Hydroxyapatite-316L fibre composites prepared by vibration assisted slip casting

To prepare hydroxyapatite (HA, or HAp)-stainless steel 316L fibre composite s with up to 30 vol% 316L fibres (similar to1 mm long and 50 mum in diamete r), slip casting assisted by vibration (frequency: similar to 55 Hz; amplit ude: similar to5 mm) was carried out, followed by both cold isostatic press ing (CIPing) and hot isostatic pressing (HIPing). With the addition of arou nd 0.5 wt% sodium carboxymethylcellulose (Na-cmc), solids loadings up to 44 vol% were obtained in calcined HA powder-derived slips, which were castabl e only under the vibration. The slips were concentrated and viscous so that the preferential sedimentation of the dense and large 316L fibres could be avoided. Subsequent CIPing was able to increase the relative density of th e cast and dried green compacts from 46% after casting to 60% after CIPing. With the dense and uniform green compacts of the HA-316L mixtures, final H IPing at 950 degreesC resulted in HA-316L fibre composites of 99% relative density. The HA-316L fibre composites had improved fracture toughness of 3. 6 +/- 0.3 MPa.m(0.5), due to the bridging effect of the ductile 316L fibres . However, the mechanical strength of the composites was limited by the pre sence of residual thermal stresses and circumferential microcracks. The HA- 316L fibre composites were biocompatible and exhibited favourable bone-bond ing characteristics. (C) 2001 Kluwer Academic Publishers.