Sabine Apelt

In this work, the mechanism of the corrosion behavior of laser‐treated aluminum is studied. Two different laser techniques are used to fabricate the samples, direct laser interference patterning (DLIP) and direct laser writing (DLW), using nanosecond laser sources. The DLIP treatment uses a two‐beam optical configuration producing line‐like periodic structures. The DLW technique is employed to produce non‐periodic structures on the Al‐surface with the same cumulated fluences as in DLIP. The surface topography is analyzed by confocal microscopy, and the formation of oxide layers is investigated by scanning electron microscopy of cross‐sections produced using a focused ion beam. Wetting measurements performed on the laser‐treated samples exhibit a contrasting behavior, leading to either superhydrophobic or superhydrophilic states. In the case of the DLIP treatment, the static water contact angle is increased from 81° up to 158°, while for DLW, it decreases to 3°. Electrochemical tests demonstrate a decreased corrosion rate after laser treatment. Additionally, findings indicate no correlation between wettability and corrosion reduction. Therefore, the improvement in corrosion resistance is mainly attributed to the oxide layer formed by laser treatment. Although similar corrosion rates are achieved for both treatments, surfaces produced with DLIP can be beneficial when additional surface properties are required.

The ferro‐, pyro‐ and piezoelectric properties of poly(vinylidene fluoride‐co‐trifluoroethylene) P(VDF‐TrFE) have created interest with regard to its application in aqueous and ambient surroundings for sensors, functional coatings, and in the field of life sciences. P(VDF‐TrFE) thin films are usually applied via spin‐coating, but dip‐coating will be advantageous especially for irregularly shaped substrates. The morphology of dip‐ and spin‐coated semi‐crystalline thin films is studied as a function of both the film thickness and the annealing temperature. The characterization of the films is carried out by grazing incidence wide‐angle X‐ray scattering (GIWAXS), X‐ray reflectometry (XRR), and infrared reflection absorption spectroscopy (IRRAS). Atomic force microscopy measurements (AFM) are used to examine the resulting topography. It is found that both spin‐ and dip‐coated thin films crystallize in the desired edge‐on orientation, but the overall crystallinity after dip‐coating is decreased compared to the spin‐coated films of comparable thickness and the resulting roughness is increased. The higher roughness is most probably caused by the slower evaporation of the solvents and a secondary crystallization process at the air‐polymer interface.