CeraMat

An innovative gel-casting process was developed in order to obtain macro porous ceramics scaffolds of hydroxyapatite to be used in regenerative medicine for bone tissue reconstruction. Mechanical investigation was carried out on different formulations of dense hydroxyapatite samples in order to evaluate the effect of the gel casting process parameters on the density, the elastic modulus, the tensile and the compressive strength. The fracture critical stress intensity factor (KIC) was also evaluated by means of microhardness measurements.

Two different alumina powders were dispersed in low-density polyethylene (LDPE) to evaluate if any role can be ascribed to the crystalline phase, size and morphology of the alumina filler. In particular a submicrometric α-alumina and a nanocrystalline transition (γ/δ) alumina were added to the polymer at 5 wt% concentration, using a Brabender mixing unit. Both the neat inorganic fillers showed a good dispersibility in the polyolefin. The thermal and mechanical properties of the composites obtained were evaluated.

Biocompatible and biodegradable scaffolds can provide a convenient support for stem cell differentiation leading to tissue formation. Porous hydroxyapatite (HAp) scaffolds are clinically used for applications such as spinal fusions, bone tumors, fractures, and in the replacement of failed or loose joint prostheses. The incorporation of small amounts of silicon within hydroxyapatite lattice significantly improves HAp solubility and rate of bone apposition, as well as the proliferation of human osteoblasts in vitro.

Well-dispersed nano-crystalline transition alumina suspensions were mixed with yttrium chloride aqueous solutions, with the aim of producing Al2O3–Y3Al5O12 (YAG) composite powders. DTA analysis allowed to highlight the role of yttrium on the α-phase crystallization path. Systematic XRD and HRTEM analyses were carried out in parallel on powders calcined in a wide temperature range (600–1300 °C) in order to follow phase and microstructural evolution.

A fine-grained (330 nm) yttrium aluminium garnet (YAG) ceramic, presenting a non-negligible transparency (66% RIT at 600 nm), was obtained by spark plasma sintering. The YAG powder was manufactured by co-precipitation, starting from a yttrium and aluminium chlorides solution. A soft precursor was obtained, whose phase evolution was studied by X-ray diffraction. Calcined powders were dispersed by either ball milling or by ultrasonication and then subjected to spark plasma sintering at several temperatures (1200–1400 °C) and for a reduced time (15 min).

Calcium phosphate-based materials should show excellent bone-bonding and cell-mediated resorption characteristics at the same time, in order to be employed for bone replacement. In this perspective, pure (HAp) and silicon-substituted hydroxyapatite (Si-HAp, 1.4% wt) porous cylinders were prepared starting from synthesized powders and polyethylene spheres used as porogens, and investigated as supports for osteoblast and osteoclast progenitor differentiation.

Al2O3–5 vol.% Y3Al5O12 (YAG) composite powders have been prepared by surface doping of α-alumina powders by an yttrium chloride aqueous solution. Two commercial, one submicron-sized, the other ultra-fine, alumina powders were compared as matrix materials. YAG phase was yielded by an in situ reaction promoted by the subsequent thermal treatment of the doped powders.

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.