• Journal of the Korean Ceramic Society
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• 제31권11호
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• pp.1362-1368
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• 1994

The hydrolysis of aluminum nitride was increased gradually with increasing reaction time from 1 hrs to 24 hrs and/or with decreasing the addition of the reaction water from 100 mι 100mι. Amorphous aluminum hydrate, formed in the beginning of the reaction, was transformed to bayerite and to pseudoboehmite at below and above 8$0^{\circ}C$, respectively. Aluminum oxynitride was synthesized by heating the partially hydrolyzed aluminum nitride at 1$700^{\circ}C$ for 4 hrs or at 175$0^{\circ}C$ for 30 min. AlON specimen with 1 wt% of Y2O3 that was molded and then sintered pressurelessly at 190$0^{\circ}C$, exhibits 98% of the theoretical density and a translucency of 68% in the visible ray zone.

• Journal of Korea Foundry Society
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• 제41권1호
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• pp.3-10
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• 2021

In the compound casting between the aluminum alloy and the cast iron, the iron component may be dissolved from the cast iron during the process and mixed into the aluminum melt, thereby forming various iron-containing intermetallic compounds and significantly deteriorating the tensile properties of the aluminum alloy. On the other hand, unlike Fe, which is added as an impurity, Cu is added to improve the mechanical properties of the aluminum alloy. In this study, the change in microstructure and tensile properties of aluminum alloys due to the addition of Fe and Cu was investigated. A large amount of iron-containing compounds such as coarse Al₅FeSi phases were formed when the iron content was 1% or more, and the tensile properties were significantly reduced. In the case of the aluminum alloy to which Cu was added, an Al₂Cu phase was additionally formed and the tensile strength was clearly improved.

• Journal of the Korean Ceramic Society
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• 제41권8호
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• pp.610-617
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• 2004

For preparation $\alpha$-Al$_2$O$_3$ platelets having 20 $\mu$m in average diameter and 0.2∼0.3 $\mu$m in thickness, we have prepared aluminum hydroxides gel by using aluminum sulfate and sodium sulfate as starting materials. In this study, we investigated the effect of the amount of sodium phosphate on particle size, morphology and thickness of $\alpha$-Al$_2$O$_3$ platelets. When sodium phosphate was not added to aluminum hydroxides gel, most of $\alpha$-Al$_2$O$_3$ platelets had hexagonal shape but the thickness was over 1.0 $\mu$m, and this sample was not adequate for pearlescent pigment. On the other hand, introduction of sodium phosphate caused an increase of aspect ratio (particle diameter/thickness) with a decrease in $\alpha$-Al$_2$O$_3$ platelet thickness.

• Journal of the Korean Ceramic Society
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• 제40권9호
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• pp.909-915
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• 2003

Anodic oxide films on aluminum play an important role as a dielectrics in aluminum electrolytic capacitor. In order to obtain the high capacitance, ZrO$_2$ films were coated on aluminum foils by sol-gel method and then, the properties of anodized films were studied. The coating and drying of the films were repeated 4-10 times and annealed at 300～$600^{\circ}C$ and the triple layer of ZrO$_2$/Al-ZrO$_{x}$ /Al$_2$O$_3$ was formed onto aluminum substrates after anodizing of ZrO$_2$/Al film. The thickness of $Al_2$O$_3$ layer was decreased with increasing the annealing temperature due to the densification of ZrO$_2$ film. The ZrO$_2$ films were crystallized even at 30$0^{\circ}C$ and showed nanocrystalline structure. The. capacitance of aluminum foil annealed at low temperature was higher than that at high temperature. The increase of capacitance was due to the high capacitance of ZrO$_2$ film annealed at low temperature. The capacitance of ZrO$_2$ coated aluminum increased about 3 times compared to that without a ZrO$_2$ layer after anodizing to 400 V. From these results, the aluminum foils with composite oxide layers are found to be applicable to the aluminum electrolytic capacitor.

• Bulletin of the Korean Chemical Society
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• 제33권10호
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• pp.3258-3264
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• 2012

Aluminum oxide ($Al_2O_3$) nanofibers were treated thermally under an ammonia ($NH_3$) gas stream balanced by nitrogen to form a thin aluminum nitride (AlN) layer on the nanofibers, resulting in the enhancement of thermal conductivity of $Al_2O_3$/epoxy nanocomposites. The micro-structural and morphological properties of the $NH_3$-assisted thermally-treated $Al_2O_3$ nanofibers were characterized by X-ray diffraction (XRD) and atomic force microscopy (AEM), respectively. The surface characteristics and pore structures were observed by X-ray photoelectron spectroscopy (XPS), Zeta-potential and $N_2$/77 K isothermal adsorptions. From the results, the formation of AlN on $Al_2O_3$ nanofibers was confirmed by XRD and XPS. The thermal conductivity (TC) of the modified $Al_2O_3$ nanofibers/epoxy composites increased with increasing treated temperatures. On the other hand, the severely treated $Al_2O_3$/epoxy composites showed a decrease in TC, resulting from a decrease in the probability of heat-transfer networks between the filler and matrix in this system due to the aggregation of nanofiber fillers.

