Development of ceramic coatings on aluminium and plastics by laser pyrolysis of particle filled silazanes

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In the recent years 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 temperatures for the preparation of the ceramic coatings only allow the use of substrates with high melting points. Recently, it was demonstrated by us, that laser pyrolysis is also suitable for the formation of ceramic coatings on steel substrates. The specific input of laser radiation as the source of energy should lead to a reduction of thermal stresses of the substrate, thus enabling the preparation of ceramic coatings on substrates with low melting points. However, first tests with laser irradiation on coatings applied on an aluminium substrate showed, that the coefficient of thermal expansion (CTE) as well as the thermal conductivity have a strong influence on the process. A higher thermal conductivity leads to a faster heat dissipation. Furthermore, a high difference between the CTEs of the substrate and the coating increase the stresses generated. These problems lead to the delamination of the coating during or immediately after the laser pyrolysis. Thus, coating systems, which were successfully applied onto steel are not easily applicable to aluminium and magnesium, whereby a more intense research will be needed. For these reasons, coatings should be specifically developed for the laser pyrolysis on aluminium and subsequently on magnesium substrates within the scope of this project. Therefore it is necessary to vary the composition of the coatings as well as the process parameters systematically and to investigate their influence on the properties of the resulting coating. The next ambitious stage of development concerns the preparation of precursor-based-ceramic coatings by laser pyrolysis on plastic substrates. Until now, none of such activities have been described in the literature. In addition, plastics show an even lower thermal stability, very high CTEs and low thermal conductivity. Moreover, the resulting reduced heat dissipation during the laser pyrolysis can lead to an undesired increase of the substrate temperature. As the expected problems cannot be solved at once, coatings for carbon fiber reinforced plastics shall be developed at first and afterwards for pure plastics. For all coating systems the characterization of the most important mechanical and physical properties as well as the chemical resistance will be performed. Therefore, fundamental knowledge should be obtained, to enable a systematic development of ceramic coatings for different substrates, based on the coating composition and the process parameters to be determined.