Dynamics of formation of self-organized mesoporous AlO(OH)-alpha H2O structure in Al-metal surface hydrolysis in humid air

In humid air, a nascent Al-metal surface (S) with a surface Hg2+ catalyst hydrolyzes in divided reaction centers (micelles) with a vigorous exothermic reaction, {Al + 2OH(-)} + alphaH(2)O --> AlO(OH).alphaH(2)O + 3e(-) + H+. It yields amorphous AlO(OH).alphaH(2)O with a huge similar to90% porosity with alpha = 0.25. The primary driving forces of the reaction are the chemical potential mu(e) between the reaction species, the mechanical stress cr induced in expansion of S, and the flow of the reaction species. They drive it in a common direction perpendicular to S. The heat released in it flows primarily along S. It disrupts and stops the directional hydrolysis if the local temperature in the micelle reaches a critical value T-c (hot spot). The hot spot cools to the operating value T-0, and the reaction restarts and runs over to T-c in a periodic manner, at a time scale of Deltat(i) similar to 5 s, per the dynamics of hot spots, forming a self-organized mesoporous structure of 15-50-nm diameter ellipsoidal shaped particles (halo) separated through 3-5-nm pores. A pore, in continuous formation of the sample, forms in disrupted reaction during the hot spot as it cools from T-c t(o) T-0. The result is modeled in terms of the microstructure and dynamics of the hot spots.