Martin Günthner

cBN particle filled SiCN precursor coatings

Abstract A polymer derived ceramic composite coating consisting of the polycarbosilazane ABSE (matrix) and cBN (filler) is developed. The final coating thickness is varied by adjusting the withdrawal speed, the viscosity of the solution and the pyrolysis temperature. The coatings exhibit excellent adhesion to the substrate confirmed by cross-cut and bending tests. The environmental barrier properties of the coatings were investigated with static, isothermal oxidation experiments testing coated and uncoated steel substrates. It was revealed that the weight gain during oxidation was strongly reduced by coating the substrates and hence the coatings offer the possibility to enhance the lifetime and performance of steel substrates under rough conditions.

Control of surface energy of silicon oxynitride films.

Microstructure and chemical composition determine the wetting property of solid surfaces. To achieve hydrophobicity or hydrophilicity, recent efforts have mostly focused on designed patterns and sophisticated surface modification. Here we show the fabrication of a dense amorphous silicon oxynitride (SiON) film by simple annealing of perhydropolysilazane (PHPS), which experiences significant and abrupt transition in surface energy as a function of temperature. The polar component of surface energy, derived from contact angle measurements, exhibits an increase of 20-40 times in an annealing temperature window of ~100 °C, which leads to a 5-fold increase of its total surface energy. On the basis of the chemical analyses, we propose a compositional gradient in the film. Due to this gradient, the hydrophilic SiON film, for instance, can be used as the bond coat material in a double-layer environmental barrier coating system with outstanding oxidation resistant properties.