- First, two 1 mm thick aluminum plates of 99.999% Aluminum purity and 98% Aluminum and 2% Magnesium respectively, were mounted on a silicon block and polished on a rotary sander, followed by successive uses of finer grain sand paper from 1500, 2000, and 4000 grain and polished with alumina grains of 3, 1, and 0.5 µm diameters for 15 minutes.
- Second, after separating the plates from the silicon block, they were annealed from ambient temperature to 450oC in increments of 5oC/min for four hours, and then returned to ambient temperature in increments of 10 oC/min.
- Third the plates are electro polished in a chemical bath of H3PO4, H2SO4, and H2O of 4:4:2 weight proportions at 20 Volts (V) and a temperature of 85oC, and then dipped in ethanol and rinsed with distilled water four times.
- Fourth, a thin oxide layer is removed after a two minute bath at 90oC in a bath of 45 grams (g) per Liter (L) of chromic acid (H2CrO4), H3PO4 3.5% volume, and H2O 96.5% volume.
- Fifth, the first anodization of the plates was performed at a temperature of 1oC, at a potential of 40 V, and in an electrolyte solution of 0.3 Molarity (M) of Oxalic acid for four hours. The formed coat is then attacked in a bath of 0.2 M H2CrO4 and 0.4 M H3PO4 at a temperature of 90oC for thirty minutes in order to support the growth of perpendicular pores.
- Finally the plates are anodized in an electrolytic solution of 0.1 M H3PO4 at a temperature of 40oC for twenty five minutes. The figure illustrates the stages of production of the substrates.