| Abstract [eng] |
Surface phenomena and resistance to the environment impact are very important for materials or structures that must perform their function in outdoor conditions. The aim of this work was to modify the wetting properties of stainless steel, reduce liming and improve resistance to the growth of microorganisms on the surface by ultra-short pulse laser exposure and deposition of a diamond-like carbon with incorporated SiOx composite coating. The necessary conditions (224-448 mJ/cm2, 1000-2000 p/mm) for the formation of laser-induced-periodic-surface-structures (LIPSS) were determined after performing power test. LIPSS are used in a variety of fields from biology to solar cells. To evenly cover the stainless steel surface with periodic structures, 2x2 mm squares were created by changing the spacing between scanning lines from 1 to 30 µm. Analysis by atomic force microscopy revealed that keeping a gap of 1 µm between the scanning lines, 900 nm periodicity structures are obtained with minimum fluence (224 mJ/cm2) and impulse density (1000 p/mm) applied. Further squares were made with 5-30 µm spacing between scanning lines. Then samples were photographed by optical microscope after laser exposure. Contact angle measurements showed that periodic structures made with 448 mJ/cm2 fluence, 2000 p/mm pulse density and 5 µm spacings increased the steel contact angle from 47 to 131º. Composite coating on the steel increased its wetting to 87º, but the expected increase of wetting angle on the stainless steel with periodic structures was not observed, the wetting angle reached only 126º. The liming test was performed by keeping the samples in a flow of hard water. This study showed that samples exposed to 224 mJ/cm2 of fluence with a pulse density of 1000 p/mm with a spacing of 30 µm between the scanning lines and composite coating on the top are covered the least. An antibacterial test was performed using microorganisms made for cleaning sewage pipelines. Samples were kept in running water with microorganisms for several weeks. Analysis with a dark field optical microscope revealed that the surface of the stainless-steel samples exposed to 224 mJ/cm2 of fluence at a density of 1000 p/mm at 30 µm spacings between the scanning lines with the composite coating was covered with biofilm the least. |
