Nanocomposites and Nanoporous Materials VIII

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Authors: Jong Min Lee, Young Kyu Hwang, Ajit Singh Mamman, Sang Min Lee, Do Young Hong, Kook Young Ahn, Jong San Chang
Abstract: Influence of steam, loading amounts of Pd (viz., 0.7, 2.1, 5.4 wt %) and other process parameters (viz. GHSV and temperature) on methane-based MCFC anodeeffluents over Pd-based La2O3-Al2O3 supported on honeycomb substrate have been investigated. TGA study reveals precise temperature of decomposition of Pd-O in catalytic combustion at high temperature. An increase in methane conversion at elevated temperature is attributable to decomposition of PdO to Pd active phase. The XRD analysis of spent catalysts suggests that the reflections corresponding to PdO gradually become weaker with increase in the Pd loading. The addition of 4% water in the feed decreases the methane conversion due to the reversible reaction of PdO with water adduct resulting in the formation of inactive Pd(OH)2 phase. However, the methane conversion remains unaffected and increases monotonously with 100% water concentration in the feed.
Authors: Hyun Gi Jung, Young Hun Cheong, In Dong Han, So Jin Kim, Sung Goon Kang
Abstract: Mechanical processing of nanocrystalline Y2O3 and transition alumina (AlOOH) was performed, using a Spex mixer mill under atmospheric conditions, to synthesize yttrium aluminum garnet (YAG, Y3Al5O12) powder at lower temperature. The reaction of nanocrystalline Y2O3 with AlOOH was activated by mechanical energy and use of fine instead of heat energy, leading to the direct formation of pure YAG without second phases at a lower temperature, 800°C, which is significantly lower than that required by the conventional solid-state reaction process.
Authors: Jung Goo Lee, Ryusuke Nakamura, Daisuke Tokozakura, Hideo Nakajima, Hirotaro Mori, Jong Hoon Lee
Abstract: The formation of hollow zinc oxide has been studied by oxidation and subsequent thermal treatment of nanometer-sized zinc particles using in-situ TEM. The zinc particles produced under UHV condition were exposed to air at room temperature for 0.6 ks, which resulted in the formation of oxide layer with thickness of 3 nm. Subsequent heating inside UHV chamber of TEM induced the evaporation of the inner zinc, which resulted in the formation of hollow zinc oxide. The produced hollow zinc oxide had the wurtzite structure. Based upon the vapor pressure of the inner zinc, it seems reasonable to consider that the internal zinc vapor leaks away through the interface between the oxide layer and the amorphous carbon film used as a supporting substrate.
Authors: Hae Sic Kim, Hyun Suk Kang, Gyo Jin Chu, Hong Sik Byun
Abstract: The antifungal effectiveness against rose powdery mildew using antimicrobial nanosilver colloidal solution was investigated. Double-capsulized nanosilver was prepared by chemical reaction of silver ion with aid of physical method, reducing agent and stabilizers. The average diameter of nanosilver was about 1.5 nm. They were highly stable and very well dispersive in aqueous solution. The Transmission electron microscopy and UV-vis spectrometer were used for measurements of size analysis and their stability, respectively. The nanosilver colloidal solution of concentration of 5000 ppm was diluted in 10 ppm of 500 kg and sprayed at large area of 3306 m2polluted by rose powdery mildew. The white rose powdery mildew fade out above 95 % after 2 days and was not recurred for a week. The antifungal effects were observed by an optical microscope and photographs.
Authors: Yu Peng Guo, Nam Hee Lee, Hyo Jin Oh, Cho Rong Yoon, Chang Kyu Rhee, Kyung Sub Lee, Sun Jae Kim
Abstract: In this study, we have successfully developed the technology to grow the nanotube array thin films from dip-coated titania using hydrothermal method. The nanotube array thin film strongly adhered onto the substrate, was formed in short time reaction at 140°C. Even a self-supporting films, consisted of vertically aligned nanotube in large part, were formed after long time reactions at 140°C with 10 μm in thickness. The most probable formation mechanism of TiO2-based nanotube array thin films is discussed.
Authors: So Jin Kim, Won Kyu Han, Sung Goon Kang, Min Su Han, Young Hun Cheong
Abstract: Lanthanum hydroxide and oxide were prepared by the precipitation method in an aqueous medium at room temperature. The precipitate was examined using thermal analysis, X-ray diffraction and Scanning Electron Microscopy to investigate the phase evaluation and the thermal transformation by decomposition. The as-precipitated powder from the precipitation method was hexagonal La(OH)3. The lanthanum hydroxide was decomposed to oxide in two-steps as La(OH)3 → LaOOH + H2O and 2LaOOH → La2O3 + H2O.
Authors: In Hyuck Song, Yong Jin Kim, Hai Doo Kim, Dong Pyo Kim
Abstract: In this study, two-dimensional (2D) ordered macroporous SiCN ceramics were prepared by infiltrating sacrificial colloidal silica (SiO2) templates with the low molecular weight preceramic polymer, polysilazane. This was followed by a thermal curing step, pyrolysis at 1250°C in a N2 atmosphere, and finally the removal of the templates by etching with diluted HF. In particular, 100large-scale monolayer silica crystals were prepared on the cleaned Si substrates by spin coating. Two-dimensional SiCN ordered pore arrays were fabricated by a solution-dipping template strategy.
Authors: Young Kyu Hwang, Ajit Singh Mamman, K. R. Patil, Lee Kyung Kim, Jin Soo Hwang, Jong San Chang
Abstract: Reflectometry technique has been successfully applied to investigate the correlation between the porosity and optical property (refractive index) of the ordered mesoporous thin film deposited on silicon wafer substrates. The measured optical spectra were simulated by the Effective Medium approximation model. The reflectometry technique has been found to be appropriate for the measurement of thickness of thin films as well as thick layer films. The mesoporous silica films prepared from tri-block copolymer (F-127) as a surfactant and polypropylene oxide as a swelling agent were subsequently exposed to the ammonia vapors to enhance thermal stability and shrinkage minimization of the film that results in increased film thickness.

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