• Korean Journal of Materials Research
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• v.11 no.11
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• pp.978-985
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• 2001

The amorphous alumina was obtained by flash calcination of Bayer gibbsite[$Al(OH)_3$aluminum trihydroxide]. Rehydration and pore characteristics of $r-A1_2O_3$ prepared from rehydrated amorphous alumina were investigated. Crystal phases of pseudo-boehmite and bayerite were changed when amorphous alumina was hydrated at various conditions such as time, the ratio of water/alumina and pH. Specific surface areas and pore volumes of $r- A1_{2O}_3$ were influenced by the reaction time, water/alumina and PH of rehydration. The total pore volume of $r-A1_{2O}_3$increases with increasing the reaction time and ratio of water/alumina. Especially, the pure pseudo-boehmite of single phase could be prepared, when amorphous alumina was hydrated in the range of pH 6.5-8.0 in water/alumina= 10 at $90^{\circ}C$ for 7hr. The $r-Al_{2O}_3$, obtained by calcination of the prepared pseudo-boehmite at $500^{\circ}C$ for 2hrs, is characterized by the specific surface area of $265m^2$/g, total pore volume of $0.75cm^3$/g.

• Advances in environmental research
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• v.8 no.1
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• pp.55-69
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• 2019

The generation of ferrous slag, an industrial by-product from the iron ore industry, results in serious environmental problems. The chemical compositions indicate 30-34% SiO₂, 30-34% CaO, 18-22% Al₂O₃ and 0.5-0.6% Fe₂O₃. The specific gravity, moisture content and pH are in the range of 1.3-1.65, 9.1-10% and 8.5-9.0 respectively. The major part of the slag is composed of sand-size particles. The problems of disposal of slag could be minimized by considering its use in various environmental engineering applications providing additional value to the by-product. This paper mainly focuses on the potential utilization and valorisation of ferrous slag in both water and wastewater treatments. It is effective for the treatment of water and wastewater containing nutrients, heavy metals and polluted river/stormwater.

• Journal of the Korean institute of surface engineering
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• v.54 no.1
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• pp.25-29
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• 2021

The fabrication of nanopore membrane by deposition of Al2O3 film using electron-beam evaporation, which is fast, cost-effective, and negligible dependency on substance material, is investigated for potential applications in water purification and sensors. The decreased nanopore diameter owing to increased wall thickness is observed when Al2O3 film is deposited on anodic aluminum oxide membrane at higher deposition rate, although the evaporation process is generally known to induce a directional film deposition leading to the negligible change of pore diameter and wall thickness. This behavior can be attributed to the collision of evaporated Al2O3 particles by the decreased mean free path at higher deposition rate condition, resulting in the accumulation of Al2O3 materials on both the surface and the edge of the wall. The reduction of nanopore diameter by Al2O3 film deposition can be applied to the nanopore membrane fabrication with sub-100 nm pore diameter.

• Bulletin of the Korean Chemical Society
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• v.29 no.5
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• pp.1048-1050
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• 2008

Electric current flow was observed through imogolite film when imogolite ($(HO)_3Al_2O_3SiOH$) was exposed to water molecules and connected to external electrodes. Current flow was due to the bound water on the surface of imogolite. Current flow increased as the pH of the water decreased. The current-voltage (I-V) measurements from a field effective transistor (FET) using $H_2O$/imogolite film revealed that the current carrier in $H_2O$/ imogolite had p-type characteristics, i.e. the carrier was probably $H^+$. The possible mechanism for current transportation in imogolite/water was also suggested in this paper.

• Journal of the Korean Ceramic Society
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• v.34 no.4
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• pp.380-386
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• 1997

The tribological properties of ceramics are very important in the application to engineering ceramic parts such as seal rings, pump parts, thread guides, and so on. In this study, the effects of graphite addition on the mechanical and tribological properties of alumina/graphite composites were investigated. The composites were prepared by the adding of graphite powder to the mixture of Al2O3, talc and calcium carbonate. Bending strength, water absorption, friction coefficient, the amount of worn out material at a certain time, and maximum surface roughness(Rmax) of the prepared composites were measured. Crystalline phases and microstructure were examined with XRD and SEM. The melt of Al2O3-CaO-MgO-SiO2 system was shown over 10 vol% graphite composition. As the amount of the graphite is increased, needle like crystals of mullite were formed and grown. We obtained the good properties of friction coefficients and wear resistance at the powder composition containing 15 vol% of graphite.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.5
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• pp.477-483
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• 2015

