Optical and mechanical studies on free standing amorphous anodic porous alumina formed in oxalic and sulphuric acid

Abstract

Anodic porous alumina (APA) membranes with a uniform pore arrangement typically serve as an ideal template for formation of different types of nanostructured materials. In the present work, APA membranes were synthesized using two-step anodization in 0.3 M of oxalic and 0.3 M of sulphuric acid under the anodization potential of 40 V and 20 V respectively, at 8 C. Alumina nanowires (ANW) were synthesized by the chemical etching of the APA membranes using phosphoric acid solution. The optical absorbance and reflectance measurements of APA membranes were performed on a spectrometer in the wavelength range of 200 600 nm. The band-gap energy (3.7 and 4.3 eV for oxalic and sulphuric acid) of APA membranes was determined from UV visible absorption data. The photoluminescence (PL) investigations have revealed the presence of F and F+ defect centers, which could be attributes to oxygen vacancy-related defect centers in oxalic (483 and 466 nm) and sulphuric (423 and 421 nm) alumina. The mechanical properties of amorphous APA membranes were investigated by micro- and nanoindentation techniques. The results indicate that highest hardness (7.70 GPA) and Young s modulus (138.80 GPA) for sulphuric alumina compared with oxalic alumina. In sulphuric alumina, more number of ANW were observed compared with oxalic alumina. 2018, Springer-Verlag GmbH Germany, part of Springer Nature.