• Applied Chemistry for Engineering
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• v.31 no.4
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• pp.390-397
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• 2020

To synthesize non-corrosive metallic gold colored α-Al₂O₃ nanoplate-TiO₂ core-shell pigments with controlled roughness, we systematically checked the morphological variation of the TiO₂ shell with the mole ratio of TiCl₄ and NaOH from 1 : 1 to 1 : 1.5, 1 : 2, 1 : 2.5, 1 : 3, 1 : 3.5, and 1 : 4. The more increased mole ratio of TiCl₄ and NaOH resulted in the smoother TiO₂ shell due to the promoted formation of anatase TiO₂ than that of the rutile one. By the heat-treatment of pigments at 500 ℃, we could improve the adhesiveness between TiO₂ shell and α-Al₂O₃ nanoplates without changing their topology and roughness. In addition, the α-Al₂O₃ nanoplate with the robust TiO₂ by heat-treatment exhibited comparable photo-stability against photo-catalytic degradation by UV exposure compared with the commercially available α-Al₂O₃/TiO₂ lustering pigment.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.628-631
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• 2002

$Al_2O_3$ capping layer and MgO protective layer were deposited by electron beam evaporation method using single crystal source. Thickness of the capping layer, $Al_2O_3$, was varied from 5 nm to 10 nm. Surface morphology was observed by SEM and AFM before and after hydration. And microstructure of deposited $Al_2O_3$ layer and chemical shift of electron binding energy were also observed by high resolution TEM and XPS, respectively, after hydration. From these results, it was found that Mg atoms diffused into $Al_2O_3$ layer, reacted with moisture and formed $Mg(OH)_2$ during hydration. As thickness of $Al_2O_3$ increased, extent of hydration increased. $Al_2O_3$ capped MgO thin films and uncapped MgO thin films were deposited on AC-PDP test panel to characterize discharge properties. Although $Al_2O_3$ has poor discharge properties rather than MgO, because of many hydrated species on the surface of MgO, similar discharge properties were observed.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.6
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• pp.581-588
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• 2013

This paper presents a study of the process temperature dependence of $Al_2O_3$ film grown by thermal atomic layer deposition (ALD) as a passivation layer in the crystalline Si (c-Si) solar cells. The deposition rate of $Al_2O_3$ film maintained almost the same until $250^{\circ}C$, but decreased from $300^{\circ}C$. $Al_2O_3$ film deposited at $250^{\circ}C$ was found to have the highest negative fixed oxide charge density ($Q_f$) due to its O-rich condition and low hydroxyl group (-OH) density. After post-metallization annealing (PMA), $Al_2O_3$ film deposited at $250^{\circ}C$ had the lowest slow and fast interface trap density. Actually, $Al_2O_3$ film deposited at $250^{\circ}C$ showed the best passivation effects, that is, the highest excess carrier lifetime (${\tau}_{PCD}$) and lowest surface recombination velocity ($S_{eff}$) than other conditions. Therefore, $Al_2O_3$ film deposited at $250^{\circ}C$ exhibited excellent chemical and field-effect passivation properties for p-type c-Si solar cells.

• Journal of Powder Materials
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• v.16 no.4
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• pp.280-284
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• 2009

The pressureless sintering behavior of $Al_2O_3$/Cu powder mixtures, prepared from $Al_2O_3$/CuO and $Al_2O_3$/Cu-nitrate, has been investigated. Microstructural observation revealed that $Al_2O_3$ powders with nano-sized Cu particles could be synthesized by hydrogen reduction method. The specimens, pressureless-sintered at $1400^{\circ}C$ for 4 min using infrared heating furnace with the heating rate of $200^{\circ}C$/min, showed the relative density of above 90%. Maximum hardness of 16.1 GPa was obtained in $Al_2O_3$/MgO/Cu nanocomposites. The nanocomposites exhibited the enhanced fracture toughness of 4.3-5.7 $MPa{\cdot}m^{1/2}$, compared with monolithic $Al_2O_3$. The mechanical properties were discussed in terms of microstructural characteristics.

• Korean Chemical Engineering Research
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• v.56 no.4
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• pp.600-606
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• 2018

The influence of acidity in MTT zeolite of different Si/Al molar ratio's on the catalyst activity in methanol-to-olefin (MTO) reaction has been investigated. The Si/Al ratio was controlled with the Al content in the gel when N,N,N',N'-tetramethyl-1,3-diaminopropane was used as a structure directing agent (SDA). The gel composition was controlled to $20SiO_2$ : 30SDA : x (=0.25~1.25)$NaAlO_2$ : 2NaOH : $624H_2O$, which was subject to the hydrothermal synthesis at 433 K for 4 days. As the composition of sodium aluminate decreased, the particle size of MTT zeolite increased, and also the amount of acid sites decreased. To investigate the catalytic performance, MTO reaction was carried out at 673 K with $1.2h^{-1}$ WHSV. It was found that the H-MTT (1.00Al) catalyst with a Si/Al molar ratio of 24 maintained the methanol conversion over 90% for 900 min.

