In this study, a new, relatively simple fabrication method for forming a mesoporous Al(OH)3 film onAl substrates was demonstrated. This method, i.e., alkali surface modification, was simply comprised of dippingthe substrate in a 5×10-3M NaOH solution at 80oC for one minute and then immersing it in boiling waterfor 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 theXPS analysis, the flake-like morphology after the alkali surface modification was mainly composed of Al(OH)3,with a small amount of Al2O3. The mesoporous Al(OH)3 layer was composed of three regions: an amorphous-rich region, a region of mixed amorphous and crystal domains, and a crystalline-rich region near the Al(OH)3layer surface. It was confirmed that the stabilization process in the alkali surface modification stronglyinfluenced the crystallization of the mesoporous Al(OH)3 layer.

Aluminum hydroxides were synthesized by a simple electrolytic reaction of aluminum plates. The aluminum hydroxide, boehmite (AlO(OH)), was predominantly formed in the application of electrical potential at and above 30V, while the mixture of bayerite () and boehmite (AlO(OH)) phases were formed below 20V. The boehmite has a clear fibrous structure controlled on nanometer scale. On the contrary, the bayerite consists of the typical hourglass or semi-hourglass shaped coarse crystals as a result of aggregation of various crystals stacked together. The specific surface area of the boehmite nanofiber was markedly high, approaching at about .

The results obtained are summarized as follows; (1) Boehmite produced in the high temperature and acid region showed a nano fibrous shape with several nm in diameter and several hundreds nm in length having high specific surface areas with a maximum value of . (2) In order to obtain nano fibrous boehmite with high surface areas from nano metal powder, the hydrolysis reaction should be done at a high temperature over , high acidity under pH 6, and terminated before a transition to the bayerite phase.