Buckling pattern of TiO2 nanotube film

Substrate straining test was carried out to study the buckling pattern of TiO2 nanotube film. The results show that the tensile strains of buckling occurrence of TiO2 nanotube films without annealing, with 250°C annealing and with 400°C annealing are 2.5%, 8.9% and 7.8%, respectively, which indicates the modifying effects of temperature annealing. Through the SEM observation, the critical buckling stresses of TiO2 nanotube films without annealing, with 250°C annealing and with 400°C annealing can be estimated as 180.4, 410.2 and 619.5 MPa, respectively. The critical buckling stress of TiO2 nanotube films with 250°C annealing from AFM observation is estimated as 470.2 MPa, which indicates good agreement with the critical buckling stress from SEM observation. The true stress and the critical energy release rate of TiO2 nanotube film with 250°C annealing are given as 840.3 MPa and 77.2 J/m2, respectively. Excellent agreement of the critical energy release rate of TiO2 nanotube film with 250°C annealing in terms of buckling perspective and crack perspective is obtained.