LFG (Land-Fill Gas) includes components of $CH_4$, $CO_2$, $O_2$, $N_2$, and water. The preparation of synthesis gas from LFG as a DME (Dimethyl Ether) feedstock was studied by methane reforming of $CO_2$, $O_2$ and steam over $NiO-MgO-CeO_2/Al_2O_3$ catalyst. Our experiments were performed to investigate the effects of methane conversion and syngas yield on the amount of LFG components over $NiO-MgO-CeO_2/Al_2O_3$ catalyst. Results were obtained through the methan reforming experiments at the temperature of $900^{\circ}C$ and GHSV of 8,800. The results were as following; it has generally shown that syngas yield increase with the increase of oxygen and steam amounts and then decrease. Highly methane conversion of above 98% and syngas yield of approximately 60% were obtained in the feed of gas composition flow-rate of 243ml/min of $CH_4$, 241ml/min of $CO_2$, 195ml/min of $O_2$, 48ml/min of $N_2$, and 450ml/min of steam, respectively, under reactor pressure of 1 bar for 200 hrs of reaction time. Also, it was shown that catalyst deactivation by coke formation was reduced by excessively adding oxygen and steam as an oxidizer of the methane reforming.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.432.1-432.1
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• 2016

We demonstrated that the power conversion efficiency (PCE) of bilayer solar cell was significantly enhanced by inserting interfacial layer between the organic bilayer film and the Al electrode. Moreover, the water contact angle shows that the bilayer solar cells suffer from the undesirable surface component which limits the charge transport to the Al electrode. The AFM measurement has revealed that the pre- and post-thermal annealing treatments results in different morphologies of the interfacial layer which is critical for the higher PCE of the bilayer solar cells. Furthermore we have investigated the electrical properties of the bilayer solar cells and obtained insights into the detailed device mechanisms. The transient photovoltage measurements suggests that the significantly enhanced Voc is caused by reducing the recombination at the interface between the organic films and the Al electrode. By inserting the TiO2 layer between the bilayer film and Al electrode, the open circuit voltage (Voc) was increased from 0.37 to 0.66V. Consequently, the power conversion efficiency (PCE) of bilayer solar cells was significantly enhanced from 1.23% to 3.71%. As the results, the TiO2 interfacial layer can be used to form an ohmic contact layer, serveing as a blocking layer to prevent the penetration of the Al, and to reduce the recombination at the interface.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.1
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• pp.149-157
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• 2012

Experiments for As(V) removal using synthesized $Ca{\cdot}Al$-monosulfate was performed from the water contaminated with arsenate. Monosulfate is known as LDHs (Layered Double Hydroxides) which is one of the anionic clay minerals. Monosulfate was synthesized mixing $C_3A$ (tricalcium aluminate), gypsum (calcium sulfate), and water with an intercalation method. The product form the synthesis was characterized by FE-SEM, WDXRF, PXRD, and FT-IR. Experiments with different doses of monosulfate were carried out for kinetic. As a result of experiment, the concentration of As(V) was reduced from 0.67 mM to 0.19 mM (0.67mM of monosulfate) and 0.178 mM (1.34 mM of monosulfate). The concentration of sulfate was increased with As(V) decrease. The result of PXRD showed that the d-spacing of inter layer ($d_{003}$ peak) was shifted from 8.927 ${\AA}$ to 8.095 ${\AA}$ because the sulfate in the inter layer of monosulfate was exchanged arsenate with water molecules bonded. From the FT-IR results, a new single band (800 cm-1) was observed after the reaction of monosulfate and As(V). The arsenic removal can be regarded as anion exchange mechanism that is one of the characteristics of LDHs from the results of PXRD and FT-IR analysis.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.321-322
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• 2001

대기중 과산화수소($H_2O$$_2$)는 기상과 액상에서 peroxy radicals 간의 결합 (HO$_2$ㆍ+ HO$_2$ㆍ $\longrightarrow$$H_2O$$_2$+O$_2$)에 의해 생성된다. 만약 수소 원자 하나가 organic group으로 치환되면 organic peroxides가 생성된다(Calvert et al., 1985). 이러한 과산화수소($H_2O$$_2$)와 methylhydroperoxide(MHP, $CH_3$COOH), hydroxymethylhydroperocide(HMHP, HOC$H_2O$OH)등의 organic peroxides는 대기 중에서 주요 산화제로 작용한다. 이들 peroxide 물질들은 pH 5 이하의 aqueous phase (cloud, fog and rain water)에서 sulphuric acid (HSO$_4$$^{2-}$ ) 형성에 중요한 역할을 한다(Calvert et al., 1985). (중략)

• Journal of the Mineralogical Society of Korea
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• v.16 no.3
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• pp.245-254
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• 2003

Stishovite was synthesized from hydrous basaltic starting materials at 10∼15 ㎬ and $1000∼1400^{\circ}C$. Water content of synthetic stishovite has been determined, and solid solution mechanism of $H_2$ and Al in stishovite was investigated. The maximum water content obtained from stishovite single crystal was up to $844\pm$44 ppm $H_2$O. The concentration of hydrogen increased with increasing substitution of trivalent cation, mainly Al. The temperature effect on the hydrogen content in stishovite is more sensitive than that on any other impurities. Among the nominally anhydrous mantle-minerals, stishovite could be an important water-containing phase and contribute to the transportation of $H_2$O to lower mantle.