Wear resistance of sol-gel TiO2 thin films to prosthetic heart valve prosthesis

FAVILLA, P.C.; ALTERACH, M.A.; MARIO ROBERTO ROSENBERGER; SCHVEZOV, C. E.

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, one probable cause maybe its strong dependences with the fabrication process.  The wear resistance of TiO2 thin films fabricated by the sol gel dip-coating technique was measured. A rotating ball-on-flat device was used in order to reproduce the movement of a pivot. Lubricated tests were performed, employing a 6.35 mm in diameter hard steel ball as counterface. A constant 7 rpm and loads ranged from 1 to 5 N were chosen to perform the test; these values exceed more than 50 times the stress calculated on the valve pivot. Scratch test, SEM observations and RX diffraction were performed to characterize the film.  The influence of three dip-coating process parameters: the withdrawing velocity, the aging time and the heat treatment temperature, beside the number of layers were studied. Film thicknesses ranged between 50 to 200 nm were obtained.  The withdrawing velocity and aging time had influence in the film thickness but negligible influence on the wear resistance. On the other hand, the heat treatment temperature; which produces different crystal structures, and the numbers of layer had more influence on the wear resistance. Higher temperature and more layers increased the wear resistance. Although, when the number of layers increased the failure by adhesion increased.