Materials Science Forum Vols. 449-452

Abstract: An optimum route to fabricate the Al2O3/Cu nanocomposites with sound microstructure and improved mechanical properties was investigated. Three powder mixtures of Al2O3 and Cu, CuO or Cu-nitrate were used to obtain Al2O3/5 vol% Cu composites. Microstructural investigations for the composite from Al2O3/Cu-nitrate showed that fine Cu particles, about 150 nm in diameter, were homogeneously distributed within the Al2O3 matrix grains and at the grain boundaries. Fracture toughness of 4.8 MPa
m and strength of 953 MPa were measured for the Al2O3/5 vol% Cu nanocomposites prepared from Al2O3/Cu-nitrate mixture. The toughening and strengthening of the composites are explained by the crack bridging/deflection and the refinement of the microstructure, respectively.

Abstract: Microstructure of hot-pressed Al2O3/Cu composites with a different temperature for atmosphere switching from H2 to Ar has been studied. When the composite atmosphere was switched at 1100°C it lead to a more homogeneous microstructure and the highest fracture strength with smaller deviation than when the atmosphere was switched at 1450°C. The strong sensitivity to atmosphere, especially the oxygen content in the atmosphere, was found to be responsible for observed changes, based upon the interfacial phenomena related to the formation of CuAlO2

Abstract: Geometrical and chemical designs of an implant surface affected the stabilization of implant and the healing of tissue. In this study, effects of surface designs in implants on in vivo behavior and mechanical stability were compared by histological and mechanical analyses. The implants were transversely grafted on dog thighbone and healed for 4 and 8 weeks. The pull-out strength between living bone and implant was evaluated by universal testing machine (UTM).

Abstract: A highly oriented nanostructure of poly(styrene)-b-(ethylene-alt-propylene)-b-(ethylene) (PS/PEP/PE) semicrystalline terblock copolymer was deformed under tensile loading. Roll casting process oriented the microdomains of the terpolymer. Hexagonally ordered PS cylinders subsequently guided the crystallization of the PE block occurring in between the PS cylinders, resulting in the molecular chain orientation of the PE blocks perpendicular to the PS cylinder axis. The structure change of the terblock copolymer under deformation was monitored using Simultaneous Wide Angle X-ray Scattering (WAXS) and Small Angle X-ray Scattering (SAXS). The samples with the load parallel and perpendicular to the cylindrical axis of the PS show their mechanical failures at the strain of approximate 100 % and 210%, respectively. The anisotropic mechanical behavior was interpreted by interplay of the different types of the nano scale domains

Abstract: We have investigated the structures of copper nanowires encapsulated in carbon nanotubes using a structural optimization process applied to a steepest descent method. Results show that the stable morphology of the cylindrical ultra-thin copper nanowires in carbon nanotubes is multi-shell packs consisted of coaxial cylindrical shells. As the diameters of copper nanotubes increases, the encapsulated copper nanowires have the face centered cubic structure as the bulk. The circular rolling of a triangular network can explain the structures of ultra-thin multi-shell copper nanowires encapsulated in carbon nanotubes.

Abstract: Ag doped Hydroxyapatites (Ag-HAp) was prepared through either ion exchange or coprecipitation to compare the durability of antimicrobial effect. In case of ion exchanged Ag-HAp, the microbials reproliferated after 100 h, in spite of the rapid reduction of E.Coli during the initial moment. On the contrary, coprecipitated Ag-HAp effectively suppressed the reproliferation until 1000 h. The difference in durability depending on synthesis route was analysed with respect to the amount of silver released at each interval. In case of ion exchanged Ag-HAp, more than 60% of overall silver was released during initial 10 minitues. On the contrary, coprecipitated Ag-HAp released less than 40% of overall silver during the same period, meaning the comparatively uniform release behavior.

Abstract: We developed a simple method of producing metal oxide nanoparticles by reacting a polyamic acid (PAA) with Cu or Sn metal films. Respective particle size, distribution, and morphology were characterized by transmission electron microscopy (TEM). The morphology of metal oxides dispersed in the polyimide is different in Cu and Sn metal films. The Cu2O particles were formed by the dissolution reaction between the polyamic acid and the Cu films. During curing, PAA dehydrates and converts to polyimide, accompanied by precipitation of Cu2O particles. The synthesized Cu2O particles were randomly dispersed within the polyimide. And their particle size was relatively uniform, having a narrow distribution. Mostly nanosize Cu2O particles were formed in the specimen made from 10 nm thick Cu film and the mixture of nanosize particles and Cu layers were observed in the 30 nm thick Cu film. On the other hands, the Sn film undergoes surface reaction with the polyamic acid. Therefore, the synthesized SnO2 particles existed only at the surface of the substrate. SnO2 particle size distribution was not uniform in the polyimide. Although particles were not distributed uniformly in the polyimide, they were confined in a monolayer. The different particle distributions were attributed to the reactivity difference of PAA with Cu and Sn films.

Abstract: Amplification of the p53 gene using the polymerase chain reaction (PCR) was performed in a silicon-based micro-PCR chip. Metal deposition, photolithography, and anodic bonding were used to fabricate micro-PCR chip and a thermal cycling system with dual peltier devices and PID controller was integrated for controlling the cycling temperature of the PCR mixture. We have demonstrated the amplification of exon 6(182bp) of the p53 gene with the micro-fabricated PCR chip. Temperature control accuracy was within
0.5  . The amplified p53 genes using both conventional PCR and micro fabricated PCR were analyzed using micro-capillary electrophoresis. The PCR performance strongly depends on the cycling temperature, and the Si surface treatment with protein. The micro-PCR products show higher specificity than those of conventional PCR products, and this is attributed to the uniform temperature distribution of the PCR mixture in micro-chip.

Abstract: Application potential of ZnO nanowires grown by MOCVD for atomic force microscope (AFM) probes was evaluated by predicting numerically their structural performances in terms of flexural stiffnesses and natural frequencies. Estimated properties of the nanowires suggested that they are structurally compatible with typical AFM cantilevers while maintaining mechanical stability during operation and they are therefore promising candidates for high aspect ratio probes.

Abstract: The microstructure and photocatalytic characteristics of anodic TiO2 film have been investigated for applications in waste water treatment. The major structure of the fabricated anodic TiO2 film consisted of porous cell structure, of which the main crystal structure bas been found to be anatase type. The photocatalytic efficiencies of anodized TiO2 were evaluated by the degradation rate of aniline blue and the chemical states of anodic film were estimated by P2P spectrum. The reaction order and the rate constant for degradation of dye have been determined to be first dimension and 1.608410-4s. Due to the high bonding strength between TiO2 film, and the substrate and the high specific surface area, the anodized TiO2 can be used as efficient photocatalyst with high reactivity for waste water treatment and water purification.