Highly porous uranyl selenate nanotubules

A first amine-templated uranyl selenate based upon highly porous uranyl selenate nanotubules, (C4H12N)14[(UO2)10(SeO4)17(H2O)], has been prepared in the room-temperature reaction of uranyl nitrate, butylamine, and H2SeO4 in aqueous solution. The structure consists of nanometer-scale tubular [(UO2)10(SeO4)17(H2O)]14- units packed in a hexagonal-type fashion. The tubules have elliptical cross section with outer dimensions of 25 x 23 A = 2.5 x 2.3 nm. The internal free crystallographic diameter of the tubules is 12.6 A = 1.26 nm, which is comparable to the effective pore size in large-pore zeolites. This finding demonstrates the possibility of nanostructures for actinides in higher oxidation states and opens up a new area of research and exploration.     

Scaling of the energy gap withT c in Bi2Sr2CaCu2O8+δ

The results of a high-resolution photoemission study using synchrotron radiation of two single crystals of Bi₂Sr₂CaCu₂O₈₊, with different critical temperaturesT _c due to a variation in oxygen stoichiometry are reported. Within experimental accuracy, the energy gap 2 is found to scale withT _c , amounting to a reduced gap parameter of 2/k _BT_c7.4. Employing resonant photoemission at the O–2s and Cu–3p thresholds, two spectral peaks at binding energies of 180 meV and 320 meV were identified as predominantly O–2p-and Cu–3d 4s-derived states, respectively.     

Plasma Polymerization Inside Tubes in Hexamethyldisiloxanes and Ethyne Glow Discharges: Effects of Deposition Atmosphere on Wetting and Ageing in Solvents

The coating deposition inside tubes becomes increasingly important for fluidic applications, in which inner surfaces are chemically and mechanically strained by the flowing liquid and by scratching of particles. The developed process for tube coating, presented in this work, is based on the discharge in the precursor gas atmosphere between two mesh electrodes at the ends of the tube. The gas mixture is introduced on one end and pumped through the electrode on the other end. Igniting plasma inside the tube, the tube walls are the barrier to the atmosphere. Especially pulsed DC discharges for plasma polymerization in this alignment lead to good coating results, which is shown in this work focusing on deposition in pure and mixed hexamethyldisiloxane, ethyne, and oxygen atmospheres. Chemical binding, wetting, and ageing are strongly influenced by the choice of the gas mixtures. Sufficient oxygen partial pressure in the deposition atmosphere leads to hydrophilic behavior of the SiO₂-like polymer-like carbon coatings, all other applied atmospheres to generally hydrophobic behavior of pure and Si-doped plasma polymers, respectively.