• YAKHAK HOEJI
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• v.21 no.2
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• pp.101-109
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• 1977

The effect of humidity on the aging process of hydrous aluminum oxide prepared by the reaction of aluminum chloride and sodium bicarbonate solution at pH 7.8, which was then kept in various atmosphere under relative humidity at 37.deg. was observed by the measurements of acid consuming capacity, X-ray diffraction and IR absorption. The humidity was one of the important factors influencing the aging process of hydrous aluminum oxide during storage. The higer the humidity, the more was accelerated age, crystalize and loss in acid reactivity. Depending on the humidity, the aging product was different, especially, in the case of up to the relative humidity of 72%, it forming bayerite. On the other hand, the hydrous aluminum oxide aged below the relative humidity of 50% was still amorphous even after 120 days storage. When hydrous aluminum oxide was aged under higher humidity, definite IR absorption bands develop as the hydroxys become part of an ordered structure, and it showed their characteristic absorption band around 1630 and 1060 cm$^{-1}$.

• Korean Journal of Computational Design and Engineering
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• v.14 no.4
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• pp.234-241
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• 2009

The use of aluminum parts in automobile structuraI applications has increased in an effort to reduce the weight of cars and hence improve fuel economy. But Aluminum bar, I-beam and channels need other processes to vary the cross section in the axial direction. Thus, applications of these parts are limited by high cost. If the cross section of the part is variable by using only extrusion, application of extruded bar, I-beam and channels will increase in the Aluminum industries. In this paper, we propose the variable-shape extrusion process which can control the thickness of Aluminum bar. And we can calculate the speed of center ram by varying the cross section in the extrusion to control the thickness of Aluminum bar.

• Journal of the Korean Ceramic Society
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• v.27 no.6
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• pp.747-754
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• 1990

Aluminum hydrate gels were prepared from the mixtures of bauxite and ammonium sulfate by wet acid process. Optimum conditions for obtaining the maximum yield( 99%) of aluminum hydrates from the same amount of bauxite were confirmed as follows ; 1. Mixing ratio ; addition of 25mole% of ammonium sulfate to 1mole of bauxite. 2. Calcination ; heated at 350℃ for 1hr. 3. Extraction ; leached at 95℃ in 1% H2SO4 for 90min. 4. pH of precipitating solution; slight below 7.0. Amorphous aluminum hydrates were precipitated at the pH lower than 8.5, but the precipitates crystallized to bayerite at the pH was 10. Mean diameter of α-Al2O3 powders which were obtained by calcining the aluminum hydrates was below 0.2㎛, and EDS analysis revealed than SiO2 was it's primary impurity.

• Journal of the Korean Society of Combustion
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• v.19 no.1
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• pp.1-10
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• 2014

An analytical study on performance evaluation of superdetonative mode ram accelerator was conducted for understanding the experimental result. The quasi-one dimensional continuum, momentum, energy equations were solved under the assumption of inviscid flow. It would be noticeable that experimental result could be analytically simulated with the assumptions of inlet shockwave, temperature dependent specific heat, and additional aluminum combustion due to ablation of aluminum projectile in superdetonative operation mode. The acceleration of ram accelerator was comparable to experimental result with the consideration of the additional aluminum combustion energy by ablation of projectile. As result, the experimental result with the aluminum projectile could be affected by heat of aluminum.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.217-218
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• 2007

Aluminum 분말과 고분자를 혼합하여 고분자-금속 복합재료(polymer-metal composite)를 만들어 copper foil과 기판의 접착력을 평가하였다. Tape casting 방법을 이용하여 sheet 만들고 vacuum lamination으로 PCB(Printed Circuit Board)기판을 제조한 후 포토공정으로 peel strength pattern을 형성하였으며, 본 연구에서는 최적의 aluminum 조건을 찾기 위하여 압력, 온도, copper foil의 표면 상태와 silane 표면 코팅에 따른 aluminum-polymer복합재료의 peel strength의 변화를 확인하였다. 최적의 조건은 silane 표면 코팅 처리를 한 aluminum 분말로 $210^{\circ}C$에서 $9.7kg/cm^2$ 압력으로 matte면의 돌기 크기가 크며, 응집이 잘 되어있는 copper foil을 사용하여 13.89N의 우수한 peel strength를 구현 할 수 있었다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.188-191
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• 2005

