Properties of titanium oxide biomaterials synthesized by titanium plasma immersion ion implantation and reactive ion oxidation

As an artificial heart valve material, titanium oxide is superior to low te mperature isotropic pyrolytic carbon in terms of mechanical properties and biocompatibility. The irregular shape of a heart valve makes conventional f abrication techniques like beam-line ion implantation and ion beam enhanced deposition (IBED) difficult. Plasma immersion ion implantation (PIII) does not suffer from the line-of-sight limitation and is an excellent technique for this purpose. In this work, titanium oxide thin films are synthesized on Ti6A14V by titanium metal PIII and oxygen PIII. By controlling the depos ition/implantation rate of titanium and oxygen plasma density, TiOchi films with different compositions and properties can be fabricated. The film pro perties are evaluated by techniques including atom force microscopy (AFM), X-ray diffraction (XRD), and various mechanical testing methods. AFM result s reveal that the TiOchi film surface is quite dense without gross voids. T he microhardness is enhanced with increasing oxygen partial pressure betwee n the range of 0-3 x 10(-2) Pa and reaches a maximum value of 17 GPa at an oxygen partial pressure of 3 x 10(-2) Pa. The wear resistance is also much better than that of Ti6A14V. In spite of our encouraging results, the TiOch i films synthesized in our experiments are still too thin. In order to expl oit its full potential as an artificial heart valve material, the films mus t be thicker. It can be achieved by using a more efficient metal are source or by increasing the PIII duty cycle. (C) 2000 Elsevier Science B.V. All r ights reserved.