| AVS 64th International Symposium & Exhibition | |
| Applied Surface Science Division | Tuesday Sessions |
| Session AS+TF-TuA |
| Session: | Problem Solving Using Surface Analysis in the Industrial Laboratory |
| Presenter: | Shoshan Abrahami, Vrije Universiteit Brussel (VUB), Belgium |
| Authors: | S. Abrahami, Vrije Universiteit Brussel (VUB), Belgium T. Hauffman, Vrije Universiteit Brussel (VUB), Belgium De KoK, Fokker Aerostructures BV, Papendrecht, The Netherlands Gudla, Technical University of Denmark (DTU), Denmark Ambat, Technical University of Denmark (DTU), Denmark J.M.C. Mol, TU Delft, Netherlands H. Terryn, Vrije Universiteit Brussel, Belgium |
| Correspondent: | Click to Email |
Aluminium pretreatment for bonding purposes needs to produce a stable oxide with optimal chemical and structural characteristics for adhesion with the organic resin. Contributions at the interface region can be related to adsorptive interactions as well as mechanical interlocking between the two phases. To separate between these two effects, we applied either barrier-type or porous-type oxides on two sets of specimens. This paper presents an overview of a study on the relation between oxide properties and interfacial bonding, as affected by the nature of electrolyte and the anodizing conditions, as well as changes in the chemistry of the organic resin (epoxy, phenol, silanes). A detailed characterization of different anodic oxides and its effect on the adsorption of resin-derived functional molecules was performed using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Results indicate significant changes in the chemical composition of the oxides as a function of the electrolyte1. Mechanical peel test performance indicate that the initial bond strength is independent of the oxide surface chemistry, while the stability under the ingress of water is correlated to the amount of surface hydroxyls2. The presence of phosphates and sulphates did not alter bonding mechanisms, only the availability of hydroxyls. Further, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are used to characterize the geometrical modifications to the pore- and oxide structure in porous-type oxides. In addition, energy-dispersive X-ray spectroscopy (EDS) profiles were acquired on TEM cross-sections to assess the oxide structure and concentration of resin inside the pores. Linking these morphological features to peel results show that two types of modifications are crucial for the formation of a strong and durable bonding3. A minimum pore size is needed for the resin to fill the oxide pores for good initial adhesion. Surface roughness, on the other hand, was found beneficial for the durability of the bond upon the ingress of water. Overall, the results demonstrate that both surface chemistry and oxide morphology contribute to the strength and durability of an adhesive bond.
1. Abrahami, S. T., et al., XPS Analysis of the Surface Chemistry and Interfacial Bonding of Barrier-Type Cr(Vi)-Free Anodic Oxides. J. Phys. Chem. C 2015, 119, 19967-19975.
2. Abrahami, S. T., et al., Effect of Anodic Aluminum Oxide Chemistry on Adhesive Bonding of Epoxy. J. Phys. Chem. C 2016, 120, 19670-19677.
3. Abrahami, S. T., et al., Interface Strength and Degradation of Adhesively Bonded Porous Aluminum Oxides npj Materials Degradation 2017, in press.