Formation Mechanism of Mesoporous Aluminum Hydroxide Film by Alkali Surface Modification

Abstract

In this study, a new, relatively simple fabrication method for forming a mesoporous Al(OH) 3 film on Al substrates was demonstrated. This method, i.e., alkali surface modification, was simply comprised of dipping the substrate in a 5 × 10 -3 M NaOH solution at 80 o C for one minute and then immersing it in boiling water for 30 minutes. After alkali surface modification, a mesoporous Al(OH) 3 film was formed on the Al substrate, and its chemical state and crystal structure were confirmed by XPS and TEM. According to the results of the XPS analysis, the flake-like morphology after the alkali surface modification was mainly composed of Al(OH) 3 , with a small amount of Al 2 O 3 . The mesoporous Al(OH) 3 layer was composed of three regions: an amorphousrich region, a region of mixed amorphous and crystal domains, and a crystalline-rich region near the Al(OH) 3 layer surface. It was confirmed that the stabilization process in the alkali surface modification strongly influenced the crystallization of the mesoporous Al(OH) 3 layer.