2011

An ultra-fine alumina powder was doped with yttrium or zirconium chloride to produce Al2O3–5 vol.%ZrO2 (AZ-5) and Al2O3–5 vol.%YAG (AY-5) composite powders. Composite samples and pure alumina, used as a reference, were submitted to dilatometric analyses up to 1500–1550 °C at 2, 5 and 10 °C/min for supplying the data required for the modeling of their sintering behaviour. The best fit for the three samples was obtained by applying an Avrami–Erofeev nucleation and growth model (An) and a subsequent power law reaction (AnFn).

This paper deals with the development of macro-porous components made of a carbonated hydroxyapatite (HAp) nanopowder which was extracted from pig bones. Prior to sintering, the powder was treated at 700 °C for 1 h. During calcination, a partial carbonate decomposition occurred yielding CaO. In order to eliminate this by-product, the calcined HAp was washed in distilled water several times, checking the effect of washings by FT-IR spectroscopy.

Three-phase composites in the system Al2O3–YAG–ZrO2 (AYZ) were produced by doping the surface of commercial alumina nanopowders with inorganic precursors of the second phases. Materials with three different compositions were prepared, in which 5, 20 and 33 vol.% of each second phase were respectively present. Pure crystalline phases were obtained in the final composites, as assessed by X-ray diffraction. Green bodies were produced by slip casting and uniaxial pressing.

Electrospun polyamide-6 membranes containing titanium dioxide (TiO2) photocatalyst were prepared and characterized. By tailoring the electrospinning parameters it was possible to obtain membranes having two different thicknesses, namely 5 and 20 µm, in which TiO2 particles were homogeneously dispersed. As a comparison, hybrid films made with polyamide-6 matrix and TiO2 filler were successfully produced, with inorganic/organic ratios of 10 and 20 wt%.

Barium titanate—acrylic hybrids with ceramic contents ranging between 10 and 70 wt% were successfully prepared by means of photopolymerization. These composites presented a homogeneous distribution of the ceramic particles within the organic matrix. In addition, an almost complete acrylic double-bond conversion took place. Basic electrical properties of the composites were investigated by dielectric spectroscopy.

Heat recovery from waste gas is a major key process for increasing efficiency of thermal processes. The aim of the present work is to increase heat transfer coefficients of ceramic heat exchangers of recuperative burners using highly structured surface elements created from a textile precursor. The paper describes the chosen geometries and their thermal behavior, the ceramization process and the preliminary design of the new recuperative burners.

Presently, one of the most interesting approaches to the generation of H2 is based on sulphur-based cycles, that however require structural components able to work in a corrosive environment at high temperature. Silicon carbide (SiC) is one of the most promising materials for this application, and to increase its limited toughness multilayered structures can be envisaged, since crack deviation and delamination increase energy adsorption during fracture.