Effect of Manganese Content on the Fabrication of Porous Anodic Alumina

Abstract

The influence of manganese content on the formation of well-ordered porous anodic alumina was studied. Porous anodic alumina has been produced on aluminium substrate of different manganese content by single-step anodizing at 50 V in 0.3 M oxalic acid at 15°C for 60 minutes. The well-ordered pore and cell structure was revealed by subjecting the porous anodic alumina to oxide dissolution treatment in a mixture of chromic acid and phosphoric acid. It was found that the manganese content above 1 wt% impaired the regularity of the cell and pore structure significantly, which can be attributed to the presence of secondary phases in the starting material with manganese content above 1 wt%. The pore diameter and interpore distance decreased with the addition of manganese into the substrates. The time variation of current density and the thickness of porous anodic alumina also decreased as a function of the manganese content in the substrates.

Synthesis of Nanoporous Anodic Alumina by Anodic Oxidation of Low Purity Aluminum Substrates

“…Recently, Voon et al have investigated the effect of Mn content in the Al substrate on the anodizing behavior and the structure of anodic alumina layers formed by potentiostatic anodization in oxalic acid electrolytes [56]. The main conclusions drawn from this study are in general agreement with the results described above, obtained in our group [41,47].…”

“…In general, the higher Mn content in the substrate, the lower regularity of as synthesized oxide. For the alloys with Mn content <1.0 wt%, it is possible to achieve the hexagonal arrangement of pores, however, their shape and size are less uniform than those obtained from the high-purity substrate [56]. Moreover, a number of pits appear on the surface of AAO layers formed from the substrate with a higher Mn content.…”

“…As a consequence, the local minimum of the current density as well as the steady state current density are achieved within a longer anodizing time. The lower current densities result also in lower oxide growth rates [56].…”

“…On the other hand, Vonn et al reported that the presence of Mn can strongly influence the uniformity of the oxide structure [56]. In general, the higher Mn content in the substrate, the lower regularity of as synthesized oxide.…”

“…A further increase of the Mn content (up to 2.0 wt%) in the starting material disturbs the hexagonal pore arrangement to a greater extend. As a result, the sizes of the pits and cracks in the oxide structure also increase [56].…”