High resolution images of Mo2C(0001)- structure by scanning tunneling microscopy

A C-terminated structure on Mo₂C(0001) was observed by scanning tunneling microscopy. The structure was observed as a honeycomb structure with dark depressions corresponding to C atoms which make up the lattice. High resolution imaging was possible at low tunneling resistance less than 1 MΩ. Each C atom appears as a shallow sombrero protrusion predicted by theoretical calculations of C atoms on a metal substrates. It is concluded that the C atoms occupied threefold hollow sites of the (1×1) Mo layer of the substrate and a model for the structure is proposed.     

Preparation and properties of porous glass using fly ash as a raw material

The porous glasses were prepared by a conventional phase separation method using coal fly ash as a raw material, and the properties of these porous glasses were investigated. The composition of coal fly ash is basically composed of SiO₂–Al₂O₃–Fe₂O₃–CaO system and the SiO₂–B₂O₃–Al₂O₃–CaO–Na₂O system of glass was chosen as base glass composition. The pore diameter increases proportional to cube root of heating time (t^1/3), however, the early stage of phase separation is not clear. It is estimated that the rate determining step may be the diffusion process of structural units involving oxygen ions and the phase separation may take place by the nucleation and growth mechanism, and the relatively larger pores of above 1 μm can be obtained easily. The chemical composition of porous glasses is SiO₂–B₂O₃–Al₂O₃(–CaO–Na₂O). A relatively large amount of fly ash (>40%) can be used successfully for the preparation of porous glass.     

Surface phonons of LaB6(100): deformation of boron octahedra at the surface

The surface phonon dispersion of clean LaB₆(100) surface has been measured by means of high resolution electron energy loss spectroscopy. Eight vibrational modes, of which most are located in the energy gaps between the bulk phonon bands, have been detected. The lattice dynamical calculation of a slab-shaped crystal based on a force constant model has reproduced these experimental dispersion curves, which indicates the large increase in the force constant of interoctahedral boron-boron bond at the surface by 25%, and the large decrease in the force constants of intraoctahedral boron-boron bonds at the surface by 25–50%. These changes together with the analysis of the bulk phonon structure of metal hexaborides strongly suggest that the boron octahedra at the surface are expanded by about 0.004 nm parallel to the surface.     

Synthesis of hyperbranched polymer having binaphthol units via oxidative cross‐coupling polymerization

The oxidative coupling polymerization of triphenylamine derivatives having 2‐naphthol moieties with a CuCl‐2,2′‐isopropylidenebis(4‐phenyl‐2‐oxazoline) catalyst under an O₂ atmosphere was carried out. The polymerization of the monomer bearing both the hydroxynaphthoate and naphthol units afforded a hyperbranched polymer with a high cross‐coupling selectivity of > 99%, which showed a number‐average molecular weight of 20.3 × 10³. In addition, the obtained polymer was quite soluble in THF. The photoluminescence and electrochemical properties of the obtained polymers were also examined. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1034–1041, 2008     

An autosampler with a short transfer line for Curie point pyrolysis capillary gas chromatography

A new multichannel autosampler which can automatically analyze up to twenty samples in sequence has been developed for Curie point pyrolysis – capillary GC. Compared with a previous system [1] the transfer line between the pyroysis unit and chromatograph is shorter, and thus has less dead volume, and can be operated at a higher temperature (300 °C). The relative yields of higher boiling point, highly polar, and thermally labile pyrolysates generated from polymers, and the reproducibility, were better than those obtained from the previous autosampler. To facilitate rapid operation an additional flow controller is installed on the new device to shorten the time taken to purge air from the sampler.     

Fe-Ni-Zr films with large perpendicular anisotropy deposited on PEN tape by facing targets sputtering

One of the origins of perpendicular magnetic energy of Fe-Zr films may be attributed to the structural inhomogeneity of Fe-rich alloy crystallites in a Fe-Zr amorphous matrix. Fe-Ni-Zr films deposited on PEN tape substrates at about 90°C exhibited large K_u with appropriately large 4πM_s suitable for flexible recording media.     

Ultrahigh Electron Emissive Carbon Nanotubes with Nano-sized RuO2 Particles Deposition

Multi-wall carbon nanotubes (MWNTs) have a great commercial potential as electron field emitters, but suffer from fundamental problems such as stability and brightness. By depositing the MWNTs with nano-sized ruthenium dioxide (RuO₂) particles, a new high performance emitter has been developed. When compared to MWNTs, the MWNTs impregnated with 1–2 nm sized RuO₂ have superior and more efficient electrical characteristics. MWNTs supported by a silicon substrate showed a reduction in the onset voltage from 5.4 to 4 V/μm after RuO₂ impregnation. The long-term stability of the impregnated MWNTs is also demonstrated with only a 20% increase in applied voltage required after 700 h operation at 40 mA/cm².