Layer-by-layer deposition of barrier and permselective c-Oriented-MCM-22/silica composite films

A layer-by-layer deposition method is presented for the fabrication of compact c-oriented-MCM-22/silica films on aluminum alloys and porous (x-alumina discs. The film fabrication procedure combines deposition of platelike MCM-22 crystals on substrates by covalent attachment under reflux and/or by sonication-assisted covalent attachment (using the methods introduced by Yoon and co-workers and recently reviewed [Acc. Chem. Res. 2007, 40 (1), 29-40]) with evaporation-induced-self-assembly (EISA) of surfactant-templated silica. The composite c-oriented MCM-22/silica films exhibited corrosion resistance barrier properties comparable to commercial chromate conversion coatings. Moreover, they exhibited hydrogen ideal selectivities. (e.g., H-2/N-2 similar to 7) above those expected by Knudsen diffusion indicating molecular sieving potential.