- Formation of Aluminum Hydroxides by Hydrolysis of Nano and Micro Al Powders
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Young Oh, Geunhee Lee, Joong Park, Chang Rhee, Whung Kim, Do Kim
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J Korean Powder Metall Inst. 2005;12(3):186-191.
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DOI: https://doi.org/10.4150/KPMI.2005.12.3.186
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- A formation of aluminum hydroxide by hydrolysis of nano and micro aluminum powder has been studied. The nano aluminum powder of 80 to 100 nm in diameter was fabricated by a pulsed wire evaporation (PWE) method. The micro powder was commercial product with more than 10;µm in diameter. The hydroxide type and morphology depending on size of the aluminum powder were examined by several analyses such as XRD, TEM, and BET. The hydrolysis procedure of micro aluminum powder was different from that of nano aluminum powder. The nano aluminum powder after immersing in the water was transformed rapidly to a nano fibrous boehmite, accompanying with a remarkable temperature increase, and then further transformed slowly to a stable bayerite. However, the micro powder was changed to the stable bayerite slowly and directly. The formation of fibrous aluminum hydroxide from nano aluminum powder might be due to the fine cracks which were formed by hydrogen gas pressure on the surface hydroxide layer during hydrolysis. The nano powder with large specific surface area and small size reacted more actively and faster than the micro powder, and transformed to meta-stable hydroxide in relatively short reaction time. Therefore, the formation of fibrous boehmite is special characteristic of hydrolysis of nano aluminum powder.
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Citations
Citations to this article as recorded by  - Synthesis and Characterization of Glold Nanofluid Prepared by the Solution Plasma Processing
Yong-Kang Heo, Sang-Yul Lee
Journal of Korean Powder Metallurgy Institute.2010; 17(4): 342. CrossRef - A Study on Thermal Properties of Ethylene Glycol Containing Copper Oxide Nanoparticles
Chang-Kyu Kim, Gyoung-Ja Lee, Chang-Kyu Rhee
Journal of Korean Powder Metallurgy Institute.2010; 17(4): 276. CrossRef
- Effect of Post-heat Treatment on Fatigue Strength of Thermally-Sprayed Stellite Alloy on Steel
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Jeong Oh, Jun Komotori, Chang Rhee
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J Korean Powder Metall Inst. 2005;12(2):106-111.
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DOI: https://doi.org/10.4150/KPMI.2005.12.2.106
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Abstract
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- The effect of post-heat treatment on the coating characteristics and the fatigue strength of the gas flame thermally sprayed Stellite alloy coatings on 0.35% carbon steel were investigated. The fatigue fracture surfaces of the heat treated samples were observed using SEM (Scanning Electron Microscopy). For as-sprayed samples, there was considerable scattering in the fatigue life due to the presence of the pores in the coating. After the post-heat treatment to improve the microstructural characteristics of the coating layer, the fatigue strength of the specimens was greatly improved, increasing with increasing the coating thickness. For the specimens with the 0.3mm and 0.5mm thick coating, the fatigue cracks originated in the substrate region just below the interface. On the contrary, for the specimens with the 1.0mm thick coating, they nucleated at the pore within the coating, and the fatigue strength was 2.6 times higher than that of the substrate due to the high fatigue resistance of the coating.
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