Micro and nanoindentation analysis of porous anodic alumina prepared in oxalic and sulphuric acid

Abstract

In this article, the mechanical behavior of porous anodic alumina (PAA) structures obtained from two different electrolytes (oxalic and sulphuric acids) was investigated using micro and nanoindentation techniques. Regularity ratio (RR) of PAA structures was calculated using WSxM software and it was found that strength of the PAA structures varies with the RR of the pores. Micro hardness of the PAA structures was studied using 0.98, 9.8 N loads and it was observed that surface ring cracks were generated for 9.8 N load in oxalic acid. PAA structures formed in sulphuric acid exhibits an extremely high hardness of 7.5 GPa and Young's modulus as 146.5 GPa compared with oxalic acid due to low porosity. Results indicate that the indentation modulus and hardness of the PAA structures decrease with increasing pore size. Further the effect of porosity and regularity ratio of pores on mechanical properties of PAA structures was studied in detail. © 2016 Elsevier Ltd and Techna Group S.r.l.