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- 2017 (13) (entfernen)
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Schlagworte
- Femtosecond laser (6)
- Laser-induced periodic surface structures (LIPSS) (4)
- Femtosecond laser ablation (3)
- Laser ablation (3)
- Laser-induced periodic surface structures (3)
- Steel (3)
- Fluid transport (2)
- Nanostructures (2)
- Surface wetting (2)
- Anodic oxidation (1)
- Auger electron spectroscopy (1)
- Biofilms (1)
- Biomometics (1)
- Bug (1)
- CIGSe (1)
- CIGSe micro solar cells (1)
- Cell adhesion (1)
- Copper-indium-gallium-diselenide (1)
- Darkfield microscopy (1)
- Dielectrics (1)
- Diffusion (1)
- Electromagnetic scattering (1)
- Femtosecond laser patterning (1)
- Friction (1)
- Indium islands (1)
- Laser Processing (1)
- Laser-induced forward transfer (LIFT) (1)
- Laser-induced periodic surface structures, LIPSS (1)
- Lizard (1)
- Micro-concentrator solar cell (1)
- Microbial adhesion tests (1)
- Oxidation (1)
- Pacemaker (1)
- Raman spectroscopy (1)
- Refractive index (1)
- Scattering (1)
- Silicate glasses (1)
- Structural relaxation (1)
- Surface functionalization (1)
- Surface plasmon polariton (1)
- Surface texture (1)
- Titanium (1)
- Titanium alloy (1)
- Titanium nitride films (1)
- Ultrafast microscopy (1)
- Wear (1)
Indium islands on molybdenum coated glass can be grown in ordered arrays by surface structuring using a femtosecond laser. The effect of varying the molybdenum coated glass substrate temperature and the indium deposition rate on island areal density, volume and geometry is investigated and evaluated in a physical vapor deposition (PVD) process. The joined impact of growth conditions and spacing of the femtosecond laser structured spots on the arrangement and morphology of indium islands is demonstrated. The results yield a deeper understanding of the island growth and its precise adjustment to industrial requirements, which is indispensable for a technological application of such structures at a high throughput, for instance as precursors for the preparation of Cu(In,Ga)Se2 micro concentrator solar cells.
Titanium nitride (TiN) was coated on different substrate materials, namely pure titanium (Ti), titanium alloy (Ti6Al4V) and steel (100Cr6), generating 2.5 μm thick TiN layers. Using femtosecond laser pulses (30 fs, 790 nm, 1 kHz pulse repetition rate), large surface areas (5 mm × 5 mm) of laser-induced periodic surface structures (LIPSS) with sub-wavelength periods ranging between 470 nm and 600 nm were generated and characterized by optical microscopy (OM), white light interference microscopy (WLIM) and scanning electron microscopy (SEM). In tribological tests, coefficients of friction (COF) of the nanostructured surfaces were determined under reciprocating sliding conditions (1 Hz, 1.0 N normal load) against a 10-mm diameter ball of hardened 100Cr6 steel during 1000 cycles using two different lubricants, namely paraffin oil and engine oil. It turned out that the substrate material, the laser fluence and the lubricant are crucial for the tribological performance. However, friction and wear could not be significantly reduced by LIPSS on TiN layers in comparison to unstructured TiN surfaces. Finally, the resulting wear tracks on the nanostructured surfaces were investigated with respect to their morphology (OM, SEM), depth (WLIM) and chemical composition by energy dispersive X-ray spectroscopy (EDX) and, on one hand, compared with each other, on the other hand, with non-structured TiN surfaces.
Miniaturized pacemakers with a surface consisting of a Ti alloy may have to be removed after several years from their implantation site in the heart and shall, therefore, not be completely overgrown by cells or tissue. A method to avoid this may be to create at the surface by laser-ablation self-organized sharp conical spikes, which provide too little surface for cells (i.e., fibroblasts) to grow on. For this purpose, Ti-alloy substrates were irradiated in the air by 790 nm Ti:sapphire femtosecond laser pulses at fluences above the ablation threshold. The laser irradiation resulted in pronounced microstructure formation with hierarchical surface morphologies. Murine fibroblasts were seeded onto the laser-patterned surface and the coverage by cells was evaluated after 3–21 days of cultivation by means of scanning electron microscopy. Compared to flat surfaces, the cell density on the microstructures was significantly lower, the coverage was incomplete, and the cells had a clearly different morphology. The best results regarding suppression of cell growth were obtained on spike structures which were additionally electrochemically oxidized under acidic conditions. Cell cultivation with additional shear stress could reduce further the number of adherent cells.