Development of a theory for the determination of the composition of the anodizing solution inside the pores during the growth of porous anodic Al2O3 films on aluminium by a transport phenomenon analysis

Effect of the Anodizing Temperature on Microstructure and Tribological Properties of 6061 Aluminum Alloy Anodic Oxide Films

Anodizing a simple and effective method to improve the wear resistance of 6061 aluminum alloy. In this study, the microstructure of 6061 aluminum alloy oxide films (AAO) was adjusted by changing the electrolyte temperature (5, 15, and 25 °C) using 160 g/L sulfuric acid as the electrolyte. The phase composition, microstructure, and morphological characteristics of the specimens were detected using X-ray diffractometer and field emission scanning electron microscopy (SEM). The hardness, elastic modulus, and tribological properties of the films were examined using hardness testers and a rotary friction tester. The results showed that as the temperature of the electrolyte increases, the surface of the oxide films changes from uniformly distributed small-sized pores to a coral-like loose porous structure, and the thickness of the films increases. The electrolyte temperature has a significant effect on the friction performance of the AAO films. When the solution temperature decreases from 25 to 5 °C, the steady-state friction coefficient decreases from 0.46 to 0.39. According to the morphology of the wear tracks, it can be determined that the main wear mechanism of AAO films gradually changes from delamination wear to abrasive and adhesive wear, and the wear rate drops by ~69%.

Usage of neural network to predict aluminium oxide layer thickness

This paper shows an influence of chemical composition of used electrolyte, such as amount of sulphuric acid in electrolyte, amount of aluminium cations in electrolyte and amount of oxalic acid in electrolyte, and operating parameters of process of anodic oxidation of aluminium such as the temperature of electrolyte, anodizing time, and voltage applied during anodizing process. The paper shows the influence of those parameters on the resulting thickness of aluminium oxide layer. The impact of these variables is shown by using central composite design of experiment for six factors (amount of sulphuric acid, amount of oxalic acid, amount of aluminium cations, electrolyte temperature, anodizing time, and applied voltage) and by usage of the cubic neural unit with Levenberg-Marquardt algorithm during the results evaluation. The paper also deals with current densities of 1 A·dm⁻² and 3 A·dm⁻² for creating aluminium oxide layer.

Progress in Nano-Engineered Anodic Aluminum Oxide Membrane Development

The anodization of aluminum is an electro-chemical process that changes the surface chemistry of the metal, via oxidation, to produce an anodic oxide layer. During this process a self organized, highly ordered array of cylindrical shaped pores can be produced with controllable pore diameters, periodicity and density distribution. This enables anodic aluminum oxide (AAO) membranes to be used as templates in a variety of nanotechnology applications without the need for expensive lithographical techniques. This review article is an overview of the current state of research on AAO membranes and the various applications of nanotechnology that use them in the manufacture of nano-materials and devices or incorporate them into specific applications such as biological/chemical sensors, nano-electronic devices, filter membranes and medical scaffolds for tissue engineering.

Polarization-dependent angular-optical reflectance in solar-selective SnOx:F/Al2O3/Al reflector surfaces

Polarization-dependent angular-optical properties of spectrally selective reflector surfaces of fluorine-doped tin oxide (SnOx:F) deposited pyrolytically on anodized aluminum are reported. The angular-reflectance measurements, for which both s- and p-polarized light are used in the solar wavelength range 0.3-2.5 microm, reveal strong spectral selectivity, and the angular behavior is highly dependent on the polarizing component of the incident beam, the total film thickness, and the individual thickness of the Al2O3 and the SnO2:F layers. The anodic A12O3 layers were produced electrochemically and varied between 100 and 205 nm in thickness. The SnOx:F films were grown pyrolytically at a temperature of 400 degrees C with film thicknesses varying in the range 180-320 nm. The reflectors were aimed at silicon solar cells, and good spectrally selective reflector characteristics were achieved with these thinly preanodized, SnOx:F/Al samples; that is, high cell reflectance was obtained for wavelengths below 1.1 microm and low thermal reflectance for wavelengths above 1.1 microm, with the best samples having values of 0.80 and 0.42, respectively, at near-normal angles of incidence. This corresponds to an anodic layer thickness of 155 nm. Both the angular calculations and the experimental measurements show that the cell reflectance is relatively insensitive to the incidence angle, and a low thermal reflectance is maintained up to an angle of approximately 60 degrees.