Key Engineering Materials Vols. 277-279

Abstract: We present the result of photometric variability investigation for stars in the field of M67. The old open cluster M67, one of the most studied open clusters, shows the sign of significant main-sequence binary population in its color-magnitude diagrams. Identification of eclipsing binaries and follow-up studies will enable us to study the nature of binary population in most direct manner. We used approximately 350 images from the BATC (Beijing-Arizona-Taipei-Connecticut) data archive to examine variability within one square degree field centered on M67. A total of 18 stars were classified to be real variables. Our new discoveries include seven eclipsing binary systems of which two are likely to be W UMa systems. All of these variables were found using the phase dispersion minimization (PDM) method developed by Shin and Byun[11].

Abstract: The synthesis of nearly monodisperse, roughly spherical, and non-aggregated maghemite (g-Fe2O3) nanoparticles (average diameter = 5.5 nm, standard deviation = 0.7 nm over 100 particles) is reported. We utilized a sol-gel reaction of common ferric salt in reverse micelles and then, crystallization of the gel particles by reflux. The nanoparticles show superparamagnetic behavior and are expected to be useful for clinical applications.

Abstract: The effect of a longitudinal magnetic field and the dielectric constants mismatch of a size- quantized wire and surrounding medium on the impurity scattering of charge carriers is considered. The expressions for the momentum relaxation rate are carried out for scattering on charged Coulomb centers located on the wire axis. The dependences of the momentum relaxation rate on the magnetic field induction, dielectric inhomogeneity parameter, and also on the wire radius are obtained.

Abstract: Water/CO2 (W/C) microemulsion was formed by sodium salt of bis(2,2,3,3,4,4,5,5-octa fluoro-1-pentyl)-2-sulfosuccinate and the phase behavior of this emulsion was investigated in supercritical state. In addition, the change of the phase behavior of W/C microemulsion was observed when various organic solvents were added into this microemulsion. The added organic solvents are isopropanol, n-propanol, ethanol, methanol, pyridine, 2-methoxyethanol, tetrahydrofuran, acetonitrile, acetone, and 1,4-dioxane. According to the results, the phase behavior of W/C microemulsion depended on the temperature and pressure and the microemulsion was thermodynamically stable in the special range of pressure. In case of W/C microemulsion with organic solvents, the phase behavior of this system was affected by the solubility parameter of organic solvents.

Abstract: The interband light absorption in spherical quantum dot (QD) of semiconductors connected with the charged and neutral exciton-donor complexes are studied theoretically. The oscillator strength for interband optical transition from valence band to the ground state of excitondonor complex in spherical QD has been investigate. The calculations were performed in the cases of infinite and finite potential barrier of QD. The dependences of the oscillator strength on the radius of the QD were obtained. It was shown that the quantum confinement gives rise a giant oscillator strength per impurity.

Abstract: Mesoporous carbon (MCs) was synthesized using mesoporous silica as a template. Prepared mesoporous carbon materials were found to have high surface area and large pore volume with uniform pore size. Resulting materials showed a different pore arrangement from mesoporous silica templates. Pt catalysts supported on mesoporous carbon prepared were applied to an anode catalyst for Direct Methanol Fuel Cell (DMFC). Results indicate that a mesoporous carbon having 3-dimensional pore system (3D-MC) had higher catalytic activity than 2-dimensional one (2D-MC) due to a favorable pore structure in methanol electro-oxidation.

Abstract: Site-defined metal microstructure was fabricated on the pre-designed organic template via a surface modification of Si(100) wafer. Site-defined substrate with octadecyltrichlorosilane (OTS) was oxidized by AFM (Atomic Force Microscopy) at threshold voltage (Vo). Terminal group (-CH3) of OTS was changed into carboxyl group (-COOH). Then, locally modified monolayer surface was used to induce the site-selective self-assembly of different materials (organic, metal, and semiconductor), according to the predefined patterns. The target metal selected is copper ions for the feasibility examination of conductive metal line fabrication

Abstract: Poly(methyl-co-cyclosiloxane bearing silsesquioxane)s (P(M-co-CSSQs)) were prepared. Using poly(e-caprolactone) (PCL) as a template, PCL / P(M-co-CSSQ) nanohybrid films were fabricated. The electrical, morphological, and mechanical properties of the PCL / P(M-co-CSSQ) films were investigated. The dielectric constant of a cured PCL / P(M-co-CSSQ) film at 420°C scaled down from 2.55 to 2.05 and refractive index from 1.41 to 1.33 when 20 vol. % of the PCL was admixed with the polymer matrix. The elastic modulus and hardness of the cured PCL / P(Mco- CSSQ) (2:8, vol./vol.) film were 2.50 and 0.32 GPa, respectively, showing dependency on the PCL content.

Abstract: In this paper, we present a reusable quartz master fabricated by electron-beam lithography and the results of the preliminary test of injection molding using the reusable quartz master. Since patterned structures of photoresist can be easily damaged by demolding process of nickel stamper and master, a master with photoresist cannot be reused in stamper fabrication process. In this work, we have made it possible of the repeated use of master by directly patterning on quartz in nickel stamper fabrication process. We have developed a 100nm-pit sized reusable quartz master with intaglio carving patterns of finer sizes than those of DVD (400nm) and blue-ray disc (200nm). In the preliminary test of the injection molding, we have found optimum injection molding conditions using polypropylene.

Abstract: We have investigated structural phases of potassium in carbon nanotubes using a structural optimization process applied to an atomistic simulation method. As the radius of the carbon nanotubes is increased, various structural phases ranging from an atomic strand to multi-shell packs composed of coaxial cylindrical shells and helical, layered, and crystalline structures are found to emerge. Numbers of helical atom rows composed of coaxial tubes and orthogonal vectors of a circular rolling of a triangular network can explain multi-shell phases of potassium in carbon nanotubes.