Carbon Fibers / Hydroxyapatite Bone Implant Composites

Hydroxyapatite(HA)/Carbon fibers composite is one kind of the excellent hard tissue implants. However, the significant difference in heat expansion coefficient and surface chemical properties between hydroxyapatite and C-fibers leads to the poor bonding strength of the C-fiber/HA interface, and to the appearance of cracks, which results in the low reliability of the mechanical properties of the composite. These reasons limited the application of the composite in the bearing position in human body. The technology of surface treatment and coating calcium phosphate layer on C-fibers have been used in this paper in order to fabricate more mechanically reliable C-fiber reinforced HA composite.The electrodeposition on the untreated and nitric acid treated carbon fibers was studied. Result shows that CaHPO4 2H2O(DCPD) was obtained as the kind of calcium phosphate coating on two kinds carbon fibers, but their construction and morphology are different. It also shows that the time of oxidization has significant influence on eletrodeposition kinetics. In this paper, carbon fibers treated by para-aminobenzoic acid were used for forming a bioactive coating on the surface of carbon fibers. Result shows that C-fibers were coated by a thick layer of nano HA particles, with the morphology of spheric or hemispheric shape.The chemical constitution, micromorphology and bending strength of the composites have also been discussed in the paper. And the result shows that electrodeposition layer on carbon fibers is unfavorable to the HA/C-fiber composite by inducing the decomposition of HA. The untreated C-fibers/HA composite has a fatal disadvantage in incomplete sintering. It has a weak bond between the carbon fibers treated by nitric acid and matrix, and it has a lot of cracks around the C-fibers due to the difference in heat expansion coefficient. On the contrast, it has a strong bonding strength between the biomieralized carbon fibers and matrix. The better bending strength can be obtained from the biomieralized C-fiber/HA composite than that of other C-fiber reinforced.