• Bulletin of the Korean Chemical Society
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• 제22권11호
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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.

• Bulletin of the Korean Chemical Society
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• 제24권1호
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• pp.86-90
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• 2003

Reverse-Water-Gas-Shift reaction (RWGSR) was carried out over the ZnO, $Al_2O_3,\;and\;ZnO/Al_2O_3$ catalysts at the temperature range from 400 to 700 ℃. The ZnO showed good specific reaction activity but this catalyst was deactivated. All the catalysts except the $ZnO/Al_2O_3$ catalyst (850 ℃) showed low stability for the RWGSR and was deactivated at the reaction temperature of 600 ℃. The $ZnO/Al_2O_3$ catalyst calcined at 850 ℃ was stable during 210 hrs under the reaction conditions of 600 ℃ and 150,000 GHSV, showing CO selectivity of 100% even at the pressure of 5 atm. The high stability of the $ZnO/Al_2O_3$ catalyst (850 ℃) was attributed to the prevention of ZnO reduction by the formation of $ZnAl_2O_4$ spinel structure. The spinel structure of $ZnAl_2O_4$ phase in the $ZnO/Al_2O_3$ catalyst calcined at 850 ℃ was confirmed by XRD and electron diffraction.

• 한국세라믹학회지
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• 제52권1호
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• pp.19-22
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• 2015

The joining behavior of YSZ ceramics to the glasses used in the $9Al_2O_3-24ZrO_2-51SiO_2-16R_2O$ and $9Al_2O_3-24ZrO_2-51SiO_2-7La_2O_3-9R_2O$ (wt%) glass systems was investigated. The glass transition and softening temperatures were determined to be $430^{\circ}C$ and $760^{\circ}C$, respectively. The behavior of the contact angle was inversely proportional to an increase in the temperature. The Zr element in YSZ acted as a nucleation agent and contributed to the bonding behavior at the interface.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.24-24
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• 2007

Aerosol deposition(AD) method is a emerging technology for the room temperature deposition of the dielectric thin films with high quality. In this study, $Al_2O_3$ thin films were deposited by aerosol deposition method directly from raw powders. To get uniform and smooth film surface, Process parameters such as gas consumption rate, nozzle-substrate distance and vibration speed were optimized. From XRD results, $Al_2O_3$ thin films have the same crystal structures with starting powders. $Al_2O_3$ thin films also showed dense microstructure. Electrical properties of the thin films were also investigated.

• 한국결정성장학회지
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• 제29권1호
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• pp.24-31
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• 2019

사파이어 단결정을 성장시키는 기존 합성방법들의 원료충진율을 높이기 위한 방법으로 스컬용융법을 사용하여 $Al_2O_3$ 파우더를 용융시켰다. 냉각도가니 크기는 내경 24 cm, 내부 높이 30 cm로서 2.75 MHz 발진주파수에서 15 kg의 $Al_2O_3$ 파우더를 1시간 내에 모두 용융시켰으며, 3시간 동안 융액상태로 유지 후 자연냉각 시켰다. 냉각된 잉곳의 부분별 면밀도 및 성분은 SEM-EDS를 통해 분석하였다. 잉곳의 면밀도 및 $Al_2O_3$ 함량은 고주파유도가열 시 냉각도가니 내부에 형성되는 온도 분포와 관련이 있으며, 온도가 높게 형성되었던 부분이 면밀도 및 순도가 높게 나타나는 경향을 보였다.

• 한국표면공학회지
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• 제33권5호
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• pp.365-372
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• 2000

Pure $Fe_3$Al alloys with three different compositions of Fe-21.8%Al, Fe-24.1%Al and Fe-27.2%Al were prepared by vacuum induction melting followed by homogenization and hot forging. The long-time oxidation behavior of the prepared alloys was studied at 1073, 1273 and 1473k in air. The oxidation resistance greatly increased with an increase in Al contents. Thin and uniform oxide scales were always formed on Fe-27.2%Al, while thick and fragile oxide scales were formed on Fe-(21.8, 24.1%)Al. Internal oxidation was observed in Fe-(21.8, 24.1%)Al, when oxidized above 1273K. The major oxidation product of all the oxidized alloys was always $\alpha$-$Al_2$$O_3$.

• 한국재료학회지
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• 제10권6호
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• pp.398-402
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• 2000

유도 용해후 열기계적 처리를 거친 3종류의 $Al_3Ti-Cr합금, 즉 Al_{67}Ti_{25}Cr_8,\;Al_{66}Ti_{24}Cr_{10}$ 및 Al_{59}Ti_{26}Cr_{15}에 대해 2.5% NaCl 용액 내에 부삭시험과 1000, 1100 및 $1200^{\circ}C$에서의 고온 산화시험을 실시하였다. 전기화학적 평가결과에서 Cr조성이 증가함에 따라 국부부식에 대한 내식성이 증가하였으며, 부동태 피막의 취성파괴를 방지하였다. XPS결과는 $Al_3Ti-Cr$합금의 부동태 피막은 주로 $Al_2O_3$로 구성되어 있으며, $TiO_2$ 및 $Cr_2O_3$도 공존하고 있음을 알 수 있었다. 고온 내산화성은 모든 시편이 전체적으로 뛰어난 내산화성을 지니고 있었는데, 구체적으로는 $Al_{59}Ti_{26}Cr_{15},\;Al_{66}Ti_{24}Cr_{10}\;및\;Al_{67}Ti_{25}Cr_8$의 순으로 증가하였다. 이는 합금내의 Al 함량이 증가할수록 $Al_2O_3$보호피막의 형성이 용이하였기 때문이었다.

• 대한기계학회논문집A
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• 제24권8호
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• pp.2032-2041
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• 2000

• 한국세라믹학회지
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• 제24권5호
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• pp.447-452
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• 1987

${\alpha}$-Al2O3 powder was produced at 1000$^{\circ}C$ by the boehmite sol-gel process with seeding 2 wt% ${\alpha}$-Al2O3. The processes and mechanisms of fornation of ${\alpha}$-Al2O3 was investigated using DTA/TG, XRD, TR spectroscopy and thermodynamic analysis. The specific surface area of the obtained ${\alpha}$-Al2O3 was 16.3㎡/g.

• 한국전기전자재료학회논문지
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• 제24권6호
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• pp.445-448
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• 2011

In this study, the etching characteristics of $Al_2O_3$ thin films were investigated using an ICP (inductively coupled plasma) of $BCl_3$/Ar gas mixture. The etch rate of $Al_2O_3$ thin films as well as the $SiO_2/Al_2O_3$ etch selectivity were measured as functions of $BCl_3$/Ar mixing ratio (0~100% Ar) at a constant gas pressure (10 mTorr), total gas flow rate (40 sccm), input power (800 W) and bias power (100 W). The behavior of the $Al_2O_3$ etch rate was shown to be quite typical for ion-assisted etch processes with a dominant chemical etch pathway. To analyze the etching mechanism using DLP (double langmuir probe), OES (optical emission spectroscopy) and surface analysis using XPS (x-ray photoelectron spectroscopy) were carried out.