2010

Si-SiC open cell foams with porosity >87% and high pore sizes (4-7 mm) are commonly employed as active zone in porous burners for heat radiation applications. In a porous burner, the solid porous body let the heat recirculate from the hot combustion products to the incoming reactants. The result is that the flame is confined within the foam, meaning high thermomechanical loadings on its constituent material. A set of commercial Si-SiC foams from the same production batch was aged with flat porous burners.

Massive carpets of well packed, vertically aligned and very long multiwall carbon nanotubes were synthesized by an efficient thermal Chemical Vapour Deposition process. Electrical properties of the material were evaluated, both in terms of "global" characteristics (bulk resistivity) and in terms of "local" properties (Scanning Tunnel Spectroscopy measurements) for as-grown and annealed at different temperatures samples. The behaviour of bulk resistivity as a function of temperature was evaluated in the range 3÷300 K, with a four-probe technique.

The oxidation resistances of different kinds of SiC-based laminates are compared. The materials under investigation are produced by tape casting of green ceramic sheets, followed by stacking of the sheets in a multilayer structure and laminate consolidation by de-binding and sintering. Three kinds of specimens are tested: multilayer SiC with fully dense layers, multilayer SiC integrating porous layers and multilayer composites made by stacking SiC/Cf composite layers. Two kinds of chopped carbon fibres (polyamide coated and uncoated) are used for the manufacture of the composite sheets.

Tape casting combined with layer stacking, debinding and sintering proved to be a suitable technique for processing SiC-based multilayers to be used as thermal protection system for space vehicles. In this paper two methods have been evaluated in order to decrease the thermal conductivity through the thickness of the material: the insertion of layers containing a pore forming agent able to leave residual porosity; the deposition of an external insulating coating made of yttria-partially stabilized zirconia (YPSZ). Both techniques contribute to the reduction of thermal conductivity.

Co-continuous metal/ceramic composites were obtained by the Reactive Metal Penetration (RMP) method. With the aim of components cost reduction, commercial cordierite preforms and standard aluminium infiltrating alloys (1050, 2011 and 7075) were used in the process. Kinetics of the infiltration reaction, microstructure and mechanical properties of the composites were found to be influenced by both quantity and type of alloying elements.

In this paper, the surfaces of PET/TiO2 thin film were modified by DC glow discharge plasma as a function of discharge potentials for improving the bioactivity. The hydrophilicity of the plasma-treated PET/TiO2 film was measured by contact angle measurement and the surface energy was estimated by using Fowkes method. The structural and chemical composition of the plasma-treated PET/TiO2 was analysed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS).

Blocks of vertically aligned multiwall carbon nanotubes were prepared by thermal chemical vapor deposition starting from camphor and ferrocene precursors. The blocks, having a thickness of approximately 2 mm and composed of nanotubes with diameter ranging between 30 and 80 nm, were submitted to compression tests. The results were analyzed accordingly with a simple model consisting in a parallel array of nanotubes under compression and bending suffering microscopic instability and compaction.