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Abstract: Aluminium oxide coating was directly synthesized on aluminium alloy by micro-arc oxidation (MAO) in NaAlO2 solution. XRD results show that the coating consists of α-Al2O3 and γ-Al2O3 in its whole thickness; the content of α-Al2O3 in the coating is 64±4%. The coating consists of a relatively compact inner layer and a porous outer layer, and its porosity is 7–10%. The density of the coating is 3.47g/cm3, its highest hardness 22 GPa and elastic modulus 279 GPa appear at around 12 μm from interface. The thermal expansion coefficient of the coating is 7.38×10−6 K−1. The coating can suffer the thermal impact of 873 K; it indicates that the aluminium oxide coating possesses a good thermal shock-resistant and adhesion strength to the substrate. [Copyright &y& Elsevier]

The thermal conductivity at (220 to 480) K of anodic alumina film of (1.4 to 5) μm thick and about 30 % porosity, which is grown from aluminum foil, is reported. A laser flash technique was employed to carry out measurements of thermal diffusivity of layered anodic aluminum specimen, while the effective thermal conductivity of anodic alumina film was determined using a two-layered model, which is 1.22 W·m−1·K−1at 220 K and 1.71 W·m−1·K−1at 480 K. Agreement in the overlapping temperature range (220 to 300) K with the measurements of Chen is found. The results showed that the thermal conductivity of anodic alumina films has a temperature dependence of amorphous solids, and the apparent thickness dependence of thermal conductivity is not found for anodic alumina films. [ABSTRACT FROM AUTHOR]