Correlation of the ratio of metallic to oxide species with activity of PdPt catalysts for methane oxidation

Bimetallic catalysts consisting of Pd and Pt on TiO2-zeolite (mordenite, beta, ZSM-5) supports were prepared and tested for the combustion of methane. The activity of the catalysts was found to be dependent on the zeolite topology and SiO2 : Al2O3 ratio and was linearly dependent on the proportion of Pd and Pt present in a bimetallic phase observed in XRD diffractograms of the catalysts. This linear dependence was valid for a range of zeolites used. STEM-EDS and electron tomography showed the Pd and Pt to be largely co-located and XAS and XPS indicated that the metals are mostly present in the form of oxide nanoparticles with a minor contribution from the metals at high SiO2 : Al2O3 ratios. Catalyst characterization showed there to be little difference overall in the metal loading and physical characteristics of the samples and NH3-TPD suggested that the activation of methane over acid sites is not important. Adding water to the feed, slightly reduced the conversion but did not affect the deactivation profile of the catalysts tested

Dense GaN nanocolumn arrays by hybrid top-down-regrow approach using nanosphere lithography

A comprehensive description of a procedure to form dense locally ordered 2D arrays of vertically aligned hexagonal in section GaN nanocolumns (NCs) without height deviations will be presented. Particular focus will be given for the preparation of silica nanosphere hard masks, dry etching to form GaN NCs, wet etching to modify NC shape, thermal annealing and regrowth to recover non-polar m-plane facets, improve NC crystal quality and array fill factor

Correlation of the ratio of metallic to oxide species with activity of PdPt catalysts for methane oxidation

Bimetallic catalysts consisting of Pd and Pt on TiO2-zeolite (mordenite, beta, ZSM-5) supports were prepared and tested for the combustion of methane. The activity of the catalysts was found to be dependent on the zeolite topology and SiO2 : Al2O3 ratio and was linearly dependent on the proportion of Pd and Pt present in a bimetallic phase observed in XRD diffractograms of the catalysts. This linear dependence was valid for a range of zeolites used. STEM-EDS and electron tomography showed the Pd and Pt to be largely co-located and XAS and XPS indicated that the metals are mostly present in the form of oxide nanoparticles with a minor contribution from the metals at high SiO2 : Al2O3 ratios. Catalyst characterization showed there to be little difference overall in the metal loading and physical characteristics of the samples and NH3-TPD suggested that the activation of methane over acid sites is not important. Adding water to the feed, slightly reduced the conversion but did not affect the deactivation profile of the catalysts tested

SKraken: Fast and Sensitive Classification of Short Metagenomic Reads based on Filtering Uninformative k-mers

We describe extensive studies on a family of perovskite oxides that are ferroelectric and ferromagnetic at ambient temperatures. The data include x-ray diffraction, Raman spectroscopy, measurements of ferroelectric and magnetic hysteresis, dielectric constants, Curie temperatures, electron microscopy (both scanning electron microscope and transmission electron microscopy (TEM)) studies, and both longitudinal and transverse magnetoelectric constants alpha(33) and alpha(31). The study extends earlier work to lower Fe, Ta, and Nb concentrations at the B-site ( from 15%-20% down to 5%). The magnetoelectric constants increase supralinearly with Fe concentrations, supporting the earlier conclusions of a key role for Fe spin clustering. The room-temperature orthorhombic C-2v point group symmetry inferred from earlier x-ray diffraction studies is confirmed via TEM, and the primitive unit cell size is found to be the basic perovskite Z = 1 structure of BaTiO3, also the sequence of phase transitions with increasing temperature from rhombohedral to orthorhombic to tetragonal to cubic mimics barium titanate. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4790317]</p