2013

In the present work, the fabrication and characterization of non-curling, free-standing TiO2 nanotube membranes and their integration in front-side illuminated dye-sensitized solar cells are reported. Vertically oriented TiO2 nanotube arrays were fabricated by anodic oxidation of a titanium foil. Nanotube membranes were detached from the metallic foil, transferred and bonded on transparent fluorine-doped tin oxide/glass substrates employing a TiO2 sol as a binder.

Vertically oriented arrays of TiO2 nanotubes (NTs) are fabricated by fast and facile, thus easily up-scalable, anodic oxidation of a titanium foil followed by rapid thermal annealing. The structural/morphological characterization shows the formation of well defined one-dimensional nanotube carpets, while the X-ray diffraction analysis reveals the pure anatase crystalline structure of the thermal treated samples.

The fabrication and characterization of TiO2 nanotube (NT) arrays and their integration in front-side illuminated Dye-sensitized Solar Cells (DSCs) are reported. Vertically oriented TiO2 NTs were obtained by anodic oxidation of titanium foil and not-curling free-standing NT membranes were easily separated from the metal without the formation of cracks. Stoichiometry, crystalline phase and morphology of the films were investigated, evidencing the formation of a highly ordered 1D NT array, with a pure anatase crystalline structure.

YAG powder was synthesised by reverse-strike co-precipitation, calcined at 1000 °C and dispersed by either ball-milling with α-alumina (BMA) or zirconia (BMz) spheres or by ultrasonication (US). All the dispersed powders were consolidated by SPS to nearly theoretical density, but only the US powder gave rise to a transparent material (transmittance of about 60% at 600 nm, 1 mm thickness), characterised by an ultra-fine microstructure (average size of 330 nm).

Spray drying is widely used for producing granulated feed materials for compaction process, which is the current industrial method for manufacturing alumina-zirconia femoral heads. The optimization of the granules compaction behavior requires the control of the slurry rheology. Moreover, for a dual-phase ceramic suspension, the even phase distribution has to be kept through the atomization step. Here we present two approaches addressing the key issues involved in the atomization of a composite system.

Zirconia toughened alumina (ZTA) nanocomposites are attractive structural materials which combine the high hardness and Young's modulus of the alumina matrix with an additional toughening effect by the zirconia dispersion. In this study two approaches to prepare ZTA are compared. For the first approach, an ultrafine alumina powder was coated with 5 vol% zirconia by a wet chemical method. For the second one, the reference material was prepared by intensively mixing and milling the same alumina with nanoscale zirconia powder.

Well-dispersed nano-crystalline transition alumina suspensions were mixed with yttrium chloride aqueous solutions, with the aim of producing by spray-drying Al2O3–Y3Al5O12 (YAG) composite powders of increasing YAG vol.%. Two samples were prepared, with different Y content, corresponding to 5 and 20 YAG vol.%, respectively. Both samples were then treated at either 600 or 1150 °C.

Alumina-zirconia (AZ) composites are attractive structural materials, which combine the high hardness and Young’s modulus of the alumina matrix with additional toughening effects, due to the zirconia dispersion. In this study, AZ composites containing different amounts of zirconia (in the range 5–20 vol %) were prepared by a wet chemical method, consisting on the surface coating of alumina powders by mixing them with zirconium salt aqueous solutions. After spray-drying, powders were calcined at 600 °C for 1 h.

Varallo Sacred Mountain was realized at the end of the fifteenth century on initiative of the Franciscan Father Bernardino Caimi as a place of prayer, meditation and evocation of the Christian faith and has been included in the UNESCO World Heritage List since 2003. Some of its buildings show at the moment manifold maintenance, conservation and restoration problems. Therefore, in the frame of a detailed program of interventions, a research cooperation has been launched, aiming at singling out the existent materials and, as much as possible, their working techniques.

The free sintering of ceramic powders into fully dense nanostructured materials is still a challenging process, even more complex when nanostructured transition alumina is used as starting powder. In this paper, biphasic (Alumina–YAG) and triphasic (Alumina–YAG–ZrO2) composite powders were produced by doping the same nanocrystalline transition alumina with inorganic precursors of the second-phases, which were subsequently yielded under controlled thermal treatments.