The Preparation And Properties Research Of Ti-O Films

In this paper, the chemical composition, microstructure, energy band, morphology, physical, chemical, and mechanical properties and the blood compatibility of Ti-O films were systematically studied, and the relationship between the factors and its blood compatibility was evaluated, and it was attempted to apply this type of coating of artificial cardiovascular devices.Ti-O films with different crystalline structure (rutile, anatase, a mixture of rutile and anatase, and amorphous) were synthesized by unbalanced pulsed or DC magnetron sputtering on several kinds of substrates. Their composition, structure and surface properties could be controlled in large-scale by regulation of the process parameters.The microstructure of the Ti-O films mainly depends on the energy of the particles impinging on the substrate and the deposition temperature. Increased electrical conductivity of the substrate, substrate bias voltage, increased sputtering power density, oxygen partial pressure, substrate temperature and annealing temperature are conditions, which favor the formation of rutile titanium oxide. The surface composition of the films is stoichiometric TiO₂, but the bulk composition of the films is non-stoichiometric TiO_2-x, and the element distribution of the films is very well along the depth profile. The O/Ti ratio of the prepared films increases with oxygen partial pressure during deposition. The valence band (VB) of the film surface is confined to energies between 2 and 8 eV, relative to the Fermi level (Ef) showing a general VB width 4.70 eV. By O-vacancydefects, Fermi level shifts to the conduction band at about 0.35 eV with n type semiconductor characteristic were obtained.The surface roughness of Ti-0 films increases slowly when the substrate bias voltage or annealing temperature increases, or when the oxygen partial pressure decrease. The integrity of the crystals could be directed by the process parameters as substrate temperature, substrate bias and annealing. The contact angle between the films and water and blood composition, i.e. the polar component of the surface energy of the films and the interface tension of the films with biological substances were influenced in a certain extent by the chemical composition, microstructure, morphology and integity of crystals of the films. As a consequence, also the blood compatibility was influenced by these factors. The mechanical properties of low temperature isotropic pyrolytic carbon (LTIC) and titanium alloy (Ti6A14V) improved obviously by a Ti-0 films surface modification. The deposition of a Ti interlayer improves substantially the adhesion strength of the Ti-0 film. The optical constants, including refractive index, absorbance index, extinction coefficient, reflectivity, and the density of Ti-0 films were calculated.The results of the platelets adhesion and thrombin time indicated that the oxygen content and integrity of crystals are the key factors, which influence the blood compatibility of the Ti-0 films. The Ti-0 films with rutile structure, n type semiconductor nature, band gap 3.1 3.2, hydrophilic, high polar component of the surface energy, approaching to stoichiometric ratio have excellent antithrombogenicity. The reason for the improved antithrombogenicity of Ti-0 films can be mainly attributed to its...