This work investigates the conversion of molecular precursors to very thin ceramic coatings by irradiation cure. The goal is to target specific bonds in the precursor structure by adjusting the wavelength of the radiation thereby achieving localized heating. The proposed method is an alternative route to conventional polymer-to-ceramic conversion and allows for new applications including those featuring polymeric substrates (e.g. wind turbine blades), since the underlying substrate is not exposed to very high temperatures.

For this purpose, the light absorption of selected precursors including a polysilazane and a polycarbosilane as well as a number of polysiloxanes was studied in the range of lambda = 0.2 - 25 microm. The absorption band at lambda = 4.8 microm associated with the silane (Si-H) functional group was identified as a promising wavelength for radiation cure experiments. The Si-H bond is present in some of the precursors investigated in this work, but is not included in the structure of the ceramic product or the substrate composite and therefore could allow for self-limiting heating in the precursor during the conversion process. The results of radiation cure experiments of a polycarbosilane with a Si-H content of 38.6 mmol/g are presented. The primary characterization technique applied in this work was FTIR. Furthermore, the molar absorptivity values associated with the Si-H bonds found in the pre-ceramic polymers studied are also reported.