Free Volume of Network-Forming Oxide Glasses in the Systems P2O5-(GeO2,TeO2,Sb2O3,V2O5)

The free-volume fraction (V_f) defined by Simha and Boyer was measured for network-forming oxide glasses in the systems P₂O₅-(GeO₂, TeO₂,Sb₂O₃.V₂O₅). The V_f values varied from 0.06 to 0.25. The systems P₂O₅-TeO₂: and P₂O₅-Sb₂O₃ have V_f∼0.1, which is near the magnitude of the free-volume fraction for normal metaphosphate glasses and many organic high polymers.     

Fluidized-bed synthesis of sub-millimeter-long single walled carbon nanotube arrays

The rapid growth method for vertically aligned, single walled carbon nanotube (SWCNT) arrays on flat substrates was applied to a fluidized-bed, using ceramic beads as catalyst supports as a means to mass produce sub-millimeter-long SWCNT arrays. Fe/Al₂O_x catalysts were deposited on the surface of Al₂O₃ beads by sputtering and SWCNTs were grown on the beads by chemical vapor deposition (CVD) using C₂H₂ as a feedstock. Scanning electron microscopy and transmission electron microscopy showed that SWCNTs of 2–4 nm in diameter grew and formed vertically aligned arrays of 0.5 mm in height. Thermogravimetric analysis showed that the SWCNTs had a catalyst impurity level below 1 wt.%. Furthermore, they were synthesized at a carbon yield as high as 65 at.% with a gas residence time as short as <0.2 s. Our fluidized-bed CVD, which efficiently utilizes the three-dimensional space of the reactor volume while retaining the characteristics of SWCNTs on substrates, is a promising option for mass-production of high-purity, sub-millimeter-long SWCNT arrays.     

One second growth of carbon nanotube arrays on a glass substrate by pulsed-current heating

We report the very rapid growth of carbon nanotubes (CNTs) at high temperatures that can be tolerated by glass substrates. Glass substrates with metal microelectrodes and sputtered catalysts are heated by a pulsed current in a chemical vapour deposition gas environment for 0.5–1 s to synthesize CNTs of several micrometres in height without damaging the glass substrate. CNTs with structures from single-walled to multi-walled and morphologies from entangled networks to vertically aligned forests are grown simply by changing the nominal thickness of the catalyst, and such CNTs grown selectively on the microelectrodes worked as field emitters for cathodoluminescence. Rapid, easy growth of patterned CNT arrays on glass substrates without using furnaces/heaters or vacuum pumps will be useful for various applications of CNTs.     

Focused Deposition of Nanoparticles on Polymer Film with an Improved TSI-Nanoparticle Sampler (Model 3089)

A two-dimensional array of spots of deposited nanoparticles as small as 7 × 7 μm was fabricated on a polymer film using a modified commercial nanometer aerosol sampler (NAS; TSI-model 3089) coupled with a surface-discharge microplasma aerosol charger (SMAC). The charged aerosol particles were electrostatically focused by a metal mesh (electrically grounded) on the polymer film (insulator) and electrode (3 kV). The effect of mesh geometry on the concentration ratio (focusing ratio × collection efficiency) was evaluated using monodisperse polystyrene latex particles with diameters of 48, 100, and 300 nm. The electrostatic focusing effect was also analyzed by a numerical simulation of the electrostatic field. The two-dimensional patterning of nanoparticles is an effective method in concentrating particles for the subsequent observation and chemical analysis of aerosol particles. In our experiments, the SMAC-NAS system achieved a net concentration ratio of more than 20 times for 48- and 100-nm particles, which would significantly shorten the aerosol-sampling time. The particle deposition patterns formed on a transparent polymer film may provide samples for analyzing the transmittance, luminescence, and other optical characteristics of deposited nanoparticles.

Copyright 2015 American Association for Aerosol Research     

Vapor Pressure of Barium and Copper Components in YBa2Cu3O7−x Superconductor Ceramics

Purified air is passed over a specimen of YBa₂Cu₃O_{7– x} at 890°C; the vaporized substances are condensed in a pure alumina tube, then subjected to inductively controlled plasma analysis. Vapor pressure values of 2.5 × 10⁻⁵ Pa for BaO( g ), 1.2 × 10⁻⁴ Pa for Cu( g ), and 2.2 × 10⁻⁵ Pa for CuO( g ) are obtained under 2.1 × 10⁴ Pa (0.21 bar) of oxygen pressure. No Y vapor is detected at this temperature.     

