Polysilazanes are excellent coating materials, because of their self‐crosslinking in air at low temperatures, high chemical and thermal stability, elevated hardness, and excellent adhesion to many different substrates. Therefore, coatings of two chemically different polysilazanes (crosslinked Durazane 1800 (HTTS)/perhydropolysilazane (PHPS)) are deposited by either dip or spray coating and crosslinked at 200 or 300 °C in air to investigate the chemical composition, surface energy, and coating adhesion in dependency on the precursor type and crosslinking temperature. The silazane HTTS possesses a higher amount of nonpolar organic groups resulting in a lower surface free energy. The anti‐adherence properties are investigated by using a phenolic resin via pull‐off adhesion, which is slightly reduced from 13 MPa for uncoated aluminum to less than 10 MPa for HTTS coated substrates. The addition of different amounts of poly(tetrafluoroethylene) (PTFE) particles causes a remarkable reduction of the surface free energy leading to a strongly reduced pull‐off adhesion of less than 4 MPa of the phenolic resin from the HTTS/PTFE coated substrates. The anti‐adherent properties remain even after repeated pull‐off tests. Because of the excellent properties, the HTTS/PTFE coatings are a very suitable system for easy mold release of plastic parts from metal molds and to replace commercial nonstick PTFE coatings.

No abstract

Protective ceramic‐based coatings are frequently the most suitable solutions for problems like corrosion and wear. It has been shown that the precursor technology is suitable for the preparation of ceramic coatings by pyrolysis in a furnace. However, the required high temperature for the preparation of the ceramic coatings limits this approach to high temperature‐resistant substrates. A very innovative approach to overcome this restriction is the use of laser radiation as a thermal source for the pyrolysis of the preceramic polymer. In this paper, we report on a coating system, for steel substrates, consisting of a polysilazane (Durazane 2250) bond coat and a hard and dense top‐coat composed of an organosilazane (Durazane 1800) with tetragonal ZrO2 particles and aluminum flakes as fillers pyrolyzed using Nd:YVO4 laser. The aluminum fillers led to a significant increase in absorption of the laser energy leading to the formation of a dense coating with a thickness up to 20 μm and a mainly cellular/columnar‐dendritic microstructure. The microstructure, mechanical, and tribological behaviors of these composite coatings are reported and compared to those of laser pyrolyzed glass/ZrO2‐filled polysilazane‐based coatings reported in the literature.

No abstract

No abstract