$ and thermal omittance of ${\epsilon}\;=\;0.10\;(100^{\circ}C)$. The absorbing layer of Zr-O cermets coatings on glass and silicon substrate was identified as being amorphous by using XRD. AFM showed that ZF-O cermets layers were very smooth and their surface roughness were approximately $0.1{\sim}0.2 nm$. The chemical analysis of the cermets coatings were determined by using XPS. Chemical shift of photoelectron binding energy was occurred due to the change of Zr-O cermets coating structure deposited with increase in oxygen flow rate. The result of thermal stability test showed that the Zr-O cermets solar selective coating was stable for use at temperature below $350^{\circ}C$.

• Journal of Conservation Science
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• v.20
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• pp.105-117
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• 2007

This study is examined the beads excavated in the Sacheon Neukdo ruins to investigate the features of archaeological chemistry and to compare those of the same type of beads excavated within the Gyeongsang-do area by means of scientific analysis. The samples have been observed the micro-structures by an optical microscope and SEM and confirmed the physical property by density measurement. Chemical property have been analyzed main components such as flux, stabilizers, and colorants by SEM-EDS. Besides, XRD was used to identified the characteristic materials of beads. The white opaque beads, which was initially estimated as sea-shell beads, confirm as amorphous silica material. The glass beads, which are blue type as a result of compositional analysis, it is revealed potash glass group and LCA(Low-CaO, $Al_2O_3$) system. gB ones are revealed only in LCA-A(LCA-CaO<$Al_2O_3$), while purple blue ones in LCA-B(LCA-CaO>$Al_2O_3$).

• Journal of the Korean Vacuum Society
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• v.9 no.4
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• pp.411-418
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• 2000

$Al_2O_3$ thin films of 300 nm thickness were deposited at room temperature using DC reactive sputtering with variation of the $O_2$ content in the sputtering gas from 30% to 70%. Regardless of the $O_2$ content in the sputtering gas, the sputtered $Al_2O_3$ films were amorphous and exhibited the refractive index of 1.58. When the $O_2$ content in the sputtering gas was higher than 50%, the $Al_2O_3$ films exhibited excellent transmittance of about 98% at 550 nm wavelength. However, the transmittance decreased to about 94% for the $Al_2O_3$ films deposited with the sputtering gas of the 30% and 40% $O_2$contents. The optimum dielectric properties (dielectric constant of 10.9 and loss tangent of 0.01) was obtained for the $Al_2O_3$ film deposited with the sputtering gas of the 50% $O_2$ content. When the $O_2$ content in the sputtering gas was within 40% to 60%, the $Al_2O_3$ films exhibited no shift of flatband voltage $V_{FB}$ in C-V curves and exhibited leakage current density lower than $10^{-5}\textrm{A/cm}^2$ at 150 kV/cm.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.95-95
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• 2011

비정질 산화물 반도체(Amorphous oxide semiconductors: AOSs)는 대면적화에도 불구하고 높은 이동도를 가지고, 상온에서도 제작할 수 있고, 투명 플렉시블 디스플레이 소자에 사용할 수 있기 때문에 최근 들어 각광받고 있는 연구 분야이다. 본 연구에서는 스퍼터링을 이용하여 활성층을 Amorphous indium gallium zinc oxide(a-IGZO)로 증착할 시에 스퍼터의 파워와 챔버내의 Ar/O2 비율을 다르게 했을 때 소자에 미치는 영향을 MIS구조를 이용하여 분석했다. 또한 같은 조건의 a-IGZO 활성층을 사용한 박막트랜지스터(TFT) 소자의 절연막의 종류를 바꿔가며 제작했을때의 소자의 특성 변화에 대해서도 분석하였다. 먼저 60 nm 두께의 a-IGZO층을 Heavily doped된 N형 실리콘 기판위에 스퍼터링 파워와 가스 분압비를 달리하여 증착하였다. 그 후 30 nm두께의 SiO2, Al2O3, SiNx 절연막을 증착하고, 마지막으로 열 증발 증착장비(Thermal Evaporator)를 이용하여 Al 전극을 150nm 증착하였다. 소자의 전기적 특성 분석은 HP4145와 Boonton 720을 사용하여 I-V와 C-V를 측정하였다. 위의 실험으로부터 스퍼터에서의 증착 rf파워가 증가할수록 a-IGZO 박막 트랜지스터에서의 캐리어 이동도가 감소하는 것을 볼 수 있었고, 챔버내의 가스분압비와 소자의 절연막의 종류가 변하면 a-IGZO 박막 트랜지스터의 전기적 특성이 변하는 것을 볼 수 있었다. 이러한 캐리어 이동도의 감소와 전기적 특성의 변화의 이유는 a-IGZO 활성층의 bulk trap과 절연막, 활성층 사이의 interface trap에 의한 것으로 보여진다.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.7 no.4
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• pp.219-227
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• 2009