Post-irradiation examination of uranium-doped rock-like oxide fuels

Post-irradiation examinations of rock-like oxide fuels were performed in JAERI to evaluate irradiation behavior and geochemical stability. Five kinds of fuels were prepared using 20% enriched U instead of Pu; a single-phase fuel of an yttria-stabilized zirconia containing UO₂ (U-YSZ), two particle-dispersed type fuels of U-YSZ particles + MgAl₂O₄/Al₂O₃ powder, two homogeneously blended type fuels of U-YSZ powder + MgAl₂O₄/Al₂O₃ powder. The fuels were irradiated in JRR-3 for about 100 days and estimated irradiation conditions were as follows; linear power was 15 kW m⁻¹, thermal neutron fluence was 7 x 10²⁴ m⁻² and fuel temperatures at the surface were 740–1130 K. From the results of non-destructive examinations, the stainless steel cladding surfaces were partially discolored by oxidation and no remarkable deformation of the pins was observed. Significant pellet fragmentation was not observed in spite of the crack formation as observed in irradiated LWR UO₂ fuels. Nonvolatile FPs were observed only in pellets but volatile Cs moved partly to the plenum. From these examinations, no significant difference in macroscopic irradiation behavior was distinguished among 5 fuels.     

Creep analysis of surface-cracked plates by a creep line-spring method

The creep line-spring method proposed in this paper is based on the solutions for the following two problems: a creep crack under non-steady creep condition; an elastic-plastic surface-cracked plate. For the problem of a non-steady creep crack, an engineering approach for estimating the load-line displacement, crack-tip J and C integrals is presented by extending the engineering approach for elastic-plastic fracture analysis to creep analysis. For solving the elastic-plastic surface crack, a simplified elastic-plastic line-spring method is applied. These two approximate solutions are checked by the finite element method. On the basis of the above two approximate methods, a creep line-spring method is proposed and the corresponding fundamental equations are established. The creep line-spring method is used to estimate creep fracture parameters for three-dimensional cracks. In order to check its accuracy, several surface-cracked plates under uniform tension are analyzed by the creep line-spring method and by the three-dimensional finite-element method. The numerical results show that the creep line-spring method is in good agreement with the finite-element method and has the same accuracy as the common elastic-plastic line-spring method.     

Line identification of boron and nitrogen emissions in extreme-and vacuumultraviolet wavelength ranges in the impurity powder dropping experiments of the Large Helical Device and its application to spectroscopic diagnostics

An impurity powder dropper was installed in the 21 st campaign of the Large Helical Device experiment(Oct. 2019–Feb. 2020) under a collaboration between the National Institute for Fusion Science and the Princeton Plasma Physics Laboratory for the purposes of real-time wall conditioning and edge plasma control. In order to assess the effective injection of the impurity powders,spectroscopic diagnostics were applied to observe line emission from the injected impurity. Thus,extreme-ultraviolet(EUV) and vacuum-ultraviolet(VUV) emission spectra were analyzed to summarize observable impurity lines with B and BN powder injection. Emission lines released from B and N ions were identified in the EUV wavelength range of 5–300 ? measured using two grazing incidence flat-field EUV spectrometers and in the VUV wavelength range of 300–2400 ? measured using three normal incidence 20 cm VUV spectrometers. BI–BV and NIII–NVII emission lines were identified in the discharges with the B and BN powder injection, respectively. Useful B and N emission lines which have large intensities and are isolated from other lines were successfully identified as follows: BI(1825.89, 1826.40) ?(blended), BII 1362.46 ?, BIII(677.00, 677.14,677.16) ?(blended), BIV 60.31 ?, BV 48.59 ?, NIII(989.79, 991.51, 991.58) ?(blended), NIV765.15 ?, NV(209.27, 209.31) ?(blended), NVI 1896.80 ?, and NVII 24.78 ?. Applications of the line identifications to the advanced spectroscopic diagnostics were demonstrated, such as the vertical profile measurements for the BV and NVII lines using a space-resolved EUV spectrometer and the ion temperature measurement for the BII line using a normal incidence 3 m VUV spectrometer.     

A simple oxidation–reduction process for the activation of a stainless steel surface to synthesize multi-walled carbon nanotubes and its application to phenol degradation in water

Aligned multi-walled carbon nanotubes (MWCNTs) were synthesized directly on a stainless steel surface by surface activation by intense oxidation in air followed by a moderate reduction in H₂ without any wet process. This method is extremely simple compared with conventional ways that need catalyst loading steps or acid pre-etching steps to synthesize carbon nanotubes on stainless steel surfaces. It was found that the length of MWCNT bundles could reach 80 μm when the oxidation step was properly controlled. It was demonstrated that MWCNTs synthesized on stainless steel meshes could be used as a catalyst support to enhance ozone oxidation in the decomposition of phenol in water.