• Journal of the Korean Ceramic Society
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• v.28 no.1
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• pp.11-18
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• 1991

A precipitation method, one of the most effective liquid phase reaction methods, was adopted in order to prepare high-tech Al2O3/ZrO2 composite ceramics, and the effects of stress-induced phase transformation of ZrO2 on thermal shock behavior of Al2O3-ZrO2 ceramics were investigated. Al2(SO4)3.18H2O, ZrOCl2.8H2O and YCl3.6H2O were used as starting materials and NH4OH as a precipitation agent. Metal hydroxides were obtained by single precipitation(process A) and co-precipitation(process B) method at the condition of pH=7, and the composition of Al2O3-ZrO2 composites was fixed as Al2O3-15v/o ZrO2(+3m/o Y2O3). Critical temperature difference showing rapid strength degradation by thermal shock showed higher value in Al2O3/ZrO2 composites(process A : 20$0^{\circ}C$, process B : 215$^{\circ}C$) than in Al2O3(175$^{\circ}C$). The improvement of thermal shock property for Al2O3/ZrO2 composites was mainly due to the increase of strength at room temperature by adding ZrO2. The strength degradation was more severe for the sample with higher strength at room temperature. Crack initiation energies by thermal shock showed higher values in Al2O3/ZrO2 composites than in Al2O3 ceramics due to increase of fracture toughness by ZrO2.

• Bulletin of the Korean Chemical Society
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• v.23 no.8
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• pp.1149-1153
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• 2002

CH4/CO2 dry reforming was carried out to make syn gas on the Ni/Al2O3 catalysts calcined at different temperatures. The Ni/Al2O3 (850 $^{\circ}C)$ catalyst gave good activity and stability w hereas the Ni/Al2O3 $(450^{\circ}C)$ catalyst showed lower activity and stability. The NiO/Al2O3 catalyst calcined at $850^{\circ}C$ for 16 h (Ni/Al2O3 $(850^{\circ}C))$ formed the spinel structure of nickel aluminate, which was confirmed by TPR. The carbon formation rate on the Ni/Al2O3 $(850^{\circ}C)$ catalyst was very low till 20 h, and then steeply increased with reaction time without decreasing the activity for CH4 reforming. The Ni/Al2O3 $(450^{\circ}C)$ catalyst showed high carbon formation rate at the initial reaction time and then, the rate nearly stopped with continuous decreasing the activity for CH4 reforming. Even though the amount of carbon deposition on the Ni/Al2O3 $(850^{\circ}C)$ catalyst was higher than that on the Ni/Al2O3 $(450^{\circ}C)$ catalyst, the activity for CH4ing was also high, which could be attributed to the different type of the carbon formed on the catalyst surface.

• Journal of the Korean Ceramic Society
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• v.17 no.3
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• pp.158-162
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• 1980

The experiments of suspension hydration were performed in the mixtures of slag and water or NaOH solutions which were made up with a liquid/solid ratio of 10. The liquid phase of the suspension was chemically analysed and discussed. When slag was in contact with water, CaO component was released from slag grains into the solution. The amounts of $SiO_2$ and $Al_2O_3$ liberated in the solution were very low as compared with CaO, for the impermeable coating of $SiO_2$, $Al_2O_3$-rich gel was formed on the surface of slag grains. The hydration was considered to be inhibited by this impermeable coating. The weak hydraulic property of slag was based on slowly released CaO and dissolved Na, K components which increased pH in the solution.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.877-881
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• 2006

We obtained sputtering yields for the MgO, $MgAl_2O_4$ and $MgAl_2O_4/MgO$ films using the FIB system. $MgAl_2O_4/MgO$ protective layers have been found to have less $24^{\sim}^30%$ sputtering yield values from 0.24 atoms/ion up to 0.36 atoms/ion than MgO layers with the values from 0.36 atoms/ion up to 0.45 atoms/ion for irradiated $Ga^+$ ion beam whose energies ranged from 10 keV to 14 keV. And $MgAl_2O_4$ layers have been found to have lowest sputtering yield values from 0.88 up to 0.11. It is also found that $MgAl_2O_4/MgO$ and MgO have secondary electron emission $coefficient({\gamma})$ values from 0.09 up to 0.12 for $Ne^+$ ion whose energies ranged from 50 eV to 200 eV.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.11
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• pp.231-237
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• 2014

In this paper, we have proceeded research for failures of semiconductor device stressed by Pressure Cooker Test(PCT). After PCT stress, we found various failures such as delamination between aluminium line and device layers and chemical composition transition of aluminium. We have executed the analysis using the physical and chemical observation equipments. There were the main failures that aluminium loss of aluminium pad is occurred and $Al_xO_y$($Al_2O_3$ or $Al(OH)_3$)) layer is formed abnormally. The primary cause of the failures is reaction of supplied fluorine or chlorine gases and infiltrated moisture during etching process.