The effect of organic acids on the adsorption of U(VI) onto oxide surfaces ($TiO_2)$(anatase), $SiO_2$(amorphous) and $Al_2O_3$(amorphous)) has been investigated. Two different organic acids, salicylic and picolinic acids, were used. Changes of adsorption ratio of U(VI), which depend on the existence of organic acids in a sample, were measured as a function of pH. Quantities of adsorbed organic acids, which depend on the existence of U(VI) in a sample, were also measured as a function of pH. It is confirmed that the soluble complex formation of U(VI) with organic acids can deteriorate the adsorption of U(VI) onto $TiO_2$ surface. It is noteworthy that salicylic acid does not affect the adsorption of U(VI) onto $SiO_2$ surface, however, picolinic acid enhances the adsorption of U(VI) onto $SiO_2$ surface. The latter effect can be understood by considering the formation of a ternary surface complex on $SiO_2$ surface, which was confirmed by the co-adsorption of picolinic acid with U(VI) and the change in a fluorescence spectra of U(VI) on surface, In the case of $Al_2O_3$, organic acids themselves were largely adsorbed onto a surface without deteriorating the adsorption of U(VI). This would support the possibility of a ternary surface complex formation on the $Al_2O_3$ surface, and an additional spectroscopic study is required.

• Journal of the Korean Ceramic Society
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• v.47 no.5
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• pp.401-406
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• 2010

For the lower-temperature preparation of calcium monoaluminate(CA, C:CaO, A:$Al_2O_3$) clinker which is hard to synthesize purely within its melting point, an equimolar hydrate was obtained and then used as a starting raw material of clinker burning. The hydrate was prepared from a mixture of waste oyster shell and industrial aluminium hydroxide by heating to $1200^{\circ}C$, grinding and mixing with water. The hydrate was composed of amorphous aluminium hydroxide and $C_3AH_6$(H:$H_2O$) formed by resolution-precipitation mechanism of the system C-A-H. By heating the hydrate, nearly pure and porous calcium monoaluminate clinker was formed at $1400^{\circ}C$ which is fairly lower temperature than that of its melting point. The formation of calcium monoaluminate was performed mainly by the reaction between amorphous alumina and $C_{12}A_7$ caused by the decomposition of $C_3AH_6$. The immediate and earlier formation of $C_{12}A_7$ seemed to be accelerated by not only high surface area and instability of the thermally decomposed hydrate but also the catalytic effect of water decomposed from the hydrate. The final calcium monoaluminate clinker was very porous because of the influence of highly porous shape of the thermally decomposed hydrate.

• The Korean Journal of Ceramics
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• v.3 no.4
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• pp.235-238
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• 1997

Basic properties of new cement pastes based on the system $CaO-Al_2O_3-P_O_5-H_2O$were studied Phosphoric acid solutions and calcium dialuminate clinkers synthesized by the hydration-burning method were used for liquid and powder components of the paste, respectively Variation in the compositions of the paste was achieved by changing the liquid/powder ratio and the concentration of phosphoric acid solution. The hardening rate of the paste was so largely affected by the amount of phosphoric acid that hardening was inhibited with the low-concentrated solution but was explosively accelerated with the high-concentrated solution. The phosphoric acid solutions of concentration of 45~50% and the liquid/powder ratio of 0.5~1.5 were favoured for the high early-strength cement paste with the reasonable hardening rate and high strength. The binding phase of hardened paste was the dense amorphous gel of the system $CaO-Al_2O_3-P_O_5-H_2O$. in which the unreacted calcium dialuminate grains were embeded.

• 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.