SYNTHESIS, STRUCTURAL CHARACTERIZATION AND PHOTOCATALYTIC ACTIVITY OF TIO2 NANOPARTICLES

Titanium dioxide (TiO2) nanoparticles were synthesized via sol-gel process (soft chemistry), using the metal alkoxide as precursor.  TiO2 is a promising material especially when it is reduced to the nanometric scale, but many parameters influence its nanoscale synthesis. In this work, the influence of calcination time was studied. The structure, morphology and size of the synthesized particles were determined by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The XRD diffractograms revealed an anatase structure of the as prepared TiO2, with a nanometric size. The average particle size of TiO2, synthesized in ethanol as a solvent, is estimated to be 17 nm. An increase of calcination time induced an increase of the particle size to 21 nm, while keeping the anatase phase unchanged. FTIR measurements confirmed the pure anatase phase of TiO2 and the SEM micrographs displayed the aggregation of the nanoscale particles. The photocatalytic activity of synthesized nanoparticles was investigated by degradation of  methylene blue dye by TiO2 nanoparticles under ultraviolet radiation

Hydrates and polymorphs of lead squarate Pb(C4O4): Structural transformations studied by in situ X-ray powder diffraction and solid state NMR

International audienceConsidering the low dimensionality of the crystal structure of the known lead squarate tetrahydrate, Pb(C4O4)·4H2O, the thermal reactivity of the powdered compound and structural studies of lower hydrates have been investigated from X-ray single-crystal and powder diffraction data, solid state NMR and thermal analyses. It is shown that Pb(H2O)(C4O4) and two polymorphs of anhydrous PbC4O4 can be formed within different conditions. The departure of the water molecules leads to the condensation of initial inorganic chains into 2D or 3D-type crystal structures. The full decomposition of the squarate ligand provides successive lead oxides

Time frequency and array processing of non-stationary signals

The special issue of EURASIP Journal on Advances in Signal Processing 2012 focuses on the synergistic relationship between time-frequency methods and array signal processing methods and addresses recent developments. In the article 'Joint DOD/DOA estimation in MIMO radar exploiting time-frequency signal representations' Yimin Zhang and co-researchers deal with the joint estimation of direction-of-departure (DOD) and direction-of-arrival (DOA) information of maneuvering targets in a bistatic multiple-input multiple-output (MIMO) radar system when exploiting spatial time-frequency distribution (STFD). In the article 'Estimating the number of components of a multicomponent nonstationary signal using the short term time-frequency Rényi entropy,' Victor Sucic and co-researchers propose a solution to the problem of detecting the local number of signal components by resorting to the short-term Rényi entropy of signals in the time-frequency plane