In this work, the interaction between hydrogen peroxide (H2O2) and a gradient structured Ti was investigated extensively. The gradient structured Ti (SMAT Ti) was produced by surface mechanical attrition treatment (SMAT), and then it was immersed in H2O2 solution for different time until 48 h at room temperature (25 degrees C). The structure and surface morphology evolution were examined by Raman spectra and scanning electron microscopy (SEM). The formation mechanism of nanoporous titania was discussed based on above results. (c) 2007 Elsevier B. V. All rights reserved.