An analysis of the elastic properties of a porous aluminium oxide film by means of indentation techniques

Abstract

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. a b s t r a c tThe elastic modulus of thin films can be directly determined by instrumented indentation when the indenter penetration does not exceed a fraction of the film thickness, depending on the mechanical properties of both film and substrate. When it is not possible, application of models for separating the contribution of the substrate is necessary. In this work, the robustness of several models is analyzed in the case of the elastic modulus determination of a porous aluminium oxide film produced by anodization of an aluminium alloy. Instrumented indentation tests employing a Berkovich indenter were performed at a nanometric scale, which allowed a direct determination of the film elastic modulus, whose value was found to be approximately 11 GPa. However, at a micrometric scale the elastic modulus tends toward the value corresponding to the substrate, of approximately 73 GPa. The objective of the present work is to apply different models for testing their consistency over the complete set of indentation data obtained from both classical tests in microindentation and the continuous stiffness measurement mode in nanoindentation. This approach shows the continuity between the two scales of measurement thus allowing a better representation of the elastic modulus variation between two limits corresponding to the substrate and film elastic moduli. Gao's function proved to be the best to represent the elastic modulus variation.

Nanomechanical characterization and modeling of anodized porous aluminum oxide thin films with photografted anti-biofouling polymer brushes on their pore walls

“…But for the AAO films, the modulus and hardness increase with increasing depth because of the substrate effect. The values of the elastic modulus and hardness obtained for the pure AAO thin film are 35.80 GPa and 1.13 GPa, respectively, and are in good agreement with the values reported in the literature (Vojkuvka et al 2012;Hemmouche et al 2013). The SPE-coated AAO thin film shows similar elastic modulus and hardness values to the non-coated ones, mainly due to the low volume fraction of the polymer, and the fact that the stronger AAO film dominates the mechanical properties of the composite structure; this is confirmed by the FEA results below.…”

Study of the mechanical behavior and corrosion resistance of hydroxyapatite sol–gel thin coatings on 316 L stainless steel pre-coated with titania film

“…Consequently, a model must be applied for separating the influence of the substrate on the measurement. In the case of porous coating, Hemmouche et al [25] have tested numerous models related to the elastic modulus determination of thin films. They conclude that the model of Gao et al [26] leads to the best prediction and that it has the advantage of being independent of any fitting parameter.…”

Small-scale indentation of a hemispherical inhomogeneity in an elastic half-space

“…Indentation technique (Hardy et al, 1971;Follansbee and Sinclair, 1984;Hill et al, 1989) has been proved very useful in testing mechanical properties of small material samples and, in particular, thin films (Antunes et al, 2007;Hemmouche et al, 2013). By modeling the sample configuration as an elastic layer bonded to a rigid base or to an elastic substrate, one can study the corresponding thickness effect (Hayes et al, 1972; or the substrate effect (Yu et al, 1990;Gao et al, 1992;Chen and Vlassak, 2001;Perriot and Barthel, 2004;Argatov and Sabina, 2014).…”