Wear of anodic TiO2 thin films to prosthetic heart valve prosthesis

VERA, M.L.; ARES, A.E.; SCHVEZOV, C. E.; MARIO ROBERTO ROSENBERGER

Filadelfia

Conferencia; 18 International conference on wear of materials, WOM 2011; 2011

TiO2 thin films have good haemocompatibility properties suitable for implant use such as prosthetic heart valves. Little information about wear resistance of this film is available in the literature mainly, due to its strong dependences with the fabrication process.  The wear and adherence of TiO2 thin films fabricated by anodic oxidation using sulphuric acid were measured. A reciprocating ball-on-flat device with lubricated conditions was used with a 6.35 mm in diameter hard steel ball as counterface. A mean velocity of 2 cm/s and loads ranged from 1 to 5 N were chosen to perform the test; these loads values exceed more than 50 times the stress calculated for a hearth valve pivot. Scratch test, SEM observations and XR diffraction were performed to characterize the film.  The influence of the film thickness, which was controlled by the applied voltage (from 10 to 70 V) in the anodizing process, was related with the wear resistance.  The film thicknesses ranged between 20 to 170 nm. Amorphous films were obtained after the anodizing, and crystalline films were obtained by performing a thermal treatment at 500ºC.for 1 hour.  The wear resistance increases with the film thickness and is larger for the films with thermal treatment. In the same way, the adherence measured by scratch test indicates an increase in the critical valued when the thickness increased, where the failure mainly observed were smalls cracks in the side of the scratch.