Carbon Nanotubes / Hydroxyapatite Biocomposite The Gelcasting Research,

Hydroxyapatite (HA) is a bioactive material that has recently received much attention mainly because of its excellent bioactive properties. HA with relatively low strength and high brittleness can hardly meet the high need of the mechanical properties for certain parts of human bodies. CNTs is a new carbon structure which was found in 1991. It has close nano-tube structure that is made up of monolayer or multiplayer graphite piece. This special structure makes it exhibit excellent mechanical properties. We have fabricated one kind of CNTs/ HA composite whose bending strength and fracture toughness reach 140MPa and 2.4MPa·m^1/2. The biocompatibility of the composite was researched by histography observation and molecular biology. We found that the composite possessed good biocompatibility and could accelerate the wound cicatrisation.But conventional ceramic process cannot satisfy it's forming questions for the various shapes. Gel-casting is a new ceramic forming technique getting worldwide attention, which iss suitable for the fabrication of complex parts with no density differences. It is important to research the gel-casting process of CNTs/ HA composite for its clinical use.Nanograde hydroxyapatite with chemical co-precipitation method was prepared. The effects of pH, dispersant, content of solid in slurry and the dispersing process on the slurry and the properties of the green bodies were researched. The cross-experimental research of gel-casting on HAP was conducted. It showed that there existed the optimum amount of monomer, binder and initiator. DTA shows CNTs has been oxidated from 450℃, so we designed two binder' burnout methods: one step's and two steps' method. The former was burnout in air and heat preservation at 450℃; the other was burnout in vacuum at 600℃ and treatment at 350℃ .The samples were sintered at 1100℃ for 4 hours in vacuum and then the composites were obtained.The mechanical properties of the composite were studied, which is much higher than that fabricated by two steps' method. The result also shows that the bending strength increases with the increase of CNTs content. XRD shows the leaving carbon is burnt out by heat treatment and the binder cannot be burnt out thoroughly by one step's method. The CNTs/ HA composite can be fabricated by two steps' and its follow-up sinter process. The fracture microstructure of the composite fabricated by...