Structure and mechanical properties of passivating titanium oxide films fabricated by DC plasma oxidation

Abstract

Summary form only given. Titanium and titanium alloys have high corrosion resistance and are common in the aerospace, chemical, and electrochemical industries. The materials have also found applications in medical and dental products such as artificial heart valves, artificial knee and hip joints also due to their good biocompatibility. It has been observed that the biocompatibility of titanium and titanium alloys is closely related to the surface oxide layer. The thickness of this native passivating surface oxide layer is usually very thin and a thicker layer must be synthesized in order to enhance the biomedical and tribological properties of the materials. In this work, titanium oxide layers are synthesized on titanium using direct current (DC) plasma oxidation. X-ray diffraction analysis reveals that the titanium oxide layers have both the rutile and anatase structures. Nano-hardness test, pin-on-disc wear experiment, scratch adhesion test and platelet adhesion investigation are conducted to evaluate the mechanical properties and blood compatibility of the titanium oxide layers. The results show that the nano-hardness of titanium layer reaches 1000 kg/mm/sup 2/ and above. The wear resistance of the titanium oxide layer increases by a factor of 6 and is about the same as that of titanium nitride films synthesized by ion beam enhanced deposition (IBED). The adhesion strength between the titanium oxide layer and titanium matrix is determined to be as high as 20N. The blood compatibility of the titanium oxide layer is observed to be comparable to that of low temperature isotropic pyrolytic carbon (LTIC), a material generally regarded to have good blood compatibility. Our results thus indicate that titanium oxide layers fabricated by this method have good blood compatibility and mechanical properties.