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Ab-initio Simulations in order to improve processing of Nanoceramics
WilfriedWunderlich,KoichiNiihara 한양대학교 세라믹연구소 2003 Journal of Ceramic Processing Research Vol.4 No.1
Nanomaterials have been classified into inter- and intra-nanomaterials, but recent research projects focus on single molecules, like polymeric side chains or atomic monolayers. In these nano-dimensions the manufacturing becomes expensive and even characterization is a challenge. Hence, simulations are necessary to understand and optimize the properties of ceramic materials in terms of powder shape, crystals or at interfaces. The ab-initio calculations need no adjusting parameters and calculate the electron wave function in the potential of the atom core. The calculations presented in this overview paper are performed with the DvXa method focussing on three examples and show how these calculations of the electronic structure can be used for improving the ceramic processing. The first example considers how the electronic band structure of nanoparticles changes as a function of the particle size. The second example considers the substitution of atoms in an electro-ceramic material. The last example shows, how the organic macromolecule Eosin on top of a crystalline ZnO surface is bonded, which is important to increase the efficiency of solar cells or photo-catalytic reactions.
Laser microfabrication of alumina-silicon carbide nanocomposites
Kwang-Ryul Kim,김재훈,Kwang-Ho Kim,KoichiNiihara,Young-Keun Jeong 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.4
Alumina-silicon carbide nanocomposites have many potential applications, because of their excellent mechanical properties. However, they are very difficult to fabricate for MEMS devices due to the difficulty in machining these nanocomposites. Alumina-silicon carbide nanocomposites sintered by a pressureless-sintering process have been fabricated using state-of-theart laser microfabrication technology to find a way out of this difficulty. A femto-second laser with a specially equipped optical system was prepared and tested for nano and micro scale microfabrications of the material. The relationship between material ablation rate and energy fluence is theoretically investigated. In addition, the relationship is verified using cross-sectional SEM analysis of laser microfabricated alumina and alumina-silicon carbide samples. It is found that the nanocomposites are clearly fabricated using the femto-second laser and the surface roughness is acceptable for any MEMS parts.
Satoshi Seino,Takuya Kinoshita,Yohei Otome,Takashi Nakagawa,Kenji Okitsu,Tadachika Nakayama,Tohru Sekino,KoichiNiihara,Takao A. Yamamoto 한양대학교 세라믹연구소 2004 Journal of Ceramic Processing Research Vol.5 No.2
Nanocomposite particles composed of gold and iron oxide were synthesized with various ratios of gold and iron oxide in an aqueous phase using γ-rays. Iron oxide nanoparticles of γ-Fe2O3 or Fe3O4 were used as a magnetic phase on which gold nanoparticles with average diameters of 5-10 nm were supported. The efficiency of magnetic separation of biomolecules by the present nanocomposite particles was investigated using glutathione as a model compound. The amount of glutathione magnetically separated was significantly enhanced by the supported gold nanoparticles.