Thermal Stability of Hexaaluminate Film Coated on SiC Substrate for High-Temperature Catalytic Application

A coating of barium hexaaluminate (Ba_0.75Al_11.0O_17.25) on an α-SiC substrate and the thermal stability of the formed film were investigated for a high-temperature catalytic application. The film prepared by sol coating consisted of BaAl₂Si₂O₈ and α-Al₂O₃ phases and always contained many cracks or exfoliations after heating at 1200C. A hexaaluminate porous film was successfully formed by slurry coating without void formation at the interface between the film and the substrate and exfoliation due to the formation of the intermediate layer after heating at 1200°C. The microstructure of the film remained unchanged, even after heating at 1300°C.     

Hydrolytic degradation of poly[(R)-3-hydroxybutyric acid] in the melt

Poly[(R)-3-hydroxybutyric acid] [R-P(3HB)] was hydrolyzed in high-temperature and high-pressure water at the temperature range of 180-300 °C and for a period of 360 min. The formation, racemization, and decomposition of 3-hydroxybutyric acids (3HBs) and molecular weight change of R-P(3HB) were investigated. The highest yield of (R)-3-hydroxybutyric acid (R-3HB), ca. 80%, was obtained at 200 °C in the hydrolytic degradation periods of 240-360 min. Too-high hydrolytic degradation temperature such as 300 °C induced the decomposition and racemization of formed 3HBs, resulting in decreased yield of R-3HB. The hydrolytic degradation of R-P(3HB) proceeds homogeneously and randomly via a bulk erosion mechanism. The molecular weight of R-P(3HB) decreased exponentially without formation of low-molecular-weight specific peaks originating from crystalline residues. The hydrolytic degradation rates in the melt estimated from M_n changes were lower for R-P(3HB) than for poly(l-lactide) (PLLA) in the temperature range of 180-220 °C. The activation energy for the hydrolytic degradation (ΔE_h) of R-P(3HB) in the melt (180-250 °C) was 30.0 kcal mol⁻¹, which is higher than 12.2 kcal mol⁻¹ for PLLA in the melt in the temperature range (180-250 °C). This study reveals that hydrolytic degradation of PHB in the melt is an effective and simple method to obtain (R)-3HB and to prepare R-P(3HB) having different molecular weights without containing the specific low-molecular-weight chains, because of the removal of the effect caused by crystalline residues.     

Determination of the Temperature Coefficient Distribution of Dielectric Ceramics Using Scanning Photothermal Dielectric Microscopy

Two-dimensional images of the distribution showing the temperature coefficient of the dielectric constant for two types of two-phase composite ceramics composed of TiO₂-Bi₂Ti₄O₁₁ and BaTi₄O₉-BaPr₂Ti₄O₁₂ were obtained using scanning photothermal dielectric microscopy. The images of the TiO₂-Bi₂Ti₄O₁₁ ceramic showed that the TiO₂ and Bi₂Ti₄O₁₁ grains had negative and positive temperature coefficients, respectively, and that the macroscopic averaged temperature coefficient of the ceramic was relatively low because of the cancellation of the opposite signs of the coefficients. On the other hand, the images of the BaTi₄O₉-BaPr₂Ti₄O₁₂ ceramic showed that the temperature coefficient of both grains had the same sign (negative), although their absolute values were quite different.     

The crystallization mechanism of high-cordierite glass

The crystallization mechanism of high-cordierite (2MgO·2Al₂O₃·5SiO₂) from a bulkglass containing B₂O₃ and P₂O₅ as nucleating agents was studied using X-ray diffraction, differential thermal analysis and a polarizing microscope. Thin glass specimens, with a mirror surface, were heated rapidly in an electric furnace in the temperature range 888 to 1363° C for a desired time and then rapidly quenched to room temperature. The normal rate of growth of precipitated cordierite crystals was measured and their morphological change was observed photographically. The growth rate increased with temperature, and the maximum rate occurred at about 1250° C. The crystal morphology was hexagonalprismatic, elongated along thec-axis. Faceted interface morphology was observed when the range of undercooling was from 7 to 174° C. Judging from the relationship between the reduced growth rate and the degree of undercooling, the crystallization mechanism in the range of lower undercooling was governed by a layer growth depending on the surface nucleation mechanism. In the range of higher undercooling, continuous growth was seen and at intermediate undercooling a transition range from a layer growth to a continuous growth was evident.     

Orientation of nanowires consisting of poly(3-hexylthiophene) using strong magnetic field

Nanowires consisting of regioregular poly(3-hexylthiophene) (P3HT) as a conducting polymer were prepared using p-xylene. Magnetic processing of the nanowires was carried out using two superconducting magnets with horizontal (B_max = 8 T) and vertical (B_max = 10 T) directions. The formation of the nanowires was confirmed by atomic force microscopy (AFM) measurement. The results from the AFM images and the polarized absorption spectra on glass plates indicated that the nanowires partly oriented themselves with their long axes, which are parallel to the π–π stacking direction, being perpendicular to the magnetic field. The magnetic orientation is most likely ascribed to anisotropy in the magnetic susceptibilities of the ordered P3HT in the nanowires.     

