Electrochemical methane conversion over SrFeO3−δ perovskite on an yttrium stabilized zirconia membrane

Oxidative methane coupling and the related chemical reactions have been studied in an electrochemical membrane cell of the type: CH₄, (O₂), SrFeO_3– , Au¦8%Y₂O₃:ZrO₂¦Ag, air. The results are compared to a fixed bed study of SrFeO_3– . The C₂₊ selectivity and the alkene/alkane ratio may be higher in the cell reactor than in the fixed bed reactor, but the C₂₊ yield never exceeded fixed bed data. The maximum C₂₊ yield observed in the cell reactor was 3.1%. The electric fields in the cell when electrodes were connected influenced the selectivity to CO₂ in a manner which may be related to the NEMCA effect.     

Computational study of flow in a curved pipe with circular cross section

Laminar imcompressible flows in a circular sectioned pipe were investigated by seeking numerical solutions to the Navier-Stokes equations. Three semi-circular pipes of radius ratios 0.05, 0.143 and 0.148 were studied. These calculations covered the Dean number ranging from 183 to 3847. In the range of low and medium Dean numbers, a steady-state solution was obtained; when the Dean number was high, a three-dimensional separation and the associated secondary flow were clearly observed far downstream near the outlet. Extensive flow visualizations were made to depict the computed results.     

Fracture behavior of carbon steel pipe with local wall thinning subjected to bending load

To evaluate the structural integrity of power plant piping, monotonic bending tests are conducted on 4- and 3.5-in. diameter full-scale carbon steel pipe specimens with local wall thinning. The local wall thinning is simulated as erosion/corrosion metal loss. The eroded area of the wall thinning is subjected to tensile or compressive stress by applied bending moment. The deformations or fracture behaviors at maximum moments are found to be classified into three types. When the eroded area is subjected to tensile stress, ovalization or crack initiation/growth occurs at the maximum moment. When an eroded area is subjected to compressive stress, ovalization or local buckling occurs. The occurrence of ovalization, crack initiation/growth, or local buckling depends on the initial size of local wall thinning. From the relationships among ovalization, crack growth and local buckling, allowable sizes for local wall thinning are proposed.     

Chaotic characteristics of local voidage fluctuation in a circulating fluidized bed

Local voidage fluctuations have been measured by using an optical transmittance probe at various axial and radial positions in a circulating fluidized bed riser with a 0.1 m i. d. and 10 m height. The chaotic time series analysis of the local voidage fluctuations has been adopted to characterize the nonlinear dynamics of the circulating fluidized bed riser. The variations of the correlation dimension and the Kolmogorov entropy of the voidage fluctuation were found to depend on the local time-average voidage. The axial and radial distributions of the correlation dimension and the Kolmogorov entropy were strongly affected by the solids flow structures (e.g. core-annulus flow) in various operating conditions. The correlation dimension of local voidage fluctuations increases along the riser, except the position near the distributor. Both, the correlation dimension and the Kolmogorov entropy of local voidage fluctuations near the wall, were found to be smaller than those at the center of the riser, independent of the solids circulation rate and the axial position.     

Shear viscosity of nylon 6 melts reinforced with microfibrous calcium silicate hydrate

Steady shear viscosity of nylon 6 melts reinforced with xonotlite, microfibrous calcium silicate hydrate (6CaO · 6SiO₂ · H₂O), is investigated. The highly filled nylon 6 melt tends to exhibit a yield value, resulting in remarkable viscosity increase particularly at low shear rates. Addition of the xonotlite significantly increases activation energy of viscous flow of the nylon 6 melt, leading the viscosity to be strongly temperature dependent. Comparisons with the melts filled with glass fibers and wollastonite are made. Flow-induced orientation becomes more important at low volume fractions. Shortening of the xonotlite during shear flow measurement can also be observed.     

Growth of large-diameter (∼4 nm) single-wall carbon nanotubes in the nanospace of mesoporous material SBA-15

Single-wall carbon nanotubes (SWCNTs) have been synthesized by supported-catalyst chemical vapor deposition (CCVD) using one-dimensional (1D) channels of mesoporous silica (SBA-15; mean channel diameter, 6.0 nm) functionalized with carboxyl groups where Co and Fe complexes are encapsulated. The synthesized SWCNTs have much larger diameters than the SWCNTs synthesized by conventional CCVD. Transmission electron microscope observations reveal that large-diameter SWCNTs (<4.2 nm) are grown in 1D channels of SBA-15. Large metal particles formed in the channels should play an important role in the growth of the SWCNTs with larger diameters.     

Behavior of deoxophostones family as nucleophilic monomers in no-catalyst copolymerization

Summary Deoxophostone family(2-phenyl-1,2-oxaphospholane1a, 2-phenyl-1,2-oxaphosphorlane1b, and 2-phenyl-1,2-thiaphospholane1c) copolymerized with acrylic acid without catalyst to produce the corresponding copolymers. The polymerization proceeded via a cyclic acyloxyphosphorane to produce poly-(phosphine oxide — ester)3a(or3b) from1a(or1b) and poly(phosphine oxide — thiolester)3c from1c, respectively, with acrylic acid. It is of interest that the copolymer from1c with acrylic acid was not poly(phosphine sulfide — ester)4 but3c. The reactions of1a or1b with pyruvic acid or 1,3-propane sultone were also investigated.The present authors dedicate this paper to the late Mr. Ken Mizuno.     

Fluorinated poly(aryl thioether)s and poly(aryl sulfone)s derived from 2,3,4,5,6‐pentafluorobenzoic acid

Poly(aryl thioether)s (F‐PTEs) containing 2,3,5,6‐tetrafluoro‐1,4‐phenylene moiety and polar moiety, such as 1,3,4‐ozadiazole, ether ketone, and amide groups, were synthesized by nucleophilic aromatic substitution reaction of aryl fluorides and 4,4′‐thiobisbenzenthiol. F‐PTEs were amorphous with good thermal properties including high glass transition temperature (T_g) and thermal stability, solubility, and hydrophobicity. F‐PTEs were transformed into poly(aryl sulfone)s (F‐PSs) by the oxidation reaction with hydrogen peroxide in acetic acid. Because of the sulfone group, the T_gs of the F‐PSs were 30–40°C higher than those of the corresponding F‐PTEs. F‐PSs maintained solubility in polar aprotic solvents and exhibited hydrophobicity in spite of the content of polar sulfone groups due to the highly substituted fluorine atoms. These F‐PTEs and F‐PSs were a new class of high‐performance polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and luminescent properties of Eu-doped transparent mica glass–ceramics

Eu-doped transparent mica glass–ceramics were prepared, the influence of Eu-doping on the crystallization of the parent glasses was investigated and the luminescent properties of the parent glasses and the glass–ceramics were estimated. A small additive amount of Eu element was very effective in preparing transparent mica glass–ceramics. However, the excess addition led to the coarsening of phase separation in the glass phase and the separation of unidentified crystal phases and β-eucryptite during heating of the parent glasses, which caused white opaque at lower heating temperatures. When mica crystals were separated, Eu ions entered the interlayers of mica crystals. The observed emission and excitation spectra showed that parts of Eu³⁺ ions which were added as Eu₂O₃ were reduced to Eu²⁺ ions during melting of the starting materials and heating the parent glasses in air and the energy transfer from Eu²⁺ to Eu³⁺ ions occurred.