Nanoporous WO3 from anodized RF sputtered tungsten thin films

We report the first electrochemical anodization of RF (radio-frequency) sputtered tungsten (W) thin films. High pressure sputtering was utilized to produce W films of low intrinsic stress with a high degree of adhesion to the transparent substrates. Structurally and uniformly porous tungsten trioxide (WO₃) films were obtained under optimised anodization conditions in fluoride ion-containing electrolyte. Crystalline WO₃ was obtained after annealing the films at 450 °C. SEM and XRD characterisation techniques were used to determine the surface morphology and crystal structure of the non-anodized and anodized films.     

AC space-charge effects in gyroklystron amplifiers

The effects of AC space charge on multicavity gyroklystron amplifiers are studied. It is found that when AC space charge is included in the analysis of weakly relativistic multicavity gyroklystron amplifiers, the optimized nonlinear efficiency becomes a function of beam current. For a cold beam (no velocity spread), the efficiency is maximum at zero current and decreases monotonically as the current increases. The zero current limit of the optimized efficiency when AC space-charge effects are included is not the same as the optimized efficiency with no space charge; it is significantly higher. This behavior is regularized when velocity spread is taken into account; in that case, the nonlinear efficiency increases with beam current until it reaches a maximum, then falls off slowly. The increase in efficiency is attributed to enhanced bunching associated with the saturation of the space-charge instability in the drift region; the reduction in efficiency at high current occurs because space charge induces an additional velocity spread in the beam     

A comparison of the intramolecular and intermolecular hydrogen bonding of N,N′-ethylenebis(aminobenzylidene) in the solid state with its salen analogue

The crystal structure of H₂amben has been elucidated for the first time. The close NH?N contact between neighbouring molecules supports strongly the notion that intermolecular hydrogen bonding exists within the crystal lattice, creating a series of molecular chains, which are crosslinked in a three-dimensional array. This intermolecular bonding is suggested to account for the anomalously high melting point of H₂amben (176-178 °C) compared to its H₂salen counterpart (126-128 °C). Although strong intramolecular forces are present in both ligands, H₂salen contains no intermolecular hydrogen bonds.     

The structures and properties of tetrafluoromethane, hexafluoroethane, and octafluoropropane using the AIMPRO density functional program

The AIMPRO density functional program was used to calculate the structures and properties of the three simplest perfluoroalkanes: tetrafluoromethane, hexafluoroethane, and octafluoropropane. The method reproduces both the molecular structures and the vibrational spectra well, and in addition, has identified a new C₂-symmetry ortho-conformer of octafluoropropane that is approximately 0.525 kcal/mol (2.20 kJ/mol) higher in energy than the well-known C_2v-symmetry global minimum staggered-conformer.