Three silicon oxycarbide glasses (SiCO) with increasing C content were obtained through pyrolysis in inert atmosphere at 1000 °C of sol-gel derived siloxane networks containing Si-CH 3 and Si-H bonds. The glasses were further annealed at 1200, 1400, and 1500 °C to follow their evolution at high temperature. Quantitative information concerning the structure of glasses before and after annealing at high temperature was collected with a wide range of techniques (some of them used for the first time in this field) with the aim of probing the following: (i) the short-range order and chemical composition ( 29 Si and 1 H MAS NMR, RDF derived from X-ray and neutron scattering, inelastic neutron scattering, FT-IR, and elemental analysis), and (ii) the long-range order (X-ray and neutron diffraction) and microstructural features (HR-TEM combined with electron diffraction, Raman, porosity, and surface area measurements). This extensive collection of data, carried out on the same set of specimens, provided detailed and sound structural information on nearly-stoichiometric SiCO glasses and their high-temperature behavior.

A convolutive profile-fitting procedure is described for analysing X-ray diffraction peak profiles broadened by microstructural factors (crystallite size and lattice disorder). The method requires, in a first stage, an accurate determination of the instrumental function, which is subsequently convoluted with a parametric function adjusted to fit the diffraction profile intensities of the specimen investigated. In the calibration of the instrument function throughout the angular range 20-145 ° in 20, 58 peaks of a well crystallized a-quartz specimen are examined. Provision is made to include in the instrument function an exponential function containing an angle-dependent asymmetry parameter. In the present methodology, a pseudo-Voigt function is suggested to obtain the shape factors (integral breadth, peak width at half maximum, Gaussian content) that contain useful information related to the microstructural properties in the frame of the so-called

The light-induced phase transition of TiO2\ud nanoparticles from anatase to rutile structure is reported\ud depending on the surrounding environment, the transition\ud being accomplished under oxygen-poor conditions. The\ud transition mechanism is interpreted in the framework of oxygen\ud adsorption and desorption phenomena with the involvement of\ud surface oxygen vacancies and F centers. It is shown that the\ud observed phase transition is not thermally driven because the\ud local temperature of the nanoparticles during irradiation is\ud about 370 K (estimated through the Stokes to anti-Stokes\ud Raman peaks ratio). On the contrary, the phase transition is\ud initiated by intragap irradiation (with the exception of the red\ud light one) that acts as TiO2 surface sensitizer, promoting the\ud activation of the surface and the nucleation of rutile crystallites starting from two activated anatase neighboring nanoparticles

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