Journal of Powder Materials

Jae-Pyoung Ahn

4 Articles

MicrostructuraL Characteristics During Hydrogen Desorption of Mechanical Milled TiH₂: S. Jung, Hyun-Sung Jung, Jae-Pyoung Ahn, Jong-Ku Park; J Korean Powder Metall Inst. 2006;13(3):199-204.; DOI: https://doi.org/10.4150/KPMI.2006.13.3.199

Abstract PDF: We manufactured the metal hydrides of (Ti_0.88Mg_0.12)H_2 using a very easy and cheap way that Ti-12%Mg blending powder was mechanically milled with liquid milling media such as isopropyl alcohol (C_3H_8O, containing oxygen) and hexane (C_6H_14, no oxygen) as hydrogen source. The (Ti_0.88Mg_0.12)H_2 synthesized in isopropyl alcohol contained the high oxygen of 11.2%, while one in hexane had the low oxygen content of 0.7%. Such a difference of oxygen content affected the dehydriding behavior, phase transformation, and microstructural evolution at high temperature, which was investigated through X-ray diffraction and DSC measurements, and electron microscope observations.

Fabrication of Transition-metal-incorporated TiO₂ Nanopowder by Flame Synthesis: Hoon Park, Hyunseock Jie, Seung-Yong Lee, Jae-Pyoung Ahn, Dok-Yol Lee, Jong-Ku Park; J Korean Powder Metall Inst. 2005;12(6):399-405.; DOI: https://doi.org/10.4150/KPMI.2005.12.6.399

Abstract PDF: Nanopowders of titanium dioxide (TiO_2) incorporating the transition metal element(s) were synthesized by flame synthesis method. Single element among Fe(III), Cr(III), and Zn(II) was doped into the interior of TiO_2 crystal; bimetal doping of Fe and Zn was also made. The characteristics of transition-metal-doped TiO_2 nanopowders in the particle feature, crystallography and electronic structures were determined with various analytical tools. The chemical bond of Fe-O-Zn was confirmed to exist in the bimetal-doped TiO_2 nanopowders incorporating Fe-Zn. The transition element incorporated in the TiO_2 was attributed to affect both Ti 3d orbital and O 2p orbital by NEXAFS measurement. The bimetal-doped TiO_2 nanopowder showed light absorption over more wide wavelength range than the single-doped TiO_2 nanopowders.

Shapes of ZnO Nanostructures Grown in the Aqueous Solutions: Yeon-Ik Jang, Hoon Park, Seung-Yong Lee, Jae-Pyoung Ahn, Jong-Ku Park; J Korean Powder Metall Inst. 2005;12(4):284-290.; DOI: https://doi.org/10.4150/KPMI.2005.12.4.284

Abstract PDF: ZnO nanostructures with various shapes were synthesized under ambient pressure condition by a wet chemical reaction method. Nanorods of ZnO with hexagonal cross-section and their aggregates with radiate shape were synthesized. Precursor concentration affected considerably the shape evolution of ZnO nanorods. Low precursor concentration was proved to be more preferable to the growth of ZnO nanorods, which is attributed to the intrinsic characteristics of chemical reaction in the synthesis of ZnO from zinc compounds.

Synthesis of TiN/TiB₂/Ti-silicides Nanocomposite Powders by Mechanochemical Reaction and its Reaction Mechanism: Young-Whan Cho, Ji-Woo Kim, Jae-Hyeok Shim, Jae-Pyoung Ahn, Kyu-Hwan Oh; J Korean Powder Metall Inst. 2005;12(4):273-278.; DOI: https://doi.org/10.4150/KPMI.2005.12.4.273

Abstract PDF: Nanostructured TiN/TiB_2/TiSi_2 and TiN/TiB_2/Ti_5Si_2 composite powders have been prepared by mechanochemical reaction from mixtures of Ti, BN, and Si_3N_4 powders. The raw materials have reacted to form a uniform mixture of TiN, TiB_2 and TiSi_2 or Ti_5Si_3 depending on the amount of Si_3N_4 used in the starting mixtures, and the reaction proceeded through so-called mechanically activated self-sustaining reaction (MSR). Fine TiN and TiB_2 crystallites less than a few tens of nanometer were homogeneously dispersed in the amorphous TiSi_2 or Ti_5Si_3 matrix after milling for 12 hours. These amorphous matrices became crystalline phases after annealing at high temperatures as expected, but the original microstructure did not change significantly.

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