Debonding phenomenon of TiO2 nanotube film

Curvature method was used to measure the residual stress and substrate straining tensile test was carried out to study the debonding behavior of TiO2 nanotube film. The results indicate that the internal residual stress is −54 MPa. The strains of debonding initiation of TiO2 nanotube films without annealing, with 250 °C annealing and with 400 °C annealing are 2.6%, 5.1% and 8.6%, respectively, and the average radii of the debonding patches with debonding initiation are 27.5, 17.1 and 19.4 μm, respectively. The true critical debonding stresses of TiO2 nanotube films without annealing, with 250 °C annealing and with 400 °C annealing can be estimated as 220.4, 394.5 and 627.9 MPa, respectively. Interfacial shear lag model is modified and polynomial fitting equation of the interfacial shear strength of TiO2 nanotube film is demonstrated under debonding conditions. The modification and polynomial fitting are reliable since good agreement of the interfacial shear strengths after fitting is obtained compared with those results from the crack density analysis.