Growth Kinetics and Morphology of Porous Anodic Alumina Films Formed Using Phosphoric Acid

Abstract

The growth kinetics o f porous alumina films formed b y anodic oxidation o f aluminum i n phosphoric acid under galvanostatic conditions was studied. Scanning electron microscope measurements, Faraday's law, and oxide film mass measurements was used t o analyze the growth kinetics and obtain film growth rates, pore density, and porosity. Current efficiency was also determined from these measurements. The effect o f current density and solution temperature on the oxide film growth rate and morphology was examined. The rate o f growth o f the alumina film was found t o increase with an increase i n current density. The rate o f growth was observed t o increase with temperature at low current densities (7.5 mA/cmZ), but was found t o exhibit a maximum as temperature was varied at high current densities (17.5 mA/cm2). The pore density was found t o decrease with an increase i n current density and with a decrease i n temperature. The porosity and the average cross-sectional pore area o f the films were found t o increase with anodization time and decrease with an increase o f current density and temperature. These results can be explained b y considering the interplay between film growth and oxide dissolution that controls the resulting film morphology. The understanding o f the effect o f process variables on film morphology that is gained b y this study provides the information that is needed t o prepare alumina films with well-defined and well-characterized morphology.

Porous anodic alumina microreactors for production of hydrogen from ammonia

“…Our anodization of 1100 aluminum at 30 V produced only 60 m of alumina with a specific area of 16 m 2 /g, between half and a third of the specific surface areas found elsewhere (Ihm and Ruckenstein, 1978;Jessensky et al, 1998;Patermarakis and Pavlidou, 1994;Shawaqfeh and Baltus, 1998;Shizaki et al, 2001;Wu et al, 2001). Alumina thicknesses up to a factor of 2 more than ours have also been reported for Al foils (Patermarakis and Pavlidou, 1994).…”

“…The posts also enhance mass transfer to catalytic surfaces under high flow conditions by acting as static mixers (Ihm and Ruckenstein, 1978). Anodized alumina has already been shown to be a useful catalyst support in other applications (Ihm and Ruckenstein, 1978;Jessensky et al, 1998;Patermarakis and Pavlidou, 1994;Shawaqfeh and Baltus, 1998;Shizaki et al, 2001). This material can be fabricated with straight pores having well-controlled pore sizes.…”

Fabrication and Magnetic Properties of FePt3 Nanowire Arrays

“…1), showing the almost perfect hexagonally arranged porous array with a pore radius of about 50 nm. The decreasing voltage method leads to uniform barrier layer thickness [13], and the composition of each sample corresponds to that of a constant ac electrodeposition voltage [14]. Electrodeposition is conducted for another 10 min to obtain much more length and a higher aspect ratio for the nanowires.…”

Formation of Niobium Oxide Film with Duplex Layers by Galvanostatic Anodization

“…12-15 Anodization at a current mode (galvanostatic anodization) has been mainly applied to study growth kinetics, 16,17 control of local catastrophic phenomena 18,19 or self-ordered structures in anodization of aluminum 20,21 and to produce TiO 2 nanotubes with periodical morphology. 22 However, there have not been many reports on the anodization of other valve metals by galvanostatic anodization.…”