Nanomechanical characterization of porous anodic aluminum oxide films by nanoindentation

Abstract

Nanostructured thin films have gained great interests in recent years due to their significantly enhanced properties and great potential for various applications. Nanoindentation techniques are commonly used to measure nanomechanical properties of thin films and the surface layers of bulk materials. In this article, nanoindentation tests coupled with computer modeling were proposed to characterize nanostructured porous anodic aluminum oxide (AAO) films grown on glass. A three-dimensional nanoindentation model was developed. The Young's modulus and hardness were measured by nanoindentation using a Berkowich pyramidal sharp tip indenter. The effects of the substrate and porous structure of the film on the coating measurements were investigated. The dilemma for extracting the mechanical properties of a porous structural film in nanoindentation has been pointed out, and an alternative approach of combined modeling/experimental provided a justification by considering the porous structure of the film and minimizing the influence of the substrate. Computer modeling results were validated by experimental data.

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

“…Because the CSM method was used, the mechanical properties are reported with respect to the indentation depths. The results show small variations in the modulus and hardness values with respect to depth for the glass substrate with an average value of 77.15 GPa for the elastic modulus and 4.75 GPa for the hardness which largely agree with results from literature (Hu et al 2016). But for the AAO films, the modulus and hardness increase with increasing depth because of the substrate effect.…”

“…Furthermore, a deeper understanding of the nanoindentation process can be approached by studying the stress and strain distributions in the film and the substrate, which hardly can be analyzed by experimental means. For AAO thin films, Hu et al developed a three-dimensional FE model to study the mechanical characteristics of the films, and to identify the effect of the glass substrate (Hu et al 2016).…”

Computational modeling of viscoplastic polymeric material response during micro-indentation tests

“…Moreover, similar schemes were used by other authors for the estimation of parameters in nanoindentation [21], or by simple trial and error approaches [16], for instance.…”

“…With regard to prescribed force vs prescribed displacement approaches, it is worth to mention that when a prescribed displacement approach is implemented in micro or nano-indentation FEM modeling, as generally adopted in the area [7,9,12,15,16,19,24,25,28,[60][61][62], a displacement function is used to simulates the indenter penetration (on the material to characterize) down to a maximum indentation depth and its withdrawn to the initial position. Thus, creep cannot be captured because the indenter is restricted to move when a maximum indentation is reached.…”

“…Regarding nano-indentation tests in experimental and computational modeling areas, there is a growing amount of research due to its technological relevance [3][4][5]. In this scenario, since the establishment o the Oliver-Pharr method for nonoidentation [6], there has been several works being conducted concerning the development of predictive models using the finite element method (FEM) to describe the behavior of: bulk metals [7][8][9][10][11][12], thin films and coatings [13][14][15][16][17][18], multilayers [19][20][21][22][23][24][25], human bone [26][27][28], as well as for other materials, for several applications. As for microidentation, there is not a large amount of work devoted to its computational modeling mainly when one mentions analyses that take into account load rate-dependent material response in polymers.…”