Journal of Powder Materials

C. Rhee

4 Articles

Study of Hydrolysis of Al Powder and Compaction of Nano Alumina by Spark Plasma Sintering(SPS): Y. Uhm, M. Lee, C. Rhee; J Korean Powder Metall Inst. 2005;12(6):422-427.; DOI: https://doi.org/10.4150/KPMI.2005.12.6.422

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Abstract PDF: The Al_2O_3 with various phases were prepared by simple ex-situ hydrolysis and spark plasma sintering (SPS) process of Al powder. The nano bayerite (beta-Al(OH)_3) phase was derived by hydrolysis of commercial powder of Al with micrometer size, whereas the bohemite (AlO(OH)) phase was obtained by hydrolysis of nano Al powder synthesized by pulsed wire evaporation (PWE) method. Compaction as well as dehydration of both nano bayerite and bohemite was carried out simultaneously by SPS method, which is used to fabricate dense powder compacts with a rapid heating rate of 100°C per min. under the pressure of 50MPa. After compaction treatment in the temperature ranges from 100°C;to; 1100°C, the bayerite and bohemite phases change into various alumina phases depending on the compaction temperatures. The bayerite shows phase transition of Al(OH)_3toeta-Al_2O_3totheta-Al_2O_3toalpha-Al_2O_3 sequences. On the other hand, the bohemite experiences the phase transition from AlO(OH) to gamma-Al_2O_3;at;350°C. It shows AlO(OH) gamma-Al_2O_3todelta-Al_2O_3toalpha-Al_2O_3 sequences. The gamma-Al_2O_3 compacted at 550°C shows a high surface area (138m2/g).

The study of Synthesis of Dihydropyrimidine for Cardiotropic Drugs Using New Catalysts on the Basis of Nano Cu Oxides: Y. Uhm, M. Lee, C. Rhee; J Korean Powder Metall Inst. 2005;12(6):441-446.; DOI: https://doi.org/10.4150/KPMI.2005.12.6.441

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Abstract PDF: The copper oxide nano powders were synthesized by levitational gas condensation (LGC) method, and were applied to catalyst to fabricate 3,4-dihydropyrimidin-2-(1H)-one. Processes of adsorption of Biginelli reaction reagents on the copper nanooxide surface Cu_2O°CuO were studied by IR-spectroscopy. It was shown that benzaldehyde coordination, acetoacetic ether on the oxide surface is carried out with participation of carbonyl fragments, urea by N-H bonds which affects positively on the reagents reactivity.

Installation for Preparing of Nanopowders by Target Evaporation with Pulsed Electron Beam: S. Sokovnin, Yu. Kotov, C. Rhee; J Korean Powder Metall Inst. 2005;12(3):167-173.; DOI: https://doi.org/10.4150/KPMI.2005.12.3.167

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2 Citations

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Production of weakly agglomerated nanopowders with the characteristic size of about 10 nm and a narrow particle size distribution is still a topical problem especially if the matter is an acceptable output (>50 g/hour), a high purity of the final product, and a low (energy consumption. The available experience and literature data show that the most promising approach to production of such powders is the evaporation-condensation method, which has a set of means for heating of the target. From this viewpoint the use of pulsed electron accelerators for production of nanopowders is preferable since they allow a relatively simple adjustment of the energy, the pulse length, and the pulse repetition rate. The use of a pulsed electron accelerator provides the following opportunities: a high-purity product; only the target and the working gas will interact and their purity can be controlled; evaporation products will be removed from the irradiation zone between pulses; as a result, the electron energy will be used more efficiently; adjustment of the particle size distribution and the characteristic size of particles by changing the pulse energy and the irradiated area. Considering the obtained results, we developed a design and made an installation for production of nanopowders, which is based on a hollow-cathode pulsed gas-filled diode. The use of a hollow-cathode gas-filled diode allows producing and utilizing an electron beam in a single chamber. The emission modulation in the hollow cathode will allow forming an electron beam 5 to 100 ms long. This will ensure an exact selection of the beam energy. By now we have completed the design work, manufactured units, equipped the installation, and began putting the installation into operation. A small amount of nanopowders has been produced.

Citations

Citations to this article as recorded by

Effect of the Enhanced Breakdown Strength in Plasma-Filled Optical System of Electron Beam Formation
V. I. Gushenets, A. S. Bugaev, E. M. Oks
Russian Physics Journal.2018; 60(9): 1515. CrossRef
Production of Nanopowders Using Pulsed Electron Beam
S. Yu. Sokovnin, V. G. Il'Ves
Ferroelectrics.2012; 436(1): 101. CrossRef

Dispersion Properties and Photocatalytic Activities of TiO₂ Powders Obtained by Homogeneous Precipitation Process at Low Temperature in a Acrylic Resin: S. Woo, W. Kim, C. Rhee; J Korean Powder Metall Inst. 2004;11(6):503-509.; DOI: https://doi.org/10.4150/KPMI.2004.11.6.503

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Abstract PDF: Dispersion stabilities and photocatalytic activities of rutile TiO_2 powders with unique nano-structure synthesized by homogeneous precipitation process at low temperature(HPPLT) have been investigated in the acrylic resin containing fluorostyrene in the range of 0~0.16 mole. Isoelectric point of TiO_2 in the acrylic resin placed in the neutral region whereas that of TiO_2 in the water placed in the acidic region, indicating that zeta potential and agglomeration of TiO_2 powder is strongly dependent on the pH and the type of solvent. To prepare an adhesion, an acrylic resin containing fluorostyrene was synthesized by a radical polymerization. The adhesion of coating layer was increased with increasing fluorostyrene's contents without changing the dispersion stabilities and degrading photocatalytic properties.

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