Lower arm for automobile has been made in steel traditionally. Nowadays steel is being substituted fur aluminum to reduce weight of automobile. Widely applied production method of aluminum component has been casting processes or cast/forging processes. But casting or cast/forging processes have limits of application to parts which is required high strength durability like automotive component. In this research, hot forging process has been adopted to produce aluminum lower arm to ensure required mechanical properties. To reduce production cost, 2 pieces with 1 blow process was developed. Optimization and verification of hot forging process for aluminum lower arm was performed by computer aided engineering using finite volume methods.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.78-81
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• 2005

The aluminum Subframe for automobile was developed using hybrid process, i.e. extruforming and press forming. To achieve a $30\%$ weight reduction compared with convensional steel subframe keeping satisfactory performance, the design of cross-section of extrusion part was initiated, then forming simulation was performed and the final design was determined. In addition, we tried to estibilish proper aluminum welding conditions for good penetration depth and few pore defact, finally the prototype of aluminum subframe was assembled using MIG welding method.

• Journal of the Korean Society for Heat Treatment
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• v.17 no.3
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• pp.146-150
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• 2004

Because of the social needs for energy saving and the rigid environmental regulation, the development of light materials and new economical manufacturing technologies have been actively investigated. Recently, the hydroforming of high strength aluminum tube has attracted great interest due to its good strength-to-weight ratio, which could play an important role in lightweighting of automobile. However, the limited formability of high strength aluminum alloys is considered to hinder the active application of the hydroforming process. In this paper, the hydroformability of aluminum tubes with different heat treatments was investigated as the basic research of the hydroforming process for the high strength aluminum tubes.

• Bulletin of the Korean Chemical Society
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• v.14 no.6
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• pp.743-749
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• 1993

The approximate rates and stoichiometry of the reaction of excess lithium tris(dihexylamino)aluminum hydride(LTDHA) with selected organic compounds containing representative functional groups under the standardized conditions (tetrahydrofuran, 0$^{\circ}$C) were studied in order to define the reducing characteristics of the reagent for selective reductions. The reducing ability of LTDHA was also compared with those of the parent lithium aluminum hydride(LAH), lithium tris(diethylamino)aluminum hydride(LTDEA), and lithium tris(dibutylamino)aluminum hydride(LTDBA). In general, the reactivity toward organic functionalities is in order of $LAH{\gg}LTDEA{\geq}LTDBA>LTDHA$. LTDHA shows a unique reducing characteristics. Thus, the reagent reduces aldehydes, ketones, esters, epoxides, and tertiary amides readily. Anthraquinone is cleanly reduced to 9,10-dihydro-9,10-anthracenediol without hydrogen evolution, whereas p-benzoquinone in inert to LTDHA. In addition to that, disulfides are also readily reduced to thiols without hydrogen evolution. However, carboxylic acids, anhydrides, nitriles, and primary amides are reduced slowly. Especially, this reagent reduces aromatic nitriles to the corresponding aldehydes in good yields.

• Journal of Surface Science and Engineering
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• v.51 no.6
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• pp.372-380
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• 2018

Anodization techniques are widely used in the area of surface treatment of aluminum alloys because of its simplicity, low-cost and good corrosion resistance. In this study, we investigated the relationship between the properties (porosity and thickness) of anodic aluminum oxide (AAO) and its corrosion behavior. Aluminum 5052 alloy was anodized in 0.3 M oxalic acid at $0^{\circ}C$. The anodizing of aluminum 5052 was performed at 20 V, 40 V and 60 V for various durations. The corrosion behavior was studied in 3.5 wt % NaCl using potentiodynamic polarization method. Results showed that the pore diameter and thickness increased as voltage and anodization time increased. The relatively thick oxide film revealed a lower corrosion current density and a higher corrosion potential value.