Biocompatible artificial cellular ceramics can be used as scaffolds for tissue engineering in substitution of natural bone, in force of a better reproducibility of the microstructure, potentially higher mechanical performance and ease of forming components of the desired geometry. An innovative gel-casting procedure was selected for the production of both dense and highly porous (about 60%) structures made of pure hydroxyapatite (Ca10(PO4)6(OH)2, HA). Suspensions of commercially available HA powders (solid loading of 60 - 68 wt.%), were mixed with solutions of 2 wt % agar, selected as gelling agent. The slurries were cast into PMMA molds under vacuum, and gelation occurred during slow cooling down to room temperature. The gelled specimens were de-molded and dried in controlled relative humidity conditions. For the production of porous components, commercial polyethylene spheres (355 - 420 µm diameter) were used as pore-forming agents and added to the suspensions before casting. After drying, samples were submitted to a controlled thermal treatment for the decomposition of the organic compounds and the densification of the ceramic skeleton. Sintering was performed at 1280°C for 3 h. A complete mechanical characterization was carried out both on dense and porous samples. Uniaxial compression, four point bending and indentation tests were performed in order to determine Young’s modulus, ultimate tensile stress, compressive strength and fracture toughness (KIC). Microstructural characterization evidenced the presence of spherical macro-pores, yielded by PE decomposition, and a diffused micro-porosity on the HA walls, caused by incomplete densification during sintering. A digital image based finite element analysis (DIB-FEA) procedure was applied to gel-cast cellular ceramics. Such an approach allows to build up a FE model that includes all the relevant microstructural features of a material (distribution of pores, presence of isolated defects, micro-cracks…) starting directly from real micrographs of its cross-sections. A simulation of the mechanical behavior or real components can thus be carried out on the designed model. A good agreement was evidenced between experimentally derived and calculated values of elastic modulus, thus validating the simulation procedure and opening the way to the possibility of predicting the mechanical behavior of cellular components characterized by different amounts of macro-porosity.
Mechanical characterization of hydroxyapatite micro/macro-porous scaffolds by an innovative gel-casting process / Bartuli, Cecilia; Tirillo', Jacopo; L., Montanaro; P., Palmero; M., Cabrini; P., Marcassoli. - STAMPA. - (2009). (Intervento presentato al convegno VII Convegno Nazionale sulla Scienza e Tecnologia dei Materiali tenutosi a Tirrenia nel 9-12 Giugno 2009).
Mechanical characterization of hydroxyapatite micro/macro-porous scaffolds by an innovative gel-casting process
BARTULI, Cecilia;TIRILLO', Jacopo;
2009
Abstract
Biocompatible artificial cellular ceramics can be used as scaffolds for tissue engineering in substitution of natural bone, in force of a better reproducibility of the microstructure, potentially higher mechanical performance and ease of forming components of the desired geometry. An innovative gel-casting procedure was selected for the production of both dense and highly porous (about 60%) structures made of pure hydroxyapatite (Ca10(PO4)6(OH)2, HA). Suspensions of commercially available HA powders (solid loading of 60 - 68 wt.%), were mixed with solutions of 2 wt % agar, selected as gelling agent. The slurries were cast into PMMA molds under vacuum, and gelation occurred during slow cooling down to room temperature. The gelled specimens were de-molded and dried in controlled relative humidity conditions. For the production of porous components, commercial polyethylene spheres (355 - 420 µm diameter) were used as pore-forming agents and added to the suspensions before casting. After drying, samples were submitted to a controlled thermal treatment for the decomposition of the organic compounds and the densification of the ceramic skeleton. Sintering was performed at 1280°C for 3 h. A complete mechanical characterization was carried out both on dense and porous samples. Uniaxial compression, four point bending and indentation tests were performed in order to determine Young’s modulus, ultimate tensile stress, compressive strength and fracture toughness (KIC). Microstructural characterization evidenced the presence of spherical macro-pores, yielded by PE decomposition, and a diffused micro-porosity on the HA walls, caused by incomplete densification during sintering. A digital image based finite element analysis (DIB-FEA) procedure was applied to gel-cast cellular ceramics. Such an approach allows to build up a FE model that includes all the relevant microstructural features of a material (distribution of pores, presence of isolated defects, micro-cracks…) starting directly from real micrographs of its cross-sections. A simulation of the mechanical behavior or real components can thus be carried out on the designed model. A good agreement was evidenced between experimentally derived and calculated values of elastic modulus, thus validating the simulation procedure and opening the way to the possibility of predicting the mechanical behavior of cellular components characterized by different amounts of macro-porosity.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
