Anodized aluminium membrane

Furneaux, R. C. and M. C. Thornton. 1988. Porous "ceramic membranes produced from anodizing aluminium. Brit. Cer. Proc., Advanced Ceramics in Chemical Process Engineering Eds. B. C. H. Steele and D. P. Thompson, vol. 43, pp. 93-101. 

Mesoporous alumina membranes ( anodic aluminium oxide , or AAO) are prepared by anodic oxidation of aluminium metal [1,2]. The cylindrical pores, perpendicular to the membrane surface, form hexagonal arrays of straight non-intersecting channels with pore densities up to lO Vcm. Their diameters are controllable within the range 5 - 100 nm as a linear function of anodisation voltage. These membranes are used as molecular sieves, and have also found application as templates for metallic nanowires [3,4,5,6], metal elusters and colloids [7,8], and carbon nanotubes [9,10]. 

Using porous anodic aluminium oxide films, Routkevitchand associates electrodeposited very thin CdS nanowires [49]. The alumina membranes were typically 1 - 3-pm thick with pore sizes ranging from 9 to 35 nm. The CdS was electrodeposited, using ac electrodeposition, from a DMSO solution containing CdCl2 and elemental S. The porous alumina, as anodized, was separated from the A1 by a dense oxide... 

Carturan G, Dal Toso R, Boninsegna S, Dal Monte R (2004) Encapsulation of functional cells by sol-gel silica actual progress and perspectives for cell therapy. J Mater Chem 14(14) 2087-2098 Cho S, Lee S, Jeong SH, Kim Y, Kim SC, Hwang W, Park J (2013) Anodic aluminium oxide membranes for immunoisolation with sufficient oxygen supply for pancreatic islets. Integr Biol 5(5) 828-834... 

Most of the work that has been carried out using porous membranes as hard templates was done on porous alumina (anodic aluminium oxide, AAO) or track-etched polycarbonate membranes. The general principle of nanotube formation relies on a continuous polymer film being formed on the inside of the pores that remains as a tubular structure once the template is removed. There are several possibilities as to how this polymer film can be formed inside the pore. A film can be obtained by wetting the pore with a polymer melt or a polymer solution. Alternatively, the polymerization of monomers... 

Cho, S.H., Walther, N.D., Nguyen, S.T. Hupp, J.T. (2005). Anodic aluminium oxide catalytic membranes for asymmetric epoxidation, Chem. Commun. pp.5331-3. 

Abstract Membrane reactors with a catalyst bed are designed to be used in various reactions, such as hydrogenation, dehydrogenation, oxidation and reforming reactions. The catalyst can be introduced into the reactor as a bed in several ways in the form, for example, of pellets, extrudates or tablets or it can be incorporated in the reactor as a catalytic membrane wall. However, in many cases, the studies concentrate on the membrane itself, the development of catalysts is ignored, and commercial catalysts are used in the experiments. Most of the catalysts tested are aluminium oxide (alumina, AI2O3) based, as alumina is a mature support and already well proven in convectional reactors. However, some new catalyst materials such as carbon nanotubes (CNTs), carbon black, gels and anodic aluminium oxide (AAO) are developed as innovative catalyst supports and catalysts, since there is also a need for new catalysts for membrane reactors. 

Microporous alumina membranes electrochemically grown by anodizing of aluminium can be also produced with an excellent controlling of pore size distribution and porosity [34]. 

The MF membranes are usually made from natural or synthetic polymers such as cellulose acetate (CA), polyvinylidene difiuoride, polyamides, polysulfone, polycarbonate, polypropylene, and polytetrafiuoroethylene (FIFE) (13). Some of the newer MF membranes are ceramic membranes based on alumina, membranes formed during the anodizing of aluminium, and carbon membrane. Glass is being used as a membrane material. Zirconium oxide can also be deposited onto a porous carbon tube. Sintered metal membranes are fabricated from stainless steel, silver, gold, platinum, and nickel, in disks and tubes. The properties of membrane materials are directly reflected in their end applications. Some criteria for their selection are mechanical strength, temperature resistance, chemical compatibility, hydrophobility, hydrophilicity, permeability, permselectivity and the cost of membrane material as well as manufacturing process. 

The third route is defined as substractive (lUPAC), in that certain elements of an original structure are selectively removed to create pores. Examples include the formation of porous metal oxides by thermal decomposition of hydroxides, of porous glasses by chemical etching, of activated carbons by controlled pyrolysis, of ceramic foam membranes by burning off a polymer (e.g. polyurethane), of alumina by anodic oxidation of aluminium to give oriented cylindrical pores with a narrow size distribution. 

Mozalev, A., Magaino, S., and Imai, H. 2001. The formation of nanoporous membranes from anodically oxidized aluminium and their application to Li rechargeable batteries. Electrochimica Acta 46, 2825-2834. 

Note All the numbers quoted are based on real components and assume a cell with 50 pm lithium foil anode, 85 pm PE0-LiC104 electrolyte membrane and 10 pm aluminium current collectors. Numbers are for unpackaged laminate only. 

Furneaux, R.C., Rigby, W.R. Davidson, A.P. (1989). The formation of controlled porosity membranes from anodically oxidized aluminium. Nature Vol.337 pp.147-149. 

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