A facile approach to the fabrication of ultrathin polymer films and application to optical lenses

A facile approach to the fabrication of ultrathin polymer films on a flat or curved substrate is presented. Polymers with unsaturated pendant groups were spin-coated on a photoinitiator tethered surface, which was then photoirradiated and washed with a solvent. The obtained films were uniform, smooth (R_a < 0.2 nm) and exhibited robustness toward solvents. The thickness of the films was determined by the molecular weight of the coated polymer and was not dependent on the initial spin-coated thickness. A mechanism for the formation of the ultrathin film and application to optical lenses is presented.     

Effects of low- or medium-pressure ultraviolet lamp irradiation on Microcystis aeruginosa and Anabaena variabilis

A pure culture of Microcystis aeruginosa or Anabaena variabilis, the representatives of water blooming algae, was exposed to low-pressure (LP) or medium-pressure (MP) UV lamps. Irradiated pure culture suspension was subsequently incubated for 7d under white light fluorescent lamps. During incubation, profiles of the number of cells, DNA damage and photosynthetic activity were determined. When UV fluence was 600mJ/cm(2), M. aeruginosa cell numbers decreased throughout the 7-d incubation period, to produce 1.5log reduction (LP) or 1.2log reduction (MP) compared with control. The amount of DNA damage was 2.02x10(-4) ESS/base (LP) and 3.42x10(-4) ESS/base (MP) just after UV irradiation, which became 0.05x10(-4) ESS/base and 0.23x10(-4) ESS/base, respectively, after 3d incubation. However, cell number kept decreasing, even after DNA repair. Photosynthetic activity decreased by 1.5log within 1d (LP) or 3d (MP). Thus, reduction in photosynthetic activity could contribute to the reduction in M. aeruginosa cell numbers. A. variabilis cell numbers reduced by 2.3log (LP) or 2.2log (MP) during the 7-d incubation period; however, after DNA damage repair, cell number began to increase. The amount of DNA damage was 6.07x10(-4) ESS/base (LP) and 4.48x10(-4) ESS/base (MP) just after UV irradiation, which became 0.23x10(-4) ESS/base and 0.40x10(-4) ESS/base, respectively, after 3d incubation. No reduction was observed in photosynthetic activity/cell. Therefore, DNA damage is the main contributor of the reduction in cell number of A. variabilis.     

Amplified fragment length polymorphism of the AWA1 gene of sake yeasts for identification of sake yeast strains

Sake yeasts are used for sake brewing and have a crucial role in the quality of sake, since they produce not only ethanol but also various compounds that provide sake flavors. Therefore, the appropriate selection and monitoring of a strain used in sake mash is important. However, the identification of specific sake yeast strains has been difficult, because sake yeasts have similar characteristics in taxonomic and physiological analyses. We found amplified fragment length polymorphisms (AFLPs) in the PCR products of the AWA1 gene of sake yeast strains. The AWA1 gene encodes a cell wall protein that is responsible for foam formation in sake mash. This polymorphism of the AWA1 gene can be used for the identification of sake yeast strains.     

Crystallographic analysis for acicular ferrite formation in low carbon steel weld metals

Inclusions contributing to acicular ferrite nucleation were investigated from a crystallographic point of view in low carbon low alloy steelweld metals. The samples from electro slag welding (ESW) and submerged arc welding (SAW) deposits with various cooling rates were prepared in this study. In those samples, intragranular acicular ferrite formation was observed from inclusions. The inclusions contributing to acicular ferrite formation were of multi-phase type consisting of amorphous phase, spinel type and MnS. They were surrounded by a Ti-enriched layer. It was confirmed by selected area diffraction patterns and energy-dispersive X-ray spectrometer analyses that the Ti-enriched layer was TiO. The acicular ferrite had a Baker–Nutting orientation relationship with the TiO layer on the inclusion surface. The misfit was 3.0% at the interface between the acicular ferrite and TiO. Therefore, it is considered that TiO on the inclusion surface contributes to the heterogeneous nucleation of acicular ferrite by small lattice misfit. However, themorphologies of ferrite growth which nucleated from inclusions were different in both samples. Whereas the growth of ferrites nucleated from TiO was enough in ESW, the size of nucleated ferrite in SAW was a few hundred millimetres in size. In the early stage of nucleation from TiO, ferrite had small deviation from Kurdjumov–Sachs orientation relationship (K–S relationship) in both ESW and SAW. However, there was a difference in the growth stage of ferrite. The ferrite orientations were gradually changed to fit to the K–S relationship in ESW. On the other hand, the nucleated ferrite in SAW stopped growing and the newly nucleated ferrite which had K–S relationship prior to austenite was formed adjacently because of large super cooling due to small heat input.