• Journal of the Korean Society of Food Science and Nutrition
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• 제25권1호
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• pp.39-45
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• 1996

The study was performed to investigate the effects of administration of aluminum compound in Kidney metabolism and plasma hormone of rats. Seventy frve male Sprague-Dawley strains rats were divided into five groups consisting of the control, 250ppm AlCl$_3$group, 500ppm AlCl$_3$ group, 250ppm $Al_2$(SO$_4$)$_3$group, 500ppm $Al_2$(SO$_4$)$_3$group and kept on the diet for 2 weeks. The body weight gain was increased by the administration of AlCl$_3$ but decreased by the administration of $Al_2$(SO$_4$)$_3$as compared to the control. The urinary excretion of sodium and creatinine were increased and free water clearance and urine volume were decreased significantly after AlCl$_3$adminstration group as compared to the control. The water balance, free water clearance, excretion of sodium and creatinine were increased and the excretion of chlorine was decreased after $Al_2$(SO$_4$)$_3$ administration as compared to the control. Plasma renin activity was increased and plasma aldosterone content was compared to the control. Plasma renin activity was increased and plasma aldosterone content was significantly decreased after adminstration of aluminum compounds as compared to the control.

• Archives of Metallurgy and Materials
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• 제65권3호
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• pp.1019-1022
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• 2020

In the past few years, overhead copper transmission lines have been replaced by lightweight aluminum transmission lines to minimize the cost and prevent the sagging of heavier copper transmission lines. High strength aluminum alloys are used as the core of the overhead transmission lines because of the low strength of the conductor line. However, alloying copper with aluminum causes a reduction in electrical conductivity due to the solid solution of each component. Therefore, in this study, the authors attempt to study the effect of various Al/Cu ratios (9:1, 7:3, 5:5) to obtain a high strength Al-Cu alloy without a significant loss in its conductivity through powder metallurgy. Low-temperature extrusion of Al/Cu powder was done at 350℃ to minimize the alloying reactions. The as-extruded microstructure was analyzed and various phases (Cu9Al₄, CuAl₂) were determined. The tensile strength and electrical conductivity of different mixing ratios of Al and Cu powders were studied. The results suggest that the tensile strength of samples is improved considerably while the conductivity falls slightly but lies within the limits of applications.

• Bulletin of the Korean Chemical Society
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• 제20권10호
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• pp.1205-1208
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• 1999

27Al NMR chemical shielding, quadrupolar coupling, and dipolar coupling interactions for corundum (α-Al2O3) are determined from the single-crystal 27 Al NMR spectra according to the rotation about three orthogonal axis. 27 Al NMR parameters obtained in this work with high accuracy are as follows: δiso = 7.4(4) ppm, QCC = 2.30(4) MHz, h = 0.08(3), and R = 2.0(3) kHz. This work appears to be the first NMR measurement of an aluminum-aluminum dipolar coupling interaction in α-Al2O3 crystals.

• YAKHAK HOEJI
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• 제27권2호
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• pp.139-148
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• 1983

The neutralizing capacities of the antacids, which are frequently used in Korean market, were evaluated in vitro by the methods of Resset and Rice, Fordtran and Collyns, and modified Beekman, respectively. The antacids used in the study are two kinds, the one is preparations from Seoul National University Hospital and the other is products from pharmaceutical companies, and their components are aluminum phosphate, aluminum hydroxide, magnesium aluminum hydroxide, magnesium hydroxide, basic aluminum sucrose sulfate and $2MgO{\times}Al_{2}O_{3}{\times}SiO_{3}$, etc. The hospital preparations, DMC and MAC powders, showed most powerful and sustained neutralizing capacities, i.e. they maintained the pH range from 5 to 8 for 60min, Whereas pharmaceutical products, aluminum hydroxide gel containing magnesium hydroxide and magnesium aluminum hydroxide gel exhibited a moderate capacities, i.e pH ranged from 3 to 6, and aluminum phosphate, $2MgO{\times}Al_{2}O_{3}{\times}SiO_{2}$ and basic aluminum sucrose sulfate displayed a weak activity, pH ranged from 2 to 3. When the therapeutic doses of aluminum hydroxide gel containing magnesium hydroxide and magnesium aluminum hydroxide gel were divided into 2 doses and each dose was used at the interval of 30min., the divided doses kept more prolonged higher pH than the single therapeutic dose. Milliequivalents of neutralizing capacities of each antacid were measured by the method of Fordtran and Collyns. The milliequivalents per 1ml of aluminum hydroxide gel, aluminum hydroxide gel containing magnesium hydroxide, magnesium aluminum hydroxide gel and aluminum phosphate were 2.87, 2.86, 2.57, and 0.67, respectively. The milliequivalents per 100mg of preparations, i.e. MAC powder, dried aluminum hydroxidgel, DMC powder, 2MgO, $Al_{2}O_{3}$. $SiO_{2}$, magnesium aluminum hydroxide and basic aluminum sucrose sulfate were 1.91, 1.68 1.63, 1.45, 1.44, and 0.44, respectively.

• Journal of Powder Materials
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• 제11권4호
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• pp.308-313
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• 2004

An experimental study on the combustion of superfine aluminum powders (average particle diameter, a$_{s}$: ∼0.1 ${\mu}{\textrm}{m}$) in air is reported. The formation of aluminum nitride during the combustion of aluminum in air and the influence of the combustion scenario on the structures and compositions of the final products are in the focus of this study. The experiments were conducted in an air (pressure: 1 atm). Superfine aluminum powders were produced by the wire electrical explosion method. Such superfine aluminum powder is stable in air but once ignited it can burn in a self-sustaining way due to its low bulk: density (∼0.1 g/㎤) and a low thermal conductivity. During combustion, the temperature and radiation were measured and the actual burning process was recorded by a video camera. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and chemical analysis were performed on the both initial powders and final products. It was found that the powders, ignited by local heating, burned in a two-stage self-propagating regime. The products of the first stage consisted of unreacted aluminum (-70 mass %) and amorphous oxides with traces of AlN. After the second stage the AlN content exceeded 50 mass % and the residual Al content decreased to ∼10 mass %. A qualitative discussion is given on the kinetic limitation for AlN oxidation due to rapid condensation and encapsulation of gaseous AlN.N.