The tribological protection of carbon fiber reinforced epoxy composites (CFC) is essential for broadening their use from structural to functional applications, e.g., to linear bearings in mechanical engineering. However, their wear resistance in sliding and rolling contacts is low. This work focusses on the possibility of improving their tribological properties by the application of thin hard multi-layered coatings. Chromium nitride (CrN) single layer and chromium-CrN multilayer coatings of ~4 µm thickness, partly finished with a 1 µm diamond-like carbon (DLC) top layer, were deposited by magnetron sputtering at low temperatures on soft CFC and for comparison of the mechanical behavior on comparatively hard austenitic steel substrates. Structural investigations showed especially that the multilayer coatings possess a very fine grained, columnar microstructure and a very low density of intercolumnar micro-cracks, while the single layer coatings possess a coarse structure. The indentation testing and the analysis of the deformed and fractured cross-sections revealed a tougher behavior with improved plastic deformability of the multilayers in comparison to CrN single layers. However, in wear testing only coatings with DLC top layers significantly improved the tribological material properties of CFC. This is due to the reduced shear forces in sliding on low-friction DLC coatings on the soft epoxy-based CFC, decreasing the total dynamic stresses during sliding under high loads.

Development of a new generation of multilayer coatings as well as a microstructure understanding of the mechanisms operating at the smallest length scale (nano- and atomic-scale) during wear, opens an avenue for the fabrication of future high-tech functional surfaces. Coatings for the presented work were fabricated by a pulsed laser deposition supported by magnetron sputtering. Microstructure characterization has been performed on as-deposited coatings as well as on coatings after mechanical wear test. Thin foils for detailed TEM microstructure observation were cut directly from the mechanically deformed area, using the FIB technique. Wear mechanisms operating at the small length scale of TiN/Ti/a-C : H multilayer coatings subjected to mechanical wear was studied by means of transmission electron microscopy (TEM). Cracking of the multilayer systems propagated layer by layer. The highest stress concentration during mechanical uploading was moved through the multilayer coating by breaking only one layer at the time.

Carbon fiber structures provide strength, stiffness, and fatigue resistance. Carbon-based materials show, however, significant oxidative degradation in air beginning at temperatures in the region of 400 °C. Therefore, a coating concept for carbon–carbon composites consists of an inner part, which serves as a structural link with stress compensation ability to the carbon substrate, and an outer part, which acts as a diffusion barrier. In the presented paper, chromium/chromium nitride (Cr/CrN) multilayer structure has been selected as the inner part. The outer part of the coating, in the presented paper, was hydrogenated amorphous carbon (a-C:H). Among doping metals, Cr, as one of the carbide formed elements, possesses an attractive combination of properties (corrosion resistance, wear resistance, etc.). Thus, in the presented paper, a-C:H part of the coating was implanted by Cr nanocrystals. Coatings were deposited by means of magnetron sputtering technique. They were subjected to complex investigations. Mechanisms of a mechanical wear of analyzed systems were presented, focusing on the cracking propagation in ball-on-disc tests using a 1 N and 5 N applied loads for 20 000 cycles. Complex microstructure analysis of presented nano-multilayer coatings, before and after mechanical tests, were performed by means of transmission electron microscopy (TEM). The microstructure characterization revealed that cracking, which was propagating in the outer part of the coating (in the carbon part) in the layer with lower nano-particle content, was stopped at the interface with the higher nano-particle content layer. In the case of the inner part of the coating (Cr/Cr₂N), ceramic layers showed brittle cracking, while metallic (Cr) ones deformed plastically.

In this work, we present the results of defects analysis concerning ZnO and Al₂O₃ layers deposited by atomic layer deposition (ALD) technique. The analysis was performed by the X-band electron paramagnetic resonance (EPR) spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) methods. The layers were either tested as-deposited or after 30 min heating at 300 °C and 450 °C in Ar atmosphere. TEM and XPS investigations revealed amorphous nature and non-stoichiometry of aluminum oxide even after additional high-temperature treatment. EPR confirmed high number of defect states in Al₂O₃. For ZnO, we found the as-deposited layer shows ultrafine grains that start to grow when high temperature is applied and that their crystallinity is also improved, resulting in good agreement with XPS results which indicated lower number of defects on the layer surface.

Formamidinium lead iodide (FAPbI₃)-based perovskite solar cells have gained immense popularity over the last few years within the perovskite research community due to their incredible opto-electronic properties and the record power conversion efficiencies (PCEs) achieved by the solar cells. However, FAPbI₃ is vulnerable to phase transitions even at room temperature, which cause structural instability and eventual device failure during operation. We performed post-treatment of the FAPbI₃ surface with octyl ammonium iodide (OAI) in order to stabilize the active phase and preserve the crystal structure of FAPbI₃. The formation of a 2D perovskite at the interface depends on the stoichiometry of the precursor. By optimizing the precursor stoichiometry and the concentration of OAI, we observe a synergistic effect, which results in improved power conversion efficiencies, reaching the best values of 22% on a glass substrate. Using physical and detailed optical analysis, we verify the presence of the 2D layer on the top of the 3D surface of the perovskite film.